What's your A/F on Overrun?, 'Nother D-Jet A/F Question Options

[BeatNavy]

AFR of 12 will not hurt the engine and is reasonable I think. What MPG do you get?

Barely 20 MPG, driving mostly in and around my neighborhood and to/from work, which is mostly parkway driving - 55 mph for 2 miles, then a stop light - rinse and repeat. The few opportunities I've been able to track actual "highway" driving I MAY get closer to 24 MPG. Nothing close to the 30 MPG or more that many claim.

[Frank S]

AFR of 12 will not hurt the engine and is reasonable I think. What MPG do you get?

Barely 20 MPG, driving mostly in and around my neighborhood and to/from work, which is mostly parkway driving - 55 mph for 2 miles, then a stop light - rinse and repeat. The few opportunities I've been able to track actual "highway" driving I MAY get closer to 24 MPG. Nothing close to the 30 MPG or more that many claim.

Thanks Rob,
this is what I get out too (20.5 MPG) but this is while driving it hard and still doing some minor adjustments.
Season is almost over, so probably no normal driving within this year...

[cgnj]

Hi,
just saw this. A while ago I had a PM exchange with Brad Anders regarding the differences between each of the DJet ECUs.


This is a para phrase of what he explained to me, rgarding overrun cutoff and the 4 and 5 waveform generators.

Overrun cutoff ended up being a mixed bag with regard to emissions. Apparently, it doesn't work that well, something with regard to engine cooling. In the early '70's, before the 3-way catalytic converter became available, manufacturers were trying anything and everything to meet the new CO, HC, and NOx standards.

Perhaps he will chime in here.
Carlos

[Olympic 914]

I played around with my MPS, decal valve, tuning and a host of other things since I originally posted this. Car runs great, idles well, and is blast to drive. But I still see AFR numbers in the 12 range during decal, and my MPG numbers are not great. For the most part, I've given up worrying about it much, particularly since I have plans for a different motor before too long.

All good (IMG:style_emoticons/default/beerchug.gif)

I also have played around with my MPS, and timing.

On decal I see around 15.0 + afr. I may be running a little on the lean side though.

But on a cruise the AFRs vary from mid 12s to high 14s depending on throttle position.

Do you have a meter to check your MPS values? I have notes around here somewhere with where I set the MPS on my car. Maybe we could compare settings.



Little different system since I have the 037 ECU

[BeatNavy]

I played around with my MPS, decal valve, tuning and a host of other things since I originally posted this. Car runs great, idles well, and is blast to drive. But I still see AFR numbers in the 12 range during decal, and my MPG numbers are not great. For the most part, I've given up worrying about it much, particularly since I have plans for a different motor before too long.

All good (IMG:style_emoticons/default/beerchug.gif)

I also have played around with my MPS, and timing.

On decal I see around 15.0 + afr. I may be running a little on the lean side though.

But on a cruise the AFRs vary from mid 12s to high 14s depending on throttle position.

Do you have a meter to check your MPS values? I have notes around here somewhere with where I set the MPS on my car. Maybe we could compare settings.


Little different system since I have the 037 ECU

My Air/Fuel numbers are pretty good - similar to yours at cruise.

I've actually swapped out like four different 043 MPS's in an attempt to figure out what was going on. Last year I picked up one rebuilt professionally by that company back in the day (Fuel Injection Corp?), and I used that for a while. I assume it was calibrated to stock 2.0, but I didn't notice any real improvement in my MPG, although I was probably slightly lean at cruise.

Earlier this summer I picked up a stock, unmolested 043 that I wanted to use to baseline my MPS values on my inductance meter. That confirmed my suspicion that my (cheap) inductance meter provided significantly different values than those documented by Anders, particularly at part and full load (idle wasn't too bad). So I've used that stock 043 as my "calibration," and adjusted my other MPS to just slightly richer than stock.

I can definitely share my numbers, but what would probably really help is to let you use that stock 043 so you can also calibrate your inductance meter. It's my guess that different models/meters can vary quite a bit. Let me know if your interested.

In terms of my mileage, that remains somewhat of a mystery to me. It could be multiple factors. It could also just be what it is.

[nordfisch]

...
Not sure if the higher vacuum level at higher RPMs is ever so slightly preventing the throttle plate from closing fully, but I pulled the body and TPS to check it out:



As I understand it, in order to be in the idle/overrun "circuit," there needs to be continuity between where the two arrows are pointing in the picture above - the little arm (where the smaller arrow is pointing, the fuel shut-off switch) and the pin (where the larger arrow is pointing). The middle "wiper arm" also needs too be on the idle trace on the board. The only real difference between idle and overrun is the ECU will shut off fuel delivery at RPM's >~2,000. Is my understanding correct?

Even after careful adjusting of the TPS I find there's too much play in the switch/throttle body shaft to reliably ensure continuity unless the throttle is really fully closed. May need to overhaul the throttle body.

I'll probably also try plugging off the cold start valve fuel supply to eliminate that as a possibility.

Hi Beat,
it is quite easy to adjust this 'late-type' TPS, because it has the integrated 'stop-sheet'.
No electrical measuring needed for adjusting it (just for controlling the functions...).

Just loosen the screws so far you can turn the body of the TPS without great resistance.
First turn the body counterclockwise to the stop (by the screws).
Then turn it clockwise till you feel the resistance of the brown plasic arm touching the 'stop'.
Fix it in this position without turning it back. There has to be some
preload.

As you mentioned, this type of TPS uses the contacts you marked for cutting off the idle signal. The position of the 'wiper-contacts' doesn't matter, this is pre-adjusted in the PTS by the position of the 'stop-sheet'.

Regards
Norbert