To use M52 rods or not to use M52 rods, that is the question

Post Wed Feb 06, 2008 2:15 pm

What do we reckon.

I've got a forged crank and forged pistons, do we think I should use rods from someone like Arrow or Carillo (SP?) or stick with the M52 rods and ARP bolts?

The BMW rods are of course forged themselves, but I'm still undecided!

Cheers!

Alex

Post Wed Feb 06, 2008 2:22 pm

If they fit and you have them why not?

can you think of any 'real' scientific tuning reason you shouldn't reuse them?

BTW whats the difference between thos and the M20B20 ones?

Post Wed Feb 06, 2008 4:43 pm

without putting thought into the reply etc, but what would the advantage be of the arrow etc rods then if the bmw ones are forged? get them destressed, balanced n away?

Post Wed Feb 13, 2008 2:10 pm

Only reason I can think of is strength and weight.

Think the decision's been made for me now though as I've just about secured a good deal on a set of Pauter rods

Post Wed Feb 13, 2008 2:12 pm

Turbo-Brown wrote:Only reason I can think of is strength and weight.

Think the decision's been made for me now though as I've just about secured a good deal on a set of Pauter rods

There's quite a difference in weight between the BMW and the Pauters! 640g for a standard M20B25 rod, 500g for the Pauter.

Post Wed Feb 13, 2008 2:16 pm

If you do go with the Pauter rods, I might be interested in your m52 rods! PM me.

Post Wed Feb 13, 2008 2:19 pm

Thought you used M20b20 rods for the 2.8?

Post Wed Feb 13, 2008 3:12 pm

Turbo-Brown wrote: There's quite a difference in weight between the BMW and the Pauters! 640g for a standard M20B25 rod, 500g for the Pauter.

What's the weight of the M52 rods though? I bet it's nearer 500g than 640g.

Post Wed Feb 13, 2008 5:19 pm

Think the M52 rods are about 570g or so in fairness.

Post Thu Feb 14, 2008 1:22 pm

I vote have the M52 ones de-stressed and burnished. Shouldn't cost too much and they'll blatantly be strong enough, especially as you are using lighter, forged pistons.

Good to be able to have the choice though eh? S'alright for some..

Jai

Post Fri Feb 15, 2008 8:49 am

Well, the deal's done now as I've paid the guy

Apparently the M52 ones are a MASSIVE 75g heavier than the Pauters :lol:

Every little helps I guess.

Post Fri Feb 15, 2008 12:18 pm

Ooooh, you flash bastard... lol

Post Fri Feb 15, 2008 1:49 pm

And I've bought the M52 ones now too!

Tell me more about having them de-stressed and burnished please?!?

Post Fri Feb 15, 2008 6:36 pm

Well it's a matter of removing all flashing, lumps bumps etc from the face of the casting (or in this case forging) in order to prevent crack propogation from surface imperfections. Then burnishing is where beads of hardened metal are blasted at the surface to work harden it, again helping to prevent cracks propogating from the surface.

Metals are funny things. Their strength is hugely affected by the surface finish as cracks generally start at the outside and move in.

Don't know of anywhere secifically that does it but I remember there being a place in Coventry somewhere off Gulson road (I think).

HTH

Jai

Post Fri Feb 15, 2008 7:07 pm

Perhaps type "shot peening" into google and see if anything comes up.

Post Sat Feb 16, 2008 3:13 am

DOH.. Been a while since I did materials science, excsuse the engineering fauxpas lads...

Post Sat Feb 16, 2008 2:50 pm

are M25 2.8 rods 135mm ala 2.5 M20 ones?

Anyone know if M54 rods are lighter still as they came in 2494cc?!

Post Sat Feb 16, 2008 9:19 pm

They are indeed 135 mm Simon

Post Sat Feb 16, 2008 10:12 pm

Hmm, according to the metric mechanic site the rod weights are as follows:

M20B25 (87-91) 640g
M20B25 (91-92) 600g
M52B28 575g
S50 540g

I'm pretty sure that all of the rods are interchangable as they've all got the same BE bore, LE bore, BE width and centre to centre length. Don't quote me on that though!

Post Sun Feb 17, 2008 2:53 am

Are the S50B30 and the S50B32 rods the same then?

Post Sun Feb 17, 2008 11:05 am

M54 M54 m54 M54 m54..........................

Post Sun Feb 17, 2008 1:00 pm

Simon13 wrote:M54 M54 m54 M54 m54..........................

huh?

Post Sun Feb 17, 2008 3:20 pm

I think he wants to know how heavy they are..

Post Sun Feb 17, 2008 5:03 pm

DanThe wrote:I think he wants to know how heavey they are..

and the size.

Post Sun Feb 17, 2008 7:01 pm

jaistanley wrote:Are the S50B30 and the S50B32 rods the same then?

Good question, no idea! :lol:

Post Mon Feb 18, 2008 3:13 pm

I doubt they are the bore is only marginally bigger isn't it? The increased stroke being where the majority of the capacity increase is from.

Jai

Post Mon Feb 18, 2008 6:27 pm

bmw made a 2.5 M54 and i doubt they would change the cc from original recipe 84mm bore 75mm stroke. Or i hope they don't and i hope they are even lighter rods!

Post Mon Feb 18, 2008 6:38 pm

Simon13 wrote:bmw made a 2.5 M54 and i doubt they would change the cc from original recipe 84mm bore 75mm stroke. Or i hope they don't and i hope they are even lighter rods!

Can't find info on the 2.5, but heres some intersting info on the 3L M54

http://www.usautoparts.net/bmw/engines/m54.htm

135mm rods though!

Post Mon Feb 18, 2008 9:49 pm

You think those are good? Find out some info on the latest 6 pot, the N52

Post Mon Feb 18, 2008 9:50 pm

If I could afford custom rods then I would definatly go for those. As I can't I'm settling for the M52 rods.

Dan did the crank get collected today?

Post Mon Feb 18, 2008 9:54 pm

Its booked for collection tomorow, will let you know what time it happens

Post Mon Feb 18, 2008 9:54 pm

Cheers dude.

Post Wed Feb 20, 2008 11:27 pm

M54 rods are powdered steel, not forged. They also have the fractured big end caps.

All M52 rods are 135mm, even the 2 litre.

Post Thu Feb 21, 2008 9:04 am

yeah the above's right, although I've also seen m54 engines with exactly the same rods as m52 - forged, and not cracked big end caps. Not sure what dictates it :S

Post Sat Feb 23, 2008 7:25 pm

are these nice and light and 135mm tim?!