Intercooler sizing
 

I'm starting to source things for my Rotrex build and one of my biggest unknowns is the intercooler. Target wHP is around the 400-450 range running a c38-81 on my current N/A engine with slightly smaller cams. The goal is to pretty much scale my current output by 2 keeping everything else similar eg: power range from 6000 - 8500 rpm with lowish torque to preserve drivetrain. I'll be running my 5 speed seq dog box, a 4.1 rear diff and lots of aero.

I currently have a half width Honda radiator which easily cools my current engine and I think it will have enough capacity for the power I'm targeting. My original plan was to install an intercooler sitting next to it side by side so that both coolers get nice clean airflow through the mouth and out the bonnet and guards. I can pretty much fit a 300mm wide core, maybe even wider if I chop out the chassis rails and build a tubular front end, and I think I can fit 450mm high + end tanks and go up to 100mm thick or more...

Given this will be going on a very high flowing head with an open exhaust (so less boost than a stock 450whp engine) and that it will see nice cool airflow, will this be large enough? The engine is going to be living on the edge given I'm planning on high compression but I'll also be running solely on e85 and with relatively large cams so hopefully it should all work.

The reason I like the side by side layout is that I'll be mounting the Rotrex down low on the block where the alternator normally sits. It's a nice short run to the bottom of the intercooler, then it's straight from the top of the intercooler to the throttle body. Also the radiator sees nice clean airflow so engine cooling is less of a concern.

Should I try it or just abandon the idea of side by side and go 'V' mount with a bigger intercooler? Who has some experience / knowledge on this stuff?

This will do the job.

Cooling-Pro Bar & Plate Intercooler - 550 x 230 x 65mm 2.25 inch Outlets

Dann

Dann, I can't go and buy something off the shelf... that just isn't my style! Knowing me I'll do something crazy like billet end tanks or something.

Forsure 2.5 inch tube.and hopefully bigger from the ic to the TB. My TR8 Rated for 500hp intercooler that is "7" mounted gets me 20f over ambient and thats with my c30-74 at 10.5 psi.325whp

you might end up with some head lifting issues with the high comp and boost it will be very dependent on the cams and your tune.

The throttle body is 70mm so I'll run a 2.75" tube out of the top. The Rotrex exit is 51mm ID so I'll probably step that out to 2.25", make a 90 degree turn and across to the intercooler.

Head lifting might be a big issue. I have ARP head studs and I'm hoping that the larger duration cams with some overlap will drop the peak pressure down a little... I really won't know until I have it running. Given I'm targeting power up high in the revs I really don't care if I lose power in the low to midrange. The most of the rotrexed Hondas setup for track are running cams with around 250 degree @ 0.05", 310 degree adv. My current N/A cams are like 254 degree @ 0.05" or something so I was thinking of just giving it a go with them and changing out the cams if it doesn't make power. The problem will be at low revs given I don't have VVT to close up the overlap. I think it will just be blowing fuel and boost out the exhaust. At some point in the rev range the exhaust back pressure will keep in the fuel.

Dann, the 550 x 230 equal to 300 x 420... so as long as the frontal area is the same, and I don't restrict the flow path we should be good right?

Garrett or precision core. Or something with proper turbulator quality and placement from a repulable source. 99.9% of the cores out there these days are chinese junk. even supposedly "quality" stuff (like FM) is usually just rebranded junk. surface area is a lot less important than you think. some of these subaru cores are only 450x180x100 and sit on top of a glowing hot engine and have bad air feed and still manage to cool off 500whp worth of power on track