Racers!

For those of you with experience of running the 991 Cup cars, can I ask what the recommended rebuild intervals are for the engine and gearbox (and then what you think is feasible in reality?)

Also your experience or expectations of costs for each?

Thanks in advance, happy driving!

 

Engine is basically an updated 3.8 Mezger engine. Almost same as 2010 - 2013 997 Cup.
History of that engine goes back to the 964 and is bulletproof.
Running on top level Carrera Cup (always max revs) will give you at least 50 hours before you would rebuilt out of pre caution.
Running on semi top level track day can give you 100 or maybe even more.
Have been numerous 996 cup engines (practically the same) lasting forever.
Just check leak down regular and change oil and filters after each or each second race day.

Gearbox will be the question for everybody i guess.
It is protected to over revving to an extend it will be on the safe side so therefore it should last longer.
I have not heard stories of rebuild and their costs but most top teams must have already done their boxes.
So it must be out there already .........

 

Gearboxes holding up really well on the 991 so far ..! Better than the 997
Early days with the box so let's see ..most opened but all ok this year ..!

 

Agree with the above comments. We figure 60 hours of real run time on the motors before rebuild. That excludes idle, pit and warm up time. They can go longer with leak down and dyno monitoring. 991 and 997 motor is identical other than exhaust and ECU variables.


991 motor should outlive 997 because you can't over rev unless you're an idiot and the electronics won't allow a downshift until around 8,300 rpm. Aggressively driven 997 cups are often downshifted in the 8,800+ range to take advantage of maximum engine braking. A few guys would downshift well north of 9,000 rpm. Not so good for engine life in a 997. I would figure engine rebuild cost at $35k, but that varies.

Tranny life should be superior in the 991 as well. With intense racing you can figure 35-40 hours or so on a 997 tranny. Maybe more. Clutch less downshifting, unmatched revs/blips and other high wear behavior are eliminated with the 991, so I would expect longer intervals. Cost on a tranny rebuild varies considerably if sealed by PMNA or built elsewhere. The former can run from $20-$35k in most instances. Figure saving at least a third if done elsewhere and a seal is unnecessary.

Lastly, you should know that a 991 is more difficult to repair and more fragile than a 997. It is also much easier for a 991 to be irreparable and require a new tub vs a 997.

Hope that helps.

 

Very interesting ! Thanks !

 

Thanks everyone for the speedy and hugely informative responses!

A couple of follow-up questions for you:
I was aware of the same DNA of the 991 and 997 racecar engines - do they run at the same rev limits as previously? If so, then 997 engine life and rebuild cost comparisons should be fully relevant, if the rev limit has been raised then maybe that will influence engine life for the worse. I guess comparing US vs European rebuild prices might be tricky too, would you agree?

The new box is a major attraction of the 991 vs the 997 for me - it takes a massive variable out of the equation as regards protecting the internals (over-revving, mis-matched downshifts etc) - in particular as we are racing it in endurance races here in Europe (4h up to 24h), where finishing at all is the first and most significant step towards finishing first....
Re the box in the Cup, (and this is a really obscure question for the super-techy guys out there) do we know if it is actually the same box as the one Porsche were running in the 997 RSRs? I think the latter are manufactured by Ricardo, does anyone know whether it's the same one?

Thanks again for all your insights, very much appreciated. I will be back with more questions no doubt in the future if that's ok with you!

Happy racing!

 

The gearbox information somewhat conflicts with what I am hearing from a number of US teams. They have had issues with new ring and pinion design, which on the new box requires also replacing the differential at the same time from what I am being told. I haven't seen the box apart in person, but my source is Bill Rader, who has likely had more US boxes apart than anyone else in the country outside of PMNA. Take it FWIW.

Regards,

Matt

 

I have a 2012 Cup and run in the Pirelli Cup series and recently switched to the Holinger paddle system explicitly for the reasons of protecting the gearbox and preventing engine overrevs. We installed the system after Bill Rader rebuilt the gearbox (following 3rd gear grenading on a test day).

Have used the system for 2 race weekends and two full test days and the drain plug magnet is cleaner than we've ever seen it from the bump shift days every time we've taken it out between events. Shifts are clean and smooth, although down changes take a little adjusting as the system is protecting from overrevs. So far this seems to be a game changer for the 997's gearbox reliability/endurance and protecting the motor.

If you have a 997.2 and you're in a series that allows a paddle system, it seems to negate some of the advantages of the 991. The brakes on the 997 still are what they are, but the 991 certainly seems far more costly to fix if you have an incident. The retub cost/frequency would be my biggest concern with the aluminum chassis sections glued together. Several incidents we saw this year would have required retubs if the drivers were in 991's.

Cheers,
Mark

 

Mark knows of what he speaks. A paddle shift 997 with 991 brakes would be the theoretically lowest cost car to run or crash !

 

+1
on paper the 991 box is better
in reality its been problematic. 2015 update should sort out a lot of the issues

 

I was under the impression that the changes for 2015 were mainly limited to shocks and a different paddle shift system supplier. Are changes being made to the transmission internals as well?

 

fuel pump changing too

i've heard some new internals and a new actuator.

around 10K euro for the update and mandatory if the car enters CC

 

Correct. Existing actuator is a high failure component.

 

Can you or someone else explain this in a bit more detail? What are the differences between the 997 and 991 chassis-wise that would require retubbing?

 

991 uses a combination of various steels, aluminum, and magnesium in construction of unibody, some of which apparently are bonded with adhesives verses traditional welding. See explanation below.

"The chassis of 991 is all-new. It has a more modern proportion, i.e. faster windscreen and fastback angles, shorter overhangs, slightly lower and a wheelbase boosted by 100 mm to 2450 mm – that is only the third wheelbase extension in its entire history (the first and second happened in 1969 and 1998 respectively). It also sports a wider front track to improve handling (up 46 mm on Carrera and 52 mm on Carrera S).

Despite of the extra dimensions, the new car is 30-40 kg lighter than the outgoing 997, thanks to an aluminum-steel hybrid construction. Porsche did not follow Ferrari or Audi to employ spaceframe chassis made entirely of aluminum, because that would have thickened the pillars and door sills thus hamper cabin space and ease of entry (remark: aluminum takes larger section than steel to achieve the same stiffness). Instead, the 991 uses super-high-strength steel, baron steel and multiphase steel at locations where stiffness matter most, whereas aluminum is used for the floorpan, roof, door skins, bonnet, engine lid, luggage compartment, front crash structure and rear fenders. They comprise 45 percent of the body shell. Besides, the dashboard mounting beam is made of magnesium. The new chassis is 20-25 percent torsionally stiffer than the old one."

First photo is 991 unibody. Second is 997, which used different types of steel in the unibody construction.