D-Jet PhD Sticky. Newbies Need Not Enter. Advanced FI Tuning

[Keith Park]

I also agree with Bob, I need to get into the distributor, it starts into advance right off idle and is jumpy with that transition. Maybe Friday Ill have a chance to get the distributor straightened out. I want no play in those springs right? so the weights are held closed until centrifugal force starts the advance.

with the stock engine, I know it was running rich, with the amount of towing I did I figured run it rich and don't worry about it, yea the 1200 and 1800 RPM giggle was there on occasion but with a low HP engine and heavy flywheel drivability was OK but far from optimum. I did get 165K out of that engine! The 2056 in there now is definitely running rich off the line, I swapped in the 049 MPS spare that I have and tuned with the engine when I first started all this years ago, its leaner off the line and tracks better, so Im going to do a small outer move of the inner stop tonight and see if that leans things out to where it should be for idle and light throttle conditions. Once I have the right TB on there with all the advance/retard hooked up properly, the Dcell hooked up properly, the dist tight Ill noodle with the outer stop and
see if it makes a difference, and if not, we'll see what ive got wrong as to why its not more touchy with off the line performance.

[raygreenwood]

[Keith Park]

sounds good, Please post that link, im planning on doing the distributor
tomorrow and if its running well enough I may pull it up on the highway for an hour or so to make a camp run with it and see how it does.

moved the inner stop on the MPS out slightly, its less rich under very light throttle now but still too rich, its "I can smell it" rich. Ill try another small adjustment tonight. How hard a vacuum should the MPS hold? My diaphragm looks good and the assembled nose section seems OK but it has a small leak somewhere, it wont "hold" vacuum. Should there be a paper gasket on BOTH sides of the diaphragm or just the atmospheric side?

Thanks,

Keith

[raygreenwood]

[Keith Park]

Yes, inner stop, hex key...
I moved it out just a bit, idle is still rich but a bit less so, and my richness is mainly really light throttle, just off no throttle at all when cruising, as I open the throttle more it leans to the 12-13 range, as the RPMs go up it goes thru the 13-14 range.

so for a rich very light throttle should I move it in or out, or look for the problem elsewhere? Idle is still rich....

if the 049 Pressure sensor I have holds vacuum is there ANY reason I shouldn't use that one in an 037 based system? if so should I reverse that
spacer as you had mentioned earlier?

Thanks

Keith

[raygreenwood]

[Keith Park]

thanks for getting that out Ray, I certainly don't expect a long response several times a day anyway. One thing I have this time around with this engine is TIME. I don't HAVE to take the car on any long trips if it isn't ready,
and mechanically the motor seems fine at this point.

I screwed the outer stop in a half turn (this leaves is out a half turn from
fully in) and no change. Took it up on the highway and it just seems to track backwards, at the same RPM (3200) on the highway the farther down the pedal goes the more LEAN the mixture gets, unless you really floor it then it richens up. its in the low 14's under say 50% throttle and the high 11's under very light throttle. Odd......

I sprayed some gumout around the MPS to look for a vacuum leak and nothing showed up, so its a small leak but the 049 holds vacuum and maybe Ill run with that one instead. I did try the RTV on the seal and that didn't work with this one.

One question, I heard knocking and pinging under heavier throttle on the highway, BUT... the ignition at this point was intermittent as the Dcel valve
was shorting the coil terminal, could ratty intermittent ignition cause knocking and pinging or should I back off the timing a couple degree's? its at the stock 28 currently.

Thanks

Keith

[raygreenwood]

[Keith Park]

Sorry, I should have been more descriptive, Im using a stock T3/4 decal valve its just attached to the MPS bracket and the whole thing is laying on top of the engine at the moment so I can get at the nose to adjust it and it slipped in next to the coil.

Ive got almost a quarter turn OUT of the inner stop now and while it SEEMS to be tracking better at very light throttle, it still has a rich spot just off closed throttle, the thing that bothers me is as I remember and as you pointed out, that inner stop is VERY sensitive and I seem to have moved it quite a lot with only a small change.

Im not really ready to tweak the outer stop till I get the TB and Dcel valve hooked up, but if you point out that its sweet spot is very narrow Ill spend some time with this once Im ready, its not bad now... but there is some throttle response that could be improved.

unrelated question, right now I have the AAR closed, so it wont muddy up
observations if it sticks on a bit or leaks inconsistently, and currently I have an L jet one on there as its adjustable, did these work well enough that I can use it out of the box (as its not adjustable) or should I retain the L jet unit
where I can adjust how much air it flows during cold warmup?

Thanks

Keith

[Keith Park]

OK, I rebuilt the distributor. It really wasn't all that bad but I paid special attention to the areas in the article that I should, the only thing that I did that really might have changed something is tighten up on the initial
advance spring by bending the tab out just a bit, maybe getting the advance to kick in just a bit later, as it was starting pretty much right off idle.

Well...

I really screwed SOMETHING UP! Starts, wont idle, ran REALLY lean, popping back, I was able to set the timing, that appears to work, it is advancing as it should, but Its not drivable, NO power. I tried both MPS's, same issue... I richened It up a full turn, now the AFR reads OK mixture but still, no idle, no power.

What could I have possibly done?

Checked the firing order, that's OK, I don't think it would run if I switched 2 anyway or it would be rich... I did move the trigger points a bit as they are on the elongated holes... still, it shouldn't be THAT sensitive to that. Both contacts are closing, so they appear OK.

Timing is advancing
Forced it rich
No wires appear off... could delaying the advance a bit cause this drastic a reaction? or moving the trigger points over a smidge?

I did try bending the tab back just a bit, no improvement

???

Keith

[Keith Park]

Had #2 and #4 plug wires crossed, still reads 1234 when you do that but after stepping back, serenity now, the frame of mind changes and allows
logic to take over more for troubleshooting.

Still

Timing looks more stable now, bucking is still there but seems better, stumble off the line that could be the outer stop, wont mess with that till
I have the vacuum adv hooked up

retarded the timing to 26, to prevent pinging, road trip today... we'll see how she does on the highway.

Keith

[Keith Park]

OK, after some highway miles Ive settled on stock timing, 28 full mech adv,
and it seems to run well on the highway with the AFR between 13 and low 14's, although that seems a bit lean, head temps are 250-275, and gas mileage on the trip I just took to PA is 23.1 all highway at 70. that seems a bit TOO good, I recall it ran about 22 before on this engine, am I a bit lean with that mileage in a Squareback? heck! the stock motor didn't do much better...
got the outer stop adjusted so no hesitation off the line, Dcell valve is hooked up.
Problem is, in town, is 15-16MPG when I think it should be 17. Big theme now is TOO RICH under light throttle, even on the highway, but on the highway your usually under enough throttle to lean it out to where it should be. The system doesn't seem to track properly, almost backwards, the lighter the throttle the richer it is, the heavier the throttle the leaner it gets. Not sure how to adjust this kind of a problem.

When off the gas decelerating, its MEGA rich, I mean... gas out the tailpipe rich, AFR of 9.9 on the highway when the throttle is closed. Not sure what is going on here, the fuel cutoff wire on the TPS is disconnected at the moment, #17.

Also, even with a tight distributor the bucking is still there... and as it passes through the bad spots, 1200 and 1800 on decal, foot OFF the gas, it will from time to time just start bucking at these points as it passes thru them.
so what is really doing this, with NO throttle? Hmmmm....

So great highway car, gas hog around town with some bucking issues. Ill have to see what adding the vacuum advance does to these issues when the new TB arrives, Ive never had that working on this car.

Keith

[Keith Park]

Well, everything is in place now and connected up as it should be, the new TB does seem to help keep the super rich problem just off closed throttle to a smaller range, it is still there. If Im decelerating and there is still a little throttle on its super rich, as I put more on it gets leaner, if I drop the throttle completely it comes up leaner to a more reasonable range in the 12's. How do I eliminate that rich spot?

One thing I investigated was the inner stop in the MPS (inverted hex) I measured the original bad diaphragm from this 037 MPS that im using and found that the inner stop on the replacement diaphragm in It now was a FULL TURN inward too much! ( I think I can hear Ray's ears ringing).
Not sure how it got this way but I think it got moved WITH the mixture screw
when I was adjusting it. I took measurements and set it back to where the original was, and no real difference, I may still have it in too far, could this cause the rich spot right off no throttle?

Ray, you mention setting the inner stops up on molested MPS's with feeler gauges, yet mine has the stop right against the retaining plate with its opened up, where to you measure with the feeler gauges and what gap?
Id like to make sure that this inner stop is right before proceeding, or close anyway. Im NOT getting spikes lean, the opposite really. Also the whole range of throttle seems to get richer under lower throttle and leaner under heavier throttle TO A POINT, then when you really floor it the mixture goes back to a more reasonable 12's range.

Head scratching now....

Keith

[Keith Park]

OK, a nice 75% highway trip netted 22mpg, not bad, maybe even too good, so am I too worried about rich at small throttle openings? well... I think so.
When its warming up, the bucking is MUCH worse, and it richer during warmup so Im starting to think that the bucking is made worse or a result of running too rich at small throttle openings.

On the highway, its generally leaner the more the throttle is open, unless floored where it richens up a bit. BUT, when your at light throttle its very rich, unless you decelerate and close the throttle completely, THEN the TVS can be seen telling the ECU to cut fuel and it leans up into the 12's, IF the vacuum is high enough to do that.

Another clue... moving the inner stop anywhere makes no difference in the running, in my engine maximum vacuum is under high RPM deceleration, like on the highway, at idle its only 10-12 in Hg, BUT when a vacuum pump is hooked to the MPS as Ray has suggested a while back you CAN get the idle to lean up considerably, to the point of stalling but the engine never produces enough vacuum at idle to do this, no matter where the inner stop is set.

I re-adjusted the inner stop to where it was in the original 037 diaphragm.
Even on hard decal though, it never spikes lean beyond 12's in the AFR.

Boosted the timing to 30BTDC hoses off, I can see the vacuum adv working now and once warmed up, car accelerates and drives nicely, except for the bucking.

Somehow I need to lean it up under the lower throttle openings, get it track better, and I have a feeling that if I can get it a more reasonable AFR under those light throttle openings, my bucking will get better or go away.

Ideas on leaning up part throttle? how do I get the MPS to run leaner under the higher vacuum situations but NOT leaner under lighter vacuum (heavy throttle)?

Hmmm....

Keith

[raygreenwood]

[Keith Park]

Thanks for answering, while you were busy Ive had some time to try a bunch of things and noodle with it.
My confusion with setting the inner stop is that with the MPS open, and android chamber out but the keyhole plate still in place the inner stop is already pressed against the keyhole plate. so I pulled apart an unmolested 007, this also has the inner stop right against the keyhole plate as well, there is no gap.

I know when the aneroid chamber is in place, and the unit closed that pushes or attempts to push the inner stop off the keyhole plate but then of course I cant access anything.

So am I actually measuring the distance between the washer on the diaphragm and the keyhole plate (ie, how much the inner stop is above the diaphragm washer? If so that wouldn't change moving the spacer around.

Im confused, should the inner stop NOT be against the keyhole plate with the unit apart?

Thanks

Keith

[raygreenwood]

[Keith Park]

OK, got it. This is what Id done, when I first pulled apart this 037, I measured that distance that the inner stop protruded on the bad diaphragm with a micrometer and set the new diaphragm to that, this had been disturbed at some point but its back there now. I have the spacer on the cover side of the diaphragm on this 037, which is opposite the 007 I have, but really, doesn't this just change the pre-load of the diaphragm? if the spacer is on the cover side, the diaphragm is closer to the keyhole plate, if the spacer is on the plate side the diaphragm is closer to the cover, but the hub of the diaphragm is wherever the adjustments hold it too, between the inner and outer stop, so why would the inner stop setting change if your only changing the the location of the diaphragm outer lip and not the height of the keyhole plate?

Keith

[raygreenwood]

[Keith Park]

Ok, I THINK I have this in my head now, increased stroke.
One thing I didn't check was the Flange thickness on the 2 different diaphragms, the 007 was a bit different, had less pleats in it, Ill have to check that.

One thing Im going to try, just to see what happens, is swap in a 007 that I had with a bad diaphragm, I RTV'd the diaphragm up for a temporary repair but Im interested in seeing what the curve looks like with a long nose opposed to the short nose 037.
I appreciate the pix, my inner stop protrudes farther inward than the one in the pix.

Keith