N52 Swap Discussion

[hoveringuy]

Here's one of the big reasons whey everyone complains about radiator clearance on the N52. This is the coolant bypass hose, it goes from the "mickey" fitting near the regular radiator outflow to the "closed" side of the thermostat. The radiator connects to the "open" side. When the thermostat is cold, the radiator flow is blocked and the only flow is through this hose (and some through the heater core) to keep water circulating through the engine when it's cold. Once the coolant gets hot enough, the thermostat opens and it's a mix of radiator flow and bypass from this hose.

It sticks out so far because it needs to clear the serpentine belt.



I don't have AC, so I don't need the most of the serpentine belt, I'm only driving the alternator and power steering on the drivers side. Since there's a cheaply available aluminum fitting for the water pipe "mickey" (the stock plastic fitting dissolves after XX miles), my task has been to fab an aluminum hardline that could run closer to the block. I've made my second prototype and it checks all the boxes. Next step is to have a number of aluminum tubes bent to reduce it to one weld at the fitting.

Clearance to the radiator is now basically limited to the profile of the cylinder head and the damper pulley. A 50mm radiator should be no problem, let along stock 33mm.


I haven't decided if I want to use the second mounting boss yet. It's where the plastic hose-holder was attached.

[hubcapboy]

Good evening.

I haven't given up.

Yet.

During hoveringuy 's engine assembly he ran into some... unwelcome interference. The pan was designed to run from the flange to clear the windage tray. What I hadn't spotted, because I hadn't turned my engine, is this naughty boy here:



There's a whopping great crank counterweight that swings down into this space several thousand times a minute. Steve made some adjustments to the shape of... one of the components. I lost a small amount of sleep every night for two weeks until just now. After raiding the kids drawers for some playdough, I installed the interference gauge:



After re-installing the pan and snugging enough bolts, I had a good print of the crank:



It clears on mine. Mercifully. Here's a section of the interference gauge:



I'm writing a whole post just on this with big flashy pictures to warn anyone in the future that this is a very critical clearance that I just lucked out on. Just to be safe, I've eased the inside corner of the flange:

[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.

[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.

[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.

[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.

[Trevbot]

Should have just let it clearance itself.

[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...

[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]

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]

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.

[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.

[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]

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.

[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.