Saturday Night Thoughts about DME Reports

After reading multiple people go back and forth about the DME Report from the GT2 posted on BaT and compare it to a regular 996 regarding what Range and hours and severity, I sit here watching Bruins pregame show while enjoying a macrobrew (Miller High Life, it's the champagne of beers) And I realize I have forgotten so much about gasoline engines to truly understand what the ramifications are of the DME report. For ten years or so, other than my motorcycles, I've driven diesel cars and trucks plus worked in the industry for a few years so I haven't seen a tach north of 4500-5k in a long time. Why is it important? It only seems like it's proactively posted by enthusiast listings but always discussed when a used dealer happens to have a 911. Also what do the hours mean? Hours since occurrence? What triggers it? I get that there are different ranges. If I sit in my driveway and smash my 911 off the rev limiter, will that cause X amount of instances? Is it just the ECU seeing a signal from the tach that can't be possible? Or do I need to "money shift" it to cause an instance in the DME? How common is it? Should I get a Durametric/have my indy run a report? My 911 was used as a daily drive for years hence 130k miles. Ok the Bruins are about to start and I'm on the macrobrew movement board! -G

Nine question marks. Looking forward to your answers.

I'll bite since I have too much personal knowledge on this. On our cars, I would not worry about the first level of over revs. This is hitting the rev limiter. So to answer your question, if you sat it your driveway, and mashed the throttle, with the car in neutral it would trigger multiple level 1 over revs. 3 over revs for every full rotation of the motor (I believe). The level 2 over revs are the bad ones. This is a mechanical over rev. Something the DME could not protect you against blowing the motor. The person writing this may have triggered 273 level 2 over revs. 70 or so revolutions. I was doing 100 (on the track) and went from 4th to 1st. Car made it 2 more laps, but that 70 revolutions resulted in a connecting rod salad in the sump. So long story short. Lots of level 1 over revs, the owner DROVE the car. Level 2 over revs, you could be lucky depending on how bad, or your day is about to be real bad. The newer cars have several more levels, so the math is a bit different. I don't think you need to be worried until level 3 or so.

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I don't have any answers. shrug So just going over the limit isn't a trigger for a single over rev? Every specific revolution of the engine triggers a DME "event?" Am I reading that right?

its only necessary on tracked cars imho. gt-2 gt-3 If the information is there why not use it? In reality 97% of these cars change hands with no DME reports and less the 1% of vehicles overall change hands with any type of rev range report. On BAT it is quite simple. nerd on the couch wants to show others online how smart he is by asking for a dme report. Kinda like teaching a baby a new word and they keep repeating it. The people who ask about DME reports NEVER bid on anything and are annoying to me.

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If you hit the Rev limiter (where the car loses power to save itself) it will register a a level 1. So yes. hitting the rev limiter will register three level ones for every revolution, but the level 2s are the ones that could be bad. All maps to the amount of hours on the motor. If there were dozens or hundreds of hours from the level 2s to current time, things likely could be okay. For instance, my DME currently show 272 leve 2 over revs. Those over revs were fatal to the motor. If I ever sell my car, I will have to show the photos of the blown motor, and the new motor that I installed in the car. The fatal over revs of my motor will always be there (unless I get a new DME). All that being said, I have 200 hours on the DEM since those fatal over revs. Long story short, if lots of hours have passed since the level 2 over revs, you are likely in okay shape, bust still, ALWAYS SPEND TOO MUCH MONEY ON A PPI.

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Didn't pay for a PPi, took a train 4 hours to my 911 and drove it home 4 hours sight unseen https://rennlist.com/forums/996-foru...ro-thread.html Did a POST purchase inspection with a really good local indy, didn't mention my DME report, Should I bring it back and ask?

From what I have gleaned here if 50 hours have passed since the last type 2 over rev then probably okay.

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At this point you own the car and the DME report would be for information only. I guess the better question is how would you respond to the information that was in it? If you planned to rebuild if you see any level 2 then sure have it done. If you plan on driving it then don't scare yourself with the dme.

I will echo the above...Don't worry about range 1 over-revs unless they are way excessive. For range 2, none is best but if there are some and they occurred a long time ago then if something bad was going to show up resulting from it then probably would have already. If they were very recent I would be more concerned.

Quick post as for some miraculous reason my wife and son are still asleep. I look for the usual over revs but also for service hours and times the car has been started. What I do is to divide the miles by number of starts. A car with low miles per start may not be ideal as it probably never got to warm up real well in most circumstances. i.e., saw a very nice 2015 with under 10k which had an average trip of less than two miles. Also, I divide miles by service hours to get a sense for type of driving. Saw a car with an average speed of less that 8 miles. Probably a stop and go car with 20k miles .... or it just sat in the garage warming up before it was driven. My previous 997 had an average trip of 27 which was very consistent with my boss� boss commute. The average speed was low 30s. Had 48k miles but very low cycles and drove like a 10k mile car. My new (to me) C4S has an average trip of 5.8 miles and an average running time of close to 17 minutes if I recall correctly. Average speed in the low 20s. I was able to confirm with previous owner that she drove it across suburbs to work three times a week. Did I mention 0 over revs in 1 or above? Finally on the 991.2, saw a bunch with plenty over revs in 3 (with PDK) but because none on 4 (or above) they where CPO. Here I was able to figure many of these have been tuned and the tune allows for a higher red line. Saw an immaculate one with less than 5k but with almost 3,000 in rev 3 with very high starts and low operating hours. When I asked a bit more identified a previous owner who loved to hit the rev limiter every morning on every light. Car was fine but wonder how that engine will do down the road. The math may no be exact, but there is more to these numbers. They tell you a story. PS. On a PDK they won�t share with you because �it is a PDK and it can not over rev�. Somewhat true by a non modified PDK car should have very few in 1 and less in 2. Never in 3 .... yet many have them. Also, they mostly won�t share the start cycles as most sales guys have no clue. Ask and ask. They will eventually will share.

Have a read of this: http://www.911virgin.com/porsche/rev-range-information/ A PPI includes over-rev information - its important to know when it occurred because there is a safe and not safe time - 150 hours post the event the engine is deemed "safe" pre 150 hours the engine is "in danger of failure" according to Porsche techs i've spoken to. This was used for pre-certified used criteria etc.

What’s the redline in a 996?

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Depends on the model of 996. Which one are you speaking about?