I guess it's easier to change the oil, inspect things etc, so who on here does not bother with one?

Advantages and Disadvantages?

 

ive been running without one for around 4 years> my exhaust headers(wrapped) started to melt it so i removed it.

 

i'v never had one just a large metal sump gaurd!!

 

i got one, but don't know what it's for.

 

Neither of my impreza`s had one

 

Never had one on my96 JDM WRX and it is fine without it imo.
Suppose a disadvantage would be that the standard manifolds with there metal heat shields may heat up in use & when the car is driven through a puddle there may be some risk of the heat shields welds being damaged with the sudden change in temperature.
Advantage would be easyier to inspect, change oil, filter etc plus possibly helping more air cooling of the sump etc

 

My Legacy had rectangular holes on the front of the undertray covered with rubber flaps.These flaps were only attached on one edge so I assume they are meant to bend inwards as speed increases to let more air under the engine.Anyway, I removed the flaps to increase airflow at all speeds.

Is this the same system as on the Impreza ??

 

an undertray,doesnt it say in the subaru handbook that as soon as you buy the car you should remove this and throw it away.

 

Mine has ran for years without one without issue.

 

Most manufacturers run undertrays to aid in undercar turbulance.
Basically improving the cars aerodynamics at speeds.
Interesting fact....... the e60 m5 undertray system allows the car to maintain 124mph with 12 less horsepower when compared to an e60 without an undertray system.

 

dont have one at the moment, but intend to fit a Laile under panel in the near future!

 

Both my impreza's had them on

 

Been told it will aid underbonnet cooling a LOT without mine.

 

I haven’t thought about removing mine, I assumed that it aids down force due to smoother air flow underneath and protects the engine from crud flying up from the road.

 

The front subframe on my 99 JDM STi is pretty shocking and needs replacing. This is due to it never having had it's undertray fitted.

I have sourced on and it's going back on. If it's good enough for the WRC cars it's good enough for me.

 

+1 could smell the plastic burning and was only when I changed the oil I clocked where it had melted the undertray.

Was happy to keep it on but the FMIC pipe work put a stop to that.

I understand the oil temp is helped along with the the rest of the cooling aspect without?

My only fear now is the speed humps etc.

Steve

 

when i bought my wrx it didnt have one, MY95,so i fitted one from my previous my00.
Wouldnt be without it,the amount of crap it stops from splashing up etc (i m a clean freak)

 

Thanks folks for the feedback.

It's really the melting issue that I will be grappling with, so anyone had tubular headers and an undertray without issue then? Thinking about different materials too, can you get carbon ones? Would they also melt?

 

taken them off every impreza ive owned as they just collect dropped tools and bolts etc.

however will be refitting for winter now i have tidier car as dont want sump etc to start corroding with salt/stone chips.

 

removed mine , but do have a sump gaurd for a little protection

 

Phil, who makes that sump guard, and can it be fitted with tubular headers and an FMIC?

 

My old car didnt have one, the new one does .. Cant see a plastic guard stopping anything that would course damage anyway ??

 

not sure who makes them, my car now has a gt fmic and it fits perfect, dont know about the headers as i have standard ported ones

 

Undertray helps in extracting air from the engine bay. Its designed to send air down the gearbox tunnel, undertray will help this. One of those counter-intuitive things like removing classic bonnet vent blanking plates.

I run mine with wrapped standard STi headers with no melting problems and unless you've got some oversized tubular jobs, I can't see a problem.

If your oil temps are high fit an oil cooler.

 

I have discussed this many time,used digital temp gauge in different places under bonnet with and without belly tray,with tray my engine ran up to 8 deg c cooler.Subaru would not have fitted it without a good reason.Litchfield run over 400bhp with a top intercooler they say without belly tray top mount do not work very well !

 

Been trying to find an article writen by an american engineer,he set about proving the importance of belly pans,the logic was as your car his air at say 80mph it gets split in three areas,the largest mass goes over the top speeds up causing down force,the next mass goes thro grill etc cooling rad,the final volume gets squeezed under the car speeding up creating low pressure as it flows out behind.With belly pan on the air gets drawn down thro intercooler,air gets drawn thro rad flows past turbo reducing underbonnet temps,it also cools transmission casings.When this hot air exits at rear of car it mixes with cooler causing a depression ie downforce,so there you go

 

i have the under tray fitted as it was from the factory. but thats not to say i would drive my car if it wasnt on there

 

Anyone using tubular headers with the tray and found a way to avoid melting?

 

put a metal one on?

 

Never had one and didn't even know it should have until a year after I had the car, never had an issue and in the end the gearbox undertray went too