Curious about stroke vs turbo efficiency vs piston velocity vs power band
09-10-2005 | 11:15 AM
#21
Again I will say, the Turbo will only flow XX amount of air. Whether its on a 1.0L or 10.0L. The total output will vary by efficiency. You can easily read this by looking at the compressor map. As for larger engine going faster, again its not because of peak HP. Its simply due to larger area under the curve. The earlier you can light off a 106mm the better the ET. This is the same principle behind why a big turbo Supra has great mph and crappy ET.
Jim, I know what you mean. I will be glad when our turbocharger test stand is done. We can simulate the load of a 1.0L through a 15.0L engine. Hard to convince people of different ways of thinking as well as myself at the beginning, but after working at the turbine test facility here at NASA afterhours you get to see the final results and test data to support it. Once again the statement I made above holds true.
Jose
Jim, I know what you mean. I will be glad when our turbocharger test stand is done. We can simulate the load of a 1.0L through a 15.0L engine. Hard to convince people of different ways of thinking as well as myself at the beginning, but after working at the turbine test facility here at NASA afterhours you get to see the final results and test data to support it. Once again the statement I made above holds true.
Jose
09-10-2005 | 11:16 AM
#22
FormerVendor
Joined: Nov 2001
Posts: 3,065
Likes: 5
From: Houston, Tx.
I think I understand what you are saying and you are probably correct on all that too but I am looking at it in another way. I don't care about making a certain power at a certain engine rpm but rather just total power.
You can operate the turbo in it's sweet spot probably with any size engine although the rpm will change obviously quite a bit depending on this. That same sweet spot will be at different rpms depending on engine size and the cam etc. Obviously running a tiny turbo like a 40mm with a 632 inch engine the turbo will not even make boost at higher rpms but be a restrictor plate.
Way down low where the small turbo can work though it will probably make more peak power on that giant engine but the rpm will just be extremely low. I.E 18 wheeler engine! Again you do not see these guys either running a small engine to get more power out of a turbo combination. They LIVE on efficiency and the larger lower rpm engines are more efficient and make more power out of the same fuel.
Basically peak mass flow and power should increase with a given turbo as you enlarge the engine while the rpm you achieve this at will drop very much the same as NA in some ways.
You can operate the turbo in it's sweet spot probably with any size engine although the rpm will change obviously quite a bit depending on this. That same sweet spot will be at different rpms depending on engine size and the cam etc. Obviously running a tiny turbo like a 40mm with a 632 inch engine the turbo will not even make boost at higher rpms but be a restrictor plate.
Way down low where the small turbo can work though it will probably make more peak power on that giant engine but the rpm will just be extremely low. I.E 18 wheeler engine! Again you do not see these guys either running a small engine to get more power out of a turbo combination. They LIVE on efficiency and the larger lower rpm engines are more efficient and make more power out of the same fuel.
Basically peak mass flow and power should increase with a given turbo as you enlarge the engine while the rpm you achieve this at will drop very much the same as NA in some ways.
Originally Posted by y2khawk
sorta but not quite. More often than not, you'll get more compressor flow at a higher pressure ratio. Either limited by choking the compressor, or being so far off the map that you end up in an efficiency range so unusable you will net limited gains.
in the simplest terms, you are limiting the possible mass flow into the air pump (ie engine) with the compressor size. That max limit will vary depending on where you operate on the map of the turbo, ie ideal mass flow for said air pump given a pressure ratio you intend to operate.
reguardless of how much flow you can actualy get from a given turbo, you're ultimately limited but how much heat you've added to the air. You will have to spark and fuel for that heat. Higher pressure ratios = more heat obviously, but extremely low efficiency at a low PR can give you more actually heating than a more efficient compressor at a higher PR.
There are MANY ways to look at it, and that's just on the "cold air" side of things. Turbine size and efficiency one the hot side can choke your air pump as well.
We could spend days on what effects various things will have on what's needed for MBT and LBT spark, how extreme your fueling will need to be just to keep the exhaust valves intack, how bad your knock limit will change for the given PR and adiabatic heating from the compressor, etc, etc.
too early for me, not enough coffee yet
in the simplest terms, you are limiting the possible mass flow into the air pump (ie engine) with the compressor size. That max limit will vary depending on where you operate on the map of the turbo, ie ideal mass flow for said air pump given a pressure ratio you intend to operate.
reguardless of how much flow you can actualy get from a given turbo, you're ultimately limited but how much heat you've added to the air. You will have to spark and fuel for that heat. Higher pressure ratios = more heat obviously, but extremely low efficiency at a low PR can give you more actually heating than a more efficient compressor at a higher PR.
There are MANY ways to look at it, and that's just on the "cold air" side of things. Turbine size and efficiency one the hot side can choke your air pump as well.
We could spend days on what effects various things will have on what's needed for MBT and LBT spark, how extreme your fueling will need to be just to keep the exhaust valves intack, how bad your knock limit will change for the given PR and adiabatic heating from the compressor, etc, etc.
too early for me, not enough coffee yet
09-10-2005 | 11:23 AM
#23
i'm interested in the effects of the difference in say the same exact motor,only difference being one with a 5.7 rod and say the other one with a 6.25.i know the longer rod motor will have the piston spending more time at tdc and bdc but will travel faster up and down the cylinders.anyone with any info if that will help or hurt a fi motor?
09-10-2005 | 11:50 AM
#25
BTW, just for quick comparison sake, lets take the most popular street unit out there and do some quick calcs with some consumption charts I have already avail.
Consumption for 346
Consumption for 408
Consumption for 575
Just a quick example here.....Take all the engines above and set them at 10psi, with 6500rpm limits. Now remember this is a compressor map for a 76-ptrim. No maps are available for the newer units like the GTS, but I do have some estimated compressor maps we came up with, but I can't let all the tricks out of the bag...lol. Now what we get is some total different efficiencies and engine output will greatly suffer for some.
346@6500 consumes = 62lbs min @1.68 pr = 70% efficiency.
408@6500 consumes = 72lbs min @1.68 pr = ~choke line. This means the 408 will be pushing the compressor into the super heating part of the map and the compressor blade just can not supply the air demanded by this engine.
575@6500 consumes = 100lbs min @1.68pr = restrictor plate racing...lol. This would be no more then a nice restrictor for this engine and would seriously hinder its peformance.
Jose
Consumption for 346
Consumption for 408
Consumption for 575
Just a quick example here.....Take all the engines above and set them at 10psi, with 6500rpm limits. Now remember this is a compressor map for a 76-ptrim. No maps are available for the newer units like the GTS, but I do have some estimated compressor maps we came up with, but I can't let all the tricks out of the bag...lol. Now what we get is some total different efficiencies and engine output will greatly suffer for some.
346@6500 consumes = 62lbs min @1.68 pr = 70% efficiency.
408@6500 consumes = 72lbs min @1.68 pr = ~choke line. This means the 408 will be pushing the compressor into the super heating part of the map and the compressor blade just can not supply the air demanded by this engine.
575@6500 consumes = 100lbs min @1.68pr = restrictor plate racing...lol. This would be no more then a nice restrictor for this engine and would seriously hinder its peformance.
Jose
09-10-2005 | 12:19 PM
#26
Wow, those comsumption charts really tell the story. Is that what you are going to be able to generate from your test stand? Are those available from Garrett or do you calculate them?
-Geoff
-Geoff
09-10-2005 | 12:23 PM
#27
The consumption charts are not generated on the test stand. The compressor maps are though. We are going to be doing testing on the new turbos we are coming out with....easy way to compare againist other units already out there. Plus we can take available units that are out there and improve upon them.
Jose
Jose
09-10-2005 | 12:24 PM
#28
FormerVendor
Joined: Nov 2001
Posts: 3,065
Likes: 5
From: Houston, Tx.
Originally Posted by slow trap
i'm interested in the effects of the difference in say the same exact motor,only difference being one with a 5.7 rod and say the other one with a 6.25.i know the longer rod motor will have the piston spending more time at tdc and bdc but will travel faster up and down the cylinders.anyone with any info if that will help or hurt a fi motor?
09-10-2005 | 12:35 PM
#29
FormerVendor
Joined: Nov 2001
Posts: 3,065
Likes: 5
From: Houston, Tx.
Jose, who says you have to run all these engines at 6500 rpm? That is what I am saying. The bigger engine will still make more power plus you can run a larger turbo on it if you want to run the engine at the same rpm and then you have even more power. You can't expect the same power band and gearing out of the large engine as compared to the small engine but it will make more power and go faster if both are geared right.
I do agree that if you are deciding to arbitrarily run a certain rpm at a certain engine size than you would also have to have just the right turbo size to run in that turbo's sweet spot at that exact rpm level. I am just saying that that's like these people that think a certain cylinder head can only support so many cubic inches and then they are surprised when they actuall go faster with a lot larger engine. Larger engines turning lower rpm are faster all the time in racing vs. the smaller stuff but of course larger engines turning higher rpm are even faster of course!
I do agree that if you are deciding to arbitrarily run a certain rpm at a certain engine size than you would also have to have just the right turbo size to run in that turbo's sweet spot at that exact rpm level. I am just saying that that's like these people that think a certain cylinder head can only support so many cubic inches and then they are surprised when they actuall go faster with a lot larger engine. Larger engines turning lower rpm are faster all the time in racing vs. the smaller stuff but of course larger engines turning higher rpm are even faster of course!
Originally Posted by JZ 97 SS 1500
BTW, just for quick comparison sake, lets take the most popular street unit out there and do some quick calcs with some consumption charts I have already avail.
Consumption for 346
Consumption for 408
Consumption for 575
Just a quick example here.....Take all the engines above and set them at 10psi, with 6500rpm limits. Now remember this is a compressor map for a 76-ptrim. No maps are available for the newer units like the GTS, but I do have some estimated compressor maps we came up with, but I can't let all the tricks out of the bag...lol. Now what we get is some total different efficiencies and engine output will greatly suffer for some.
346@6500 consumes = 62lbs min @1.68 pr = 70% efficiency.
408@6500 consumes = 72lbs min @1.68 pr = ~choke line. This means the 408 will be pushing the compressor into the super heating part of the map and the compressor blade just can not supply the air demanded by this engine.
575@6500 consumes = 100lbs min @1.68pr = restrictor plate racing...lol. This would be no more then a nice restrictor for this engine and would seriously hinder its peformance.
Jose
Consumption for 346
Consumption for 408
Consumption for 575
Just a quick example here.....Take all the engines above and set them at 10psi, with 6500rpm limits. Now remember this is a compressor map for a 76-ptrim. No maps are available for the newer units like the GTS, but I do have some estimated compressor maps we came up with, but I can't let all the tricks out of the bag...lol. Now what we get is some total different efficiencies and engine output will greatly suffer for some.
346@6500 consumes = 62lbs min @1.68 pr = 70% efficiency.
408@6500 consumes = 72lbs min @1.68 pr = ~choke line. This means the 408 will be pushing the compressor into the super heating part of the map and the compressor blade just can not supply the air demanded by this engine.
575@6500 consumes = 100lbs min @1.68pr = restrictor plate racing...lol. This would be no more then a nice restrictor for this engine and would seriously hinder its peformance.
Jose
09-10-2005 | 12:56 PM
#30
I see what you are saying. Now what I am explaining is for example, take a class rule that limits you to a single 76mm turbo, which I believe some NRMA classes do. You will want match the engine output and cubic inches with a compressor map that will support it most efficiently. Sure a bigger engine with a bigger turbo will go faster no one is arguing that point. If the class allowed unlimited cubes though, I doubt you would want to build a 575 ci motor with a T76 that will suffer, vs a smaller cube motor that will push the 76 to peak efficiency and greatest power output. What you would see is the 575 coming on boost almost instant and then boost would drop as efficiency dropped. Now by running less rpm you could keep the effiency up, but a 575 even at 4000rpms is going to be pushing choke limit. Run it above 6500 rpms and you would be looking at EGT's soaring and heads possibly lifting. The smaller cube motor properly matched would bring the turbo on boost quickly and then hold peak or near peak efficiency throughout a complete run. Either extreme, whether it be too big of cubes or too small of cubes will hinder the performance. Match it perfectly and you will have a hard running car.
Jose
Jose
Last edited by JZ 97 SS 1500; 09-10-2005 at 01:01 PM.
09-10-2005 | 01:14 PM
#31
Huh? How is this? The piston speed and changes in piston speed should be the same as it approaches and leaves TDC and BDC... unless you are accounting for some sort of stretch or flexing in the components?
Originally Posted by racer7088
The longer rod engine will slow the piston down near TDC but speed it up at BDC as compared to the shorter rod engine. This is a relatively tiny effect and also slightly affects cam timing relative to piston position and speed but again it's a very small change. Does not seem to matter much at all on 99 per cent of engines. I doubt it would affect relatively low rpm turbo engine at all. Possibly the shorter rods might help by reducing detonation sensitivity but again it's a small change.
09-10-2005 | 02:19 PM
#33
Jose, I expanded on you consumption for a 346.. It has been quite usefull for me.. http://73-ls1.com/misc/Airmap.xls
09-10-2005 | 02:31 PM
#34
Yeah I have a spreadsheet that runs the #'s. I just copy and paste them to an .htm file. You should see my diesel sheets....lol. Boost all the way to 175psi but only 4500rpms....hahaha. That is for our tractor puller customers and twin compound trucks....lol. We have a truck pull this upcoming tuesday night. We are taking our single turbo truck to run againist built compound twin turbo trucks to prove a point with our new compressor wheels.....hehe.
Our single turbo cummins made 570rwhp/1280rwtq @57psi with our (01) wheel...hehe. Truck is stock other then extra fueling, stacked boxes and exhaust. BTW, that is turbo alone...no N20, meth injection or propane.
Our single turbo cummins made 570rwhp/1280rwtq @57psi with our (01) wheel...hehe. Truck is stock other then extra fueling, stacked boxes and exhaust. BTW, that is turbo alone...no N20, meth injection or propane.
09-10-2005 | 03:06 PM
#36
that would be awsome, to have a freaking stock dodge truck with a different turbo and then make that kind of power.
Is it the stock manifold (exhaust) and just more fuel or whats the deal with that?
Is it the stock manifold (exhaust) and just more fuel or whats the deal with that?
09-10-2005 | 03:09 PM
#37
Yes still stock manifold. Just more fuel. BTW, EGT's are hitting 1750 when hooked to the sled...hehe... . Which is alot for a street truck....but not for the big boys. Some of our big tractor pullers are seeing 2100-2200 EGT's...hehe
. Which is alot for a street truck....but not for the big boys. Some of our big tractor pullers are seeing 2100-2200 EGT's...hehe
09-10-2005 | 03:14 PM
#38
what kind of turbo is it? seems like alot of the guys that are buying compound diesel kits are going to be wasting their money
Im wanting to get a dodge here in a year or two, to pull the TA, would be pretty sweet to have one that could pull the house out of the ground as well as the TA
Im wanting to get a dodge here in a year or two, to pull the TA, would be pretty sweet to have one that could pull the house out of the ground as well as the TA
09-10-2005 | 03:18 PM
#39
Its a custom hybrid. We will have a line of new units for the public soon. We are working on modding some units for MP. They will be awesome indeed and up to an 88mm . Also we want to flow test them first againist the best already on the market. We want to see the data differences between the units...not just skeptical say so.
Jose
. Also we want to flow test them first againist the best already on the market. We want to see the data differences between the units...not just skeptical say so.Jose