How Much Boost w/ 9.3:1 OEM Pistons?
01-21-2004, 10:46 AM
#1
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How Much Boost w/ 9.3:1 OEM Pistons?
I know the main killer of boosted preludes are weak ring lands. They blow out b/c the cylinder pressures are too high and the lands can't support the load.
I am building an H23 VTEC and am tryin to do a bit of theorizing, but couldn't find a formula for calculating static cylinder pressure.
I have heard of USDM and JDM H22's running 10-11psi at the track and being fine, w/ good tuning. Assuming this is the max for that setup, how much more could I handle at 9.3:1, using factory pistons?
I am building an H23 VTEC and am tryin to do a bit of theorizing, but couldn't find a formula for calculating static cylinder pressure.
I have heard of USDM and JDM H22's running 10-11psi at the track and being fine, w/ good tuning. Assuming this is the max for that setup, how much more could I handle at 9.3:1, using factory pistons?
01-21-2004, 11:41 AM
#3
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Re: How Much Boost w/ 9.3:1 OEM Pistons? (LudeyKrus)
I still wouldn't go over 10psi with only a half pt lower of compression. Daily I would stick with 8psi. 1 or 2 more pounds of boost is really not going to make that much difference. Would you rather have a car that lasts a long time or one with 20more whp and only lasts a month? With race gas you can get a little more power by adding a bit of timing.
01-21-2004, 01:20 PM
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Re: How Much Boost w/ 9.3:1 OEM Pistons? (Turbo Sam)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Turbo Sam »</TD></TR><TR><TD CLASS="quote">47 POUNDS ON 87 OCTANE!!!!!!!!!!!!</TD></TR></TABLE>
Been there done that, wasn't too thrilling.....
I've heard of 10psi at the track on H22's, so I would figure more since I'll be dropping from ~10.6:1 to ~9.3:1 (I've heard of JDM H22's).
Assuming ring lands were the only restriction, It seems like going lower would yield a higher tolerance to boost.
And I would be using 93 octane.
Been there done that, wasn't too thrilling.....
I've heard of 10psi at the track on H22's, so I would figure more since I'll be dropping from ~10.6:1 to ~9.3:1 (I've heard of JDM H22's).
Assuming ring lands were the only restriction, It seems like going lower would yield a higher tolerance to boost.
And I would be using 93 octane.
01-21-2004, 02:22 PM
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Re: How Much Boost w/ 9.3:1 OEM Pistons? (LudeyKrus)
I didnt know you were gonna be boosting this motor. Man I would still not go over 10 psi at the track and like 8 daily.
01-21-2004, 04:11 PM
#7
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I'm not gonna be for a while, but I'm toying w/ the idea. I like the concept of dropping compression down a point w/o any internal work.
If I do it, then i'm gonna be crankin it up to see what's the limits. I'd like to hit around 14psi at the track, and it makes sense to me that it should be able to handle around that much.
If I do it, then i'm gonna be crankin it up to see what's the limits. I'd like to hit around 14psi at the track, and it makes sense to me that it should be able to handle around that much.
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01-21-2004, 04:38 PM
#8
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Re: (LudeyKrus)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by LudeyKrus »</TD></TR><TR><TD CLASS="quote"> I'd like to hit around 14psi at the track, and it makes sense to me that it should be able to handle around that much.</TD></TR></TABLE>
It's not going to happen. If it does, then it won't last long. The f22a has a 8.8:1 compression... so according to your theory the motor should be able to boost 18-20psi stock, right? Nope.
I say go ahead and boost 14psi at the track and come back and tell us how the motor runs a week later.
It's not going to happen. If it does, then it won't last long. The f22a has a 8.8:1 compression... so according to your theory the motor should be able to boost 18-20psi stock, right? Nope.
I say go ahead and boost 14psi at the track and come back and tell us how the motor runs a week later.
01-21-2004, 05:50 PM
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Re: (PrecisionH23a)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by PrecisionH23a »</TD></TR><TR><TD CLASS="quote">
I say go ahead and boost 14psi at the track and come back and tell us how the motor runs a week later.</TD></TR></TABLE>
Will do!
I've seen dynos of F22's making GOOD horsepower on stock blocks, so yes, the theory is somewhat correct. Can anyone explain how lowering compression will NOT let you run higher boost?
I say go ahead and boost 14psi at the track and come back and tell us how the motor runs a week later.</TD></TR></TABLE>
Will do!
I've seen dynos of F22's making GOOD horsepower on stock blocks, so yes, the theory is somewhat correct. Can anyone explain how lowering compression will NOT let you run higher boost?
01-21-2004, 07:13 PM
#10
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Re: (LudeyKrus)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by LudeyKrus »</TD></TR><TR><TD CLASS="quote">
Can anyone explain how lowering compression will NOT let you run higher
boost?</TD></TR></TABLE>
I think you are mixed up in what I was trying to tell you. Lowering compression will allow you to run a higher amount of boost safer. But the problem with the H series motor is the ring-lands as we have already discussed. Personally, I would not take a stock H series motor above 9psi at the track. Once you start experiencing problems you will wish you had played it safe. Your theory does hold true, but I think 14psi is REALLY pushing it. If this is your daily driver, then I seriously think you should consider running maybe 11-12psi at the MOST only at the track. 1 or 2 psi is not worth a rebuild that will cost $3-$5k.
High compression FI increases the loads placed on the rods, bearings, rod bolts and etc. far greater than low compression ratio's with higher boost. You are placing the internal components under greater stress, so the likelyhood of bearing/rod failure is greater... same as the load placed to the ringlands. Without doing extensive number crunching, the stresses should be at least 5-10% greater.
High compression engines produce more power, but they also produce more heat... so essentially you will need a good consistent air/fuel combination to avoid detonation. Higher compression motors also boost faster. When under boost, you generally want to retard your ignition timing. By doing so, you are also decreasing temperatures. If you are running a heavily advanced ignition timing when under boost you generally will experience overheating, detonation, and/or a blown headgasket.
In boosted cars, the turbine is sending compressed air into the cylinders. This alone can raise the air temperature causing the engine to detonate. So as a safety measure lowerering the compression X amount reduces the chaces of detonation and raises the threshold for boost.
As far as heat is concerned, the higher compression will yield a higher energy (heat) per combustion than a lower compression engine. The higher compression makes the engine more efficient thermodynamically with its heat (energy), so you can spool up a larger turbo or gain spool up time on the exsisting turbocharger. There becomes a point where the compression will pre-ignite no matter how cold of spark plug you run, or how much you reduce the timing. With high compression and boost the two biggest things are running colder plugs as well as reducing the timing around .75 degrees per pound of boost.
So in conclusion, there would be more stress with a higher compression set-up. The cylinder pressure would be greater than a lower compression set-up. Retarding the timing is the normal practice to lower cylinder pressure, but you'll find that higher compression engines will also have a higher cylinder pressure even with reducing timing. Yes lowering the compression will allow you to boost more, a large amount of B series guys do this left and right. But remember, they do not have to worry about weak ringlands on their pistons. I honestly think that a half pt cr reduction is not significant enough to run 14psi at the track frequently while retaining the car as a daily driver.
Can anyone explain how lowering compression will NOT let you run higher
boost?</TD></TR></TABLE>
I think you are mixed up in what I was trying to tell you. Lowering compression will allow you to run a higher amount of boost safer. But the problem with the H series motor is the ring-lands as we have already discussed. Personally, I would not take a stock H series motor above 9psi at the track. Once you start experiencing problems you will wish you had played it safe. Your theory does hold true, but I think 14psi is REALLY pushing it. If this is your daily driver, then I seriously think you should consider running maybe 11-12psi at the MOST only at the track. 1 or 2 psi is not worth a rebuild that will cost $3-$5k.
High compression FI increases the loads placed on the rods, bearings, rod bolts and etc. far greater than low compression ratio's with higher boost. You are placing the internal components under greater stress, so the likelyhood of bearing/rod failure is greater... same as the load placed to the ringlands. Without doing extensive number crunching, the stresses should be at least 5-10% greater.
High compression engines produce more power, but they also produce more heat... so essentially you will need a good consistent air/fuel combination to avoid detonation. Higher compression motors also boost faster. When under boost, you generally want to retard your ignition timing. By doing so, you are also decreasing temperatures. If you are running a heavily advanced ignition timing when under boost you generally will experience overheating, detonation, and/or a blown headgasket.
In boosted cars, the turbine is sending compressed air into the cylinders. This alone can raise the air temperature causing the engine to detonate. So as a safety measure lowerering the compression X amount reduces the chaces of detonation and raises the threshold for boost.
As far as heat is concerned, the higher compression will yield a higher energy (heat) per combustion than a lower compression engine. The higher compression makes the engine more efficient thermodynamically with its heat (energy), so you can spool up a larger turbo or gain spool up time on the exsisting turbocharger. There becomes a point where the compression will pre-ignite no matter how cold of spark plug you run, or how much you reduce the timing. With high compression and boost the two biggest things are running colder plugs as well as reducing the timing around .75 degrees per pound of boost.
So in conclusion, there would be more stress with a higher compression set-up. The cylinder pressure would be greater than a lower compression set-up. Retarding the timing is the normal practice to lower cylinder pressure, but you'll find that higher compression engines will also have a higher cylinder pressure even with reducing timing. Yes lowering the compression will allow you to boost more, a large amount of B series guys do this left and right. But remember, they do not have to worry about weak ringlands on their pistons. I honestly think that a half pt cr reduction is not significant enough to run 14psi at the track frequently while retaining the car as a daily driver.
01-21-2004, 07:48 PM
#11
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Re: (PrecisionH23a)
Whoa, didn't know who I was talkin to! Nice name....
My point was that I've heard of more than one person occasionally push 10-11psi through an H22, one of which was a JDM H22. So you figure 10.6:1, running that boost and not blowing.
Knock it down to 9.3:1, and that's over a full point dropped in compression. If I remember correctly, as you lower the compression, the amount of boost that should be able to be safely pushed through the motor increases more and more, almost exponentially (so i was told). So if 10 psi well tuned is alright for the occasional track day, then 13-14psi seems do-able on a lower compression, higher displacement motor.
It's just my train of thought that lower compression will greatly decrease the pressure on the ring lands, increasing the motor's boost capacity.
Like previously said, this is all just brainstorming. It'll be a while before I can come close to boosting my car; right now I'm just tryin to get the damn thing to crank!
My point was that I've heard of more than one person occasionally push 10-11psi through an H22, one of which was a JDM H22. So you figure 10.6:1, running that boost and not blowing.
Knock it down to 9.3:1, and that's over a full point dropped in compression. If I remember correctly, as you lower the compression, the amount of boost that should be able to be safely pushed through the motor increases more and more, almost exponentially (so i was told). So if 10 psi well tuned is alright for the occasional track day, then 13-14psi seems do-able on a lower compression, higher displacement motor.
It's just my train of thought that lower compression will greatly decrease the pressure on the ring lands, increasing the motor's boost capacity.
Like previously said, this is all just brainstorming. It'll be a while before I can come close to boosting my car; right now I'm just tryin to get the damn thing to crank!
01-21-2004, 07:56 PM
#12
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Re: (LudeyKrus)
I got sick of the Gude name... why should I promote their product when they gave me such BS.
Anyways, without number crunching you are looking at 5-10% less internal stress with around a 1.3-2.0 CR drop. Remember, some motors are healtheir then others too. There is always that one motor that for some reason last longer and can endure more stress then the other motors out there. Why? I have no clue, that's just how it is. I would be very careful as I have already advised you, let us know how it all comes out.
Anyways, without number crunching you are looking at 5-10% less internal stress with around a 1.3-2.0 CR drop. Remember, some motors are healtheir then others too. There is always that one motor that for some reason last longer and can endure more stress then the other motors out there. Why? I have no clue, that's just how it is. I would be very careful as I have already advised you, let us know how it all comes out.
01-21-2004, 11:04 PM
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Re: (PrecisionH23a)
how did you set up your si to run 20 psi? if your saying that he cant run 13 psi?
as im looking to swap my f22 and get an h22 or an h23 and add a turbo later on.
as im looking to swap my f22 and get an h22 or an h23 and add a turbo later on.
01-21-2004, 11:12 PM
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01-21-2004, 11:35 PM
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Re: (PrecisionH23a)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by PrecisionH23a »</TD></TR><TR><TD CLASS="quote">Because I am a magician.</TD></TR></TABLE>
nice reply
nice reply
01-22-2004, 09:21 AM
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Re: (PrecisionH23a)
Higher compression means less boost needed to produce more power, yeah it's tricky, but it can me done with proper tuning. Firedrake is running 13 psi on stock internals, so am i soon to be with my stock h23a2 prelude.
I also say 14 psi is pushing it, but once in a while it shouldn't be a problem if you have a properly maintained engine.
I'm from europe and we run different fuel in our engines(higher grade)but i've ran a stock internal Vti civic(1994)turbo for more than 6 months on 14.7 psi. No problem what so ever. Just don;t put your foot down all the time.
I don't push my cars hard everytime, and take care of my engine all the time.
I come form The Netherlands. That means LOW LANDS (we are under sea level)So we have less dense air, so cars breath better.
And we run 98 fuel and higher, maybe that's why my engines last as long as they do.
Tuning is the key.
I also say 14 psi is pushing it, but once in a while it shouldn't be a problem if you have a properly maintained engine.
I'm from europe and we run different fuel in our engines(higher grade)but i've ran a stock internal Vti civic(1994)turbo for more than 6 months on 14.7 psi. No problem what so ever. Just don;t put your foot down all the time.
I don't push my cars hard everytime, and take care of my engine all the time.
I come form The Netherlands. That means LOW LANDS (we are under sea level)So we have less dense air, so cars breath better.
And we run 98 fuel and higher, maybe that's why my engines last as long as they do.
Tuning is the key.
01-22-2004, 09:54 AM
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Re: (musclefella)
Dont boost it man unless you take it back apart and replace the pistons and rods.
Sp you said you were trying to get it to crank.... I asume you got it all put together. Did you use the manuel tensioner?
Sp you said you were trying to get it to crank.... I asume you got it all put together. Did you use the manuel tensioner?
01-22-2004, 10:14 AM
#18
Re: (musclefella)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by musclefella »</TD></TR><TR><TD CLASS="quote">Higher compression means less boost needed to produce more power, yeah it's tricky, but it can me done with proper tuning. Firedrake is running 13 psi on stock internals, so am i soon to be with my stock h23a2 prelude.
I also say 14 psi is pushing it, but once in a while it shouldn't be a problem if you have a properly maintained engine.
I'm from europe and we run different fuel in our engines(higher grade)but i've ran a stock internal Vti civic(1994)turbo for more than 6 months on 14.7 psi. No problem what so ever. Just don;t put your foot down all the time.
I don't push my cars hard everytime, and take care of my engine all the time.
I come form The Netherlands. That means LOW LANDS (we are under sea level)So we have less dense air, so cars breath better.
And we run 98 fuel and higher, maybe that's why my engines last as long as they do.
Tuning is the key.</TD></TR></TABLE>
""In Europe, the Research Octane Number (RON) standard is used, whereas the US uses an average of MON and RON, the Anti-Knock Index (AKI). In comparison, AKI 91 octane in the US is the equivalent of RON 95 octane in Europe.""
Our 93 octane, is the same as your 98 octane
I also say 14 psi is pushing it, but once in a while it shouldn't be a problem if you have a properly maintained engine.
I'm from europe and we run different fuel in our engines(higher grade)but i've ran a stock internal Vti civic(1994)turbo for more than 6 months on 14.7 psi. No problem what so ever. Just don;t put your foot down all the time.
I don't push my cars hard everytime, and take care of my engine all the time.
I come form The Netherlands. That means LOW LANDS (we are under sea level)So we have less dense air, so cars breath better.
And we run 98 fuel and higher, maybe that's why my engines last as long as they do.
Tuning is the key.</TD></TR></TABLE>
""In Europe, the Research Octane Number (RON) standard is used, whereas the US uses an average of MON and RON, the Anti-Knock Index (AKI). In comparison, AKI 91 octane in the US is the equivalent of RON 95 octane in Europe.""
Our 93 octane, is the same as your 98 octane
01-22-2004, 10:45 AM
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Re: (LudeyKrus)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by LudeyKrus »</TD></TR><TR><TD CLASS="quote">If I do it, then i'm gonna be crankin it up to see what's the limits. I'd like to hit around 14psi at the track, and it makes sense to me that it should be able to handle around that much.</TD></TR></TABLE>
if you have money burning a hole in your pocket then sure i would say then push the limits of the motor, maybe you will get lucky,
but my next question is, are you going to be boosting this 14 psi on the stock pistons that have already seen 100k + ort heating and cooling cycles?
i would say if you were runing alll new stock internals, i think even then 14 is pushing it too high. and yes i have seen those dynos of the f22s puting out silly power, but they have different pistons that are stronger than the h series
f22 are 8.8 low compression dished compared to the h23/h22 that have a dome... which brings me to a question = does dished vs domed pistons increase or decrease likelyhood of detonation, other than the fact of the pistons being lower compresion??
i realize that you will have an 9.3:1 cr, but 14 on an h series even at that compresion ratio is going to be too much. but if you plan on doing it, then you better spend a very long time tuning, and have a good fuel managment setup,
if you have money burning a hole in your pocket then sure i would say then push the limits of the motor, maybe you will get lucky,
but my next question is, are you going to be boosting this 14 psi on the stock pistons that have already seen 100k + ort heating and cooling cycles?
i would say if you were runing alll new stock internals, i think even then 14 is pushing it too high. and yes i have seen those dynos of the f22s puting out silly power, but they have different pistons that are stronger than the h series
f22 are 8.8 low compression dished compared to the h23/h22 that have a dome... which brings me to a question = does dished vs domed pistons increase or decrease likelyhood of detonation, other than the fact of the pistons being lower compresion??
i realize that you will have an 9.3:1 cr, but 14 on an h series even at that compresion ratio is going to be too much. but if you plan on doing it, then you better spend a very long time tuning, and have a good fuel managment setup,
01-22-2004, 10:51 AM
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Re: (musclefella)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by musclefella »</TD></TR><TR><TD CLASS="quote"> Firedrake is running 13 psi on stock internals</TD></TR></TABLE>
Last time I heard it was 11psi at the track. I sent him a PM so hopefully he will be in here soon...
Last time I heard it was 11psi at the track. I sent him a PM so hopefully he will be in here soon...
01-22-2004, 01:40 PM
#22
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Ok, let me clarify a few things.
My next car I build is going to be a kind of project... I really like the prelude's style, so I may actually end up keeping it in the end. Right now I am building an H23 VTEC w/ stock H23 rods and H22 pistons, brand new. IF i boost this, it will be a great deal into the future. Since forged H23 rods are pricey, I would like to challenge myself by building a very powerful (comparatively) stock-based motor. I would be using H23 pistons, cryoing the pistons, rods, and crank, shotpeening the rods, and building the whole thing right.
This is all assuming I keep the car, I don't have any sudden financial emergencies between now and the next year, and I don't change my mind.
There are very few powerful preludes out there b/c they're so expensive to build; there's the bolt-on ludes and the all-out ludes. I want to find a nice place in the middle.
My next car I build is going to be a kind of project... I really like the prelude's style, so I may actually end up keeping it in the end. Right now I am building an H23 VTEC w/ stock H23 rods and H22 pistons, brand new. IF i boost this, it will be a great deal into the future. Since forged H23 rods are pricey, I would like to challenge myself by building a very powerful (comparatively) stock-based motor. I would be using H23 pistons, cryoing the pistons, rods, and crank, shotpeening the rods, and building the whole thing right.
This is all assuming I keep the car, I don't have any sudden financial emergencies between now and the next year, and I don't change my mind.
There are very few powerful preludes out there b/c they're so expensive to build; there's the bolt-on ludes and the all-out ludes. I want to find a nice place in the middle.
01-22-2004, 06:12 PM
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Re: (LudeyKrus)
And here I am
It was only 10-11 at the track, and currently that's the boost I've been running daily on 91 pump for about the last year. I'm gonna start building a motor one of these days (if I ever have any time), and once it's ready we'll be turning the boost up to about 14 psi on C16 on this one to see how the stock rings like it......I've had the boost up at 14 psi a couple of times (mis-setting the boost controller) but never for more than a couple WOT runs.....
It's nice to know our cars will make good power even at only 10 psi though......honestly, I wouldn't really want the car making more power as it is. I already can't really get on it in 1st through 3rd without blowing away the tires, and in the rain it's a PITA......the only good more power would do me right now would be at the track, and I never have any free time to get out there (or money to buy new slicks for that matter)
Brian
It was only 10-11 at the track, and currently that's the boost I've been running daily on 91 pump for about the last year. I'm gonna start building a motor one of these days (if I ever have any time), and once it's ready we'll be turning the boost up to about 14 psi on C16 on this one to see how the stock rings like it......I've had the boost up at 14 psi a couple of times (mis-setting the boost controller) but never for more than a couple WOT runs.....
It's nice to know our cars will make good power even at only 10 psi though......honestly, I wouldn't really want the car making more power as it is. I already can't really get on it in 1st through 3rd without blowing away the tires, and in the rain it's a PITA......the only good more power would do me right now would be at the track, and I never have any free time to get out there (or money to buy new slicks for that matter)
Brian
01-23-2004, 02:06 AM
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Re: (Firedrake)
Well i'm gonna find out the hard way, i'm gonna run 10 plus psi and not more then 14 psi max on stock internals.
If it blows then it blows. When i have my Turbo setup complete in March for dragracing over here, i'll try and post a video off it.
If it blows then it blows. When i have my Turbo setup complete in March for dragracing over here, i'll try and post a video off it.
01-23-2004, 10:37 AM
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I just obtained my turbo kit and will be boosting about 7psi on my stock h22 motor. How much timing should I set it back? I'm trying to safeguard the motor for a while till I save up for my build with forged internals.
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