Can you have a look at your undertray?

[brad]

The undertray of my 2008 1.8tsi manual is only half-length & has a couple of NACA ducts on the passenger side - I assume to cool the gearbox.
It looks approximately like this (this is leading edge pointing upwards):


I'd never given this much thought but was looking at later model petrol vRS and noticed the undertray went right back to the crossmember.

I figured this would be a good thing for aerodynamics & also noise so when I came across a cheap undertray from a golf diesel I fitted it (it appears Golf, Passat, Audi A3, A4, Jetta, Scout, Yetti, Tiguan & Octavia all share the same undertray dimensions).

The one I fitted looks like this with no NACA ducts (leading edge pointing downwards):


Can someone have a look under their vehicle & if it has the full length undertray tell me if it has the ducts and is it manual or DSG?

I suspect the ducting is particularly for DSG equipped vehicles but if it's common for the manuals as well I'll do some cutting & glueing & incorporate my half-tray ducts into the full tray.

[Lucas_R]

Both my Mk6's have the 1st tray you have pictured. (Manual Mk6's).

Several Mk5's that i have worked on also have the same tray. I have never seen the bigger tray.

[Brendan_A]

My mk5 Jetta tdi dsg has the full length under tray(2nd picture) and no ducts.

[NOO63N]

Looked, I have no undertray lol

[brad]

Interesting.

The one I have is from a MK6 TDI DSG.

Just for reference, the Scout has a metal undertray that can be retrofitted to all the other similar chassis vehicles. It's a fair bit of work though.

[tigger73]

My Tiguan has the longer undertray - may be related to whether they expect the vehicle to ever be driven off-road as the longer undertray will stop some of the dirt/mud coming into the engine bay.

It won't however stop rocks so if you were concerned about damage you're best to replace with a plate.

The shorter tray probably allows better ventilation/cooling perhaps. And you may be able to change the oil without having to take the tray off. Full length trays have to be removed first for obvious reasons.

Depends what you think you need I guess.

[Transporter]

Because less of the energy from the diesel fuel is wasted ( to heat) compared to petrol engines, they need more insulation around the engine bay to keep them at the operating temperature, hence they have the full tray. If you're fitting the full try to the tuned TSI engines and run the car on the race track or a hot day in "your" Sydney traffic watch out for the increased engine temperatures, but hey, the chances are that you'll be fine most of the time.

[Transporter]

My Tiguan has the longer undertray - may be related to whether they expect the vehicle to ever be driven off-road as the longer undertray will stop some of the dirt/mud coming into the engine bay.

It won't however stop rocks so if you were concerned about damage you're best to replace with a plate.

The shorter tray probably allows better ventilation/cooling perhaps. And you may be able to change the oil without having to take the tray off. Full length trays have to be removed first for obvious reasons.

Depends what you think you need I guess.

Try tray is more open at the back in the Tiguans than in Golfs and Octavias, so the heat can better escape from under the bonnet.

@ Brad, I would be checking under the bonnet temperatures before and after the mod.

[notflyingscot]

Our 4/12 build Superb 1.8 (with everyone's favorite DSG) has that short tray with the two NASA ducts on the nearside.

[brad]

@ Brad, I would be checking under the bonnet temperatures before and after the mod.

I think you've nailed it Miro. Under normal driving probably fine. Temp range where i am at the moment is 0-22 so quite benign. I'll pay extra attention as our crap summer approaches.

Most likely will cut a section out of the full tray where the ducts should be & attach the half-tray underneath if the profiles match.

I don't race track but traffic may be an issue.

[brad]

Our 4/12 build Superb 1.8 (with everyone's favorite DSG) has that short tray with the two NASA ducts on the nearside.

NACA = National Advisory Council on Aeronautics. They pre-dated NASA.

[notflyingscot]

NACA = National Advisory Council on Aeronautics. They pre-dated NASA.

Bloody auto spell checkers!☺

[brad]

Bloody auto spell checkers!☺

Don't you hate that!

I need glasses for reading but rarely have them with me when I'm out & about. Some of the txts I send are really weird.

[Fourwinds]

Sorry for the late reply Brad but been a bit wet to be crawling under the car.

My MY13 VRS 6 speed DSG has a full length under-tray with NACA Ducts. Well I am taking a punt that the two holes in under-tray are the ducts you are referring to.






Cheers Fred

[brad]

that's them - thx.

I'll model mine on that - best of both worlds