Twin Turbo S2?

[Glen Chamberlain]

Just thinkin out loud here guys but i was day-dreaming today (nothin new there then! ) and i had this idea for people who were thinking of building a custome exhaust header?
Why no make it carry two stock turbos? or RS2 ones? Would this be realisticly pheasable? or just a waste of time? Just thougth that it may help spool up with two small turbos rather than one big one? I maybe missing a huge point here but i cant seem to find a big reason why not?

Yeh you would need two wastegates and maybe two control valves etc etc. but... Well, enough waffle, what do people think?

[Josh-stateside]

audi had a twin turbo 10v 5cylinder rallye car

[Sweeper]

The biggest problem such ideas face is proper ECU.

But with such a genius amoung us(who said Mihnea ) I believe it's quite possible (if you will find place for 2 turbos).

[Floddy]

I just don't have a clue about how the exhaust manifold would be designed... Three to one turbo and the other two to the second turbo? Or perhaps a 5-1-2-system?

I know that the IMSA had one outlet per valve, so perhaps if you use that head and took one outlet per cylinder for turbo no1 and the other five for turbo no2?

Five cylinders are a bit special to deal with in many ways, but i love 'em!

[Glen Chamberlain]

how about 5 turbos of the little Smart car thingies?

[Floddy]

If i were rich....

...I would go out to my big garage, take one of my 10 S2s, buy a load of smart turbos, and tell my servant "Desmond" to go buy some stainless pipes

But I ain't rich, so i guess I never gonan see that conversion!

[Greg_S]

Depends if u go for sequential turbos or two just the same.

Sequential u can have one which spools up quickly then it gets bypassed later for a bigger turbo.

gets very complex though.

But in my opinion the less moving parts the better, less to go wrong

[Floddy]

Talking about sequencial, check this out; (not an audi but...)

http://www.hilmersson-racing.com

Download the movie clips...I LIKE IT! Dispite the fact it is an opel(vauxhall) with a volvo engine.

[Josh-stateside]

floddy is this your car?

Floddy is this yours?http://www.danneeklund.nu/adde.htm



I druel watching those videos..

[Floddy]

Nope, not mine. Nice colour though!

[Pisobiker]

Apart from sequential turbos (which need bypasses both on the exhaust and the intake), putting two turbos on one manifold could be possible.
For ease of tune up, I think the need would be of twin turbos with both cold sides and hot sides pressures balanced.
Exhaust header could be manufactured with two collectors being fed the first by cyl.1-2 and half of 3 (with a divider) and the second one with cyl 4-5 and other half of 3 (so the two collectors will communicate through cylinder 3 runers, and pressures could be balanced).

Only problem is choosing the right turbochargers:

If you put two k24 you'll have about 540-550 hp top end flow capabilityes but will still have only about 1.5 bar max boost available (which is top manageble by them) so that you will never get that much power with them on a 2.226 L (even if you had 1.5 bar boost @ 7500 rpm that would probably make someting not over 420-430 hp only).
And boost treshold presumibly could be in the 4500-4800 rpm range.

If you put two RS2 turbos you'll have about 700-720 hp top end flow capabilityes with 2-2.2 bar peak boost (which isn't low but still not enaugh to reach that much Hp at 7000-7500 rpm). Boost treshold would presumibly be in the 5800-6000 rpm range :eek2:

For reaching lets say 550 hp the two turbos should have same flow capabilityes of the k24 cold side but with 2.3-2.4 bar peak boost and still about 2.0 bar when close to the choke line.


Marco

[Mihnea]

Well, my opinion is that if you do this, you'll have to use very small turbos... IMO, K03s out of 1.8T engines can do 225HP when pushed to the limits and with good intercooling and exhaust system. Or, 2 K04 turbos out of S3s??? The K04 can go as high as 270 HP....

thx to Sweeper

[Pisobiker]

Mihnea, but what about boost?

I mean, ok for total flow capabilityes, but on a 2.226 L engine to make 500 hp wouldn't you need to have something around 1.7-1.8 bar boost @ 7000 rpm?
So this means the two turbos will have not only to flow an air mass enaugh for 250 hp each, but they need, at that flowing rate, to still deliver 1.8 bar boost each.

Which turbocharger could be capable of this performances? don't have k04 map, but the K03 and K16 will make only 1.6 bar peak boost and 1-1.1 bar at about max flowing capabilityes (choke line).


Marco

[Mihnea]

Ummm, yeah, you're right Marco....

I quite frankly dunno, but if it were just me, I'd build a sequential turbo setup with a k14 or a diesel 5 cylinder K24 for low RPM performance and a K27/29 for high RPMs. The diesel K24 should be able to give boost from 2000 to 4000 (well, not 2 Bar but it will still be better than nothing) and then after 4000, a K27/29 can do it IMO....

Or a hybrid setup with a blower until 4500 and a K27/29 for high revs.... or it might be even better to use a K27/29/31 on a tubular manifold, 600 HP are possible if the K27 hot side is big enough...

But that's just a thought, my next turbo will be an RS2 hot side and a K27 cold side, boost from 3000 (2 Bar) and 1.3-1.4 Bar at 7000 should be enough for about 400 HP and about 600-650Nm with RS2-like low end performance...

[Pisobiker]

Originally posted by Mihnea


....Or a hybrid setup with a blower until 4500 and a K27/29 for high revs.... or it might be even better to use a K27/29/31 on a tubular manifold, 600 HP are possible if the K27 hot side is big enough...

yeah... I'm already working on that...
Pretty slowly, unfortunatly, due to almost complete lack of time (and money....), lately

At the moment I'm waiting for the blower's inlet and oultet ducts to arrive from the States...
Then some big working on the intake ducts and bypasses will need to be done... together with some mods to make everything fit under the bonnet


Marco