m54b30 crank question

[Kuutiwo]

Sorry if wrong place to post but seems people have good info on this forum. How much in revs can b30 crank handle with something like ati damper ? After im done with my e34 i will be buying engine for my e28. I was thinking of doing m50 block + b30 crank and some nice pistons+rods for na build and some other stuff but atm interested to crank. But im curious about what are the limits of b30 crank ? Am i good with b30 crank or should i look into b28 crank instead ? Block propably would be bored to 86~mm. And i think rev range between 7500-8500 depending what i will throw at it when (if 😅) i do start on the build.


Edit: i should add that i havent built engine in my life, i do have information to do so, but this would be at the same time learning project, not aiming for the moon as the car will be driven on street so the finished product might end up as something completely different. I would go turbo otherwise but i have max 135~kw if i would do turbo, would need to add abs after that and i simply love na cars. If i would make the build in short it would propably be either b28/b30 crank, 86mm bore, some headwork, cams, itb setup and ofcourse some custom exhaust stuff and so on. I would be doing everything i just can do, either by learning on the fly or googling and adding up that information. Oil pickup is something i havent addressed yet for example, but like said i still have to finish my e34 thingy so i have time to collect information here and there. I have the build pretty much written in my head minus few things here and there. I might also go for lower rpm level than 8k so dont think that as a target, its more of would be fun to do. Aim would be for 250whp which should be do able with what i have planned.


Just noticed there was 24v section.........

[E30-325iS]

Ex

[2mAn]

Just noticed there was 24v section.........

and its there now

[TobyB]

The B30 crank's got a serious history of self- destructing just below 7k.
I don't know how much of that's due to the adequacy of the
stock damper and the harmonics tearing the oil pump off,
and how much is the crank itself.

Your target is tricky- 250 hp can be found (just) under 6800 rpm.
And the 3l crank DOES help the torques.

But a 2.8 liter crank, spun faster, should get you over the 250 hump quite comfortably.
But with potentially less torque.

It's your call- personally, I wouldn't spin the 3L that fast, because I hate
big bangs. But the sound of a 6 at 7500 is sooooo sweeet.

1 vote for a 2.8 liter crank, here.

t
not very scientific

[digger]

it comes down to what the purpose of the engine is. are you going to use it for racing where it spends a lot of time at high rpm ?
or for the street with occasional burst (no pun intended)?

the former a smaller stroke is potentially better
the latter the larger stroke is certainly better

250whp should be easy on 3L sub 7k

ATI is not a 100% cure for racing a 3L iirc the oil pump still shakes itself but could just be a matter of adding a tensioner

or upgrade to a timing belt engine that absorbs all this nonsense

[Northern]

+1 for adding a tensioner, should do a lot for damping the vibration transmitted to the pump.
There's a cheap VAG part that can be installed on the earlier 24v cars, as well as the early M50NV/S54 style setup.
Not sure which is "better", but you may also run into fitment issues with the larger/different M54 pump or aluminum block

[ba114]

I really haven't read about THAT many unique issues with the oil pump nut undoing or shearing off, mostly the same couple of stories propagated across the internet by people who have never had it happen to them personally.

with that said, there's nothing wrong with being cautious, which is why I have a modified (6 bolt sprocket + welded and shaved) m54 oil pump fitted to my m50b32 as well as the VAG tensioner.
Brand new crank and pump sprockets were used in the build.

[TobyB]

While it's never happened to me personally, I did inspect the carnage
that dropped out of the bottom of a Spec46 car last spring, going into 5a in Seattle-
the rotor was out of the pump, the outer gearotor was in chunks,
and the front shaft threads had no evidence of a sprocket or nut
anywhere in the zip code.
I suspect that one unscrewed, and then blewed. Up. Way up.

t

[moatilliatta]

I really haven't read about THAT many unique issues with the oil pump nut undoing or shearing off, mostly the same couple of stories propagated across the internet by people who have never had it happen to them personally.

with that said, there's nothing wrong with being cautious, which is why I have a modified (6 bolt sprocket + welded and shaved) m54 oil pump fitted to my m50b32 as well as the VAG tensioner.
Brand new crank and pump sprockets were used in the build.

More info on the VAG tensioner?

I have an S54 pump / pan set up on my E30. Motors coming apart this winter.

I think S50 crank and 140mm rods is the secrete sauce if your going to get curious in the RPM.

[Northern]

More info on the VAG tensioner?

https://www.fcpeuro.com/products/aud...-ina-06a115130

INA 06A115130
also has an oem version for a bit more, and I believe there are some other variants in different colours.

Installed on an M52B28 for my clapped out 4dr with a new pump chain:


$6 vs ~$40 for the S54 setup.

There is allegedly a motorsport pump chain for the m50/52 pumps that is slightly tighter somehow. Not sure if the same exists for the M54.

[Northern]

You just sort of line it all up and drill where it seems to fit best. Placement is somewhat limited by the rib structure on the inside of the block and the timing cover.

[TobyB]

I am thinkin' that is good for stoppin' the flappin' but maybe not so good for the pulsin' that comes from the crank,

as any real reversion on the chain will overcome the spring.

That bloviated, it's a shit- ton better than stock...

t

[Kuutiwo]

By the sounds, i might go with b28 crank if i do step on this build ever(dreams are nice 😋) as if my budget keeps up, i might make the engine turn higher than 7500, not for racing use but i guess its more of dream car thing. Propably will get damper anyway, time will tell. Sorry for late answer, kinda forgot this thread haha. If i dont find this via googling around, is there much weight dofference between the 2 cranks ?