MaxC2S

Wondered if an expert here on the forum can tell me if the following "ignitions at speed" are excessive. This is from the DME report on a 2005 911s.

Range 1 3,603
Range 2 407
Range 3 36
Range 4 0
Range 5 0
Range 6 0

ADias

I see a few rev-limiter interventions. It does not seem bad.

utkinpol

It looks like a good car. Ranges 4+ are bad news, 1-3 are OK.

sjfehr

What do the different ranges mean?

RonCT

Try a search on "over-rev" or other combinations of over-rev, overrev, DME read out, etc. All been hashed out many times before and honestly, I don't remember the exact RPM ranges. There are 3 ignitions in 1 revolution, so divide those by 3 to get the number of revolutions the engine spun at those ranges. 1-3 indicates somebody was frisky with the engine, but didn't blow a shift - if they did, you'd probably see 4-6 on there.

gota911

A 997-1 DME records the following rev ranges:

Range 1: 7300-7500 RPM
Range 2: 7500-7700 RPM
Range 3: 7700-7900 RPM
Range 4: 7900-8400 RPM
Range 5: 8400-9500 RPM
Range 6: 9500-11000 RPM

At 7200 RPM you have 120 revs per second X 3 ignitions per revolution or 360 ignitions per second.

In your case, you car spent the following time in each rev range, assuming the midpoint of each range as the actual RPM.

Range 1 - 3,603 ignitions / 370 per second = 9.74 seconds
Range 2 - 407 ignitions / 380 per second = 1.07 seconds
Range 3 - 36 ignitions / 390 per second = 0.09 seconds

As has been stated earlier, ranges 1 - 3 should not cause you any problems with engine damage or with the warranty. Range 4 gets into the gray area, but revs in Ranges 5 and 6 are red flags for the potential to have warranty voided by Porsche.

Edit: Corrected number of ignitions per revolution and resulting calculated numbers

MaxC2S

Thanks for the input everyone. Makes the decison a bit harder between the 2005 C2S and 2007 C4S i found. need to make a deciosin this weekedn in order avoid somoen else getting one or both right in my back yard.

cviles

Gota911's info is correct except for one minor detail: Modern gasoline engines in cars, trucks, etc. are 4-stroke engines. They have an intake, compression, combustion, and an exhaust stroke and it takes two rotations of the crank to work through all these cycles.

So at 7200 rpm, there are 360 ignitions per second instead of 720. His information about what each of the rpm ranges mean is otherwise correct.

DJ23

Tim and Chris thanks for the info. Learned a lot in this thread.

Jay

gota911

Chris, thanks for catching my mistake!

I have edited my original post to reflect 3 ingitions per revolution.