Venting underhood pressure

[s2man]

that's what I was thinking, samandw. louvers in the belly pan. louvers on the hood would require repainting

[mustngr]

For now I'm revising my bellypans. Gonna go back to just a front and rear pan.

Mine are made fom ABS plastic and follow the suspension and undercariage grimaces to a gnat's butt. Needless to say it was a lot of work, but who knew?

Something to consider for anyone engineering a pan. Where's all that air gonna go?

I keep a thermocouple attached under my hood (on the firewall, just behind the motor). The other end is always under the dash, so I can hook it up to my meter any time I make a modification.

Last summer the underhood temps on my stock Geo never exceded 150 degrees F. on a 100+ degree day. I blocked the grill in stages, and found that blocking either section of the grill sent temps to over 220 degrees in short order.

After installing the full pan temps went to near 200F at times, and it's winter here!

From a mechanical standpoint, I have concluded that grill blocks are a shortcut. The better way may indeed be to allow all that air to continue to come in, then give it somewhere to go (i.e. vents in the hood or fenders, or at least allowing it to go under the car).

I know some of you may disagree. There seems to be a false notion that heat=MPG.

To some extent this is true. Thinner lubricants offer less friction, hotter air molecules occupy more space, etc. But if that heat has nowhere to go, your dead car will get 0 MPG. To me heat ultimately means shortened life expectency of major components.

Just food for thought. I think we armchair engineers should think ahead, towards building a better overall package.

For example if you want to run a hot air intake. We already established that the principle to "works", to varying degrees. The "right" way to accomplish this may be to isolate your intake air (in something resembling a heater box with an air filter, fed by radiator or exhaust heat), rather than by heating up your entire engine compartment unneccessarily as some are now doing.

Just rambling, mostly cuz I'm avoiding going out there under the car.

[lovemysan]

My belly pan is vented out the the front suspension/axle area. I also installed 5 4"x10" vents running along under the exhaust system. I tested my pan in Kansas city traffic all last year with good results. I was able to keep water temp under 200f when it counted the most. A manual fan switch would help though.

My secret to keeping under hood temps to near normal is an HAI that picks up air at the exhaust manifold. You might consider taping your exhaust manifold. But the saturn likes the HAI idk about the geo.

[mustngr]

Nice work.

If you seal up the front undercarriage on a Metro the only openings left for cooling are the two slots that the tie rods run through. Not much area there.

I just gotta re-engineer the whole thing. The Metro's sills are flush with the floorpan, I need to extend them toward the ground and do something like you've done with your Saturn.

[holypaulie]

Another way to decrease underhood temperatures, is to wrap exhaust manifold with hi-quality wrap like racing cars have. Second way is to make coolant more efficient by changing ratio to 70% water/30% antifreeze + water wetter.

[lovemysan]

Mustanger, have you seen the mercedes e class underbody windtunnel pics. I think it was autospeed that posted them. Anyway Merc uses to portals about 8" in diameter just below the firewall area. You might consider looking into that style of underhood exhaust.

[GasSavers_RoadWarrior]

I was thinking about this a while back... it occurred to me that my mirror housings have about a 1/4 inch gap all round the glass (allowing clearance for adjustment I guess) and thus a 5x3 mirror has about 4 square inches around it. This is a low pressure area also. So began wondering if I could pipe engine bay heat into the mirror housings. This would provide some airflow bleed... and would defrost the mirrors in winter! (and maybe keep some rain off them too) There is a potential that with being a low pressure area, the 8 square inches for both sides, would vent much more air than 8 square inches of hood vent, and may negate some proportion of the base drag of the mirror housings....

If installing a belly pan, maybe making provision for air passage under the pan, all the way to the rear of the car would be a good idea, maybe plumbing it to come out of holes high in the bumper molding where pressure will be lowest.

[s2man]

Lol

[GasSavers_RoadWarrior]

Well I always wondered if there was something a little extra in Timmies when Roll up the Rim was on, but I swear I haven't had one today.