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hahahahahahaah

any restriction would be the wrong wording ... every thing has a restriction, the consistence of exhaust flow is what changes spool times...
also there's a whole host of other reason why outlaw class drag cars run turbos the way they do. And none of them have to do with a optima.

Unconstipate the exhaust flow to, through, and away from the turbine housing outlet, and the boost onset will improve. i.e., you'll get into boost sooner [onset threshhold], and get to a higher boost level faster, if you lower (not eliminate) the backpressure in the exhaust post turbo.

A larger downpipe/exhaust will net you a SLOWER spool, not quicker (mainly a larger downpipe). It will however boost more on top in since you are freeing up the restrictions. It is kind of a trade off when doing larger exhaust. You trade some low end for more top end HP.

Same concept when doing a custom intake manifold and changing the size of the intake runners.
 

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Asher I've been wanting to do that for a while, any pics of the placement?
i'm afraid not sir. :/

Asher-- you have any sound clips of your set up?
no, but you're welcome to come to the SanAntonio meet next month and hear it in person.


A larger downpipe/exhaust will net you a SLOWER spool, not quicker (mainly a larger downpipe). It will however boost more on top in since you are freeing up the restrictions. It is kind of a trade off when doing larger exhaust. You trade some low end for more top end HP.

Same concept when doing a custom intake manifold and changing the size of the intake runners.
You're right about the exhaust diameter having an effect on the powerband, but the turbine housing itself is the most decisive factor in how quickly a turbo will spool up when coupled to a mechanical wastegate (boo Optima!) What do you mean when you say "...boost more up top?" Our mild turbos are so small that there is no "up top" and are gasping for air in the upper RPMs.

As i'm sure you already know, engines output their exhaust in the form of a pulse and since the turbocharger almost negates (i said almost; not entirely) the need for an efficient pipe since the turbine wheel intercepts that pulse. It's more important for the 2.4L guys to correctly choose the diameter of their exhaust piping so it will perform well in relation to exhaust velocity which i believe is what everyone confuses for backpressure. Once compressed air comes into the mix with an engine, exhaust tuning has much less to do with making power. So what if you can milk another 3-5 hp out of a car with a tuned exhaust... the benefits of making an engine sustain an insane final compression ratio (boosted air x compression in the combustion chamber) has much more effect on making power if you can just get rid of the extra gasses it produces. Bigger is almost always better on a turbo setup. The only place where it isn't good is on the exhaust wheel where too big can = no chance of spooling your oversized turbo any time this year.

-asher
 

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^^ oh that's all i have to do?? Lol. Might be easier for the sound clip lol
 

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i'm afraid not sir. :/

no, but you're welcome to come to the SanAntonio meet next month and hear it in person. :)


You're right about the exhaust diameter having an effect on the powerband, but the turbine housing itself is the most decisive factor in how quickly a turbo will spool up when coupled to a mechanical wastegate (boo Optima!) What do you mean when you say "...boost more up top?" Our mild turbos are so small that there is no "up top" and are gasping for air in the upper RPMs.

As i'm sure you already know, engines output their exhaust in the form of a pulse and since the turbocharger almost negates (i said almost; not entirely) the need for an efficient pipe since the turbine wheel intercepts that pulse. It's more important for the 2.4L guys to correctly choose the diameter of their exhaust piping so it will perform well in relation to exhaust velocity which i believe is what everyone confuses for backpressure. Once compressed air comes into the mix with an engine, exhaust tuning has much less to do with making power. So what if you can milk another 3-5 hp out of a car with a tuned exhaust... the benefits of making an engine sustain an insane final compression ratio (boosted air x compression in the combustion chamber) has much more effect on making power if you can just get rid of the extra gasses it produces. Bigger is almost always better on a turbo setup. The only place where it isn't good is on the exhaust wheel where too big can = no chance of spooling your oversized turbo any time this year.

-asher
Didn't meant o use the word "boost more up top". Just meant to say more top end power.

And yes Turbo size plays a huge role on spool (which is why manufactures dont put something like a 28rs on)... But we were talking about exhaust itself. I replied to someones mention about exhaust size making a car spool faster.

However, I do hit 30lbs of boost by 3300 RPM with my GT3076 turbo :)
 

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wasnt the old rule of thumb 2-2.5' for all motor 3' if you pushing some power?

However, I do hit 30lbs of boost by 3300 RPM with my GT3076 turbo <-- in what car? im so partial to t3/t4 hybrids **** you honda
 

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wasnt the old rule of thumb 2-2.5' for all motor 3' if you pushing some power?

However, I do hit 30lbs of boost by 3300 RPM with my GT3076 turbo <-- in what car? im so partial to t3/t4 hybrids **** you honda
2.0L stroker audi a4. all tuning done by me with Maestro software. Check out my garage.
 

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I know it's an old post, but my ex straight piped my EX. It's stupid loud and not worth it... and I've owned all sorts of moded civics.
You can hear it with the windows up through my phone and through the walls up of my 3rd floor apartment.
 
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