lower boost + higher stat. comp vs higher boost + lower..
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lifelong learner
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lower boost + higher stat. comp vs higher boost + lower..
all while on pump gas.
what are everyones views on this in the turbo honda world.
with the advent of hondata and other affordable engine management systems, the ability to tune either way is very easy. now, which way would you rather go, or which way do you think is better, and why.
please try to support all arguments with evidence of theory in the form of dyno charts, 1/4 et's, etc.
i dont want to hear everyones hypotheical crap, because all you idiots dont know what youre talking about half the time anywyas.
i'll post my ideas on this subject after a few replies. no i wont change mine.
what are everyones views on this in the turbo honda world.
with the advent of hondata and other affordable engine management systems, the ability to tune either way is very easy. now, which way would you rather go, or which way do you think is better, and why.
please try to support all arguments with evidence of theory in the form of dyno charts, 1/4 et's, etc.
i dont want to hear everyones hypotheical crap, because all you idiots dont know what youre talking about half the time anywyas.
i'll post my ideas on this subject after a few replies. no i wont change mine.
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rest in peace tim.
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rest in peace tim.
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There aren't very many people here who know mad craziness about hondas. Other then most who you have access to on a daily basis.
I like the idea of having decent power while not under boost, and Ive seen Mike and Chris' car w/ that 10:1 static ratio, and thier dyno was perty mean at only 12psi. Not to mention 160mph+ (seeing the tires afterwords was crazy) on thier dyno.
Lower compression is a good saftey factor IMHO, and it also allows at times alot more boost. Which is always a plus. Although driving not under boost sucks, and is not very responsive.
I think with the proper tuning the higher compression would have a better curve and overall better numbers.
But that's just my hypotherical crap.
I like the idea of having decent power while not under boost, and Ive seen Mike and Chris' car w/ that 10:1 static ratio, and thier dyno was perty mean at only 12psi. Not to mention 160mph+ (seeing the tires afterwords was crazy) on thier dyno.
Lower compression is a good saftey factor IMHO, and it also allows at times alot more boost. Which is always a plus. Although driving not under boost sucks, and is not very responsive.
I think with the proper tuning the higher compression would have a better curve and overall better numbers.
But that's just my hypotherical crap.
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lifelong learner
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what's preventing a lower compressioned car to run 16-19 pounds on pump gas and putting out better numbers than the high cr car, and having a better power band due to a properly sized turbo?
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I guess nothing as long as you have a small turbo that produces good power low end, but they're hardpressed to find one that produces solid power and torque numbers below say, 3500rpm. As long as you can keep the intake temps down. 19psi is alot of heat on a smaller turbo. Im not very familiar with many different types of turbo's tho, so I could be misinformed.
Ive seen t25's pushing out 22psi. I do not know thier efficiency at such boost levels. I can't imagine it would be great. Although a t25 might be hard to get to spool to... 8k rpm like Honda motors love to do. As long as it's not so high-reving, the turbo wouldn't get out-spooled(I don't recall the term). Peaking at near or over it's efficiency RPM, it would take a nice cool day, methanol injection and a WELL matched intercooler. Not to mention a good tuner.
Again, these are just my limited knowledge theories on the matter. I have very little expierence with engines and thier dynamic, even less with boosted engines. Hope Ive been of some help. Maybe someone else could pop in and school me on what im wrong about.
As far as your question. You know the answer and what would have to be over come.
Detonation, Aluminum block, Fuel, and Tuning. Sleeves would probably be a must for that much boost on a Honda block. Altho I believe Mike and Chris said they've run 19psi on that LS motor. (With race gas though.) I might not be remembering correctly. So don't quote me.
Ive seen t25's pushing out 22psi. I do not know thier efficiency at such boost levels. I can't imagine it would be great. Although a t25 might be hard to get to spool to... 8k rpm like Honda motors love to do. As long as it's not so high-reving, the turbo wouldn't get out-spooled(I don't recall the term). Peaking at near or over it's efficiency RPM, it would take a nice cool day, methanol injection and a WELL matched intercooler. Not to mention a good tuner.
Again, these are just my limited knowledge theories on the matter. I have very little expierence with engines and thier dynamic, even less with boosted engines. Hope Ive been of some help. Maybe someone else could pop in and school me on what im wrong about.
As far as your question. You know the answer and what would have to be over come.
Detonation, Aluminum block, Fuel, and Tuning. Sleeves would probably be a must for that much boost on a Honda block. Altho I believe Mike and Chris said they've run 19psi on that LS motor. (With race gas though.) I might not be remembering correctly. So don't quote me.
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Here is the bottom line though I know you already said you don't want to hear thermo theory about how engines work.
The two primary factors that control power output in a motor are actual compression ratio (boost+compression) and the mass/sec of fuel/air the engine can process.
Since the turbo is creating compression and increasing the mass/sec the engine can process by using energy that is normally lost in the exhaust gasses that is something you want to maximize through the highest possible boost.
Regular piston compression is stealing valuable crank power and limits the amount of boost you can run.
Before you go against this by thinking that you can run high compression and high boost by running pig rich, don't forget that you sacrafice the available power you can get from each gram of fuel/air the engine processes by doing so. The math could easily work out that whatever advantage you gain from increased boost is defeated by the power losses from a super rich mix.
For this reason the best combo for max power is low piston compression and high boost.
Intercooling, plumbing efficiency and good tuning is all about pushing the envelope of these basic principles.
The only downside of this combo is that your power output sucks until you hit boost, and this is the only reason for going against the low compression / high boost combo.
Its the only reason I want to bump the compression in my car from 7:1 up to about 7.5:1.
These are solid scientific facts that you can verify by looking at every high output turbo motor that is built to reliably to run on pump gas.
Reading a book on the subject of thermodynamics could also do wonders for you too.
The two primary factors that control power output in a motor are actual compression ratio (boost+compression) and the mass/sec of fuel/air the engine can process.
Since the turbo is creating compression and increasing the mass/sec the engine can process by using energy that is normally lost in the exhaust gasses that is something you want to maximize through the highest possible boost.
Regular piston compression is stealing valuable crank power and limits the amount of boost you can run.
Before you go against this by thinking that you can run high compression and high boost by running pig rich, don't forget that you sacrafice the available power you can get from each gram of fuel/air the engine processes by doing so. The math could easily work out that whatever advantage you gain from increased boost is defeated by the power losses from a super rich mix.
For this reason the best combo for max power is low piston compression and high boost.
Intercooling, plumbing efficiency and good tuning is all about pushing the envelope of these basic principles.
The only downside of this combo is that your power output sucks until you hit boost, and this is the only reason for going against the low compression / high boost combo.
Its the only reason I want to bump the compression in my car from 7:1 up to about 7.5:1.
These are solid scientific facts that you can verify by looking at every high output turbo motor that is built to reliably to run on pump gas.
Reading a book on the subject of thermodynamics could also do wonders for you too.
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No, only if you don't compensate other factors to allow the higher PSI levels.
IE: Larger More efficent Intercooler, More fuel pressure, there really is no limit.
IE: Larger More efficent Intercooler, More fuel pressure, there really is no limit.
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There is a limit before your mix spontaneously ignites which is known better as detonation. This is usually a very bad thing for motors with a lot of mix crammed into their cylinders.
How much you can cram in before this happens depends on a lot of factors which are controlled by things such as intercooling, tuning and plumbing efficiency.
This is where the fine art of knowing what you can get away with for a particular combo comes into play and I imagine is the kind of info Matt was really looking for in this post.
The scientist in me prefers to start with reasonable estimates of where things should be and let testing, tuning and other adjustments push things up from there.
How much you can cram in before this happens depends on a lot of factors which are controlled by things such as intercooling, tuning and plumbing efficiency.
This is where the fine art of knowing what you can get away with for a particular combo comes into play and I imagine is the kind of info Matt was really looking for in this post.
The scientist in me prefers to start with reasonable estimates of where things should be and let testing, tuning and other adjustments push things up from there.
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Not sure about Honda's (although I doubt they are breaking the laws of physics), but you generally can make more HP with lower compression and more boost. As you mentioned, there is a tradeoff in off boost HP which is mushy with low compression. So basically, if you are going with a "hot" street car, keep higher compression and limit boost. For a drag car, lower the compression and up the boost. Take a look at the turbo Dodge's. They run pretty low compression (not sure exactly what, but its a non interference motor), and they routinely run 25-30 lbs of boost on street motors. This could never be possible on a 10:1 Honda motor.
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MY Dodge GLH-S is 8.5 ratio, but your quote about 25 to 30 psi on TD street cars is almost correct.
I ran my GLH-S around on the street with 22 plus psi pushing 350 hp and 380 TQ....
I ran my GLH-S around on the street with 22 plus psi pushing 350 hp and 380 TQ....
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