M50B25 Turbocharge Build Advice

[shiftlock]

Hey,

Not posted for a long time on here so hello from cold and rainy England

I bought a spare S50B30(euro) engine to turbocharge however I have been put off by how much spares for the engine now cost, so decided to buy a very much cheaper engine to turbocharge, the M50B25 (Non-Vanos).

I have already bought the turbo for the s50b30(euro) which I intend to use on the M50B25, The Borg Warner EFR 8374 0.93 A/R IWG on twin scroll T4 flange.

My power goals are as much as i can get with high octane Petrol station fuel, Shell Optimax 98RON.

Ive done a fair bit of reserch already and the issue is most people buld a standard internals with just a set of pistons and they are done, so want to ask questions to do with getting the most out of the engine.

I intend to replace the pistons and rods for good quality fordged, I was going to stick to the 2.5litre however theere is allot of crankshafts people use, does someone have a list and what stroke and rod is required?

I have spare s50b30euro crankshafts here, which are very simular to m54b30 crankshaft but they are not the same like the internet tells you etc.

Another thing i notice is the lower static CR people run, 8.5:1 pistons and then 3.5mm headgaskets, they dont seem to take into account the thickness of the headgasket so allot of these engines are really low CR, my aim is to finish with 9:1 CR.

I have 3.2 evo s50b32euro sumps and oil pumps in stock so i will bang one of those on for now, dry sump later.

On the s50b30euro turbo builds we fire ring the blocks, is it required on the m50b25 motor?.


What is the limit of the cylinder head? I will fabricate a equal flow plenum with singe throttle plate.

As for ecu it will be run on m800 motec with everything so i can control the engine parameters well.

What is the ideal spec for what i am doing and any advice?

Oh and max rpm of these engine? 7500rpm?

[E36 HateR]

You're on the right track, turbo selection is perfect, your best bet would be to use an m54b30 crank, same as our us 3.2L cranks, and a set of forged 135mm rods as well as forged pistons for the compression and bore you want.

With that crank I wouldnt go above 7300rpm, but I know some guys on that side of the pond rev these engines very high.

Head isn't really a big issue on these engines as they flow well, best cams so far have been shrick stage 1 cams as they spool better and make more power up top vs our US m3 camshafts.

From what I have read the euro engines crankshaft is not interchangeable with the m50 engines.

[mr10ger]

max rpm for the stock M50B25 NV is 7200. some say 7300 works as well, but i wouldnt risk it. with other valve srpings you can go way higher, up to 8000 or maybe more (with lighter valvetrain).

[shiftlock]

I'm really on the fence regarding this project, I've been sitting down and really working the cost difference out between the S50B30(EURO) and the M50B25, Reason I say this is because basically if you take the cost of the engine you start with, all the other costs are the same, Pistons, rods, bearings, fittings, ECU, Loom, Turbo, Manifold, etc etc.

So the M50B25 cost me £500 vs the S50B30 that owes me £3000, however the S50B30 was a complete engine conversion that was fully rebuilt, so it already had £6k spent on it with new chain guides, new 3.2 oil pump twin pick up etc.

As I would need to get Oil filter housing off M3 engine, 3.2 sump, and a host of other parts, I mean just the oil pump, sump and filter housing is well over £1k in parts, so would make the M50 more like a £1500 engine to start with (if you had same spec parts hanging off the side)

The the differences are the m3 S50B30Euro can rev much much higher, has throttle bodies out of the factory, and Vanos that works well.

I get the feeling if you where to smash a headgaket on the M50 and maybe a set of pistons and hang a Holset HX35/40 off the side, job done nice cheap project and great fun, but if your going to be spending best part of £8-10k building the project (if not more) seems logical to start with the right engine in the first place?

Over your side of the pond, I guess the main reason M50's are used is lower compression and less hassle of the Vanos, and the S50B30euro engine doesn't exist? maybe only as import so must be expensive there, same as an LS3 or something here is crazy moneys, so just wondering if I'm following what others do over there when there is better option over here if that makes sense.

Really need to decide what I want to do, the mapper said easy 700bhp with the S50 lol Perfect daily

Not decided either way yet, seems the 2.8 crank option is the better option as its nearly equal bore to stroke.

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What would you do?

[mr10ger]

as youre using a EFR charger, i think this wont be a build on a budget. so go for the s50. rods and Pistons may be a bit more expensive, as well as everything else, but you Need that parts on the M50 anyway. and just think about driveability if you really want to drive it daily. i dont think 700 hp out of a 2.5l or even a 2.8l low revving engine are somewhat nice to drive, a high revving 3l may be much smoother. but what you Need is a pretty good tuner to stay with dual vanos (wait, does de 3l even have dual vanos?) and use electronic boost control, so you could get a really nice torque curve. so 700hp @ 7800 rpm with Turbo out of 3l? could be streetable
btw i dont think youll be blowing anything with this power Output, so dont care about the costs of the spare parts.
you could use some 9,5:1 Pistons, im not sure, if ist JE or Wiseco. with a O-ringed block and oem/elring 2.05mm headgasket you should stay somewhere around 9.3 or 9.4.

[shiftlock]

as youre using a EFR charger, i think this wont be a build on a budget. so go for the s50. rods and Pistons may be a bit more expensive, as well as everything else, but you Need that parts on the M50 anyway. and just think about driveability if you really want to drive it daily. i dont think 700 hp out of a 2.5l or even a 2.8l low revving engine are somewhat nice to drive, a high revving 3l may be much smoother. but what you Need is a pretty good tuner to stay with dual vanos (wait, does de 3l even have dual vanos?) and use electronic boost control, so you could get a really nice torque curve. so 700hp @ 7800 rpm with Turbo out of 3l? could be streetable
btw i dont think youll be blowing anything with this power Output, so dont care about the costs of the spare parts.
you could use some 9,5:1 Pistons, im not sure, if ist JE or Wiseco. with a O-ringed block and oem/elring 2.05mm headgasket you should stay somewhere around 9.3 or 9.4.

Yeah this is kinda my train of thought now, if i was aiming for a budget 400bhp then M50 is a great bace, but if I want some numbers and drivability, and Lets be honest by the time I've spent out on a proper ECU it costs the same to tune, luckily I have great contacts for mapping.

The early 3.0ltr S50B30 is single Vanos, the later (Evolution aka EVO) is the 3.2ltr S50B32 with dual vanos, both constantly variable vs that of the M52 which I think is either on or off. The 3.2 has a much more longer stroke and prone to dropping rods, the 3.0ltr is same motor that came in the GT etc. I have spares because I have a Avus blue M3 with euro 3.0ltr.

The biggest bonus is Throttle bodies per cylinder, so you can basically run an open style plenum, saving paying out for a big boy throttle plate. the S50 also has ceramic spacers between the head and the throttle bodies so again win win.

This is my very clean (mostly refurbished) Avus Blue M3 3.0 95' (any excuse to show my baby off) (she also has Alloy doors )

[mr10ger]

very nice car!
well as youre using the S50 anyway, im just saying that were using the M50 manifold up to 750 HP over here in Germany and afaik the 500+ guys still use the OEM throttle body.
I only know about the torque curve of the 3.2l as N/A and ist almost flat like a Turbo engine. great engine to drive also. if it makes a big power difference between the M52 and the 3.0l 's vanos? i dont believe that, but it may also help your driveability. so go for it

[E36 HateR]

I made 717whp and 550wtq on a stock m50 vanos block, I'm sure with a 2.8 bottom end and a piston rod motor you can have a reliable 700whp depending on fuel and turbo size.

[someguy2800]

First nobody uses low compression pistons and a 3.5mm head gasket. It's either low compression pistons or stock piston and 3.5 mm head gasket. If you have the cash to turbo either motor I would pick the s50b30, but if money is a concern an m50 will make a hell of a lot of power for very little money. With an m52 or m54 stock crank and pistons in it and the 3.5 mm cutring spacer combo you can make 600 whp forever. Stock used non vanos valvetrain has no problem at 8000+ rpm but will eventually break the oil pump shaft or shear the harmonic balancer key if you make it a habit.

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I would go for wiseco pistons, rods of your choice, m54b30 or m52b28 crank, stock thickness cutring gasket, Achilles oil pump shaft new gaskets and valve seals and stock used everything else. Easy peasy reliable 600-700 whp

[mr10ger]

stock NV valvetrain will definately not rev 8000 rpm. this has been proven by many people as the most reknown BMW Custom Turbo manufacturer here in Germany. the TU starts losing valve collets at low 7000's. The valvetrain likely will not be killed immediately, but on long term the valves/seals will be killed by valve fluttering (i hope this is the right term) over 7200~7300 rpm.
If you think it works, try it, i wouldnt risk it. you can get new valve springs for 7500+ rpm for around 250 $ i think, why would you risk killing an engine for that Price?

also, the M52(euro) rods start bending at over 450 HP (depending on torque), some guy i know from the Internet tested it one day stay with the NV rods if possible, they should be good for at least 500 HP or more.

but as i said, i would go for the S50 for driveability

[someguy2800]

I've been over 8000 several hundred times on my stock 180k mile valvetrain. Seen as high as 8300 on datalogs.

[TheJuggernaut]

I would go for wiseco pistons, rods of your choice, m54b30 or m52b28 crank, stock thickness cutring gasket, Achilles oil pump shaft new gaskets and valve seals and stock used everything else. Easy peasy reliable 600-700 whp

Don't listen to anything he says ^^^ He spends tens of thousands, doing things just because the internet said so, only to run 12s.

It's opposite day.

[Nutzy]

also, the M52(euro) rods start bending at over 450 HP (depending on torque), some guy i know from the Internet tested it one day stay with the NV rods if possible, they should be good for at least 500 HP or more.y

Was that 450HP at 3000rpm or 7000rpm? Because your problem there is TQ, not HP.

[mr10ger]

@someguy: with stock M50 cylinderhead and hydraulic lifters? then the US Version definately has som other parts or youre just pretty lucky
@nutzy: it was a GT35-ish charger, so i dont think it was a diesel-like torque-line like i had. I've driven 516Nm @ 4000rpm (recalculate it to your non-metric System by yourselves :P) for a while on my stock M52 rods

[Nutzy]

@someguy: with stock M50 cylinderhead and hydraulic lifters? then the US Version definately has som other parts or youre just pretty lucky
@nutzy: it was a GT35-ish charger, so i dont think it was a diesel-like torque-line like i had. I've driven 516Nm @ 4000rpm (recalculate it to your non-metric System by yourselves :P) for a while on my stock M52 rods

Australia does not use the imperial system.

My point was that saying "450hp will bend stock M52 rods" is a pretty useless metric. Because if that 450HP is made at 6500rpm, it only needed 362ftlb to do it. If on the other hand you wanted to make that 450HP at 4500, now you need 525ftlb. Will the stock rods hack it? Maybe...
700HP at 7500rpm needs just 490ftlb, and maybe others could comment, but I'd think that is within the limits of stock rods.

The point of my blah blah is that on stock parts, sometimes it is wise not to let that turbo just 'go for gold' and hit max boost as early as it can. Ramping the boost up with RPM to keep the TQ line flat is a good idea, in some cases.

[someguy2800]

All stock. Do some looking and you will find others doing similar, its not that big of a deal.

[mr10ger]

@nutzy: thats why i wrote "convert it by yourselves" ;D yeah i know that, and ramping is what i will do when the base tune up to 0,6bar is done but theres snow on the streets right now . i also think i like the N/A-like torque-curve more.
i've done pretty much Research, thats why im saying that it cant handle more. i dont like statements that cant be proven, so im not just writing something. i've not tried it by myself, but i've talked to many People that have. one guy lost his valve collets two times on his TU engine at around 7000rpm. others have bent valves because they werent closed on TDC caused by valve flattering on high rpm.
i dont say youre lying, im just wondering why there are so different experiences about that?!

[someguy2800]

A TU uses 6mm valves and single straight springs. A non vanos uses 7mm valves and double springs. They are the same springs retainers and locks as an M20 with slightly different installed height on the springs.

[mr10ger]

just for my interest: do you know about the possible rpm on a M52 Zylinder head with the conical springs?

[someguy2800]

Never tried it so I couldn't say. Most people run 7300 limiters or so without problems.

[E36 HateR]

7300-7250 is usually where people stay at the limit with the single valvesprings and 6mm valves and s52b32 crankshaft.