Ok I wanted to start a thread here for the N/A section just to have people respond about engine bay heat and what they have and haven't tried. What works best for what application as far as type and size of radiator. Electric or clutch fan or both. Oil coolers what kind you have, where its mounted and what your oil temps, water temps and all that are. Basically anythign that has to do with cooling the motor. Different hoods, heat sheilds, air ducts anything you can think of. The reason why is I've made it my quest to make the temps as stable as possible on water temp oil temp and what not so I can drive the car harder longer before it needs to rest.

Don't just answer aluminium radiator because thats not the answer. I can heat soak mine real good in about 30secs-1 minute of sliding the car around on the street/parking lots. Or climbing curvy hilly mountain roads at WOT. Piston engines are easy to cure of this because they don't produce alot of heat, but as we all know the rotary engine is a hot bastard to say the least.

My setup on my FC is a huge barely fitting in the car aluminium radiator thats for like a chevy 350 or something. Dual pass, 2+ inch wide with a 20lb radiator cap I believe. stock oil cooler in stock position. Two electric fans one on front and one on back of the radiator. The car is N/A but has a T2 hood which I think is actually making the heat stay in. The header gets very hot of course as well not glowing or anything but they are really hot! My opinion is that the stock oil cooler is too close to the radiator and they may be polluting each other depending on which is hotter. There's a point where the fans run for a relly long time till they cut off again. I will add the point of the car never getting hotter than half way on the factory gauge but the engine just smells hot. especially worse on hot days and nights usually I don't drive the car hard in the day time though as much of my activity is illegal so it takes place at night much like the better part of the people on this forum I'm sure.

I'm thinking custom heatsheild to seal the header off from the engine bay completely. laying the oil cooler down on more of an angle like my FB which improved the oil temps by about 10 degrees. Just leaned it forward like the factory comp manual says. Or switching to 2 side mount oil coolers in the brake duct areas. getting an N/A hood and putting louvers (For lack of a better word) in it so the radiator air can escape. Then the T2 hood won't be causing turbulence the opposite way. Possibly building better ducting material in the nose to feed the radiator higher pressure air.

 

I haven't tried anything yet for my FC but I've spent a bit of time contemplating this problem.

A heat shield is a good idea as the exhaust radiates a tremendous amount of heat. I think you'd have to go with some sort of double walled design to make it effective though.

Venting a NA hood would be a better option then the t2 hood. The t2 hood also increases drag over the NA hood.

You could vent the bay into the fenders but I'm not sure how effective it would be without a vent on the outside of the car to help draw the air out.

 

I was thinking the exact same thing about the exhaust. The double walled part that is. My idea was to get some aluminium sheetmetal and keep it apart with really light duty aluminium c-channel. Plus that would give it structure and keep it from making weird metal rattling noises. Having it in mounted to the engine but in close proximity to the firewall and frame with possibly the front angling down towards the subframe. So that its in kind of its own "wheelwell" if you will. I need to buy some polyurethane engine mounts though so the engine doesn't move at all pretty much that way I can get the gaps tighter. I even thought of addind a small piece of metal to angle air up from the ground into the "wheelwell" not sure that would matter much though.

 

Yeah I was thinking along the same lines although what I would do is make a fiberglass sandwich of sorts. Figure out the shape you need with cardboard then make two copies out of like 0.080" aluminum, then make a third but remove the center so you basically have a 1" thick ring the same shape as your top/bottom plates. Fill the middle with fiberglass insulation from home depot and rivet it all together. This is very similar to how a lot of OEM heat shields are made, and should provide the best results. The aluminum will reflect a certain portion of the heat and the fiber glass will help prevent the rest from soaking through.

You mentioned motor mounts .... so here is a shameless plug
https://www.rx7club.com/vendor-classifieds-276/sale-fb-motor-mounts-844799/

 

IMO it helps to break it down a bit.

1. we know the header is hot, its a huge source of radiant heat too, right above the intake manifold. making a shield, or wrapping it is easy.

2. radiator. if you have one that is as big as the opening in the car, you can seal it off, so that ALL of the air has to pass thru the core. then you can duct it. IMO with the "stock" setup in an FC there is plenty of air coming IN to the radiator, but it doesn't really have a good place to go, i could be wrong, and in fact our experience shows that a big radiator like that, sealed off is fine on an NA

3. oil cooler. again in a stock car, it seems like the cooler is quite big, but it gets really poor air flow. just getting some air flow to the thing, really works well

 

I agree that there is a fair bit of air getting into the FC engine bay (FB's don't seem to get nearly as much). The problem really is evacuation. The under body tray helps keep it in, but if you remove the tray you increase drag.

I know on the passenger side behind the cruise control is a nice sized hole that could be used to plumb some ducting to allow for better engine bay venting. I'll have to remember to take a look to see if the drivers side is the same. You could run some ducting down and vent it to the bottom of the fender which would be functional and not leave holes in your fenders. In theory the air rushing past the car would also help draw the air out of the engine bay.

 

Great thread! And perfect timing.

I'm starting to cope with all these things. First off that I'm starting with is a cold/ram air intake. Will be fed through one of the front bumper holes to a 4" duct vent, into an enclosed manifold for the ITB's. I've just sent out the CAD files to a company this morning to get prices on thing to get laser cut. Another thing that I will also be doing is wrapping all the pieces ontop of the engine bay with DEI's reflect-a-gold (http://www.designengineering.com/newsdetail.asp?id=53) or similar product.

Next one will be the idea of sealing up the headers by making a box around it. Having thinwall SS headers gets things going pretty hot in the engine bay. So hot that I've had the windshield washer bottle disform and fall off its mount. Wrapping the headers up definatly helped that problem and left things alot cooler, but having talked to my engine builder who's been racing since the 70's with rotaries he said that wrapping a rotary's headers could make your loose HP as it would create more backpressure. This apperently works fine for piston engines because they need the pipes to stay warm to speed up velocity of the gases since they have an "off period" in the headers. But in our case its always a constant flow. I'm not 100% sure that a double wall is worth the extra weight, but ceramic coating it might be a better option.

Radiator ducing along with changing to FMOC as oppose to the water-oil cooler will be in place third. I need to get an aluminum rad first before I do anything so that I don't have to do things twice. But even with my setup right now, car stays under 93*C at the track which I guess is pretty decent.

Another one that I'm really curious about doing, but still not know how much of a performance its actually going to give, is maybe installing a fuel cooler (not one that you pack with ice or what ever all the time, but one that is like a small rad (like this : http://static.summitracing.com/globa...flx-4130_w.jpg). I kinda skimmed a bit over wether they do work or not, but seems like its more for carburated setup as the fuel usually sits in the lines getting warm from the fuel pump, engine bay heat and what not. In a return style like all EFI setups, it doesn't have time to cool properly. I wonder if me just having my aluminum lines is enough though too. As it probably cools the lines under the car easier than standard steel, or even worse, SS braided lines.

Last but not least, vented hood. Just waiting on someone to really finish up a carbon fiber one for the FB.

 

Racing BEat and several other companies already make the heat shield between the header and intake manifold.

 

I know but it doesn't seal the header off from the rest of the engine bay which would be way more useful imo.

 

That makes absolutely no sense. To me it sounds like someone who has misunderstood since the 70's how exhaust systems work and why. That doesn't make it right today. I'm not even going to take the time to elaborate on the topic other than to just say his hypothesis is wrong.

 

Ceramic coating the header will also make a huge difference, but you have to make sure you get it done by a knowledgeable place. Most coatings break down at around 1600F which is too low for a rotary, there is an additive you can use to increase the break down point to closer to 2000f. A good place will also coat the header inside and out. The drawback is that headers have a tendency to break down faster, same applies to exhaust wrap.

 

yes, but the great thing about RB stuff is that they last like 50 years, so if you wrap it, cut the life in half you're still looking at a couple decades, which is really more than you need!

i own an RB header that is drinking age

 

One thing to remember is that copper cools almost two times more efficiantly than aluminum. The reason the aftermarket uses aluminum is beacuse it's half the price in weight, cheaper to manu facture, and half the weight. But these companies are raping you for the cheap costs of the alluminum radiators. You could go to a radiator shop and get a custom copper 3 core radiator for about $600. That'll solve your cooling issues. In my NA FB that makes 190 whp I run a stock FC aluminum and plastic radiator with a stock FB oil cooler mounted 6" infront of the radiator. I've only had cooling issues on the dyno because there is never addiquate air flow. Other than that 75 second autoX's and my oil temps are at 180* and water at 185*

I just vented my hood and didn't see the drip in water temps I thought I was going to see, but I'm positive underhood temps are way down! I can touch my air cleaner after sitting in traffic now.
https://www.rx7club.com/1st-gen-general-discussion-207/vented-hood-843760/

 

That was his opinion, and I just wanted to post it (I might of worded things a wrong way in my statement, but in the end he says pretty much ditch the header wrap that I have on there and make a box around it). I would love to hear your opinion on that topic though. This is what this board is made for, research (or atleast in my opinion thats what I see it for) and research isn't based on one source.

 

I think if you have a vent that drops right behind the radiator, as oppose to just venting out you might see a better drop in water temps.

 

I actually see no issues with header wrap. It's a myth that header wrap can trap moisture which will prematurely rust out the pipes. If the people spreading these myths realized what temperatures those pipes hit, I'm sure they'd realize that any water soaked into the wrap isn't going to be there very long. That is actually a nonissue.

The only reason why it could be an issue at all has to do with the strength of the welds at the pipe to flange locations. Specifically with stainless or when stainless is welded to mild steel. Stainless has a pretty high expansion coefficient compared to other metals with temperature variation and this has to be accounted for during welding. Use of the correct welding rod is especially important for this reason. Just because the wleding wire used will work doesn't mean it's good. By wrapping stainless pipes, you keep more heat in the system which can affect expansion that causes cracking at the weld joints. If everything is done correctly even this too isn't much of a concern. Anything is possible though.

Heat shielding is a good thing whether it's from wrap or ceramic coating or even a shield. Keeping heat away from the intake manifold is a good thing. I'd suggest getting the intake manifold ceramic coated so it can't pick up as much heat and doing this in addition to all of the other precautions. Don't worry about "added backpressure" in the exhaust from doing this. It's not going to happen.

You aren't going to see water or oil temps really fall below 180* or so no matter how well everything is vented as long as there is a thermostat in place.

 

I was looking over my engine bay (fc) today and thinking about cooling. One option that I loathe to recommend is washers under the hood hinges. This is an old trick. It raises the rear of the hood to allow for venting ..... the problem is it looks like taint.

Thinking about this lead me to wonder about cutting some ducting into the top of the fire wall where it meets the wiper compartment. I haven't pulled my cowl off yet to look but as long as the compartment is sealed against the inside of the cabin then this could be a viable option to increase airflow without visually changing the appearance of the vehicle.

 

That will probably not work at all (As far as cutting into the firewall to vent out the hot air). There's actually more air being pushed in there then pulled out. In our first gens (well atleast the S3) we have an air vent that goes straight from there to inside cabin. At high speeds (~60mph) some people think I have the A/C on. What I have seen people do though is route their intake to there, because it is fresh cool air being rammed in there.

Just my 2cents

 

Yeah I'm not shocked, as I said I hadn't actually looked in there to see. But now I might have a better route for my intake

 

i think the box is valid too. there are two functions.

1. since the intake is right over the exhaust, isolating the two is the biggie, cooler intake = gooder

2. keeping the heat IN the exhaust helps too, but seems maybe more subtle?

 

if you've ever UNWRAPPED a header/downpipe you'd see that it actually does lead a harder life being wrapped.

but yes, the first failure point is the welds. the only pipe ive ever seen fail was a piecut mild steel downpipe for an FD, it failed at the welds, but the main piping didnt look very good either.

but if you had a decent part to start with, its not really a problem

 

Of course it leads a harder life. It stays hotter. The point is that functionally it's really a nonissue and people make more of a big deal out of it than they need to.

 

Even a new $150 parts store radiator will be leaps and bounds better than some 10+ year old junk that is corroded on the outside and scaled on the inside.

The biggest problem I have had with cooling systems is prying the money out of my hands...

I run a stock FB radiator in mine because, well, it's the same size as the FC within 1/2" or so, and it bolts in like it was made for the car. I do run a GSL-SE oil cooler as well, but since my car does not have A/C, I made a kind of duct/tray out of reinforced rubber (truck mudflap scraps) that goes from the top of the oil cooler to the middle of the radiator, to ensure that air never bypasses it. The electric fan is also biased to the bottom of the radiator.

I don't know what my oil temps get to, but at a recent rallycross I was seeing coolant temps around 210deg at the end of a ~95sec run, but the oil cooler never seems to get hot to the touch. So either it works really well or the thermostat is stuck shut. A temp gauge is on my List.

Cooldown between runs seems to go fastest with the engine off and hood open and just let it radiate out, instead of idling it with the fan and heater on full blast.

Unfortunately, opening the hood means getting out of the car, and it takes me about a minute to get the 5-point and arm restraints sorted out so I don't like to leave the car if I don't have to. So I'm looking into my venting options...

Certainly getting the air OUT from under the hood is more important than getting it there. At speed the air pressure under the hood is high enough to raise it about 4 inches. Interestingly, with a 12A it only goes up maybe an inch.

 

interesting thread concerning various types of rads:

http://www.eng-tips.com/viewthread.cfm?qid=61247

 

back in the pro7 days, the cool setup was a good brass/copper shorty style radiator, with the oil cooler mounted under it (the rx4 one if you had $$$)

then you get a big aluminum sheet, that goes between the two coolers and up to the opening in the front. adjust height at the front until the temps are good.

worked well for roadraced stock port 12a's....