Converting BMW 2.8L M30 L-Jetronic to VEMS: Some questions ...

[SamSpade]

Hello everyone.

I'm looking at buying and restoring a 1986 BMW 728i (E23) with a 2.8L M30 L-Jetronic engine:




I'm quite handy at engines and electronics, being an electrical engineer by education.  I almost always DIY my 2004 BMW 325i and am very comfortable even with its much more complex Siemens MS43 ECU.  I have a few Innovate gadgets on the 3-series (2 LC-1s, DL-32, 2 SSI-4) where I tapped signals directly on the ECU.

Having fallen for these cars and their engines, I've been looking the past months for a project car to restore.  I've narrowed my choice to an E23 (1977-1986 7-series), E24 (1977-1989 6-series), or E28 (1981-1988 5-series).  The 6-cylinder M30 engines on these cars are bulletproof and easy to maintain.

As you can see from the photo above, the L-Jetronic is fuel-only control and spark timing is still handled by a vacuum-enabled distributor.

I was looking at MegaSquirt when I stumbled upon VEMS and was impressed by its capabilities.

Now some questions:
1) Can VEMS do multi-bank adaptive fuel trims (closed-loop UEGO control)?
I understand VEMS has a built-in LSU4 WBO2 controller but it's only for one O2 sensor.  If I install Innovate LC-1's on each bank (cyl 1-3, cyl 4-6), what are the VEMS options for closed-loop fuel trim control?  Or is it not possible at the moment?

2) Can VEMS do multi-spark firing?
Multi-spark ignition is supposed to improve clean burning and efficiency especially at idle.  It's not a deal-breaker, but it would be nice to have.  Here's a snapshot from the secondary circuit of my M54 325i during idle where you can see the multiple firings:


3) What other caveats should I know before embarking on the L-Jetronic to VEMS conversion?

Thanks all!

[rob@vems.co.uk]

Hi mate, interesting project, there are a few M30's running on VEMS, heres a nice one with a turbo:
http://www.vems.hu/wiki/index.php?page=MembersPage/GergelyLezsak/BigSixTurbo

I'll answer your questions by number:

1) Currently there is no injector trim in the released firmware, but the version currently in test has individual injector trim, but this will not be individually loop-back controlled.  You could tune the engine with the lambda in the standard place, then tap a bung in each bank, and adjust the trim.  And while I'm sure the LC-1 is a good system wouldn't you be better off with a VEMS Wideband and EGT gauge?

2) No multiple spark option I'm afraid.

3) God alone knows , there's some information on the wiki, often confusing and contradictory, theres a lot of good people on here though.

[gunni]

As I have some experience with these engines.

Your best way is to find a later m30 motronic timing wheel to fit on the front, as well as the crank sensor and it´s shielded wiring.
these parts are (sensor bracket, sensor, e34 or e32 wiring loom)


I would actually go so far and say that you should get a 3.5 from a e34 or e32, they are cheap and fit straight, if you get a engine ´87 it will have both mounting positions ( e23, e28, e24 vs. E32, E34 ), it´s a better engine in all respects then the 2.8.
and will have almost all the sensors and wiring you need.

as for #1. I can´t see a need for individual bank adjustments as you wouldn´t run banked injection any more.
but 6 sequential injectors. And if you are running the stock injectors the resolution is going to be plenty for accurate adjustments,
I have perfect idle with 42lb injectors on my 2.5 where the stock is 14lb.

[SamSpade]

Rob and gunni, thanks for the quick replies.

... 1) Currently there is no injector trim in the released firmware, but the version currently in test has individual injector trim, but this will not be individually loop-back controlled ...

First off, great work Rob!

I guess I misread the "Configurable closed loop UEGO" in the VEMS spec sheet.  I thought it was for adaptive long term fuel trims like in the modern ECUs.  I suppose "closed loop" here means pump current PID control and heater control of the wideband O2 sensor itself.

Come to think of it, once the wideband sensors and AFR gauges are installed, I don't think I'll need the adaptive fuel trim capabilities. Manual AFR tuning is more impressive anyway.

2) No multiple spark option I'm afraid.

Something to think about in your next release.  Should be easy enough for you guys to include. 
I can imagine it now ... how the configuration dialog would look like:

• [Y] Enable multi-spark ignition
• [1500] Maximum RPM for multi-spark
• [7] Number of sparks per ignition event
• [300] Spark duration (in usecs, except for last spark)
• [900] Multi-spark intervals (in usecs)

I would actually go so far and say that you should get a 3.5 from a e34 or e32, they are cheap and fit straight, if you get a engine ´87 it will have both mounting positions ( e23, e28, e24 vs. E32, E34 ), it´s a better engine in all respects then the 2.8.
and will have almost all the sensors and wiring you need.

Yeah I was actually looking for a late model 3.5L M30 engine.  I'm based in the Philippines.  Unfortunately the local junk yard is selling the 3430cc engine for an arm and a leg.  I guess I'll have to search some more.

Although I wouldn't mind working on the 2.8L and fabricate some brackets and a camshaft timing wheel.  The crankshaft 60-2 timing wheel would be easy enough to get.  I'm also planning to replace the whole wiring harness so might as well put in Hall effect sensors instead of the stock VRs.

Also planning to convert to coil-on-plug. It's more reliable and even might be cheaper in the long run since I don't have to replace the Motronic's (in case I get the 3.5L) old rotors, cap and spark plug wires.  I'm an electrical engineer, the less moving parts there are, the easier for me to understand.   

as for #1. I can´t see a need for individual bank adjustments as you wouldn´t run banked injection any more.
but 6 sequential injectors. And if you are running the stock injectors the resolution is going to be plenty for accurate adjustments,

Yes, I was thinking sequential injection but with banked adaptive fuel trim adjustments like in the modern engines, not actual banked injection.  As you know the M30 exhausts are in groups of 3.  I would have wanted to put wideband O2 sensors in each exhaust manifold and let VEMS perform adaptive fuel trim adjustments per bank.  But like I said earlier, manual trimming is cool.

I have perfect idle with 42lb injectors on my 2.5 where the stock is 14lb.

Wow! I guess you're running a mean turbo. 300rwhp perhaps?   Which injectors are you using, and are they peak-hold or high-impedance?  I'm very impressed they're stable at idle.   How many ms are those 42lbs injectors open at idle?

[gunni]

There is closed loop ego control, but it adjusts all the injectors as is normal for ALOT of stock ecu´s.

Multiple spark isn´t all what they say, it´s more of an emissions thing then anything else. you can always just tune to leaner mixtures and still run fine.

I´d just go for wasted spark instead of cop´s, now that is easier still

to me manual trimming is not cool tbh, I´ll just have the ecu working thousands of times a second to keep the mixture where I told the ecu to be, it will do that under all conditions and makes it a non concern after the engine is up to temps. Doing a couple of logs and let the megalogviewer VE analyzer review will keep lambda at exactly where it is supposed to be.

they show about 1.9ms at idle. And it´s because of the vems´s injector control they can be run like that,
some people are running more then 1000cc´s on E85 and 4cylenders, it´s that good. My injectors are high impedance.

it´s going to be 400hp turbo 325i E30.

Using Vems I´m able to not have any extra wideband, egt or any logging stuff.
it and everything the vems is doing get´s logged for review.

[SamSpade]

Thanks gunni for the informative replies! I'm sold!!

I misread Rob's reply -- so there IS fuel trim control! Great!  But since VEMS only has one WBO2 input I can only read one bank (e.g. 3 cylinders), right?  Shouldn't really matter that much since if correctly tuned with matched injectors both LTFT's should be within 1% of each other anyway.

So the wasted spark method would mean I don't need a camshaft timing wheel, correct?  I was considering coil-on-plug since the coils on my M54 are on a BMW NA recall list (stock Bremi to be replaced by Bosch coils).  They're still ok.  But since I was planning to replace them soon I might as well use them on an M30 VEMS conversion.  Having the coils exposed (albeit above the exhaust manifold shield) should extend their lives a little longer.

400hp!      What's your VEMS member page?

[gunni]

You can also just put the o2 in the exhaust stream in an H pipe or X pipe or in a merge to a single outlet pipe.
besides, there would have to be a pretty big problem is the first bank of cyl´s isn´t almost the same as the later one.

yes the wasted spark means that, but you could run double out (where two ignition drivers are activated at a time) and thus run "fake" wasted spark. and thus use your COP´s, you can also just put small HT leads on the cop´s and run them as 6 coils.

I haven´t finished my setup but
http://www.vems.co.uk/forum/index.php?topic=477.0
today the exhaust fabrication begins.

[SamSpade]

Nice setup! How did that big pit in the head happen?

Also, which TPS (brand, part number, etc.) would you recommend to put in the M20/M30?  Would the Bosch 0 280 122 001 in the VEMS web shop be suitable for the M30?  I suppose it's still best to use the current throttle body but just replace the TPS right? 

Thanks!

[gunni]

yes, you can get a TPS from automatic e34 or E32 m30 based cars,
it has a round connector, it´s variable and a switch like the old ones(yours)

that tps in the webshop will require you to do some minor mods to fit it but nothing major.

A rocker must have broken at one point, that hole errupted when I was taking the cam out, must have released some tension in the head that was keeping it in there.