2.5" Inlet and 3" outlet for Intercooler?

[Z2TT]

Hello.

I noticed that a Saber Intercooler kit I think it was for a 1jz Soarer had 2.5" Inlet and a 3" outlet pipe. Just wondering why the inlet/outlet pipes are different size, and is there any benefit from that?

Anybody run different sized cooler piping on their 1jz and does it help?

Thanks.

[88FOUR]

I have 2 inch from the turbo, flars out to 2.5 inch at the intercooler, then 2.5 inch out, flaring out to 3 inch about 40cms from the throttle body and I like the way it drives.... going from a 2inch turbo out let to a 3 inch throttle body you would have to have different sized piping... on a 3sgte that is but cant see how it would be different.

[jonathan yee]

funny, sometimes i've seen smaller after the IC to keep flow up as the air has cooled down and less volume.

[88FOUR]

makes sense that does....

.... then why is a turbo outlet so much smaller then the throttle body?

[Z2TT]

Pretty sure it was 2.5" inlet and 3" outlet, or maybe it could have been the other way around.

Anyway would it be a good idea to have different sized inlet/outlet pipes when say making your own setup?

[Z2TT]

Then again I have seen setups the opposite way, People saying that since the intercooler causes pressure drop, to use a smaller pipe after the cooler.

Thanks.

[celicapain]

In the real world makes no difference, the reasoning behind a larger ID outlet on an intercooler is because of that pressure/temp relationship. People figure that if you increase the id of the piping after the core you get a greater pressure differential between the inlet and exhaust of the intercooler and hence a larger temprature drop. though in the world whatever plumbs in easier- i know there is a s4 audi making 300+kw at the wheels running 2" plumbing all the way to the throttle body so dont blow it up to be more imprtant than it is. my 2 cents.

[Z2TT]

Well I remember reading on MRT's website that in one of the customers cars using slightly smaller intercooler piping made better power.

[jonathan yee]

i guess the piping dia realy needs to be balanced for the engf/turbo combo. smaller capacity eng's and turbo you'd want smaller pipes as you want to keep flow up as much as possible and goin too big in the pipe creates more turbulance/less flow.

but then if you had 2in piping all the way for a big gt40r on a 6/8cyl then you'd prob be restricted esp in the higher rpm...

but yeh most setup's i've seen and for road cars people always go bigger than what they need and think the bigger the better. 3in is too big i think for most apps esp as most tb's aren't 75mm.

[celicapain]

Providing you keep the cooler piping bigger than the id of the compressor outlet it should be cool. thats said i run 2.5" if i had done it again would have gone for just 2", would have been heaps easier to plumb and interesting to see if it restricted power.
If you look at the top level racing stuff, either turbo F1 or the gt300/gt500 jap tourers youll notice they all run a small (around compressor id) pipe into the cooler, then a fat 3" out, so maybe there is something to it. "but these guys spend billions for bees dicks"

[auto351]

Looking at this question, I agree with some of the guys (celicapain),, but the larger the pipe work diameter the better and this is because of the pressure drop thought the system will be less, the formula pressure = Air flow * Pipe resistance,
If your running 12PSI at the engine and you have a 10PSI loss across the system them your total turbo pressure will be 22PSI, I’ve hear numbers like 100degress Celsius temp increases for every 10PSI boast (not sure if that’s exact but we can use this for our example)
If our pressure losses are only 5 PSI (due to large pipe work) then this would reduce the air temp by 50degress to start, so large piping would give lower running temp

If pressure increases causes an increases in temp then the reveres is true a pressure drop will reduce the temp, so with a correctly sized pipe work (outlet large diameter) we can get some free cooling with the outlet pressure drop of the intercooler.

The only problems I can see with large diameter pipe work is taking up more room under the bonnet, cost more $$$ & more important it would increase the turbo lag as the larger pipe work now needs to be pressurised.

[hemi twofifteen turbo]

The turbo outlet is a constant smooth air supply, where as the engine breathes in say 500ml 'gulps'. Having larger piping is like having a larger plenum somewhat and minimises the pressure drop at every instant that another cylinder drops the intake pressure momentarily as it fills. The effects/benefits would vary greatly on a whole heaps of factors, i think most noticeable would be throttle body/plenum size.

[auto351]

The turbo outlet is a constant smooth air supply, where as the engine breathes in say 500ml 'gulps'.

\

Not sure if this is the case that the engine would gulps the air, I think it would be a more smother air draw , in the case of the 1JZ the inlet value timing would be 120degress apart, as the suction stroke happens over 180degress this means there will always be one inlet valve open & in some cases two (at the start & end of the cycle).
From this I would think the engine is always drawing air?

[white_sandshoe]

I'd tend to think that similar concepts in the N/A tuning world could be appled here. I agree with hemi twofifteen with the 'gulping' so to speak... You'll always have an inlet pulsation due to the path of air being opened then closed. Even if that pulse is only in the inlet runner from the plenum, it still happens.

auto351, you're spot on in what you're saying about the 1JZ... It's well known that straight 6 engines are the smoothest for power delivery, and it's due to the reasons you've stated. (as well as the follow on that the ignition is done in the same manner over the cycle.) Even then, there's still going to be a pulse due to the air 'backing up' when one valve is closed, and it's re-directed to the other valve opening, though this is likely to only be noticed in the inlet runner and maybe at certain points and times inside the plenum.

Now, my point is that in N/A tuning, more so on the exhaust side, but the same principles apply to inlet, there is a relationship between size of piping and airflow... There is also a relationship between size of piping and pressure, and the known relationship between pressure and temperature.

I'd suggest that using these three relationships, having the smaller piping between turbo and cooler means less backpressure on the turbine and higher air speed. This also means higher pressure and temperatures, but at least the air is getting to the cooler faster.

Then it hits the intercooler... Now, I don't know what equivilent sized pipe would flow the same as an intercooler of specific dimensions, but i'd imagine it'd be one heck of a big pipe... The pressure would drop some, as well as the obvious cooling effect an intercooler is designed for.

From there, it only makes sense to continue with a reduced air speed in a larger pipe, so that the temperature is not raised back up by the added pressure of tight piping, as well as the additional thickness of air taking longer to transfer latent heat from the rest of the engine bay. It'd also be beneficial to the smoothness of the engine by having larger pipes reducing the effect of that pulsing, no matter how small it might be. (or large, in the case of a 4 cyl with muchos lumpias cams...)

Anyways, I don't think the the aftermarket has gotten it to as fine an art as possible, where generic off the shelf items apply... but at least the principle is there.

The Japanese GT300 and GT500 guys are at the top of the game in that regard, where their setups are precision tuned to get every last ounce... even if that means and extra 2-3kw from tuning the length and ID profile of the inlet tract, specific to their needs.

Anyways, having 3 inch piping just looks phat... and that's enough for me. lol

[hemi twofifteen turbo]

edit -- as above re pulses