Red rooster

Geoffrey,

No way would I have a 7200 rev limit on a standard 964 motor. 7000 absolute tops. Maybe I am just careful ??

Jason
As for 7440rpm, that is ludicrous.

Geoff

Geoffrey

Geoff, I agree with you, but it is because of the valve springs and retainers. The rod and rod bolts are fine to 7200, and the rods with upgraded rod bolts are fine to 7500. Beyond that I know people have run them, but I would not.

NineMeister

Sorry Geoffrey, for once I cannot agree with you about the safe rpm limit for our stock 964 & 964RS engines. You are correct in that the 964/930 rod is good for 600hp in turbo applications which have high compressive forces and generally low piston mass, but in an n/a engine because the main loading of the rod is in tension at TDC overlap with no pressure above it to resist the load, the weight of the stock 964 piston stretches the rod too much and the rod/piston combination flexes under load.
The tell-tale sign of a persistantly high-revved 964 engine are burrs on the outer edge of the piston circlip grooves, which occur when the pin is loaded sideways due to rod flex and starts to knock the pins out of the bores, if you strip an engine with these marks you know when you have to use a pin drift to get the wrist pin out of the bores.
The second issue is fatigue within the piston around the pin boss where the material is being stretched away from the rod. Even with a better connecting rod the stock piston is still not suitable for use above 7000rpm as it will eventually elongate in the vertical plane and eventually fracture along this point.
And how do I know?
The shuffle problems occured in a 964RS engine that we developed a long time back, it had Motec, throttle bodies, cams and stock rods; due to cam problems I stripped the engine after 3000miles and was shocked at the burrs on the circlip grooves. It went back together at the time with Carillos and we dropped the limit to 7250rpm....
...until I then stripped another RS engine that had spent the last 3 years on track, again on Motec, with a 7000rpm limit and 7200 hard cut, on which the datalogger told me that the rpm limit had been exceeded a handful of times but never more than 7150rpm. Fortunately for the customer I specified new rods on the last build, luckily these saved his crankcases from major damage when this occured to the piston:

Anyone still want to run 7500rpm on a stock bottom end??

(so now you know why 9m have manufactured 100mm & 102mm Clubsport oem fit replacement pistons for the 964 & 993 engine...)

Red rooster

Geoffrey, Colin,

The fact that we are discussing this, in this kind of detail will maybe head off
someone getting too brave !
I find pictures like Colins , so sad. Its tempting to go that bit further but for years I have been urging caution.
7500 rpm sounds good over a beer but not so impressive when the whole motor is scrap !and when a rod breaks free at 7000+ you wont believe what can happen .
The DME rev limit will be slightly exceeded , especially in the lower gears , due to the motor inertia situation.

Geoff

warmfuzzies

Can i take it the "wrist pin" is in fact the Gudgeon pin???

Kevin

Red rooster

Kevin,
Yes.

Geoff

Larry Herman

That's what happened to the PO of my car. My chip has a 7300 rpm redline, and he ran it to that more than he should have. Also used to break rockers in the process. Anyway, at TWS a wristpin let go, and the con rod cut the motor in half. Practically nothing was salvageable, not even the intake manifold (also split). Talk about grenading a motor.

TR6

One of the reasons I've been hesitant to chip my 964 is because I don't want to raise the rev limit past the OEM rpm limit. Although I've heard you can spec chips that don't alter the original rev limit....

NineMeister

At the end of the day it is always the driver who is bouncing the engine off the rev limiter, not the chip, so if you were to choose a new program for your ecu that has a raised rpm limit, it does not mean that you have to use it!
As others have mentioned, I would be comfortable setting the rpm limit of a good 964 engine to 7000 from its standard limit of 6800 and happy to use it on the odd occasion on track where you are in-between bends and there is no point in doing an extra up-down shift. Besides, if your engine uses a stock intake manifold it will limit the peak power rpm to somewhere between 6000 & 6400 irrespective of the cams used, so you would be better off changing at 6700 to hit peak torque at 5000rpm since the area under the power curve in this region is greater.

TR6

True! But sometimes I get sloppy and am looking ahead and not watching the tach! I've been known to bounce off the limiter once in a while and am glad its there!

DaveK

If it wasn't for rev limiters I would have destroyed my 964 engine several times - and when I had the R1 I hit the rev limiter on that several times. I even hit it on my Ford Focus once I think.

Haven't managed it on the Supra, so maybe my driving is improving.....

warmfuzzies

Or not as the case may be Dave.

Megatron-UK

When I had my automatic Supra TT, the only time that you could hit the rev limiter was in 3rd to 4th, the changes from 1-2 and 2-3 were just so quick with the ecu controlled box (it's a fantastic gearbox, never mind being just a fantastic *auto* gearbox!) that it wasn't possible.

Mind you, redline at 3rd to 4th in that thing was nigh-on 130mph, so you had to be giving it some beans in order to hit the rev limiter

Haven't tried that much welly in the C2T... I've a feeling it may try to bite my head off......

DaveK

You're just rude!

warmfuzzies

Damn, unmasked................................