Forced engine compartment cooling with full belly pan

[Sidakers]

Ok, so I was thinking about building a corroplast belly pan on my sl2 after reading about one another saturn owner built; not only because I'd like to improve my mpg, but because the factory air damn got ripped off by some road debris, now my car feels rather floaty and less safe to drive at highway speeds.

Most of my miles are highway miles (I live right by the on ramp to the main corridor through wichita, and work right by the off ramp 10 miles down the road or so) so I really figure I'd see an mpg improvement as well as stability from a full belly pan.

My concern is engine compartment cooling. I figure a lot of heat actually gets pulled out under the car, so I'd like to force cool it somehow. This got me thinking. I figure I could put two 12v computer fans near the top of my engine bay (heat rises, right?) duct the airflow down with dryer-vent piping and flushmount a dryer vent (like the kind with the flaps that close with no airflow) into the corroplast.

I figure the flaps on the vents would close at high speeds due to terminal velocity, but I could build a thermostat that would activate the fans once the engine bay reached a certain temperature, forcing the flaps open and venting the engine bay. Otherwise, the fans could run while idling or at low speeds, to vent the bay while not being aerodynamically inhibitive.

Anyone heard of anything like this, or have any thoughts?

Also, Hi. I read this forum a lot but this would be my first post

[Daox]

Its not necessary. You're not sealing it that tight at all. There are still huge areas for the air to escape (wheel wells).

[vtec-e]

My intercooler is on top of the engine (diesel) and when i made a full bellypan the airflow from the intercooler was blocked off. MPG suffered as a result. I ducted it as best i could but still no joy. Bellypan removed and is now standing at the back of the shed.....

[BamZipPow]

I don't believe the computer fans will create enough pressure to open the flaps fully...especially if you use dryer vent hose.

Have you actually measured yer under hood temps? I have with my thermocoupler setup...highly accurate/calibrated and fast changing.

Top number is fer the top of the engine/air plenum while the lower number is the temp nearest my oil catch jar.


I've measured about a 30°F increase above ambient with my grill blocked at 66% while driving. Not sure what it was without the grill block. I do know my under hood temps rise the highest after driving/parking and there's no air flow under there. I've seen it as high as 175°F.

To vent the excess heat...I just open my hood up fer about 20 minutes (at home only) and the temps drop about 60°F within a short period of time. It might keep some components from cooking too much...but it might be a moot point since there's about 350,000 miles on the truck already.

[Sidakers]

you may be right about the dryer vent, a less turbulent form od ducting may be ideal, perhaps pvc with 45° elbows. i could also put Y's in it to combine two pipes to the vent, that may also help with the pressure issue as well. and im not talking about the spring loaded vents that are forced shut, i'd just use the cheapies so they would hang open at low speeds.

I like to err on the side of caution though. Half the point of this project is to save me money, not cost me cause i cooked something important. =P

[Daox]

Take a look at basjoos aerocivic, he has nearly everything (grill and bellypan) sealed up and has no problems with cooling.

Aerocivic - Honda Civic modifications for maximum gas mileage - aerocivic.com

[BamZipPow]

I'm headed up to Wichita by Friday...maybe we can meet up and we can come up with some ideas.

[Exalta-STA]

You can use hood spacers to cool up the engine bay

[BamZipPow]

Originally Posted by Exalta-STA

You can use hood spacers to cool up the engine bay

You have to be careful doing that as there are some safety stops to keep the hood from shearing off in an accident and taking out the passenger compartment.

[Daox]

Spacing the hood up is not a good idea. The hood to windshield is a high pressure area on almost all vehicles. It makes air enter from the top and then it goes under the car which is going to be bad for aerodynamics.