L-Jetronic with MAF hot wire conversion!
08-05-2003, 01:20 PM
#1
Three Wheelin'
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L-Jetronic with MAF hot wire conversion!
I'm now in the thick of getting the MAF conversion tuned on my car. I started by mapping the AFM and MAF simultaneously while driving the car. I then made a graph showing the two outputs and finally was able to arrive at a correction factor plot to be entered into the PSC from Split Second.
The car started right up and was fully driveable, but there are still glitches in the setup....it is somewhat lumpy right now and I have to make certain I tune it all properly before I really turn the steam up.
It is a long and very tedious process of re-mapping the fuel curve. It sounds simple, but in reality it is quite difficult.
Right now I am working on a straight 1 dimensional correction factor, but I am becoming painfully aware, that I can have a given MAF output voltage at high RPM no boost, or the same MAF output voltage at low RPM with boost. The engine expects two different fuel inputs here, even though it has the same MAF sensor voltage. UGH! It is tricky. Luckily I have a 2d controller....that is smart!
I have been driving around with the laptop, a myriad of wires and a voltage meter connected to the out of the loop O2 sensor. Burning a lot of gas and downloading changes on the side of the highway. I think I can make this thing work...it isa just going to take a lot of time and patience.
It has made a dramatic improvement down low where the throttle response used to be choppy...I now have a more linear throttle curve. If I really screw up the program, I have it wired so I can swithc from MAF to AFM from in side the car. I have never seen so many freakin' wires on the floor of my car before.
So does this make my L-Jet an LH?
The car started right up and was fully driveable, but there are still glitches in the setup....it is somewhat lumpy right now and I have to make certain I tune it all properly before I really turn the steam up.
It is a long and very tedious process of re-mapping the fuel curve. It sounds simple, but in reality it is quite difficult.
Right now I am working on a straight 1 dimensional correction factor, but I am becoming painfully aware, that I can have a given MAF output voltage at high RPM no boost, or the same MAF output voltage at low RPM with boost. The engine expects two different fuel inputs here, even though it has the same MAF sensor voltage. UGH! It is tricky. Luckily I have a 2d controller....that is smart!
I have been driving around with the laptop, a myriad of wires and a voltage meter connected to the out of the loop O2 sensor. Burning a lot of gas and downloading changes on the side of the highway. I think I can make this thing work...it isa just going to take a lot of time and patience.
It has made a dramatic improvement down low where the throttle response used to be choppy...I now have a more linear throttle curve. If I really screw up the program, I have it wired so I can swithc from MAF to AFM from in side the car. I have never seen so many freakin' wires on the floor of my car before.
So does this make my L-Jet an LH?
08-05-2003, 01:35 PM
#2
Rennlist Member
Hi John,
Glad you've made a start. yes you must have a map with rpm, and load inputs.
Have you though t about using a closed loop CO system, which would help the "fine tuning" once you have a reasonable map ? It may be possible to use the O2 signal, with some processing, into your Split Second box.
regards,
Glad you've made a start. yes you must have a map with rpm, and load inputs.
Have you though t about using a closed loop CO system, which would help the "fine tuning" once you have a reasonable map ? It may be possible to use the O2 signal, with some processing, into your Split Second box.
regards,
08-05-2003, 01:55 PM
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Well, I looked at it this way....the AFM has no RPM input for its signal voltage....BUT the MAF is also making compensations for temperature and density where the AFM was less sensitive to these changes. I may just have to hook up the speed wire and tune it that way. Unfortunately, my work has just begun.
As for the O2, right now I am in open loop....once tuning is done I can hookup the O2 just like stock.
As for the O2, right now I am in open loop....once tuning is done I can hookup the O2 just like stock.
08-05-2003, 05:39 PM
#4
Rennlist Member
Hi John,
The basic L jet controller should do what you want, once you've got your AFM to MAF curve, which you've alredy done.
Do you also need to add a variable factor related to boost, or do you think the MAF should manage on it own ?
I agree that all the initial work should be done open loop.
The basic L jet controller should do what you want, once you've got your AFM to MAF curve, which you've alredy done.
Do you also need to add a variable factor related to boost, or do you think the MAF should manage on it own ?
I agree that all the initial work should be done open loop.
08-05-2003, 06:12 PM
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I think I will need to dip into the speed columns on the PSC to get it right. It is a long and tedious process. The MAF is on the intake side of the turbocharger system....my AFM was on the discharge side of the system. Some issues to deal with on this stuff for sure.
The MAF should more closely measure the airflow, but getting it all to work together is the trick.
The MAF should more closely measure the airflow, but getting it all to work together is the trick.
08-06-2003, 01:46 PM
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The cell array goes from 0 volts to 5.2 volts in 0.1 volt increments, while the RPM goes from 500 to 8000 in 500 rpm increments.
So for example, I can map a voltage signal at 3000 RPM differently than the same voltage signal 1500 RPM.
I discovered I can be at 3.4 volts while off boost at about 5000 RPM in 1st, but in 5th gear that same voltage comes in at about 2200 RPM and I have some boost as well.
Looks like about 2% to me....?
So for example, I can map a voltage signal at 3000 RPM differently than the same voltage signal 1500 RPM.
I discovered I can be at 3.4 volts while off boost at about 5000 RPM in 1st, but in 5th gear that same voltage comes in at about 2200 RPM and I have some boost as well.
Looks like about 2% to me....?
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08-06-2003, 04:00 PM
#8
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Hi John,
So was the fuelling incorrect at one of the 3.4v readings ? Or do you need to add a boost aprameter to the map ?
Yes it's 2%, A bit wide, but if you get it near enough and then connect up an O2 loop, that will pull in the correct value
So was the fuelling incorrect at one of the 3.4v readings ? Or do you need to add a boost aprameter to the map ?
Yes it's 2%, A bit wide, but if you get it near enough and then connect up an O2 loop, that will pull in the correct value
08-06-2003, 04:32 PM
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John,
The boost parameter is simply the fact that the car can make the MAF deliver 3.4 volts at only 2200 RPM....so that cell location in the map represents a boosted cell, where 3.4 volts at 6000 rpm is a normally aspirated cell.
I am getting a real appreciation for those gurus who do engine software development for a living.....huge number of variables to take into consideration.
Thank God I can't monkey too much with the ignition curve too much.
The boost parameter is simply the fact that the car can make the MAF deliver 3.4 volts at only 2200 RPM....so that cell location in the map represents a boosted cell, where 3.4 volts at 6000 rpm is a normally aspirated cell.
I am getting a real appreciation for those gurus who do engine software development for a living.....huge number of variables to take into consideration.
Thank God I can't monkey too much with the ignition curve too much.
