High comp or low comp??

[oakey]

[e301988325i]

Am I missing something Dave? That's clearly an E for early HC, K is later LC.

[Simon13]

high comp bert

[fowler]

high comp bert

+1 oops

[bss325i]

According to realoem 256E2 is from 9/87 on with no cat so i would say low comp.

256E1 is upto 9/87 with no cat so i would say that is a high comp.

256K1 is from 9/87 with a cat (the K in 256K1 is an abriviation for Katalysator which is german for catalitc converter so this will also be a low comp engine.

http://www.realoem.com/bmw/showparts.do ... g=11&fg=05

I will confirm this tomorrow.

[Speedtouch]

I gather all the 25 6E blocks are high compression. My 1988 F-reg 325iSE had one and it went like stink!

[bss325i]

256E2

25 denotes the engine size

6 denotes the number of cylinders

E denotes engine concept with E being injection

2 denotes the differentiation index with 2 being the second, ie low comp as that came after 1, high comp.

See page four of this very usefull PDF file.

http://www.ge39.com/files/zeigeinfo.pdf

I guess thats squashed that myth!

[B7]

256E2

25 denotes the engine size

6 denotes the number of cylinders

E denotes engine concept with E being injection

2 denotes the differentiation index with 2 being the second, ie low comp as that came after 1, high comp.

See page four of this very usefull PDF file.

http://www.ge39.com/files/zeigeinfo.pdf

I guess thats squashed that myth!

This needs clarifying? Everyones been led to believe 6E high comp. 6k low comp.

[Speedtouch]

256E2

25 denotes the engine size

6 denotes the number of cylinders

E denotes engine concept with E being injection

2 denotes the differentiation index with 2 being the second, ie low comp as that came after 1, high comp.

See page four of this very usefull PDF file.

http://www.ge39.com/files/zeigeinfo.pdf

I guess thats squashed that myth!

As interesting as that is, it doesn't specifically define 1 as high comp and 2 as low comp

[Jamese30]

So who fancies dismantling their engines and doing a volume measurement..??

only joking...

[oakey]

256E2

25 denotes the engine size

6 denotes the number of cylinders

E denotes engine concept with E being injection

2 denotes the differentiation index with 2 being the second, ie low comp as that came after 1, high comp.

See page four of this very usefull PDF file.

http://www.ge39.com/files/zeigeinfo.pdf

I guess thats squashed that myth!

As interesting as that is, it doesn't specifically define 1 as high comp and 2 as low comp

Good point. Can you explain why you think the 1 and 2 will refer to the comp ratio?
What's the engine code on yours barry?

[bss325i]

Because the the E and the K refer to type, not compression ratio. E is for fuel injection and K is for catalytic converter (on M10, M20 and M30 only)

Its clearly states that on page 4 of that PDF file (of an official BMW document) in the link i posted.

The digit after E or K denotes the differentiation index, ie 1 being the first, 2 being the second.

256E1 = upto 9/87 non cat and of the first differentiation, ie high comp (9.4:1)

256E2 = from 9/87 non cat and of the second differentiation, ie low comp (8.8:1)

256K2 = from 9/87 cat (and i think cat prepped) and of the first differentiation, ie low comp (8.8:1)

I will have to check what mine is Dave but it think its 256K1, mine is cat prepped but doent have the cat itself.

[Speedtouch]

But how have you drawn the conclusion that the differentiation number refers specifically to compression ratio?

The document appears to make no validation on this, unless I missed something...

[bss325i]

Because the high comp came out before the low comp.

Something else has come to light that may throw this theory out.

More tomorrow.

[Andyboy]

Early ones are 9.75.1, later plakky bumper cars are either 9.4:1 or 8.8:1.

[bss325i]

Why do BMW state only two compression ratios for the M20B25

9.4:1 or 8.8:1?

[Andyboy]

They don't, they state three. 9.75 in the old chrome bumper version handbook and the other two in the later handbooks.

[oakey]

So the above engine number is that of a 9.4:1 comp ratio engine???

[bss325i]

Andy, i checked it out at work on BMW TIS. It only states 9.4:1 and 8.8:1.

I checked '85, '86, '87, '88, '89 etc.

No mention of 9.7:1.

[Andyboy]

Well, then TIS is wrong. The original 1985 owners handbook states 9.7, so does the original 325i technical bulletin from 1985 and I got a mate to check the Mahle piston catalogue which actually states 9.75 on early cars.


To check, I trawled through ETK and found three different slugs (standard bore Mahle)

Up to 9/87 11251708861 = this must be the 9.7

From 09/1987 to 06/1988 11251718924 = early plastic bumper, probably 9.4.

From 06/1988 11251735760 = Later plastic bumper, probably 8.8

[Speedtouch]

So, 25 6E1 probably refers to 9.75 CR while 25 6E2 is the 9.4 CR (presumably).

[bss325i]

You are right about three specific dates for pistons but interestingly on the etk it lists 3 different engines.

256E1 Up to 9/87 11001730858

But what is missleading is this, both engines are listed from 9/87, neither of them upto 6/88

256E2 From 9/87 11001730889

256K1 from 9/87 11001730862

[bss325i]

So, 25 6E1 probably refers to 9.75 CR while 25 6E2 is the 9.4 CR (presumably).

This is what its begining to look like i guess.

Strange that the most up to date version of BMW's TIS (Technical Information System) only mentions 9.4 and 8.8.

Conflicting data doesn't make things easy!

[Speedtouch]

Where's Ant when you need him? I'm sure he knows the definitive answer!