Cubic inches and Boost Correlation
9 Second Club
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
I dunno. He may have a point. Below are the specs on a model airplane engine.
SPECIFICATIONSDisplacement: 0.352 cu in (5.77cc)
Bore: 0.795 (20.2mm)
Stroke: 0.709 (18.0mm)
Practical RPM: 2,500-17,000
Output: 0.9PS 11,000 RPM
Weight: 12.8oz (363g) with muffler
17,000 rpm. Think of the possibilities. What would it take to get an s475 hooked up to that? It would not make much down low but it would really start to wake up somewhere around 6500 rpm. Also, don't forget the weight savings as it is all aluminum. I just remembered that it runs on nitromethane. This is really exciting. Will get back to you with the results.
SPECIFICATIONSDisplacement: 0.352 cu in (5.77cc)
Bore: 0.795 (20.2mm)
Stroke: 0.709 (18.0mm)
Practical RPM: 2,500-17,000
Output: 0.9PS 11,000 RPM
Weight: 12.8oz (363g) with muffler
17,000 rpm. Think of the possibilities. What would it take to get an s475 hooked up to that? It would not make much down low but it would really start to wake up somewhere around 6500 rpm. Also, don't forget the weight savings as it is all aluminum. I just remembered that it runs on nitromethane. This is really exciting. Will get back to you with the results.
9 Second Club
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
Start back at the beginning. I am asking the question because I was informed by a reputable builder that it is EASIER to make power with a 5.3 BECAUSE of the restriction, EASIER to make boost which translates to power, holds MORE boost because of block thickness. We all know that ultimately the bigger the setup the more power can be made, question was at what point do the lines on the graph cross
TECH Apprentice
Joined: Sep 2016
Posts: 347
Likes: 10
How much more boost can the 5.3 make vs the 6.0 because of the thicker walls
And, will that added boost in the 5.3 out-HP the 6.0 because it's limited to how much boost can be made given the thinner walls
And, will the 6.0 out-HP the 5.3 from that naturally gained power, but lesser boost?
I wouldn't call it ABSOLUTE bullshit, I'd just call it "mostly bullshit"
OP is wondering where the lines cross as in... will the higher boost out-weigh the N/A power from the 6.0 with lesser boost.
So the ULTIMATE question is:
How much MORE boost can the 5.3 with thicker walls REALLY make? I'm sure this has been answered a million times before.
Last edited by AndyTA; Dec 18, 2019 at 11:54 AM.
The fact is I have both a 5.3 and a 6.0 in my shop, one of which will get built (forged rotating) for Turbo use. I also have a set of 243's that have been "stage III" CNC ported with 2.08 intake valves. This is a 95% track vehicle on race fuel and planning to spray meth. Goals are to see 850ish whp
Indeed! Sumtinggg rongggg
9 Second Club
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
The question is:
How much more boost can the 5.3 make vs the 6.0 because of the thicker walls
And, will that added boost in the 5.3 out-HP the 6.0 because it's limited to how much boost can be made given the thinner walls
And, will the 6.0 out-HP the 5.3 from that naturally gained power, but lesser boost?
I wouldn't call it ABSOLUTE bullshit, I'd just call it "mostly bullshit"
OP is wondering where the lines cross as in... will the higher boost out-weigh the N/A power from the 6.0 with lesser boost.
So the ULTIMATE question is:
How much MORE boost can the 5.3 with thicker walls REALLY make? I'm sure this has been answered a million times before.
How much more boost can the 5.3 make vs the 6.0 because of the thicker walls
And, will that added boost in the 5.3 out-HP the 6.0 because it's limited to how much boost can be made given the thinner walls
And, will the 6.0 out-HP the 5.3 from that naturally gained power, but lesser boost?
I wouldn't call it ABSOLUTE bullshit, I'd just call it "mostly bullshit"
OP is wondering where the lines cross as in... will the higher boost out-weigh the N/A power from the 6.0 with lesser boost.
So the ULTIMATE question is:
How much MORE boost can the 5.3 with thicker walls REALLY make? I'm sure this has been answered a million times before.
It is not the statement/question made in the OP's question here.
And even though it has been repeated...I'll repeat it again. It is only n the latter comment AFTER it other concerns were highlighted did he add comments about wall thickness....but that was never in the original comments. NOR does it make an engine create boost easier because of restrictions, nor does more restrictions mean more power...etc etc etc.
I am new to the boost scene, and have questions.....
I have been told that all things the same (as in properly sized cam, injectors, same compression, properly sized Turbo etc) a 5.3 is "easier" to make boost with than a 6.0. What is the truth of this and if so the reasoning?
I have also been told that using ported heads makes it harder to make boost? Again if so why?
I have been told that all things the same (as in properly sized cam, injectors, same compression, properly sized Turbo etc) a 5.3 is "easier" to make boost with than a 6.0. What is the truth of this and if so the reasoning?
I have also been told that using ported heads makes it harder to make boost? Again if so why?
Start back at the beginning. I am asking the question because I was informed by a reputable builder that it is EASIER to make power with a 5.3 BECAUSE of the restriction, EASIER to make boost which translates to power, holds MORE boost because of block thickness. We all know that ultimately the bigger the setup the more power can be made, question was at what point do the lines on the graph cross
TECH Apprentice
Joined: Sep 2016
Posts: 347
Likes: 10
No, that is something you made up.
It is not the statement/question made in the OP's question here.
And even though it has been repeated...I'll repeat it again. It is only n the latter comment AFTER it other concerns were highlighted did he add comments about wall thickness....but that was never in the original comments. NOR does it make an engine create boost easier because of restrictions, nor does more restrictions mean more power...etc etc etc.
It is not the statement/question made in the OP's question here.
And even though it has been repeated...I'll repeat it again. It is only n the latter comment AFTER it other concerns were highlighted did he add comments about wall thickness....but that was never in the original comments. NOR does it make an engine create boost easier because of restrictions, nor does more restrictions mean more power...etc etc etc.
Start back at the beginning. I am asking the question because I was informed by a reputable builder that it is EASIER to make power with a 5.3 BECAUSE of the restriction, EASIER to make boost which translates to power, holds MORE boost because of block thickness. We all know that ultimately the bigger the setup the more power can be made, question was at what point do the lines on the graph cross
Boost is indicative of flow efficiency.
For example: I ran a TC7868 turbo on my LS1 six speed car at 11 lbs. of boost, single 255 fuel pump, stock fuel system.
After changing the turbo to a T7875 and changing literally nothing else a second 255 had to be added to the fuel system and additional fuel added to the tune.
Why?
Because the larger frame turbo moved a larger volume of air more efficiently at the same boost level.
Stop thinking you need lots of boost to make power or that boost means power.
I make just shy of 700whp on 12-13lbs on pump fuel, seen plenty of guys make less power with more boost.
Making power is entirely dependent upon the combination and not solely the displacement of the engine.
Yes a larger engine will make more power but a smaller engine can make just as much power with the correct combination, I think the 2JZ platform is a good example.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
Thread Starter
Staging Lane
Joined: Apr 2019
Posts: 63
Likes: 4
Exactly. While I may have not directly mentioned wall thickness, it was definitely part of the discussion from said builder as part of the benefit of a 5.3. Capable of just adding more boost to overcome displacement.
TECH Fanatic
Joined: Feb 2015
Posts: 1,080
Likes: 178
6.0 is 13% larger than 5.3. Spin a 5.3 13% more rpm than 6.0 and you now have a 6.0 air pump. Add fuel and spark and you're done. Or, add 13% more cylinder pressure/volume/flow (boost) and get similar output of 6.0. At 850, either motor will be fine. Personally, I'd go with thicker more stable cylinder if you want longer term reliability. If you want to turn it up, again the thicker wall wins. i.e. Which will perform and last longer at 1200hp? 5.3. Hope this makes sense.
I've always like the hp to boost formula vs cid to boost. Example: if you have a mild 5.3 making 400hp na and add 15 lbs of boost you get roughly 800hp. Or a mild 6.0 making 475hp na would make 950 hp at the same 15 psi . By the same token, if you built a hot na 5.3 making 475 hp na, you would make the same 950 hp at 15 lbs.
another way to compute hp to boost would be to take the two theoretical engines and divide their na power by 14.7. This will give you a rough idea, given a properly sized turbo, how much hp each engine will make per psi. My calculations say the mild 5.3 will increase 27hp per psi and the 6.0 would increase 32hp per psi. That's based on 400 and 475 hp na.
it comes down to how much hp you make NA, not so much the cid of the engine. if the op wanted to use the mild 400hp 5.3 to make as much hp as the mild 475hp 6.0 at 15psi he would have to push the 5.3 to 20psi. 27.2x20=544hp+400na=944hp at 20psi.
All of these numbers are optimistic because they dont take into account pumping losses through the restrictive turbine , so 3 to 5% can be deducted for that. These are FWHP numbers obviously, so you all know the drill on drivetrain losses .
another way to compute hp to boost would be to take the two theoretical engines and divide their na power by 14.7. This will give you a rough idea, given a properly sized turbo, how much hp each engine will make per psi. My calculations say the mild 5.3 will increase 27hp per psi and the 6.0 would increase 32hp per psi. That's based on 400 and 475 hp na.
it comes down to how much hp you make NA, not so much the cid of the engine. if the op wanted to use the mild 400hp 5.3 to make as much hp as the mild 475hp 6.0 at 15psi he would have to push the 5.3 to 20psi. 27.2x20=544hp+400na=944hp at 20psi.
All of these numbers are optimistic because they dont take into account pumping losses through the restrictive turbine , so 3 to 5% can be deducted for that. These are FWHP numbers obviously, so you all know the drill on drivetrain losses .
Last edited by newschool72; Dec 26, 2019 at 10:21 AM. Reason: Adding
Teching In
Joined: Dec 2019
Posts: 12
Likes: 0
If you are looking at restriction being easier to make power because it makes more boost that's nonsense. Why do some turbos not make boost until a higher RPM? Why once they start to light do they come on quickly? Because they are driven off of the heat energy of the exhaust gases coming out of the engine and the higher RPM moves more air. Once they start to make boost the engine dumps more exhaust gasses to drive the turbo faster. So if an engine breathes easier (less restriction) it will move more air (more power) sooner thereby lighting the turbo sooner (more useable powerband from same turbo). If it moves air easier less boost is the same power. Less boost means less load on the turbo so less drive pressure required. All that means faster spool and less power robbing back pressure.
I've got a 427 that I just built for my Chevelle that at 3psi makes 850hp and at 16psi makes 1500hp. That's flywheel hp on 93 pump gas on the engine dyno since I don't have it in the car yet. The engine breathes well so it makes right around 50hp/pound of boost with very fast spool. The result is I can shape the torque curve to what I want once in the car. This will be a driver so it will be on a 3psi spring most of the time. At the strip I'll figure out what the tires will take in each gear and tune the boost controller to that. The motor came in at 469lbs with headers and full front dress including AC.(turbos not installed as we were loading it into my truck)
I've got a 427 that I just built for my Chevelle that at 3psi makes 850hp and at 16psi makes 1500hp. That's flywheel hp on 93 pump gas on the engine dyno since I don't have it in the car yet. The engine breathes well so it makes right around 50hp/pound of boost with very fast spool. The result is I can shape the torque curve to what I want once in the car. This will be a driver so it will be on a 3psi spring most of the time. At the strip I'll figure out what the tires will take in each gear and tune the boost controller to that. The motor came in at 469lbs with headers and full front dress including AC.(turbos not installed as we were loading it into my truck)
If you are looking at restriction being easier to make power because it makes more boost that's nonsense. Why do some turbos not make boost until a higher RPM? Why once they start to light do they come on quickly? Because they are driven off of the heat energy of the exhaust gases coming out of the engine and the higher RPM moves more air. Once they start to make boost the engine dumps more exhaust gasses to drive the turbo faster. So if an engine breathes easier (less restriction) it will move more air (more power) sooner thereby lighting the turbo sooner (more useable powerband from same turbo). If it moves air easier less boost is the same power. Less boost means less load on the turbo so less drive pressure required. All that means faster spool and less power robbing back pressure.
I've got a 427 that I just built for my Chevelle that at 3psi makes 850hp and at 16psi makes 1500hp. That's flywheel hp on 93 pump gas on the engine dyno since I don't have it in the car yet. The engine breathes well so it makes right around 50hp/pound of boost with very fast spool. The result is I can shape the torque curve to what I want once in the car. This will be a driver so it will be on a 3psi spring most of the time. At the strip I'll figure out what the tires will take in each gear and tune the boost controller to that. The motor came in at 469lbs with headers and full front dress including AC.(turbos not installed as we were loading it into my truck)
I've got a 427 that I just built for my Chevelle that at 3psi makes 850hp and at 16psi makes 1500hp. That's flywheel hp on 93 pump gas on the engine dyno since I don't have it in the car yet. The engine breathes well so it makes right around 50hp/pound of boost with very fast spool. The result is I can shape the torque curve to what I want once in the car. This will be a driver so it will be on a 3psi spring most of the time. At the strip I'll figure out what the tires will take in each gear and tune the boost controller to that. The motor came in at 469lbs with headers and full front dress including AC.(turbos not installed as we were loading it into my truck)
TECH Fanatic
Joined: Dec 2019
Posts: 1,129
Likes: 478
People really worry about that boost number way too much. I still shake my head when someone says "I'm going to spend $2500 on heads just to keep the boost down".
Turn up the boost. Stop worrying about stressing your silicone couplers and MAP sensor.
Turn up the boost. Stop worrying about stressing your silicone couplers and MAP sensor.
If its a guy that's maxed out his class turbo and needs more power, heads are a solid move. Or because they already made 1200 on stock heads and want to push further and paying for the thicker deck... maybe. But if its a guy starting out and just throwing money at a build blindly then absolutely true.