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

[raygreenwood]

First off.....if you are getting mileage that low with this engine in a type 3....your MPS is out of adjustment or you have vacuum leaks or both.

2nd.....if the wire you have disconnected on your MPS is half of the zig zag,strip.....you have the wrong wire disconnected.
Do not just disconnect the one I may have quoted 6-8 posts back.....look at the pin out and look at my write up.....and follow the circuit trace...... ...i got in trouble that way to many years back. Even across 2-3 versions of the exact same part...they have several numbers stamped/molded into the TVS.
The positiions of WHAT a pin goes to on a TVS never changes.....but the numbers might for different vehicles across different time periods. In the end....the numbers are irrelevant.

No that is the same TPS design as my write up....and is one of the same TPS part #. I have all of them....both NOS and used.

This is the hardest thing to relate to people to get them to understand......how the floating switch of the TPS is actually working.

Its simply designed as tolerance in the throttle shaft bushing. Why?
Because you do not want to start adding excess fuel until....
A. The throttle is cracked open even a smidgeon so you air to go with that fuel and
B. So you also are probably getting vacuum advance transition.

And this is the important part:

But.....you do not want lag....meaning ....if the throttle starts moving....and you are not ALMOST instantly getting extra fuel.....within a degree or two of movement....from the TVS...you will get a flat spot.......AND......this effect....will cause you to adjust the MPS incorrectly.......to give you that fuel you need for getting off the line....from another source.

And......that incorrect MPS adjustment is what is giving you the rich runnijg snd po9r fuel mileage.

The slack/slop built into the TVS is in two parts. About half is in the main hub that mounts to the throttle shaft and half is in the fork of the switch.

This slack allows the forked switch of a properly adjusted TVS......to bias toward closed when the throttle is closed.....and toward open when the throttle is in forward motion.

THE PROBLEM IS THIS:
Many...if not MOST.....TVS.....have just about the exact amount of 2° movement between ofc and on at the fork switch.........BUT....they have more than 2° at the main throttle shaft mounting hub.....so when properly adjusted....they get out of sync by a degree or so......so the bias or float of the forked switch becomes uncertain.

This is why the books all state.....if once you adjust....the reading is not perfect on the volt meter.....turn the adjusting plate one more grad toward open to bias the switch float more toward open to account for lag.

BUT....BUT.....in many cases that is BAD ADVICE.....BECAUSE......each grad on the plate is 2°.....and the amount of slop you are accounting for may actually be only 1°....or may be 3°....or may be already biased to far toward open and it may be toward closed that you need to adjust to (that last one is rare but it happens).

The key is that when the throttle is closed and you adjust the plate position......you MUST then check...and you will need a magnifying glass to do so....the actual position of the exact tip of the wiper arm ....on the circuit board.

Why is this so important?

Understand this...that if the donut shaped bead or contact tip of the wiper arm is on the center of say.....the very first cross hatch contact on one of the two enrichment wiper strips when the throttle is fully closed.....instead of in either the correct parking position on the circuit board (on some tvs)....or on the gap between the first and second contact marks of the two wiper strips........then.....when the throttle starts moving toward open.....it will be 2° of movement before the forked switch makes contact.
During that 2° movement.....the contact tip of the wiper arm is moving off of the first contact. At this point you are getting no enrichment because the forked switch has not yet closed.
2° later....when the forked switch has jow closed....the wiper arm tip is now actually in the dead area between the two strip contacts on the board....and it will be another 1° to 2° of throttle movement before it contacts the next one....so you get a dead spot.

I will look at my write up and if needed .....post an extra picture of which track....regardless of number...is the fuel overrun shut off wire. Ray

[Keith Park]

Ok, I think iM getting the big picture a bit better, reading this:
"THE PROBLEM IS THIS:
Many...if not MOST.....TVS.....have just about the exact amount of 2° movement between ofc and on at the fork switch.........BUT....they have more than 2° at the main throttle shaft mounting hub.....so when properly adjusted....they get out of sync by a degree or so......so the bias or float of the forked switch becomes uncertain. "
sitting there staring at the TPS on the bench in front of me, with the play in the switch section, and the mount hub, wondering if the 2deg was for BOTH or just one? Brain jamb! So I want the enrichment to hit the first rung of the cross hatch about 2 degrees after the throttle is cracked open... correct? or 2 degrees after that forked switch makes contact in the forward direction?

YES, Im running WAY rich at small throttle openings, 10's and 11's AFR and when im driving stuck in traffic and slow speeds that kills the gas mileage.
But my Quandry is: Ive adjusted the MPS to just Kiss 14 on the highway (and in town for that matter) at its leanest point (about 1/3 throttle), so on the highway and even on secondary roads if I can move along and keep on the throttle enough the mixture is at least in the 12's and I get 22MPG under these conditions, about what I would expect.

So I cant go any leaner with the MPS, Ive looked for another way to lean out the slight throttle richness and so far haven't had good luck but I need to get this TPS right cause as you say, it has an effect too. Im so rich off the line
it runs well even without the TPS!

Please post that diagram, I also need to verify which wire on the harness is not connected to the TPS, I thought it was the end one but maybe not... this is a stock harness and one of those 5 wires went nowhere.

Thanks Ray,

Keith

[Keith Park]

well with most of the oil leaks taken care of, at least for now I removed the TPS and gave it some attention. The wires are going to the appropriate terminals, ground is ground and the disconnected one is indeed the full throttle enrichment. With that sorted out I tightened up the play between the inner hub and switch assy with some thing shims, I didn't want to sleeve the contacts as the spring contact is very close to it already and it would not have been able to disconnect had I done that.

First adjustment I tried was with the enrichment contact ready to touch the first of the cross hatch when the throttle is opened (with 2 degree or so of play) WIth it this way the bucking was worse, less drivability and then something you said made me try something else, you stated that if the TPS is not adjusted properly you need to get the quick enrichment from somewhere else and then that adjustment (MPS) will be too rich. Well,
my MPS IS way too rich off idle, and unfortunately I cant lean it out anymore
without making the third throttle area too lean, SO... with that in mind, I set the TPS to get the idle wiper to the idle pad as soon as possible, so under
small throttle openings it would park on the idle pad and prevent excessive enrichment as the ECU would think its time to idle.

This helped drivability, much less bucking! It still has an over-rich light throttle area, lean 1/3 throttle area but no hesitation off the line. Its not bad this way but I still suspect the in town gas mileage will be crap. I know this isn't the way its supposed to be adjusted but given the vacuum sig I have, and the limitations I seem to be running into its a best case scenerio for drivability.

Another observation I have is that this is an 037 ECU which takes the 1200 ohm head temp sensor. I have a 2500 or so sensor on it and a shunt, so cold its about 2K and even with that its warmup curve is quite lean, and in town under light throttle that is pretty good, and as it warmps up fully (takes some time) it slowly gets richer to the setpoint I have it (14AFR or less on the highway). Kinda curious why its so lean on warmup with that sensor so high in resistance?

Lastly, I have the Dcel valve disconnected, as I DONT want it any richer under small throttle openings that it is and I can do anything I want with the inner stop etc and I NEVER see lean spikes under light throttle/high vacuum. Is it OK to leave this out? or am I not thinking of another benefit of having it in there?

THanks

Keith

[raygreenwood]

[Keith Park]

Yes, Mechanical Dcel valve that is adjustable, but I haven't touched that adjustment. This engine is tight, new, only a couple thousand miles on it.

Well your certainly not the first person to tell me not to look at my gauges,
Im kinda OCD with the AFR meter as this engine has always run hot oil temps on the highway, although now I have a cooler on it and those temps are capped and no longer a problem. Heads have always run cool, 235 - 285 on the highway depending on load IF I believe that sensor, its a thermocouple I have held against the head over #1 spark plug with a spring loaded ceramic doohickey I put on there, but when accelerating from a light the heads seem to cool awfully quickly making me think that the cooling air may be cooling the sensor faster than the head, how quickly DO the heads cool when RPM goes up?

Anywho, being in a square I can run with the lid open and its easy to hear if there were any pinging and last summer I ran for a bit with the AFR in the 14's and heard none.

Gas mileage on the highway seems what Id expect, 22mpg, does that seem rich? around town its 15 - 16 rich! and Id expect 17... what do you expect Id get with a 2056 in town in a Square?

SO, you recommend I put tape over the wideband meter, lean up the MPS so long as it runs smooth and doesn't detonate, and not worry where that lean spot ends up. its NEVER had a lean spot at small part throttle, at least with the way Ive had it adjusted so far, only lean at that third throttle area then richening up again nicely when I really get into the throttle.

ONE thing I still have a bit of a problem with that makes me think it may be too lean is when its in its lean areas is that intermittent missing, this is MUCH better with the trigger contacts advanced as much as I could get them, perhaps I passed the sweet spot and can back that off a bit and make it better... I still need to try that.

I just get OCD over high AFR's.... Ill stick some tape over that gauge and try leaner!

Keith

[Keith Park]

well the roads are salted up and the car is away for the season. It was running decently but rich around town. The biggest aspect for me with this tuning process is what to expect. For the last 200Kmi or so Ive run a stock engine, and in the past few years a tired one, so even if the 2056 were running on 3 cylinders it would feel powerful to me! The Stock motor only got low 20's in town for gas mileage, less than that when the weather got cold, but yea... it was on the rich side too.

So with the wide band taped over, I can lean it up and it should run well with the exception of the missing I get during that part throttle lean spell, but hopefully with more careful adjustment of the trigger points I can eliminate that, when going more advanced with that it got a lot better, I may be too far now though.

So assuming I can get a nice smooth response from it, and better in town gas mileage, when I untape the AFR gauge what lean or rich spikes should worry me? I know about the very lean issue under light cruising throttle that I have not yet experienced, but perhaps will when things are leaned out overall but what other Yellow or Red flags should I watch out for?

I can monitor oil temp quite accurately, and head temps at least to some point. and One thing that I noticed last summer that I didn't mention so far was on one highway trip traffic was moving along well and I brought the cruise speed up to 75 or so, about 7 or 8 MPH higher than usual and it ran
a good 10 degree's cooler that way, what RPM does the T4 cooling fan top out CFM at?

Keith

[raygreenwood]

[Keith Park]

Thanks Ray, Im starting to get a better understanding for what Im seeing. I suppose the best "Filtered average" measurement is the gas mileage, as that's an average over a couple hundred miles of running! IT tends to stay in that band of leaner running on the highway more often, so that makes sense that its highway mileage is better, but around town its not in that band very often so mileage is lower.

I thought of putting the lambda sensor in the tailpipe, but feared that would be too much of a restriction.

The head temp sensor is just a thermocouple pushed against the head with a little spring loaded ceramic piece I made, I don't trust that when it says say 280 that that IS the temp of the head, there may be some delta T but I can see if things will change in temp as I lean out, and I suppose that will warn me if its getting too hot. With the Square its easy to hear pinging with the lid open so that will work.

In the spring Ill try leaning out the MPS, see if I can get the missing in the lean spot under control with the injector timing and watch for hesitations off the line or lean spots under very light throttle that haven't been noticeable so far. Since the bucking seems to be worse when rich and better when lean that should improve and maybe I can get the TPS adjusted more in the way of how it should be.

At least the oil leaks are under control now! and I have all winter to find a couple spare good 2L injectors.

Thanks

Keith

[Keith Park]

Well its spring and the Square is out again, and time to get back into tuning!

To pick up where we left off, the consensus of an overall too rich mixture will be something I deal with by leaning out the MPS a bit, taping up the AFR meter for a while and see how it feels. I think my biggest issue as I lean it Out to where it probably should be will be the intermittent missing at part throttle where the “Lean zone” is, however adjusting the Timing on the trigger points helped with that, and perhaps I still don’t have it where it is ideal as I was never able to see any Pulsing of the fuel pressure as I changed that.



Next question is timing, I have it a stock 28 degrees, and I have tried moving that up and down by 2-3 degree’s with no noticeable difference

But what should I be looking for in getting the timing in the sweet spot, and should I even touch it until I get the mixture set up to where

It should be? The KB pistons Im using suggest 2-3 degree’s less timing, should I start by retarding the stock numbers im running now

That much and run with that?

Thanks



Keith

[Keith Park]

Well Ive leaned up the 2056 to the point that im getting 17-18MPG in town and 24 on the highway at 70 and that was even when it was a bit heavily loaded. Oil temps when it was 62 out were running around 200 with heads in the 280’s on average, when temps were around 70 for the return trip oil was up to 215 – 220 and heads occasionally popped over 300 but that thermocouple was getting a bit screwy. Not sure why the oil was so much higher for a small change in ambient.



It seems to be running well, not hearing any detonation, a quick peek at the AFR on the highway saw it running 14’s at half to ¾ throttle, occasionally kissing 15

But going down into the 12’s under full throttle. I still get occasional miss when its in the leaner ranges but mainly when its warming up and that gets less the more advanced I get the FI trigger timing, but im probably 15 degrees or so advanced now and not sure I can clearance the distributor to go any further. Still have some bucking on occasion but much less and again, mainly light throttle during the initial stages of warmup.



Its getting there, I just hope I can keep the oil temps down far enough when the weather really heats up, hopefully the SETRAB will be enough.



Keith

[Keith Park]

pressure sensor issue and question.
The 2056 is running nicely now and the setup is just about where I want it, so I decided to swap the spare pressure sensor back in to match the calibration with the one Im using and happy with. Both are 2L 914 037's and I have set the mixture on the spare to match that of the good one im running and did this during highway driving, they match pretty well now BUT, when Im using the spare, and this has been a past problem with this one, it runs perfectly on the highway, AFR numbers under all conditions same as the good one, it idles fine, it goes down 45-55 MPH roads just fine but when im at say 45 or lower, and in moderate to heavy throttle, especially at lower RPM's, it leans out drastically and starts to misfire, you can see the AFR lean out in its numbers too

Now main mixture is fine on the highway, so im assuming that's correct or darn close, the outer stop is for full throttle only so Im assuming that cant be the problem, the inner stop is for high vacuum light throttle only, so that shouldn't be it unless that can lean it out too much under moderate to heavy throttle at low speed..
So what could the issue possibly be? Ive had it apart, holds a vacuum fine, diaphragm is good, armature FEELS fine, no drag, but what could possibly be causing this issue with this one sensor?

Im stumped! thanks

Keith