full fat m20b25 spec

[steve_k]

Right time for an update.

so far the spec i'm going with is as follows.

+1mm rebore/extreme hone.
HD bearings & shell's from ireland engineering.
BBTB (64mm).
stage 3 griffin motorsport cylinder head, ported, polished & gasflowed, 3 angle valve seats, welded water ways. (got a copy as a spare).
284/272dg cam.
magnex 6 branch manifold.
X-pipe on the end of the down pipes (next to the gearbox).
full stainless steel exhaust (single box) system, fully insulated/heat wrapped.
(massisve) K & N style twin cone air filter (had it laying around ages).
Remapped ECU.

future mods,
standalone ECU, ms3, or M5x.
coil on plug.
MAF conversion.
lightened flywheel.
custom 6 branch (RD copy).
maybe H section steel rods.
ARP bolts.
anything else i can think of over the next 12 months.
so, what sort of power do you thing the current set up will give?

[steve_k]

Forgot to add i wasn't able to get a power output as the remap was done by a mate of mine who does live mapping on the road from time to time.

[HairyScreech]

Wouldn't worry about the hd bearings, the stock bearings are man enough for quite a lot as the engine is a 7 bearing set up.
We are not lumbered with 5 bearings for 8 bores like the American boys.

[steve_k]

right then. just a quick question,

i've been offered a m20b25 bottom end that according to the owner has been fully rebuilt & had a 1 - 2mm overbore/rebore as part of it's rebuild & what i would like to know is this.

if it has been rebored by upto 2mm (is this even possible?) what kind of increase in CC would it give? also what would the cylinder bore diameter be? (if i was to measure it with a set of vernier calipers?

i only ask as i don't fancy paying top dollar for a b25 thats just had a simple strip down & rebuild.

thanks in advance folks.

[sean_318i]

Standard m20 b25s are 84mm bore, so if its bigger than this its rebored.

HTH
Seán

[reggid]

simple maths

Vol = PI*D^2/4*S*6

where

D=bore
S=stroke
PI= 3.14159

std = 3.14159*8.4^2/2*7.5*6 = 2,494cc
+1 = 3.14159*8.5^2/2*7.5*6 = 2,554cc
+2 = 3.14159*8.6^2/2*7.5*6 = 2,614cc

[steve_k]

Cheers digger

at least I now know what i'm looking at, & fingers crossed it has been rebored +2.

[bmwmaster]

OK fair enough, would like to hear an m20 at 8000 rpms!

I would be curious to know if they used the stock timing belt, I am not sure it would be suitable for high revving, high precision valve trains.

look here:

[youtube][/youtube]

[HairyScreech]

If it has been rebored 2mm i would question what pistons have been used. There are only a few options for pistons and all of them are not cheap, if it seems too good to be true then it probably is.

[steve_k]

If it has been rebored 2mm i would question what pistons have been used. There are only a few options for pistons and all of them are not cheap, if it seems too good to be true then it probably is.

well all I can say is that the guy who built the engine builds rallycross engines as a bit of a hobby & i've yet to see one let go, & he does not do anything on the cheap.

also the price (which i'm keeping sctum about) is a good one as he's an old friend of the family

[steve_k]

well i thought i'd better update this thread,

not long after my last post (nearly 2yr's ago ) i was offered an engine by a mate of mine who builds N/A rally cross engines who's also an e30 freak,

he had at the time a hartge h26 which spun a shell, so he decided to rebuild the engine (genuine h26 block stamoed MB16E) to a higher spec,
he took the old crank out (in my shed now ) & based the spec around a m50 crank, I beam rods & +1mm oversize pistons. baffled the sump with an extension plate he made himself.

for some reason he left the head nearly standard except for a shcrick dual profile cam (can remeber what spec), fitted m50 17.5lb/hr injectors & had it all mapped up & run in,

sadly a few months later the car was rear ended & written off but he kept the salvage.

he then offered me the engine for a price i just couldnt say no to. that then went into my sport but not before i fitted one of the griffin stage 3 heads i've got, a magnex 6 branch, X-pipe, BBTB & a few other bits.

i dont know what power its putting out but i do know its a hell of a lot more fun than a normal/tweaked b25, also the cc is 2554



i really need to get it mapped again & see what its putting out, future plans include a IJ crank scraper, lightweight flywheel & if/when funds allow stand alone & cop.

[Pinchy_Larou]

well i thought i'd better update this thread,

not long after my last post (nearly 2yr's ago ) i was offered an engine by a mate of mine who builds N/A rally cross engines who's also an e30 freak,

he had at the time a hartge h26 which spun a shell, so he decided to rebuild the engine (genuine h26 block stamoed MB16E) to a higher spec,
he took the old crank out (in my shed now ) & based the spec around a m50 crank, I beam rods & +1mm oversize pistons. baffled the sump with an extension plate he made himself.

for some reason he left the head nearly standard except for a shcrick dual profile cam (can remeber what spec), fitted m50 17.5lb/hr injectors & had it all mapped up & run in,

sadly a few months later the car was rear ended & written off but he kept the salvage.

he then offered me the engine for a price i just couldnt say no to. that then went into my sport but not before i fitted one of the griffin stage 3 heads i've got, a magnex 6 branch, X-pipe, BBTB & a few other bits.

i dont know what power its putting out but i do know its a hell of a lot more fun than a normal/tweaked b25, also the cc is 2554



i really need to get it mapped again & see what its putting out, future plans include a IJ crank scraper, lightweight flywheel & if/when funds allow stand alone & cop.

Interesting thread Steve, how did this turn out or was the project shelved.....?

[steve_k]

hi dude, thanks for digging this thread up as i need to update it

the engine is still going strong, only changes now are it's got a sump baffle extension plate in the sump & i've got a Teflon lined/coated IJ crank scraper/windage tray winging it's way from the land of the strangewhich should be here in the next 3-4 week's.

the only part of the plan thats been shelved is the stand alone ecu, mainly while i collect the parts for an ITB set up, true i could get one from RHD engineering but i like to do things myself (less chance of a third party fuck up) also i already have the template for the inlet manifold so it would be rude not to use them

my just buy an MS3x ecu kit to build up later in the year.

thats all for now but as soon as something happens i'll be sure to post it up

[Pinchy_Larou]

No probs, it was a good read. Been trawling all the M20 threads trying to get some ideas as I've just pulled my recent purchase apart and need inspiration / direction taken from everyones knowledge on here. I'm pretty certain I will be adding a tubby in the not too distant future so will take the time to build it right (forged) and pinch a couple of ideas from this thread

Look forward to your updates

[steve_k]

No probs, it was a good read. Been trawling all the M20 threads trying to get some ideas as I've just pulled my recent purchase apart and need inspiration / direction taken from everyones knowledge on here. I'm pretty certain I will be adding a tubby in the not too distant future so will take the time to build it right (forged) and pinch a couple of ideas from this thread

Look forward to your updates

no worries dude, it's about time the m20 was shown some love lol.

as for the hairdryer, i might go down that route myself one day

[Pinchy_Larou]

[/quote]as for the hairdryer, i might go down that route myself one day [/quote]

Haha..!! I'm not really that brave....

[steve_k]

as for the hairdryer, i might go down that route myself one day [/quote]

Haha..!! I'm not really that brave.... [/quote]

well...........................

i do have a spare lump in a mates workshop so might use that lol

[Eddie25]

I love the M20.

Slightly off topic but I had the x pipe taken out of my exhaust system yesterday and swapped it with true dual pipes from the BTB. The rest of the system is standard Fritz. Long story short I was having trouble with the gaskets blowing out between the x-pipe and mid section. I also fancied a slightly different tone.

If it has lost any power it certainly doesn't feel like it but the best part is the noise! It's no louder than before but has much more of a howl. In a way it reminds me of an old 60's straight 6 like a jag or TR6. Seriously addictive and I wish I'd done it that way years ago. It still has zero drone and is lovely and quiet in the cruise.

[Pinchy_Larou]

I love the M20.

Slightly off topic but I had the x pipe taken out of my exhaust system yesterday and swapped it with true dual pipes from the BTB. The rest of the system is standard Fritz. Long story short I was having trouble with the gaskets blowing out between the x-pipe and mid section. I also fancied a slightly different tone.

If it has lost any power it certainly doesn't feel like it but the best part is the noise! It's no louder than before but has much more of a howl. In a way it reminds me of an old 60's straight 6 like a jag or TR6. Seriously addictive and I wish I'd done it that way years ago. It still has zero drone and is lovely and quiet in the cruise.

Interesting, sounds like something I need to try...!

[steve_k]

right thought i'd better update this thread,

at the end of this month the "new" m20 2.6 lump will be going into my sport (at long last!!!!).

final spec is.

m20b25 block over bored +1mm to 85mm to give a CC of 2554

m52b25 crank, knife edged, & balanced.

m20 135mm rods with +1mm slipper pistons.

total seal rings.

ARP rod bolts.

teflon lined crank scraper,

sump baffle extension plate.

BBTB.

port matched inlet manifold.

stage 3 griffen motorsports cylinder head (port, polish, gas flowed, 3 angle vale seats).

green top m50 injectors,

oil catch tank with internal baffles.

3 bar FPR.

silicone inlet hose/elbow.

magnex 6 branch manifold.

X-pipe.

2 inch exhaust pipes to single scorpion back box. all heat wrapped.

fully mapped ecu (live mapped on the road).

the engine was built for me by a good friend who normally build ford X-flows/kent lumps & loves to build a strong N/A engine, but he has done a few bmw straigh 6's before.

it was all run in & mapped in his own lachs silver 2 door, so is ready to drop into my sport hopefully at the end of the month.

having taken his e30 out with this lump in i have to say it's a hell of a lot of fun to drive
it has plenty of low down grunt & a nice fat midrange (bit like the driver ) though it was running a 3.6 diff.

as for power/dyno numbers?? IIRC it was in the region of 200+ & same for torque, but at the end of the day bhp numbers don't interest me at all, they can change from day to day & dyno to dyno.

& the cost for all this was simply a straight swap for my H27 lump/bottom end.

can't wait to get it in my sport & see what it's like with a 3.91 diff.

wish me luck.

[SeanOB]

cool!! what's the redline

[steve_k]

cool!! what's the redline

7K for the time being

[reggid]

what cam and CR?

[steve_k]

what cam and CR?

i knew i forgot to add something

cam is a schrick dual profile 274/282 IIRC & CR of 10.2.

[reggid]

or maybe you mean 284/272? that would be a shelf grind

[steve_k]

or maybe you mean 284/272? that would be a shelf grind

thats the one, sorry to early in the morning, not woke up properly lol.

[Steven320]

Maby a diff. Story... Will the harmonic damper survive higher rpm then 7k?

Steven

[steve_k]

Maby a diff. Story... Will the harmonic damper survive higher rpm then 7k?

Steven

to be honest with you i'd have to speak to the guy who built the engine about that,

but to be honest i very much doubt that i'll be taking it above 7K as the power starts to tail off at about 6500rpm.

[steve_k]

Maby a diff. Story... Will the harmonic damper survive higher rpm then 7k?

Steven

just read your quote properly sorry,

IIRC the harmonic balancer/damper was balanced at the same time as the crank, but like i said i would have to speak to the engine builder to find out for definite.

[steve_k]

i'm glad this has popped up as i need to update it.

hopefully the final part of the puzzle is on it's way to me.

a rebuilt 3.73 LSD with 40% lock

it was lively in the builders car with a 3.9 lsd so i wonder what it's going to be like with a 40% lock 3.73 LSD.

[reggid]

The harmonic balancer will be fine unless it's old and ragged as they do delaminate eventually and it can slip and distort throwing the crank sensor out....

[steve_k]

WOW 2yr's since i last updated this thread,

been a few changes since then, the last spec decided to spin a shell so was torn down.

the full & final spec is as follows.

m20b20 block bored out to 84mm to guarantee fresh bores, fitted with m50 type oil squirter/piston oilers, & O ringed with annealed stainlees steel wire.

m20b23 crank, bullnosed, lightened, balanced, shot peened,micro polished,

skimmed flywheel.

ACL tri-metal bearings.

H section steel conrods, ARP rod bolts.

high comp 84mm slipper pistons with total seal rings.

billet m50 tall boy main caps. ARP main studs.

custom dual crank scraper/crank girdle.

sump baffle extention plate.

port matched inlet manifold, BBTB.

m50b25 fuel rail & 17lb injectors,

rebuilt stage 3 griffin motorsport head (welded up water ways & O ringed)

schrick 284/272 camshaft, HD rockers & double valve springs, vernier cam gear (to get timing spot on).

ARP head studs.

gates racing kevlar timing belt.

refurbished porsche 944 afm,

magnex 6 branch manifold, X pipe on the end of the down pipes,

just waiting on a chance to get it all mapped properly but at the moment running on a tweaked chip.

all being well will be going into my sport in the next week or so,

as for bhp/torque? not a clut but anything in the 190++ region will do me.

[flybynite]

Nice! I do like the sound of this. It is the sort of thing that gets my interest, especially as I have both a M20B23 and a M20B25 to play with so I have a good 80mm block to bore out to a clean 84mm and a good known B23 crank.

I would probably only do the semi-skimmed version but it would still make a good engine.

What did you do to compensate for the increased throw of the B23 crank? Was it dealt with by the head, the pistons or the rods? I was obviously going to go down the route of the oversize head gasket but curious if there is a better option.

You will certainly have to let us know how it runs!!

[steve_k]

Nice! I do like the sound of this. It is the sort of thing that gets my interest, especially as I have both a M20B23 and a M20B25 to play with so I have a good 80mm block to bore out to a clean 84mm and a good known B23 crank.

I would probably only do the semi-skimmed version but it would still make a good engine.

What did you do to compensate for the increased throw of the B23 crank? Was it dealt with by the head, the pistons or the rods? I was obviously going to go down the route of the oversize head gasket but curious if there is a better option.

You will certainly have to let us know how it runs!!

thanks bud

if you've got the parts then why not go for it? it's what i did with what i had to hand.

as for the compensating for the extra throw of the crank, a 2.5/2.7mm MLS head gasket was used, but thats what i was told by the engine builder (an old skool N/A rally engine builder).

looking forward to getting it in the car & out on the road,