5.3 turbo keep stock 5.3 heads or use my ported ls6?
08-02-2011, 02:11 PM
#21
the same principles apply above. backpressure was obviously a massive issue on that engine. TURBOS DO NOT MULTIPLY THINGS. i have no idea where you're getting this information, but you're wrong. there is no x4, x2, +6, -2, /5 with selecting turbocharged engine components.
HTH
08-02-2011, 06:45 PM
#22
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again, what exactly is the turbocharger multiplying? if you mean MAGNIFY, then yes, a poor induction setup will be magnified once you get a certain point, and will result in huge losses.
but in this case, he's not going to gain much from the ported heads because the stock cylinder head wont be a restriction AT ALL. not only that, but swapping the heads is going to cost him compression.
and density ratio refers to the the density of the air pre compressor VS the density of the air post compressor. how does this apply to my last paragraph?
but in this case, he's not going to gain much from the ported heads because the stock cylinder head wont be a restriction AT ALL. not only that, but swapping the heads is going to cost him compression.
and density ratio refers to the the density of the air pre compressor VS the density of the air post compressor. how does this apply to my last paragraph?
Last edited by kmracer; 08-02-2011 at 06:58 PM.
08-02-2011, 10:48 PM
#23
Basic rule of thumb that engine builders say is basically unexcapable: it takes 1.5 cfm of air per HP...... if you want 1000hp then you are going to need 1500cfm, if you want 500hp you are going to need 750 cfm of airflow thru the motor. Keep this is mind when reading below.....
I dont want to type a response that takes an hour to type up. I type with 2 fingers, my spelling sucks, and my 12 year old sons grammar is better than mine...
OK old school Turbo 101 ( the basics) and calculating what would be the best turbo for a particular motor. The VERY first thing you do is calculate the estimated air flow thru the motor naturally aspirated. With this you get into engine size (cubic inches), expected rpm range, and VE (volumetric efficiency). If you are familiar with FAST, Bigstuff, accell DFI these along with desired A/F ratios are the heavy hitters for calculating how long to spray a given size injector for on a NA motor. The VE numbers are what a tuner fills in on your fueling tables. The better a motor breaths at a given rpm the higher the VE. Basically a 100 cubic inch four stroke motor will pump 100 cubic inches of air thru it for every 2 revolutions if its VE is 100%. Now if that motor only pumped 50 cubic inches of air thru it then its VE would be 50%, it only pumped half as much as it should have. So if you only pumped half as much air then you can only burn half as much fuel and you will basically make half as much HP. This difference between how much air the motor should have pumped thru it and how much it actually pumped threw it is where alot of street car upgrades try to grab some HP. Like air filters, exhaust ect. Good lord I am getting a headache already...
So the other things we can do to flow more air thru a motor is to make the motor bigger (bore and or stroke it), increase the speed the motor turns. When you increase the number of times a motor turns in a minute (rpms) you have the potential to increase how much air flowed thru it in that minute. Cams are the heavy hitters here and right behind is the heads and intake and exhaust systems. All these will have a huge effect on the over all VE thru out the rpm range but will tend to shine the most as rpms increase.
So 35 mins of typing and 5 mins of reading later WTH was I discussing all these things? Because the first thing you do when selecting a proper turbo for a motor is you HAVE to know approx how much air it would flow if it was naturally aspirated. The pisser of writing something like this is that its kind of in vane with a popular motor to mod like the LS motors. A basic search of what kind of power for what normal mods will give us a good idea on the expected NA hp. Like a 6.0L with this cam and those heads and these other mods will give you 450 hp.... Hey!! 450 hp is basically 675 cfm, screw the math and the theory my motors has the exact same mods or real damn close. I should be flowing right around that 675 cfm so lets move on.
The turbo side can open up lots of really interesting discussions. But lets stick to the heavy hitter on the turbo side. DENSITY RATIO, the best way i can describe this is its the ratio between how much air is in something compared to how much air would be in it at standard temperature and pressure. I believe standard temp and pressure is 60 degrees F, and 14.7 pounds per square in absolute (basic barometric pressure at sea level).
For easy math we are going to call standard pressure 15psia. Now with density ratio think of an air compressor tank where the air in it has cooled back down to 60 degrees F for all scenarios. If the air tank was opened up and vented it would only have atmospheric pressure in it which is 15 pounds but our gauge would read zero because 99.xx% of the compressor gauges out there call atmospheric pressure 0. This is why you see something like 30psig the psig stands for pounds per square inch gauge pressure and you have to add the 15 pounds of atmospheric pressure to that to get the absolute pressure (psia). Ok all our readings are assuming the air in the tank has settled out to 60 degrees. We close the valve and bring the pressure up to 15 pounds on our gauge. Now we have 15 psig + 15psia for 30psi total, you then divide that by the 15 psia, so 30 / 15 = 2 we now have a density ratio of 2 in the tank. if we took the tank up to 30 psig we would have 30 psig + the 15 psia for 45 psi total. Take that 45 and divide by that 15psia again and we have 45 / 15 = 3 we now have a density ratio of 3 in the tank. For every 15 psig we go up we increase the density ratio by 1 if we kept the temp of the air at that 60 degrees. So when we have a density ratio of 2 then we have 2 times as much air in that tank as what would be in there naturally if we just had it opened up. 3 would be 3 times 4 would be 4 times.
Any forced induction set up increases the density ratio of the air going into the motor once the motor goes into boost. And what is DENSITY RATIO? It is a MULTIPLIER 2x 3x 4x (it doesnt have to be a whole number it can be any number or fraction there of 1.2 , 1.8 , 3.7 , 2.0045
.....) The density ratio just comes down to what pressure the air is at, and what temp it is at. Once we know these two things we can calculate the density ratio. Once we know are density ratio this is our multiplier. So if we have a density ratio of 2.2 we would then take our 675cfm (450) NA and multiply it by 2.2, 675 x 2.2 = 1485 cfm. Holly crap if 1.5cfm = 1 hp then 1485 / 1.5 = 990 hp damn close to 1000hp. So a density ratio of 2.2 took a 450 hp motor to 990hp. NOW ALL THIS TIES INTO MY ORIGINAL POST..... If the motor was at 350 hp to start instead of 450, which is only 100 hp difference. If we then took this 350 hp motor and and ran the same pressure and temp in the intake manifold we would have the same 2.2 density ratio. We would then take the 350hp and MULTIPLY it by 2.2 which gives us 770hp. So a lack of upgrades that cost us 100 hp naturally aspirated wound up costing us 220 hp when we where boosted and running at a density ratio of 2.2.
As you address flow or "Breathing" issues on a motor the gains from addressing these issues goes up once the motor is boosted. You will lay down bigger numbers over all, bigger numbers per pound of boost, or be able to run less boost to hit a HP target if you make the motor breath better. The wilder you get with the turbos and intercooling the wilder these gains will be. I have spent close to two hours typing this and I am done with trying to explain this. Half the reason it takes so long is trying to word it to where I think peeps will be able to understand it. IF I lost you somewhere in the explanation all I can say is I tried hard to explain it the best I could. If you do some heavy research on turbocharging the concepts above will be verified. One thing you will see that will look different is that lb/min of air flow has replaced the cfm approach. They are just looking and measuring from a mass of air stand point instead of volume of air standpoint. 10lb/min = approx 100hp = approx 150 cfm.
HTH
I dont want to type a response that takes an hour to type up. I type with 2 fingers, my spelling sucks, and my 12 year old sons grammar is better than mine...
OK old school Turbo 101 ( the basics) and calculating what would be the best turbo for a particular motor. The VERY first thing you do is calculate the estimated air flow thru the motor naturally aspirated. With this you get into engine size (cubic inches), expected rpm range, and VE (volumetric efficiency). If you are familiar with FAST, Bigstuff, accell DFI these along with desired A/F ratios are the heavy hitters for calculating how long to spray a given size injector for on a NA motor. The VE numbers are what a tuner fills in on your fueling tables. The better a motor breaths at a given rpm the higher the VE. Basically a 100 cubic inch four stroke motor will pump 100 cubic inches of air thru it for every 2 revolutions if its VE is 100%. Now if that motor only pumped 50 cubic inches of air thru it then its VE would be 50%, it only pumped half as much as it should have. So if you only pumped half as much air then you can only burn half as much fuel and you will basically make half as much HP. This difference between how much air the motor should have pumped thru it and how much it actually pumped threw it is where alot of street car upgrades try to grab some HP. Like air filters, exhaust ect. Good lord I am getting a headache already...
So the other things we can do to flow more air thru a motor is to make the motor bigger (bore and or stroke it), increase the speed the motor turns. When you increase the number of times a motor turns in a minute (rpms) you have the potential to increase how much air flowed thru it in that minute. Cams are the heavy hitters here and right behind is the heads and intake and exhaust systems. All these will have a huge effect on the over all VE thru out the rpm range but will tend to shine the most as rpms increase.
So 35 mins of typing and 5 mins of reading later WTH was I discussing all these things? Because the first thing you do when selecting a proper turbo for a motor is you HAVE to know approx how much air it would flow if it was naturally aspirated. The pisser of writing something like this is that its kind of in vane with a popular motor to mod like the LS motors. A basic search of what kind of power for what normal mods will give us a good idea on the expected NA hp. Like a 6.0L with this cam and those heads and these other mods will give you 450 hp.... Hey!! 450 hp is basically 675 cfm, screw the math and the theory my motors has the exact same mods or real damn close. I should be flowing right around that 675 cfm so lets move on.
The turbo side can open up lots of really interesting discussions. But lets stick to the heavy hitter on the turbo side. DENSITY RATIO, the best way i can describe this is its the ratio between how much air is in something compared to how much air would be in it at standard temperature and pressure. I believe standard temp and pressure is 60 degrees F, and 14.7 pounds per square in absolute (basic barometric pressure at sea level).
For easy math we are going to call standard pressure 15psia. Now with density ratio think of an air compressor tank where the air in it has cooled back down to 60 degrees F for all scenarios. If the air tank was opened up and vented it would only have atmospheric pressure in it which is 15 pounds but our gauge would read zero because 99.xx% of the compressor gauges out there call atmospheric pressure 0. This is why you see something like 30psig the psig stands for pounds per square inch gauge pressure and you have to add the 15 pounds of atmospheric pressure to that to get the absolute pressure (psia). Ok all our readings are assuming the air in the tank has settled out to 60 degrees. We close the valve and bring the pressure up to 15 pounds on our gauge. Now we have 15 psig + 15psia for 30psi total, you then divide that by the 15 psia, so 30 / 15 = 2 we now have a density ratio of 2 in the tank. if we took the tank up to 30 psig we would have 30 psig + the 15 psia for 45 psi total. Take that 45 and divide by that 15psia again and we have 45 / 15 = 3 we now have a density ratio of 3 in the tank. For every 15 psig we go up we increase the density ratio by 1 if we kept the temp of the air at that 60 degrees. So when we have a density ratio of 2 then we have 2 times as much air in that tank as what would be in there naturally if we just had it opened up. 3 would be 3 times 4 would be 4 times.
Any forced induction set up increases the density ratio of the air going into the motor once the motor goes into boost. And what is DENSITY RATIO? It is a MULTIPLIER 2x 3x 4x (it doesnt have to be a whole number it can be any number or fraction there of 1.2 , 1.8 , 3.7 , 2.0045
.....) The density ratio just comes down to what pressure the air is at, and what temp it is at. Once we know these two things we can calculate the density ratio. Once we know are density ratio this is our multiplier. So if we have a density ratio of 2.2 we would then take our 675cfm (450) NA and multiply it by 2.2, 675 x 2.2 = 1485 cfm. Holly crap if 1.5cfm = 1 hp then 1485 / 1.5 = 990 hp damn close to 1000hp. So a density ratio of 2.2 took a 450 hp motor to 990hp. NOW ALL THIS TIES INTO MY ORIGINAL POST..... If the motor was at 350 hp to start instead of 450, which is only 100 hp difference. If we then took this 350 hp motor and and ran the same pressure and temp in the intake manifold we would have the same 2.2 density ratio. We would then take the 350hp and MULTIPLY it by 2.2 which gives us 770hp. So a lack of upgrades that cost us 100 hp naturally aspirated wound up costing us 220 hp when we where boosted and running at a density ratio of 2.2. As you address flow or "Breathing" issues on a motor the gains from addressing these issues goes up once the motor is boosted. You will lay down bigger numbers over all, bigger numbers per pound of boost, or be able to run less boost to hit a HP target if you make the motor breath better. The wilder you get with the turbos and intercooling the wilder these gains will be. I have spent close to two hours typing this and I am done with trying to explain this. Half the reason it takes so long is trying to word it to where I think peeps will be able to understand it. IF I lost you somewhere in the explanation all I can say is I tried hard to explain it the best I could. If you do some heavy research on turbocharging the concepts above will be verified. One thing you will see that will look different is that lb/min of air flow has replaced the cfm approach. They are just looking and measuring from a mass of air stand point instead of volume of air standpoint. 10lb/min = approx 100hp = approx 150 cfm.
HTH
08-03-2011, 03:45 AM
#24
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"So a lack of upgrades that cost us 100 hp naturally aspirated wound up costing us 220 hp when we where boosted and running at a density ratio of 2.2."
you're forgetting back pressure (drive pressure.). im not sure if you're used to a supercharged engine, but consider this. in an efficient, modern setup pressure ratio (absolute turbine pressure:absolute intake pressure) can be 1:1. meaning the pressure in the intake manifold is = to the back pressure pre-turbine, meaning the engine is going to behave the same as it would N/A. if im wrong, let me know. in any case, the heads arent going to be holding him back AT ALL at 600whp, and he'd be better off with the half point of compression and the $800 or so he'd get from selling em.
"density ratio refers to the the density of the air pre compressor VS the density of the air post compressor. "
i hope you didnt spend 2 hours typing that just for me, i understand it completely.
and please understand im not trying to demean or belittle you, i just completely disagree.
you're forgetting back pressure (drive pressure.). im not sure if you're used to a supercharged engine, but consider this. in an efficient, modern setup pressure ratio (absolute turbine pressure:absolute intake pressure) can be 1:1. meaning the pressure in the intake manifold is = to the back pressure pre-turbine, meaning the engine is going to behave the same as it would N/A. if im wrong, let me know. in any case, the heads arent going to be holding him back AT ALL at 600whp, and he'd be better off with the half point of compression and the $800 or so he'd get from selling em.
"density ratio refers to the the density of the air pre compressor VS the density of the air post compressor. "
i hope you didnt spend 2 hours typing that just for me, i understand it completely.
and please understand im not trying to demean or belittle you, i just completely disagree.
Last edited by kmracer; 08-03-2011 at 04:02 AM.
08-03-2011, 05:38 AM
#25
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Wow I just lost 2 hours of sleep do to reading this thread but I can go to sleep knowing when I re-read it tomorrow I'm sure a lot of us will come away with a better understanding of how we should've paid more attention in math class! Seriously this is a great read and learning tool no matter how you look at it. Thanks
08-03-2011, 10:57 AM
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So 1.5 cfm = 1hp, wut kinda hp difference would there be between identicle setups one with 8:1 cr and the other with 9:1 cr
i know everyone says that more compression is better for out.of boost regions but wut about in boost, i would think cfm flow would be more important than a small compression ratio difference...
But i would look at other factors as well, if ur running a stock intake manifold and it only flows 300cfm n/a then heads that flow substantially more than that are pretty much useless
i know everyone says that more compression is better for out.of boost regions but wut about in boost, i would think cfm flow would be more important than a small compression ratio difference...
But i would look at other factors as well, if ur running a stock intake manifold and it only flows 300cfm n/a then heads that flow substantially more than that are pretty much useless
08-03-2011, 03:14 PM
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with less compression you'll have to run more boost to compensate, and you'll spool slower. now the difference between 1 compression point and how much boost more boost you'd have to run to make up for the power loss i have no idea. probably a half to a full psi.
like i said, in this case there is no need to swap heads. camaroandreas made 1340hp with stock 317 heads, no porting, and valve job. were they holding him back? perhaps. but the dyno doesnt show it, the engine keeps pulling past 7k rpm's....
https://ls1tech.com/forums/forced-in...k-6-0-lit.html
not nut swinging, but sometimes **** just WORKS. beyond the calculations...
like i said, in this case there is no need to swap heads. camaroandreas made 1340hp with stock 317 heads, no porting, and valve job. were they holding him back? perhaps. but the dyno doesnt show it, the engine keeps pulling past 7k rpm's....
https://ls1tech.com/forums/forced-in...k-6-0-lit.html
not nut swinging, but sometimes **** just WORKS. beyond the calculations...
08-03-2011, 07:55 PM
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ya well im trying to deside for myself if i should run the stock 5.3 heads or my slightly ported 317's.....and i was also thinking that the larger cc head would help spool the turbo faster because it's allowing you to have a larger volume in the cylinder which will in turn increase the amount of air into the cylinder and have more exhaust gas to spool the turbine wheel...
compression is not gonna spool your turbo, it will just give you a little more torque while out of boost,
compression is not gonna spool your turbo, it will just give you a little more torque while out of boost,
08-03-2011, 08:01 PM
#29
Technically if the motors are at the same RPM, the one with lower compression will spool a little faster, since the exhaust will be a little hotter (since its less efficient, and turbos work off of heat). However, more N/A torque helps you get up on the converter easier (more rpm against the converter means more airflow, and faster spool).
08-03-2011, 08:24 PM
#31
It has everything to do with it. Its why the LS motors make so much power. All LS heads flow real nice compared to old SBC heads, and any of them can hit 600hp with a turbo easy. The question is how much boost and what rpm you will need to run to hit the 600 hp. The better the head the less boost you will need to run to hit that 600hp.
The 120hp is from a scenario to explain a principle. If you are only aiming for 600hp with a turbo your not going to find a head that bumps you from 480 to 600, your set up is just going to be to mild. However if you take a 2000hp turbocharged LSX motor with high end heads and swap them out for stockers then that motor will loose ALOT more than 120hp.
The best way to sum up the principal is that turbos are multipliers. Because of this the gains from making the motor breath better are actually larger than on NA motors. There is a false concept that "You're forcing the air into the motor so it doesnt matter as much". This is wrong and the fact that the turbo acts like a multiplier makes addressing these issues even more worth while. BUT if you are limiting yourself to 600hp there isnt much of anything I would worry about spending money on, but you have a better set of heads just sitting there already.
I am new to LS stuff and I have been researching up like crazy. In my online researching I cam across an article a couple years old. I think it was a hot rod article. In this article they had some nasty twin turbo LS build. This was NOT that newer 4.8 @ 1200hp article. I cant remember all the details but it was some twin turbo LS they had on a dyno and they where at 1200 hp or so. They felt like something was holding them back and they wound up unhooking the dyno exhaust. The motor immediately jumped to 1500hp!! That was a 300hp gain from changing the exhaust. They even stated that they where surprised because the dyno had a freakin 5" exhaust system on it, and they thought it was more than enough. If you are wondering HTH a motor can gain 300hp from an exhaust mod then read up in my original post about making the motor breath better and turbos multiplying the gains from these types of mods.
HTH
The 120hp is from a scenario to explain a principle. If you are only aiming for 600hp with a turbo your not going to find a head that bumps you from 480 to 600, your set up is just going to be to mild. However if you take a 2000hp turbocharged LSX motor with high end heads and swap them out for stockers then that motor will loose ALOT more than 120hp.
The best way to sum up the principal is that turbos are multipliers. Because of this the gains from making the motor breath better are actually larger than on NA motors. There is a false concept that "You're forcing the air into the motor so it doesnt matter as much". This is wrong and the fact that the turbo acts like a multiplier makes addressing these issues even more worth while. BUT if you are limiting yourself to 600hp there isnt much of anything I would worry about spending money on, but you have a better set of heads just sitting there already.
I am new to LS stuff and I have been researching up like crazy. In my online researching I cam across an article a couple years old. I think it was a hot rod article. In this article they had some nasty twin turbo LS build. This was NOT that newer 4.8 @ 1200hp article. I cant remember all the details but it was some twin turbo LS they had on a dyno and they where at 1200 hp or so. They felt like something was holding them back and they wound up unhooking the dyno exhaust. The motor immediately jumped to 1500hp!! That was a 300hp gain from changing the exhaust. They even stated that they where surprised because the dyno had a freakin 5" exhaust system on it, and they thought it was more than enough. If you are wondering HTH a motor can gain 300hp from an exhaust mod then read up in my original post about making the motor breath better and turbos multiplying the gains from these types of mods.
HTH
08-03-2011, 09:31 PM
#33
I would think since he will be on a stock shortblock the larger chambers not only will benefit in CFM flow, but also by lessening his chance of detonation....and since he will theoretically have to run more boost due to the compression drop won't that make more power in boost due to more psi, and having more cfm flow?
One thing we haven't even asked that is the big X factor here is what size this turbo will be? If it is anything like a TC76 or say even an ST-80 he will not have back pressure issues with either of those until he gets to around 364 c.i. and/or 15+ psi.
I honestly think with the cast pistons and rods being used that the larger chambers will give you more room to err on being at a lower CR and benefit in boost by having more cross sectional area.
I've also heard this being thrown around before that you can run a larger cross sectional area intake port wise on a boosted motor and get away with it without taking a hit at lower and mid range rpms vs. a N/A motor because the air is being pressurized into the port. Maybe this is wrong?
One thing we haven't even asked that is the big X factor here is what size this turbo will be? If it is anything like a TC76 or say even an ST-80 he will not have back pressure issues with either of those until he gets to around 364 c.i. and/or 15+ psi.
I honestly think with the cast pistons and rods being used that the larger chambers will give you more room to err on being at a lower CR and benefit in boost by having more cross sectional area.
I've also heard this being thrown around before that you can run a larger cross sectional area intake port wise on a boosted motor and get away with it without taking a hit at lower and mid range rpms vs. a N/A motor because the air is being pressurized into the port. Maybe this is wrong?
08-04-2011, 07:01 AM
#34
Pretty simple really if you make more N/A power you will make more power at the same boost level. NA power x pressure ratio is a rough idea.
Say 10lbs of boost, 10 + 14.7 = 24.7
24.7 / 14.7 = 1.68 pressure ratio.
400 hp engine x 1.68 pr = 672 hp in theory with out accounting for losses in efficiency
350 hp engine x 1.68 pr = 588 hp
To say head flow has no effect on hp is down right retarded. Do you want to make 600 hp on 10 lbs or 12lbs. Less boost = less heat = more efficient. Compressing air creates heat, to much heat creates detonation given a certain fuel.
Say 10lbs of boost, 10 + 14.7 = 24.7
24.7 / 14.7 = 1.68 pressure ratio.
400 hp engine x 1.68 pr = 672 hp in theory with out accounting for losses in efficiency
350 hp engine x 1.68 pr = 588 hp
To say head flow has no effect on hp is down right retarded. Do you want to make 600 hp on 10 lbs or 12lbs. Less boost = less heat = more efficient. Compressing air creates heat, to much heat creates detonation given a certain fuel.
08-05-2011, 09:46 PM
#35
I took a two day break so now i am behind.
When you look at the arguments I am making these are more on how to properly select a turbo charger for a particular motor / application. I was using some backwards math, like A is greater then B and B is greater than C, therefore C is greater than A.
Now if you are studious and do your homework and go thru the calcs to pick your own turbo you will find that the airflow thru the motor Natuarally aspirated is what all the rest of the calculations are based on. If you actually do the calculations, and if you have a solid understanding of mathematics, then the points or concepts I was talking about in previous posts will become more clear. The better the engine breathes NA carries into the calcs for once the turbo is added, and the gains go up and up in the calcs as you add boost.
Now I am not trying to be a smart ***, Im just trying to pass along some info. Alot of people dont want to research the hell out of things or they dont want to do the math or what ever. I am cool with that, but when I make a post like this I try to describe the (science, math, logic, physics ect) behind it as best as I can and in such a way that someone who isnt all read up on it may be able to understand it. BTW I am WAY better at explaining this stuff verbally. I have a decent size group of car buddies in real life and I am always trying to explain things to them. I am always explaining this stuff, not because I like to hear myself talk, but because all these guys are always asking me about things like this. BTW we tend to drink when we get together and I have a few good booze related analogies for some of this stuff. Why the hell its easier for guys drinking beer to understand science stuff if you put it in terms of booze will always confuse me, but if it works it works.
So back to the real subject of the heads, and then add in back pressure, add in compression. The above stuff like a 60 hp gain from heads on a NA motor might be 120 hp on a boosted motor. This is 100% solid, dont get side tracked off of that. This will tie into How well your turbo set up is designed, and how much boost you are running.If you are running 5 pis boost you might only see 75 extra hp boosted instead of 60, if you are running 45 psi you may see a couple hundred extra hp EASY out of kick *** heads.....
HERE IS ONE CATCH: this is all based on how to properly pick a turbo, this would assume you did / do have the right turbo and associated components selected, and therefore the calculated / theoretical gains or something close to them should be with in reach. If you have a turbo that is struggling to feed a motor already, or close to struggling then switching to higher flow heads is not going to get you near the gain it should. It always comes down to having a matching combo, wether NA or boosted, street or track, dragster, mud booger or tow vehicle. Selecting all the pieces of the puzzle to work well with, and even complement each other should be priority 1 in the project.
CATCH NUMBER 2: diminishing returns. This one is always bitting you in the *** when seeking better performance. You see this alot in cams, if you add 20 degrees to a cam and pick up 60 hp, it doesnt mean that 60 more hp is just another 20 degrees away. There are side effects / limitations to all this stuff and as you get wilder with your selection the bigger the bite Diminishing returns takes out of your pie.
SOME VALIDATION:
http://www.performancetrucks.net/for...-going-485734/
This is that 1200hp almost stock 4.8 twin turbo. If you remember the Density ratio stuff from above that is based on manifold pressure AND temperature. If you get the air going into the motor back down to 60 degrees you can basically look at just the pressure or boost to determine your HP gain. BTW getting the compressed air back down to 60 degrees or even lower is pretty much the sole territory of liquid intercooler guys. Thats why I have 4 of them in my garage and these are all from WAY before you could buy cheap liquids off of EBAY. One of them almost cost me $2000!! So if we get the air down to 60 degrees then we can treat the boost like its or density ratio. The motor in this article made 450 hp naturally aspirated. If you look at the boost only and treat the boost like it the actual density ratio, and give them the benefit of the doubt that their intercooler set up was working real good........ that motor would calc out to hit right about 1273 hp @ the 26.8 psi. They hit 1203hp so diminishing returns gigged them for about 70 hp on a 1200 hp motor, that isnt bad in my book. The calculated HP in crease would be 2.83 x the NA hp. the measured gain was 2.67 x the NA hp and this math is based on giving them the benefit of the doubt on the intercooling.
If you ask me HOW THE HELL DID they hit 1200 hp on that, I would say the answer is simple they made 451 hp on the damn thing naturally aspirated, and they got it to stay together under almost 27 psi of boost. The 1200hp was going to be elementary in that scenario.
Now if I get to ask my question it would be this: HOW THE HELL DID they make 451 hp naturally aspirated on that little 4.8 at only 7000 rpm... I'll take a dozen please
Compression: In the turbo Buick world guys used to drive over their crankshafts trying to get into the 10's. They now have guys knocking on or in the 8's with the production 109 blocks. They are going faster than ever and are actually breaking less stuff doing it. What they have been fighting for years is detonation. Do not underestimate this detonation straight up destroys stuff, pistons, cranks rods ect. I dont care if you have a 500 hp turbo motor, if you are detonating you will break any of the above EASY. IF you dont detonate you will be shocked at how much HP and boost some stock stuff can take. Finding out how much hp stock stuff can really take tends to be slow coming. Most peeps wont put a $2400 Fast system in thier
"Budget" builds so they can tune it down to the nats ***. They would get a $100 reflash and spend $2300 on goodies like pistons and rods, OR they would think about the nice rods and pistons they could buy if they had $2300. With the compression I would rather error a little low than high. Unless you are running a maxed out set up you can always up the boost a bit and you are less likely to break something in the short block because extra compression with boost is more likely to get you into detonation than adding a little boost to a lower compression motor. ESPECIALLY on a street car.
HTH
When you look at the arguments I am making these are more on how to properly select a turbo charger for a particular motor / application. I was using some backwards math, like A is greater then B and B is greater than C, therefore C is greater than A.
Now if you are studious and do your homework and go thru the calcs to pick your own turbo you will find that the airflow thru the motor Natuarally aspirated is what all the rest of the calculations are based on. If you actually do the calculations, and if you have a solid understanding of mathematics, then the points or concepts I was talking about in previous posts will become more clear. The better the engine breathes NA carries into the calcs for once the turbo is added, and the gains go up and up in the calcs as you add boost.
Now I am not trying to be a smart ***, Im just trying to pass along some info. Alot of people dont want to research the hell out of things or they dont want to do the math or what ever. I am cool with that, but when I make a post like this I try to describe the (science, math, logic, physics ect) behind it as best as I can and in such a way that someone who isnt all read up on it may be able to understand it. BTW I am WAY better at explaining this stuff verbally. I have a decent size group of car buddies in real life and I am always trying to explain things to them. I am always explaining this stuff, not because I like to hear myself talk, but because all these guys are always asking me about things like this. BTW we tend to drink when we get together and I have a few good booze related analogies for some of this stuff. Why the hell its easier for guys drinking beer to understand science stuff if you put it in terms of booze will always confuse me, but if it works it works.
So back to the real subject of the heads, and then add in back pressure, add in compression. The above stuff like a 60 hp gain from heads on a NA motor might be 120 hp on a boosted motor. This is 100% solid, dont get side tracked off of that. This will tie into How well your turbo set up is designed, and how much boost you are running.If you are running 5 pis boost you might only see 75 extra hp boosted instead of 60, if you are running 45 psi you may see a couple hundred extra hp EASY out of kick *** heads.....
HERE IS ONE CATCH: this is all based on how to properly pick a turbo, this would assume you did / do have the right turbo and associated components selected, and therefore the calculated / theoretical gains or something close to them should be with in reach. If you have a turbo that is struggling to feed a motor already, or close to struggling then switching to higher flow heads is not going to get you near the gain it should. It always comes down to having a matching combo, wether NA or boosted, street or track, dragster, mud booger or tow vehicle. Selecting all the pieces of the puzzle to work well with, and even complement each other should be priority 1 in the project.
CATCH NUMBER 2: diminishing returns. This one is always bitting you in the *** when seeking better performance. You see this alot in cams, if you add 20 degrees to a cam and pick up 60 hp, it doesnt mean that 60 more hp is just another 20 degrees away. There are side effects / limitations to all this stuff and as you get wilder with your selection the bigger the bite Diminishing returns takes out of your pie.
SOME VALIDATION:
http://www.performancetrucks.net/for...-going-485734/
This is that 1200hp almost stock 4.8 twin turbo. If you remember the Density ratio stuff from above that is based on manifold pressure AND temperature. If you get the air going into the motor back down to 60 degrees you can basically look at just the pressure or boost to determine your HP gain. BTW getting the compressed air back down to 60 degrees or even lower is pretty much the sole territory of liquid intercooler guys. Thats why I have 4 of them in my garage and these are all from WAY before you could buy cheap liquids off of EBAY. One of them almost cost me $2000!! So if we get the air down to 60 degrees then we can treat the boost like its or density ratio. The motor in this article made 450 hp naturally aspirated. If you look at the boost only and treat the boost like it the actual density ratio, and give them the benefit of the doubt that their intercooler set up was working real good........ that motor would calc out to hit right about 1273 hp @ the 26.8 psi. They hit 1203hp so diminishing returns gigged them for about 70 hp on a 1200 hp motor, that isnt bad in my book. The calculated HP in crease would be 2.83 x the NA hp. the measured gain was 2.67 x the NA hp and this math is based on giving them the benefit of the doubt on the intercooling.
If you ask me HOW THE HELL DID they hit 1200 hp on that, I would say the answer is simple they made 451 hp on the damn thing naturally aspirated, and they got it to stay together under almost 27 psi of boost. The 1200hp was going to be elementary in that scenario.
Now if I get to ask my question it would be this: HOW THE HELL DID they make 451 hp naturally aspirated on that little 4.8 at only 7000 rpm... I'll take a dozen please
Compression: In the turbo Buick world guys used to drive over their crankshafts trying to get into the 10's. They now have guys knocking on or in the 8's with the production 109 blocks. They are going faster than ever and are actually breaking less stuff doing it. What they have been fighting for years is detonation. Do not underestimate this detonation straight up destroys stuff, pistons, cranks rods ect. I dont care if you have a 500 hp turbo motor, if you are detonating you will break any of the above EASY. IF you dont detonate you will be shocked at how much HP and boost some stock stuff can take. Finding out how much hp stock stuff can really take tends to be slow coming. Most peeps wont put a $2400 Fast system in thier
"Budget" builds so they can tune it down to the nats ***. They would get a $100 reflash and spend $2300 on goodies like pistons and rods, OR they would think about the nice rods and pistons they could buy if they had $2300. With the compression I would rather error a little low than high. Unless you are running a maxed out set up you can always up the boost a bit and you are less likely to break something in the short block because extra compression with boost is more likely to get you into detonation than adding a little boost to a lower compression motor. ESPECIALLY on a street car.
HTH
08-06-2011, 02:20 AM
#36
I took a two day break so now i am behind.
When you look at the arguments I am making these are more on how to properly select a turbo charger for a particular motor / application. I was using some backwards math, like A is greater then B and B is greater than C, therefore C is greater than A.
Now if you are studious and do your homework and go thru the calcs to pick your own turbo you will find that the airflow thru the motor Natuarally aspirated is what all the rest of the calculations are based on. If you actually do the calculations, and if you have a solid understanding of mathematics, then the points or concepts I was talking about in previous posts will become more clear. The better the engine breathes NA carries into the calcs for once the turbo is added, and the gains go up and up in the calcs as you add boost.
Now I am not trying to be a smart ***, Im just trying to pass along some info. Alot of people dont want to research the hell out of things or they dont want to do the math or what ever. I am cool with that, but when I make a post like this I try to describe the (science, math, logic, physics ect) behind it as best as I can and in such a way that someone who isnt all read up on it may be able to understand it. BTW I am WAY better at explaining this stuff verbally. I have a decent size group of car buddies in real life and I am always trying to explain things to them. I am always explaining this stuff, not because I like to hear myself talk, but because all these guys are always asking me about things like this. BTW we tend to drink when we get together and I have a few good booze related analogies for some of this stuff. Why the hell its easier for guys drinking beer to understand science stuff if you put it in terms of booze will always confuse me, but if it works it works.
So back to the real subject of the heads, and then add in back pressure, add in compression. The above stuff like a 60 hp gain from heads on a NA motor might be 120 hp on a boosted motor. This is 100% solid, dont get side tracked off of that. This will tie into How well your turbo set up is designed, and how much boost you are running.If you are running 5 pis boost you might only see 75 extra hp boosted instead of 60, if you are running 45 psi you may see a couple hundred extra hp EASY out of kick *** heads.....
HERE IS ONE CATCH: this is all based on how to properly pick a turbo, this would assume you did / do have the right turbo and associated components selected, and therefore the calculated / theoretical gains or something close to them should be with in reach. If you have a turbo that is struggling to feed a motor already, or close to struggling then switching to higher flow heads is not going to get you near the gain it should. It always comes down to having a matching combo, wether NA or boosted, street or track, dragster, mud booger or tow vehicle. Selecting all the pieces of the puzzle to work well with, and even complement each other should be priority 1 in the project.
CATCH NUMBER 2: diminishing returns. This one is always bitting you in the *** when seeking better performance. You see this alot in cams, if you add 20 degrees to a cam and pick up 60 hp, it doesnt mean that 60 more hp is just another 20 degrees away. There are side effects / limitations to all this stuff and as you get wilder with your selection the bigger the bite Diminishing returns takes out of your pie.
SOME VALIDATION:
http://www.performancetrucks.net/for...-going-485734/
This is that 1200hp almost stock 4.8 twin turbo. If you remember the Density ratio stuff from above that is based on manifold pressure AND temperature. If you get the air going into the motor back down to 60 degrees you can basically look at just the pressure or boost to determine your HP gain. BTW getting the compressed air back down to 60 degrees or even lower is pretty much the sole territory of liquid intercooler guys. Thats why I have 4 of them in my garage and these are all from WAY before you could buy cheap liquids off of EBAY. One of them almost cost me $2000!! So if we get the air down to 60 degrees then we can treat the boost like its or density ratio. The motor in this article made 450 hp naturally aspirated. If you look at the boost only and treat the boost like it the actual density ratio, and give them the benefit of the doubt that their intercooler set up was working real good........ that motor would calc out to hit right about 1273 hp @ the 26.8 psi. They hit 1203hp so diminishing returns gigged them for about 70 hp on a 1200 hp motor, that isnt bad in my book. The calculated HP in crease would be 2.83 x the NA hp. the measured gain was 2.67 x the NA hp and this math is based on giving them the benefit of the doubt on the intercooling.
If you ask me HOW THE HELL DID they hit 1200 hp on that, I would say the answer is simple they made 451 hp on the damn thing naturally aspirated, and they got it to stay together under almost 27 psi of boost. The 1200hp was going to be elementary in that scenario.
Now if I get to ask my question it would be this: HOW THE HELL DID they make 451 hp naturally aspirated on that little 4.8 at only 7000 rpm... I'll take a dozen please
Compression: In the turbo Buick world guys used to drive over their crankshafts trying to get into the 10's. They now have guys knocking on or in the 8's with the production 109 blocks. They are going faster than ever and are actually breaking less stuff doing it. What they have been fighting for years is detonation. Do not underestimate this detonation straight up destroys stuff, pistons, cranks rods ect. I dont care if you have a 500 hp turbo motor, if you are detonating you will break any of the above EASY. IF you dont detonate you will be shocked at how much HP and boost some stock stuff can take. Finding out how much hp stock stuff can really take tends to be slow coming. Most peeps wont put a $2400 Fast system in thier
"Budget" builds so they can tune it down to the nats ***. They would get a $100 reflash and spend $2300 on goodies like pistons and rods, OR they would think about the nice rods and pistons they could buy if they had $2300. With the compression I would rather error a little low than high. Unless you are running a maxed out set up you can always up the boost a bit and you are less likely to break something in the short block because extra compression with boost is more likely to get you into detonation than adding a little boost to a lower compression motor. ESPECIALLY on a street car.
HTH
When you look at the arguments I am making these are more on how to properly select a turbo charger for a particular motor / application. I was using some backwards math, like A is greater then B and B is greater than C, therefore C is greater than A.
Now if you are studious and do your homework and go thru the calcs to pick your own turbo you will find that the airflow thru the motor Natuarally aspirated is what all the rest of the calculations are based on. If you actually do the calculations, and if you have a solid understanding of mathematics, then the points or concepts I was talking about in previous posts will become more clear. The better the engine breathes NA carries into the calcs for once the turbo is added, and the gains go up and up in the calcs as you add boost.
Now I am not trying to be a smart ***, Im just trying to pass along some info. Alot of people dont want to research the hell out of things or they dont want to do the math or what ever. I am cool with that, but when I make a post like this I try to describe the (science, math, logic, physics ect) behind it as best as I can and in such a way that someone who isnt all read up on it may be able to understand it. BTW I am WAY better at explaining this stuff verbally. I have a decent size group of car buddies in real life and I am always trying to explain things to them. I am always explaining this stuff, not because I like to hear myself talk, but because all these guys are always asking me about things like this. BTW we tend to drink when we get together and I have a few good booze related analogies for some of this stuff. Why the hell its easier for guys drinking beer to understand science stuff if you put it in terms of booze will always confuse me, but if it works it works.
So back to the real subject of the heads, and then add in back pressure, add in compression. The above stuff like a 60 hp gain from heads on a NA motor might be 120 hp on a boosted motor. This is 100% solid, dont get side tracked off of that. This will tie into How well your turbo set up is designed, and how much boost you are running.If you are running 5 pis boost you might only see 75 extra hp boosted instead of 60, if you are running 45 psi you may see a couple hundred extra hp EASY out of kick *** heads.....
HERE IS ONE CATCH: this is all based on how to properly pick a turbo, this would assume you did / do have the right turbo and associated components selected, and therefore the calculated / theoretical gains or something close to them should be with in reach. If you have a turbo that is struggling to feed a motor already, or close to struggling then switching to higher flow heads is not going to get you near the gain it should. It always comes down to having a matching combo, wether NA or boosted, street or track, dragster, mud booger or tow vehicle. Selecting all the pieces of the puzzle to work well with, and even complement each other should be priority 1 in the project.
CATCH NUMBER 2: diminishing returns. This one is always bitting you in the *** when seeking better performance. You see this alot in cams, if you add 20 degrees to a cam and pick up 60 hp, it doesnt mean that 60 more hp is just another 20 degrees away. There are side effects / limitations to all this stuff and as you get wilder with your selection the bigger the bite Diminishing returns takes out of your pie.
SOME VALIDATION:
http://www.performancetrucks.net/for...-going-485734/
This is that 1200hp almost stock 4.8 twin turbo. If you remember the Density ratio stuff from above that is based on manifold pressure AND temperature. If you get the air going into the motor back down to 60 degrees you can basically look at just the pressure or boost to determine your HP gain. BTW getting the compressed air back down to 60 degrees or even lower is pretty much the sole territory of liquid intercooler guys. Thats why I have 4 of them in my garage and these are all from WAY before you could buy cheap liquids off of EBAY. One of them almost cost me $2000!! So if we get the air down to 60 degrees then we can treat the boost like its or density ratio. The motor in this article made 450 hp naturally aspirated. If you look at the boost only and treat the boost like it the actual density ratio, and give them the benefit of the doubt that their intercooler set up was working real good........ that motor would calc out to hit right about 1273 hp @ the 26.8 psi. They hit 1203hp so diminishing returns gigged them for about 70 hp on a 1200 hp motor, that isnt bad in my book. The calculated HP in crease would be 2.83 x the NA hp. the measured gain was 2.67 x the NA hp and this math is based on giving them the benefit of the doubt on the intercooling.
If you ask me HOW THE HELL DID they hit 1200 hp on that, I would say the answer is simple they made 451 hp on the damn thing naturally aspirated, and they got it to stay together under almost 27 psi of boost. The 1200hp was going to be elementary in that scenario.
Now if I get to ask my question it would be this: HOW THE HELL DID they make 451 hp naturally aspirated on that little 4.8 at only 7000 rpm... I'll take a dozen please
Compression: In the turbo Buick world guys used to drive over their crankshafts trying to get into the 10's. They now have guys knocking on or in the 8's with the production 109 blocks. They are going faster than ever and are actually breaking less stuff doing it. What they have been fighting for years is detonation. Do not underestimate this detonation straight up destroys stuff, pistons, cranks rods ect. I dont care if you have a 500 hp turbo motor, if you are detonating you will break any of the above EASY. IF you dont detonate you will be shocked at how much HP and boost some stock stuff can take. Finding out how much hp stock stuff can really take tends to be slow coming. Most peeps wont put a $2400 Fast system in thier
"Budget" builds so they can tune it down to the nats ***. They would get a $100 reflash and spend $2300 on goodies like pistons and rods, OR they would think about the nice rods and pistons they could buy if they had $2300. With the compression I would rather error a little low than high. Unless you are running a maxed out set up you can always up the boost a bit and you are less likely to break something in the short block because extra compression with boost is more likely to get you into detonation than adding a little boost to a lower compression motor. ESPECIALLY on a street car.
HTH
I hope you stick around this section for some time. I think you could help explain some of the more complicated mathematical problems that are associated with choosing the right turbo or how much will my motor make threads.
08-06-2011, 09:07 PM
#37
I hope you stick around this section for some time. I think you could help explain some of the more complicated mathematical problems that are associated with choosing the right turbo or how much will my motor make threads.
I went and bought a 4.8 and I am itching so bad to turbo it and drop it in something. Here is the problem, I got a big crew cab dually diesel, a jaguar xk8, a harley low rider and a 87 Buick grand national, then the ole ball an chain has her mini van. The LS motor cant go into my truck, harley, or her minivan. That leaves my Jag and my Buick. I cant put a turbo LS into my Jag w/o cutting it up so thats out. That leaves my Buick and there is alot of history behind this car that I may post about at a later date (has to do with a death of a family member), but as of right now I am not sure I would want to drop an LS motor into this. That leaves one other option... pick up another car AND I know where the perfect one is. I need another car like I need a hole in the head and thats not my ole lady talking thats myself trying to exhibit some self control...... Someone some where should start a "Horse Power Anonymous group" .....
"Hi. My name is Jason and I am a turbo addict"
08-06-2011, 09:12 PM
#38
Good lord I am terrible!!
I just reread my last post about how I cant put it into this car or that car and how I cant really buy another car.....
Did that stop me from buying a 4.8 and also half the crap I need to turbocharge it...... Hell no!! and you guys probably thought I was kidding about the HP anonymous thing.
I just reread my last post about how I cant put it into this car or that car and how I cant really buy another car.....
Did that stop me from buying a 4.8 and also half the crap I need to turbocharge it...... Hell no!! and you guys probably thought I was kidding about the HP anonymous thing.
08-08-2011, 03:35 AM
#40
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again, you can sit here and use math and theory, but that isnt always practical. the example you provided hardly backs up your point, seeing as the made double the power the OP has in mind with "stage 1" (whatever that means) stock heads....