Motronic 1.3 conversion

[Joe Boston]

I was looking at your idle value, see below this engine with Motronic 1.3 he has the tubing going underneath the log manifold.

opposite side.


hope this helps

[PatinaBeforePolish]

Looking good Lock. Curious, does it matter where on the fuel rail the FPR is installed? Yours is after the #1 injector as compared to at the end of the rail.

[Lock]

Thanks everyone, I know this has been done before but it's enjoyable.

Joe you mentioned the e21 intake runners which sounds like you have, I'm guessing they are longer which moves the torque curve down. Have you noticed any tradeoff on the top end?
I was also looking at the Megasquirt, but as I have a background in electronics and I've modified ECUs before I've been looking into the EPROM modifying forums by the e30 guys so I'll keep the Motronic for now. I will probably actually load an M20B25 BIN file into my ECU as that engine is much closer to the M30B28 than the B35 is, and tweak it from there. Plus there's heaps of e30 support still. But in the future I may consider a Megasquirt because as you say, plug and play.
I highly recommend the 528e wiring harness. The e34 535i won't make it past the firewall and it's a complex mess. I was considering mounting a box somewhere, but modifying the 528e is trivial if you can use a soldering iron.
If I take the head off I might put the M30B35 cam in there (assuming it wont' cause interference). Thanks for that photo of the idle speed controller mounted low. I notice that also used the original hose. I'm still playing with locations.

PatinaBeforePolish the location of the FPR on the rail shouldn't normally matter, but I may need to bleed the air bubbles out of the rail initially because the former FPR location was the highest point. I've left enough hose length to wrangle the rail around enough to 'shake' the bubbles out and will run the fuel pump manually the first time I fill it. I considered bleeding the rail via the FPR nut, but spraying fuel at 40PSI sounds like a really bad idea.

[528i-1981]

I think I read that at the fuel rail at 6000 rpm, something like 15 g of fuel per second is consumed, which is less than 20 ml or 2/3 oz. The volume of the whole fuel system from the pump forward is way bigger than that and at 40 psi the delta P should be really small anywhere in the system. Maybe Lock can rig his iPhone to make a video of his pressure gauge at highway speed when he’s finished.

[Lock]

I think I read that at the fuel rail at 6000 rpm, something like 15 g of fuel per second is consumed, which is less than 20 ml or 2/3 oz. The volume of the whole fuel system from the pump forward is way bigger than that and at 40 psi the delta P should be really small anywhere in the system. Maybe Lock can rig his iPhone to make a video of his pressure gauge at highway speed when he’s finished.

I was actually considering this during my earlier troubleshooting with the L-Jet! I had the hood open and watched the gauge from the drivers seat while revving and light loading (one of the benefits of the clamshell) but needed real-world data. I was almost at the point of installing a GoPro or something to record it until Mike suggested just hard-wiring the fuel pump to the battery and I determined I likely had a faulty ECU.
If I get one, at some point I'll place it in the engine bay, could make for some good visuals.

[Joe Boston]

Thanks everyone, I know this has been done before but it's enjoyable.

Joe you mentioned the e21 intake runners which sounds like you have, I'm guessing they are longer which moves the torque curve down. Have you noticed any tradeoff on the top end?
I was also looking at the Megasquirt, but as I have a background in electronics and I've modified ECUs before I've been looking into the EPROM modifying forums by the e30 guys so I'll keep the Motronic for now. I will probably actually load an M20B25 BIN file into my ECU as that engine is much closer to the M30B28 than the B35 is, and tweak it from there. Plus there's heaps of e30 support still. But in the future I may consider a Megasquirt because as you say, plug and play.
I highly recommend the 528e wiring harness. The e34 535i won't make it past the firewall and it's a complex mess. I was considering mounting a box somewhere, but modifying the 528e is trivial if you can use a soldering iron.
If I take the head off I might put the M30B35 cam in there (assuming it wont' cause interference). Thanks for that photo of the idle speed controller mounted low. I notice that also used the original hose. I'm still playing with locations.

PatinaBeforePolish the location of the FPR on the rail shouldn't normally matter, but I may need to bleed the air bubbles out of the rail initially because the former FPR location was the highest point. I've left enough hose length to wrangle the rail around enough to 'shake' the bubbles out and will run the fuel pump manually the first time I fill it. I considered bleeding the rail via the FPR nut, but spraying fuel at 40PSI sounds like a really bad idea.

I do have E21 runner and they are longer by 1 1/4, but are an exact fit to the manifold log and intake manifold, only difference is they have threaded studs on the side part of the runner rather than the front so you would have the make an adapter bracket to affix the FPR and wiring harness.
it is more responsive on the high end, I have a WOT problem, that every time the throttle closes the
second micro switch my engine bogs down, or has big hesitation. that another reason why i am installing megasquirt with 3.5L engine.
on ebay there is a set of 4 you would need two more..
https://www.ebay.com/sch/i.html?_from=R ... s&_sacat=0

[528i-1981]

It looks like the pictures Joe posted feature the E21 runners with an elegant bracket for the FPR.

[Lock]

It looks like the pictures Joe posted feature the E21 runners with an elegant bracket for the FPR.

I was going to say I cleaned my engine a little while it was apart, but that one looks amazing and show-worthy. I'm just bashing things into shape with a rock over here by comparison.

Currently I'm working on wire routing, cutting, splicing and soldering. Won't tape up until everything is located correctly.

Also have solved the steel heater pipe issue - may make a separate post just for that so it's easy for folks to find later, because there are two options and part numbers depending if you keep the "Jules Verne device"/water controlled idle speed valve which was eliminated after the e12, or upgrade to/have the electronic idle valve.

I also ordered a fuel damper because the e34 had one on the pump, and I read that they can help smooth the fuel pulses in the rail to the injectors, which will produce more consistent fuel metering.

My camera isn't currently working, will figure it out later and post progress.

[Lock]

I'll jump straight to it - It lives! A video:

https://www.flickr.com/photos/87580745@N02/48939571558/

And another. that's not a stumble - I gave it a bit, and then a bit more

https://www.flickr.com/photos/87580745@N02/48939671698/

Life got in the way this month, but last weekend I spend most of the weekend on it, and by Sunday afternoon it started. I had everything reassembled and filled with coolant by Sunday morning, but it wouldn't start. Everything was connected, but I noticed there wasn't any particular "ignition on" signal. Researched it - turns out there's a single green wire on the C103 connector in the glove box that gets ignition signal. After checking it wouldn't blow anything up, connected it, and it started.

The wiring is not yet taped up, the diagnostic connector isn't finalized, and it's still in "just started" mode so I didn't drive it further than my driveway, but besides a slight stumble off idle it runs much, much better than I imagined. Works just fine with the original distributor handling rotor duties only.

Ironically the reman e34 starter motor failed later in the day so I can't start it right now, just clicks and does nothing, brushes? It did a lot of start attempts and I guess it was on its last legs. However, the e12 has a very distinct/unique chirping starter sound, you can tell an e12/e24 from a mile away, and this one sounds like a 90s 4cyl Chrysler so I'm not sold on it.
Unfortunately the original fat starter is a hassle to bolt up. I'll deal with that later.

Not too much to say about wiring and reassembly, so I'll post pictures.

The troublesome C103 connector. The red wire is temporary battery positive. The thick green wire is + from the coil, which will supply ignition signal and has since been permanently connected. The black wire also connects up directly to the e12 tach.



Start of wiring



Middle



End



Other side wiring



Finished

[Joe Boston]

Nice Job Lock!!!.. my hats off to you..your engine sound so responsive..
your idle sounds smoother..

Q. did you use a E34 relay holder near the coolant tank?

thanks for sharing your progress.

[528i-1981]

Sounds and looks great. Thanks for taking the time to make these (and other) posts, too. I've learned so much, it was like an online adult-ed class on E12s. -E

[Lock]

Thanks! I'm pretty happy. I'm having fun with this car and it's good to share with people who understand the car and the passion. I'll see if this starter can be repaired, or just put the old one back. Then tidy up the wiring, and it will be ready for daily duties again despite winter. I'll also look into modifying the programming, I'm going to see if the M20B25 fuel injection/spark map is a better fit for this engine, as there's plenty of aftermarket programming support for it with the e30 crowd.

And Joe - good catch, yes it is an e34 relay holder, it worked out really well there. It solved the problem of how to mount the fuel pump, O2 and main relays because there isn't really room for a relay box, and that's where the combo relay used to live.

[tschultz]

Great work on this.

I also cut the AC bracket when I fit M1.3 onto the '81 635 I had.