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Bigger Exhaust = More Boost?

cosworth1971
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cosworth1971 Community Regular

cosworth1971

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Posted

still having some issue with my 96 gtst r33 skyline.

Basicaly i have a Blitz 3" full exhaust with big down pipe and decent size Fmic, the exhaust came with a bolt in restrictor,silencer for the end of the exhaust as a option to run.

With the restricter in my car gets to a solid 9-10psi and is basically a missile(never hitting boost cut).

However i like the loud of the system without this restictor/silencer installed on the end, but my car then boost to 10-12psi then just hits boost cut? which is why its annoying me.

The question is , does this sound normal ?and is it normal for big exhaust to make more boost?.

would a r32 7psi actuator be the answer?.

I dont really want big boost yet as im saving for a power fc.

I have fuel cut defender but dont know how to adjust it/install.

Im thinking of trying a 2.5" restrictor plate in exhaust, this silencer is ugly hehe.

Is there ways to keep/get boost low?

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cosworth1971 Community Regular

cosworth1971

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with the restrictor in it boosts as you want and is quieter, win win?

Yeah its not bad quiet but would like it louder without the restrictor.

What are the good cheap option ecu's? would like a power fc but how do the cheaper piggy back ecu's perform?

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AngryRB Grand Master

AngryRB

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Posted (edited)

maybe your stock turbo's wastgate has reached its limits , it might not be able to vent off any more at the top end so its spiking..

if this is true then your on the edge of needing a hiflow/turbo upgrade

as a cheap alternative you could take the turbo off, remove the exhaust housing , take it to turbo shop and tell them to hone out the wastegate area and fit a larger flapper.. ( XR6 turbo flapper was used on my old turbo)

then your boost should be whatever the spring is..

Edited by SliverS2
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WMDC35 Experienced

WMDC35

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Yeah its not bad quiet but would like it louder without the restrictor.

What are the good cheap option ecu's? would like a power fc but how do the cheaper piggy back ecu's perform?

it's hard to do good & cheap with ecus, nistune prob most eco, link g4 is good ,does boost control & doesn't need z32 afm so in the long run not too bad if you're going to go further, there's a few reputable tuners on here so see who's in your area and they'll be able to recommend for your goals

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cosworth1971 Community Regular

cosworth1971

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maybe your stock turbo's wastgate has reached its limits , it might not be able to vent off any more at the top end so its spiking..

if this is true then your on the edge of needing a hiflow/turbo upgrade

as a cheap alternative you could take the turbo off, remove the exhaust housing , take it to turbo shop and tell them to hone out the wastegate area and fit a larger flapper.. ( XR6 turbo flapper was used on my old turbo)

then your boost should be whatever the spring is..

i did think this with boost creep but how common is this senario?

I mean my car is std except pod,bigger fmic and big exhaust.

I think i need to make sure its a 5psi actuator?as it may have a 10psi one.

about the std r33 dont they get to 7psi? not 5psi

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cosworth1971 Community Regular

cosworth1971

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it's hard to do good & cheap with ecus, nistune prob most eco, link g4 is good ,does boost control & doesn't need z32 afm so in the long run not too bad if you're going to go further, there's a few reputable tuners on here so see who's in your area and they'll be able to recommend for your goals

thanks

what of wolf ecu? or greddy ecu?

Im seeing them cheap atm.

I did think nistune but is it just plug and play?like swappng a pc graphics card? basic tune on it? diy it? until i can save for tunes

sorry still a noob with skylines obviously hehe

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GTSBoy Grand Master

GTSBoy

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i did think this with boost creep but how common is this senario?

I mean my car is std except pod,bigger fmic and big exhaust.

I think i need to make sure its a 5psi actuator?as it may have a 10psi one.

about the std r33 dont they get to 7psi? not 5psi

If you had an R32 actuator on it you would always have had at least 10 psi boost. Seeing as you used to have 9-10, then it IS possible that your actuator is not a 5psi one.

My suggestion. Put the silencer in, and don't worry about having a louder exhaust until you can afford the management issue. Noise is just fashion, and fashion is for wankers. The only thing that is really important is how well shit works.

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OEM_as_f*ck Apprentice

OEM_as_f*ck

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5psi till 4500 rpm then 7psi. If you ground one of the cables then you can mod it to run 7psi constant =)

He just said before that he has a straight vacuum hose from the pressure source to the wastegate actuator. So he doesnt have any wires to ground. Also, he wants to lower the boost, not increase it.

The stock wastegate should be fine with those mods, and a little gate creep is normal. You don't need a bigger wastegate flap, a new ECU or a high flowed turbo. And you shouldn't need to run a stupid f**king restrictor in the exhaust. Your just painting over dirt.

I'm willing to bet it has a bigger actuator fitted, just go and fit the original actuator back onto it and your problems will be solved.

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