improving aerodynamics with OEM parts

[RedRobin]

Ric, I don't know. But some mates report of a reduction of 0.2 - 0.4 l / 100 km.
Maybe this seems to much, but that's what they told me.

Thanks Bruce that seems about 8-10% which over a tank could be 30-40 miles so not insignificant for the money spent on parts 

....I'm playing devil's advocate here rather than being a hater, but wouldn't such a fuel saving only occur on high speed, unrestricted autobahn types of journeys?

[Richn83]

Ric, I don't know. But some mates report of a reduction of 0.2 - 0.4 l / 100 km.
Maybe this seems to much, but that's what they told me.

Thanks Bruce that seems about 8-10% which over a tank could be 30-40 miles so not insignificant for the money spent on parts 

....I'm playing devil's advocate here rather than being a hater, but wouldn't such a fuel saving only occur on high speed, unrestricted autobahn types of journeys?

Thats why I asked for fuel saving at 130kph which is 80mph so that would be the saving on a motorway journey on the continent and roughly on a UK motorway.  And dont worry about the hater thing ideas need to be challenged or we would all still be living on a flat world at the centre of the universe! 
It's the way they are challenged which is the key 

I would think you could potentially make your money back on the parts with 10k a year of 60+mph driving assuming the savings Bruce mentioned.

[the bruce]

2 x 1K0 609 734 C
2 x N 102 854 02

 


For the parts 2a and 2b in the picture below (from A3 and TT) it will be best
to use the parts from above to fix the brake cable.

[laurent.d]

The idea of aerodynamics improvement  is good but I have to say that I a bit concerned with this panel closing all the sub engine bay.

Not because of oil temp. As cooling through the oil sump is minimal.
But what about eat released by the turbo and all the devises around it when runnig flat out as you have enclosed the engine bay and that air can't cool down behind the engine any more.
Ok there is a naca but it look rather small and desinged for a 110 Hp Bluemotion diesel car, not for 200Hp /350Hp benzine sporty car.

[vRSAlex]

The Octavia vRS's come with the full length undertray as standard.

As another example, the Leon Supacopa cars run a full length undertray and have no issues running 330bhp round a race track at full pelt.  Our GT3 Gallardo's also run a full length undertray with the only holes being for the air jacks.  They run 3 hour races with no heat issues.

[the bruce]

Thanks, Alex, for the information.  

Laurent, I had the same doubts like you for a long time and so
I fitted the engine bay panel last. When I started this mod more
than two years ago I first wanted to reduce the lift at the rear.

Then I have seen that the A3 3.2 has the same panel from factory
(and probably the R32 as well). So does Audi on all TT including
TT-S and TT-RS (a different one but similar completely closed).

Furthermore I talked with Benny at Raeder Motorsport and he
told me they use it on their A3 TFSI as well.
The Leon Supercopa and the very familar Scirocco GT24 even
have a completely closed and flat underbottom from front to rear.

Last, not least:

The air entering from front radiators now has only a few definated
ways to leave the engine bay passing the turbo charger to the
center tunnel.
I'd presume there will pass very few air to the wheel fenders because
there should be a high pressure area.

[laurent.d]

Thanks guys!!

I was wondering but I feel reassured thanks to your further explanations and experiences. I missed those points.


I will go today to order 4, 3 (i don't know if it will fit because of my Resonated Milltek) and the undertray.

But about undertray, I don't know which one to order as ther is many of them.

Do you know if lastest S3 have also theis long undertray?

[laurent.d]

Ok I just found out on ETKA that 1K0 825 237 P is the same ref for 3.2 A3 so A3/golf have the same shape.

May be it's what you mentioned but I didn't get it.

[the bruce]

Right. It's the same. Only TT is different.
Another thing:
The inner plastic fender is different Golf and A3 as you may know.
The Golf's one has brake ventilation, the A3's not.

I have cut '3' a little bit to fit the stock center muffler, but with the
smaller Supersprint I have now it would have fit without any
modification. I guess the Milltek res. is more like OEM in it's shape.

[laurent.d]

The Bruce does 1K0 825 235 AB is the same. I found your german Scirocco thread I understood it is what you mention but I'm not sure I get it right.

[the bruce]

I'd go for 237 P again. 

- Golf ball pattern
- 3rd NACA
- cheap

Don't forget the three metric screws. First clean the threads in the subframe.
Sometimes it will be neccessary to drill/cut the threads a bit.

[laurent.d]

I just come back from Audi dealer!!

Ordered:

A3 3.2 undertray  1K0 825 237 P
Tank deflector 1K0 501 713 D
Rear muffler deflector 1K0 825 206 A
And all the necessary screws, at least I think.

[RedRobin]

.
How much does all this undercarriage weigh?

[the bruce]

I never read of somebody posting the weights of these parts and I didn't
do this by myself, Robin.

The only chance: Laurent will do this job for us. 

- first the new parts
- after modification the old small engine cover


But I don't really care about this because it's very low positioned and this
stuff is just fibre reinforced plastic.
The engine bay cover is very thin though. And the rear parts don't do any
harm from the 'dynamics' view (unless acceleration).

[laurent.d]

I'll weigh new parts and old parts for you.

But I don't think it's very heavy.