D-Jet annoyances, The final solution Options

[saigon71]

Even in a fine state of tune with no vacuum leaks and the ECU set to full rich, my cars idle would hunt terribly during warm-up (occasionally stalling).

The other problem I have is that on particularly hot days, the car heat-soaks if I shut it down while running an errand. It becomes extreemly difficult to start until it cools off. I'm not talking vapor lock here, definately heat soak.

Last year it left me stranded in a cemetary following a funeral in the blistering sun. Twice, heat soak has caused my car to not start while on a date, which is a little embarrassing in your 40's. (IMG:style_emoticons/default/dry.gif)

I drive this car a lot and needed to find a permanent solution.

I studied this thread closely:

http://www.914world.com/bbs2/index.php?showtopic=298261

After considering a bunch of alternatives, I felt the best all around fix was indeed a parmanent trim knob in the passenger compartment. Based on the testing and research by PBanders, I only needed to richen the mixture for both problems.

I'm not big on drilling extra holes in my car, so I fabricated a custom bracket that takes the place of one of lower dash washers to mount the potentiometer.

I tested it today. It wasn't hot enough to verify that it will cure the heat soak condition, but it sure worked awesome to smooth out the idle hunt during warmup. I'm pretty sure it will work to get me over the heat soak condion and allow me to start the car as I can instantly add 500 ohms of resistance to the CHT circuit and cause the mixtrue to richen.

I used a 500 ohm pot for this. I'll try a 1,000 ohm pot if the 500 doesn't cure the heat soak problem.

A huge thanks to Pbanders for his research thread listed above. (IMG:style_emoticons/default/beerchug.gif)

[GregAmy]

Watching.

I've had similar issues with cold idle, but not so much the heat soak problem. I've got a couple of settings on the D-Jet ECU idle mixture that I know where to set, but of course when it's set properly for cold start then it runs rich when warmed up (and vice versa).

I've often thought that if we could determine the proper resistance values to accomdate this then the best solution would be a latching relay. Hit the button and the relay closes for a set amount of time (5-10 minutes?) and then automatically opens the circuit. This relay would control both a resistor for the CHT sensor and an electric solenoid AAR valve (seems so silly to me to have to maintain constant power to the AAR after warm up).

So...quite interested in what numbers you come up with.

[JeffBowlsby]

Watching.

I've had similar issues with cold idle, but not so much the heat soak problem. I've got a couple of settings on the D-Jet ECU idle mixture that I know where to set, but of course when it's set properly for cold start then it runs rich when warmed up (and vice versa).

The ECU idle control knob only has effect at idle, because it is switched through the TPS. Off idle it has no effect.

[GregAmy]

The ECU idle control knob only has effect at idle, because it is switched through the TPS. Off idle it has no effect.

Exactly.

[brant]

The ECU idle control knob only has effect at idle, because it is switched through the TPS. Off idle it has no effect.

Exactly.

Agreed, the adjustment knob is idle only and not a tuning knob.

It seems that using a wide band to tune the MPS would provide a better solution
having the correct mixture all of the time and not running the risk of tuning the fuel mixture by seat of the pants or sound.