Rippin' the revs

[kevinheap]

I have a 95 M3 and generally I just take it up to about 5k before shifting but there is a wealth of power from 5k to 6k which I am tapping into more and more often. I like to see the machine live up to its potential.
My question is that if I continue to push it like this coming up just 500 rpm short of redline on a regular basis will this shorten the life of my car to any major extent. I also wonder if I should pay special attention to any particular components on the car if I drive it hard. I do have new coolant. The car have 140,000 miles and I just love this model vehicle. Thanks

[shadowpuck]

most of these cars, in my opinion, do not get driven hard enough on a regular basis.

that said - i don't beat up on my cars unnecessarily on the street. a few good pulls each time i drive is enough, at least in my time owning e36's and e46's.

if you aren't already, look into the BMW Club of America (BMW CCA) and join. then, contact mike miller and ask for his maintenance schedule. it's the best way to make a vehicle last. his contact info is in the CCA's official magazine - Roundel.

if the following hasn't been done already, it'll need to be:
- at 140k you will need to address the entire cooling system (BMW Coolant, hoses, waterpump, thermostat, t-stat housing, radiator, etc.)
- suspension bushings are common wear items on all BMWs and should be addressed.
- regular oil changes with a quality oil and OE or OEM (so, BMW, Mahle, etc.) filters.
- regular brake fluid flushes (every 2 years) with BMW fluid.
- regular transmission and differential fluid changes with quality fluids.

if you really want the vehicle to live up to its potential, make sure it is completely safe and leak free then take it a BMW club driving school. the local chapter in Colorado puts on some great events with some awesome instructors.

[bmwdirtracer]

+1 to every word shadowpuck has shared. I'd mention that the torque curve of the U.S. S50 falls away fairly rapidly after 5500 rpm, so actual acceleration will diminish. My M5 revs to 7200, but I rarely use the top 700 revs, because really, the next gear delivers more acceleration.

By all means, use your car's performance....and certainly, join BMWCCA, and participate in some HPDE's.....that's where you'll truly be able to become familiar with all your car has to offer.

Always buy the best tires; it's your car's only connection with the earth.

[MIKYZZ4]

Gradual acceleration to redline or whatever you desire can extend engine life,
compared to regularly driven attempts at sudden acceleration to red line,
which will decrease engine life.
Smooth and steady acceleration and deceleration can extend vehicle lifespan.

[323i E30]

Obvious, but should be mentioned: don’t get to the high revs until your engine has been at proper operating temperature for a couple of minutes.

[ross1]

Gradual acceleration to redline or whatever you desire can extending engine life,
compared to regularly driven attempts at sudden acceleration to red line,
which will decrease engine life.
Smooth and steady acceleration and deceleration can extend vehicle lifespan.

NO

The BMW redline is ~conservative and you'll not blow it up by touching it. It's not over stressed at redline, just working hard. Revving beyond that you are approaching intolerable stress levels and just making noise anyway.
In short revs do kill.
An interesting thing I learned working with race cars was the recommended time between overhaul on a friend's Cosworth DFV engine. Shift at 10,500 20 hrs TBO, shift at 11,000 10 hrs TBO,,,,,,,,,, 'nuff said

[jclausen]

The red line is set by the manufacturer,, I don't know why one would think it is conservative. the harder you drive it the harder it is on everything in the engine, driveline suspension brakes. So if you want to wear your car our sooner then drive it hard. Just because it can do it doesn't mean it has to be driven that way all the time

[ross1]

It's conservative because they are expected to warranty the engine and know some will flirt with it, there are plenty of revs(but little power) left before things get ugly, that's why the rev limiter. Not saying it's good for it.

[MIKYZZ4]

Gradual acceleration to redline or whatever you desire can extend engine life,
compared to regularly driven attempts at sudden acceleration to red line,
which will decrease engine life.
Smooth and steady acceleration and deceleration can extend vehicle lifespan.

The red line is set by the manufacturer,, I don't know why one would think it is conservative. the harder you drive it the harder it is on everything in the engine, driveline suspension brakes. So if you want to wear your car our sooner then drive it hard. Just because it can do it doesn't mean it has to be driven that way all the time

I agree, and still stand by my quote.
Gradual and steady acceleration is much more life extending,
than stomping on the pedal for your desired results.

[bmwdirtracer]

Really, when you're flat out on the throttle, the object is acceleration, is it not? If the object is acceleration, then revving most engines to near redline is counterproductive. Sure, it's easy to THINK it's faster, but science is science. (Yes, there is the wasted time spent gearchanging. but if you're going to use the same number of gears on a given straightaway, it's faster to be in the gear which is closest to the torque peak.)

This isn't a graph for a U.S. S50, (It's an M52, I think) but it won't be far off, in terms of torque curves. If the torque is greatest between, say 4000 revs and 5500 rpms, and the engine experiences more stress as it nears redline, isn't it wise to just go ahead and shift at, oh, 500 rpm less than redline?



https://screenshots.firefox.com/UMjM...www.google.com

[jclausen]

The rev limiter is a warning system, if you miss a shift, the rev limiter will not protect your engine against bent valves. It seems silly to take a great running car and run it to redline on a regular basis, What is exactly achieved by this.

[ross1]

The rev limiter is a warning system, if you miss a shift, the rev limiter will not protect your engine against bent valves. It seems silly to take a great running car and run it to redline on a regular basis, What is exactly achieved by this.

I don't see where anyone has proposed this. What am I missing?
The rev limiter is intended to and does protect the engine against severe over revs(unless forced to rev as by a clumsy downshift), it isn't a warning, the redline on the tach is the warning.
I think we are all in agreement the too high revs are NG.
Bent valves can occur if the valves float, ostensibly the rev limit is set below that point.

[Breeze1]

I don't think my opinion is going to be a popular one based on what I have read, but I would say that you NEED to rev the sh*t out of it on a regular basis.

Depending on the type of enging you have (rev happy or not...) that "regular basis" will differ but still, it needs to stretch its legs to its full potential to keep internal components, joints, etc. running smooth. Think of a sprinter: if he/she doesn't run as fast as possible on a regular basis his/her peak performance will decrease.

But that comes with rules: great maintenance, never on a cold engine (meaning not only water temp but oil temp as well, which takes at least 10-15min of smooth driving), always give it time to cool off (smooth driving again...) before you turn it off...and since you haven't gone past 5000rpm often you should do that gradually (again: an athlete who hasn't exercised hard for a while would get hurt if he suddenly ran like a maniac...)

The only engine I blew up in 20 years (M52TUB25) was an engine driven for 10 years by a woman who probably never got it past 4000rpm and maintained it like sh*t.
When I got the car there was literally sludge in the engine and it was barely faster than my former e36 116hp 318i, if faster at all.

After many engine flushes, oil changes and gradual increase in how much I demanded of it, it got in a pretty decent shape and I can say that it was waaaay faster at the end than when I got it, on par with 170hp new cars and that was before I modded it with an M54 intake manifold and a CAI, which made it around 180-185 from my "gut feeling" of how it drove. In the end it was not only red lining but rev "limiting" easily whereas it choked at 5000rpm when I got it.

Eventually it blew up because I guess it kinda got "too powerful" for its tired internals, as I would discover when I pulled it out that it had already been opened (missing a nut ), probably due to overheating. The ticking noise I could never totally get rid of and thought was only a pushrods issue ended up being a piston ticking noise.

It also suffered a spark plug thread destruction when, after a hard mountain driving on low oil (there was a 4cyl dipstick in the engine which made me think it had 6l when in fact it only had 4. The road's steep slopes did the rest...

The damn piston spent 4 years ticking and gave its best up to the last trip, which it managed like a champ (I can still hear it revving ).

So I would say just take good care of it but make it work...

[bmwdirtracer]

"Tis a thin line, between genius and madness."

We all spend plenty of time on the dark side of the longevity equation. But if you ask any race engine builder how long his engine will last, the answer will always hinge very strongly on what maximum revs you use regularly. Avoiding constantly visiting the highest 500 revs might double your engine life.....and keep you accelerating at peak torque, too.

[Breeze1]

Doesn't look good that

Sure it's not something that should be done on a constant basis. But a few high revvings during say, a 20 miles drive should not be a problem IMO, on the contrary. I also think that race engines, given their very high revving nature, might be more prone to that "last 500 revs" (adding 500rpm to 9000 or 10000...) rule than customers cars, but that's just my two cents...

"Tis a thin line, between genius and madness."

We all spend plenty of time on the dark side of the longevity equation. But if you ask any race engine builder how long his engine will last, the answer will always hinge very strongly on what maximum revs you use regularly. Avoiding constantly visiting the highest 500 revs might double your engine life.....and keep you accelerating at peak torque, too.

[ross1]

"Tis a thin line, between genius and madness."

We all spend plenty of time on the dark side of the longevity equation. But if you ask any race engine builder how long his engine will last, the answer will always hinge very strongly on what maximum revs you use regularly. Avoiding constantly visiting the highest 500 revs might double your engine life.....and keep you accelerating at peak torque, too.

Exactly. Anyone who understands the forces involved knows this.
If someone manages to beat the crap out of an engine for xxx miles before it blows up you can rest assured it would have gone longer if not thrashed.

[bmwdirtracer]

That's my M5's last engine, pictured, right after it blew three holes in the block on the front straight at VIR.....at redline, by the way. Still, the replacement engine gets the car to over 100, every day. Today it happened to be 130, last week it was 145.

My candle burns at both ends,
It shall not last the night.
But ah, my foes, and oh, my friends,
It gives a lovely light.

-Edna St. Vincent Millay

[Breeze1]

+1

[bmwdirtracer]

"Play it once, Sam, for old time's sake." (don't play that song again)

You don't really strike me as being in the Maghreb, Breeze. (There wouldn't seem to be enough spare engines there.)

[jclausen]

The rev limiter cant react quick enough if you miss a shift or some thing like that, rev limiters are dealing with electronic counter measures altering fuel delivery or timing, it has nothing to do with pistons or valves that have sped past there design limits. You can't slow the mass quick enough to save the engine

[Breeze1]

"Play it once, Sam, for old time's sake." (don't play that song again)

You don't really strike me as being in the Maghreb, Breeze. (There wouldn't seem to be enough spare engines there.)

I'm more specifically in Morocco, Casablanca, and the Rick's café is alive and well
And believe me there are plenty of spare engines! The M parts (engines and other parts) are scarce though...

[ross1]

The rev limiter cant react quick enough if you miss a shift or some thing like that, rev limiters are dealing with electronic counter measures altering fuel delivery or timing, it has nothing to do with pistons or valves that have sped past there design limits. You can't slow the mass quick enough to save the engine

please explain to me then what continues to accelerate the mass without any combustion.

[Breeze1]

please explain to me then what continues to accelerate the mass without any combustion.

I am incapable of giving a detailed mechanical explanation of that phenomenon but broadly speaking I would say that when you downshift, instead of the engine spinning the driveshaft (through the gearbox) thanks to combustion, things go "backwards": the driveshaft makes the engine's crankshaft spin. Depending on what gear you're in it does that at different speeds.

That's why rev limiters only work when you're accelerating (using the combustion process, which can be stopped by the ECU through fuel injection cut off) and not when you're downshifting: the former can be electronically controlled whereas the latter is 100% mechanical process which the ECU has no control over.

The only way you can "save the day" if you miss-shift is by depressing the clutch, to disengage the gearbox from the engine.

[ross1]

I am incapable of giving a detailed mechanical explanation of that phenomenon but broadly speaking I would say that when you downshift, instead of the engine spinning the driveshaft (through the gearbox) thanks to combustion, things go "backwards": the driveshaft makes the engine's crankshaft spin. Depending on what gear you're in it does that at different speeds.

That's why rev limiters only work when you're accelerating (using the combustion process, which can be stopped by the ECU through fuel injection cut off) and not when you're downshifting: the former can be electronically controlled whereas the latter is 100% mechanical process which the ECU has no control over.

The only way you can "save the day" if you miss-shift is by depressing the clutch, to disengage the gearbox from the engine.

I understand how a too early downshift can do this and touched on it in a previous post. I was responding to the contention that a missed (up)shift could somehow exceed the rev limiter.

[Breeze1]

I understand how a too early downshift can do this and touched on it in a previous post. I was responding to the contention that a missed (up)shift could somehow exceed the rev limiter.

I thought it was about a miss-down-shift... Impossible on upshifts since that's why the rev limiter is there in the first place, and it has nothing to do with shifting. If you fail to engage the following gear the RPM will reach rev-limiter and fuel will be cut-off, exactly as it would in neutral. So +1 on your combustion comment.