M42club.com - Home of the BMW E30/E36 318i/iS
DISCUSSION => Engine + Driveline => Topic started by: Oversteer on January 07, 2008, 04:14:40 AM
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hi!
I was just wondering what is the real limit of a standard M42 (E30 in my case), in terms of revs... It cuts around 6,5k but I believe it can take more, even in standard form, considering the forged crank and rods...
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dont... the hydrolifters will destroy your valves and even the head... above approx. 7000revs
above this revs the hydros will get filled with oil more then normal and it can be that the valves touches the pistons... the springs are also not strong enough
change to solid lifters and stronger springs then you can rev up to 8 or 9000
it can go well without changing anything, it CAN... but it is only a matter of time
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Many people over here in Ireland and England use chips from a very reputable company. It raises the rev limit to 7200 rpm and no failures have ever been reported.
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M42s can rev to 7000 rpms (heck, mine revs to 8000 rpms :) )
if you're super concerned about valve float, new beehive springs, M44 valves, and M50 lifters will do the trick.
The harmonic balancer issue of yonder also turned out to be a non-issue...
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yes i am a bit concerned!! because i saw fully destroyed heads after reving too high! but maybe it was about 8000revs. anyway... i am going to change my hydros with solid ones! i hate removing the head... for things like that
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M42s can rev to 7000 rpms (heck, mine revs to 8000 rpms :) )
if you're super concerned about valve float, new beehive springs, M44 valves, and M50 lifters will do the trick.
Why m44 valves? I thought ours were lighter.
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M44 is a teeny bit lighter, narrower stem etc.
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For short bursts, yes you can pass 7k. Above 7k, power drops dramatically anyhow so there is no point unless you change the cam, at which point everything changes.
Keeping it there for even short periods on a stock bottom end though is not recommended as it has been deemed not built to take it. Forget the lifters, the oiling system is not good enough for the lower end bearings at those revs.
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For short bursts, yes you can pass 7k. Above 7k, power drops dramatically anyhow so there is no point unless you change the cam, at which point everything changes.
Keeping it there for even short periods on a stock bottom end though is not recommended as it has been deemed not built to take it. Forget the lifters, the oiling system is not good enough for the lower end bearings at those revs.
HAHA, learned that the hard way, kept up w/ some e36's I shouldn't have, but my number 2 rod bearing was laying in the bottom of the case when I came out of a few corners.
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So, 7K is the limit, right?
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So, 7K is the limit, right?
Yes, and with stock cams useless to exceed.
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yep! except you want to turn the inside of the engine to the outside!
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i chipped my car a year and a half ago and it revs to seven thousand no problem and it hits it allot
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It's hard to give definite rev limit for stock lifters, springs or bottom end but 7000 sounds bit too low. There is always some safety margin built into the engine to allow for springs loosing their stiffness with age or occasional misshift.
Higher rev limit can be beneficial on stock engine even if it does not increase power. On my favourite track there is two places where I need to upshift for few seconds, then almost immediately downshift before entering a turn. That is 4 pretty useless gearshifts which could be avoided if I could stay on lower gear for few hundred revs longer :)
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Higher rev limit can be beneficial on stock engine even if it does not increase power. On my favourite track there is two places where I need to upshift for few seconds, then almost immediately downshift before entering a turn. That is 4 pretty useless gearshifts which could be avoided if I could stay on lower gear for few hundred revs longer :)
I know what you mean!;)
i chipped my car a year and a half ago and it revs to seven thousand no problem and it hits it allot
What chip are you using? I mean brand...
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That safety margin is why I said 7k is about the limit.
Many of the parts can hit 8k. That is not a question, the problem is that some may not. You may start pumping lifters, over-stressing bearings, and more. Any idea how good your oil system is? How about bearing condition? Timing chain?
If it were all brand spanking new, yeah, you could probably do 8k for short bursts, probably hit 7500 for a touch longer, but on a 130k+ mile engine... No.
May want to take a look at some of the bearings in the engine and read the Metric Mechanic engine manual. There are quite a few things in this motor to hold you back from ramping up the revs and keeping your engine living a healthy life.
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i hit 7,600 on an engine with 340,000 km's on the bottom end. the top end has reground cams and thats about it. i did it once by accident, but i've been driving ever since with no problems, i held it at 7,600 for good couple of seconds though.
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Well, it is quite pointless to argue about few hundred RPM's because this is no exact science and there are sooo many variables (age of valve springs, used oil etc).
Also, power targets and purposes of the engines vary from person to person. Somebody wants the car to last until a million miles and somebody needs to have 200 hp for one track season.
Only way to know for sure is to try it out... That is not very constructive practice because when you have found the limit it is too late. But since complete M42's are going for few hundred €'s so the loss of engine is hardly an end of the world anyways.
I think the guy here (ludiagsm?) who turbocharged his M42 revved it all the way up to 8500 with a stock valvetrain? Bottom end was obviously modified to take the stresses but I think that shows that atleast the hydro lifters, valve springs etc do not abrutly stop working bit past 7000. They might not last for another 10 years but when you can have spare engines for a cost of 5 tanks of fuel, hey, you might as well take some risks :)
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Say you're engine is built to rev to 8000 rpm, how would we make sure it has sufficient oil pressure? Febi, how is your oil pressure holding up at those revs?
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I've ordered a chip that has the rev limit changed to 7K, so I was wondering if it was safe to rev it there.
I think that 7K is enough for what I'm planning, cause I won't go radical about engine spec, keeping it standard with the chip and a KN panel filter. Plus, I'd need another rev counter!:D
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Well, it is quite pointless to argue about few hundred RPM's because this is no exact science and there are sooo many variables (age of valve springs, used oil etc).
Also, power targets and purposes of the engines vary from person to person. Somebody wants the car to last until a million miles and somebody needs to have 200 hp for one track season.
Only way to know for sure is to try it out... That is not very constructive practice because when you have found the limit it is too late. But since complete M42's are going for few hundred €'s so the loss of engine is hardly an end of the world anyways.
I think the guy here (ludiagsm?) who turbocharged his M42 revved it all the way up to 8500 with a stock valvetrain? Bottom end was obviously modified to take the stresses but I think that shows that atleast the hydro lifters, valve springs etc do not abrutly stop working bit past 7000. They might not last for another 10 years but when you can have spare engines for a cost of 5 tanks of fuel, hey, you might as well take some risks :)
Exactly.
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i'm willing to bet an M42/44 is well capable of 11K.
dry sump, solid lifters, lightweight valvetrain components, heavy springs, light flywheel, edged crank, ITBs, SA EMS, larger injectors, serious internal balancing, high duration cams, high comp pistons, 4-1 manifold, ect, ect.. should turn out rougly 300 to the flywheel.
how long would it last? 10K miles maybe. and it wouldn't idle. if you bought a few longblocks from the JY, you'd be able to swap parts over to new motors. would it be worth it? i doubt it. why bother making 300hp at a super high rpm, when you could make 300hp at 4-5Krpm with forced induction and have the motor last 100K miles. the only way i'd build a high strung M42 is if that's what was required by a sanctioning body of a racing organization.
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....dry sump, solid lifters, lightweight valvetrain components, heavy springs, light flywheel, edged crank, ITBs, SA EMS, larger injectors, serious internal balancing, high duration cams, high comp pistons, 4-1 manifold, ect, ect.. should turn out rougly 300 to the flywheel.
yes, do that and then you have a s42 engine! only some "small" changes to a m42b18 engine!! ;-)
!after a telephone with my racecarbuilder! set your rev limit for an m42b18 with stock hydros etc. to 7000rpms just to stay on the save site! think on your tiny oilpump! :-)