question regarding intercooler upgrade for nbse

Mr Sexy · Postby **Mr Sexy** » Fri May 08, 2015 9:25 pm

Managed to pick up an intercooler along with some other goodies for my se recently, how ever after getting home and taking a good look at it the inlets look a little small. They have an id of 40mm so need a 2'' joiner. Would this be too much of a restriction? I imagine the stock tube size is some thing like 2.25'' am i correct? Every one I see upgrading there intercoolers appear to be going from the 2.25'' stock pipe to 2.5".

At the end of the day it might be pretty far away but the end goal is too run some decent power and dont want to be doing things twice.

timk · Postby **timk** » Fri May 08, 2015 9:51 pm

Sounds like you've already answered your own question! I think it would be best to swap it with one with a more appropriate inlet/outlet.

EDIT: Are you sure the SE piping isn't 2"? If the inlet/outlet match then that's even better! I think I went from 2" (SE piping) to 2.25" (intercooler).

Cheers

Postby **NitroDann** » Sat May 09, 2015 1:39 am

2" supports 400whp comfortably.

speed · Postby **speed** » Tue May 12, 2015 9:51 am

NitroDann wrote:2" supports 400whp comfortably.

Dann, in your experience, Is there any negatives to running 2 inch?
I ended up going 2.25 as I thought best to be same as stock or a bit bigger. Is this wrong?

Stock SE is just under 2.25 inch

Postby **NitroDann** » Tue May 12, 2015 10:46 am

This is stock SE piping, I literally went out the front and checked both SE's right now.

This is 1.75". There are guys in the states putting 30psi into these and making >400whp on EFR turbos.

You want the air to move slower than the speed of sound, thats easy enough to calculate, and that is how I size intercooler piping. If you go bigger than you need it wont become laggy (calculate how long it takes for air to travel through 6 feet of pipe at the speed of sound lol) but it is uneccessary and becomes harder to fit on the car.

The other rule is no more than one size change on the intake or the intercooler piping, that kills flow. So from 3" pod down to compressor inlet size, one smooth step, and from turbo outlet size to the intercooler and typically a step up into the intercooler and the same size from cooler outlet to throttle, this is typically 2" hotside and 2.5" IC into the 2.5" throttle body.

The following dyno is a 1.6L MX5 with the piping configuration described above.

Dann

Lokiel · Postby **Lokiel** » Tue May 12, 2015 3:19 pm

NitroDann wrote:;
This is stock SE piping, I literally went out the front and checked both SE's right now.

This is 1.75". There are guys in the states putting 30psi into these and making >400whp on EFR turbos.

The SE's IHI turbo compressor outlet is 1.75" - this is the narrowest point of the entire turbo->TB flow chain so is the biggest plumbing flow restriction (aside from the intercooler).
The SE's "token" intercooler has 2" barbs (or something close to it).
It's easier to route smaller diameter plumbing, especially on the hot side where there's not as much room as the cold side, so Mazda kept it small and stepped up to the 2" intercooler inlet barb.
The TBI is about 2.5" and the SE has some odd combinations of pipe steppings and a rubber hose to step up from the 2" intercooler outlet barb to the TBI's 2.5" barb.

The MX5-sized EFR turbos (and most other MX5-sized turbos) have a 2" compressor outlet - if you upgrade to one of these, you'll eliminate all the 1.75" SE pipes since they'll choke flow.
- ie. NOBODY would still be using 1.75" pipes with a larger turbo.

NitroDann wrote:The other rule is no more than one size change on the intake or the intercooler piping, that kills flow. So from 3" pod down to compressor inlet size, one smooth step, and from turbo outlet size to the intercooler and typically a step up into the intercooler and the same size from cooler outlet to throttle, this is typically 2" hotside and 2.5" IC into the 2.5" throttle body.

I think this "rule" is more like "avoid step-downs since they choke flow".

speed · Postby **speed** » Tue May 12, 2015 7:04 pm

Thanks Dann and Lokiel.

Since I'm SC and not turbo, I should have stated that the pipe I'm referring to is from IC to TB elbow.
I thought this pipe was slightly smaller then 2.25 inches but larger than 2.00 inches.

SC outlet is 2.5 inch which steps down to 2.25 and goes into my funky looking and badly welded pancake pipe to the IC which steps down slightly from 2.25 to SE cooler.

Think I would have been better off going with the 2.00 to clear the top radiator panel.
Oh well, hoping I can send my dodgy creation to Dann to make a pretty one.
I make a better carpenter then a sheety...

On the plus side, seems I didn't go too big or too small