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Porsche Engine Rev Range Reports

What is a rev range report?

All modern Porsche have a rev limiter, this is what starts to cut the engine revs as you enter the ‘red line’.  Engines have a performance envelope, whereby the engine can cope with a certain maximum rev (rpm) before they are in jeopardy of internal damage.

For many Porsche sports cars, the red line, is something between 6500 and 8500, whereas Formula one cars, are limited to 15000 rpm. Exceeding the design limits can cause serious problems.

Revenge data is stored in the engine ECU and has been from the introduction of the 986/996.

Practically, a 2.7 Boxster is very very low risk, whereas checking the report on a manual transmission GT car would be wise.

For us, we do check and have rejected various Porsche on the basis of the report, only to see them pop up for sale in some other place.

How do over revs occur?

Typically, in a road car, touching the rev limiter is entirely safe, but selecting 3rd gear, when you were looking for 5th or downshifting to 2nd when you were looking for 4th can force the engine beyond the electronic control (rev limiter).

PDK and Tiptronics are not normally at risk, as the clever software prevents missed or incorrect gear selection.

Do you need to be concerned?

On high performance models, cars that might have been driven to experience maximum performance, a rev range check is appropriate.

There are situations that are entirely normal and expected, acceptable, worth checking, or at the extremes, worth avoiding. (See explanation below). But if you want to be safe, speak to our service department to arrange a data check.

In theory, the principles behind Rev Range activity are simple, it’s the variation in data interpretation that causes issues. Excessive engine speeds, especially very recently in the history of the vehicle, are what we are looking for.

Rev Limits. 

Engines are designed to operate up to a maximum rotational speed. The manufacturer uses a rev limiter to prevent engine speeds exceeding a pre-determined engine speed. This engine speed (the red line) is set with a margin of safety built-in, and engines do not typically produce their best power at or beyond the maximum engine speed. Sports models often have a higher rev limit or engine speed.

Over revving.

At full throttle, with the accelerator pedal down indefinitely, the engine can’t and won’t exceed the rotational speed of the limiter. If a driver selects too low a gear relative to the speed of travel (such as selecting 3rd instead of 5th) or selecting a lower gear much too early under braking,  the momentum of the car can mechanically drive the engine past a point of safety. A car with ignitions in rev range should not be an issue or concern, it simply means that the car has touched the rev limiter or perhaps just beyond, that is not a concern. 

Retrieving data.

The ECU will record and store engine ignitions at, or past, the car’s limiter and the operating hours of the last occurrence. On a 6-cylinder engine, there are 3 ignitions per engine revolution, and ignitions are recorded as a cumulative total throughout a cars life.

  • 986 and 996 models have 2 Rev Ranges. Rev Range 1 records ignitions at the rev limiter whilst Rev Range 2 records ignitions beyond the limiter
  • 987, 997, 981 and 991 models can record ignitions in 6 different ranges. Rev Range 1 and 2 record ignitions at or just below the limiter. Ranges 3 through to 6 represent increasingly higher engine speeds.

Shown below are the engine speed ranges for selected models within the Porsche line-up in revolutions per minute.

What’s safe.

Up until recently, ignitions recorded in ranges 3 and 4 were considered by the Manufacturer to be safe with such vehicles still eligible for Porsche Extended warranty. Ignitions recorded in ranges 5 and 6 would not be considered for warranty with existing policies invalidated at the point of over-rev.

Current Porsche warranty procedure (as of 2020) now considers activity in ranges 3 and 4 to be potentially problematic with compression tests and /or oil checks deemed necessary irrespective of whether or not incursions occurred several hundred operating hours prior to the check.

However, in a pragmatic relaxation of previous protocol vehicles with activity in ranges, 5 and 6 will be considered for the extended warranty provided the over-rev activity occurred more than 200 operating hours ago.

Note though that the warranty provision is at the discretion of the importer (so different countries can have different policies for the same scenario), and are subject to the aforementioned compression/oil checks.

Porsche dealers are advised by the manufacturer to disregard over rev data on all PDK and Tiptronic transmission cars when assessing a car for warranty provision. Consequently, a PDK / Tiptronic vehicle with activity recorded as high as Range 6, assuming all other mechanical checks are passed, will be applicable for warranty (accurate as of 2020).

Understanding the data.

An operating hour log captures the exact moment when the most recent activity within a given rev range occurred. When the most recently recorded over-rev occurred is of interest. When the engine rev limiter is exceeded, there is a greater risk of issues, of course relating to how far beyond the limits it has operated and how often and how recently. Industry experts would suggest a 50 operating hour window of danger after the point of a significant over-rev.

The ability to separate genuine incidents from an erroneous recording is critical. No data is perfect. In general, we would consider the registering of less than 10 ignitions within a given range to be no cause for concern. 10 ignitions represent fractions of a second, insufficient time, in our view to cause damage.

Porsche takes a different view and consider the registering of a single ignition (one third of an engine revolution) to be relevant. A single ignition recorded in rev range 3 or higher within a 200 operating hour period means that an engine compression test is deemed necessary.

The registering and recording of a single ignition at such high engine speed, in our view, is just not possible in the same way that a single ignition in, for example rev range 4, can’t follow a single ignition in the previous rev range. In order to pass to a higher engine speed, the engine must complete at least a full engine revolution, a minimum of 3 ignitions.

Tiptronic and PDK equipped Porsches can record legitimate engine ignitions past the limiter; Due to the way the gearbox automatically changes up a gear when the engine speed reaches a certain point it is unlikely but not impossible.

Example Report:

Understanding the Report.

The printout shows:

  • 14788 ignitions recorded at the limiter (Rev range 1). The figure to the right shows when the last incident occurred. In this instance 1430.8 hours.
  • 78 ignitions have been recorded past the limiter (Rev range 2) with the last incident also occurring at 64.4.

The significance of an over rev can only be fully understood by considering it in relation to the total operating hours for the vehicle. In this instance, the car has been used for a total of 1436.6 hours meaning the last rev range 2 activity occurred at 64.4 operating hours well outside of our suggested 50-hour danger window. We are not able to determine the number of ignitions recorded at this moment as 78 is a cumulative total from new.

Calculating the period of time that a car has spent at the rev limiter can also be of use. Using the example of the 996 gt3 above with a rev range 1 threshold of 8200rpm the following calculation can be used:

  • Number of ignitions / 3 = number of engine revolutions 14788 / 3 = 4929
  • Number of revolutions / by rev limiter = minutes spent at limiter 4929 / 8200 = 0.60 minutes
  • Minutes spent at limiter x 60 = seconds spent at limiter .0.60 x 60 = 36 seconds spent at the limiter as a cumulative total from new

Consequently, using the above data. It is not possible to accurately calculate the exact time spent past the limiter in range 2, due to us not knowing the exact engine speed reached on each occasion. We know it to be higher than 8800rpm but we can’t be any more accurate than that. However, let’s look deeper.

  • 78 ignitions /3 = 26 revolutions in Rev range 2.
  • 26/8800rpm=0.0295 of a minute x 60=0.177 of a second at R Range 2. timed at 64.4 hours.

It had just 26 revolutions in rev range 2 for 0.177s (2/10ths of a second). It could not have travelled far past the rev range 2 threshold if it only did 26 revolutions. A true split second, over 1300 hours ago.

This GT3, shows activity in rev range 1, typical of its type, and likely to have touched the rev limiter multiple times over the course of 17 years and 36000 miles. The activity in rev range 2 shows just 26 revolutions, occurring for a cumulative total of 0.177 seconds, and happening at circa 2000 miles shows a driving error long ago. As such it is in a healthy state, has not been abused and has a consistent odometer reading, verus operating hours. This causes no problems.

What else can we learn?

Average car speed over its life. A GT3 may be expected to have spent more time out for a Sunday run at high speed than a daily driving Boxster. In this case, the total mileage of 47827 miles / operating hours 1436.6hours = average speed of 33.29 mph over the life of a GT3. Certainly nothing excessive but naturally higher than your daily driven Boxster.

From that you can ‘guestimate’ the rev range 2 incident happened circa 2000 miles, and that the odometer reading is consistent with the operating hours logged.

An understanding of the significance of rev range activity is important, but so too is a pragmatic approach. A lack of consistency from the manufacturer has turned the subject topic into something often misunderstood or misinterpreted. The principles are straightforward and simple to understand. Understanding the data is important, to avoid panic.

Contact our Service Team to find out more, or to book your Porsche Rev Range check.

 

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