JPschnitzer

Tom,

I'm sorry that this happened...You are a real trooper, and your positive attitude during this is great to see.....Cars break...especially at the track...BUT, over revs, chips, etc....or not, the damn crank in a Porsche should not just blow up....this is just wrong. Could it have something to do with the factory insistence that we use this watery 0-40 Mobil one?

Geoffrey

Why would you think that the 0w-40 is the problem? The 0w-40 is necessary due to the hydraulic tappets and the variable camshaft actuators. FWIW, NASCAR engines run 30 weight oil. Its all about the design and a lighter weight oil has less friction inside the engine, not more.

wross996tt

Unfortunately we will never KNOW what caused this failure...even after examining the parts it will still be hypotheses as to what happened. Since all of the parts in the motor are manufactured it could be material variations or manufacturing variations that resulted in a component(s) with less strength than average (after all 50% will have strength less than the average ). We will never know, only be able to speculate. So on to the next motor

Steve Weiner-Rennsport Systems

NASCAR Nextel Cup engines use oils far lighter than 30 wt. These use 0w-10, 0w-15, and 5w-20 weight oils. All clearances are designed around these ultra-low drag lubricants.

One of my good customers is an engine builder for Roush-Yates and he is kind enough to tell me a few things when I ask specific questions,...

I'd be using a 0w-40 product for any engine equipped with VarioCam.

Wachuko

I know this is due to a suffering Rennlister, really sorry you had to go through this Tom; but this thread has been a great source of information sharing even among those that agree to disagree...

tkerrmd

Well I agree alot of good info. I have taken alot of this to heart and will be driving and monitoring differently than in the past. But I will still be at the track every weekend I can, I bought the car for enjoyment and that is how I choose to do it so I will pay the price.
Hopefully we will all learn more when Kevin examines the engine this week.

Again thank you all for your support, information, and help with my huge problem.
tom

1AS

JP,
Hate to disagree, but eventually, every mechanical thing breaks. The only variables are the number of use cycles, upkeep, and load. 8,000 track miles is a bunch of load for a car with aftermarket mods. The typical guy with mods does a hot mile here, or a quarter of a mile there. Tom has been exploring his limits and the car's limits for some time. That is lots of miles at peak demand.

The fact that we could even begin to complain about it is a wonder. When I first started to autocross (in a progressively modified 1966 Olds 442, but with standard engine internals), it would have been hard to get 100 all-out miles on an engine. You could watch the oil pressure idiot light flicker in hard corners, knowing sooner or later the bearings would go. The lifters floated, and the timing chains stretched. We have seen a ton of improvement, but are still learning the limits. Nascar guys can't get 8,000 race miles out of a motor. Maybe Miata guys can, but a turbo with 500 hp.... I don't think so.

Thanks to Tom's candor and enthusiasm, I suspect lots of people will have some adjustment of expectation. Maybe the right answer is to leave the X50 bone stock, or do the whole bottom end when all the mods are done. That seems to be the take home message for track junkies.AS

tkerrmd

AS as usual you provide accurate, insightful comments. And I think you are correct. My new plan is to run the X-50 as hard and as long as I can the way it comes in the box. I put my short shifter back to stock, adding shift light, A/F, oil temp, and boost gauges and running it as I thought it was meant too.
Future plans will be an engine overhaul and rebuild when the warranty expires.
thanks for your input!

Geoffrey

It sounds like you are ready for a GT3 Cup...

drane

Tom , Sorry for your pain, I was running with you at Sebring. I have blown up two turbos and now am happier with normal aspiration and a lighter car. Geoffrey may be right, before ytou unload on a new engine, think about your options.

Jean

Geoffrey I was referring to the 996 Turbo crankshaft, I don't have access to my data as I am several thousand miles away from home but I seem to remember that the crankshaft had ben lightened to reduce rotating mass. Bearings were also strengthened with some Ni-Ca alloy or sth.

Geoffrey, the 996TT use the same crankshaft as the GT1 race engines, only those were a bit lighter, so the homologation angle I don't think is a factor. Many privateers run professionally in GT2 class in Europe using highly tuned 996 turbo engines (maybe in the US too) and their cars use the 996TT crankshaft, which has wider journals than the GT3 ones (unless I am mistaken and they're not?). On the thoroughly race proven 993GT2 engines with the same crankshaft as the TT, I have not read of any engine failure due to crankshaft damage, it was mainly gearbox and top end issues, the crankshafts proved to be very solid and still are. Bearings were upgraded.

The highly reliable RUF RT12 also uses the TT crank.

As I mentioned before, there is not enough professional racing experience here to prove either way, but more evidence than not that the TT crankshafts do perform very reliably in the harshest of race environments, within their operating parameters and proper tuning.

I obviously don't have any race car building history either so I only try to look at proven facts to base my opinions, which obviously could be mistaken.

Kevin

Jean, the 993TT crankshaft and the 996TT are the same. Yes, the 996TT crank is newer but the raw casting/tooling is the same.

The Rod journals are narrower with the 993TT, 996TT crankshaft.. The width of the rods are narrower. The GT3R cranks have wider journals.. It is similar to the 930 and 964 journals.

tkerrmd

That's the plan.......soon

Geoffrey

Jean, the GT1 was a 3.2 liter engine and did not use a 76.4mm (993/996tt) crankshaft.

Jean

Apologies, I am slow in answering as I have very limited net acccess in my current location.

Geoffrey,

I of course know that GT1s were 3.2 ltrs (there were three different engine sizes and versions in fact), except one which ran a 3.6ltr engine in 2004 and it was homologated in LMGT as a GT1 racer and raced in Le Mans Series, funnily, it is a 100% 996TT based engine.

The GT3 crankshaft was based (with modifications, I should have been more precise maybe ) on the GT1 crankshaft, and it is a 3.6 ltr engine, so is the 996TT crankshaft.

Kevin thanks for the correction. I should have taken more time to write my post and use more precise language, I will give it a shot..

The 993TT, 996TT and GT3 (same as GT3R, GT3 Cup etc..all the same) all use a similar crankshaft (material). AFAIK, the GT3 crankshaft has no change in the oiling holes, only a feed from the nose and the rear bearing, just like the 996tt.

GT3 race teams claim that the GT3's (996) have common rod bearing failures and that the fix is the same as the 993/996tt cranks, by modifying the oiling in them.

Since lubrication is known to be the major reason for crank/bearing failure on the TTs, I don't think the GT3 crank itself would make a difference as it has the same oiling specs.

As far as journals etc..from information I gathered during my research,

- The GT3 rod journal as you rightly said is not narrower, but the diameter is smaller vs. thinner (narrower), It is 53mm at the crank running a 22mm wristpin. Do you know the width of the journals? I think they are 25mm ?

- The 996tt shares the same crank as the 993, having a 55mm journal at the
crank and a 23mm wrist pin if I am not mistaken. So the rod journal diameter is larger than the GT3 crank and will withstand more torque (?)

Is the GT3 crank better or not? It's different, it has wider journals BUT narrower diameter journal, which Porsche probably did to reduce reciprocating mass on the high revving GT3. So we don't know, but I always think that when Porsche engineers do a change on a turbocharged engine, they know why they have done it (that's only me of course ) and IMO it is due to the higher torque levels achieved, and lower RPM usage (hence rotating speed).

I find it very strange that Porsche has used a narrower rod journal on the new 997GT3 crankshafts while increasing usable range by 200RPMs......so was wider better or not? I don't think there is a definitive answer.

I guess I go back to my original post and the heart of the matter, and regardless of sizes and specifications of crankshafts, which I could have posted wrong maybe, IMO the 996TT crankshaft itself is not the issue, the problem lies somewhere else, those TT crankshafts have been used for years in heavyduty professional racing environments, since the days of the 993GT2 with great success, after some modifications to the oiling and bearings.

Cheers