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

Just a quick heads up getting back to angle skimming, and the care needed if anyone is thinking about doing it in the quest of power>

The head bolt hole to the right of intake port number 3 is live to the oil way gallery supplying tappets.
This could have two effects if care is not taken, on milling the holes to 90 degrees with the head face again, after angle milling great care should be taken in order to clear gallery of any chips that WILL without a doubt block the feed to the surrounding buckets.

The only way I can think out of this is to remove both alloy gallery plugs either end of head and flush gallery's with a suitable solvent/cleaner.

Also, another problem one will face is the ability for the head bolt head and washer to re-seal on the now elongated hole in the counter-bore area. If this is not sealed OR a small gap exits beside washer(not sure if washer will fully seal and cover) all oil pressure to head will be lost.

Perhaps the side of the hole could be tigged up before the 90 degree hole re-alignment commences.

This is also why head bolt number #4 on the front row always comes up oily. The supply to head is fed up through this ''larger than the rest'' bolt hole.





Sorry for going off topic a touch but I feel its worth a mention here as angle milling has been discussed.

 

By skimming under a 2 degree angle means 3 mm will be removed from the combustion chamber at one side or 6 to 7 cc reduction in volume

Audi has tried 30mm exhaust valves but lost some hp and went back to 29.5 mm
At full lift there will be about 0.5 mm more wall clearance
or they have to shift the head slightly on the block to gain another 0,5 mmor more ?
IMO the biggest gain is in the piston , lower dome, weight reduction ,extra flow


Peugeot 406 works engines build by Pipo

300hp (1996) 310 hp(1997) 315 hp (1998 ) @ 8300 rpm
26 mkg /6500 (96) 27,5 mkg / 7000 rpm (97)

 

A head supposedly off an 'Audi S1 road car, 1988' (which is what?)



- cam drives are helical (to limit noise).

Click

Just a thought to ask how much in the way of similarities are there between the 16 4cyl & 20v 5cyl heads?

 

weird, I thought the stw valvers had the drive at the other end of the head, this has it at the belt end. Theres definitely not enough room on any 16v head to get gears in there. Either way the inlet cam is going the wrong way. Must make cam selection a headache.

 

Surely it doesnt matter which way the cam rotates as all its doing is pushing open a valve?

 

Those cams are clearly designed to work that way round, however if one were to just attach gears to regular 16v/20v cams the inlet would go the wrong way. If a cam is designed to rotate one way and you were to reverse it the lobes are all in the wrong place. The synchronisation between cylinders is all going to go to pot.

It was just the observation that that inlet cam must be fairly special as all other 5 cyl inlet cams will have the cylinder sequencing going the other way.

 

lol, because they would be 'off the shelf cams'.. not.. I think this was taken into account, when they were designing the cams somehow!

 

Ah of course. I didnt consider inter inlet valve timing just profile and assuming it would be symmetric.

 

Yes, the STW valvers do have the drive at the other end:

 

A few more bits of info for the thread:

 

And some full-on technical stuff!

 

This is very interesting and reminds me of a chat in the dim and distant past (2L 20V's being restricted for cam profile by the size of the followers)

The VW 2L 16V engine appears to have the capacity to fit very large diameter cam followers - 37mm are available - M3's have a similar size

Seems to be larger than many engines

http://www.arrowprecision.co.uk/followers_stock.php

Maybe they got away with the relatively poor cyl head design by having the ability to run some very daft cam lifts......

 

Some good info there Chris. I presume the Piper source is John Crabb the technical director there?

Rob, I have read the same thing regarding 20 v's, the lifters are not big enough to run big cams.

My question in general is, do you seriously think the head design is that poor? What is essentially the same casting won the BTCC. Just because we amateurs haven't reach "big" numbers doesn't indicate a poor design in my opinion. I have read lots of "accepted wisdom" on many different forums regarding tuning these engines and I would suggest much is B.S

What I would point to is a lack of true development over the years with people too willing to accept that this is best or that is best. I guess ultimately it comes down to the amount of 's poeple were willing to spend when these engines were relatively new.

 

Yes, it's Jon Crabb - they did an interview / business visit in that issue.

On 5-valve lifts versus bucket diameter, base circles can be reduced to an extent to get greater lift?

Some interesting information, albeit non-Audi.

I think this is TWR BTCC Volvo data, but it's marked "V10":

Inlet valve:

• Diameter - 39.50
• Lift - 15mm

Exhaust valve:

• Diameter - 33.20
• Lift - 13mm

Dated June 1999. Half a chance it's Arrows F1 (V10 = engine or version 10? 39.5mm is a lot for inlets on a 2.0, esp a 5-potter)

 

Yes, you can do this to an extent, but if you coinsider they are only 24mm that does not leave a lot of scope for radical profiles.

That is massive for a 4 valve per cylinder engine. I think you would need something approaching a 94mm bore for that. On a 5 cylinder engine that would translate into something like a 58mm stroke. Very short. Could be right but it sounds too big to me...

 

Yes I do, from a conventional wisdom standpoint: If you look at 16V engines in some top race cars, whats obvious is the width of the cylinder head (a VW 16V looks almost like an 8V head by comparison). This is to get plenty of angle between the valves and fit the largest valve in for a given cylinder bore. Also the bore/stroke ratio is not the best.

As a base-spec engine, there are much better designs out there (see how easy it is to get 200hp from a duratec or a redtop).

But I guess if you invest enough in development time, you can make even a poor design pretty good.

Whats interesting though is little gems like the size of the lifters. Maybe this gave massive scope for cam development that engines with better bore:stroke ratio and mahoosive valves couldnot use, and thus, levelled the playing field.

Maybe conventional wisdom is wrong, and what really matters to make a valver fly is not valve area, but valve lift.....they are both affecting airflow after all.

 

I would agree that the design is not perfect, bore to stroke ratio is not ideal, at 2L capacity especially with the lack of space for larger bores. My current area of concern is to do with combustion chamber shape (which ties into width of head), not actual flow numbers. Bit of a strange shape, and quite a large volume too. Strangely enough, when developed, exhaust flow is not an issue, even with the vertically inclined exhaust valve it still comfortably flows 75% of a fully developed inlet port.

As an FYI, my head flows the same at 12.5mm lift as it does with no valve so there is little point in me lifting any higher than that. Different engines have different lift / flow profiles, but in this concern my particular head this is very similar to an XE. Perhaps if you were going massive with the ports this would be different but I cannot confirm for a fact either way.

Regarding the ease of hitting 200 bhp with other engines, I presume this is just bolt on parts? That said, I did see someone hit 200 bhp with just bolt-ons with a vw 16v on here a while back...

 

http://www.sbdev.co.uk/History_files/History_EngineTechVauxhallXE.htm

+carbs/tbs and exhaust = 180hp

+cams = 200-225hp (tidied up head with stock valves)

All on a std bottom end.

I would say probably 20-25hp up on a VW 16V for similar add-ons.

Who has a 2L valver (atmospheric and no nitrous or similar) with a std bottom end that makes over 200hp?

 

super touring cars,are these the same spec? http://www.racecarsforsale.com/saloon-cars/audi-a4s-1.html

 

Didn't dub_nutta's make over 200 hp from 1800 or 1900cc??