Engine bay cooling

[ohmygosuness]

Engine bay cooling seems like a concern for the GTM. My plan is, in addition to wrapping the exhaust, to install some fans and direct them towards low pressure area beyond the car body. My reasons are:

1) Potentially more airflow through the engine bay while driving.
2) Keep air flowing during idle.

For you seasoned builders, is this something that's been done before and proven effective or am I just high.

I heard ceramic coating the exhaust somewhat helps too. But I'd like to keep my options open :)

[VRaptor SpeedWorks, LLC]

Addressing heat in the GTM in general, I would suggest the following "outline" of stuff to consider:

1. Produce/provide/create as many paths as possible that you can to get fresh air into the engine bay and a path for heat to get out of the engine bay. IMO, the round-perforated alum mesh that comes with the FFR kit provides very little air flow. If you follow the manual and install that mesh in the side scoops, the hatch, the exhaust recess.......you've essentially sealed off the engine bay.....and any way for fresh air to get in or heat to get out.

2. The fans sound like a good idea, but I've never really seen a good way to use them or a good place to position them. I've had customers install them in the diffuser......and the problem there, is heat rises. If you have the fans positioned to push air out of the engine bay, they are at the lowest point in the engine bay, so they're likely just drawing fresh air from around the oil pan and blowing out out the diffuser.....which isn't really accomplishing anything. If you have them pushing air into the engine bay.....they are going to be battling the design of the diffuser....trying to draw air from a low pressure area and pushing it to a high pressure area.....not ideal. I've had customers install fans in the large alum panels behind the rear tires. Well, do you want to suck every particle of dust and dirt and road debris into your engine bay? If you blow the fans into the wheel area, is that really doing any good?

3. The #1 most effective way I've found to keep heat out of the cockpit is to: A) Keep the engine bay as cool as possible. B) Create a physical insulation barrier inside the tunnel. Keep all of the coolant and AC lines on the bottom side of the blanket/barrier and all of your electrical/other stuff on the top side of the barrier. Seal the tunnel off at the smallest place between the main dash and waterfall so that heat from the engine bay can't migrate forward into the tunnel area. Install a vented/louvered belly pan under the coolant tubes so that this sealed off area of heat has somewhere for all of the heat to go while driving. Air flow in the tunnel does not travel from front to rear.....it travels from engine bay to under the hood. Make sure that everything under the dash is completely sealed to the tunnel so that no air can get from the tunnel into the cockpit.

[ohmygosuness]

Thanks for your detailed input, Shane.

My thought with the fan is to seal off all openings in the engine bay and open side scoops (ones behind the doors). Then open up a hole in the rear and have a fan pointing directly behind the car (assuming back of the car has lowest pressure while driving). Think Gordan Murray's T-50, except I think his fan is there for downward force while I'll be using it to cool the engine bay. This should make a wind tunnel where air only flows one direction - in from the scoops and out to the rear - kind of like sucking air from a straw.

I'm also routing coolant lines outside the car, so I think heat in the cockpit shouldn't be a big issue.

Here's a pic for example
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[crash]

I have done a lot on the FFR PDG GTM race car to address heat concerns. I do not run mesh on the intakes on the sides of the car. As Shane said, more flow the better. I do not run quarter panel scoops because when we had "the fire" flames came out the 1/4 panel scoops and singed the driver's fire suit...down to the second layer. I ceramic coat the headers. Then I double wrap the headers with lava wrap. Then I reinstall the OEM header heat shields. I leave the exhaust uncoated but wrap the tubes FOUR times. Two other things here that are far different than most GTMs...the rear of the car below the tail lights has been cut out so air can come out much easier, but, the bottom of the engine bay is closed up with sheet metal. This closing in causes much more of a heat build towards the front of the engine bay. We had previously used acrylic windows on this car but once I closed in the bottom of the car those windows were melting. Which led me to what I believe is THE most significant change I have made for engine bay heat management, and that is...

using V Raptor's aluminum louvered rear window replacement. I went from not being able to touch the fiberglass rear window panel to being able to grab the aluminum louvered area without it being very hot. HUGE difference in under hood temperatures IMHO. Granted I did not actually put temp sensors in there and measure it, but the difference in feel was HUGE. I would highly recommend this product because, as Shane has said, the higher up you give a path for heat to get out the better, and this louvered insert begins at the roof height, so you can't get much higher than that.

I was actually just thinking about ordering another one from Shane for a spare since I will not be using anything else on the FFR PDG GTM because it works so well.

This insert in the picture is modified for my rear window air box that I made, so from Shane it will look slightly different in that the louvers will go all the way to the roof in the center.

[lance corsi]

Heat is an issue with mid engine cars. I built an 818 and decided to use louvers on the rear hatch without using the FFR supplied glass. In addition the roof scoop dumps its air into the engine bay, and I also am running quarter window scoops as well. My tail panel is open at the bottom and screened. I’m also running an electric water pump with an override switch to help with engine cooling after shutdown. I’ve wrapped my header pipes with lava wrap and have a lava blanket for my turbo. My intake manifold has a heat shield below it to help manage heat. I hope this is enough because I can’t think of anything else.

[ohmygosuness]

Crash - I suppose the race car is constantly getting airflow since it's always moving during races. Mine wouldn't be on the tracks as much. I wonder how hot it gets if I were to have it idle at a stop light. Also, I live in a small town. Speed limits here are like 35-45 mph max lol.

Lance - I'm definitely wrapping my exhaust. I may consider quarter window scoop if rear fender vents + hood scoop + fan still won't do the trick.

So, I understand air needs a place to enter (like scoops) and a place to exit (louvers/vent). I'm considering replacing the common exit (louvers) with a fan to help during idle. The fan will only be effective if there's no other exits to create a "wind tunnel" effect. So, it'll be scoops + either fan(s) or louver, not both.

[lance corsi]

I suppose a couple of well placed naca ducts couldn’t hurt either. But they’re passive too.

[beeman]

I suppose a couple of well placed naca ducts couldn’t hurt either. But they’re passive too.

NACA ducts require attached airflow, hard to identify best location for these without a wind tunnel. You could do some yarn tuft experimentation...

[crash]

Let me maybe approach this from another angle...anything and everything you can come up with that increases air flow in the engine bay will be helpful. I would think the louvered "window" would be even more beneficial if the car is stopped frequently. Obviously your call, but IMHO Shane's louvered insert is a game changer.

And the bigger the fan you can put in the engine bay the better. I just don't see where you are going to have the space for a big fan, but maybe if you modify the rear of the car to that of the T-50 it will be enough.

[ohmygosuness]

Let me maybe approach this from another angle...anything and everything you can come up with that increases air flow in the engine bay will be helpful. I would think the louvered "window" would be even more beneficial if the car is stopped frequently. Obviously your call, but IMHO Shane's louvered insert is a game changer.

And the bigger the fan you can put in the engine bay the better. I just don't see where you are going to have the space for a big fan, but maybe if you modify the rear of the car to that of the T-50 it will be enough.

I'm very open to different approaches in cooling this car. It would just be another science project/trial and error for me. The fan idea is something I've had in mind since I got the kit. Only problem is, since I don't have my transaxle yet, I don't know exactly how much space I'll have in the engine bay. I may have more than one smaller fans (all point rearward) if the trans is in the way or just scrap the idea all together and go with louvers.
Here is the "science" for this idea:

- If I have only louvers (during idle), then the rate of air is being pulled through engine bay is determined by the rate of air exiting the louvers due to pressure build-up from the heat of the engine. Maybe like ~25-50 CFM? (no idea, depends on ambient temp, surrounding wind velocity as well)
- If I have only fan(s) (LOL no pun intended) and no other vents for air to escape, then the airflow of the engine bay will be set by the CFM of the fan (like a wind tunnel). Therefore, depending on the CFM fan is rated for, it's a lot more convection. Just a google search shows small car fan rated ~300 CFM.
- If I have both louver + fan, then it won't be an enclosed area and the fan won't be able to enforce all its CFM in the whole engine bay.

Imagine drinking water from a cup through a straw (water is the "hot air" we're trying to get rid of). Now poke a hole on the side of your straw. Now you'll be sucking in air bubbles + some water. Meanwhile, without the hole, you'd be sucking only the water. Same in this situation - I'd like to extract as much hot air as possible. A sealed engine bay with inlets on one end and vents out the other end will cause air to flow only one direction, any louvers between them will be "leaks" and would interfere with one-direction flow stream.

Shane's louver is definitely something I'd consider. I might even order one just in case my idea is just a pipe dream.

[crash]

I actually previously tried exactly what you are talking about. I had an oil cooler on the drivers side and a trans cooler on the passenger side. I ducted the air from the door side scoops through fans, then through the coolers, then made ducting that forced the air onto the headers and exhaust. I figured, like you are, that the forced air would work better than just having air move around willy nilly. When I still had issues, then I completely reworked things and opened up everything as much as possible. I also eliminated the trans cooler by using a heat exchanger that put the trans heat into the water system. Then I increased the radiator size by over 60% to handle an increase in HP and the added trans heat. This allows 100% cool air to flow in on the drivers side. That goes over the fuel pumps before being ducted into the engine bay. I also still use the C5 crate exhaust manifolds, but switch sides so the exhaust runs up instead of down as I see no reason to heat the engine and transaxle with exhaust heat. So my exhaust now runs up a lot higher to the rear window area, which probably also contributed to the heat issue on the rear deck.

I had designed and built that sway bar setup before switching the exhaust system to the high version or I likely would have done that differently and had straighter shots from the headers into the muffler.

[ohmygosuness]

I actually previously tried exactly what you are talking about. I had an oil cooler on the drivers side and a trans cooler on the passenger side. I ducted the air from the door side scoops through fans, then through the coolers, then made ducting that forced the air onto the headers and exhaust. I figured, like you are, that the forced air would work better than just having air move around willy nilly. When I still had issues, then I completely reworked things and opened up everything as much as possible. I also eliminated the trans cooler by using a heat exchanger that put the trans heat into the water system. Then I increased the radiator size by over 60% to handle an increase in HP and the added trans heat. This allows 100% cool air to flow in on the drivers side. That goes over the fuel pumps before being ducted into the engine bay. I also still use the C5 crate exhaust manifolds, but switch sides so the exhaust runs up instead of down as I see no reason to heat the engine and transaxle with exhaust heat. So my exhaust now runs up a lot higher to the rear window area, which probably also contributed to the heat issue on the rear deck.

I had designed and built that sway bar setup before switching the exhaust system to the high version or I likely would have done that differently and had straighter shots from the headers into the muffler.

The only reason I can think of that the fan doesn't work is if it's not producing enough CFM. There's some math to it, where you add up the area of all the air scoops and multiply by the car speed. Say the GTM tops at 150 mph, it would be 150 x sum of the area of all the air inlets. Then buy a fan (or multiple fans) that combines to produce that CFM minimum.

It looks like the race car has its intake facing front of the car. That's actually not a bad idea if it could get fresh air directly from the roof scoop instead of sucking in hot air from the engine bay!

[crash]

We ran under a very low noise limit at Thunder Hill and also at Laguna Seca so we needed more room for the previous exhaust system that actually ran 3 mufflers, so I flipped the intake back around and used a "cobrahead" rubber intake duct and made the airbox. The FFR design probably flows a bit better, but that doesn't really matter if we can't meet sound requirements. Thought about a clean sheet redesign of the exhaust, sway bar, and intake air box/manifold, but that is a lot of work and there are other items that are currently higher priority...like ABS and adjustable front sway bar.

If you want the info on the cobrahead I can send it to you, but IIRC Richard, the previous owner, had moved the firewall forward a bit on the FFR PDG GTM, which is the only reason the flipped forward manifold even works. I don't think this setup will work on a stock GTM with the "waterfall" sheet metal. From what I understand, it is a very tight fit just to the manifold when the throttle body is facing the rear.

[crash]

Here's a picture of the cobrahead.

[ohmygosuness]

Here's a picture of the cobrahead.

What made you go with 2 alternators?

[crash]

What made you go with 2 alternators?

We do 24 hour endurance racing and had an alternator fail previously which left us with changing batteries every 30 minutes or so. That sucked. After that we have always run two alternators.

NOTE: No that is not where the serpentine belt runs on the water pump...I had made a change to the diameter of the crank pulley and was taking this pic to NAPA to help select a new, longer belt.