N52 Swap Discussion

[hoveringuy]

This is hopefully the last post from me on the belt tensioners.

One niggling issue I had when I installed the N54 tensioner is that the belt doesn't appear centered on the pulley, there's a solid 7mm space between the belt and the end of the pulley that makes it look like the belt isn't centered, and that made me concerned that there was a difference in backspacing between the N54 and the X5 tensioners.



So, I did the rational thing and ordered a genuine X5 tensioner, P/N 11-28-7-565-225. The only differences between the N54 tensioner, P/N 11-28-7-563-927 and the X5 one is that the former comes with a steel bolt and the latter an aluminum bolt. Also, it seems that all instances of N52 tensioners have silver tension springs instead of black. Different steel composition or just paint... I dunno. Otherwise, everything else between them was identical.

E70 X5 on the left and N54 on the right



I also discovered why my belt looked so cattywampus on the N54 tensioner: the pulley is physically thicker. The N54-style tensioner has a 30mm thick pulley whereas the normal N52 one is only 26mm AND any N54 or N52 with that style tensioner has a 7 rib K07 belt instead of a 6 rib K06 belt!

I tried mounting a set of 26mm pulleys on the N54 tensioner but that legitimately screws things up because it changes the pulley centerline.

Notice that the backs of the pulleys are perfectly aligned.



Bottom line.

The N54-style tensioner works just fine. You can either order the cheaper N54 tensioner ($65) and then order the aluminum M11x99 bolt that goes with it separately ($15) or just order the X5 tensioner for around $140.

Sorted.

[Caperix]

The water pump is not anywhere near the tensioner, and it's not connected to the belt either, not sure how it's related if true. But that would be interesting to know, although the N54 pump is plastic and known to crack, so probably not an upgrade though.

Sorry about that, I was not very clear. The larger water pump installs below the compressor so I was thinking that was the reason for moving it, though looking into it deeper, an adapter plate is installed on the pump not the compressor as I had thought. This will not effect using the tensioner for a/c delete but it does mean that the compressor length difference is in the pulley not moving the compressor, so the v12 compressor will still be the best route for and.
While it must flow more I agree that the n54/55 pump would not be a good upgrade due to the common leaks between the plastic & metal parts of the housing, or worse through the connector that can short the dme.

[hoveringuy]

The water pump is not anywhere near the tensioner, and it's not connected to the belt either, not sure how it's related if true. But that would be interesting to know, although the N54 pump is plastic and known to crack, so probably not an upgrade though.

I think the X5 4 zone climate feature has an additional mixing valve that sits behind the AC compressor; compressor needed to be pushed forward to make room.
SInce it no longer aligned with the serpentine they gave it its own belt and used N54 style tensioner for the main belt.
The remaining mystery for me is why N54 and X5 tensioners have different PNs.
I'll have that answer soon.

[hubcapboy]

Caperix was trying to tell us about the 2-belt setup somewhere around page 18 when I was looking at different AC compressors.

I didn’t look into it further because I didn’t want to add a second pulley to the crank, and from what I could tell the m54 compressor would align the pulley with the inner belt (and have the wrong number of grooves) and wouldn’t stick out far enough to catch the outer belt.

We didn’t realize at the time that it would solve the AC delete issue.

[nando]

They use the n54 water pump so that may be what the extra clearance is for. If there is clearance for the 2 row pulley I think a m54 compressor should bolt up for AC swaps as well.

The water pump is not anywhere near the tensioner, and it's not connected to the belt either, not sure how it's related if true. But that would be interesting to know, although the N54 pump is plastic and known to crack, so probably not an upgrade though.

[hubcapboy]

This is the best you can hope for from cleaning up a magnesium valve cover. If this looks like hell after 6 months I can clean up the other one and paint it.

It looks REALLY cool and dark blue when it’s wet, but dries to grey. I can’t find a single reliable resource for a good finish that keeps that dark blue color that doesn’t sound like a commercial process.

[Caperix]

They use the n54 water pump so that may be what the extra clearance is for. If there is clearance for the 2 row pulley I think a m54 compressor should bolt up for AC swaps as well.

[hoveringuy]

E70 x5's with the n52 use a 2 belt setup with a separate belt for the compressor like a m5x engine. That belt & tensioner setup should work as well.

Ooh. Good tip!

I see that the tensioner basically looks the same, but they have an aluminum bolt! I shouldn't have been searching for an M11X100, but an M11X99.

Although they look identical, the X5 tensioner and N54 have different P/N's, and X5 is $150 instead of $60. Wonder what the difference is? I just ordered the bolt.

This is only on X5's with adaptive drive and 4 zone climate, I guess they needed room on the front of the engine for something.

[Caperix]

E70 x5's with the n52 use a 2 belt setup with a separate belt for the compressor like a m5x engine. That belt & tensioner setup should work as well.

[hoveringuy]

Am I going to hell for this?

The two golden rules of the N52 are (1) Don't re-use aluminum bolts and (2) Don't ever, ever, ever use steel bolts in a magnesium block. EVER!

One of my issues with the initial install was that when the AC compressor was removed, the routing of the new belt was less than ideal. It was tensioned in completely the wrong way and the tensioner was actually on the stop at the end of it's stroke. Plus, by tensioning at that angle the belt tension was probably 2 or 3x greater than what it should have been.



The N54, on the other hand, has the turbos where the AC compressor was so they moved the compressor to the other side and re-designed the tensioner to compensate. The N54 shares a lot of similarities to the N52 block but is aluminum.



Would I be able to use the N54 tensioner?

After purchasing some Ebay samples, it seemed plausible. One of the issues is that the N54 uses a steel M10x100mm bolt where the N52 uses an M11 aluminum bolt. Because magnesium, duh...

So after searching for an M11x100 aluminum bolt I discovered that there is no such thing, but BMW does have an M11X100 bolt that was used in the crank of an M60. P/N 11111745108 "collar screw" and as a bonus it's grade 10.9.

Slight downside is that it doesn't have the same shoulder the original bolt has, but the pulley is still aligned on the other end.



As far as corrosion, yeah...

magnesium-steel galvanic corrosion only happens in the presence of an electrolyte, namely water. The mounting boss of the tensioner sticks up and into the back of the tensioner so it's a difficult place for water to get, but I coated the area liberally with marine grade anti-corrosive anti-seize.
I'll look at it in a few years but I don't expect much.



The result is perfect. The tensioner engages the belt in exactly the right manner. I used a Gates K060495 50 1/8" belt and it's a great fit.




As a final note, removing the power steering would be a snap. Belt routing and tensioning would be easy. The only reason I've kept the power steering so far is that with out it the car would be so light it would come off the road. I need the ballast.

So, I'm probably still going to hell, but not for the bolt.

EDIT: Just use the X5 tensioner which comes with an aluminum bolt. See below...

[Trevbot]

Should have just let it clearance itself.

[hubcapboy]

The counterweight comes close to the inside edge of the pan flange and there's some possibility for tolerance stack-up to create interference. I relieved the corner of the counterweight just a hair.

I'm pretty sure it needed that to get into perfect balance, anyway.

That rear fillet piece may have had a slightly shallower angle for me. You're looking at the very back of the engine, transmission is to the right.

I said "AH" component. you weren't supposed to tell people what it was.

[hoveringuy]

The counterweight comes close to the inside edge of the pan flange and there's some possibility for tolerance stack-up to create interference. I relieved the corner of the counterweight just a hair.

I'm pretty sure it needed that to get into perfect balance, anyway.

That rear fillet piece may have had a slightly shallower angle for me. You're looking at the very back of the engine, transmission is to the right.

[nando]

Doesn't look like that big of a deal, but I guess I'll definitely want to check clearances. Probably I'll just mark it with one of my N52 pans and grind that corner off a bit like you did.

I'll have the DMEs flashed and on their way to you guys soon.

[hubcapboy]

My engine was pretty gunky, and hoveringuy 's trial fitment (capable of a not insignificant distance on the freeway to my place) meant that I could abandon my mock-up car. My original plan was to have everything running in the red car (but not driving, because that car was undrivable) before touching mine. I'm days from pulling a well-serviced and reliable m20b27 with a leaky head gasket out of what used to be my daily driver, so to make myself feel better about it I've pulled all the ancillaries off the new motor and scrubbed it until it turned grey:



I've ordered a whole basket of new aluminum bolts to fit everything back on again. A new valve cover gasket kit and oil filter housing gasket will be going on before installation as well.