Under Hood Temp Reduction

[JohnC]

Thought I would ask if anyone has done this to the Vibe…remove the rubber seal at the rear edge of the hood to increase airflow in the engine compartment/decrease intake air temperature. This was a very easy and no-cost mod for the Dodge Neon that actually worked great.I was skeptical at the time so I temporarily installed a remote thermometer under the hood at the intake, well sure enough, the under hood temperature dropped 5 degrees when the rubber seal was removed (only at speeds above 25mph). On a side note it was amazing how much the under hood temp climbed in stop and go traffic.I am not going to do this to my Vibe because I am staying with the OEM air intake which gets fresh relatively cool air already. Just thought someone with an intake that’s under hood might benefit. If you want more info you could probably find it in my old stompin grounds… neon.org.

[hman33]

sounds good in theory. i'll have to give it a try. always looking for cheap ways to increase horsepower. and free sounds pretty cheap to me. one question though. does the hood rattle at all with the seal missing?

[scherry2]

Quote, originally posted by JohnC »remove the rubber seal at the rear edge of the hood to increase airflow in the engine compartment/decrease intake air temperature. that seal is there for a reason (or auto manufacturers would leave it off and save money). the seal is to prevent engine fumes from entering the fresh air vent under the cowl into the vehicle. if you want to remove it go ahead, I can imagine the headaches already, I'm just letting you know what its there for.

[Jahntassa]

I guess water seeping down through that seal isn't a problem then? I'd be worried about the master brake cylender, and whatever else might be under there..

[scherry2]

Quote, originally posted by Jahntassa »I guess water seeping down through that seal isn't a problem then? I'd be worried about the master brake cylender, and whatever else might be under there..na there is a stove pipe shaped vent water will go around it but not in.

[JohnC]

Quote, originally posted by scherry2 »that seal is there for a reason (or auto manufacturers would leave it off and save money). the seal is to prevent engine fumes from entering the fresh air vent under the cowl into the vehicle. if you want to remove it go ahead, I can imagine the headaches already, I'm just letting you know what its there for. Well I drove over 100k miles without it in my Neon and never had any problems with fumes or water. Unless there is somekind of fluid leak on the engine or an exhaust leak at the exhaust manifold there shouldn't be any fumes from the engine compartment. I suppose the air drawn into the cabin could be warmer than the outside air normally drawn in, although I never noticed this either.

[joatmon]

under hood temp reduction is why Celtic Curse made his hood scoop functionalhttp://forums.genvibe.com/zerothread?id=11325

[MadBill]

The pressure difference between the cowl area and the underhood region is very dependent on vehicle shape and grill arrangements. In the absence of a rear edge seal, sometimes air flows out, sometimes in. To know which it is on the Vibe, an easy test is to tape 3-4" lengths of string at various points along the back edge of the hood. Then drive at a varying speeds and note whether they blow out or are sucked in. Ta dah! Your very own wind tunnel test! (Of course, either way could help underhood temps, either by forcing in cold air, or venting hot; only if no particular flow is observed would it indicate no possible effect.)

[Smokin' Rubber]

I think for most driving the vents blow out hot air. I have driven a couple times at night when it was in the 50's with the defrost set to max cold (I almost always have it on defrast to make sure the window doesn't fog) the windshield right above the vents has water condensing on it and even after I drive for a while (and used the windshield wipers to move the water around and help it dry) it kept coming back.That;s just one day one experience tho. We'd need more tests to actually figure out the sucking in and out of the rear hood vents and Bill said

[Jahntassa]

You'd be almost guaranteed to get water above the defrost vents in that condition. By having the defroster on max cold, you're making the windshield COLDER than the ouside air, which is making water condense on the windshield. You'd have to make the air coming from the defroster warmer to "burn" off the water by making the windshield warmer than the surrounding air. I think the vents in front of the windshield are an intake only, not an exhaust.

[Smokin' Rubber]

Could be, but that doesn't make sense how the air coming from the vents is colder than outside air seeing as how it basically is outside air. On the coolest setting I think all it does is suck in and expel pure outside air, once you start moving the heat up it starts blowing heat off the engine. Plus I had all the windows open so the temps/humidity of the inside and outside of the window should have been close.Also, this might be just a stab in the dark, but I would imagine that some of the air that comes in through the front grills would get pushed back up over the engine and end up exitting through those grills. But then again maybe not, it would be hard to say without testing it

[joatmon]

In these cars, the AC is turned on automatically when you switch to defrost mode, I suppose to dehumidfy the air.. So, on a cool day, with defrost on and set to most cool, you'll have refigerated air blowing on the windshield, which will cool the glass more than just ambient air would, so you'll get condensation where the defrost air hits the glass. When it happens to me I just turn the temp up a little, and it clears up

[Smokin' Rubber]

oooh, good to know, thanks Joat. Didn't know it automatically turns AC on when you have on defrost

[ragingfish]

Quote, originally posted by Jahntassa »I think the vents in front of the windshield are an intake only, not an exhaust.Correct.

[sidewinder]

I have been told by our A/C man that another reason for the A/C to turn on with defrost is to run the A/C compressor in the winter to keep some lube moving in the compressor. Otherwise in some states the A/C compressor might not ever turn on for months and then in the summer when you hit the A/C button the compressor would be dry of lube and really be hard on the comperssor. Just what I heard and it seems to make sense to me.