Intercooler piping

Points
57
Location
England
Car
celica gt4 st205
Hi I'm just wanting a second opinion on the sizing of my intercooler piping.

Basically from the turbo it is ~43mm internal to ~53mm external, then the intercooler is 68mm external, then the throttle body inlet is ~72mm internal - its a rubber flange type thing so a metal pipe will have to go inside it, its the wrong shape to have anything on the outside.

So out of the turbo it is into a 45 bend then down to two 90 bends, both of these are step ups, 51mm to 63mm and then 63mm to 70mm, then another 45 bend to bring it inline with the intercooler.

After the intercooler theres a 90 bend that goes from 70mm to 76mm and then two 45 bends to bring it inline with the throttle body, then there is a step down to 70mm for the throttle body.


I'm just wondering if I've gone down the right route having the step ups on each 90 bend? I was just thinking it would be a little less restrictive than a normal bend due to a slightly larger diameter.

Also the section after the intercooler where it goes up to 76mm then back down, is that a waste of time or not? I was just thinking again with a bigger diameter hose it would be slightly less restrictive for the bends but I'm thinking 76mm is too big.

I will be running 15-16 PSI in a 2L to give you an idea of flow, any help would be appreciated, cheers. :)
 
Avoid steps where possible and try and use cone shapes to increase or decrease the size of a intercooler pipe.

The bend is a good point to change size.

Interestingly air flows faster through narrow pipes. So larger pipes increase capacity potential but do not actually increase the rate of flow so in some cases you can lose a bit of power with larger pipes (exhaust or intake are typical areas for this phenomena).
 
Increasing the exhaust diameter at the turbo outlet will increase power over the stock system every time as the only restriction in any turbo powered vehicle should be is the turbine housing itself.

Silicone reducer bends are available and I would only alter the size ( step up or down in diameter) of the pipework at the Intercooler and the TB if needed
 
Avoid steps where possible and try and use cone shapes to increase or decrease the size of a intercooler pipe.

The bend is a good point to change size.

Interestingly air flows faster through narrow pipes. So larger pipes increase capacity potential but do not actually increase the rate of flow so in some cases you can lose a bit of power with larger pipes (exhaust or intake are typical areas for this phenomena).



The steps I am using are all silicone and they are never any more than 10mm each so they are very smooth and gradual.

Basically now my only concern is after the intercooler where it jumps up from 70mm to 76mm then back down to 70mm for the throttle body, is that just going to make me loose power? it steps up to 76mm on a 90 bend then stays at 76mm through two 45 bends then steps down to 70mm with a very gradual straight reducing coupler before entering the throttle body.
 
Increasing the exhaust diameter at the turbo outlet will increase power over the stock system every time as the only restriction in any turbo powered vehicle should be is the turbine housing itself.

Silicone reducer bends are available and I would only alter the size ( step up or down in diameter) of the pipework at the Intercooler and the TB if needed


I'm not doing too much on the exhaust other than 3 inch downpipe and front pipe, I am using silicone bend reducers just obviously flipped to step it up, I did think of only stepping it up just before it is needed, i.e. before the intercooler but I am just thinking increasing the size on the exit of a 90 bend might just cut down on the turbulence created by the bend, the two increases in size to get from the turbo to the intercooler aren't too far away from the intercooler inlet so I would think they aren't too bad ... although I could obviously be wrong.
 
the power you are running will determine the correct intercooler set up.they should be matched - you can go too large . remember a larger ic may enable you to run more power but it will also give more lag .
 
Yeah I understand and the intercooler itself is fairly small I've not just gone bigger is better with that it is well sized.
I'm just wondering with the piping is it just possible that a bigger diameter corner the slower moving air would create slightly less turbulance and therefore not impact the power too much as oppose to having a corner that is perfectly sized to have the air travelling at the right speed, however, that is the air travelling straight line not a around corner.

Yes it will mean a bit more lag but at the end of the day the throttle body inlet is 70mm and I don't want to have a pipe smaller than that then have to step it up.
I'm just thinking the small amount of added lag may be worth a lower resistance through each corner
 
I don't think that there will be any noticeable difference as you may be overthinking it as to what is best , large pipe volume and slower airspeed vs small pipe higher airspeed :)
 
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Again it depends on your power - if it stock then honestly it will make no difference. Also do you have a front mount because if not you really are wasting your time even thinking about pipe sizes.
I have an n spec series 3 caldina which has the later ST246 3gse turbo engine . it has exhaust induction and a chipped ecu and the stock intercooler set up is perfectly adequate for close to 300bhp.
 
It's not stock, but at the same time it's not massively modified, sort of 4/5 psi boost above standard, modified intake and exhaust and rebuilt turbo with billet impeller.

Yeah hahaha it's front mount.

I think people say for the modifications I've done in this car people usually get around 280-320 bhp ish, but obviously without a Dyno on mine those numbers are kind of pointless
 
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