So what kinda compression is everyone running and what power adder??
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So what kinda compression is everyone running and what power adder??
So what kinda compression is everyone running and what power adder??
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Re: So what kinda compression is everyone running and what power adder??
im gonna be 9.7:1 with a single turbo t-76
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Re: So what kinda compression is everyone running and what power adder??
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.
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Re: So what kinda compression is everyone running and what power adder??
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.
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
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Re: So what kinda compression is everyone running and what power adder??
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.
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Re: So what kinda compression is everyone running and what power adder??
8.5:1 single turbo 350, 93 octane, and 12psi so far.
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Re: So what kinda compression is everyone running and what power adder??
Originally Posted by scamaro355
im gonna be 9.7:1 with a single turbo t-76....
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Re: So what kinda compression is everyone running and what power adder??
8.5 24psi pump gas w/a intercooler procharger F2
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Re: So what kinda compression is everyone running and what power adder??
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....
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
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Engine: Vortec 4200 Inline 6 PT70 Turbo..
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Re: So what kinda compression is everyone running and what power adder??
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.
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.
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Re: So what kinda compression is everyone running and what power adder??
Originally Posted by scamaro355
im open to suggestions....
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Re: So what kinda compression is everyone running and what power adder??
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....
look at some of these turbo size limited drag racing classes .You`ll find compression in the 11+:1 ratio.
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Re: So what kinda compression is everyone running and what power adder??
yeah ill be happy hitting mid 10's with a good tune...
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Re: So what kinda compression is everyone running and what power adder??
Originally Posted by daverr
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....
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Re: So what kinda compression is everyone running and what power adder??
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....
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.
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Re: So what kinda compression is everyone running and what power adder??
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.
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Re: So what kinda compression is everyone running and what power adder??
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"
"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"
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Re: So what kinda compression is everyone running and what power adder??
I'm running 10.5:1 with just a 200 shot.
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Re: So what kinda compression is everyone running and what power adder??
Originally Posted by windowrattler
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....
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....
Last edited by Street Lethal; 03-13-2011 at 04:11 PM.
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Re: So what kinda compression is everyone running and what power adder??
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 .
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
14.7-psi / 14.7 + 1 * 8.5:1 = 17.00 effective compression
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Re: So what kinda compression is everyone running and what power adder??
Originally Posted by daverr
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.
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Re: So what kinda compression is everyone running and what power adder??
Originally Posted by daverr
run both engines with the same boost and you will the find the engine with more compression will make more power....
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