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Engine performance simulations 924 Turbo
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 1522
Location: Somerset, UK

PostPosted: Tue Dec 20, 2016 9:53 pm    Post subject: Reply with quote

Hi Cedric. Would be good to see the series 1 2470#6 compared with the later spec turbos too.
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1980 931 - forged pistons, Piper cam, CGT turbo, 951 ducted FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife LSD
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CÚdric  



Joined: 27 Aug 2004
Posts: 1663
Location: Sweden

PostPosted: Tue Dec 20, 2016 11:40 pm    Post subject: Reply with quote

Carrera RSR wrote:
Hi Cedric. Would be good to see the series 1 2470#6 compared with the later spec turbos too.


That could be possible since the map is around, but its so crap its painful to put the work into it. But it would be interesting to see just how a std 931 responds to the different chargers. The variations on the turbocharger specs for the 931 is quite big, maybe they were trying around a bit, on later models its much more thought through. My s1 engine had this #4/2664 turbo as a replacement turbo for example..

Overspeeding a turbo on short stints like street driving is probably ok, but for a track car i would definitely go bigger.

Looking at the OEMs is a good guide, we chose our turbos wisely:). Porsche went from 2667 to 2670 when the 951 went from 220 to 250hp, the 924GTS also has the 2670 for 245/275 hp. The Lancia delta s4 group B homolgation model has 2670/#6 turbo for 1,8l 250hp, a good indication aswell. But sure, we dont need the margins that the oems have, for altitude, longetivity, dirty air filters etc, but its a good guide.
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gegge  



Joined: 27 Jul 2007
Posts: 1018
Location: Sweden

PostPosted: Wed Dec 21, 2016 2:58 am    Post subject: Reply with quote

morghen wrote:
Uh, interesting. So you're on holiday.
Can you do a K27 compressor on the same model as well?


https://goo.gl/photos/8SgvAzq3ZSdUjZNu5

https://goo.gl/photos/zB8D3XNVA1TJefC28


Or the more common 911 compresorwheel:


(I know the 2670 is hard to beat in the 200-300hp powerband - I am looking beyond )

It┤s a pity that there┤s no housing to match the RS2 wheel:

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924 turbo -81 Carrera GT clone LSD Coilovers
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black with low ET "Phonies"
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 1522
Location: Somerset, UK

PostPosted: Wed Dec 21, 2016 3:51 am    Post subject: Reply with quote

Mittelmotor have gone upto 400bhp with a K26#6 on their GTS spec racers but haven't divulged which compressor they are using. All Michael said was that it was 'matched' to their motors flow/back pressures. So the #6 will give more with the right compressor. Would be great to see if any modern compressor designs are the 'perfect' option with good low end spool and top end efficiency.
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1980 931 - forged pistons, Piper cam, CGT turbo, 951 ducted FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife LSD
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 1522
Location: Somerset, UK

PostPosted: Wed Dec 21, 2016 3:57 am    Post subject: Reply with quote

CÚdric wrote:
Carrera RSR wrote:
Hi Cedric. Would be good to see the series 1 2470#6 compared with the later spec turbos too.


That could be possible since the map is around, but its so crap its painful to put the work into it. But it would be interesting to see just how a std 931 responds to the different chargers. The variations on the turbocharger specs for the 931 is quite big, maybe they were trying around a bit, on later models its much more thought through. My s1 engine had this #4/2664 turbo as a replacement turbo for example..


Here's another question. Would a 2664#6 or #4 give better results on a 7.5:1CR S1 turbo v's its stock 2470#6? OR does the higher 8.5:1 make a difference on S2 turbos?

The GTS had 8.2:1CR. Mittelmotor run 8.0:1CR on their GTS spec cars.

Apart from potentially inducing det, does the CR make an impact on the turbo used?
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1980 931 - forged pistons, Piper cam, CGT turbo, 951 ducted FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife LSD
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gegge  



Joined: 27 Jul 2007
Posts: 1018
Location: Sweden

PostPosted: Wed Dec 21, 2016 4:52 am    Post subject: Reply with quote

A 2664/#4 will most likely outperform the OLD 2470/#6 in any respect. A tighter nozzlearea spool faster and a better compressor flow more. A 2664/#6 will of course have a better topend. The new K24 2470 is a completly different story.

A CR of 8,5 with good enginemanagement will make more power than 7,5 regardless of level of boost.

A non-intercooled 2470 with CR 8,5 and 1 bar of boost spells disaster though!

The 2670 can┤t make 400hp according to the map. It is out of breath north of 300hp and will not last long. I doubt a 2672 can make it, even it there are some very powerfull Audis out there.
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924 turbo -81 Carrera GT clone LSD Coilovers
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black with low ET "Phonies"
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CÚdric  



Joined: 27 Aug 2004
Posts: 1663
Location: Sweden

PostPosted: Wed Dec 21, 2016 8:02 am    Post subject: Reply with quote

The 2470 should never be used if you have the possibility to change, its a very ancient design compared to the others, looks like somerthing from the 60s.

400hp with a GTS turbo is nonsense, i thought they were FIA htp appK legal, that should put some serious restraints on the turbo choice.

Ive seen data from a certain rally GTS and the #6 housing do limit performance du to severe backpressure/knock limiting. But knock is of curse dependant on many other parameters, like cam (mostly echaust cam), and how your porting affects airflow pattern in the cylinder, which is highly critical, and of course compression and octance rating.

The 3072 is badass when it comes to flow, maybe i will give it a try some day..

I have LOTS of holset maps available, I can throw a similar sized but modern compressor on if you want
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 1455
Location: Not Detriot - NMI

PostPosted: Tue Dec 27, 2016 12:52 pm    Post subject: Reply with quote

I just wrote up a good post and my power flashed

long - short..

How are the 2667 and 2670 looking up to 1.5 bar?

How about the k26 turbine and turbine housing to 1.5-2 bar?
Assuming it was mated to pretty much any compressor imaginable..

The turbo shop closest to me said that they would rather bore my turbine housing to fit a modern chra of my choice, even bb, for a very reasonable price, than to try to find parts to rebuild my k26..
When do you think a #4 and/or #6 housing would choke assuming it is bored to anything possible..

Would the oem exhaust manifold choke? When?

Gegg, similarly, I believe you could have a k26 compressor housing bored out for a rs2 wheel if you wanted.. 98% sure..
I think they told me $125 or something close to bore housings..

rs2 is kkk correct?
Are you sure it won't bolt on? Why? Backplate problem?
It may be easier/cheaper to modify an rs2 backplate to fit the whole rs2 compressor than bore a k26 housing to fit an rs2 wheel..
If the shaft diameter is the same or smaller you'r in business...
Bunch of ways to skin a cat..
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Mike9311  



Joined: 14 Dec 2004
Posts: 648
Location: Chicago-ish

PostPosted: Wed Dec 28, 2016 12:34 am    Post subject: Reply with quote

why not machine a billet front section for the 3072 to mimic the 924 circ valve or is it the center section that needs attention? This leaves the K27 comp housing in place. Probably not the easiest path depending....
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1980 931 ...off with the cobwebs
1982 931 Entwicklungsfahrzeug
1979 924 NA M471/M481 / ohne M650 Herausnehmbares Dach
0.5 1982 931 smashed parts car
1982 931 parts car?
1980 924 NA (R&D lightweight)
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 1522
Location: Somerset, UK

PostPosted: Sat Mar 11, 2017 7:12 pm    Post subject: Reply with quote

Anyone done away with the recirc valve and no additional BOV?
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1980 931 - forged pistons, Piper cam, CGT turbo, 951 ducted FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife LSD
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Mike9311  



Joined: 14 Dec 2004
Posts: 648
Location: Chicago-ish

PostPosted: Mon Mar 27, 2017 1:45 am    Post subject: Reply with quote

Carrera RSR wrote:
Anyone done away with the recirc valve and no additional BOV?


Isn't that hard on the turbo as well as boost coming in later???
_________________
1980 931 ...off with the cobwebs
1982 931 Entwicklungsfahrzeug
1979 924 NA M471/M481 / ohne M650 Herausnehmbares Dach
0.5 1982 931 smashed parts car
1982 931 parts car?
1980 924 NA (R&D lightweight)
1982 931 WB wana-be GTR race car
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 1522
Location: Somerset, UK

PostPosted: Mon Mar 27, 2017 8:24 am    Post subject: Reply with quote

Mike9311 wrote:
Carrera RSR wrote:
Anyone done away with the recirc valve and no additional BOV?


Isn't that hard on the turbo as well as boost coming in later???


Nope and nope.
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1980 931 - forged pistons, Piper cam, CGT turbo, 951 ducted FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife LSD
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CÚdric  



Joined: 27 Aug 2004
Posts: 1663
Location: Sweden

PostPosted: Mon Mar 27, 2017 8:03 pm    Post subject: Reply with quote

Carrera RSR wrote:
Mike9311 wrote:
Carrera RSR wrote:
Anyone done away with the recirc valve and no additional BOV?


Isn't that hard on the turbo as well as boost coming in later???


Nope and nope.


Why would you get rid of it, its a simple device that is very efficient in doing its job.
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http://www.garaget.org/show.php?car=211
┤80 924 Turbo
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WEASEL149  



Joined: 19 Aug 2005
Posts: 592
Location: UK, Sheffield

PostPosted: Mon Mar 27, 2017 8:10 pm    Post subject: Reply with quote

*Can of worms nicely opened*
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 1522
Location: Somerset, UK

PostPosted: Mon Mar 27, 2017 11:58 pm    Post subject: Reply with quote

CÚdric wrote:
Carrera RSR wrote:
Mike9311 wrote:
Carrera RSR wrote:
Anyone done away with the recirc valve and no additional BOV?


Isn't that hard on the turbo as well as boost coming in later???


Nope and nope.


Why would you get rid of it, its a simple device that is very efficient in doing its job.


Why not? Its a simple device potentially redundant to my needs. Why need it?
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1980 931 - forged pistons, Piper cam, CGT turbo, 951 ducted FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife LSD
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