Confused engine

[Skar]

I have a friend who has a wierd engine config, when he bought the car, the previous owner said it was an 325e. But we took a closer look at it and found out there were some things that were not ment to be there. By right his engine shouldnt start or will be damaged really quickly.

this is the config or parts used on the engine.

1. m20b20 head
2. m20b23 ecu (L-jet system)
3. m20b27 block and wiring
4. m20b20 air flow metre

there is excessive smoke during down shifting and acceleration.

can anyone explain me how this works or what kind of damage is this doing to his engine becuase i am puzzled

[Quaser]

sounds like a cheap way of doing the 2.7 conversion. Car should have lots of torque low down.

The block and the head go together as the piston shapes are the same, and all m20 blocks are the same size externally.

What year is the car - maybe it was originally a jetronic system and he decided not to change it!

[Skar]

the car is an 84 model, but the current owner tought it was a proper eta but it isnt, it does have a lot of low end torque but the car runs out of breath after 4000rpm. the car is running lean due to the lack of air going into the engine

[Gwynleym10]

Are you in the states mate?

[Templ8e30]

If it has the 2 and 2.3 litre injectors it will be under fuelling possibly causing the reluctance to rev.

Would be a good idea to get it on a rolling road to see what's needed to get it to run properly.

Cheers,

Iain T

[Skar]

No man i am not in the states, i am from malaysia, the car is definately running lean, its running on b20 injectors and b20 AFM. the car is running but it does look like its running well. first of all the head needs to be changed and the AFM needs to be atleast a 2.5 one.

[Geeman]

Keep the head, but port it to match a 2.5 inlet manifold. With this, the 2.5 injectors, throttle body and AFM, the car should run much better. You also need a 2.5 chip/ECU...

Hope this helps...

Giles.

[Skar]

Keep the head, but port it to match a 2.5 inlet manifold. With this, the 2.5 injectors, throttle body and AFM, the car should run much better. You also need a 2.5 chip/ECU...

Hope this helps...

Giles.

hmmm...not a bad idea....thanks that might be overall cheaper here to do that, rather than looking for the b25 head itself, i do have some b25 parts lying around somewhere. thanks man for the idea.

[Geeman]

No problem. Happy to help.

You may also want to put a 2.5 cam in the 2.0 head. This will make a lot of difference too.

So to go over it again, keep the head and block, but mate up a 2.5 inlet manifold with the 2.5 injectors, throttle body and AFM, a 2.5 cam and a 2.5 ECU/chip.

This should give you a much more usable 2.7 unit with loads of torque.

[Skar]

so does that mean that the b20 head is almost identical to the b25 except for the cams and maybe the valve size? just want to make things clear.

[Geeman]

Not quite sure about specifics, but I do know the b20 fit on the Eta block with no hassles, where as the b25 will require some modificatiosn to get it to run / mate up correctly.

[Quaser]

i think that the problem with the b25 head is the piston shape. The b20 pistons are flat topped as are the ones from the eta lump.

2.5 engines have the funny dome shape, so mating a 2.5 head on an eta block causes unwanted pinking (what i have been told) due to the extra space in the head!

Q

[StuBeeDoo]

so does that mean that the b20 head is almost identical to the b25 except for the cams and maybe the valve size? just want to make things clear.

No. The combustion chambers are a different shape. You need the right pistons for whichever 'head you use. If you don't match the 'head and pistons, you'll either end up with piston/head contact, or at the opposite extreme, too much combustion chamber and an engine that runs, but like a bag of s**t.

[StuBeeDoo]

the car runs out of breath after 4000rpm.

It's probably still got the ETA cam in then!!

[Skar]

thanks for the feed back, from what i know the pistons are still eta and the head is definately a b20, but not sure about the cams, i think the previous owner is a bit dodgy, it looks like he just put the engine together for the sake of getting the car running...just to sell it...

[Andy_magic]

If the cam in the B20 has seven bearing surfaces its from a B20, only four and it's from a B27 ETA.

As far as I know the B25 is a no no in a B20 (731) head casting, don't know why.

What ECU/Chip is it running, when does the rev limiter cut in 4800 or 6500 rpm??

[StuBeeDoo]

As far as I know the B25 is a no no in a B20 (731) head casting, don't know why.

See above!

[Skar]

the car can be taken up to 6500 rpm but looses its breath at around 4000 rpm. it is also using the ecu from a b23 and its a L-jet system.

[Andy_magic]

Sounds like it's got the ETA cam in then, my 525e gets very wheezy above 4000 rpm

[chu346]

As far as I know the B25 is a no no in a B20 (731) head casting, don't know why.

See above!

???

[StuBeeDoo]

As far as I know the B25 is a no no in a B20 (731) head casting, don't know why.

See above!

???

Three posts above Andy's I said why you can't use the 731 head on a '25.

[Skar]

If the cam in the B20 has seven bearing surfaces its from a B20, only four and it's from a B27 ETA.

As far as I know the B25 is a no no in a B20 (731) head casting, don't know why.

What ECU/Chip is it running, when does the rev limiter cut in 4800 or 6500 rpm??

just to make things clear....are saying that b25 cams cant go into a b20 head?

[StuBeeDoo]

See above!

???

Three posts above Andy's I said why you can't use the 731 head on a '25.

Sorry, thought Andy was talking about heads/blocks. Is he on about the camshaft??

[Skar]

i am not sure he went a bit too technical hehe

[chu346]

I take it you mean this one,

so does that mean that the b20 head is almost identical to the b25 except for the cams and maybe the valve size? just want to make things clear.

No. The combustion chambers are a different shape. You need the right pistons for whichever 'head you use. If you don't match the 'head and pistons, you'll either end up with piston/head contact, or at the opposite extreme, too much combustion chamber and an engine that runs, but like a bag of s**t.

but it doesn't mean you can't use a 2.5 cam in a 2.0 head. It's the 2.7 head which doesn't have the oil galleries for the 2.5 cam.

The 2.0 head and the 2.7 head are identical apart from the oil ways, thats why you can't use the 2.5 cam.

[Geeman]

Right... a 325 cam WILL go into a 320 head which WILL fit on a 325e block. (which is what we were talking about... I think!)

325e (or indeed a 525e) block is different to a 325i block... therefore a 320i head will fit straight on.

Just to clear things up!

[chu346]

BTW its the pistons that are different and supposedly the block is about 1mm taller but otherwise all blocks are the same.

[Skar]

Yes that is what we were talking about, thank you. Atleast the poor guy with this confused setup will be abit happier.

[Andy_magic]

Just to clear things up my end:

I have read numerous posts about B25 camshafts being a no no in a 731 B20 head. I don't know why, but I have seen it posted a good few times.

The B27 head can have the extra oilways drilled out to accept a 7 journal cam.

The B25 & B27 blocks are the same, the B27 has a longer throw crank and different pistons with (I think) shorter skirts and (I know) different crown profile to suit the (nicknamed) flat head. This is how you can use either a B20 or a B25 head on the B27 block. With the B25 head you need to get the deck of the block shaved to allow the B25 pistons to get the proper compression ratio, otherwise you end up with 8.3:1 comp ratio. If you use the B20 & B27 head you get either 10.x:1 or 11:1 if you use an early B27 engine.

Just to confuse matter even further, there is also whats known as the Super ETA which has (I think) a 9.3:1 comp ratio but the same valve sizes as a 325. all other heads have 2mm smaller valves all round.

Budget 2.7 components:

325/525e block, pistons, rods, crank & 320i head, bolts straight on and works... loads of torque, if used with 325i engine management system gives about 180bhp.

Expensive 2.7 components:

325e/525e block and crank, 320i rods, 325i pistons, 325i head. machine work is needed to deck the block down to give decent comp ratio. Gives about 190/195 bhp when 325i engine management system is used

It does get confusing with all these designation numbers B25/B20/M20 etc etc.

[Skar]

well said thanks for the help