I have an 85 fiero with an Iron duke. I have been facing gremlins ever since I bought it. In that time I have rebuilt the engine, rebuilt transaxle, new computer and virtually every other part imaginable. Even with the TLC I have given my baby she still acts up(coil cracked, starters fried, intermittent shut downs....). The engine doesnt overheat but I have a feeling that the gremlins I am facing thrive in a warm climate. My question is if anybody knows of an inexpensive way to cool down the engine bay without adding huge scoops that extend over the roof. One main thing I was looking at is another heat vent on the decklid such as ones seen on rally cars and Mitsubishi Evolutions. I also entertained the idea of a fan in the trunk that sucks air out of the engine and into the outside. If you could please advise me on this issue I would greatly appreciate it.

Interesting that you bring up this question today. It's snowing outside and I've been forced to stay inside and "think" about my Fiero instead or work on it.

Quite often I'll get an idea about a problem or a situation involving my Fiero or Fieros in general. I've recently been thinking of an inexpensive way to add additional cooling to the engine bay without spending alot of time and effort. Something that could be simply done by the average owner and be worth doing.

Here is what I've come up with:

The concept: Use a broad narrow structure that fits beneath the car in front of the exhaust assm. to channel air into the engine compartment and exhausted through the LH and RH engine vents.

The structure: Using a sheet of thin aluminum or sheet metal, form a 1" thick box like structure that is between 1ft to 2ft wide, depending on the owners preference. While making this box, leave a 1" to 2" lip on each side so that the structure can be attached to the vehicle. The curves needed can be made by cutting past the lip into the 1" or 2" part of the box (which the fabricator decided earlier). This will allow you to be able to overlap the metal in the areas in which you desire a curve or bend. Next the lips should be predrilled slightly larger than the screw you intend on using to secure the structure. A minimum of screws should be used so that the structure will remain secure. I suggest extending the structure to a height close to that of the exhaust manifold. I suggest using short self starting hex head screws because it may be impossible to get a drill to some of the places you need to install screws and using hex head screws makes it possible to use a socket and ratchet instead of using a screwdriver. Ideally, a 90 degree drill would be perfect to drill holes to mount the structure, but few people own them and they are expensive to buy JUST for this one purpose.

Remarks: If done properly I estimate that this device will lower engine compartment temps by at least 40 to 50 degrees. It has no moving parts, is maintenance free and for those worried about it catching on something, while possible, it is unlikely because it is above the rear end area. I would rate the difficulty of this project a 5, meaning it doesn't take a mechanical genius to do it, but it can be a bit tedious to make the bends and cuts. It should take the average person with the proper tools about 2 to 3 hours. It is a project that I will definitely do, but is not at the "top" of my list.

I welcome all comments......good, bad, hilarious.......LOL! Open invite Revin

Phil

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87 FIERO GT 2.8 5spd

If you found my advice helpful, please take the time to give me a positive rating. Thanks

GT Dude has an interesting idea. I have wondered along that line myself before but not in as much detail.

I am about to start a rebuild of a spare 2.5 to put in my 84. One thing I plan to do to hopefully lower the under hood temp is have my stock exhaust manifold (and maybe the head pipe) coated by Jet Hot. I haven't heard of anyone doing this but I think it is worth a try. Fiero Store sells a coated exhaust but I can save about $100 buy having mine done instead. I invite any comments too. Any advice will be appreaciated as always.

U wanna, what are the details on your rebuild? You can PM me if you don't want to misdirect your own thread.

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Dwayne Mohr
84 SC Red
87 GT 5sp Silver
(Member under various names since 2001)

[This message has been edited by 1MohrFiero (edited 01-10-2004).]

some people put fans under the side vents to exhaust warm air and draw cool air in the engine compartment

I'm pretty sure the aerodynamics of the car were designed to channel as much under car air thru the engine compartment as possible. Have you noticed all the dirt that builds up on the rear decklid when you drive thru a dusty area (road construction for example)?
Removing the "louvers under the louvers" on the rear decklid vents will help some. A cool fan switch may help, as well as a colder thermostat (shop the mall).
You could add an oil cooler or remote dual filter.
I live in Florida, where it gets really hot in summer. Usually if everything is working right, there will be no problem even in traffic while running the AC.
I have a V6 auto with the cool switch, thermostat and modified vents mentioned above.
The last heating problem I had was caused by a leaking head gasket....
Or maybe you radiator is clogged?

[This message has been edited by NEPTUNE (edited 01-10-2004).]

1MohrFiero-You can always replace the 2 eng bay covers with vents from a later model. It looks good and will allow more air out of the eng compartment, but there is a tradeoff in that the area near the battery is now wide open to rain & snow. I live in a drought striken area so it doesn't affect me.

I would think that considering all of the rebuilding you've done, things should be working right. You might want to think about other things to help the cooling situation, like a larger radiator, lower fan switches, thermostats, ect. Something is def not sounding right for your situation.

I'm not sure if a deflector under the car will help... that air can already be rather warm from road and radiator heat. It would be interesting to investigate.

The larger problem is two fold....

1. The entire exhaust is in the engine bay. This creates tremendous amounts of air heating. Using a coating from Jet-Hot, Techline, etc should help but I don't know how much. It would probably need coating the whole exhaust and muffler. Even just exterior coating the parts should help. If you coated inside and out of all the parts before the catalyst it should help more, especially on a V6 with the bloody crossover the transmission pipe.

2. Air flow. Passive scoops likely don't help much and could even hurt. Example, A passive scoop that helps at highway speeds could cause major problems at other times if it's not built right. Such as in slow traffic or at traffic lights. At that point you want as much convection as posible. (Think chimeny and draft.)

Over the roof scoops are complicated.... Depending on how much pressure there is on the inlet, they could have a net flow of Zero under certain conditions as the air trying to convect up them pushes back. Convecting air can have quite a bit of lift. (Think hot air baloon.) A good example of dead time would be you are stopped at a traffic light and have a breeze hitting the front. The breeze could litterally cancel all the air trying to lift up the stopped rood scoop. Unless you have a strong breeze it won't force much if anything down a stopped scoop.

Heat can and will climb very fast if convection is blocked.

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Edison Carter: When did the News become Entertainment?
Murray: Since it was invented.

The Ogre's Fiero Cave (It's also at the top of every forum page...)

I think I will try a bigger radiator for starters. Any suggestions? I may also tinker with the existing vents and may add some fans to them. If these two projects do not solve the problem then I will have to think about body modifications such as more vents and possibly look into an air cooling system such as what is found in earlier VWs. Thanks for all the advice.

I think you are missing the point of some of this....

DO NOT confuse Engine Bay temp with Engine Coolant temp. They are not the same and only very slighty related.

A Fiero L4 should never need a "bigger" radiator than OE. GM built the cooling system to run in all 50 states.

If the engine is overheating then there is a problem. It could be a crapped up radiator, fan isn't working, a pinched hose, bad thermostat, crushed/bent coolant pipe and a few other things. It could be small amounts of several things at once. A slightly crapped radiator with a slightly bent pipe can restrict flow enough to cause over heating. Bent pipes are extremely common.

When I originally wrote the heat management section of my cave (that section currently offline.) I had a slightly crushed pipe and a leaking heater core. I didn't know about either problem yet. The heater core was letting small amounts of air into the system w/o pissing coolant on the floor. The partly crushed pipe was blocking coolant flow. After fixing both those items, I have not had any problem with high coolant temp even in 90-100F very humid weather. Not even in slow traffic. If the car is moving at all the radiator fan stays off. (And this is an 87 L4 which has an ECM controlled fan set to 225F.)

If you want a cooler engine bay, it is a completely different issue. changing the radiator will not make any difference. You need to get more air thru the engine bay and/or you need to insulate heat sources. Likely both.

But if I did put in a bigger radiator wouldnt that make the engine run at a cooler temperature which would make the heat from the engine (not exhaust) cooler. Or would that change be to small to notice? Also would it be possible to wrap the exhaust system in dynamat to help with the cooling, or would the dynamat not be able to withstand the extreme heat?

decklid vent fan pics here

[This message has been edited by lurker (edited 01-11-2004).]

The engine bay cooling system on a Fiero isn't obvious - but it's pretty effective. As the air flows over the body, there's a low pressure area created behind the roof due to the sudden dropoff of that vertical rear window. This pulls air up through the deck lid vents - there's actually a substantial amount of air flow generated in this way.

Any "improvement" involving scoops that force air down through the deck lid vents would work in opposition to the normal aerodynamic cooling; probably not a good plan.

What would be good would be a method that would boost the natural cooling; larger deck lid vents or a scoop under the car to deflect more air up into the engine bay. I believe the GM engineers considered this undercar scoop but decided against it due to snow and other environmental factors. Fans in the vents would help when the car is stopped - but would reduce the airflow at speed...

quote Originally posted by U Wanna Race: But if I did put in a bigger radiator wouldnt that make the engine run at a cooler temperature which would make the heat from the engine (not exhaust) cooler. Or would that change be to small to notice? Also would it be possible to wrap the exhaust system in dynamat to help with the cooling, or would the dynamat not be able to withstand the extreme heat?

Wraping the exhaust creates problems of it's own. Dynamat probably won't take that anyway. Exhaust can easily run 1000F if the engine has problems. It runs over 600F normally.

A bigger radiator will have no effect on engine bay temperature.

quote Originally posted by Whuffo: The engine bay cooling system on a Fiero isn't obvious - but it's pretty effective. As the air flows over the body, there's a low pressure area created behind the roof due to the sudden dropoff of that vertical rear window. This pulls air up through the deck lid vents - there's actually a substantial amount of air flow generated in this way.

anyone remember that green and white rally fiero?

there was a greeat pic of it cruising along a dirt road and you could see the air and dust being pulled through the decklid vents. it perfectly illistrates what wuffo is trying to say.

i'll see if i can't find it.

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