Turbology paper revised

[S2central.net]

Some more hard sums. Enjoy !

http://s2central.net/Turbology_v2.pdf


Cheers,

Paul

[Mihnea]

Looks and sounds good

Good job Paul!

Cheers,

Mihnea

[Greg_S]

Nice one, makes some interesting reading. I will have to read thru some of my books again to refresh myself.

Greg

[Jamo]

Turbo UrS4

Came across this, don't quite get what he's trying to say in the last paragraph, anybody put it into english?


Is the hybrid K24/K26 turbo the same as the RS2 turbo?

No. The RS2 is all K26 turbo. I've had a couple dozen of RS2 and RS2 Competition turbos apart in the past 6 years. The hot side is based on the smallest of the K26 series housings, with a Porsche specified hot side wheel, and the appropriate milling of the housing (which results in a slightly larger downpipe opening). The center section is stock Audi K26 WC, and the cold side is a K24 cold side housing with a K26 cold side wheel. The RS2/Comp both use the larger K26 shaft for the wheels. The RS2 Competition uses a larger cold side wheel and housing, the hot side stays per early RS2. What throws most folks off, is that KKK left the K24 designation in their part numbers on the cold side tag.

The actual answer to the years of the K24 cars in the US is up for some discussion. The Audi "claim" is that as of 1989.5 (late MC dual knock MAC-14) Audi switched to the K24 turbo on all I5 turbo applications. This switch also "supposedly" came with a revised cam profile, flat flywheel (+ different TOB fork), and 2pc exhaust manifold. IME, 1990 was the ******* year for previous year pieces parts. I've seen 1990's with single pc exhaust, K26 turbos (but all have had the flat flywheel and the revised cam profile).

As of 1991 + intro of the 20vt cars worldwide, all Audi 20vt (I5 only - thought I'd miss that turbo cars except for the RS2, were K24 based turbochargers.

Maximum boost to the K24 is altitude corrected at 16psi. At 3200ft the 1991> stock 20vt cars lowered maximum boost threshold to prevent overspin of the turbo. You guys with modded 20vt computers with K24 turbos should reread that last sentence.

Scott Justusson
QSHIPQ Performance Tuning

Also this website as well.

Audi 80 TQ

Thoughts, comments?

[S2central.net]

Jamo - What Scott is eluding to is the fact that these cars have altitude compensation in the ECU so that the turbo doesn't go nuts trying to develop (say) 1.2bar with thin ambient air. Turbos don't like altitude period. Plug some very low air pressures into some key 'turbology' equations and you should see why.

Mihnea - Glad you like it so far... would value your comments. v3 is already in the works with more background info and a glossary of terms etc. I need some help with decent calculations for helping select the best 'hot' side...


paul

[audiman]

Nice work Paul :s Will read it again when i have more time, but glancing through it almost made some sense. Basically, i have the wrong turbo and IC setup LOL!!! Time to change things about me thinks

[APNess]

Mihnea said as much about my turbo too Tom (same as yours k26/27) - inefficient at high rpm I think When I get me *** in gear will lower those boost temps, just been busy this week. Also a deeper intercooler (maybe slightly longer too) might help (so that it still fits in the bumper - car gotta look standard).

Mihnea was right about another thing too - the slight hissing at 1.9/2.0 bar on mine was a split pipe on the ECU - that'll be replaced too, but I'll have to wait till September for the stiffer spring/remap.

So with regards 380-400hp, and similar torque, whats the best turbo - still RS2? Or a Garrett job? Might swap mine for an RS2 job at some point...

PJ

[Beetie]

Look's top draw effort mate! Good explanation.... even I understood!

[Mihnea]

**** me if I know why it is so guys, but basically, Paul's turbo, running less boost (1.9-2.0 Bar peak dropping to 0.8-0.9 at redline) than what Sal's is for instance (Sal: peak at 30+ psi-dunno how much, the gauge goes off the scale- and 20 psi at redline) heats the air much more than Sal's is. Paul's turbo was doing about +33 degs C above ambient temp increase in the IM, Sal's was only doing +27. Same IC and better DP on Paul's car also....

Tom's even a bit worse as his is pushing 1.1 bar at redline.

A few weeks after I'm back from the yanks, I'll be tuning a K26/27 with 3072 compressor wheel and #8 hot side in my mate's S4, we'll then be able to see how good this one is, and I do suspect it will be, as it's the same as the ones MTM use for 380-420HP stages...

Cheers,

Mihnea

Mihnea said as much about my turbo too Tom (same as yours k26/27) - inefficient at high rpm I think When I get me *** in gear will lower those boost temps, just been busy this week. Also a deeper intercooler (maybe slightly longer too) might help (so that it still fits in the bumper - car gotta look standard).

Mihnea was right about another thing too - the slight hissing at 1.9/2.0 bar on mine was a split pipe on the ECU - that'll be replaced too, but I'll have to wait till September for the stiffer spring/remap.

So with regards 380-400hp, and similar torque, whats the best turbo - still RS2? Or a Garrett job? Might swap mine for an RS2 job at some point...

PJ

[91_S2]

Nice work Paul! Well done.

[audiman]

Mihnea thats what i am gonna be using later on this year, WHEN i do my rebuild. Also gonna get me one of those MartinJS IC's too!! I was qouted about 200 quid to change the turbo and rebuild it at the same time.