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Discussion Starter #1
I was told by the guys at Hybrid racing that the K20 engines need a big exaust, at least 2.5 even 3 inch is better. What have you guys heard and what sizes are you using.
 

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I have 2.5 with no muffler no cat.

I am using 2.5 resonator and 3" resonator
 

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prob minimal.

resonators are straight through.

try to muffle the noise a little. instead of complete straight pipe.

Got ticket yesterday for to loud. :lol:
 

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Isn't 3" too big? Has anybody run a 3" yet? If so, did you loose any torque throughout the rev-range?
 

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c_buz said:
Isn't 3" too big? Has anybody run a 3" yet? If so, did you loose any torque throughout the rev-range?

I know that k20eg does, and he said he gained power, but for me thats not the case, I'm going on boost.
 

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acchybrid said:
I was told by the guys at Hybrid racing that the K20 engines need a big exaust, at least 2.5 even 3 inch is better. What have you guys heard and what sizes are you using.
The K-series wants to breath, less back pressure is always better, so 3 inch is not too big.

brian g
 

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so is a 2.5" good to run on the street without losing power or is it best to just cough up the $$ and go 3"?
 

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Exhaust

If you really want to know the best thing to do is get someone with close to the same mods as you but with the two different exhaust setups to post dyno sheets. Other than that mods don't matter if thety can post before and after dyno sheets. One thing to remember is that you may sacrifice some low end power with the larger exhaust making the car a little less wife/girlfriend friendly. Also with dyno charts you can compare power and torque gain across the chart to see what fits your driving style best.
 

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According to K20EG going from 2.5" to 3" back to back dynos gained power everywhere. Thats what he told me. No losses.
 

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power is different from torque... i bet he lost a TON of torque but going that large... you need some backpressure so that the air doesnt tumble over itself and cause even more problems in such a big pipe. i have 2 inch pipe on my 2.8v6 and its more than enough for that to run up to 6k... im sure that a k20a N/A isnt going to be pushing much more air then that. so 2.5" is all you should go unless you just want highend hp and dont want any tq... think of it this way a bus moving .5 mph has a lot of stuff moving at a slow speed so when it hits something its gonna do some damage but if you have a lot of hp and no tq its like a mosquito going 500mph and hitting a piece of tin foil... its not going to do anything.
 

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Dude29662 said:
i bet he lost a TON of torque but going that large
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you need some backpressure so that the air doesnt tumble over itself and cause even more problems in such a big pipe.
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i have 2 inch pipe on my 2.8v6 and its more than enough for that to run up to 6k... im sure that a k20a N/A isnt going to be pushing much more air then that. so 2.5" is all you should go unless you just want highend hp and dont want any tq... .

He hasen't lost a ton of torque he has gained it.
Needing back presssure is a bunch of crap.

Depending on certain factors, going to bigger pipes loses velocity I've read.
 

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Discussion Starter #15
Just because you have a V6 doesnt mean anything. Ive had many H22 powered Hondas and 2.5 inch exhaust would be the biggest for that engine and its a 2.2L compared to the RSX 2.0L. The difference is in the head design. The RSX head just flows a lot better.
 

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Exhaust

As far as needing back pressure being crap. Obviously you are not educated in the dynamics of internal combustion engines. For all out power back pressure is not needed but for most street driven cars that see more than wide open throttle back pressure is neccesary. First the K20A3 and I think the A2 use the Vtec system for EGR as well as power and EGR lowers combustion temperatures to avoid detonation. So a certain amount of backpressure would be necessary, one way to avoid this may be to use water injection to cool the intake charge sufficiently, this is commonly used in turbocharged cars. Besides if you really want power try to tune the exhaust so that the pulses of exhaust gas leaving the cylinder create a low pressure right behind the echaust valve to help scavenge the cylinder.
 

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but the fact ath there is only 2000cc of air that CAN be moved is what i was talking about... i know that it makes no difference if its a v6 or not... you have to balance air flow w/ velocity.... dont go to big or you loose the speed at which the exhuast is coming out and if it slows down to much then it will stop "pulling" the exhaust pulses
 

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Re: Exhaust

JohnR said:
As far as needing back pressure being crap. Obviously you are not educated in the dynamics of internal combustion engines. For all out power back pressure is not needed but for most street driven cars that see more than wide open throttle back pressure is neccesary. First the K20A3 and I think the A2 use the Vtec system for EGR as well as power and EGR lowers combustion temperatures to avoid detonation. So a certain amount of backpressure would be necessary, one way to avoid this may be to use water injection to cool the intake charge sufficiently, this is commonly used in turbocharged cars. Besides if you really want power try to tune the exhaust so that the pulses of exhaust gas leaving the cylinder create a low pressure right behind the echaust valve to help scavenge the cylinder.

John R we were always talking about performance.

k20a2 egr my ass.

k20a3 has egr.
 
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