porsche52

Look, the M96 powerplant cannot reach 16k rpm!!! No way in hell!!!! Your buddy may have a cool tach that reads up to 20k rpm, but unless he drives a F1 car, it is just another gadget to impress the girls with! Anyone who has disassembeld this engine will tell you the same. Now as for the idea that the RMS/clutch repair is linked to the engine failure is a no go too. As Jack stated, most likley failure is "D" chunk or cracked liner thus the coolant/oil intermix. But without proper engine tear down, all we can do is speculate.

JDSStudios

Macster, you may have the number backwords.
1 Bit=8 Bytes, right?

ltc

Incorrect.
Your logic would apply for a Type 1 (engine accelerating under fuel/spark control).
It would not be correct for a mechanically induced engine crankshaft rotation.

Example:
Turn ignition off.
Connect tow strap to vehicle
Put vehicle in gear.
Tow vehicle now begins to pull the vehicle and continues.

The tire circumference, speed and gear ratio will determine the engine (crankshaft) RPM, independent of any 'redline' on the tach or 'rev limiter' (engine is off in this case).

It is the same as when you used to have one of those little spring driven mechanical cars as a kid...you would push it against the ground for as long and as fast as you could in order to get the RPM's up as high as possible....mechanically induced over rev.

Relaxed90

^ Sorry, but the fact of the matter is, @ 2nd gear, 7200rpm, there is a given wheel RPM. If you shift instantaneously into first and the wheel RPM does not drop (in real life, there will be a slight drop during a shift), then the engine RPM can be calculated by the ratio between 1st and 2nd gear, which is what the previous poster suggested.

The wheel RPM which takes into consideration its diameter, angular velocity, yada yada, can be considered the constant in this situation.

JDSStudios

1. Would you even be able to put it in first at that speed (not that I would try)

2. How can you not be sure if you actually did or not a money shift?

salayc

No, 1 byte = 8 bits. Not including parity, of course.

Also, Durametric (they claim to read overrevs like PIWIS) only displays range 1 and range 2 for the 996, not actual values.

Third, range two overrevs are not the number of times the car has been overrev'd but how many sparks occurred. i.e. if a car was overreved one time but held there for a while, there could be a huge range 2 overrev number from a single missed shift.

ltc

My reply was to demonstrate that this engine (like any other engine connected to a drivetrain) can in fact be spun to 16000RPM via external mechanical forces, not internal combustion forced. That is all.

It is still unclear what happened in this particular case, since the original post seemed to indicate possible 3-1 shift, but it still not clear what may have happened in this case.

Meister Fahrer

Not that there's a lockout per se, but downshifting into 1st gear at anything over a crawl is very difficult.

That's true with nearly all manuals that I've ever driven.

When I drive hard, I'm only concerned about the 4 -> 5 shift...that I might hit 3rd instead.

So....you're not going crazy -- you didn't jam it into 1st.

Also, if you went from 3rd to 2nd -- let's think about that for a minute.
If you would have been at redline in 3rd doing almost ~100mph, is that possible you were going that fast?
Then you went down to 2nd?

But the other poster is right too, the motor would have collapsed right at that moment....

I don't know about their previous repairs, but what the shop is telling you now does not compute in any way.....

Tippy

I use redline as the RPM because that is all the rev limiter (Type1) will let you do. Its an assumption.

Read below what relaxed90 said - he says the same as me.


Exactly.

Jake Raby

It is possible to mechanically over rev an engine to infinity via a downshift..

My experience with this has proven that its near impossible to get a transaxle into first gear at such high speeds.. It can be done, but it takes effort.

I'll be forcing an engine failure in a few weeks on the dyno just like this and I'll let you know how it comes out.

Macster

Why would you force such a failure? What do you expect to learn?

Sincerely,

Macster.

Macster

No. A byte consists of 8 bits. Each bit is either a 0 or 1.

A 2 byte number consists of 2 8-bit values thus 16 bits. And 16 bits can express a number bewtween 0 and 65535.

Sincerely,

Macster.

Tippy

We do this with our jet engines. We purposely put cracks or parts that are over their time limit in an engine and run unitl failure.

Then, you use destructive testing and a lot of data can be gathered.

Im sure Raby is doing the same but only see what will let go first and determine the weak link of the motor I assume.

JimB

To hit 16,000 in 2nd I think you would need to be spinning your rear wheels at just under 155 mph. Again, not likely.

JimB

My computer science degree from 1982 says you are correct although in the early days bytes tended to vary in size depending on what chip set your computer was running on.