Mikelly

Tom, I greatly appreciate the info you've provided to this point, and thanks to Kevin for doing the autopsy. I'm all ears... Quite frankly I'm surprised that oil temps as low as you folks are quiting are considered "harmful" to the porsche rotating assembly. The Vette guys are seeing much higher sustained heat/oil temps, and they do have an oil temp gauge from the factory... Might just need to plumb one in after reading this...

I have changed my oil every time before each track event. Now I'm wondering if I shouldn't be running something a little heavier, weight-wise... Crazy the things that happen to these motors when at full song!

Mike

eclou

Great educational thread! I hope the oiling on the 997tt has been improved, but it is part of the reason I hesitate to raise the rev limiter, and I always run either octane boost or mix in some 104.

Like RXDOC I too am too cheap, nervous (and limited in skills) to use these newer cars exclusively for my track days. I was even nervous tracking a nice modded E36M3 earlier in my days so I picked up a neglected $3k 944 turbo locally and spent 2 years massaging it into dedicated track duty. All in I have about $10k in the car and with 310rwhp and 2600lbs of weight it is plenty competitive for spirited DE work. I can drive that car at 9/10+ and have much more piece of mind than driving the TT at 6-7/10. The way things work out now is at the DE I drive the 944 turbo and the wife drives the 997tt. I usually take out the tt for 1 maybe 2 sessions at the end of the event. Just another thing to consider.

tkerrmd

I am trying to give every detail, even if it is painful or ego damaging in hopes of helping out myself or someone else.
After the car was towed in we ran a computer check and I was "told" well what do you make of this type 2 overrev? Well it happend about an hour prior to the engine blowing. Meaning somewhere around 2 or 3 sessions ago.
to the best of my knowledge I had no trouble with missed down shifts or any thing really obvious. so.......the car ran fine for an hour of track time after the dreaded "type 2 over rev".
Me vascular surgeon not car surgeon, got to admit I dont think I personally did anything at the track with my own hands or feet and the car ran another hour prior to exploding.
so if I caused damage and it blew an hour later well then I am just a dumbass.

for the record in case I had not mentioned this (poor ego) pulled the tranny apart and the third and forth synchos were shot!

I am really trying to get an oil temp guage, A/F guage, accurate boost guage, and some driving lessions before I go back to the track.

must admit in one of the session prior to the engine explosion I had a pro driver out coaching me and certainly for what its worth, said I was a pretty damn good driver (although he could have just been trying to be nice, I really was looking for some critiscism)

oh well thanks again for all the input and reading and replying to this post I really appreciate it and it really has helped me (become even more OCD)
tom

tkerrmd

Mike, this post was especially for you and heavychevy, sechsgang, and all the track guys.
Have any of you given any thoughts as how to better protect these cars at the track? I will wait to hear from kevin and also going with additional gauges if possible. but now I have been told if my track addiction persists I should run the X-50 TOTALLY stock. which really means no ECU flash.
that is what I am going to do but the battles with the new Z06 and GT3 will I think now be out of my reach and I will be made fun of at the track for having such a slow heavy car!!!
Have to admit with the full race suspension, 3300 pounds, ECU flash, straight pipes and hoosiers was running with the best of them, till I BLEW THE ENGINE UP!!!
Would like to hear some of yours and other track guys thoughts as this thread continues, and thanks for all your track info I have learned alot from your experience as well.
tom

MidnighTT

I have added another couple of type 2 overrevs by just kissing the limiter, not slamming into it. I watch them like a hawk now that I have Durametric software, so I know exactly when they happen.

Thus far I have NEVER missed an upshift with this car (knock on wood).
I have NEVER blown a downshift with this car (knock on bigger wood).
I have, however, visited the rev limiter. One of those times was when the car broke traction in first at about 5500 and slammed into the limiter. That one cost me 9 counts IIRC. The more recent limiter visit cost me only 2 counts.

I don't know where the type 2 threshold is, but my guess is 7200. I'm beginning to think that they aren't nearly as evil as some may think. For sure, in some cases like a 5 > 2 (instead of the intended 5 > 4) downshift that zings the motor to 8000 (or more!), they can foreshadow serious engine damage. But I'm absolutely positive that they can come from simply hitting the rev limiter, at least with my '02.

Jeff

tkerrmd

Will I will admit I hit the rev limiter all the time and I didnt think it was a big deal, I wont with the new engine and I am also thinking of a shift light to help out at the track.

m42racer

"""Will I will admit I hit the rev limiter all the time and I didnt think it was a big deal, I wont with the new engine and I am also thinking of a shift light to help out at the track. ""

Tom, I have been told the limiter can be so harmful to an engine as much as the over rev itself. The sudden uneven firing at higher RPM's causes the Crank to go into all sorts of harmonics and twists.

Best to call whom I suggested in my PM. You will get the real answer there. I think the correct reason the Crank broke is in your explaination. "Heat" and "Drag" did not do this in my opinion.

wross996tt

I don't know Tom...I guess you just have to realize...if you are going to track the car...you are going to have mechanical things go wrong now and then....should be in your "track budget". I think you just have to be comfortable with this and drive it like you want...forget worrying about the inevitable...JMHO.

Mikelly

Tom, Although my roadcourse experience is long, and lord knows I've broken a LOT of parts over the last 20 years, I'm so new to porsches that I really am at a loss... I thought the dry sump, the added cooling capacity, and porsche engineering was all I needed. Running the setup I'm running makes me wonder if I wont be far from your situation... Lord knows I don't want to have to shell out the coin for a new motor, means to do it or not, nobody wants to go that route if at all possible.

Until the last event, at Watkins Glen, I had never come close to hitting the rev limiter. However, being so down on power, I was pushing the motor harder and was bouncing the rev limiter the last two sessions of the weekend... Not good...

With the track car I'm building we've added a remote filter accembly that includes relocating it up near the radiator/airflow. We've also added an oil cooler and an accusump. I'm hoping that we'll be able to keep my small black chevy's oil much cooler. Bottom line is if you're gonna run with the big dogs, you're gonna break hard parts doing it!

We're all ears... Keep up the posts/ updates...
Mike

tkerrmd

You are right and that is what I did and will do but gotta admit, the blown engine kinda wasnt in the "budget"

Geoffrey

Hi Simon, it's been awhile...I can see why a reve limiter might be hard on an engine as your friend suggests, however, I'm not so sure it is as bad as some people make it out to be. Also, advanced functions like traction control and launch control both use cylinder cutting strategies. I bang off the revlimiter from time-to-time and I have traction control which is very active on a damp track and have not noticed any significant engine wear.

Tom, one thing you might want to do is to start doing oil analysis as well as keeping a log of how many hours you run your car. These are two things that will give you an indication as to the health of your engine. IF your type 2 overrev was the result of a missed gear, then I can see a damaged rod bolt. IF your type 2 overrev is simply from hitting the rev limiter, I don't believe that in itself, will cause the failure.

You may also find that you might be interested in getting a lighter N/A car for your track duties. I came from a high HP turbo car to a lightweight N/A car and much prefer it.

Jean

Geoffrey

Thanks for your earlier explanations, they are very enlightening.

It is debatable whether the lightweight GT3 crank (GT3, GT3R, GT3 Cup they're all the same) with narrower journals is the right crank for high torque turbocharged engines or the factory would have simply used it. The GT3s are not torque monsters but rev high, they need good oiling and reduced friction etc.. but their cranks are not necessarily a better option for high torque engines.

The highly modded (100k Euros + on engine work) watercooled turbo Porsches (GT2R) that are running in GT2 class in professional series Belcar, Spa, Zolder and others and other big European races use the 996TT/GT2 turbo crank as a base. I have confirmation from at least one of the top teams, not sure what others use though (could be GT3 cranks)

For high revs, balance (no dampener), and great oiling, GT3/R/RS/CUP etc yes, for high torque of a turbo charged engine, probably not so, respectfully there isn't enough R&D or race experience here to give a definitive answer about longevity in race environments for GT3 crank-based turbo engines.

Crank failure on these engines with proper software and correct running conditions (no overrevs etc) is very rare, obviously poor oiling or high mileage coupled with incorrect maps and boost, will definitely destroy the bearings and other.

Tom,

Your X50 stock might give you same or better lap times than your ex-package, provided you keep it per factory, no turbo work or other(obviously LWFW and straight pipes is no problem). You just need to wait for a couple of full throttle laps before you start seeing the difference . It would be great if you could, at some point, report back about your lap times differences with both setups, after a few sprint laps that is. I was reading on the 993TT board that at a recent VMAX in the UK, a stock 993TT with factory 424PS upgrade did 184mph top speed, in 1.5 miles, which was the same speed of some tuned 996GT2 with claimed 520HP, despite worse aerodynamics, food for thought on heat soak.

Cheers

Geoffrey

Jean, The GT3R crank is actually heavier than a 993 style crank by a few lbs mainly because or the larger counterweights like the earlier 930/3.2 crankshaft.

"It is debatable whether the lightweight GT3 crank (GT3, GT3R, GT3 Cup they're all the same) with narrower journals is the right crank for high torque turbocharged engines or the factory would have simply used it."

The more I think about it, the more I disagree with this statement. The TT engine is a factory production street engine and I'm not aware of any racing turbocharged versions produced by the factory for customer racing. I'd say, that for a street application and stock power levels, the stock crank is fine which is why I believe they used it. The GT3 engine has the racing crankshaft version because the GT3RS (street) is the homologation model for the GT3R, RS, RSR and therefore would have to have the racing version of the crankshaft to comply with race series rules.

I also don't think that performance is the #1 concern for Porsche's street cars, I think they choose parts for a variety of reasons like economics, longevity, reliability, and performance. They are not selecting parts simply because they are "the best" available.

m42racer

""I also don't think that performance is the #1 concern for Porsche's street cars, I think they choose parts for a variety of reasons like economics, longevity, reliability, and performance. They are not selecting parts simply because they are "the best" available.""

I totally agree with this statement. For those who are building performance engines based upon the street engine, read the above statement and have it tatoo'ed into your brain. The issue is always, if I don't have to I won't do it. Many get away with this, amd some pay the price. Do you want to put your engine at risk to save a few bucks? I don't.

Geoffrey, the loading on the Crankshaft and other engine internals is different when Tractiojn control is activated verses the engine speeed limiter. I do not know about the Bosch system, but many of the EFI systems drop the same Cylinders every revolution until the fuel cut happens. Its this unbalance with the full load of the car at speed that causes the damage. Traction usually drops Cylinders in order with the engine speed at a lowere speed and less dynamic load due to the lower road speed.

Geoffrey

I know that the MoTeC ECUs I use drop random cylinders for all cut strategies (revlimiter, launch control, traction control) and use fuel cut, ignition cut or both to do it. The factory revlimiters are extremely smooth and I would think that they employ a similar random or alternate strategy. I can certainly see why dropping the same cylinder could create issues.