I would think that a heat shields would be much better than a wrap as the wrap would keep even more heat in. What exhaust do you have? Maby Shane can cut something out for the Kooks.
Custom exhaust. Yeah I think I am gonna have to do some additional heat shields to try to block some of the heat transfer. I think i would even consider some small directional fans pointed not at the transaxle but more along the 'lines' of the case to push away some of the heat. It's that hot.
Custom exhaust. Yeah I think I am gonna have to do some additional heat shields to try to block some of the heat transfer. I think i would even consider some small directional fans pointed not at the transaxle but more along the 'lines' of the case to push away some of the heat. It's that hot.
Do you know with certainty that the transaxle isn't the source of the heat? Are you running a transaxle oil cooler?
Cosmetics of exhaust wrap are horrible IMO especially if you have polished stainless investment in Kooks, etc
An aluminum reflector plate left natural finish of something like .040 suspended below the exhaust and with .500 or so airspace above the transaxle will reflect 80-90 of the thermal energy up and away from the transaxle case. from there your airflow improvements will help overall engine compartment temps remain manageable. You should be able to configure a cantilever hanger from the exhaust mounts to support it. When my Gen 2 is ready for body mount I was going to consider doing this.
I built similar deflectors for my engine mounts when I switched from the oil filled corvette parts to urethane and the GM fabric heatshields didn't fit great.
In aviation and big iron aluminum panel thermal reflectors are used extensively as the front line of managing unwanted heat transfer.
For 12v fans in various sizes made for the temps GTMs throw off look at the motorcycle/ATV product lines from SPAL and others - everything from 4 - 9 inch in pushers and pullers
Here is my solution which might help you if you like the look. The right side of the "Y" is blocked off and engine air only flows through the left side. This makes the airflow through the MAF smoother. The right side has a cutout underneath that dumps cold air on the tranny when a bimetallic thermostat exceeds 150 degrees. There is a marine 3" centrifugal blower just behind the passenger air intake that pushes the air. It's small enough that air still flows around it into the engine bay when not running. It rarely comes on, but works well when it does. I might lower the thermostat a few degrees. When I participate in driving events I just jumper the thermostat and let it run all the time.
The Marine units only push 175CFM. You finding that is enough? I guess at 3-4" 175CFM is probably a lot of air actually?
I am going to fab some heat shields from alum to block the radiant heat, but I don't expect it will be the end-all solution. There is going to need to be more air flow on my transaxle.
I was thinking of grabbing some air from a wheel well and guiding it towards the sides of the trans.
The Marine units only push 175CFM. You finding that is enough? I guess at 3-4" 175CFM is probably a lot of air actually?
I am going to fab some heat shields from alum to block the radiant heat, but I don't expect it will be the end-all solution. There is going to need to be more air flow on my transaxle.
I was thinking of grabbing some air from a wheel well and guiding it towards the sides of the trans.
If you are going to make custom heat shields, stainless is a much better material choice as far as heat transfer goes....go really thin if you are worried about the extra weight.
__________________
Ciao,
Joel
Working ever so slowly on GTM #269, Twin Turbo SBC, Ricardo, Kit arrived April 5, 2009
I installed two 5-inch fans in my diffuser to move air when the car is standing still. Figured it couldn't hurt. These are "waterproof" fans from Dayton - each moves about 150CFM and are really quiet. I put a grill on the exterior of the diffuser to cover each fan, and you can barely see it from the rear of the car.
The GTM engine bay is about 15 cubic feet, so two 150 cfm fans should exchange the air in the bay about 20 times per minute. Actually will be less because of obstruction, non-ideal air flow, etc., but should make a difference.
If you are not going to track your car hard, the heat shield out of aluminum is all you need. If I was going to do it again, would not use a tranny cooler
If you are going to make custom heat shields, stainless is a much better material choice as far as heat transfer goes....go really thin if you are worried about the extra weight.
Aluminum is an EXCELLENT conductor. it will soak up the heat and actually allow it to transfer as it radiates.
Stainless is not very good, it will reflect the heat.
Aluminum is an EXCELLENT conductor. it will soak up the heat and actually allow it to transfer as it radiates.
Stainless is not very good, it will reflect the heat.
Seems to me like that's why aluminum would be a bad choice and stainless would be good. The idea is to reflect the heat away from the trans, not conduct it towards the trans.
Aluminum is an EXCELLENT conductor. it will soak up the heat and actually allow it to transfer as it radiates.
Stainless is not very good, it will reflect the heat.
The lower conductivity of stainless is actually beneficial for radiation heat shielding. It keeps the backside of the shield cooler and keeps local hot spots from conducting to the entire heat shield so the entire shield average temperature should also be reduced compared to a aluminum shield.
__________________
Ciao,
Joel
Working ever so slowly on GTM #269, Twin Turbo SBC, Ricardo, Kit arrived April 5, 2009
I do have slits in the diffuser to let air out. However, I was running with the diffuser off during this issue. I was thinking of placing fans on the diffuser but I think I'd rather run air across the trans body then out the back (diffuser).
Santa is bringing me one of those laser temp guns for xMas. I think it was dropped off early. I will take some measurements of before, after, various methods to see what might work best.
My pipes are not wrapped. They are coated, but not wrapped. Debating on that one, hate to cover them up.
I don’t know if you want your diffusers for their looks or want to gain down force from them but cutting slits in them can cause a large drop off in performance. If you do drive at higher speeds it can also cause a shift in the aero balance and cause the car to become unstable. It isn’t just the volume of air that is lost that hurts but it can also cause turbulence both of which can reduce the speed of air flowing through the diffusers. The air speed is what makes the diffusers work. When I was racing my DSR which had sizeable diffusers I could see a difference in the down force produce on the data collected when I tapped over some 1/8” diameter rivet holes that were left open. You could also see the difference in the air flow through the diffuser by looking at oil streaks on the roof of the diffuser that that had been blown through by the air passing by. With the holes open there was some flow separation on one of the walls where it made a turn and after tapping the holes the air didn’t separate which increased the air speed in the diffuser and increased the effective area both of which increases down force
If you're looking for hi-flowing small fans, I've read that the radiator fans from a Suzuki Hyabusta flow a ton. Perhaps those in conjunction with a well placed stainless steel heat shield would really do the trick.
Bill, in my opinion, the angle of the diffuser on the GTM makes it close to worthless at high speeds anyway. I'm sure your DSR, if designed properly, had a much shallower angle to the diffuser.(?) That said, since we felt it was not doing much anyway, we put the louvers in on the race PDG GTM and it helped substantially with the cooling. For us anyways, the cooling was more important than the down force generated by a diffuser that was at too great of an angle to be effective with the higher speeds that we run. we can generate all the down force we could ever need with the proper rear wing.
Might not need fans at all. Heat shield alone may work. I do have an intercooler up above blowing down onto the trans. So of course the heat from that blowing down could be the cause, but for this particular day/run I don't think so. The day I was running it was 60 degrees out. Compressed (boost) into intercooler guessing 80-90 air temp then?
But the trans was hot. Concentrated mainly in the 'belly' of the unit. Must be radiant from the exhaust near the sides.
A carefully placed heat shield between the exhaust pipe and the trans I think will do the trick.
The lower conductivity of stainless is actually beneficial for radiation heat shielding. It keeps the backside of the shield cooler and keeps local hot spots from conducting to the entire heat shield so the entire shield average temperature should also be reduced compared to a aluminum shield.
That is what I was trying to say!!
the stainless will not soak up the heat and transfer it to the trans.
How much heat a stainless or aluminum panel absorbs itself has little or nothing to do with its performance as a heat deflector, its color has more to do than the material itself (black the ultimate absorber, shiny metal the ultimate reflector)
Its a physics problem (described by Kirchoffs law). The exhaust system is radiating near-field thermal energy as a wave (as all energy ultimately falls somewhere in the electromagnetic spectrum whether sound, visible light, or radioactive) and a bare metal surface is a pretty ideal reflector of the mostly far infrared wavelengths.
Stainless has some strength advantages in very thin gauges, but 6061 T6 with any shaping to work harden it also is more than enough. Aircraft use it extensively.
I'm an old car guy so I thought I would give a thought from some of my past experiences. On every car and truck I've owned they all have one thing in common, plenty of air from the front mounted raditor. This is no help with a GTM. The air on traditional vehicles exits the engine compartment by flowing back against the firewall and around the transmission and under the car for the most part, lots of cooling. Sense I do not have a GTM yet I can only throw out an idea. What if some sort of baffle / deflector was mounted at the base of the firewall to pick up some air from under the car and force it up around the front of the engine and followed up by some smaller ones place around the lower part of the engine bay to keep more air moving up around the exhaust area to force some of the heat from the manifolds out the back more quickly. May not be possible, but just trying to help. Move the hot air faster with cooler air is the real solution if possible
I also made up some replacement triangular panels for under the fuel tanks that accept a plastic NACA (w/ 3" round outlet) duct so that the duct comes up right behind the back of the fuel tank. You could buy a plastic plumbing elbow to attach to the top of the NACA duct to direct the air where you wanted it........or attach 3" duct hose to route it where needed.
__________________ Shane Vacek-VRaptor SpeedWorks, L.L.C. Supplier of Many Custom Products for the GTM! GTM's & SL-C's Custom Built for You! http://www.vraptorspeedworks.com
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