Audi A4 BTCC / STW engine specs - 305 bhp from an N/A valver.

Well here's what the STW exhaust looks like:




If you want one:


http://cgi.ebay.de/Auspuffkroemmer-...le_ohne_Strassenzulassung&hash=item19c61e4138

A bargain at 500. If it had an extra pipe, I'd buy it for the 7A motor!

 

does it look to be welded? at pipe no.4?

 

Tris.

I think it is welded in lots of places, as it appears to be made from lots of small bits, to achieve the intricate shape?

 

welded as in broken?

 

Welded as in:

'How do they make F1 exhausts!'

 

Does this show more?

 

SEE where no3 and4 primaries meet the collector? at the junction of dull grey to shiney? It matters not really , just my pedantic hat was comfy the other day...

 

Thats where the pipes are flared and the pipe back joins it Tristan. Its to be shoved together in Daves picture. Thats why the shine is still on pipes, it would normally be mated together, and tack welded/wired to hold in place. Looking closer, its spring wired to hold in place, spot the little hooks either side of join, similar to the net pictures below,





BG

 

Dunno Brian , if 1 and 2 primaries were to be pushed together , the 4 of them wouldn't be inline at the head end. and if they were all pushed out , the other 2 would have the same shine. No matter anyhoo , I won't be buying it!

 

Seat Sport S2000 20V engine specs > WTCC / BTCC 2004/2005

85mm x 88.1 mm

CR 11/1

Valve lift 11 mm


Engine block 06A 103 021C bored to 85.00 mm

 

i've heard 13-14mm

 

so would we conclude that the FSi head offers a little more potential than the 20v? or are there other things in the mix

 

OEM bolts for head and main caps is very interesting!..

 

Yes , more valve area

 

Just to add some precision to HPR good description :

- CR and Valve lift, are the maximun allowed by rules (you can go to 13/13 but you have to add weight to the car)

- Crankshaft Minimun Weight is also didacted by the rules (A seat WRC crank Weight 11,5 Kg with 92,3 stroke)

- Rod and Main bearing are from the Audi 16v STW engine

- Airbox Back in magnesium is also from the Audi STW engine

- Injector are from the 1.8 T 225bhp !

 

Second Primera BTCC article


"Increased crankshaft flexibilty can all too easily offset the frictional gain of smaller bearings."

"Compression ratio closer to 14:1 than to 13:1."

One of the best technical articles on this type of engine I've read

 

Excellent article, Chris. Ties in with much talked about above.

Some things that struck me were:

1.75 rod to stroke ratio
36mm inlet valves
2 injectors per cylinder
4 : 2 : 1 exhaust
~13.7:1 CR

Basics, yes, but very very important. Some of these were / are possible on an 827 code engine, others less so (You can't physically get 36mm inlets in without moving the stem centres, if at all).

 

Agreed.

Of particular note for me is:

 

I think a lot of that can come down to combustion chamber shape. To get high compression in some engines you need huge "intruder" type piston domes to create the required compression, but that can lead to less than ideal combustion and burn rate and the advantage of the raised CR is lost.

Either way, the high CR most certainly worked on the Nissan. Sounds like the Primera had a "traditional" pent shaped chamber as has the XE, Pug 405 and Cosworth heads. It might also go some way to explaining why VW went some way to reshaping the combustion chambers by milling down the exhaust side of the cylinder head. Perhaps to try and reduce the combustion chamber volume and alter the shape a little, rather than increasing the exhaust port flow which is more than adequate for the amount of air flowed by the inlet valves. I am sure the answer will come out in time

 

I agree target was to reduce combustion chamber volume and get the lightest possible piston
with an almost flat crown