Intercooler Pipe Sizing (Single Turbo 1UZ)

[MKII_Supra]

I have been looking around at other people's setups, and see that IC pipe size varies quite a bit from build to build (along with variation on turbos, boost level, intercoolers, etc.).

I am using a Borg Warner S300SX3-66 which has a 3" compressor outlet. Since the throttle body seems to be the most restrictive point of the system (besides the individual intake runner) and it's diameter is around 3", it seem that the obvious is to go with 3". I am a bit worried however that with the length of IC piping being used and the lower boost I plan to run, 3" will realy reduce the intake velocity and be somewhat inefficient and laggy. I ran 2.5" on my previous 3 liter inline 6 with a 61mm Garrett, and was happy with the response.

Is there anything major to gain from using 3" IC pipes, or will the losses be justified by going with 2.5"? I plan to build my pipes with aluminized steel tubing since I have a MIG and can easily weld steel.

Thanks, -Mike

 

[XR8tt]

Bit tuff when turbo outlet 3".. It could be reduced ??
But I think your worrying too much..
Keep in mind the throttle body is down stream from turbo..
So chances are there's already some boost there ...
If anything I would use smaller pre intercooler...
2 litre engines often have long intake and they do o/k...

 

[gloverman]

If you had a modified motor and where chasing top end power I would go with three inch but it seems you are more after streetable power with response I would go with 2.5 inch. I was running with 2.5 inch on a stock internal motor and TD07 and was pleased with the response. I had similar power that you are after. Cheers

 

[JBrady]

I think the intercooler core and the end cap flow will be a bigger issue than 2.5" vs. 3".

Also, is the outlet ID or OD 3.00"? Most likely OD with apx .25" wall thickness. If so the ID will be more or less 2.5" anyway. Smaller pipe routes easier and weighs less for a given length. I don't think you run into trouble until you get over 75% of the speed of sound.... IOW, 3/4 of supersonic.

 

[JustenGT8]

3 inch will be fine. I run a pretty long 3 inch intake pipe and there's no lag to speak of....crunch the numbers and you'll find that compressor flow will fill the volume of the intake in hundreths of a second. There will be no difference in response you could pick from using a 3 inch pipe over a 2.5 inch one.

 

[MKII_Supra]

Thanks for the replies.

The intercooler I am using has a 17.5”x 11.75”x 3” core with end tanks that taper from 1-2”, with 3" OD outlets.

As stated, I am also worried about the ease of routing the bulky 3" pipes and the total weight being added. My car already has a few clearance holes for the 2.5" pipes I previously ran with my inline 6, in this configuration:



Since I plan to run the turbo closer to the passenger side (so exhaust can easily exit out the side with no steering shaft), there is going to be a cluster of things going on in that area. Hopefully I will have the turbo will arrive today or early next week, and I can test fit the engine and gauge my options.

Thanks,

-Mike

 

[JustenGT8]

If 2.5 is more convenient then use 2.5 The step up and down at the IC won't be ideal but nothing concerning really. I dunno that the weight difference is worth worrying about and if it is you should be moving to alloy pipe. But if 2.5 inch is easier to fit, that's a good enough size that there's no significant reasons not to use it.

 

[XR8tt]

Purchase a 2 1/2 or 3" donut for bends and you'll
find it much easier than mandrel bends...
Subaru being a boxer engine has long intake pipes when fitted with front mount..
They don't have issues if fitted with street applicable turbo..
Your lucky being a Supra !!!
Try early Celica !!! Sheesh..
That engine bay looks sooo nice!!
Seems a shame to remove engine..
No doubt you'll have the 1UZ looking the same..

 

[stevechumo]

The pipe size is imiportant, but the pipe length and bends are critical, too. If you'll go with big pipes, then try to make the pipes as short as possible and with less bends. If the length is too long and there're too many bends, then the air will take a longer time with pressure to fill up the area before entering the intake manifold. Even with smaller pipe size, shorter pipes with less bends are still very critical.

 

[MKII_Supra]

Thanks for all the replies gents. I am much more at ease going with the big boy 3" pipes now. Your comments and the fact that I see you can rotate the intake make shorter pipes easier to route and use.

-Mike