Geoffrey

I run my race car for about 10 hours before changing the oil and the oil analysis suggests that that is about the extent I should go with the oil brand I am using. There are oil components like Zinc, ZDDP, etc. that are used up as the engine is run. Based on the oil analysis testing I've been doing, I feel that for my situaion 10 hours is about max.

We built a MoTeC controlled TT engine from various parts of a GT2, GT3R and GT3 Cup engine and it is installed in a 996GT3R chassis. We fought oil temps which were too high and had to find a way to add some significant oil cooling. We were seeing 250-260 degrees F when running at 1bar of boost. While this engine run some large turbos and runs to 8300rpm, I would wonder what the oil temps are on your street car mildly modified with additional boost. The high oil temps we experineced were no good for longevity.

It may be possible (just guessing, I have no data) that the oil temps in your engine were elevated which may have contributed to a problem with the big rod end. I would certainly have an oil temp gauge and monitor it.

Steve Weiner-Rennsport Systems

Tom:

Geoffrey brought up a LOT of very good points; some of which I'd agree with and some are open to debate,... Some of his observations reflect what we have seen here, as well.

The rod bearing issues in 911's are well known by long-time professional racing engine builders and this is not a recent development. This goes back to the mid-late sixties and the fix was developed back then to aleviate the less-than-ideal oiling to the center of the crank. Porsche A.G. didn't figure this out until they ran the first Indy engine at the Brickyard (the 6-cylinder one) and thats a separate story.

I would tell you that if the bottom end is properly prepared, equipped with the right parts, and you use a good oil, you should not have any further trouble unless you are running a LOT of boost using pump gasolines.


Geoffrey:

I'm not surprised at the oil temps you saw with that hybrid, MoTeC'ed TT engine. The last two generations of GT-3R N/A motors also ran very hot (220/220) and the newest version has much improved water circulation in the cylinders and heads.

tkerrmd

Thank you both for your expert advise and opinions, they are very helpful

tom

KPG

Tom , this is why we have spent much time and money with Kevin on these upcoming stg4 motors. Oiling, oiling,oiling.... You cannot imagine the detail that has gone into the oiling mods for this engine. The crank, case and rods all have been modified to increase oil supply at high rpms. Special bearings, custom clearancing of the rod bearings for every journal and many more details that add to the overall package.... the level of detail is staggering.

tkerrmd

well I will run this engine stock until the 2 year warranty is up (hopefully) then I know where to go for the rebuild!!

03-turbo911

Tom, I'm so sorry to hear about your engine problems. Tempting though to do a build more suited to your use. Good luck with the decision.

tkerrmd

Thanks Khalid!!

Boulder GT3

Thanks for taking the time to post this thread and keeping people updated on your logic and the path you are going down. You do so with little upside for youself and the usual internet second guessing.

I think many wonder what they would do in the event of a catostrophic failure with a relatively new and pricey car. It's helpful to read how it plays out.

Good luck.

m42racer

""""The rod journal/bearing got so hot that the drag on the rotation of the crank caused it to snap in half. """
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kevin@ultimatemotorwerks.com

I've been know to disagree with many statements posted here. Not to disagree just to disagree, but really, I've heard of "stretched statements", and this has to be up there with the best of them.

I would re evaluate the cause of failure before spending anymore money on another engine. Just might save this engine from the same.

Kevin

Simon, I'll have the engine soon in my hands and we will see the bearings. With the bearing transfer on the rod journals heat was/is present. All is speculation until one has all the parts on a table. I can check all the rod journal measurements.

Since your family has the metalurgical XRAY equipment, you can donate your services to examine the crankshaft..

tkerrmd

thank you for your reply that was why I posted this, It probably happens more than talked about, I had never heard of it before and was hoping I and all others my learn something from my misfortune.

tkerrmd

Hopefully, when the coroner does the autopsy we will all learn something.

This happend on sunday morning the first instructor run group of the day. It was the first hot lap after two yellow laps.
The car just had a new JIC race suspension and hoosiers put on the week before.
on saturday the car ran perfectly except ran out of gas unexpectedly and came to complete stop on the track and needed towed in. gased up and ran another session without problem.
remember the engine had a REVO stage 2 flash and straight pipes on 93 octane. LWFW.
Oil and filter were changed after every event for the life of the car.
the computer had a type 2 overrev within the hour before the crank broke.
To my knowledge there was no speed shifting or missed down shifts (this is my honest opinion, if I noticed or did something to the car at this point obviously I would tell all!)
Anyway that is all the past medical history I can supply. We can only wait for the final autopsy report from Kevin.
Viper Bob trailed the car down and his mechanics and he were at the track and couldnt see anything unusual.
Good Luck Kevin, please tell me what the heck happened, and thanks again for the new engine!!
tom

WCE

Sorry to hear about your engine failure. Kind of ironic to have an oil related failure in an engine that was probably way over maintained in this respect. Just curious, with south Florida's heat especially on the track, were you running 0w-40?

Geoffrey

"the computer had a type 2 overrev within the hour before the crank broke."

Can you expand on that statement?

m42racer

"the computer had a type 2 overrev within the hour before the crank broke."

AHH ahh???

The old problem revists again it may seem. The nemisis of opposed Crankshafts with no high RPM balance. I kinda figured.