So what kinda compression is everyone running and what power adder??

 

11 to 1 with a 150 shot nitrous 383. Nitrous loves compression

9 to 1 with a twin turbo 401 running straight 93 pump gas. ~9:1 is great for a pump gas street mill goin under boost

 

im gonna be 9.7:1 with a single turbo t-76

 

15:1 with a 250hp hit

 

i had some guy throw that question at me the other day when i told him about my build and the hp I'm hoping to get. compression doesnt equal hp right? am i missing something? I'm hoping to see 460hp (with out nos) out of my build and my compression (according to the machine shop) should be about 10:1 i dont mean to intrude in your thread just got me wondering now.

 

Its more like 8:1 with a 500 shot!!!

My 92 is setup at 9:1 (AFR 210's) with a D1SC running 10lbs (for now)

 

11.0-11.5:1
2 100 shots.

 

high compression is good for high horsepower non turbo or supercharger motor but can somethimes handle alil shot of nitros when built rite. low compression is good for turbo/ supercharged big nitros shot motors make sure you look into what your buying and what your trying to build.

and 9:1 B&M supercharged chevy 350 bored 40 over with forged pistons, ballanced stock crank, stock heads with port and pollish job with BIG valves, hooker headers, nitto drag dot tires "i handed a stock i think 2001 corvette z06 his *** tonite" rite out of the hole by a car length after that all over for him

 

you wont see many low compression purpose built nitrous motors.

 

8.5:1 single turbo 350, 93 octane, and 12psi so far.

 

Way too much, as the potential for them is at a much higher boost level, and with that much compression, your really leaving a lot on the table. If your set on 9.7:1 and a T-76 though, at least consider a TC76, as it will at least spool faster for you so that you can enjoy it....

 

8.5 24psi pump gas w/a intercooler procharger F2

 

You know nothing, But I'd have no problem embarrasssing you in a few weeks with the 500 shot. (Actually, I wouldn't need the gas.....lol)

 

im open to suggestions.. i have the engine in the machine shop now.. just for a good cleaning and cam bearings.. the only reason i was gonna stick with that compression is because its what i have as of now.. i've been looking at diamond pistons.. to drop me down to 9.0:1 ... i thought about useing a thicker head gasket to drop it more.. im just really missing my car and wanting to get it back on the road...lol

 

11.5:1 with a 200 shot was last smallblock. Pump gas ran good but VP113 was worth 2 tenths and 2 mph at the track.

With a 200 shot I ran VP113.

New motor is going to be 10:1 with probably 8 PSI to start.

As far as compression and power adders, its all relative to how hard you want to push the limits. A max effort big block might run great at 16:1 but a lot of nitrous builders would drop it down to 14:1 for multiple kits. Turbo setups aren't running ultra low numbers either.

Considering the owner isn't going max effort racing, there is no reason 9.7:1 is out of the question. Good piston and high octave as key ingredients to making it live anyways. Running the ragged edge of timing and tune is for people with deep pockets.

 

Remember that increasing compression doesn't raise the quantity of the air and fuel in the cylinder, it just squeezes it more during quench, which is great for a naturally aspirated engine. You'll always make more power with a turbo though by lowering your compression level, because although your giving up max power by dropping static compression by a point or two, the potential for the increased oxygen that you can run becomes very substantial, and that is where your power is, because more air will allow you to burn more fuel....

 

false . raising compression on turbo cars will always make more power. Take a
look at some of these turbo size limited drag racing classes .You`ll find compression in the 11+:1 ratio.

 

yeah ill be happy hitting mid 10's with a good tune...

 

That is completely wrong, as adiabatic compression becomes a very important factor at such a drastic increase in static compression levels making the overall benefit of the turbo becoming much less efficient. You will always make more power with a turbo at lower compression levels with a given octane because it will allow you to max the turbo, and increased oxygen will outweigh adiabatic pressure because it allows you to burn more fuel, which of course equates to more calculated horsepower. By the way, what kind of help would anyone be looking to give to someone suggesting such an increase in static compression in conjunction with an even higher increase in octane requirement, for a street driven vehicle, especially when 91 octane alone will be reaching close to $5.00 a gallon by this summer? Incidently, Top Fuelers run 90% nitromethane at around 6.0:1 static compression and are the fastest in the world, so it isn't having a higher static compression level per se that gives you power, power is in the type of fuel that is being used, and going with a compression level that is best suited for it....

 

lets say we have a turbocharged 406 and it makes 650hp.We than take the same engine setup and just increase the compression , will it make more than 650hp (same boost level)???

Imo a turbo street or drag car should not have less than 9.5:1 . if gas cost/mileage is a concern than hotrodding cars is not for you.

 

I'm under the impression that you would be after a 8:1 to 8.5:1 dynamic compression ratio. This would depend on the cam that you are choosing to have in the engine. The dynamic compression calculators i've seen have where you can enter the boost in to get the final ratio.

 

i remember chris tuten talking about when he had 9:1 compression. he got it back up to 10.5:1 or whatever it was, and the car ran better.
"on a good weather day the low compression ran good"
"on a bad weather day the low compression ran bad"
"the high compression runs good everyday"

 

IMO, always use as high compression as you can get away with for the fuel you plan on using

 

I'm running 10.5:1 with just a 200 shot.

 

The calculation is; (boost PSI / 14.7 + 1) * static compression = effective compression. A drop of a point in static compression from 9.5:1 to 8.5:1 is about a 3% loss in power, give or take a little, and let's just say theoretically your engine is making 500-HP with 9.5:1 static compression and 11.7-psi of boost, with your targeted effective compression ratio being 17:1 for the octane your currently running. Using both a 9.5:1 and 8.5:1 static compression ratio comparison, this is how it will break down....

11.7-psi / 14.7 + 1 * 9.5:1 = 17.06 effective compression
14.7-psi / 14.7 + 1 * 8.5:1 = 17.00 effective compression

We dropped 3% (15) decrease in power reducing static compression by a point from 9.5:1 to 8.5:1, but are now able to run much more boost to equal the same 17:1 targeted effective compression. Now, for every pound of boost, we're adding approximately 6.802% of additional air and fuel to burn, and since our 17:1 effective compression ratio target allows us to run 3 more psi of boost by lowering static compression by one full point, we're looking at a 20% increase in power. But then we need to take into account the initial 3% loss from the compression drop, so it's really a 17% (82.45) increase in power, but a substantial increase nonetheless, while maintaining the same 17:1 ECR....

500-HP w/11.7-psi and 17.06 effective compression....
567-HP w/14.7-psi and 17.00 effective compression....

567-HP was calculated by using our starting 500-HP engine, losing 3% (15) by dropping a point in static compression (485), then adding our 17% increase (82.45) in power....

 

forced induction does not change compression ratio. therefore effective compression ratio is just a meaningless formula.

run both engines with the same boost and you will the find the engine with more compression will make more power .

 

Obviously you are clueless when it comes to increased boost pressure in conjunction with the mandatory higher octane needed to avoid detonation, not to mention the timing related issues associated with increasing static compression along with increased boost. So far, your logic has been completely flawed, and you keep insinuating that it would be much more beneficial for him to run as much static compression as possible with as much boost as he wants, which is ridiculous because the engine simply won't last too long that way. Not one of your exaggerated claims have yet to be proven feasible, let alone factual, for a street driven vehicle. As for effective compression being meaningless, prove it, factually....

 

As for this, why don't you do the calculation as opposed to asking someone else to do it for you. But for the sake of argument, I'll do it. If your asking to run both engines at the same boost level, in this case, 14.7-psi, then the effective compression ratio for the 9.5:1 engine no longer remains at 17:1, it jumps to 19:1, which completely defeats the purpose of the whole entire point, because the target was obviously 17:1....

 

9.0:1 on a 383lt1 with novi2000 supercharger