nycarb

DME below from 997TT ppi

From searching I understand that the my results for ranges 3 to 5 equate to less than 1 sec in time which happened 250 hours ago.

However the tech said it's still cause for concern

Who do I listen to? Is it okay?

Ignitions - Range
1000 range 1
270 range 2
50 range 3
6 range 4
1 range 5

Skwerl

That report is completely healthy IMO. Those are even pretty low numbers of 1-3s.

nycarb

Yes the "tech" said "buyer beware" so I was concerned a bit because they are experts and know everything/anything about Porsches.... right?!

But I wasn't sure if it's one of those things where... once those ranges are touched, even for a second, it compromises some internal mechanical integrity going forward

bruni911

How do u calculate the time per sec in each rev range?

nycarb

Assuming there are 350 ignitions per sec at 7k RPM. And just extrapolate the ranges from that

Skwerl

Lots of debate around that on all the Porsche forums and tons of threads about it. Some people will flee in terror of any car with a single Range 4, while others take a more nuanced case-by-case approach.

With such few overrevs and 250 hours having elapsed, I'd be pretty confident that car will have zero issues caused by revs, but that's just me. Based on the evidence I've seen it seems that if a 997 will have problems from overrevs, they're going to pop up pretty soon (instantly or within a few hours). There are lots of cars out there with way more 4s and 5s and even 6s than that report and by all accounts they run fine and are still solid.

jhbrennan

7200 rpm divided by 60 seconds = 120 rps. With 3 ignitions every revolution 120 rps = 360 ignitions every second. 270 range 2 ignitions is about 0.75 seconds - a blink of an eye. I used nice round numbers for my example but you get the idea.

997.1-Renn

2006 Carrera S (Cab) : 31K Miles
Range > Number of Ignitions at OverSpeed > Operating hours counter reading...

1 > 1957 > 1256.600 h
2 > 415 > 1216.300 h
3 > 61 > 653.900 h
4 > 1 > 434.200 h
5 > 0 > 0.000h
6 > 0 > 0.000 h

Any help would be greatly appreciated, I'm very new at this! Thanks!

Needsdecaf

Yeah, that was literally ONE small overrev.

BTW, does anyone have definitions for the ranges? I always wondered how it worked when you have different redlines. Are they percentages of redline? Because all DME's say Range 1, Range 2, etc....

saabin

Different car(s) have different range definitions..

http://www.911virgin.com/porsche/rev-range-information/



Video explanation

Needsdecaf

Great link, thanks!

lflouie

Yes basically correct on the math. With that said it is a race motor that race drivers routinely over rev'd and abused.

A total of .75 seconds could be a single event or three .25 second events. Any rev count less than 20 could be noise and not necessarily a true event.

If a car had a limited number of over revs or a single event of less than a 1 sec (arbitrary count) I'd feel confident with more than 150 hrs (500 mi) since event for a level 5 or less. The facts that your cumulative lower rev ranges counts are so low, the car does not read as being abused, IMO.

NSXavier

If the engine is currently running smoothly and there are no recorded DTC's, there should be no concerns. When you overrev or money shift, the main concern is valve float. When you float valves, you bend valves. When you bend valves, they're bent at that exact moment in time... it doesn't take x amount of operating hours for the valves to bend and a poor running condition to manifest. Running an engine with bent valves will be obvious from the misfires it produces and DTC's the DME records. The ignition counts in range 5/6 is what I look at. If they're in the single digits I generally give the car a pass.

The only cause for concern with the DME report of the car you're looking at is resale. When the DME police review it they'll want to knock $30,000 off the asking price.

JoeFromPA

Agreed. I bought a car with a modest number of Range 4 ignitions which means it revved between 7400 and 7900 rpms, and not too long ago by operating hours. Some (frankly not well educated) people would say "Oh Crap it over-revved by up to 1100 RPMs!".

This engine is damn near exactly the same as the one used in the 997 GT2 RS including the key powertrain components. That engine redlined at 7900 rpms (and could spin higher without damage, to be clear). So now we're worried about the 997 turbo engine hitting engine speeds that the 997 gt2 rs, with the same engine, hit? That's not an over-rev. That's just the way the DME records things. Even Range 5 only tracks up to 9000 rpms which is again in low volume not exactly a concern.

I think the DME report is a huge red herring in particular because meticulous owners/tuners have shown it can register counts it never actually hit. (I.e it can register range 2 and 3s just from being redlined at WOT). It's a DME for the 997 turbo even though the engine was used in high revving engines too with the same DME record keeping. And because of the stoutness of this engine.

I would be concerned about buying a car with Range 6s within a few operating hours of it occurring. This to me would represent a recent money shift with the potential to not be showing damage and you are obviously concerned someone is trying to offload a car they know they did something bad too.

To me the "50 operating hour" rule about Range 5/6 DMEs was about giving the engine time to develop any wear issues related to the over-rev. If the over-rev caused meaningful metallic wear somewhere, it's going to develop very quickly. So give it 50 hours/1000 miles. If it doesn't develop, you are in the clear.

Kevin

Joe, the 997GT2RS Rev limiter is set at 6800RPM's Verified in the ECU mapping.