Lower engine and IAT2 temps with free mod...

[fullboogie]

Ten days ago I started a little experiment. I removed the weatherstripping from the underside of the hood, near the windshield and noticed a very significant venting effect. After ten days of watching engine temps and IAT2's, I can say that removing the weatherstripping absolutely lowers both. Extended idling won't be affected for obvious reasons. But in any situation in which the car is moving for a period of time, I've seen nearly 10 degree lower engine temps and 6-8 degree lower IAT2 temps.

Remove the weatherstripping and get your engine up to operating temps, and place your hand anywhere along the back of the hood. You'll be very surprised at how much heat is vented out. I can say that after logging temps for 10 days on the way to work (12 miles highway, 90-ish degree ambient temps, 90-ish humidity, readings taken at the exact same place on the highway), I've seen the improvements listed above. Prior to this simple mod, I never, ever saw engine temps in the 170's, and never saw IAT2's in this range. I certainly don't think this is a magic bullet for temperature issues, but it sure appears to help and is freaking free.

Thoughts? Comments?

 

[wallywagon]

Great write up! I will be doing this this weekend.

 

[bossnova3]

Thanks for the experiment will definitely give this a try. Again thanks for sharing

Ed

 

[fullboogie]

Suggestion - just remove the rubber weatherstripping, but leave the clips in the underside of the hood. If you are careful, it's an easy removal. If you don't like the mod, you can easily reattach it to the clips.

 

[Jimmysidecarr]

Did you try the string test?

Tape some short pieces of string to that location and then drive it, and report back which direction the string goes.

Into the engine bay or out of the engine bay.

On most cars the base of the windshield is a high pressure zone and the air will go into the engine bay not out.

Remember cowl induction Camaro hoods?

 

[Tob]

When I added my Red Top battery I wasn't happy with the clearance between the battery terminals and the hood. I added a couple of washers between the hood hinge(s) and the hood. I noticed that the seal no longer closed off the rear of the hood and wondered which way air would flow there and if there would be any type of temperature drop. Interesting...

 

[Robert M]

Did you try the string test?

Tape some short pieces of string to that location and then drive it, and report back which direction the string goes.

Into the engine bay or out of the engine bay.

On most cars the base of the windshield is a high pressure zone and the air will go into the engine bay not out.

Remember cowl induction Camaro hoods?

I spoke with a tech at H.O.Fibertrends and he said that the 1995 Cobra R hood, with the opening in the rear (drivers side) was specifically designed for heat extraction.

Inside engine compartment view........

In front of the driver view........

We were having this discussion on another forum, so I decided to call the people who made this hood since I knew it had an opening at the rear. It just happened that the guy who answered the phone has been at H.O. for many years and was involved with the 95R hood project. He was very familiar with this hood and its function. He did mention that at very high speeds, like 140+, that the string could possibly go the other way, but it would require higher speeds.



R

 

[redline]

the gt500 hood has the vents just wondering if the seal in the back of the hood is not there that it would create vacuum . no scientist here.just a thought.

 

[fullboogie]

TOB - I also added washers on either side to raise the hood. It absolutely helps.

Other replies - you have to have a hood specifically designed to take advantage of the high pressure area, which our hood is not. Also, that affect only works at high speeds, which is not what we are talking about. Just try it. You don't need strings taped to the hood to see the results.

 

[racebronco2]

I heard this years ago on the 03/04 cobras. People swore it helped. I did the string test up to 80mph. Even at 20mph the strings went inside the crevice. Like jimmy said it's a high pressure area. Under the hood is a low pressure area. For the air to exit the rear of the hood it would have to have more pressure than the base of the windshield. Think about it..... how can a restricted opening about half the size of the base of the windshield flow more air that is not restricted. A string test will show us the truth.

 

[kyl]

Any pics?

 

[Blazeone]

I did this mod about a year ago, this is an old trick that corvette owners did back when I owned them.

As far as negative verus positive pressure it doesnt matter if the hot air is exiting or the outside air is getting sucked in it's still a good outcome.

Addtionally a stop lights and low speed heat will exit the rear of the hood.

 

[fullboogie]

I heard this years ago on the 03/04 cobras. People swore it helped. I did the string test up to 80mph. Even at 20mph the strings went inside the crevice. Like jimmy said it's a high pressure area. Under the hood is a low pressure area. For the air to exit the rear of the hood it would have to have more pressure than the base of the windshield. Think about it..... how can a restricted opening about half the size of the base of the windshield flow more air that is not restricted. A string test will show us the truth.

Don't know why you're making this more than it should be. Remove the strip and place your hand anywhere near the back of the hood. Heat, and lots of it, is coming out. After a ride the windshield wiper arms are hot. My datalogging shows lowered temps. If that isn't enough for you, nobody is making you try this. But your pressure arguments are contrary to what I have directly observed.

Why don't you do the "string test" and let us all know how it works out?

 

[ZOMBEAST]

I actually thought about doing this some time ago. Only reason I didn't was in in case I got caught in the rain. I might try this at the strip since you've gotten good result.

 

[stkjock]

Dave


with the notorious hood shake of the S197s I wonder if you got the car to "speed" to see if there was any difference in how the hood acted?


Seems like a good (and cheap - i.e. free) way to vent some added heat from under hood.

 

[fullboogie]

I ride 12 miles on the highway, each way, every day for work. I'm not getting any hood shake or anything else.

Like I said, I've been monitoring engine coolant temps and IAT2's for three weeks since I installed Van's H/E, so I've got a pretty good idea what the numbers are in various situations. Over the last 10 days since I did this mod, it seems like removing the weatherstripping has lowered my temps. Hey, if someone tries it and doesn't like it, they can always put it back on - it's held on with clips, so it easily comes off and goes back on.

Zombeast - I really don't think rain will be a problem. The strip is up under the rear of the hood, so I can't see how rain would get in there. Besides, we have two big vents in our hood that don't seem to cause a problem, right?

 

[stkjock]

I ride 12 miles on the highway, each way, every day for work. I'm not getting any hood shake or anything else.

yes, I realize it's highway, however I was trying to be discreet in my question..... as to being at "speed" (wink wink nudge nudge..... )

 

[gtt500]

I did this mod about a year ago, this is an old trick that corvette owners did back when I owned them.

As far as negative verus positive pressure it doesnt matter if the hot air is exiting or the outside air is getting sucked in it's still a good outcome.

Addtionally a stop lights and low speed heat will exit the rear of the hood.

You are right,this is a very old trick.When I first got involved in drag racing in the '60s,we used shim the rear of the hood up so air would enter the engine area while racing.At idle it would allow hot air to escape.When I installed my Super Snake hood,I left the weather strip off for that very reason.It works.

 

[03 DSG Snake]

:read:

 

[97snakebite]

killer gauge!!! what is it?