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I have a 2013 Maxima and I'm wondering whether its computer would have recorded the highest RPM it has attained in the past.

Is this something all modern cars are able to do? The dealer closest to me says it can't be done, but there's another dealer about an hour away that says it can be done. Not sure who to believe here.

  • You could write code which would record it, but to my knowledge no car manufacture does this as a standard feature. – Pᴀᴜʟsᴛᴇʀ2 Mar 5 '17 at 5:22
  • Tach-o-graph! Reminds me of the old days. – zipzit Mar 7 '17 at 23:25
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The car manufacturers do this because they want to detect misuses of the engine. If the car has a manual transmission and somebody downshifts at high speed to overrev the engine, it will be recorded into the car computer's memory and thus if the engine suffers damage, the dealership can determine that the reason for the damage was overrevving. Thus, the warranty doesn't cover this failure.

Now, how is it actually done? One possibility is that the maximum RPM the engine has attained is stored no matter whatever RPM it is. Another possibility is that it is only stored if the maximum RPM exceeds the redline. This probably varies from manufacturer to manufacturer.

If one dealer said that they can determine the maximum RPM, chances are your engine implements it in the former way, i.e. storing the actual maximum RPM even if it doesn't exceed the redline.

  • Do you have any specific examples to support your claim? Ive seen aftermarket loggers that do this but not stock ecu's. – Sir Swears-a-lot Mar 5 '17 at 8:03
  • I recall reading about this in Toyota Yaris service manuals obtained from Toyota. Unfortunately, I don't have access to those manuals anymore. – juhist Mar 5 '17 at 8:09
  • This link shows that at least Porsche 911 records timing of over rev events: 911virgin.com/porsche/rev-range-information – juhist Mar 5 '17 at 8:13
  • This also shows that over rev events are recorded: pistonheads.com/gassing/topic.asp?t=1337507 -- so there's plenty of evidence online that ECUs do in fact store information about overrevving. – juhist Mar 5 '17 at 8:14
  • Nice link. I concede defeat. +1 for your effort ;) – Sir Swears-a-lot Mar 5 '17 at 8:15
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Yes, exceeding maximum can be recorded and probably most ecu does this because it does not require rocket science to record a value in ecu.

Im my opinion, ECU would record only if the maximum was exceeded. Otherwise it would need to continuously check if(CURRENT_ENGINE_SPEED > PREVIOUS_MAXIMUM_ENGINE_SPEED) update_value(). Purely from an engineering standpoint, this would be waste of CPU cycles since nobody cares as long as the values are within limits.

Do you care if it recorded that you drove any RPM inside normal values? Because using engine within its limits won't effect your warranty and nobody can blame you for doing so :)

How you access this information is probably manufacturer dependent.

For example in VW cars this can create an error entry which you can't clear. See P1560 and maximum engine speed limit exceeded.

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