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996 rev data on Pre purchase inspection

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Old 09-13-2017, 01:22 PM
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BChivs
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Default 996 rev data on Pre purchase inspection

Hi,

I'm new to the forum so hello!

I need some urgent advice from those more in the know than myself. I am looking to purchase a 2002 996 C4S and the engineer has sent me the results of a rev range check which mean absolutely zero to me! Can please someone in layman terms tell me what it means and if I should be concerned??

It shows Rev Range 1 '4015' and Rev Range 2 '3'.

I would really appreciate some light on this.

Thanks, Ben
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Old 09-13-2017, 01:40 PM
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Billup
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It means they likely drove the car with some spirit. Personally wouldn't bother me one bit, some people it might. Did you have an overall check on the rest of the car? How did everything else look?
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Old 09-13-2017, 01:42 PM
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Rev's look good.
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Old 09-13-2017, 01:50 PM
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Tell me if I'm wrong, but am I right in thinking the revs in Range 2 are more of a concern and the rev firing has to be divided by 3 or something? This would mean it was only in Range 2 for miliseconds?
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Old 09-13-2017, 01:58 PM
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Range 1 is revs at limiter, and range 2 is beyond the limiter. There's no designation for the amount of time in either, albeit milliseconds unless the previous owner was negligent.


http://www.911virgin.com/porsche/rev-range-information/
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Old 09-13-2017, 02:16 PM
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Range 2 would be a concern if they JUST happened - i.e. somebody's been test-driving the car banging off the rev limiter - but with just 3 type-2 revs, I still wouldn't freak out.

Mine also had a few type 2's - but they were VERY old. Didn't stop me from buying.
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Old 09-13-2017, 02:18 PM
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The count is for ignition events - so in this case, there were a total of three ignitions above redline. Almost always this is a missed downshift. On the street, you hear this, "oh sh*t," and get the clutch back in.

All that said, Porsche won't CPO a car if it has over-revs, so clearly they consider this number a very important metric (at least when it comes to voiding warranties).
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Old 09-13-2017, 02:52 PM
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No big deal then really.....one missed shift in the cars entire lifespan?
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Old 09-13-2017, 02:54 PM
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That would be my assumption - which is why it wasn't an issue for me.

500 range-2 over-revs 5 operating hours ago would be more worrisome.
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Old 09-13-2017, 03:52 PM
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So this car had relatively few range 1 overrevs @ redline. And exactly one missed shift where it barely peeked above the range 1 range. It's not perfect but it's pretty darn close.
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Old 09-13-2017, 03:53 PM
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When I blew my motor from a horrible downshift on the track, it recorded 274 Type 2 over revs. So a total of 91 Revolutions, at I'm guessing 9000 RMPs. So it was in over rev for less than 1 second.

With only 3 over revs in range 2 for a total of one revolution, I'm not even sure if would know it happened. Almost seems impossible to only have 1 revolution in over rev.
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Old 09-13-2017, 04:28 PM
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Originally Posted by BChivs View Post
Hi,

I'm new to the forum so hello!

I need some urgent advice from those more in the know than myself. I am looking to purchase a 2002 996 C4S and the engineer has sent me the results of a rev range check which mean absolutely zero to me! Can please someone in layman terms tell me what it means and if I should be concerned??

It shows Rev Range 1 '4015' and Rev Range 2 '3'.

I would really appreciate some light on this.

Thanks, Ben
For a 996, there are only 2 ranges in the report. Range 1 is generally called the "rev limiter" count. Range 2 is typically called the "money shift" or "mechanical overrev." Range 2 generally happens when someone downshifts incorrectly (e.g., from 5th to 2nd).

Overrevs (of either kind) are counted in ignitions, and not instances/occurances. So, hitting the rev limiter for one full revolution (i.e., 1 R in the RPM acronym) counts as 3 "overrevs."

I'm going to do some math, and it might be all wrong, but here's my analysis:
With 4015 range 1 overrevs, that equals 1338 revolutions of the engine. Assuming these are all counted at 7900 RPM, the would be ~.17 minutes (1338/7900) of red line driving. That's about 10 seconds. So, since 2002, the car has been at the rev limiter a total of 10 seconds. IMO, that's barely driving the car. [I sometimes drive at the rev limiter for a couple seconds on the track]
As for the range 2, I would call that an anomaly or an error. It was almost certainly NOT a money shift as it was one full revolution. I can't explain how it registered, but it's virtually nothing (and I wouldn't consider it relevant in a PPI). If it was anything other than 1 RPM over the limit, it would have registered twice as many (i.e., getting there and then getting back down). So I really do think it's some sort of computer glitch. Using the same math as above (which might actually be completely wrong):
3 range 2 overrevs. = 1 R. Assuming 7901 RPM, that would be .0001 seconds of mechanical overrev. That's around 7/1000's of a second.

Another key factor here is the hour markers and total hours on the engine. If the "3" came long ago, then it definitely wouldn't be a concern.

And, I personally don't care about Range 1 at all. The more, the merrier. [I have over 60,000 on my car...]

-td
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Old 09-13-2017, 05:26 PM
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So the upper bound of range 1 is 7900? I thought it was lower on the m96.
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Old 09-13-2017, 06:21 PM
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Originally Posted by TonyTwoBags View Post
So the upper bound of range 1 is 7900? I thought it was lower on the m96.
The red dashes go up to 7800, so it must be around there. The Google machine shows 7900...

[edit] found this from Schnell in another thread:

Originally Posted by 5CHN3LL View Post
For reference:



Range 1 is actually a range; Range 2 was an absolute max. Range 2's are also referred to as "downshift over-revs" since the rev limiter makes it hard to get there any other way.
-td
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Old 09-13-2017, 06:55 PM
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Cool ty
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