'84 Eta Crank Trigger

[flumph]

So now that I've got everything pretty much refreshed and working, I'm starting the process of some mild performance mods. My first step is MS3 for both control, data feedback, and refreshing a 34 year old wiring harness.

My car being an early Eta though, the crank trigger wheel is inside the bell housing, and it apparently has an arrangement of teeth that isn't compatible with MS. I've acquired a crank trigger wheel, crank pulley, VR sensor, and sensor bracket off of an '89 325i.

I have two questions.

-Is there a smart way to mount the sensor bracket onto my block? I don't see the two holes that were there from the later block in my engine. Would epoxying/JBing it in place be a horrible idea?

-Should there be a difference in offset between the crank pulley that I have and the crank pulley that's on the early engine? Am I going to need to shim the PS pump, alternator, and fan pulley forward to account for the thickness of the trigger wheel? If so, can I instead use studs here and mount the trigger wheel forward of the pulley, and then rig my own sensor bracket? I have limited but still non-zero fabrication capabilities.

I didn't know whether to put this on the M20 board or on General Technical. Any advice is appreciated! This will be, by far, the biggest thing I've attempted in working on cars. I'm excited and a little nervous.

[jeffnhiscars]

The 2 mounting holes for the CPS bracket are on my 87 eta on thje front face of the block. Hopefully your 84 has them as well.

The pulleys should swap without any adjustments for belt alignment

[AndrewBird]

JB weld will not hold in an application like this. You would be better off drilling and tapping a few holes if the factory ones are not there.

[flumph]

I'll look again. The holes might just be full of road goo. This also says that it just bolts right up. Maybe I just need to pull out my radiator so I can see it better.

Good to know about the belt alignment! I'm trying to plan everything out as well as I possibly can before I start pulling stuff apart.

For reference, I'll try to chronicle MSing an early Eta engine in this thread for anyone who might try it in the future.

[flumph]

Update:
The holes are there on the block and the bracket fits. RealOEM also says that the crank timing pulley has the relevant index pin for the trigger wheel.

Bad news: My fan clutch is stuck so I can't get the balancer off to put the trigger wheel on.
Good news: Autozone sells a euro fan clutch wrench set that has a pulley holder.
Bad news: it's 26 degrees outside.
Good news: I found my soldering iron.

[jeffnhiscars]

The fan clutch has reverse threads :)

[flumph]

I got it on! The sensor bracket fits right up. Chased the threads in the block with a tap because they were pretty crusty (like super crusty). The balancer/trigger wheel fit right up to the crank, and I hit all the bolts with a torque wrench.

There's a problem though and I don't know what to do. My alternator is no longer charging because the belt is slipping. The tensioner is maxed out. I'm going to guess that later cars (wheel came off an 89) had a smaller diameter pulley for the fan/water/alt on the wheel that I changed out. Perhaps either the bracket design was revised in later cars, or later alternator pulleys were also correspondingly larger. Definitely wish that I had checked that before I bolted everything back up. I did check that the PS/AC pulleys were the same.

So, what would you guys do? Smaller belt, try to find a later pulley, or do we know that the tensioner bracket is longer in later cars?

I could have sworn I had a spare alternator from a late car kicking around but I can't seem to find it anywhere...

[jeffnhiscars]

Buy a shorter belt and move on

[flumph]

The belt that's slipping is a 10x965.

The power steering belt is 10x820.

Think it'll fit? I don't really want to wait until next week for a 10x920 belt to ship. I would go out and check but I've already started drinking.

[flumph]

Update:
10x920 was way too small. 3 trips to Autozone later, a 10x950 (their part number 15375) belt is tight enough to push 13.9V at the battery, but the tensioner is still maxed out. Going to try to find a 10x940 (their part number 15370).

I also noticed something. Before I switched the wheels, their was a pretty pronounced vibration coming from the engine bay any time I got above about 2500 RPM in 3rd gear and on the throttle. With the new wheel, that vibration is like 95% gone. It's still there but it's very, very faint.

Did I have a bad harmonic balancer?

[flumph]

Necro update! For the record, the belt problem has been solved and I've been driving around on it for a few weeks since my last post.

Since my last post, I've also decided to:

• Swap in the whole intake from a B25, including throttle body. This also lets me use the intake boot from a B25, which has a very convenient place for the new IAT sensor.
• Fuel rail with FPR and supply line on the same side
• 19 pound injectors from a junkyard M62 (wrecked car)
• Use a 3-pin idle air control valve, since the 2-wire ones can be so finnicky in my experience

Doing this gave me the chance to build everything up off of the car before I started taking stuff apart. I hope I don't regret this decision, but it seems other people have had good luck with this swap.

After I built up all of the parts I need and played with MS/TS enough, I finally decided to pull out the factory engine harness tonight. I managed to do it without breaking anything. I suspect that this harness was swapped in some time in the late 90's or that this car sat for a very long time, because there's no way this harness has had 34 years of use. It definitely had some rough spots though, and it was only going to be a matter of time until it needed to be replaced anyway.

Tomorrow, I'm going to pull off the factory intake manifold and wire the alternator and starter back in. After that, it's time to begin making the new engine harness, install the ECU, test and calibrate, and turn the key. Then the fun really begins :devil:.

[ForcedFirebird]

You had two issues.

1. The 325i has a larger diameter water pump pulley to slow the pump at high rpm
2. The eta has a small diameter wp pulley to speed it up (it only had a 5k rev limiter)

lol.

So you have an early 325e and are attempting to MS it? Be aware if that engine sees much over 5500 rpm, you will float valves, and that configuration is not overly well documented. Most people use the 325i harnesses (and what the MS PNP's plug into).

[flumph]

That makes sense about the pulleys. So when I go in to swap heads, I should buy a 325i water pump so I can use standard belts. Does the same thing go for the alternator? Might end up having to find a bigger alt pulley too.

I thought about using a PNP, but these early harnesses are super weird. A few of the connectors were pretty much completely shattered too, so I decided I'd rather just make my own.

This just occurred to me though: these cars have fixed distributors. I'm going to convert to coil on plug later, but for now, does a fixed distributor mean that I have to run fixed spark timing in MS? What value should I use for this, if this is the case? The base map I found has like 38 degrees up around redline, which would mean that the rotor would be pretty much dead in the middle between two cap contacts. That clearly won't work for a variety of reasons. For now I'll set it at 15 degrees fixed timing, and then maybe play with it once I have COP figured out. Should that work?

Stuff like that is why I'm taking my time with this. I know that I don't know what I'm doing, and I really don't want to be a contributing force to the increasing scarcity of the M20. I'm mainly doing all of this because I'm just bored. Not really chasing power. Just needed something to do.

Also yes, for now, I have the rev limiter set to 5200. I don't trust these old springs.

[ForcedFirebird]

It's not the fact the springs are old, it's that they don't have the inner helper springs. The 325i variants have dual valve springs.

The distributor on an m20 isn't a typical "distributor" in a mechanical sense. It has a broad rotor cap that will fire ECU-dependent, not based on a mechanical advance. The ECU will ground the coil for a fire based on computations and crank angle, with a broad window (something like 50° or more). It's actually a decent system and I haven't discovered any issues with as much as 400whp with a smaller frame turbo on an m20. With larger turbos and/or high hp levels, you will get spark blow out. Most convert to a simple 3 driver ignition and use the GM wasted spark coil packs. They provide plenty of fire, are cheap and only require 3 ignition drivers on a 6cyl.

I really need to find the video, but took one of an MS-powered m20 with wasted spark in test mode. The arcs were literally jumping 2-3" and bright orange/white. Got shocked by a pair once when reaching in to seat a plug wire. Felt like someone mashed my hand with a sledge hammer.

[flumph]

High voltage scares the crap out of me! I've played around with COP coil packs and a MOSFET, and even those have a high NOPE factor for me. These big canister coils must be super nasty.

So what you're saying is that you can still (theoretically) run 25 degrees of spark advance, and the plug still fires? So if cylinder 2 is on the compression stroke and the ECU fires the coil 35 degrees advanced, would cylinder 6 spark instead?? I guess it wouldn't matter because in every case, the previous contact would always be on the power stroke. Worst case, you just spark a cylinder full of burning gas and miss on your next ignition event.

The point is, I can still run spark tables, but keep it under 25 degrees. Yes?

Edit: I know wasted spark is probably way easier, but I scored a set of Bremis at the junkyard and I want the WTF factor of seeing 6 fat coils and no AFM at BMW meets.