moparmatt19
Well-Known Member
Kinda a general question on the HP and TQ gain from 10.1 comp to 11.1 comp. How much will it really gain? Based on Iron headed sb.
HP & TQ difference between 10.1 comp to 11.1 comp?
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Probably less than 3%.
Agreed. Though a general question nets a general answer. The percent gain is not what someone should be after but they should be after the correct ratio to properly match the cam for a good operating engine.
moparmatt19
Well-Known Member
Agree also... Reason saying or asking is bc if there is not much more difference then why run 11.1-12.1 and need race fuel instead of running 10.1 and cheaper gas? Or is there really a noticeable difference? Let's say for a base to answer the question, using a camshaft like 255-265 dur @ .050 with LSA from 106-108.. Both can be run on pump or race fuel depending on setup. But why make it have to run on race fuel if your really not getting that much gain??? See where im getting at? Just seeing the Truth about all this hype on compression
EL5DEMON340
Well-Known Member
When I went from 10.2 to 11.2 it was noticeable. Idled better, quicker starts and better cold idle, torque, very slight increase in MPG, sounded a lot better.. Way nicer POP out the tips.
EL5DEMON340
Well-Known Member
With that size cam in a sb., the 11.2 engine running pump or race will be quicker in the quarter mile all things being equal. You need to tailor your cranking psi to cam not really the 9 10 or 11 to 1 number because it really is just a number. A good cam company should be able to recommend the right cam for the piston/head/stroke combo
fratzog lover
Well-Known Member
Probably not enough in your opinion to give up the pump gas drivability.
I bet the ratio increase better matched the cam and intended usage.
stroked340
Well-Known Member
I agree my 11.5 to 1 416 sounded like an beast my 10.5 to 1 360 not so much..i run them both on 93 octane no problem,mixing in some 110 at the track..
mderoy340
Well-Known Member
Static compression is just a number. To build a motor to make good power and run on pump gas you need a 7.5 - 8.5 dynamic compression ratio. More cam duration, Later intake valve closing event requires more static compression to reach your desired dynamic compression goal.
I don't see why people push the limits on a street engine especially if your a novice. It's not really worth pushing over 9:1unless your cam choice requires more. But for a race engine winning cost money, once you go passed your basic high rise, cam and headers performance becomes more and more expensive with less and less gains. If your running 15-20 hp less than everyone else your not gonna do so well.
Rusty, I'very stated before most of my knowledge is more from reading (a lot of reading) than real life experience
Cars I've done before mainly been a few bolt on like high rise cam, headers, and from my cousin late model and uncle top alcohol and a lot of hot engines my other uncle has built for various people around town.
If my info is misguided advice how so??
I see a lot of people on this forum that build High compression engine to only later try to figure how to get them to run on pump gas that's why I said the 9:1 comment. And the race comment is of course depending on the situation but if you have to detune your engine compared to the other guys to run pump gas more than likely your probably not gonna be as competitive.
Cars I've done before mainly been a few bolt on like high rise cam, headers, and from my cousin late model and uncle top alcohol and a lot of hot engines my other uncle has built for various people around town.
If my info is misguided advice how so??
I see a lot of people on this forum that build High compression engine to only later try to figure how to get them to run on pump gas that's why I said the 9:1 comment. And the race comment is of course depending on the situation but if you have to detune your engine compared to the other guys to run pump gas more than likely your probably not gonna be as competitive.
I guess I was a little confused by your post I get you now
No problem! I confuse myself all the time.
People see all these fancy magazine articles and stories on forums about high compression and pump gas and don't realize it takes lots of experience and money to do it right.
Plus, even when done "right" there's still a very real possibility that it will not like pump gas on certain occasions. Hot outside temps coupled with high humidity sittin in traffic a long time. Or in a truck pulling loads.
People do things without using their own head. If you look back at history, anything over 9:1 compression required premium fuel. And I mean back in the 60s to the early 70s.
One example comes to mind, because a neighbor had it where I grew up as a kid. It was a 1971 LT1 Camaro. 9.2:1. It was totally all original. Had "PREMIUM FUEL ONLY" right on the sun visor and on the gas filler door. Premium fuel. In 1971. That was at or over 100 octane and LEADED.
Would it run on 87? Sure. Until it got good and HOT on a hot day and then it would knock and ping like all hell. Without expensive building techniques like quench or aluminum heads, around 9:1 is indeed the limit on pump gas. Course you can cheat some by running a "big" cam, but then, what's the point? You just lost cylinder pressure. It will be more efficient with 8.5:1 and a matching cam to give optimum cylinder pressure. We are after all talking about a street engine.
No matter how much you talk to some people, they will just not believe an engine can be powerful under 10:1 compression and it just ain't true.
Rusty, that would require the concept of learning. We have a bunch of guys my age, went off the deep end with 13-14 to 1 compression STREET combos(mostly driven, on the street...). After 4 years at 10-12 dollars a gallon, they finally unloaded the race engine cars. The cars did go 9:90 10- teens, who could afford it? Good headwork & camshaft matching/ chassis & power train setup/ attention do details, counts...
Yup and I know people will argue "as long as you keep DNC under blah blah blah..." but again, that requires a learning curve most beginners don't have. Besides all that, it's just a safe bet to build a lower compression engine anyway. Especially with this crap ethanol in the gas.
Yes, upping the compression will net you more power. How much is hard to say, I know Wallace has a calculator for that...along with a calculator for just about anything else under the sun.
http://www.wallaceracing.com/Calculators.htm
How many licks does it take to get to the center of a tootsie pop???, HANG ON, let me check Wallace racing for a calculator!
Seriously though, if you want to run 12:1 and don't like race gas prices, why not convert to e85? If you drive your car a fair amount it will pay for it self in about a year in gas savings alone...just a thought.
http://www.wallaceracing.com/Calculators.htm
How many licks does it take to get to the center of a tootsie pop???, HANG ON, let me check Wallace racing for a calculator!
Seriously though, if you want to run 12:1 and don't like race gas prices, why not convert to e85? If you drive your car a fair amount it will pay for it self in about a year in gas savings alone...just a thought.
stroked340
Well-Known Member
I think this cannot be answered generally. Not enough info in the question asked. That is like saying, how much weight would be gained if someone ate pizza a day? Well, how much? Some athletes eat 6000 calories a day and never gain! Some people just LOOK at a pizza and they gain... Can't answer the question....
roccodart440
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With nothing else changing you might not see much. Both of my 440's were a static 10.5:1. Both ran/run on 92+ pump swill.
IF you up compression the cam needs to be adjusted to that new compression as well as other items if needed. Look at the compression ratios in modern performance engines. They aren't low.
N/A
2015 Camaro 11:1
Challenger 10.9:1
S2000 11.1:1
GT350 10.3:1
Boosted
Hellcat 9.5:1
GT500 9:1
IF you up compression the cam needs to be adjusted to that new compression as well as other items if needed. Look at the compression ratios in modern performance engines. They aren't low.
N/A
2015 Camaro 11:1
Challenger 10.9:1
S2000 11.1:1
GT350 10.3:1
Boosted
Hellcat 9.5:1
GT500 9:1
EL5DEMON340
Well-Known Member
Correct. When these post come up I usually chime in and say you can run 11 to one on pump in my case i have 93. But I'm usually quick to point out why my engine runs good on 11.2. Build the engine with running hi comp in mind, smoothed any sharp edges on piston, polished exhaust port, blocked heat crossover, phenolic spacer under carb, electric fuel pump with insulated lines under hood, fresh air Intake ( very important), very cold plugs with MSD, carefull timing and reading of plugs, 4,400 rpm 9.5" stall converter, 3.55 or 3.91 gear, and in a lighter car. Now I have gone with a 6 pack so I don't have the ram air and that intake and carbs hold more heat!!! You really have to nail the plug heat range, that plug is sticking out in the chamber and that is usually going to be the cause of the heat source for detonation and preignition.
Nor are they comparable to dinosaur engines with no quench, no squish, no EFI and nothing else to aid in combating detonation. Bad comparison.
Generally,
In a Medium-Performance Small Block, putting out 275 HP at the Flywheel.
By going from 10.0-1 to 11.0-1 {an increase in 1.0 Compression}, you will improve
the Thermal Efficiency and gain generally 3.6% to 4% in Horsepower.
Approximately 11 Horsepower.
Torque will be increased by 5%.
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