ptuomov

Just to understand the behavior completely, is it correct that you switched to race gas at the same time as changing the crankcase breather configuration?

The reason for this being relevant is that (as I've learned first hand) knocks pressurize the crankcase and worse windage and oil ejection problems. A system that works perfectly without knocks can be overwhelmed when knocking. Higher octane race gas will reduce knocks and therefore make the crankcase breathing problem much easier to deal with, especially on a fundamentally well sealing engine like yours.

jorj7

ptuomov,

I've been running race gas off and on since 2008 to control knocks, but stopped when I installed the water/methanol injection system in 2011. With the water/meth system I was getting less knocks then with race gas (and it's cheaper to run). I ran 3 races that way until they banned water/meth injection last year. So I went to 100% 104 octane race gas for the 2015 SSCC event. This year they allowed water injection, so I went with a 25/75% mix of pump to race gas mixture. We saw a few knocks on our "tuning" run when we were running a 50/50 mixture, so added some more race gas and called it a day.

So a far as I know we've (Bill and I) have adjusted the fuel and timing to keep the knocks at a low level since we installed this engine in 2009, so the level of knocks should not be a factor in the new crankcase breather system which I installed in 2014. But since I haven't done extensive testing on individual upgrade/modification I can't give a definitive response to if the crank case breather issues were addressed by the race fuel or new components, but I can say that I think they made more of a contribution then the fuel type.

__________________
George
90 S4 Grand Prix White (Murf #5)
94 GTS 5-Speed Midnight Blue
06 Cayenne S Havanna/Sand Beige (PASM)
http://928.jorj7.com

jorj7

Hello All,

Here is my "PR" photo of this event:



as well as a speed to distance graph from the GPS of the run:


(this contains some proprietary information, so don't tell any one

__________________
George
90 S4 Grand Prix White (Murf #5)
94 GTS 5-Speed Midnight Blue
06 Cayenne S Havanna/Sand Beige (PASM)
http://928.jorj7.com

ptuomov

Good to know.

GlenL

209 is insane! Congrats on the awesome run.

What's the RPM, final drive ratio and tire size to get that? What's in the rotating assembly? (Link?)

jorj7

Glen,

I'm running Michelin Pilot Super Sport tires, 265/40ZR18 (101Y), on 997 Carrera III wheels with stock S4 rear wheel assemble and brakes. The transmission is for an '88 928 S4 auto, so 2.2 final drive ratio. At top speed I was turning 6010 rpms according to the LM-1 logs and 209 mph according to the GPS logs. If you do the math, ((((Dia * 3.14 / 12) / 5280) * 60) / 2.2) * RPM, that should be 213.6 MPH using the manufacture's tire diameter of 26.3". But since the tires were used in last years race, they are a little worn. Also, as you know, with tire expansion and slippage, the actual speed can vary from the calculated speed.

Hope that answers your questions.

__________________
George
90 S4 Grand Prix White (Murf #5)
94 GTS 5-Speed Midnight Blue
06 Cayenne S Havanna/Sand Beige (PASM)
http://928.jorj7.com

GlenL

Thanks! My missing link was the low ratio on the automatic.

mark kibort

amazing .... great job George!
209..... wow!! and it looked like over 200mph for about 10 miles too! "Bonneville" who???

jorj7

Thanks Mark,

And welcome back.

__________________
George
90 S4 Grand Prix White (Murf #5)
94 GTS 5-Speed Midnight Blue
06 Cayenne S Havanna/Sand Beige (PASM)
http://928.jorj7.com