Hit the Rev Limiter

[Rail26]

I hit the Rev Limiter on accident today. Any damage that I might need to be aware of? She seems to be driving fine and I didn't notice any changes.

[MNBoxster]

Hi,

Nope, that's what the Rev Limiter is for - to pull the plug before you blow-up the motor.

So long as the engine is in good tune and overall good shape, and your oil & coolant levels are good, you can bounce off the Rev Limiter all day.

Happy Motoring!...Jim'99

PS BTW, Helicopters don't Fly, they beat the air into submission!

[lexuspilot]

As long as it was on the upshift and not the downshift you are okay. Which, I guess it was since you said it bounced off redline.

[Brucelee]

"So long as the engine is in good tune and overall good shape, and your oil & coolant levels are good, you can bounce off the Rev Limiter all day":

Well, not really. I can think of several negatives here:

1-Even if you engine doesn't blow at that time, you are shortening your overall engine life. Wasting tons of gas too!

2-Each trip to the rev limiter is recorded by the ECU. This is read when you get your car serviced at Porsche and if you are under warranty, can SOMETIMES be used to deny an engine warranty claim. The data becomes part of your PERMANENT RECORD!

3-If you are going this fast all the time, the Police and the local tire dealer will be your best friends!

Happy motoring!

[Rail26]

I rarely engage in that type of driving, in fact, I was trying to merge on the highway and wasn't paying attention to what gear I was in because an 18 wheeler was trying to be a funny guy and not let me on. Anyway, I hit the gas not realizing what gear I was in and hit the limiter.

I am very conscious about my driving style because I DO NOT want to be one of those horror stories where Porsche decides not to honor its warranty.

[Brucelee]

Sounds very sensible to me!

Good driving!

Originally Posted by Rail26

I rarely engage in that type of driving, in fact, I was trying to merge on the highway and wasn't paying attention to what gear I was in because an 18 wheeler was trying to be a funny guy and not let me on. Anyway, I hit the gas not realizing what gear I was in and hit the limiter.

I am very conscious about my driving style because I DO NOT want to be one of those horror stories where Porsche decides not to honor its warranty.

[MNBoxster]

@BruceLee,

I agree with you on points 2 & 3, but these are consequential, not Mechanical, issues to hitting the Rev Limiter, and I took the lister's queery to mean the Mechanical issues.

I disagree with you on item 1. There is no problem running the Engine at these speeds. The engine was designed to operate at this speed. The Performance numbers are derived from this. Peak HP is usually at or near Red Line. It does not increase the wear on the Engine, assuming, as I previously stated, that the overall condition of the Engine is good and that the fluid levels are proper. According to your reasoning, it would be better to operate the car at idle than any other RPM and we know this isn't the case. Engine Cooling and Lubrication are Crank Speed dependent (the Waterpump and Oil Pump are powered off the Crankshaft), so running at higher RPMs insures that these systems are operating at 100%. This is the primary reason why idling your car excessively will induce greater wear.

Plus, the manufacturer most always adds a Fudge Factor when determining a Rev Limit to minimize warranty claims and the like. I once spoke with a Lotus Engineer about my Esprit which hits the limiter at 7,200RPM. He stated that the engine was good for about 9,000RPM before there were any problems. And, that at 9,000 RPM, it was the Ancillaries (Alternator, Waterpump, AC Compressor), not the Engine, which were the limiting factor. He further said that only at about 11,000RPM were there any Engine problems, and this from the valvetrain, not the Reciprocating gear.

@LexusPilot,

I agree with you re. Upshift vs. Downshift. But want to point out that upon downshifting improperly, it is possible to exceed Red Line RPMs, there is no Mechanical safeguard in place to prevent this from happening.

Happy Motoring!...Jim'99

[gRed04]

Originally Posted by MNBoxster

I agree with you re. Upshift vs. Downshift. But want to point out that upon downshifting improperly, it is possible to exceed Red Line RPMs, there is no Mechanical safeguard in place to prevent this from happening.

Please help uneducated here. I don't understand why downshifting allows you to over rev? I thought the limiter was rpm dependent.

[MNBoxster]

Originally Posted by gRed04

Please help uneducated here. I don't understand why downshifting allows you to over rev? I thought the limiter was rpm dependent.

Hi,

A Rev Limiter prevents the Engine from making too high revs, but it doesn't prevent it from actually spinning that high.

A Rev Limiter usually works in one of two ways. It can completely cut out the Ignition Spark and/or Fuel Pump (this is referred to as a Hard Limiter) and the engine suddenly stops making power and subsequently very quickly drops below Max RPM). Or, the ECU (DME in Porsche Parlence) will selectively cutout every other cylinder (referred to as a Soft Limiter) which again, drops the RPMs back into the safe range.

But, if you are downshifting, the speed of the Rear Wheels can be exceeding the RPM range for the Engine. When you let out the clutch, you can cause the Crankshaft to turn at the same speed as the Transmission's Primary Shaft. Since the Engine itself isn't doing this, cutting the Spark and Fuel will have no effect, and the Engine can spin higher than Max allowable RPMs. But, you'll probably tear up the Clutch, Throwout Bearing and such, so you'll have a plateful of issues to deal with. Hope this helps...

Happy Motoring!...Jim'99

[Brucelee]

Based on several studies conducted, overall engine life is correlated inversely with average RPM and % of throttle utilized, ie acceleration rates.

Simply put, reving the engine like a mad man and hammering the throttle shortens engine life.

The last study on this subject was in Panorama magazine some months back and the source was ........Porsche.

Originally Posted by NBoxster

@BruceLee,

I agree with you on points 2 & 3, but these are consequential, not Mechanical, issues to hitting the Rev Limiter, and I took the lister's queery to mean the Mechanical issues.

I disagree with you on item 1. There is no problem running the Engine at these speeds. The engine was designed to operate at this speed. The Performance numbers are derived from this. Peak HP is usually at or near Red Line. It does not increase the wear on the Engine, assuming, as I previously stated, that the overall condition of the Engine is good and that the fluid levels are proper. According to your reasoning, it would be better to operate the car at idle than any other RPM and we know this isn't the case. Engine Cooling and Lubrication are Crank Speed dependent (the Waterpump and Oil Pump are powered off the Crankshaft), so running at higher RPMs insures that these systems are operating at 100%. This is the primary reason why idling your car excessively will induce greater wear.

Plus, the manufacturer most always adds a Fudge Factor when determining a Rev Limit to minimize warranty claims and the like. I once spoke with a Lotus Engineer about my Esprit which hits the limiter at 7,200RPM. He stated that the engine was good for about 9,000RPM before there were any problems. And, that at 9,000 RPM, it was the Ancillaries (Alternator, Waterpump, AC Compressor), not the Engine, which were the limiting factor. He further said that only at about 11,000RPM were there any Engine problems, and this from the valvetrain, not the Reciprocating gear.

@LexusPilot,

I agree with you re. Upshift vs. Downshift. But want to point out that upon downshifting improperly, it is possible to exceed Red Line RPMs, there is no Mechanical safeguard in place to prevent this from happening.

Happy Motoring!...Jim'99

[limoncello]

The engine should be able to take frequent revs. It's a Porsche and part of the driving experience is "spirited" driving.
Having said that, the history books are filled with cars that did, and did not, meet the standard. Triumph TR4 and TR6 engines were noteworthy for their reliability (yep, much of the rest of the cars were junk). The GT6 was known as frail - the transmissions and gearboxes couldn't take the load of the 6 cylinder engines. History will judge the Boxsters honestly and openly (this differs from a marketer's hype or the lawyer's esculpatory warnings).
Second thought: there was much concern in a recent thread on rev-matching so as not to load the drive train. Frequent accelerations also load the drivetrain. Still, a Boxster should be able to take repeated accelerations, braking, and even downshifting - all normal attributes of spirited driving. Equally true though, if you can drive "smoothly", it will last even longer. On the road or on the track, smoothness counts.

[lexuspilot]

So then what would be better:

The lack of revs(storing a car long enough for moisture to work it's magic)

or

Hitting the rev limiter.

The $65,000 question.

Actually Rail, this rev limit bounce is only a problem for the person who buys your car

[Brucelee]

"The lack of revs(storing a car long enough for moisture to work it's magic)"

From the standpoint of engine longevity, this is probably not the correct way to frame it. I am certainly not suggesting you park your Porsche to preserve it.

I think the data shows that driving your Porsche to the red line on a daily basis will certainly shorten the drive train's life vs. a more prudent way of driving.

This is supported both in theory and in practice.

To wit, the useful life of just about any race car is very very short, even though these cars are built to specifically run at top RPMS (blue printed engines, forged metals, oil changes at every race etc.).

If running these cars at top RPM was "good for them" they would have a nice long lifespan.

They do not.

Nor will your Porsche if you hammer it day in and day out.

I am not suggesting that you leave it in the garage or not engage in spirited driving. Simply understand that trips to the rev limiter create a cost.

If this were NOT true, why would Porsche keep track of these trips for warranty purposes?