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E39 fanboi
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Discussion Starter · #1 ·
I'm in the middle of preparing for an engine swap (M52B20->M52B25).

As i'm going to replace the VCG (it's kinda leaky) i'm not sure if I should do this before or after i've swapped the engine. While it's easier before installing the new engine, i'm afraid the hoist if lifted from engine hook (near vanos) will stress the gasket/seal?

Oh and another thing, the rear diff is 3,46 now but the engine came from a 523 that supposed has 3,23 or in special cases (3,46) - what would it mean if I drove around with a 3,43 ratio (higher) than normal spec? I assume revs / speed will be unchanged?
 

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Older than old school
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Since the replacement engine came from a car with a different rear end, you might need to reprogram your powertrain control module, which handles the interaction between the engine and transmission. Revs/speed would not change for your car from what you had with the previous engine, but if the donor car had a different rear end, it makes me wonder whether your transmission also has different gear ratios.
 

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Discussion Starter · #3 · (Edited)
I forgot to say that my car has a manual gearbox and that the new engine came from one with steptronic.

According to this calculator I will end up with 2755 RPM @ 60 MPH with the 3.46 ratio and 2572 RPM @ 60 MPH with a 3.23 ratio. So while the RPM / mph would be unaltered from my current setup the 0.5L extra may cause my consumption to rise marginally?

I usually drive around max 30.28 mph so the RPM difference would only be 1712-1598 = 114 RPM compared to a stock 523i.
 

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I forgot to say that my car has a manual gearbox and that the new engine came from one with steptronic.

According to this calculator I will end up with 2755 RPM @ 60 MPH with the 3.46 ratio and 2572 RPM @ 60 MPH with a 3.23 ratio. So while the RPM / mph would be unaltered from my current setup the 0.5L extra may cause my consumption to rise marginally?

I usually drive around max 30.28 mph so the RPM difference would only be 1712-1598 = 114 RPM compared to a stock 523i.
Higher revs doesn't always mean higher consumption - I believe that engines have different sweet spots depending on revs and what you're doing with the throttle (near closed, open, full, etc). Also bear in mind that you can shift earlier with a 3.46 rear.

Are you swapping the DME (engine control unit) or having it reprogrammed? Re: the diff in your car, the 520i has smaller CV joints on the half-shafts compared to the other I6s so maybe be careful if towing etc. with your new engine!

Let us know how you get on with your engine swap!
 

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You don't need to program a thing--stay away from stuff like that. On the engine swap, go ahead and install the new valve cover gasket while the engine is out. You can get to everything with ease. You really should
install new Vanos seals and oil filter housing and CCV valve while the engine is out also. It would be a breeze
to do all this when you can get to everything. My 2 cents
 

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E39 fanboi
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Discussion Starter · #8 ·
I am going to reprogram the DME to a 2.5L, they use same part #, but it has a different programmed #.

Also, I removed the VCG on the new engine the other day (cf. picture) and in the middle of removing the old engine as we speak.



The annoying E10, E12, and E14 torx bolts were indeed a pain to remove from the tranny, but it was possible to remove the hardest from the top of the car. One of the bolts (E14) however broke upon removal :'(

It's still fun though :)
 

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Older than old school
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The annoying E10, E12, and E14 torx bolts were indeed a pain to remove from the tranny, but it was possible to remove the hardest from the top of the car. One of the bolts (E14) however broke upon removal :'(

It's still fun though :)
It's an adventure, isn't it? By the way, I believe those Torx bolts are intended for one-time use, according to the Bentley manual, and should be replaced
.
 

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Discussion Starter · #10 ·
Thanks for that information.

I think i'll replace them all then :)

Oh and the MAF is not the same, which is another reason why it's necessary to reprogram the DME.
 

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Discussion Starter · #11 ·
Ok I managed to swap the engine successfully :)

It wasn't uneventful:

- I dropped the engine when hoisting it out of the engine bay (the rear hook broke)
- A screw from bellhousing to engine (old) snapped
- A screw from the clutch to flywheel broke (I had to use the old flywheel so it was critical I could reuse it)
- Aligning the transmission to the engine when installing the new was pretty difficult
- Car wouldn't start because a ground wire was loose
- The first flash of the DME failed so the car couldn't start...

Anyway, all in all the most difficult job I've ever done. Had to do it in the driveway hehe.

I'm pretty happy with the result. I've gone from a M52B20 to a M52B25 with upgraded DME (to correct map) and kept my old differential (3.46) so it's one hell of a difference.



 
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