Another stupid d-jet question:, Related to a new 2.1 tune: defining terms- what constitutes "part-load vs full-load" and other mysteries Options

[DRPHIL914]

calling all d-jet masters !

OK so yes, ive read Anders etc and maybe missed it along the way, but
how or what constitutes a part-load condition?

I am trying to get my d-jet MPS dialed in on the 2.1 build. and it had been running really well, but just a tad lean still, so after going back and reverifying my timing and other settings, checking plugs aftera 750 mile trip, its really close and realizing i was probably a bit low on the fuel pressure i made that correction and then set out to do some local highway driving to test it out, and really felt good, but maybe a bit rich at low end, idle and what i was thinking would be part-load.

BUT i think i over corrected on the MPS and now i went from being in the 12-12.5 range at idle and also cruising at 3000-3400rpm, i now am running light at about 14 on that mid-range cruising. it is good on WOT so i dont want to mess with that(full load stop) .

i should have left well enough alone because i will probably be a bit heavy at idle and low end with this motor, due to a more performance minded cam profile etc.

point is, what is part-load? if i am reading my AFR meter , lets say at 3000rpm- 3400rpm and cruising on the flat, that would be part- load condition correct? so i dont want to make it more rich at cruise or on WOT, so how can i isolate the mid range or par-load to enrich it with out messing anything else up. i already messed this up trying to just lean it out slighty and over corrected.

if i adjust the inner screw by itself it changes both part and full load.
the outer screw in will richen part load i believe lean out full- load.
the Anders chart doesnt really address it.
- also i feel i cant really get idle right, it seems too rich but that might be the way the motor will be, not sure.

the MPS is a rebuilt one with Tangerine kit and adjustor screws, so easy to access and adjust using the Tangerine tools.

I may be at the point of just going dual webber with 44 IDF's, and forsaking the d-jet - OR a more modern programable EFI...... i just dont think i am getting the most power out of this motor that i should or would with better air intake and A/F mix.
intake is somewhat restricted on a stock d-jet and the injectors can only give you so much fuel. i did see somewhere anders wrote that the stock set up could support a build up to 2270 even with the proper changes( not sure what that means either),

anyway first question is - part load definition. then how to proceed to get this mid-range or par-load adjusted into a better mix with out making idle even more rich(or WOT either)

Thanks for the help.

Phil

[adolimpio]

Here's a point of reference for what it's worth.

2056
Raby 9550 cam
Hoffman heads with 44x38 mm valves
123 distributor w/ vac advance profile 1
Timing 27 btdc
Fuel pressure 29 psi
Standard motor FJ67 injectors
MPS settings
- 0 inHg - 150H
- 4 inHg - 128H
- 15 inHg - 80H

AFR
- Idle 14.5
- Part load - 13.5
- WOT - 12.5

Idles nicely at 900 rpm
Engine seems very happy

[914_teener]

Here's a point of reference for what it's worth.

2056
Raby 9550 cam
Hoffman heads with 44x38 mm valves
123 distributor w/ vac advance profile 1
Timing 27 btdc
Fuel pressure 29 psi
Standard motor FJ67 injectors
MPS settings
- 0 inHg - 150H
- 4 inHg - 128H
- 15 inHg - 80H

AFR
- Idle 14.5
- Part load - 13.5
- WOT - 12.5

Idles nicely at 900 rpm
Engine seems very happy

Phil.....

I'd wouldn't recommend NOT using the vaccum advance on that dizzy. BTDT.

I'd hook up the vac port on the dizzy to a ported vaccum source. It is there for a reason and the reason is as an adjustment(real time sensor for engine needs) for timing at part load. By looking at the plugs at a certain AFR you could be mistaking incomplete combustion instead of AFR.

So...looks like the above is using it...and the results show an engine that runs well.

Hook up the vaccum advance on that dizzy and reset your timiing...next step get an AFR meter and see what how the engine is performing.

Mostly....you'll know by the "seat of the pants" test and how cool or hot the engine is running...so I'd also recommend a CHT gauge and oil temp gauge.

Carbs react to vaccum by mixture and jets....if you have disabled that feature for your FI it won't run well. Just saying.

Rob

[DRPHIL914]

Here's a point of reference for what it's worth.

2056
Raby 9550 cam
Hoffman heads with 44x38 mm valves
123 distributor w/ vac advance profile 1
Timing 27 btdc
Fuel pressure 29 psi
Standard motor FJ67 injectors
MPS settings
- 0 inHg - 150H
- 4 inHg - 128H
- 15 inHg - 80H

AFR
- Idle 14.5
- Part load - 13.5
- WOT - 12.5

Idles nicely at 900 rpm
Engine seems very happy

Phil.....

I'd wouldn't recommend NOT using the vaccum advance on that dizzy. BTDT.

I'd hook up the vac port on the dizzy to a ported vaccum source. It is there for a reason and the reason is as an adjustment(real time sensor for engine needs) for timing at part load. By looking at the plugs at a certain AFR you could be mistaking incomplete combustion instead of AFR.

So...looks like the above is using it...and the results show an engine that runs well.

Hook up the vaccum advance on that dizzy and reset your timiing...next step get an AFR meter and see what how the engine is performing.

Mostly....you'll know by the "seat of the pants" test and how cool or hot the engine is running...so I'd also recommend a CHT gauge and oil temp gauge.

Carbs react to vaccum by mixture and jets....if you have disabled that feature for your FI it won't run well. Just saying.

Rob

Rob,

just to clarify, on a 75 d-jet 2.0 throttle body there is only a retard port, not both retard and advance, so do you mean hook back up the retard vac line to the 123 dizzy? - thats easy enough to do, are you saying hook up retard(not advance) to pull the advance that is set at 3400rpm down at ide to be more with in the desired 3-4 degrees at idle? i am going to check this tonight to see what idle timing is at as-is.

Phil

[914_teener]

Here's a point of reference for what it's worth.

2056
Raby 9550 cam
Hoffman heads with 44x38 mm valves
123 distributor w/ vac advance profile 1
Timing 27 btdc
Fuel pressure 29 psi
Standard motor FJ67 injectors
MPS settings
- 0 inHg - 150H
- 4 inHg - 128H
- 15 inHg - 80H

AFR
- Idle 14.5
- Part load - 13.5
- WOT - 12.5

Idles nicely at 900 rpm
Engine seems very happy

Phil.....

I'd wouldn't recommend NOT using the vaccum advance on that dizzy. BTDT.

I'd hook up the vac port on the dizzy to a ported vaccum source. It is there for a reason and the reason is as an adjustment(real time sensor for engine needs) for timing at part load. By looking at the plugs at a certain AFR you could be mistaking incomplete combustion instead of AFR.

So...looks like the above is using it...and the results show an engine that runs well.

Hook up the vaccum advance on that dizzy and reset your timiing...next step get an AFR meter and see what how the engine is performing.

Mostly....you'll know by the "seat of the pants" test and how cool or hot the engine is running...so I'd also recommend a CHT gauge and oil temp gauge.

Carbs react to vaccum by mixture and jets....if you have disabled that feature for your FI it won't run well. Just saying.

Rob

Rob,

just to clarify, on a 75 d-jet 2.0 throttle body there is only a retard port, not both retard and advance, so do you mean hook back up the retard vac line to the 123 dizzy? - thats easy enough to do, are you saying hook up retard(not advance) to pull the advance that is set at 3400rpm down at ide to be more with in the desired 3-4 degrees at idle? i am going to check this tonight to see what idle timing is at as-is.

Phil

Hey Phil....ooppps I didn't know you are running the late TB on your car.

Yea...I'd try it first and see how it runs. That dizzy has a hard map to the stock settings.....but that cam will want to idle a bit higher than stock and IIRC has a touch more duration for your Hoffman heads to breathe.

Just get the timing where the motor performs well and then check your AFR's with a wide band and head temps in part load and load and that motor should run and perform fantastically.

I think I saw James post the equivalent.

Good luck and drive it like you stole it.