Rev Limiters

A friend and I are having an argument, so I thought I'd come to the most sane board on the net for some help. I told him that I bounced off the rev limiter in my E30 the other day on purpose and he was astounded. He said he would never do that because it's stupid. I maintain that there's nothing wrong with it...I'm not sitting on the limiter for an extended period of time. Just a quick bwaap bwaap bwaap and I shift gears.

Who's right, he or I?

I've never had a car with a rev limiter, but I'd say that's absolutely fine. That's what it's there for, right? To stop the engine over-revving and causing damage.

The rev limiter does not hurt anything, but i do not think it should be used as a substitute for a shift light.

I'm with Luke here. The factory wouldn't install a rev limiter that was high enough to cause engine damage.

I hit the limiter in my Mazdaspeed Miata more than I care to admit. There are a lot of people who never spin their engines anywhere close to the redline...take a ride with my father-in-law.

He thinks anytime I rev above 4k that I'm doing something wrong.

It depends on how it is done. Some cut fuel others ign and other do both.

Cut fuel type make it go lean at high rpm not good.... Ign cutters can be hard on plugs. All can be hard on bearings and rod bolts. as your not applying a downward force BTDC thus the piston will want to continue its travel to the head.

44

Go to an autocross and just listen. You'll hear lots of people bouncing of the limiter, for probably longer than you did.

I wouldn't use it to limit my speed during my commute, but you won't hurt anything hitting it every once in a while.

There's absolutely nothing wrong with it.

Go to an autocross and just listen. You'll hear lots of people bouncing of the limiter, for probably longer than you did.

Even better might be a rally-x, just cause you are hitting the rev limiter doesn't mean you've hit top speed in the gear you are in! When I had my sprint turbo w/ straight pipe, it would be wailin' away at 7500rpm, 14 psi and then rev limiter bwaa bwa bwa bwa shift The most hilarious part is when the RFL blow off valve starts chattering away with the rev limiter. Some of the best noises I have ever heard!

The first thing I do with a car after I buy it. Hit the limiter in first and second gear. If it survives that, then the car usually doesn't give me any problems.

MCarp22 wrote: but i do not think it should be used as a substitute for a shift light.

Oh yeah no doubt, I had just never done it before so I took it as far as I could.

Time to go tell him I win.

realize, that by asking your question here you were destined to win.

ask the same question somewhere else, say Consumer Reports and you might get a different (and wrong) answer.

HiTempguy wrote: The first thing I do with a car after I buy it. Hit the limiter in first and second gear. If it survives that, then the car usually doesn't give me any problems.

So much for break-in procedures...

TJ wrote: realize, that by asking your question here you were destined to win. ask the same question somewhere else, say Consumer Reports and you might get a different (and wrong) answer.

Hence the reason I came here. The average level of idiocy is much lower here than everwhere else.

Gameboy, I'm going to go out on a limb here and say that he is probably referring to used cars.

One of the teams at 24 Hours of Lemons Toledo (Detroit-ish) lost all but 2nd gear in his (chipped)) 325e after 2 hours.

So from then on it was 22 hours of rev limiter, with a few seconds here and there per lap where the car was slower than 50-55mph. He was waiting for the rain to come back so he could swap the trans out during a slow period. Never happened

My respect for BMW engines went up megafold after that.

OTOH, I've seen someone lunch an EJ25 Subaru mill by bouncing the limiter. Subaru DOHC engines are... funny. They have lots of guides to prevent the belt from jumping off of the pulleys, so they HAVE to have weird harmonics going on. (Automatic versions do not have the guides, per the service manual... have never dug that deep into an automatic DOHC before) Supposedly going to an aluminum crank pulley also causes belt jumping.

And rotaries hate high load + high RPM rev limiter. The shocking kills the stationary gears and in a turbo engine can cause side housing cracking.

Here's an (in)famous blown rotary, the cause, at least as far as they could tell, was holding it on the stock ECU's rev limiter for about 5-10 seconds at a certain place at Buttonwillow because it was faster than upshifting... http://www.fc3spro.com/TECH/HOF/K2RD/k2rdhof01.html

Supposedly they just cranked oil pressure up, use an aftermarket ECU with the limiter set to something they never reach (9400?) to safety the engine from a missed shift, and they have no more problems.

noisycricket wrote: And rotaries hate high load + high RPM rev limiter. The shocking kills the stationary gears and in a turbo engine can cause side housing cracking. Here's an (in)famous blown rotary, the cause, at least as far as they could tell, was holding it on the stock ECU's rev limiter for about 5-10 seconds at a certain place at Buttonwillow because it was faster than upshifting... http://www.fc3spro.com/TECH/HOF/K2RD/k2rdhof01.html Supposedly they just cranked oil pressure up, use an aftermarket ECU with the limiter set to something they never reach (9400?) to safety the engine from a missed shift, and they have no more problems.

Daaaayum! I'll make sure never to do that with my FC...

I have yet to bounce my R/T off the revlimiter, mostly because before now it has had a crappy rice can.

Yeah even my stock 5.0 likes 7200rpm burnouts. Take that 4 cylinder guys!

44Dwarf wrote: It depends on how it is done. Some cut fuel others ign and other do both. Cut fuel type make it go lean at high rpm not good.... Ign cutters can be hard on plugs. All can be hard on bearings and rod bolts. as your not applying a downward force BTDC thus the piston will want to continue its travel to the head. 44

Fuel cutout would be my choice. The fuel is not a lubricant nor coolant in a modern engine. Ignition cutout with out fuel cut out could foul plugs, unlikely tho for the short duration involved.

As for damage to bearings from no downward pressure, the engine is still on a compression stroke only with out spark to create the power stroke. Meanwhile the opposite cylinder is on an exhaust stroke and will soon change direction for an intake stroke. This happens with every revolution of the engine.

I brought up the subject again tonight, he still holds true that he's correct and that it's dumb to hit the rev limiter. Whatever.

jpod999 wrote: I brought up the subject again tonight, he still holds true that he's correct and that it's dumb to hit the rev limiter. Whatever.

You can tell him that the limiter on a BMW retards the timing and in no way causes engine damage. In fact, when I ran my M3 at Pocono I would drive all the way down the back straight on the limiter in 5th, every lap.

The motor is still going strong years later.

porksboy wrote:

44Dwarf wrote: It depends on how it is done. Some cut fuel others ign and other do both. Cut fuel type make it go lean at high rpm not good.... Ign cutters can be hard on plugs. All can be hard on bearings and rod bolts. as your not applying a downward force BTDC thus the piston will want to continue its travel to the head. 44

Fuel cutout would be my choice. The fuel is not a lubricant nor coolant in a modern engine. Ignition cutout with out fuel cut out could foul plugs, unlikely tho for the short duration involved. As for damage to bearings from no downward pressure, the engine is still on a compression stroke only with out spark to create the power stroke. Meanwhile the opposite cylinder is on an exhaust stroke and will soon change direction for an intake stroke. This happens with every revolution of the engine.

Its the brief lean condition before there is no fuel at all that results in a heat spike in the head. It can cause everything from deformation to a hole in a piston - especially at high revs and load.

I hit the rev limiter at times in my LS engines - sometimes I ride it instead of shifting based on track position.

Does not hurt a modern engine to hit the factory rev limiter.

Remember downshifts cannot be rev limited and that will do ugly things to your engine....

if the ecu is cutting injector firing events(on a mpi engine) rather than the fuel pump, there won't be a lean period, there will just be no fuel.

Fuel cut limiter there's no lean condition, it just might 'look' lean to an O2 sensor based on excess air.

I drag race so I have a lot of experience with rev limiters. I sit on the stock style limiter (ign retard, fuel cut) for about 10sec in 2nd gear for every burnout and chirp it on my 1-2 shift every pass (shifts cleaner that way). I've been doing this for quite a while with no problems.

I hit the rev limiter on my bike damn near everytime I drive it!

11,000rpm shifting is fun!