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914World.com _ 914World Garage _ Rear valance and engine heat
Posted by: MW 914 Nov 9 2006, 09:55 AM
I recently bought a fiberglass rear valance. It is the larger /6 style. Shortly after I bought it, it was brought to my attention that this has been rumored to trap warm air around the engine. In theory this seems logical....any truth to this in reality? More heat is the last thisg that I need here in AZ.
Posted by: brant Nov 9 2006, 09:58 AM
yes..
Posted by: Air_Cooled_Nut Nov 9 2006, 10:04 AM
No.
Posted by: Ferg Nov 9 2006, 10:18 AM
Maybe 
Posted by: john rogers Nov 9 2006, 10:19 AM
Yes and No. Yes if you do not have one of the large stock type mufflers that would sit in front of it such as a race car with stingers and No if you have the muffler.
Posted by: MW 914 Nov 9 2006, 10:42 AM
Maybe
Fantastic....you guys are great. I assume that Brant is serious but I'm not sure about the "no" answer.
In all seriousness, I currently have an aftermarket 911 muffler(see my avatar) on it that has been rumored to be on the large side. How about if I "slotted" the valance and glassed in some mesh behind the slots?
You think that would get the air out?
Posted by: So.Cal.914 Nov 9 2006, 10:54 AM
Maybe
Fantastic....you guys are great. I assume that Brant is serious but I'm not sure about the "no" answer.
In all seriousness, I currently have an aftermarket 911 muffler(see my avatar) on it that has been rumored to be on the large side. How about if I "slotted" the valance and glassed in some mesh behind the slots?
You think that would get the air out?I am sure it would help alot but with that big muffler in the way it probably
deflects alot of air.
Posted by: Aaron Cox Nov 9 2006, 11:31 AM
you probably wont notice any adverse effects...
Posted by: TROJANMAN Nov 9 2006, 11:39 AM
mike,
just buy a bigger radiator
oh....and all of that extra heat is probably what's making your brakes squeek
Posted by: MW 914 Nov 9 2006, 11:42 AM
mike,
just buy a bigger radiator
oh....and all of that extra heat is probably what's making your brakes squeek
Note to self - Ignore all users from Colorado.
Posted by: john rogers Nov 9 2006, 11:43 AM
In thinking about it more, it must NOT trap the heat as it certinly does not trap oil when you blow and engine wide open at speed. When mine went at about 120 or so all the oil went into the 356 right behind me!
Posted by: LvSteveH Nov 9 2006, 11:44 AM
On your car, the muffler provides enough ram-jet effect to easily negate any issues with the rear valance (Have ya seen the size of his exhaust tips??)
Your best bet is to try it out and see. It will be interesting to see how it works with your oil cooler location. It only takes 5 minutes to take it back off if you need to.
Posted by: MW 914 Nov 9 2006, 11:46 AM
Your best bet is to try it out and see. It will be interesting to see how it works with your oil cooler location. It only takes 5 minutes to take it back off if you need to.
Thing is...I can sell it now if I want to. After I cut it for my exhaust it won't be worth much to any one else.
Posted by: brant Nov 9 2006, 11:54 AM
Mike,
sorry for the differences of opinions.
someone here must have the old link.
once upon a time there was an old thread or link of a 914 guy who did ton's of actual temperature measurements.
was it brad anderson?.... can't remember
but in the old testing that was done, there was an actual test that showed removing the rear valance dropped engine bay or was it oil temperatures.
this was tested on a -4cylinder... but should yield similar results on a -6
my experience is only racing, but I've ALWAYS been told and understood that for a track car you should drop the rear valance no matter which muffler you used. even if you have a large sausage style muffler, you can reduce the insulation to it by dropping the valance.
I don't think we are talking about a big difference.
I think that for a street car the aesthetics might outweigh the benefit.
but it is my belief that it will help lower temperatures some.
so as mentioned above, try running it both ways (off/on) and see if it helps you
brant
Posted by: Howard Nov 9 2006, 11:57 AM
you probably wont notice any adverse effects...
And that heat is 'all the way back' so unlikely to affect performance or passenger comfort. Having said that, I just cut a nice piece of insulation for my trunk. Got pretty warm (but not enough to melt the kids' crayons) back there on trek to RRC. Attached image(s)
Posted by: jsteele22 Nov 9 2006, 12:48 PM
you probably wont notice any adverse effects...
And that heat is 'all the way back' so unlikely to affect performance or passenger comfort. Having said that, I just cut a nice piece of insulation for my trunk. Got pretty warm (but not enough to melt the kids' crayons) back there on trek to RRC.I think the thinking is that as air passes from the region under the engine, then past the tranny, it suddenly hits a wall at the rear of the car, a wall that drops just about straight down from the trunk floor level, down to the lower bumper level, and then a few more inches if you have a valence. So from the paint of view of air flow, its a major restriction. I've been working on my engine bay from the inside (just crawl under and sit on the gound) and I was thinking just the other day, that from that perspective the rear end of the car looks like a drag chute. Anyway, based on this I would be willing to bet that removing the valence gives some inprovement, but I have no clue how much.
WARNING : Some of the opinions expressed in this post originated in the state of Colorado. They may not be suitable for consumption by pesons living in other areasa. Please consult a qualified non-Colorado resident before taking this advice at face value. May contain nuts.
Posted by: brant Nov 9 2006, 12:59 PM
exactly Jeff!
and in a snow state like colorado, you will find many of the old cars have valances bent outward where they have drug in deep snow.
the valance (in order to hide everything for aesthetics) is the lowest hanging item usually.
Posted by: VegasRacer Nov 9 2006, 01:11 PM
Elvira has a deep rear valance and I have never had any problems with heat.
*(I also know not to keep my Crayons in the rear trunk)
Posted by: McMark Nov 9 2006, 01:21 PM
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Posted by: anthony Nov 9 2006, 01:42 PM
So what is the goal here? If you have a 3.2L six then I assume you have a front oil cooler and no cooling issues. Correct?
It sounds like you have plenty of power so trying to improve airflow under the car isn't going to help that much. Unless this is a race car I'd keep the valence because it looks so much better.
Posted by: MW 914 Nov 9 2006, 02:06 PM
So what is the goal here? If you have a 3.2L six then I assume you have a front oil cooler and no cooling issues. Correct?
It sounds like you have plenty of power so trying to improve airflow under the car isn't going to help that much. Unless this is a race car I'd keep the valence because it looks so much better.
The goal is to not trap a bunch of hot/dead air around the motor since I have the oil cooler under the rear trunk. The cooler under the trunk was sort of an experiment. So far, no trouble but I've only run it in sub-100 degree temps. If need be I will relocate it to the front but I would prefer not to. So...my question was really at trying to determine if the valance would reduce airflow bacck there enough to hinder the oil cooler.
Posted by: McMark Nov 9 2006, 02:17 PM
If you've already got it, run it. All we've got right now is 'old' information. Keep and eye on the temps and let us know what you find out. 
Posted by: anthony Nov 9 2006, 03:19 PM
Pretty easy to run with and without and see if you notice a difference.
Posted by: MW 914 Nov 9 2006, 03:30 PM
Pretty easy to run with and without and see if you notice a difference.
I agree. I was just looking for easy answers before I cut up a valance.
Posted by: East coaster Nov 9 2006, 08:32 PM
When in doubt......vent it out 
Posted by: turboman808 Nov 9 2006, 09:02 PM
Or just get rid of it.
Posted by: Howard Nov 9 2006, 09:39 PM
Valances and engine tin are for sissies 
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Posted by: brant Nov 9 2006, 09:57 PM
did this turn into a thread about valance-less cars?
hey howard, whats that drip pan for?
is that where the "incontin(g)ent" signature came from?
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Posted by: brant Nov 9 2006, 10:06 PM
and here is version #2....
I saved weight by building a different bracket:
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Posted by: MW 914 Nov 9 2006, 10:27 PM
hey howard, whats that drip pan for?
is that where the "incontin(g)ent" signature came from?
Brant - perhaps you should ask Howard where he got that drip pan?
Lemme guess....that is just from working on the car, right??
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Posted by: Howard Nov 9 2006, 11:59 PM
Drip pans are for sissies, too. There ain't one under Moby.. that's a skid plate 
Posted by: brant Nov 10 2006, 07:54 AM
ahhh....
but do you see the oil line in the bucket.
I was changing the oil, which caused the mess.
brant
Posted by: TROJANMAN Nov 10 2006, 08:38 AM
ahhh....
but do you see the oil line in the bucket.
I was changing the oil, which caused the mess.
brant
don't overwhelm him brant
I am not sure he knows what it means to change the oil
to him, changing the oil means writing a check
Posted by: MW 914 Nov 10 2006, 02:34 PM
ahhh....
but do you see the oil line in the bucket.
I was changing the oil, which caused the mess.
brant
don't overwhelm him brant
I am not sure he knows what it means to change the oil
to him, changing the oil means writing a check
....and I can assure you that it wouldn't go to a shop with floors as dirty as Brant's.
Posted by: carr914 Nov 10 2006, 05:58 PM
If you want a rear valance, go out and get some wine & cheese too
T.C.
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Posted by: VegasRacer Nov 10 2006, 08:33 PM
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