Over revs type 1 and 2

[Ckrikos]

Would you guys buy a low mileage car with type two over revs, the car ran fine and the last over rev was 200 hours ago. I was curious so to compare my boxster had 0 type 2 over revs but 11,000 type 1 (thats why my ims was in good shape). I decided to pass on the car as im worried the type two over revs may have damaged or at minimum really beat on the components in the motor.

For those that don't know type 1 is when you bounce off the rev limiter and type 2 is a bad downshift that causes rpms to surpass the rev limit.

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[RawleyD]

I think you are worrying too much.

[BYprodriver]

Type 2 revs can stretch oem rod bolts.

[steved0x]

How many? My car has exactly 1 type 2 overrev. How could you have only 1 ignition worth of type 2? If it is a legitimate count then it must not have been very sustained.

[Ckrikos]

If the car in question only had one I would be ok with it. It had 208.

[Timco]

I assume only a Durametric can tell you this??

[Ckrikos]

Dura metric or porsche computer. I was reading that Porsche could void your warranty if there were type 2 ignitions.

[san rensho]

Originally Posted by Ckrikos

If the car in question only had one I would be ok with it. It had 208.

So the motor had a bout 35 revolutions at over rev, which is comes out to about 1/2 second. Sounds like the PO did a money shift just at the type 2 threshold, which immediately went below the type 2 threshold because of engine braking.

Since the over rev was so long ago, it probably is not an issue.

[Flavor 987S]

Originally Posted by Ckrikos

Would you guys buy a low mileage car with type two over revs,

No I would not. There are 1,000's of Porsches for sale. I'd buy one with a healthy DME report.

[thstone]

I bought my 996 with a few Type 2's that had occurred quite awhile ago. And I used that evidence to get a discount on the price explaining how I'd be taking a risk with a possibly "over-stressed" engine. Car still runs great at 130,000 miles. Your mileage may vary.

[Homeboy981]

I had several Type 2 overrevs….could help explain why the engine has gone to that BIG Machine Shop in the sky (a.k.a. found at your local junk yard as scrap).

Funny how terrible events make the best humor…until it happens to you, of course!

[Ckrikos]

I would be ok if it was less than 100. The turbo guys on rennlist are ok with 200 type 2 ignitions. There are claims that type two can be triggered when up-shifting, in between shifts. I just want a good car as these are expensive cars to repair.

[stephen wilson]

A type 1 overrev is no big deal, that didn't cause your engine failure.

[Steve Tinker]

Has anybody got the calculation for interprating overrevs?

If your DME says you have (say) 1,000 Type 1 overrevs, how many second or crankchaft revolutions is that?

I know I nearly fainted when I saw my engine had 22,000 Type 1 overrevs, but that was about 100 hours run time ago and I'd already had the car for a year when I discovered it...... Looks like the car had been on the dyno in its previous life, but up to now no mechanical problems, touch wood.

[Timco]

Now I want to know and I don't.

Like Schrödinger's cat.....

[san rensho]

Originally Posted by Steve Tinker

Has anybody got the calculation for interprating overrevs?

If your DME says you have (say) 1,000 Type 1 overrevs, how many second or crankchaft revolutions is that?

I know I nearly fainted when I saw my engine had 22,000 Type 1 overrevs, but that was about 100 hours run time ago and I'd already had the car for a year when I discovered it...... Looks like the car had been on the dyno in its previous life, but up to now no mechanical problems, touch wood.

The brain counts over rev ignitions, since there are 6 cylinders, divide the over revs by 6 to get the number of revolutions at over rev.

To calculate the time at over revs, the formula is 60 seconds/7500 revolutions = x seconds at over rev/number of over rev revolutions. Solve for x and you get the seconds at over rev. Or, 60/7500*(over rev revolutions)=seconds at over rev.

So in your example,, it translates to 1.4 seconds at over rev.

[billj18]

With due respect, I question this formula. Four cycle engines fire every other revolution, on the compression stroke, but not on the exhaust stroke. Thus, it would be only three ignitions per rev; six ignitions would equal 2 revolutions, right?

Bill

[san rensho]

Originally Posted by billj18

With due respect, I question this formula. Four cycle engines fire every other revolution, on the compression stroke, but not on the exhaust stroke. Thus, it would be only three ignitions per rev; six ignitions would equal 2 revolutions, right?

Bill

I think you may be right.

[Brad Roberts]

He never said which engine/car this is.

2.5 engine with T2? Buy it.. use the info to get a discount
2.7/3.2? Who cares.. factory rev limit is 500rpm higher than the 2.5

Max. engine speed rpm
2.5= 6700
2.7= 7200
3.2= 7200