M20B25 to M20B30 stroker & ECU help

[fxckrio]

Alright, so I have an 86 318i Baur, and have been looking into engine swaps, but due to local laws here in Australia, something like an M50 is more trouble than its worth, so I was looking into building an M20 stroker, and noticed that on the wiki that the b30 (biggest that doesnt need to be bored out) says that it uses "2.5i" pistons. Does this mean I can just keep/buy new m20 pistons, or do I need m54 pistons? Also ECU wise, I assume the stock one physically doesnt have the outputs for a 6cyl, so id need one from an m20 car, but would say an E28 ecu work or would I need either an aftermarket one/factory e30 ecu?

[martauto]

Welcome to the zone mate, another chap from down under,
I`m sure some one will know or advise what to do (not me , but I do have a Baur )
More pics please , are you the only one down there with a decent car, sorry , Baur ??

Mart.

[fxckrio]

Welcome to the zone mate, another chap from down under,
I`m sure some one will know or advise what to do (not me , but I do have a Baur )
More pics please , are you the only one down there with a decent car, sorry , Baur ??

Mart.

Honestly I've never seen another one around here lol, and I've got a few more pics here

https://photos.app.goo.gl/PaeuBWSgYTQKeQL19

[MrBenn2]

Hey man. You would need all the bits from an M20 325 engine at the very least to get this going. ECU, wiring loom etc. You would probably need larger injectors and an ECU retune to get it running at its best, but it might run on the standard tune.

[Tzantushka]

More pics please , are you the only one down there with a decent car, sorry , Baur ??

Welcome - another Aussie
First rule is Mart like to see pics...
Nothing happens without pics

Sounds like a full engine transplant for you - correct?
Out goes the 318 and in goes...
- Stroked M20B27?
- Or perhaps a good M20B25?

[fxckrio]

Hey man. You would need all the bits from an M20 325 engine at the very least to get this going. ECU, wiring loom etc. You would probably need larger injectors and an ECU retune to get it running at its best, but it might run on the standard tune.

Yeah thats what I was sorta thinking, so I'll probably see if I can find a parts car and most likely just splurge some extra on a decent aftermarket ECU.

More pics please , are you the only one down there with a decent car, sorry , Baur ??

Welcome - another Aussie
First rule is Mart like to see pics...
Nothing happens without pics

Sounds like a full engine transplant for you - correct?
Out goes the 318 and in goes...
- Stroked M20B27?
- Or perhaps a good M20B25?

Probably just finding an ETA engine & replacing the head would be the backup plan, but I'd like to build a 3.0 if possible, obviously if it ends up just being unrealistic then ill back out and go the ETA route

[steve_k]

if toy plan on building a b2 stroker then maybe the best route would be the 3L kit from the likes of ireland engineering,

also at the minimum you would need the likes of a piggyback ecu right up to full stand alone, then there's all the other supporting mods, cost of machine work etc.

as for the back up plan of finding an eta & replacing the head with an 885 head? that could work but dont expect massive power from going down the "burger king" route.

have a look in the wiki as there's a guide on building a 2.7 & also have a search through the forum as there is no single way of building a stroker of any combination,

but if you want to go down the 3L stroker route have a look for a thread from a member by the username of digger, there's loads of info in that thread (very technical).

[flybynite]

Probably just finding an ETA engine & replacing the head would be the backup plan, but I'd like to build a 3.0 if possible, obviously if it ends up just being unrealistic then ill back out and go the ETA route

I am sure DanThe built an M54 cranked stroker for Magpie a few years back but he does not go public with trade secrets for obvious reasons , maybe send him a PM?

Reggid on here (Digger on some other forums) is from your neck of the woods and has done most itterations and currently has a 3.3 IIRC

He is here sporadically

The problem with the M54 3.0 crank is it does get a whip on at high revs and thrashes round a bit.

If I were to build one as a good usable M20 it would be a 2.9 using the forged M52 crankshaft, 135mm rods and Mahle sport pistons sold by Ireland Engineering. The beauty of those are you can use a really scuffed up M20 block as you are boring it out to 85mm

Not the cheapest way to do it but currently one of the best IMHO

[DanThe]

I am sure DanThe built an M54 cranked stroker for Magpie a few years back

Micks is an M52, ive done quite a few M20 2.8's now, currently got a 3.2 in pieces that some fitterz killed and a 3.0 stroker build on the horizon for a customer

[fxckrio]

if toy plan on building a b2 stroker then maybe the best route would be the 3L kit from the likes of ireland engineering,

also at the minimum you would need the likes of a piggyback ecu right up to full stand alone, then there's all the other supporting mods, cost of machine work etc.

as for the back up plan of finding an eta & replacing the head with an 885 head? that could work but dont expect massive power from going down the "burger king" route.

have a look in the wiki as there's a guide on building a 2.7 & also have a search through the forum as there is no single way of building a stroker of any combination,

but if you want to go down the 3L stroker route have a look for a thread from a member by the username of digger, there's loads of info in that thread (very technical).

I'll definitely look down the ireland eng route then, cheers man
ECU wise if I want it tuned at all I'll 90% have to buy a haltech since thats what everyone here is used to so theres a fair chance I'll just go that route.

[flybynite]

Micks is an M52,

DOH! should have remembered that

[steve_k]

if toy plan on building a b2 stroker then maybe the best route would be the 3L kit from the likes of ireland engineering,

also at the minimum you would need the likes of a piggyback ecu right up to full stand alone, then there's all the other supporting mods, cost of machine work etc.

as for the back up plan of finding an eta & replacing the head with an 885 head? that could work but dont expect massive power from going down the "burger king" route.

have a look in the wiki as there's a guide on building a 2.7 & also have a search through the forum as there is no single way of building a stroker of any combination,

but if you want to go down the 3L stroker route have a look for a thread from a member by the username of digger, there's loads of info in that thread (very technical).

I'll definitely look down the ireland eng route then, cheers man
ECU wise if I want it tuned at all I'll 90% have to buy a haltech since thats what everyone here is used to so theres a fair chance I'll just go that route.

no worries, just thought the IE kit might be easier, as for the ecu? might have a look at haltech myself.

[reggid]

lots of ways to skin a cat. Below are IMO

Firstly you want minimum 85mm slugs (ok maybe 84.5 is ok) to get fresh bored and honed cylinder walls.

Cant use OE 325i slugs without a decent amount of massaging the crowns and skirts and short rod which wont save you anything and just cause possible weakness.

24V 135mm rods are ok, Molnar are the best aftermarket rods from a value perspective if you want some invisible bling

pistons you can use a flat top OE piston from some random BMW or other with correct bore, compression height, and pin size but flat top pistons are better with the 731 head which needs a shed load of porting to get acceptable and you need to cut valve pockets.

you can get forged flat top style but again these are better with the 731 , the flat top is not how it should be done with the 885 based on basic engine building principles

best bet is forged 4032 alloy slugs for a NA engine ( or 2618 alloy for turbo). I highly recommend getting the dome replicas of stock pistons. There are few places in the US that do them topend and Mahle MS.

Avoid IE , VAC and those places if you want pistons for a big crank engine. IE do a nice set of Mahle MS slugs for a 2.8L but not for the 3L which will be some generic dome, which while works is not how it should be done in 2021 with everything that is known.

a set of forged slugs is like $1000 USD + postage and duty/tax

There are some economical ways to get to 2.8L using OE parts if on a tight budget

[fxckrio]

lots of ways to skin a cat. Below are IMO

Firstly you want minimum 85mm slugs (ok maybe 84.5 is ok) to get fresh bored and honed cylinder walls.

Cant use OE 325i slugs without a decent amount of massaging the crowns and skirts and short rod which wont save you anything and just cause possible weakness.

24V 135mm rods are ok, Molnar are the best aftermarket rods from a value perspective if you want some invisible bling

pistons you can use a flat top OE piston from some random BMW or other with correct bore, compression height, and pin size but flat top pistons are better with the 731 head which needs a shed load of porting to get acceptable and you need to cut valve pockets.

you can get forged flat top style but again these are better with the 731 , the flat top is not how it should be done with the 885 based on basic engine building principles

best bet is forged 4032 alloy slugs for a NA engine ( or 2618 alloy for turbo). I highly recommend getting the dome replicas of stock pistons. There are few places in the US that do them topend and Mahle MS.

Avoid IE , VAC and those places if you want pistons for a big crank engine. IE do a nice set of Mahle MS slugs for a 2.8L but not for the 3L which will be some generic dome, which while works is not how it should be done in 2021 with everything that is known.

a set of forged slugs is like $1000 USD + postage and duty/tax

There are some economical ways to get to 2.8L using OE parts if on a tight budget

Aight I'm gonna bite then, can you send links/info on building a 2.8 with oe parts? Since that definitely seems up my alley and losing 200cc won't kill me

[steve_k]

here's one to get you started

https://www.e30zone.net/e30wiki/index.p ... ding_a_2.8

[flybynite]

Avoid IE , VAC and those places if you want pistons for a big crank engine. IE do a nice set of Mahle MS slugs for a 2.8L but not for the 3L which will be some generic dome, which while works is not how it should be done in 2021 with everything that is known.

I agree about the 3.0 pistons, they seem to be just from VAC now. Paying for custom pistons you might as well do it right

I think that 2.8 Mahle Motorsport piston is now sold as a 2.9 (because of the 85mm bore) , it is the only one Ireland do now for the M20 it seems. It is 10.1 but I guess we are splitting hairs

https://www.iemotorsport.com/product/2- ... mahle-m20/

As above that would be what I would use with a clean sheet

Given the car it is going in, a 2.7 was more appropriate for me especially as I have the forged 81mm crank to work with. Steve Nelson did me proud with these

[fxckrio]

here's one to get you started

https://www.e30zone.net/e30wiki/index.p ... ding_a_2.8

much appreciated, honestly seems like the best option taking everything into account and ill probably go that route, cheers bro

[steve_k]

here's one to get you started

https://www.e30zone.net/e30wiki/index.p ... ding_a_2.8

much appreciated, honestly seems like the best option taking everything into account and ill probably go that route, cheers bro

no worries keep us all updated,
if you get stuck there's plenty on here who've done that build before.

[reggid]

Avoid IE , VAC and those places if you want pistons for a big crank engine. IE do a nice set of Mahle MS slugs for a 2.8L but not for the 3L which will be some generic dome, which while works is not how it should be done in 2021 with everything that is known.

I agree about the 3.0 pistons, they seem to be just from VAC now. Paying for custom pistons you might as well do it right

I think that 2.8 Mahle Motorsport piston is now sold as a 2.9 (because of the 85mm bore) , it is the only one Ireland do now for the M20 it seems. It is 10.1 but I guess we are splitting hairs

https://www.iemotorsport.com/product/2- ... mahle-m20/

As above that would be what I would use with a clean sheet

Given the car it is going in, a 2.7 was more appropriate for me especially as I have the forged 81mm crank to work with. Steve Nelson did me proud with these


Piston 1.JPG

Yes those are the 2.9 Mahle ms ones I meant.

That one from top end are the correct shape piston for the m20 with 885 cylinder head. If someone wants a 3.1L the same pistons with adjusted compression height are the best bet. My recommendation would be to get total seal conventional rings ( total seal brand but not gapless) where possible