What size exhaust is best for 250 plus HP forced induction

[Irace86.2.0]

For FI I always thought backpressure wasn’t an issue because there is FI, so larger the better was the idea. Size restriction came down to fitment limitations, budget limitations, and desired sound.

[Kolwala]

There is also this exhaust by counterspace garage and mxp:

https://www.counterspacegarage.com/c...tition-exhaust

It's a 2.75 inch exhaust that is supposedly quiet.

[FRS Justin]

2.5 is good at that level no worries in making that goal.

[86TOYO2k17]

Originally Posted by Kolwala

There is also this exhaust by counterspace garage and mxp:

https://www.counterspacegarage.com/c...tition-exhaust

It's a 2.75 inch exhaust that is supposedly quiet.

I’ve got the CSG mxp touring86

Pretty quiet considering aftermarket header and no cats. Good crisp deep tone.

I had same setup but with stock exhaust and it just sounded terrible. The CSG exhaust was same volume maybe even a little quieter but really cleaned up and deepened the tone.

[tyler_win_photo]

Originally Posted by RedRez86

Okay I will not be doing any internals at all. Only injectors and fuel pump would be only other things I might do to add some HP. I Definitely don’t want to mess with internals. Well I don’t want it “quiet” I want it to roar and growl just not be stoned out or so loud I can’t hear myself think inside the care and waking neighbors lol. Maybe Perrin 2.5 catless?

Injectors and fuel pump are unnecessary if you're only planning on using pump gas. They will not net you any more power. The limitation will be the high compression of the engine combined with boost causing knock... which is why many people lower compression when building the bottom end of the fa20 or go with e85 which has a higher knock resistance than 93 or 92 octane.

[RedRez86]

Originally Posted by tyler_win_photo

Injectors and fuel pump are unnecessary if you're only planning on using pump gas. They will not net you any more power. The limitation will be the high compression of the engine combined with boost causing knock... which is why many people lower compression when building the bottom end of the fa20 or go with e85 which has a higher knock resistance than 93 or 92 octane.

So you’re saying if I get better injectors it won’t give me any extra HP? Couldn’t a tune help with the knock and maximize the HP gains after injectors are put it in?


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[CSG Mike]

Originally Posted by RedRez86

So you’re saying if I get better injectors it won’t give me any extra HP? Couldn’t a tune help with the knock and maximize the HP gains after injectors are put it in?


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It will not for your proposed setup.

[tomm.brz]

if you spend time on the tune, you could even use totally stock injector and stock pump (on petrol only of course) with a supercharger hks v2 with 44mm restrictor instead of the 39mm stock... talking about more than 300bhp so listen to CSG Mike, they are useless

[RedRez86]

Originally Posted by tomm.brz

if you spend time on the tune, you could even use totally stock injector and stock pump (on petrol only of course) with a supercharger hks v2 with 44mm restrictor instead of the 39mm stock... talking about more than 300bhp so listen to CSG Mike, they are useless

I was actually looking into the HKS v3 is that power still possible with that? I’m listening bud I’m just asking questions lol. Knowledge is power! Thanks btw fellas. What do you mean by the 44 mm restrictive, Where would I get that. Is that the supercharger Pulley?


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[tomm.brz]

a bit OT, anyway the hks v3 has no restrictor but bigger pulley, no problem using stock fuel system at all
if you put the v2 pulley you could pass 300bhp and you (or the tuner) should tune very good the PI/DI ratio and pay attention to the opening times of the injections and to how close is the end of DI injection to the spark

[RedRez86]

Originally Posted by tomm.brz

a bit OT, anyway the hks v3 has no restrictor but bigger pulley, no problem using stock fuel system at all
if you put the v2 pulley you could pass 300bhp and you (or the tuner) should tune very good the PI/DI ratio and pay attention to the opening times of the injections and to how close is the end of DI injection to the spark

Okay so would you recommend EcuTek to do this accurately or OFT?


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[tomm.brz]

i like to use a Wideband aftermarket sensor to tune FI sothat s why I prefer ecutek

[RedRez86]

Originally Posted by tomm.brz

i like to use a Wideband aftermarket sensor to tune FI sothat s why I prefer ecutek

EcuTek got it. Wide band sensor as in air fuel ratio measurer? Sorry I know about cars but not all the details.


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[tomm.brz]

with racerom v10 you could use a wideband in the open loop and it autocorrects afr based on it, but i meant that you can connect the wideband using a custom map so that you always log the wideband too


i m not aware of a method of this with OFT so with OFT the best would be a dyno tune so that you have also a wideband connected to your car
the stock lambda is pretty inaccurate when you go under 11.5-12