how long will an m20......

[HairyScreech]

how long will an m20 happily bounce off the limiter for before it shits the bed?

[fowler]

who a dodgey question not that long

[Jesus325iTouring]

Love questions like this

[Turbo-Brown]

How long's a piece of string?!

How old is this mythical engine for a start? How well cared for? How hard's it been driven up to the point you start zinging the limiter?

[chrisr29]

Try it and see!

[AdamAnt]

For EVER

[ChrisBarns]

I don't know about M20s but when my dad was at university doing engineering in the 60s they used to strap engines to dynos, throttles wide open, set a load that stopped them from quite over revving and leave them running for up to 24 hours, manifolds glowing bright red. They'd then dismantle the engine and look for wear. Apparantly very few actually failed. Amazing really.

I'd guess the most likely fail would be a big end as the oil got hot and pressure dropped.

When I was young I ran a Nissan flat out in third (6500) for about 10 miles, trying to see if maximum speed was higher in 3rd or 4th (idiot!). A valve burned out. On other engines over revving has lead to a snapped rocker shaft and I also once broke a rocker once but I can't remeber how.

What do people think would happen to the M20?

[AdamAnt]

any volunteers to do a you tube educational vid

[Ziggy]

any volunteers to do a you tube educational vid

Well it'd have to be an m20b20 - My b25 will be spare shortly, but it still has some value!

[green-blood]

How long's a piece of string?!

the distance between its two ends.......

[jbh]

any volunteers to do a you tube educational vid

think i know where theres a 320 i could get cheap would just need to find somwhere to have some fun with it

[pnd]

don't buy a used e30 from this man!

[march109]

don't buy a used e30 from this man!

from what man? isn't this a thread about m20's on the limit.

[pnd]

don't buy a used e30 from this man!

from what man? isn't this a thread about m20's on the limit.

the guy who atarted the thread.

[maxfield]

Try it and see. I'd say a couple of hours. Who knows?

Assuming it had plenty of miles and an OK service history.

[JimmyC]

My first engine lasted one bounce up druids before dying :lol

There was a guy that used to race in PBMW (his car still does) that had a brand new engine, he lived on the limiter, you'd hear him ddddddddddddd'ing all the time.

[d6dph]

I'd say a b20 would last longer than a b25, my guess is a b25 head would poop itself within 15 minutes.

[chrisr29]

As the rev limiter's there to protect the engine then surely it would do it indefinetly. Would be more interesting to disable it and then give it a go....give the engine more and more revs untill it blew itself to peices!

[march109]

As the rev limiter's there to protect the engine then surely it would do it indefinetly. Would be more interesting to disable it and then give it a go....give the engine more and more revs untill it blew itself to peices!

not my idea of fun but each to there own. agree with the point about the limiter though, I think the manufacturer would have set it at a level where the engine would be able to operate for at least a nominal period of time before it died. I would assume these engines were also bench tested when new.

I have heard of engines being taken apat and only just looking run in, I would say the limit on engines this age would now be how long the oil would remain effective for since it would get so hot it would find a way past persihed seals and old gaskets pretty quickley, new I would expect the engine could easily run to 24 hours. At this point the engine would then need changing before running again.

Oil cooler and then engine cooling efficiency would also play a factor. If the rad was crud then you cold expect failure pretty quick.

[d6dph]

Depends on how the limiter works, if it cuts the fuel surely it would be like it was pinking heavily?

[dannyboy759]

Ive had my 325 over two years and the limter on mine is set just over 7000rpm and the car gets some right stick and touch wood its been fine.

[HairyScreech]

don't buy a used e30 from this man!

from what man? isn't this a thread about m20's on the limit.

the guy who atarted the thread.

if by me asking a completely open question about the m20 engine, in no way referring to my own e30 you assume that I intend to treat mine like shit then I find you view short sighted and quite frankly insulting. In fact id put money on mine being in better mechanical condition than most.

Now, in reference to the question it was a deliberately open question and was really in reference to a fairly new/good condition engine.

It was purely hypothetical question as I remember a fiesta that was run in a burn out solidly for 15 minutes before it dumped its coolant. Was just wondering as I know a few of the drifters on here and a few of the PBMW guys will have had theirs off the limiter for quite a long time.

As far as the way the limiter works, I'm not sure but id assume it would be a spark cut as that's a far safer method compared to making it run super lean, but I can always find out what it is on the motronic ecus as we use old nova motronics for test work at uni.

[HairyScreech]

in fact maybe i should have put this in pub talk as it was only a "here lads, how long would it take to pop one of these?"

[Turbo-Brown]

It's perfectly safe to cut the fuel as a means of limiting revs: no fuel, can't burn!

[d6dph]

Ahh ok

[Kos]

we talking about rep[airable damage or no repareable ??

i recon a rocker would go first.

[march109]

we talking about rep[airable damage or no repareable ??

i recon a rocker would go first.

Don't know, I just considered 'pop' engine no workee.

would be interesting to know, but guess its not really possible to prove since there are no new M20's, although BMW sell reconditioned M20's and you could have one rebuilt I suppose.

[Simon13]

Ive had my 325 over two years and the limter on mine is set just over 7000rpm and the car gets some right stick and touch wood its been fine.

M20's don't like 7000rpm without some internal mods

My old sport did a drift day and that was literally off the limiter all day and was fine. Stock limit though 6250rpm iirc Theres plenty of folk who drift their 325's off the limiter all the time and they are fine. Engine condition is the main baring on this one imo

A good engine will be fine, even a slightly tired one will take some sh!t