525e ETA Crank

[Widge]

Ok guy I've just read the article from PBMW about 2.7's, and it says the eta crank is not safe above 6200 rpm. Some one who has built a 2.7 tell me this is not the case

[chu346]

From what i've heard it should be alright, unless you want to turbo it.
Why do you want to go above 6200 rpm? I'm planning on using an Eta crank.

[davrosbeemer]

I'm using an eta crank and block but understood that it will rev right round to the limiter if so inclined. Why is it going to be unsafe?

[Jimbob]

Like one of the lads have said, no good for further tuning like a turbo but is fine otherwise! The article recommends a 324td crank, seen one of those lately?

[E30Adam]

The 2.7 has enough torque not to have to go over 6,250 revs so the eta crank is fine for this conversion.

Remember, the M20 isn't a revvy engine compared to the likes of civic type R's etc. 7k max is quite adequate for this engine.

[gorgeee]

324td crank, seen one of those lately?

i got a 324d which has a good engine but body is crap
and i dont wana sell it before anyone asks but would like to know what the cranks worth

[Andy_magic]

The 324TD crank is forged, the 324D crank isn't.

I'm planning the same conversion and was thinking about these issues, I was wondering what the rev limit is set too on the zone chips. I know that some are 7100RPM which might be taking the pi55 on an ETA crank.

I know that if my car has a rev limit set at 7100 it's going to find itself up there in the heat of the moment.

[Andy335Touring]

I think Ant can make you a chip with a rev limit of your choice ?

Drop him a PM mate.

[Widge]

Thats what I was thinking, don't want to bosch the limiter in the heat of the moment to find 3 rods going through the right side of the block and 3 through the left that was all. I know the 2.7 are about torque but if it will rev I'll use it!

[Andy_magic]

Thats the exact answer I was hoping for. I will be on his case closer to the time. I'm still sourcing main bits at the moment (and funding it)

[Widge]

Check this out, it's from the article. I think they are slightly over exaggerating the issue, but hey there we go!

[Andy_magic]

My thinking (without any proof or info at all) is that would BMW make the cranks for M20B20/25 motors that rev to over 6k in stock form and then make a specially cr@p crank for the B27 that wont rev over 6k without twisting and generally falling apart?

I can't see it myself. When I get my chip I will be getting one with the limiter set at 6200 just to be on the safe side.

[Widge]

I agree. The quality control is probably not as tight, but then they have warranties to think of. Any of us could have a crap crank that snuck past quality control any way, I don't think it's really worth thinking about. I'll have 7k stamped on my chip

[Andy_magic]

Sounds fair enough to me mate, I've got a feeling that my 2.7 mite be breathing a bit deeper than a normal one, I'll look into it.

[Widge]

I think mine will breathe quite deeply too, thats why I'm going the 325 block pistons and head to release an exra few ponies with those big valves and shaply pistons!

[Andy_magic]

Sorry mate, I didn't mean it to sound like I was starting a pi55ing contest. I'm sufferening from post-turbo-procurement-syndrome at the mo

[Widge]

Not at all mate I just was kinda surprised to find people saying "but why would you want to go above 6200 with a 2.7" Mine at the mo revs to 7000 and I don't use it very often at all, but it's nice to know it's there. I'm suffering from post crank/green stuff procurement

[Andy_magic]

I can see where your coming from mate, I've had a few cars that have let go due to over revving them and am paranoid about it happening again. that coupled with the fact I'm an animal sometimes when driving i'll go for a safe-ish 6200 I think.

[Widge]

I'll see what ant says but I may be convinced to have a 6500k limiter. Dunno how goo his chip will be though, cos every 2.7 is different.

[Andy_magic]

Your going for the domed piston/combustion chamber route and I'm going for a flat top version. I know there are many benefits to the route your taking but the benefit for going flat top for me is cost.

I wonder how the chips will turn out in the two very different versions of the same idea.

When they are sorted maybe a shoot out is called for.

It's 2am, sleep time

[TVRTASMIN]

My 2.7 revs to 7k no problem. Has been lightened and balanced which will help.
As has been said, there is no real point in revving the 2.7 so high, as the peak torque and power will have dropped off anyway.

[TVRTASMIN]

Your going for the domed piston/combustion chamber route and I'm going for a flat top version. I know there are many benefits to the route your taking but the benefit for going flat top for me is cost.

I wonder how the chips will turn out in the two very different versions of the same idea.

When they are sorted maybe a shoot out is called for.

It's 2am, sleep time

I built my engine using the 325i donor pistons which were domed with valve cut outs. These i beleive are the high comp ones, which i need as the engine shop that decked the block and shaved the head, took off a tad too much. I have to use Optimax at every fill and be very careful when thrashing it as pre-ignition sometimes occurs. The timing was backed off as much as possible when it was R Roaded at Bexley 3 or 4 years ago.

[Andy_magic]

I managed to get hold of an E34 diesel turbo and manifold complete so I'm probably going to fit that too once all the bits are sorted so I don't really want to push the crank too far.

I can also get the crank for the E34 but no one seems to know if it will fit or not, the 324td crank is a drop in job, but I just know the E34 will be hassle.

[Andy335Touring]

Looks like its the same E30/34

And the non-turbo uses the same crank

[Andy_magic]

Interesting, I had been told the 324d has a regular crank, 324td has a forged crank.

The crank I can get hold of is a 325/525tds crank which according to my ETK is 11 21 0 004 024

I don't really know how to use the ETK, I can't find the same page youve shown in your post.. Maybe thats half of it.

Cheers for posting that.

[Andy335Touring]

All you do is click on the item number to bring up all the option's(like color,size etc) for that part,select the one you want so it goes blue and the part number appears in the box on the right,then press the Parts information button.



This screen gives you some more info like the weight of the part etc.To see weather the part your looking at is shared with another model press the Parts use button.



HTH

Andy

[Andy_magic]

Cheers mate, helped alot.

I'll have to see if I can get the crank out and try it in an M20 block, after a little net research of course.

It appears to be an 82.8mm stroke, I'll do the maths and see what capacity that gives.

[Widge]

• 320 - bore 80mm, stroke 66mm
  325 - bore 84mm, stroke 75mm
  327 - bore 84mm, stroke 81mm

So that'd work out at more than 2.7? Or would it depend on the con rod / piston combination used?
Then again how accurate is your measurement? Is it actually 81mm stroke?

[Andy_magic]

I think it works out at roughly 2753cc v 2693cc with an 81mm crank (ETA)

I found an engine size calulator on the web and stuck it in.

the added size is a bonus, albeit a small one, but the 325TDS runs a compression ratio of 22:1 and 2.2bar boost (just over 30PSI) so I reckon it would be man enough to run 10:1 and 6PSI albeit at a higher engine speed. I think the TDS is limited at 4800 or 5000 RPM much like an ETA.

The only reason I'm looking into it is that I can probably beg the whole engine as the top end has got big problems and has been replaced.

Trouble is, where do you stop. I was really happy with my 320i before I found this site

[Widge]

Do what I'm doing in essence. I'm happy with the 2.5, it's done 170,00 but runs better than my bros cab which has done 120,00. I'm going to build up a whole spare 2.7 engine as and when the funds allow and the parts are collected then at some time in the future it will be put in the car. By which time it will probably be bored out to 3ltrs with high comp pistons ITB's and a maf conversion. So the answer I suppose is that it never stops

[Widge]

Right the Crank has arrived, and it's in good condition

But is there any way I can tell if it's an eta? I didn't see it removed from the car so I'm suspicious And I haven't got any vernier calipers only a tape, are there any give away numbers on it?

[Andy335Touring]

I'd have thought there should be a part number on it some where ?

[Widge]

That's what I thought, but I can't see one, where do they normally hide them on cranks? anyone

[Davenotouring]

I thought there was a little 'e' marked on it.

This is 90% likely to be wrong.

[Widge]

No Dave they put those on the pills...
Know what I mean