I've got a small special problem: Last year I changed the turbo of my RX7 to a T04B. I also upgraded the fuel system and so on. So far everything is running great but i get heat problems everytime i drive faster than 120mph for more than round about 5 minutes in the summer.
Till now my intercooler is a mount which has the same size as the S4 front bumper air inlet. The factory playtic undertray is still there but i guess because of my fmic the radiator doesn't see enough cold air for that high speeds.

Last week I was talking to a mechanic. He suggested getting an intercooler as big as the radiator, mounting it right in front of the radiator and building a nice air duct.
My first idea was building a v-mount. What could work better?

 

https://www.rx7club.com/2nd-generati...ioning-923286/

Just get a better hood vent. I made one from aluminum, sort of as an experiment to see if the lip really makes a difference. It really does. I ended up staying with the experimental vent for now. I'll be getting a more aesthetic one soon. The intake temps are only about 10-20 degrees above ambient, and that's when doing a 15 psi pull up hill. I'll have to wait to see what summer brings though.

This style won't work since the hood is sloped. The incoming air from underneath the intercooler gets stopped because the same speed air is hitting it from the top. You end up with zero airflow, and nothing gets cooled



This style hood vent works wonders. Like I said though, get something a little prettier. The lip creates a low pressure area right behind it, sucking the air straight out.

 

Do you think that could work with my old fmic?

By the way: My original hood vent (Turbo II hood) is quite useless now. Would it be possible that the air which is pressed in through that vent at high speeds is causing a heat build-up at the engine?

 

you might actually try the stock intercooler, or a top mount. the factory hood scoop actually does work, and it doesn't block the radiator.

 

heres an idea, dont go 120mph?

 

I know it works but not with a front mount. That's waht i meant.

I don't think the stock intercooler would be big enough for about 14psi. I could get even more heat problems with it.

Hehe nice idea barkz but I still want to fix the heat problem.

 

I meant "get a better hood vent than what I have".

Do you still use the stock radiator, or is it an aluminum one? I believe that the stock radiator has no business cooling a rotary engine in the first place.

I seriously doubt that if you stuck a larger intercooler in front of your radiator that you'd experience better temps. If you're going to be travelling that fast, vmount it and make damn sure you do a good job of ducting it.

 

https://www.rx7club.com/2nd-generati...-hfmic-145822/

 

I'm using an aluminum radiator. One other thing i could try is to build my own undertray. I think i could build a better one than the factory piece.

That v-mount looks awsome El Aviator. If the temperature doesn't get better with my own undertray, then I'l build such a thing, too.

 

if i had the time/patience, that is what my bay would look like

 

Are your radiator and intercooler sandwiched directly together? That makes a huge difference. Any gap between coolers and airflow would be disturbed. Is there proper duct work? You could always use the stock intercooler and water injection, or go vmount.

Or don't go that fast. Over 120mph for 5 minutes?! WTF?!

 

you guys need to look at his location.

one other thing i thought of is the oil cooler, if the air flow to the oil cooler is blocked, you can have the biggest radiator in the world and it'll overheat.

second, if the intercooler is right in the grille opening, if the air can't pass thru the core it'll just come out and go under the car. hard to test that

also every OEM car with a front mount also has a separate duct for the radiator, so the intercooler is not 100% in front of the radiator

 

I can't even think of a freeway or road near me that would allow me to go 120 for five minutes. I've hit 115 before for about 30 seconds, and then I jumped a length of about 7 feet( I even heard the tires screech as I landed) going over an overpass that was poorly constructed(this resulted in a few drops off pee in my pants, and me PROMPTLY slowing down)

******' shitty LA freeways

 

our roads in California would be considered dangerously bad in most of the rest of the world, they are in horrible condition.

 

My fathers dodge cummins and freightliner cummins have the intercooler sandwiched with the radiator, with no gap between them.

My mothers genesis coupe has a intercooler about the size and shape of the fc oil cooler placed directly below the radiator, with no gap between.

I think there is a common denominator. For an efficient fmic setup, without each unit ducted separately, there must be no gap between cores. I believe a gap will disrupt airflow. Just because it entered the core in a straight pattern, doesn't mean it will leave and continue through the next core that is a foot away in the same manner. It will probably become a little turbulent, might not enter the second core. Just my theory.

 

You should block your stock TII hood vent if you are not using it as it does ram air into the engine bay.

Sounds ok to get more cool air under the hood, but in reality this lowers the pressure differential between the front grille opening where the cooling air enters and the underbody where the cooling air exits.

Lowering the pressure differential lowers the total volume of flow.

The mechanic you spoke to was correct that if you must front mount an IC the best way is to use a large, thin IC core directly coupled to the radiator. This is the way all OEMs stack heat exchangers because it allows the incoming air to penetrate the heat exchangers as one core with the least drop in velocity.

The usual aftermarket FMIC for the RX-7 where the IC core is directly in the grille is the worst design- it only exists for the bling. All the cooling air passes through the IC losing velocity and then circulates around between the IC and radiator unable to penetrate the radiator core.

In addition to this, much of the incoming air doesn't even penetrate the IC core as it hits the frontal area IC and spills right over the sides of the bumper covers duct and around, over and under the car instead of through the IC. This is what you are experiencing at high speeds.

Having a deeper (stock) duct before the heat exchangers means it is harder for the air to circulate back out of the duct without penetrating the heat exchanger.

 

Ive heard about arc tmic, but how effienct are they at higher hp..

 

Don't know about ARC, but I installed an HKS TMIC on my S4 TurboVert and there was a very noticable seat of the pants improvement. Much larger end tanks, much more free flowing. Still, heat soak remains the issue with any TMIC.