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

[BeatNavy]

(IMG:style_emoticons/default/agree.gif) with this and with Rob's ( @914_Teener ) point about Jake's advice to "give the engine what it wants." When you go beyond stock you are in unchartered territory to some extent. In your case in particular, a CR of 9.5 is well outside what Jake recommends for that cam/FI combo (he suggests around 8.5, max). That doesn't mean you can't make it work for your specific combo, and it sounds like you are to a large degree, but it requires a lot of measuring and trial and error. IMO you really need an LCR and and an understanding of how much vacuum you're pulling under different driving conditions. In terms of idle, I'll suggest it one more time: try not to obsess over a specific 'ideal' idle AFR.

[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

[emerygt350]

Just put the AFR on mine and did some tuning.

Got partial load in a good range centered around 13 to 13.5. Give it a little and it drops to 12, take of the gas a little it moves up to 14.7 (not sure why it hits it on the mark like that but there you go). I noticed that as I approached what seems to be good partial mixtures, my idle mix was changing and that as I get closer to where it probably should be that adjustment knob on the ECU is getting closer and closer to the factory setting.

Still working on the WOT. Started out Lean across the board, backed out the stop screw and got that to around 12 never leaner than maybe 12.5 or 13 but I noticed after my partial load tuning it looks like my WOT is running a little lean again. Need to double check that when I get another chance. Sucks how all these adjustments interrelate.

My 123dizzy is running on retard (A) at the moment. I cant stand high idle. Not sure why it bothers me so much, but it does. Luckily I can access the pot without removing the dizzy so it's easy for me to switch back and forth. When I am all done I might give advance a try again.

Here is a plug after an hour of mixed driving. Looks pretty nice.

[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

[DRPHIL914]

(IMG:style_emoticons/default/agree.gif) with this and with Rob's ( @914_Teener ) point about Jake's advice to "give the engine what it wants." When you go beyond stock you are in unchartered territory to some extent. In your case in particular, a CR of 9.5 is well outside what Jake recommends for that cam/FI combo (he suggests around 8.5, max). That doesn't mean you can't make it work for your specific combo, and it sounds like you are to a large degree, but it requires a lot of measuring and trial and error. IMO you really need an LCR and and an understanding of how much vacuum you're pulling under different driving conditions. In terms of idle, I'll suggest it one more time: try not to obsess over a specific 'ideal' idle AFR.

yea, i am concentrating on my afr readings during part and full load and it’s really close now, so if reading at idle is a bit rich that’s fine, as you say it may not be accurate, now i need to see why my idle is so low, or why i need that idle screw out that far. so will do a recheck on the vac like you suggested and check my advance at idle , then may reconsider the curve i’m using and as rob is saying maybe put the vac line back on and change the curve setting back to either 3 or 4. here is the chart from 123

[emerygt350]

I bet you are a bit low on your timing. Have you tried adjusting your timing till you get a good idle (850) and giving that a try?

[DRPHIL914]

I bet you are a bit low on your timing. Have you tried adjusting your timing till you get a good idle (850) and giving that a try?

was at stock 27 degrees@3400rpm and verified before slightly increasing it which helped
but i have to go back and recheck it at idle too and see what its at at 900rpm - one other factor thats going to effect that is the richness/leaness at idle, thats why the true AF at idle matters too. hope to get to check it tonight.

[BeatNavy]

one other factor thats going to effect that is the richness/leaness at idle, thats why the true AF at idle matters too.

Idle mixture matters. You just shouldn't put too much stock in what your AFR gauge is telling you at idle.

[emerygt350]

As I have zeroed in on good mixtures across partial and wot my idle mixture has moved all over (depending on the screw I was messing with). However, my idle speed has stayed very close to 850 regardless of richness, of course it is only maybe the difference between 13 and 12. And yeah, afr at idle isn't particularly accurate but it is better than nothing.

I just twisted the stop screw in a 3/4 turn and that fixed my WOT leanness. Now the leanest it gets at WOT (under heavy load climbing hills) is 13. Tempted to go even further but it is running so good now I don't want to mess with it. I dare to say it 'throws you back in your seat' at low and high rpm when you give it some gas. 3rd gear is particularly fun from anywhere between 30 to 60.

It is fun seeing how much the TPS enrichment matters on that AFR.

When I get a chance this weekend I will record my inductance with the LCR.

[JamesM]

one other factor thats going to effect that is the richness/leaness at idle, thats why the true AF at idle matters too.

Idle mixture matters. You just shouldn't put too much stock in what your AFR gauge is telling you at idle.

(IMG:style_emoticons/default/agree.gif) THAT^^^

Depending on the placement of your wideband or your type of exhaust your readings at idle could be totally out of whack. With d-jet I would dial idle in by ear or vacuum gauge rather than AFR. Twist the idle knob to lean until the engine starts hunting at idle and then move it back rich one or two clicks and you should be good to go. setup cruise and WOT by AFR but idle by where it runs best.

[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.