FredR

A while ago I fitted an ally belly pan that I purchased from 928 motorsports. Nice piece of kit that I can recommend. Needed a bit of adjustment on the trim but otherwise fitted no problem.

Have not really thought about it since fitting it -seems to work perfectly OK. For some weird reason something sprang to mind last night and that is the pan does not have those two upright "scoops" [if is that is an apt description] that the stock plastic pan has.

Do those scopps [ducts, whatever] serve a practical purpose? Maybe the intent it to remove these items from the stock plastic thing and fit them to the new component but unfortunately when I purchased this item, my current GTS did not ahve the pan fitted at all.

I have seen various thoughts about the utility of the belly pan- my personal undersanding being tha tit improves aerodynamics at higher speeds to help the ground effect- right or wrong no idea.

Cannot sayI have notcied a difference one way of the other but I reckon the ally pan will sure help protect the underside mechanically if nothing else.

Best wishes

Fred R

Emboss

Assuming it's the same as a '88 S4, there's two NACA ducts on the belly pan that redirect some air up into the engine somewhere, presumably for cooling purposes. I can check tonight to see where they end up.

Bertrand Daoust

Always nice to have it. As original, but...
I removed mine about 3 years ago and never put it back... A lot easier whenever you want to work or check anything under there! But, that's me.
Might put it back there someday. When there will be nothing else to do there. Realy not sure if it will ever happen...

Speedtoys

They shift air to the motor mounts.

Tom in Austin

Jerry Feather, are you out there? ... NACA ducts for our replacement belly pans would be a great project to add to your list!

Rob Edwards

Jerry, here are your templates. Measurements are all in mm.

Tom in Austin

Rob, you are awesome!

Rob Edwards

Forgot the OCD meds that day.

Ed Scherer

Rob, kinda nice, but Jerry's just not going to be able to get anywhere on this without knowing the diameter and location of the mounting holes.

Rob Edwards

#30 drill bit would be about right, I think I'd just mark the ducts thru the existing pan holes and drill....

slate blue

i always thought the ducts or one of them at least directed air at the starter motor as they don't like getting hot.

SQLGuy

All the aftermarket undertrays that I know of expect you to remove the ducts from your old undertray and install them into the new one. Only the OEM tray comes with ducts.

We've had a few pro/con discussions about undertrays here before. Yes, they require an extra 10 minutes or so to remove and install, on the other hand, the story of the guy who lost his alternator belt due to a plastic bag on the road getting tangled up in it makes me think the 10 minutes is worthwhile.

FredR

Seems the jury is still out on the purpose of these ducts. I wondered if maybe they were designed as eductors to help get hot air sucked out of the engine bay or perhaps move more air over a specific component/s for a bit of additional localised cooling.

Without seeing these in the flesh a bit difficult to evaluate.

Thanks for the inputs

Regards

Fred

Leon Speed

I think they suck hot air from or blow cold air onto the exhaust manifolds.

Rob Edwards

Sounds like a job for someone with a belly pan on their car, a lift, and a video borescope. Scary thing is that there are probably folks here that can check all three boxes....