GlenL

Dan,

No. That's what the WOT switch does for you.

Mark,

Did you chip it?

All,

Check out www.frwilk.com as he describes how the controller sets the fuel flow rate very well. DME => L-jet.

toofast928

According to that Motronic 944 site :
"Any change in load or engine rpm, the DME must go to the fuel map to get its initial value. Then the fine tuning begins. The Lambda sensor subroutines take charge and the fuel is continuously toggled back and forth. If the Lambda sensor is disconnected, the Motronic gets it fuel levels from the map only. It never just "goes rich to protect the engine" which is another famous and incorrect saying. When the Lambda is disconnected, it uses the fuel map."

Ussally after 2500 RPM the o2 signal is ignored. So after the AFM is at full swing the controller follows a MAP. Enriching the fuel pulse 15% if the WOT is activated.
So do I have this right? Ex. 4000 RPM throttle open 30-80% manifold vaccum 12hg, the inector pulse is 68% (controller following the MAP). If the WOT is activated then enrichment of injector pulse 80% duty cycle.

toofast928

So a AFM to MAF conversion would mean a piggyback box to convert the signal voltage from the (MAF .9 mv - 5.0v to the Motronic 3.5 to 8v) AND to have the MAF sensor calibrated to max voltage at same air flow rate that maxes out the AFM.

In other words the MAF has to show 5v at apprx 3000 RPM so the Motronic fuel MAP engages.

PorKen

This is what I've considered getting, if not a Megasquirt system: PSC1-009 from Spit Second



It's what Kuhn uses in his twin-turbo setup.
...

Here's a thread about an Aussie cheapie, that looks OK: A little something for all the boostards (dirt cheap "fuel management")
...

Then theres SMT-6 as well.

John Speake

Are you sure DME -> L-jet ?

The Motronic DME is a uC type fuel injection controller.with maps The L-Jet is not, to the best of my knowledge, and the book I have in front of me...

The DSM mentioned by Rich is part of the L-Jet controller. Motronic doesn't have one because pulse widths are calcualted by the uC.

mark kibort

Its not so much the rpm, but the WOT as two things happen, first, open loop (o2 ignored) and map used as well as flap position rheostat varying voltage. voltage range is different for the Ljet on 928s vs the 944s. ours is 4.5 v to 9volt at max flap opening. its also not linear.

I tried a conversion and the problem was the voltage. probably not a huge problem, but so far, no one has done a conversion box. Huntley racing made me a tube so i could use the stock "U" leading to the throttle body and a euro intake filter housing bottom. It fit perfect, but the system didnt work at all do to the voltage issues. I still have this tube and the euro MAF style filter box bottom if anyone is doing a conversion. Its one of the parts i didnt sent back for credit.

Mk

mark kibort

this is the system. IT DIDNT WORK for a Ljet conversion !

MK

PorKen

Mark,

Was the setup you tried the computer programmable type, or the box with *****?

GlenL

Well, that's what I was told. No uC in the L-jet box? Then they're not. Poked around a bit on the web and you're right. Jettison the info I've posted.

toofast928

Ok so back to the orginal Q. How does L Jet compute pulse width after the AFM has become maxed.

It does not follow a MAP, (analog CPU). It does not have a TPS signal except for idle position (fuel cut) and WOT (ignore 02).

To accomplish this at least two inputs are needed. RPM we know. Could o2 be the other? Has anyone deleated the o2 on the L jet? When I added the supercharger to the 16v. The L Jet compensated for the more air. 3 psi at 3000 RPM, 4 PSI at 4000 RPM, 5 PSI at 5000 RPM. So 02 must be a major input and not a modifier.....................

toofast928

PorKen I what to do the same conversion and Split Second seems to have it figured out. You know you also need the R4 software. -$800.00

Cheap considering the Megasquirt is apprx $5000

sublimate

Megasquirts are only a couple hundred bucks - even cheaper if you build it yourself.

Maybe you're thinking of MoTeC?

Rich9928p

The important inputs are
- RPM
- Throttle position switch
- AFM
- Engine temperature

The attached diagram provides an idea how each stage of the L-Jet works.

944CS

when the sensor is maxed out, but the throttle is not wide open, the control unit then determines the flow rate based on inputs from the engine speed sensor, engine temp sensor, air temp sensor, battery voltage, and O2 sensor.

toofast928

The Bosch L Jet book states the fuel curve is "programed". So I guess high speed enrichment is not a MAP but a linear program (based on RPM) that is modified by 02, and air temp. make sense?