m50b25 2.8 stroker kit - what gains?

[liam012]

Zionsville have a nice little stroker kit http://www.zionsvilleautosport.com/stor ... dyStyle=4D
what sort of power/torque would you be getting out of that is fitted to a normal m50b25 engine?

[DanThe]

Thats cheap!!

Same type of thing im doing with a 2.5 NV M50 at the mo, but with a few extras

That kit would be good for 230 hp and similar torque I would have thought.

Bearings and rings will cost you more than that kit though, then there is head gasket, stretch bolts etc to take into consideration

[liam012]

unfortunately i have just found out that 30 people are waiting on the kit.....
what have you done dan?
taken pistons and crank from an m52 and put in a m50b25?

i like the sound of a 24v 2.8 conversion esp yeilding 230/230 power and torque!

[liam012]

so basicly with a non vanos m50b25 aall you need is te 2.8 crank and pistons and of youo go?

2.8l Stroker
---------------
for M50B25 engine
- crank M52B28
- rods M20B20/23 (130 mm)
- pistons M50B25 (non-Vanos)

or
- crank, from M52B28
- rods 135 mm
- pistons M52B28

or
- crank, from M52B28
- rods 135 mm
-pistons M50B25TU , pistons must be modified to decrease compression

rod lengths:
M50B25TU: 140 mm
M50B25: 135 mm (non VANOS engine)
M52B25: 135 mm
M52B28: 135 mm
M54B30: 135 mm
M20B20: 130 mm
M20B23: 130 mm
M20B25: 135 mm
M20B27: 130 mm

[DanThe]

unfortunately i have just found out that 30 people are waiting on the kit.....

Not surprising with that price

what have you done dan?
taken pistons and crank from an m52

Yes and rods,

and put in a m50b25?

Getting there

i like the sound of a 24v 2.8 conversion esp yeilding 230/230 power and torque!

Im aiming for a tad more than that

[AndyTouring]

Find a Nikasil knackered 2.8 & rebuild using a 2.5 cast iron block.

[DanThe]

Not as easy as you would think, most problem Nikasil engines are now long gone

[ste]

You going for FI DanThe?

[AndyTouring]

Not as easy as you would think, most problem Nikasil engines are now long gone

Suppose so. Could just put the whole M52 in then.

I'm sure a 2.8 crank from BMW would be laughably expensive . . .

Liam: the main gains from using a 2.8 crank is extra low end torque. Forget high bhp headline figures, it's lots of torque at 2-4k rpm you need. That's what gives you the kick out of corners & the overtaking punch. That's why diesels are such a giggle.

Now who's going to be first to get a 335d twin turbo diesel into an E30?

[Ant]

FYI the M52B28 crank is £507 inc shells NEW.

13 in the warehouse last week

[liam012]

intriguiinuinguining erm interesting

so the question is

24v 2.8 m50v hybrid versus 12v 2.7 m20

would you notice the increase in torque? i have to say the 2.7 pulls very well i'd get all silly and goofy if i thought that the 24v 2.8 offered a whole lot more as that must just be great fun.

[DanThe]

You going for FI DanThe?

No, just up the comp slightly, ive also got a pair of Schrick cams to go in


Ant, thats cheap

I had £900 in my head for some reason

[beardymat]

speaking of m52 cranks, dont forget mine on sunday dan

[DanThe]

I wont forget Mat

Just need to get it in a box to stop it rolling around in the boot denting everything

Still got my phone No?

[AndyTouring]

FYI the M52B28 crank is £507 inc shells NEW.

13 in the warehouse last week

Ouch

so the question is 24v 2.8 m50v hybrid versus 12v 2.7 m20

would you notice the increase in torque? i have to say the 2.7 pulls very well i'd get all silly and goofy if i thought that the 24v 2.8 offered a whole lot more as that must just be great fun.

Ah, I thought you were comparing a 2.8 with a 2.5. In that case, I wouldn't have thought there would be much in it.

As far as the M50/M52 were concerned they were:

2.0 150bhp @ 5900rpm 140lb/ft @ 4700rpm 70lb/ft per litre 80mm X 66mm = 1991cc

2.5 192bhp @ 5900rpm 177lb/ft @ 4200rpm 70.8lb/ft per litre 84mm X 75mm = 2494cc

2.8 193bhp @ 5300rpm 206lb/ft @ 3950rpm 73.6lb/ft per litre 84mm X 84mm = 2793cc

As you can see, torque goes up in line with capacity. Long stroke engines are low speed luggers (relatively speaking) compared to short stroke engines which have a revvier nature. This explains why the pre '82 635 felt more urgent than the later 635 which had a slightly reduced bore & longer stroke. Compression ratios & cam timing come into as well of course.

A comparison of the bore & stroke shows why you have to cane the 2.0 to get it to move & the 2.8 feels so effortless.

Square or slightly long-stroke engines have the nicest power delivery for road use. Track use has different requirements. The short answer is "there's no replacement for displacement" & a good big 'un will always beat a good little 'un.

[Morat]

ooooh loverly torque.
I gotta say, torque is where its at - its the big midrange shove that zips you away in third that excites me far more than screaming along at 6k watching the speedo inch up 1mph at a time.

[jaistanley]

If I hadn't buggered my budget and bought an S50 I think I'd have gone on the lookout for an M50B25NV and fitted the M52B28 internals.. With a set of wild(ish) cams, megasquirt (no vanos to mess around with) and maybe some headwork I recon you'd have a right belter of an engine and easier to fit than this S50 BA**ARD!

Looking at the M52B28 bore and stroke, I cant see why you couldn't get it balanced, fit cams with a higher duration and drag the peak torque further up the rev range. It's a 'square' bore/stroke. Nice combination. Have a redline of 7500 say. You might need stiffer valve springs too I spose.

Do I remember hearing the M54B30 crank fits the M50 block? Aside from getting an American 3.0 or 3.2 crank that'd be a nice way to bigger displacement. Dunno what conrod/piston combo you need though. Forged pistons are probably sensible money in the states (everything seems to be).

Jai

[DanThe]

The Non Vanos head uses double valve springs as standard Jai, I doubt they would cause a problem