Some L-Jetronic reading material for today

[84driver]

• Bosch L-Jetronic Injection Manual (& Theory) (PDF, 6.1MB)
• Metric Mechanic has interesting comments about L-Jet tuning
• Larger AFM, VW Golf Mk3 injectors, and sarcasm (In my L-Jet reading I see that the AFM is a bottleneck on many L-Jet cars and a common upgrade. Would still like to find a way to enlarge the inlet. Also, 19# injectors are a drop-in upgrade for M10? L-Jet reading says that Lambda (O2) sensor readings can adjust to a point. Don't think it has any long-term memory like Motronic just a short-term closed-loop adjustment.)
• L-Jet adjustable variables
• Modifying the L-Jet redline by adding a resistor to the ECU
• Barry Burrs L-Jetronic Tuning Guide
• Info on L-Jetronic Tester

Also this photo titled 'idle problem fixed' made me lol:

(From BFC)

[84driver]

A little more from the $500 M10 turbo thread on BFC:

Turbo: KKK K03
Intercooler: Blackstone unit from a Saab 900t
Injectors: Ford Motorsport 24#
Diverter Valve: Bosch unit from a Porsche 944t
Boost Controller: manual adjustment from PTI, mounted on wastegate actuator bracket
Exhaust Manifold Adapter: custom fab from Porsche 944 S2 exhaust

Interesting post, can you elaborate a bit on the tuning aspect?

A/F is getting taken care of with a simple retune of the stock Jetronic system (AFM spring adjustment and idle screw adjustment) with Ford Motorsport 24# injectors. The ignition timing is no longer using the vacuum advance diaphram and will be retarded 5 degrees for it's initial runs, and adjusted from there if need be. I rigged up a basically free A/F ratio meter using the stock O2 sensor to see where it stands each time I adjust the fuel, and it will have a wideband confirmation on the dyno.

...

I actually got a set of NGKs that were meant for an '85 Audi 5000S Turbo. It's the NGK version of the Bosch W7DTC. I think the NGK part number is BP6ET.

...

Although for max horsepower L-Jet is limited and it's easy to give up and just use MS or another engine management system, there are many inexpensive ways to mod an M10. Most posts say 'swap durrr' or 'go full custom turbo' or 'go carburetor' or other expensive/complicated mods. Therefore I've decided to collect solid M10 tuning tips here in this thread. Feel free to add.



EDIT:
Post from the same guy has example of AFM failing. Good to read as I am diagnosing a similar issue.

EDIT2:
And here is my diagnosis http://www.r3vlimited.com/board/showthread.php?t=227156

[Mr Mpower]

i have a k-jetronic m10 if you find some some tuning tips or a way to upgrade it,i'll be thankfull

[Hey_You]

k-jet, as in CIS system?

[Mr Mpower]

k-jet, as in CIS system?

Yes,Bosch CIS K jet

[84driver]

No offense, but would prefer to keep this an L-Jet thread.

Here's a good overview slideshow PDF I just ran across, based on the L-Jet BMW E12:

http://www.firstfives.org/faq/ljet/jetronic.pdf

[Holland]

Subscribed.

[84driver]

Here is an Fiat with custom turbo running L-Jet with a couple tricks:

http://web.archive.org/web/20090609071103/http://users.chartertn.net/jseabolt/80spider.htm

Here is a thread with more detail about the build:

http://www.diy-efi.org/pipermail/diy_efi/2005-June/000755.html

It ran for years!

Great L-Jet thread with lots of L-Jet tuning and tricks:
"L-Jet how much boost can the stock system take?"

http://www.turbo124.com/forum/viewtopic.php?f=2&t=98&start=0

A modern guide to L-Jet written in 2004:

http://www.mirafiori.com/faq/fiatFI_may2002.pdf

Interesting L-Jet tuning tips from a post on Pelican:

I loosen tension on the barn door spring in the AFM so it opens easier and farther so the motor breathes easier and injector dwell time is increased for any given rpm and then compensate for the barn door opening farther at idle and being too rich by opening up the CO air bypass screw in the AFM so the barn door closes up and the AFR is correct at idle.
Then install an adjustable rising rate wide band fuel pressure regulator on the end of the fuel rail so you can have higher fuel pressure under acceleration and zero manifold vacuum.
You can also take the stock fuel pressure regulator and take 2 sockets of the right size and squeeze the ends of the metal housing together a little bit in a vise. That increases the spring pressure inside the FPR and raises the fuel pressure, but an aftermarket adjustable vaccum controlled rising rate FPR is wayyyy better.

Along with that I install a 10,000 ohm linear taper potentiometer in series with the engine temp sending unit so you can add resistance to the sensors reading and make the ECU think it's colder out than it is up to 30 below zero so injector dwell time is increased for alot more fuel with the turn of a knob on the dashboard.

http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/523350-motronics-turbo-conversion-thoughts.html#post5147949

[84driver]

Found this gem today:

I asked essentially the same question on the yahoo groups m10 -318i board and here's the answer I got. In short, don't do it looking for an easy fix!

Anyone working on a 24 year old E30 fuel injection system needs the Robert Bentley E30 Repair manual and RB’s Bosch Fuel Injection manual from the same era – plus a digital multi-meter. The manuals and multi-meter as good as a BMW shop fault computer.

Have the engine compartment thoroughly cleaned with water/steam (wrap any electronics to prevent water contamination) to eliminate any dirt that might be interfering with things. Dirt/oil/grease will seal air leaks or interfere with electrical operations one day, allow them the next.

To ensure dependability on a 24 year old fuel injection system, replace ALL rubber hoses and ALL gaskets wherever unmetered air can leak into the motor on the motor side of the air flow meter, or independent of it. And not just for the air/fuel systems. Replace the brake booster hose, all the oil hoses. Remove and throw away those ANCO hose clamps that have accumulated over the years and put real BMW ones on – properly sized against the BMW parts manual – instead. A new ring seal on the oil filler cap and a new valve cover seal aren’t utterly necessary on the M10 motor, but you’ll feel better in the morning after you’ve done that. Don’t overlook the distributor shaft seal. With the motor at operating temperature, station 2 friends with fire extinguishers on each side of the engine compartment and you squirt a little starter fluid around the intake manifold gaskets. Any change to engine idle or running characteristics noted as the stuff evaporates signals an air leak there.

The rubber hose FROM the air flow meter to the throttle body cracks on the bottom and around the clamps over the years. If yours is 24 years old, throw it away and invest in a new one. You might not even see the crack that’s letting in air. Make sure the clamps are BMW-authentic, too.

Invest in new fuel line hoses as well. If you can smell gas in the engine compartment, one is cracked somewhere. Old BMW fuel hoses are a fire hazard.

Once you have an absolutely airtight motor, you have eliminated about 20-30% of your potential intermittent drivability problems on the E30 M10 EFI system. Move on to the electrical stuff.

24 year old BMW wiring harnesses have been hammered all those years by heat, vibration and corrosion.

Before doing any of the following electrical system work, disconnect the negative side of the battery.

Check every wire that has anything to do with the fuel injection system or drivability for continuity. Flex the wiring while putting the multi-meter on them. Frequently, an older BMW wiring harness wire will crack inside its insulation and continue to pass current part of the time, and not at other times. The wiring to the oxygen sensor is a frequent culprit. Any soldered connection is suspect on a 24 year old BMW E30. The solder cracks and you’ll never see the defect by eye. If you are good at it, re-solder all connections you can reach yourself, or ask a friend to do it. Pull the circuit board out of the instrument cluster and take it to a professional electronics repair shop. Have every soldered joint redone on the circuit board as well. They frequently cause problems with invisible cracks after all the years. (You can have the shop rig a snap in/snap out holder for the NICAD batteries while it is at it. Never have to fuss with re-soldering the batteries while replacing them again.)

Thoroughly clean every wiring connector with a brass brush and connector cleaning solvent. Dremel Tools are wonderful for the hard to get at places. Test the connectors on the multi-meter. Make sure the connection is tight and the plastic and metal components aren’t broken or missing. Eliminate any corrosion damage that you can see. Splice in new connectors if any appear defective. Wires fatigue at connectors quite often. Pull the fuse box and completely clean all the connectors in and around that, too. Chances are you’ll break some because they are corroded. Replace. Re-solder. Lots of older BMWs have cracked or crumbling rubber boots that no longer protect connectors. Replace them if that’s the case.

Using your RB Service Manual’s electrical wiring diagram, find every ground point on the motor’s wiring harness, including the main ground on the intake side of the motor. Clean all mating surfaces to bright metal with a brass brush and emery cloth, then re-connect and protect with suitable dielectric or other compound, if you live close to the ocean or in a really wet climate (you said Seattle??). Don’t forget to get into the computer compartment under the glove box and clean all connectors to the car’s brains. Be very careful to disconnect power to the battery and ground yourself before touching the computer, however.

Don’t forget to check your distributor. A worn distributor causes considerable erratic motor operation, including bad idle. Have it bench tested by someone not interested in selling you a new distributor.

The E30’s EFI sensors are pretty simple to check, though not prone to defects. With the RB and Bosch manuals, you can check sensor resistance against given values. Throw away the components that you don’t like.

Once you have addressed your air and electrical gremlins, you have eliminated at least 75% of the E30 M10 EFI system problems. If there are still problems, your RB Manual and Bosch Fuel Injection guide can help you work through them.

Good luck! Enjoy!

[packratbimmer]

That is the spirit 84driver! Great research. A properly tuned 1984-85 M10 can be amazing to drive due to the light weight and weight distribution. Back in the day, I always just tuned for high speed and did not worry too much about in-town drive-ability.

BTW: I had a Baltic Blau 1984 EURO from about 2001-2006 - love that color!!!