from 11:1 to 12:1 comp. how much gain should i see?
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#9
Originally Posted by Spinmonster
and 20 rwtq.....who said negligable
Compression is the single biggest reason why guys never get the power they read others getting.
Compression is the single biggest reason why guys never get the power they read others getting.
True The rule of thumb is for every one full point increase in compression you will see a horsepower increase of 4%
#10
Yeah, but it also increases the chance of detonation. My friend recently wiped out #7. He was running 59cc AFR's, so the CR was maybe 11.7 to 1. The engine couldn't handle it on pump gas. At least now he's got an iron 408.
#11
That is a tuning issue not what his staic CR was. If you have12:1 static at 8.4-8.7 DCR, it is no more dangerous than a moderate cam at 11:1 which has the same DCR. Static doesnt determine the ability to run pump gas.
Not to mention the other variables of what his quench distance was, combustion chamber carbon deposits and quality of fuel which can cause detonation in a stock motor.
Not to mention the other variables of what his quench distance was, combustion chamber carbon deposits and quality of fuel which can cause detonation in a stock motor.
#12
Originally Posted by Spinmonster
That is a tuning issue not what his staic CR was. If you have12:1 static at 8.4-8.7 DCR, it is no more dangerous than a moderate cam at 11:1 which has the same DCR. Static doesnt determine the ability to run pump gas.
Not to mention the other variables of what his quench distance was, combustion chamber carbon deposits and quality of fuel which can cause detonation in a stock motor.
Not to mention the other variables of what his quench distance was, combustion chamber carbon deposits and quality of fuel which can cause detonation in a stock motor.
#13
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Originally Posted by GOaT Cheese
If increase of comp. is to take advantage of more aggressive compenents that need higher comp., then who knows.
#14
Depends on the combo and the tune, I have seen an 800 hp bbc go from 12.5 to 14 and only gain 2 hp The last motor of mine that was also a bbc went from 11.7 to 12.6 and gain 0 mph (no dyno available) but those are bbc with dome pistons and I think the flame travel was hurt and prevented any real gains. If you have a decent size cam I would say 4% but a small cam detonation will get in the way of any useable power. Unless you are needing the compression to support a large cam or fighting high altitude, the returns are not as good as you might think.. It is all about getting your cranking compression (dcr) right for the elevation where you race and the fuel your using.
#15
Originally Posted by Spinmonster
That is a tuning issue not what his staic CR was. If you have12:1 static at 8.4-8.7 DCR, it is no more dangerous than a moderate cam at 11:1 which has the same DCR. Static doesnt determine the ability to run pump gas.
Not to mention the other variables of what his quench distance was, combustion chamber carbon deposits and quality of fuel which can cause detonation in a stock motor.
Not to mention the other variables of what his quench distance was, combustion chamber carbon deposits and quality of fuel which can cause detonation in a stock motor.
#17
I run 11.75 on 8.65 DCR, .040 quench and TR6 gapped at .040.
94 Octane and no issues.
Still at early tuning stage and 468 rwhp on A4
Static compression is not what we should look at, it is Dynamic and Good DCR will vary with DA as mentionned above.
So it is good to do all research and to understand what works for you in your environment while putting a combo together.
94 Octane and no issues.
Still at early tuning stage and 468 rwhp on A4
Static compression is not what we should look at, it is Dynamic and Good DCR will vary with DA as mentionned above.
So it is good to do all research and to understand what works for you in your environment while putting a combo together.
#18
If you are building a good engine with good heads and cam you will not be able to keep adding compression. Most 12+ to 1 engine I see in Houston don't make good power or detonate a lot and are hard to tune. They don't run good mph either unless they are way light etc. Now with race gas I would certainly add more compression but with 100 degree Houston weather and rush hour traffic etc. I just don't see any good in these high compression deals on the street.
If everythings right and you are running a REALLY big cam you might be able to do it but the heads, cam and intake are there to increase VE not REDUCE it so you can't always add way more compression with a cam simply because it's bigger or the "dcr" numbers would be better. Basically you guys are semi right but there's a definite limit to how far you can go and still be safe on pump gas. I don't go over 11.50 usually even with pretty big cams and have had several 550+ RWHP cars with no detonation problems at all.
When you take apart the 12+ to 1 engines from most shops you start seeing problems related to the compression and the resulting detonation. Remember NHRA and IHRA Pro Stock engine builders couldn't even run much over 12 to 1 at the engine masters competition and these guys were running cams bigger than we are talking about. Several engines were destroyed trying to run that high a compression on pump gas. The overall consensus there was 11.5 to 1 was probably the limit on the engines that weren't turds and made big power. If you CAN run 12.5 to one on pump gas basically your engine has to be a pretty bad combo if it hurts cylinder pressure that much that you can run 12.5 to 1.
If everythings right and you are running a REALLY big cam you might be able to do it but the heads, cam and intake are there to increase VE not REDUCE it so you can't always add way more compression with a cam simply because it's bigger or the "dcr" numbers would be better. Basically you guys are semi right but there's a definite limit to how far you can go and still be safe on pump gas. I don't go over 11.50 usually even with pretty big cams and have had several 550+ RWHP cars with no detonation problems at all.
When you take apart the 12+ to 1 engines from most shops you start seeing problems related to the compression and the resulting detonation. Remember NHRA and IHRA Pro Stock engine builders couldn't even run much over 12 to 1 at the engine masters competition and these guys were running cams bigger than we are talking about. Several engines were destroyed trying to run that high a compression on pump gas. The overall consensus there was 11.5 to 1 was probably the limit on the engines that weren't turds and made big power. If you CAN run 12.5 to one on pump gas basically your engine has to be a pretty bad combo if it hurts cylinder pressure that much that you can run 12.5 to 1.
#19
Originally Posted by racer7088
Remember NHRA and IHRA Pro Stock engine builders couldn't even run much over 12 to 1 at the engine masters competition and these guys were running cams bigger than we are talking about.
#20
These weren't pro stock engines. They are regular engines with production based parts and the LS1 is as good or better than any of them. The LS1 experiences similar VE as does any well tuned engine with great heads and an awsome manifold like the FAST 90mm.
The LS1 is actually banned fom Engine Masters.
The LS1 is actually banned fom Engine Masters.