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Old 06-27-2010, 06:39 PM   #1 (permalink)
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Free belly pan in kansas city!

After 2 years I'm going to pull the belly pan. I'm tired of roasting. Living with a belly pan my observations are as follows. I no longer drive this car on long trips. Most times I drive it less than 3 miles at 35mph.

1) Lots of heat builds up underneath the car. Specifically at the catalytic convertor. The floor gets to 180f easy. The muffler has melted perforations into the aluminum paneling.

1a) Your bellypan will cause cooling issues. A few notes on the saturn: A panel can be added underneath the radiator to force air through it. A sealed grill block with passages to the radiator would be best. The HAI will reduce underhood temps. Limit IAT temps to not more than 190, you will loose power and mileage. Do not exceed 200f coolant temp, again you will loose power and mileage. I found IAT 150-180 and coolant at 190-195 to be most efficient.

2) Chassis flex buckles anything rigid under the car. Install a bellypan with the car on stands and it will form waves when you set the car down. I've had several pieces of frame work loose.

3) You need heat resistant materials

4) The pan should be parallel to the ground from the chin to the beginning of your diffuser. In my car this would require adding a 5" chin to the nose and it would scrub, scrape, and destroy itself. For a proper rear diffuser you will need to lower the rear bumper 3-4" on a saturn s car. I also had issues with the rear of the car sagging when loaded with more than 2 people. This causes the ground clearance to shrink towards the rear of the car. In the end the upraked chin ingesting extra air, decreasing ground clearance, and too steeply angled rear diffuser caused buffeting under the car.

5) The biggest problem with a BP is servicing the car. Jacking the car flexes the pan and framework. It also makes small things like oil changes time consuming. Then there is suspension travel. On the rear of the saturn there is a LOT to deal with. I ended up using a coroplast panels that float. and are zip tired to the lower control arms. This worked but formed a hump right at the begining of the all so important rear diffuser.

On the plus side
1) Your car won't burn up
2) Snow has almost no effect(because the engine and exhaust heat keep it clean)
3) The firewall forward section controls engine temperature


I intend the keep the firewall forward section as it helps then engine operate at its most efficient temperature. If you want my belly pan I'll be taking it off soon.

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Old 06-27-2010, 07:00 PM   #2 (permalink)
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........this and $$ are why manufacturers dont equip cars from the factory with these things.
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Old 06-27-2010, 08:51 PM   #3 (permalink)
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Before removing your belly pan, why not modify it to achieve heat extraction with outlets like fish gills?

That way, a Venturi effect is used to draw the hot air out, as parallel as possible to the flow of the slipstream, for low drag and cooling efficiency.

And, with segmented panels, less buckling. The panel over the exhaust pipes could be made of aluminum window screen fitted tightly to a light frame.

Overall, what sort of fuel mileage do you get, to compare before and after removal of the panels?

How about noise, before and after?
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Old 06-27-2010, 11:36 PM   #4 (permalink)
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FE? Not sure if it effected mileage that much. Certainly makes no difference around town. Currently has a 28 gauge steel center section to deal with heat. I found the light gauge aluminum to be too noisy. The side sections are 3/16" solid poly that went wavy the first time it got hot. I no longer drive this car on lengthy trips. Making the bellypan more trouble than its worth.

My wife had complications from our first childbirth which required the purchase of something more comfortable. The suburban became our daily driver when our 3rd child was born. So this car has turned into a errand car making only short trips. I had my fun with it. Twice averaged well over 50mpg on 3000 mile vacations crammed with stuff. I'm thinking of auto crossing it now.
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Old 06-27-2010, 11:47 PM   #5 (permalink)
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Looking at your pics I think there are several improvements that could be made that may alleviate some of the issues you are having.....nonetheless very nice job overall.
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Old 06-28-2010, 04:27 AM   #6 (permalink)
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Add in some exhaust fans and ports.

You could also do a partial belly pan instead of a full belly pan.
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Old 06-28-2010, 01:16 PM   #7 (permalink)
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I've had an almost full under-body smoothing panels since last fall, and have not noticed any high temperatures on the car.

I did make a few engineering decisions however:

1) Since my panels are made from foam, check the surfaces of these items in high heat areas and look for excess temperatures.
2) Cover the first cat con inside the engine compartment with fiberglass batting.
2a) This causes the cat con to get up to temperature quicker (more efficient).
2b) It also keeps under hood temps down, almost to the same level as no smoothing panels. This was confirmed in winter driving where the Insight engine looses heat very easily.
2c) The batting is important, as it has a high R-value and keeps heat away from things you don't want to get hot.
2d) If you use batting on the under-side of the car, keep moisture away from it, as rain will reduce the effectiveness tremendously.
2e) Paint things with white colored paint to help maintain the heat inside the emitter or to reflect the emitted heat away from objects. Black-body radiation theory mentions that black objects absorb heat easier than light colors.
2f) Cover things with tin-foil, which again causes the heat to be reflected from the hot object, even better than white paint. This is one reason you do not want to chrome plate your engine!! Think custom motorcycle engines!

No place on the car has shown melted aluminum or even melted foam. Foam distorts at 250F.

Aerocivic has had a belly pan longer than I, again with no heat related issues.

This shows that a belly pan can indeed made to work, and may take some preparation up front to consider all the options that you have available.

Just my $.02

Jim.

Last edited by 3-Wheeler; 06-28-2010 at 01:30 PM..
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Old 06-29-2010, 09:57 AM   #8 (permalink)
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Quote:
Originally Posted by 3-Wheeler View Post
I've had an almost full under-body smoothing panels since last fall, and have not noticed any high temperatures on the car.

I did make a few engineering decisions however:

1) Since my panels are made from foam, check the surfaces of these items in high heat areas and look for excess temperatures.
2) Cover the first cat con inside the engine compartment with fiberglass batting.
2a) This causes the cat con to get up to temperature quicker (more efficient).
2b) It also keeps under hood temps down, almost to the same level as no smoothing panels. This was confirmed in winter driving where the Insight engine looses heat very easily.
2c) The batting is important, as it has a high R-value and keeps heat away from things you don't want to get hot.
2d) If you use batting on the under-side of the car, keep moisture away from it, as rain will reduce the effectiveness tremendously.
2e) Paint things with white colored paint to help maintain the heat inside the emitter or to reflect the emitted heat away from objects. Black-body radiation theory mentions that black objects absorb heat easier than light colors.
2f) Cover things with tin-foil, which again causes the heat to be reflected from the hot object, even better than white paint. This is one reason you do not want to chrome plate your engine!! Think custom motorcycle engines!

No place on the car has shown melted aluminum or even melted foam. Foam distorts at 250F.

Aerocivic has had a belly pan longer than I, again with no heat related issues.

This shows that a belly pan can indeed made to work, and may take some preparation up front to consider all the options that you have available.

Just my $.02

Jim.


Also, consider rock wool (aka mineral wool) panels instead of fiberglass, as rock wool has much higher temperature capacity while absorbing much less moisture. Rock wool is an excellent sound absorber, which would make the car quieter. Some such panels come with aluminum foil covering, which of course helps with heat reflectivity. Aluminum foil tape is another option, comes on rolls like duct tape and conducts heat very well.

I may use rock wool reflective panel material to make heat containment boxes around my exhaust manifold and turbocharger, with proper vents to the airstream. This will keep the engine bay much cooler.
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Old 06-29-2010, 07:38 PM   #9 (permalink)
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I would have done the following:

Air extractor in hood, with ducting directly from radiator.

Side vents from engine bay....that heat has to get out.

Vent in rear bumper...this would help pump out some of the exhaust heat as well as drive-train heat. You would probably have to make a proper venturi with an extension at the end past the bumper in order to allow for a sharp end and prevent a vacuum from stagnating the air back there.

Exhaust wrap and stainless steel with sandwiched fiberglass heat shielding through out exhaust track. It would be great if you could exit the exhaust way up front MB SLR style....

Vents immediately aft of engine bay in undertray...again engine heat needs to go somewhere.

I think that with these improvements you would see even greater fuel economy, better component longevity, and certainly reduced cabin temps....as well as better high speed stability
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Old 06-29-2010, 10:50 PM   #10 (permalink)
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no pan problems here

my pans seal under my car very well,, but i guess enough heat gets out the wheel wells,, because even with a full upper grill block and a 50% lower grill block (down from 75% block in winter) my car never gets that hot . 203 when setting in traffic but stays between 185- 195 almost all the time. bellypan and grillblock worked out great for my toyota echo. im sure some cars wont react as well as others, mine is thick coloplast and even where it contacts the muffler has not melted. and these mods have helped my mpgs, but if you seldom get over 35 mph in your car its not gonna help much. mines been on for around six months.

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