Hit the Rev Limiter
 

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.

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! :)

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.

"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!

:cheers:

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.

Sounds very sensible to me!

Good driving!

:cheers:

@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

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

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.

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.

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:eek:

"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?

:cheers:

Hi,

I think your argument is somewhat superfluous. Your Race car analogy is somewhat off base as this is a car who's Engine differs in many ways to a Street Car Engine, such as in Compression, Timing, A/F mix, etc. Apples to Oranges. Besides that, a Race Car Engine is run about 75%-80% of the time at Red Line (if you plan on being Competitive), whereas we're only discussing occaisionally, or accidentally, bouncing off the Rev Limiter.

Lexuspilot has taken your logic to extreme, but he's not all wrong. Simply turning the key will eventually wear out the Engine. That's what Engine's do, they wear out, no matter how well you care for them, eventually all the heat and friction takes their toll.

I don't dispute that empirically you increase wear and/or shorten the Life of the Engine. But, you need to put some perspective to this. You may have a rebuild due at 100K rather than at 120k. That doesn't mean it's gonna Blow-up tomorrow.

Plus, there are many other ways of ignoring or abusing your Engine which will shorten it's life much sooner such as running low on fluids, buying Bad Gas, not allowing it to warmup sufficiently when it's cold, (which is probably the greatest sin committed - You know that little Blue mark on your temp gauge? You're supposed to allow the Temp Needle to travel North of it before driving, how many people do this consistently?).

No, I am not convinced that hitting the Rev Limiter, even on a consistent basis is much to worry about so long as you look after the car's Tune and Fluids. Every Engine I've ver seen Blow-up was from some other type of abuse, usually neglect.

Happy Motoring!...Jim'99

"No, I am not convinced that hitting the Rev Limiter, even on a consistent basis is much to worry about so long as you look after the car's Tune and Fluids. Every Engine I've ver seen Blow-up was from some other type of abuse, usually neglect."

I understand that you are not convinced and that is not my intention. You can drive your car off the rev limiter everyday and that is fine with me. However, it is factual that heat, friction and mechanical stress all act to increase wear in ANY engine, not matter how well maintained. Same applies to the drivetrain. So, all of these increase greatly as revs climb and the gas pedal goes rapidly to the floor.

As long as you understand that you are shortening your engine life, that is fine as it is your car.

Don't delude yourself into thinking that keeping your oil clean and plugs new is going to eliminate this "cost" as it will not. It will help but there is not cheating the man!

Also keep in mind that blowing up an engine and decreasing useful life are not necessarily the same thing. However, I would bet more engines "blow up" at red line than at 2500 rpms.

Lastly, if I understand your point about engine warm up correctly, it conflicts with every professional's advice that I have seen, which is to allow your cold engine to run about 10 seconds, drive off slowly and allow the engine to warm up quickly under light load.

AFTER the engine is fully warm, one can get more aggressive with driving.

If I understand what you are advocating, you would sit in the driveway until the temp gauges moves. Did I get that right?

If so, this theory went out with the 60s I believe.

Continuing the debate -
Rail, IMHO, bouncing the rev limiter did no damage to your car.
Warm-up: Not as critical as it used to be, for starting and driving normally. I think the manual even says you can turn the key and go. As an old-schooler, I still let my cars idle for 5-10 seconds before I pull away - it's just habit. Here's the distinction: I never drive hard (aggressive throttle, or above 3500 RPM) until the car is FULLY warmed. If the car has been sitting for 3 weeks, I warm it up carefully.
High RPMs: Yes, continuous high RPMs (the race car) will burn up a motor quicker than all gentle driving. But sports cars, like Porsches, should be able to take 100,000 miles of driving by Porsche owners. Running the revs up smoothly on a regular basis should not burn the car up prematurely.
Smooth is a key word. Slamming the drivetrain wears out parts. (Many an SUV'er does damage to the soccer van by rolling backwards and dropping the automatic into drive while still moving backwards. That's bad.)
Porsche and the Economics of Warranty Work: The rev limiter is an easy target because it's measurable. It's easy to say that high RPMs = abuse. Sometimes that's correct, and sometimes it's not. Running the revs up smoothly is a joy, and personally, I don't think that alone should blow my motor early. (Track time might, however, which I do. Explains why I have a car that's out of warranty - no one would touch it after repeated trips to the track. If it breaks I'll fix it.) But Porsche is erring on their safe side - not surprising, they are a business enterprise. It's probably true that some drivers lose some deserved warranty work solely because they rev'd out a few times, but equally true that other owners wring the crap out of the cars and then take it to the dealer to fix it under warranty. And the SUV owner that puts it in drive while rolling backward gets their car fixed under warranty, simply because there is no strain gage on the driveshaft. Yet.
Back to Rail: IMO, no mechanical damage done, but your dealer may try to convince you otherwise at some future moment.

Lemon

As usual all good points.

According to my service shop, the computer tracks all overrevs.

This is not an automatic warranty no no.

However, if they see 50 or so of them,

Well........................

Good stuff.

:cheers:

Correlation versus causation, the usual logical fallacy! High engine revs can't be shown to *cause* premature engine failure, but there are other htings to take into account. If you're the type of driver that likes to drive the car hard, there's a lot of other stress factors involved than just how many times you revved the engine.

But even if there is a correlation, that doesn't make me comfortable with Porsche using computer data that states how many times you've hit [whatever] RPM as a tool for denying warranty claims. It is not proof of any sort that you've mistreated the car... well, except for really obvious over-revving of course...

Lets try this.

Does racing a car lengthen or shorten its useful life?

Do you want to buy a car that has been raced?

Does racing involve high revs and tremendous internal stresses?

Does daily trips to the redline lengthen or shorten an engines useful life?

Do manufacturer's in general have a qarranty disclaimer for racing or other forms of abuse?

:cheers:

OK, let's say you were interested in buying a used Boxster from a Porsche dealer. And you wanted to see how many times, if any, the previous owner bounced off the Rev Limiter. If the dealer actually gave you the data (you could make the final sale conditional on this data) off the ECU (DME) how could you decifer the codes? Could you tell how many times they bounced off, if they gave you the data off the ECU??

I am not going to study all the messages.

The question was from a 987 owner.

There are now 7 ranges, at least with the 997.

When we say life or premature here are we talking in Miles, RPM's, or Years.


I think everyone is using a different yardstick for engine life.

Miles, hours, revolutions, years,?

You could also take into account engine acceleration. Is bouncing off the rev limiter in fifth different than bouncing it in first or nuetral?


What I don't know is what happens to an engine when you stall it. This has to happen at a much higher rate than rev limiter bounces.

Wow, really stirred up the pot on that one! I usually don't go above 5000rpm on a consistent basis because I'm not sure what Porsche considers "warranty voiding". Quite honestly, I'm worried what type of driving may ward the warranty. Call me a wuss, but I couldn't and wouldn't want to rebuild the engine because the warranty is no longer valid. I bounced on the rev limiter once...hope that doesn't screw me in the end.

No you will be fine.

The warranty only comes into play when there are many many hits and the service folks suspect racing and/or abuse.

Fun topic actually.

Thanks for the question!

:cheers:

Porsche has to expect this car to be driven like a sports car.

They have to protect themselves from abuse and ignorance; they shouldn't pay for missed downshifts etc.

But, there was a comment from Porsche in an article about manufacturers voiding warranties for DE days, lapping, track use, and even autocross. Seems Mistubishi owners that autox were finding their warranties voided. The Porsche comment said something like "We are not going to refuse coveredge for someone enjoying our product to the fullest, but you cannot expect us to finance someones racing season with warranty work." Now I am 95% sure it was Porsche 5% chance it was Ford. Subaru was bashed for also trolling autox results and voiding warranties.

I short shift some because I am cruising or just getting around but I rarely drive that I don't get on it through the gears. It just doesn't sound good until 5k.

My favorite thing about the base boxster is I can race around and it feels fast and sounds incredible, but I stay pretty legal.

Hi,

Wait a minute here. You are carrying your examples to extremes to justify your arguments. NO ONE said anything about Racing. This was an example you brought up.

The Lister simply inquired about the Damage Potential of hitting the Rev Limiter ONE time. I said that this wasn't a problem and all of a sudden, we're talking about Racing and Warranty Claims.

Realize that Porsche has the ability to set the Rev Limiter to whatever Threshold they choose. This isn't some arbitrary number (although I would probably concede that there are more factors than merely Engine Preservation factored into their decision, such as the Marketing Potential of achieving certain Performance Parameters such as HP and Torque). I suspect that the Power Curve trails off at or just before RedLine. This means if you want to derive the maximum potential the car has to offer (and don't forget this is a Sports Car, driven largely by Enthusiasts) you're going to enter these Nether Reaches of the Tach. Porsche knows this too.

I further concede that I would not drive My car in a manner which hit the Limiter on every shift, or even every day (as you allude to), or week. But, when I'm out to take a Run or in any Competition, I want the car to Deliver the Goods, this means exceeding 6k Revs when appropriate.

I have developed a good deal of Mechanic Skill through the years and keep my cars in top shape. I have somewhat of a reputation among the Formula Vee crowd with whom I compete as having one of the most reliable cars, very few Mechanical Failures and DNFs by comparison to the rest of the field. Yet, I am one of the most Competitive and beat the P*ss out of the car on the Track. Where's your Cause and Effect here? As pointedly mentioned by another contributor, it's how you drive the car, over at what RPM range which will, to a great part, determine the car's longevity. I am smooth and very easy on my cars, despite pushing them to their limits. This is why they last. Most FV engines require a rebuild annually or every other season. Mine has averaged every 3-4 over the 14 years I've owned it. In large part, the Rules see to it that all the engines are basically the same, so how do you explain this if not for the effect of the Driver and proper maintenance?

Further, I realize that at some point in each of my cars that a rebuild will be necessary at some point, this is part of the Pkg. when owning Performance Cars longterm - you gotta Pay to Play. I try to hold that day off until absolutely necessary, but not if it means I have to drive like an Old Lady. If that's your point, those people would be much better off in a SunFire.

The 987S develops 276 bhp and 236 lb-ft of Torque respectively and this is often one of the arguments made to queeries about which model to buy - Base or 'S'. But, these numbers are only achieved at 6,200RPM and 4,700RPM respectively. If you are one of those guys who never exceeds 5k RPM, you're never gonna see this performance anyway, so buying the 'S' is a waste of time, if buying it solely for it's greater performance potential. On the other hand, a Base model driven to it's Max can realize more performance than the aforementioned 'S'.

Of course manufacturers build-in the Caveat of denying Warranty Claims against Racing or other Competition. Not usually because the cars can't take it, rather because all Drivers, or Owners are not the same. My cars are driven Hard, but, they are not abused. They are driven and maintained properly. Every car I've ever sold was sold for usually more than I paid for it, despite being very forthcoming to the Buyer about how the car was used. Their Test Drive, PPI, and complete Service Records (incl. every fill-up and Oil Change) tells them that the car is in excellent shape regardless of it's past use. Further, I have never had a Buyer come back to me with any complaints about a car I sold them. I have owned 43 cars in my life and currently own 5, so I've sold a few of them through the years.

So, to conclude, how you drive your car and maintain it is much more important in preserving it's life than an occaisional run to Red Line. If you want to keep bringing these extreme examples into the discussion, I suggest you start another thread on these topics, because they are not really germane to the discussion here. In that context, you may find that we're not so much in disagreement as you think.

Happy Motoring!...Jim'99

"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."

This was the one statement that I addressed. I think you made it.

My assertion is, if you "bounce off the Rev Limiter all day long" you are shortening your engine life.

I stand by that statement and I think any prudent, knowledgable person would.

Here is a test:

Next time you try to sell a car, tell the prospective buyer that you "bounce off the rev limiter all day long."

Tell him its OK though as you keep the oil clean and topped off and the coolant too!

See how many prospects end up walking away.

Off course, infrequent trips to Red Line are fine and I never said otherwise.

Keep bouncing the limiter if you want. Simply don't delude yourself that this is a cost free strategy.

As I indicated in one of my post, this issue was addressed in Panorama by the tech guy there. I think the article backs up my statements.

No one is attacking you, I simply think your assertion is not supported by fact.

:cheers: