Tuning With An Air/Fuel Gauge

[Captain Obvious]

I just published my book report in that other TPS thread.  

[chaseincats]

26 minutes ago, Captain Obvious said:

I just published my book report in that other TPS thread.  

Awesome, I'll respond in there, thanks!

Brief update - I didn't drive the car at all this past weekend as I left my gauge powered up when I scampered up the stairs to write the previous numbers post which subsequently drained my battery when I went to start it a few days later lol.

I got the car going in the driveway today and noticed that with the car set as lean as it is, my idle speed dropped to around 450, so I brought that back up to 800 and the idle is sitting at around 14.7.  The idle air bypass screw is indeed turned all the way in and the only way to lean out the idle further is to retard the black gear.  I think at this point, that is just how it will have to sit.

When playing with the throttle, I noticed in cruise mode it will sit in the mid 15s and pushing the linkage to when the WOT pin connects on the TPS, brings the gauge to the mid 12s which all look really good (although when the car is under load I'm expecting the numbers to change a bit).

That lead me to the TPS configuration question because it seems that the cruise mode leanness only lasts a short amount of pedal travel - maybe only an inch or so.  I can check tomorrow at what rpm the WOT pin connects in the TPS if that information would be of some help?  I attached a picture of my TPS but its in a different orientation because of the weber throttlebody.  The bottom pin in the WOT pin - should I bend it down somewhat?

Edited March 17, 2021 by chaseincats

[Captain Obvious]

I suspect the reason for the change in your numbers are simply from different engine temperatures. If you tuned it all nice and warm and then shut it off and now you notice that the numbers are way different on a cold start, I bet that's what's going on.

I talked about it a little in the TPS thread, but to bring some of that here as well... I don't think you can apply any meaningful info to the WOT setting of the switch unless the engine is under load.

I haven't connected an A/F gauge to my car, but my seat of the pants "feelings" about the Bosch L-Jet system after messing with it some:

1) The slope of the enrichment from cold to warm is too steep. In other words, it's too rich when cold. You could set it "correct" when cold, but then it'll be lean when warm.
2) The impact of the air temp sensor in the AFM is too high. Sort of the same thing as above. When the incoming air is cold, it runs rich.
3) I think the WOT contacts close too early and the car runs too rich when they do.

The bottom line is it's an analog system designed in the early seventies when gas was cheap and performance was higher priority. No computer, no feedback, and no tuning features.

I think the numbers you were getting earlier in this thread are fantastic and I think you might be trying just a little too hard with the RCH adjustments of the throttle switch?    Set the TPS using the 1400 RPM method, and get idle and cruise working again. Then lets see what the WOT numbers look like. Maybe we can entertain some modifications to the TPS to close the WOT contacts deeper into the pedal?

[chaseincats]

1 hour ago, Captain Obvious said:

I suspect the reason for the change in your numbers are simply from different engine temperatures. If you tuned it all nice and warm and then shut it off and now you notice that the numbers are way different on a cold start, I bet that's what's going on.

I talked about it a little in the TPS thread, but to bring some of that here as well... I don't think you can apply any meaningful info to the WOT setting of the switch unless the engine is under load.

I haven't connected an A/F gauge to my car, but my seat of the pants "feelings" about the Bosch L-Jet system after messing with it some:

1) The slope of the enrichment from cold to warm is too steep. In other words, it's too rich when cold. You could set it "correct" when cold, but then it'll be lean when warm.
2) The impact of the air temp sensor in the AFM is too high. Sort of the same thing as above. When the incoming air is cold, it runs rich.
3) I think the WOT contacts close too early and the car runs too rich when they do.

The bottom line is it's an analog system designed in the early seventies when gas was cheap and performance was higher priority. No computer, no feedback, and no tuning features.

I think the numbers you were getting earlier in this thread are fantastic and I think you might be trying just a little too hard with the RCH adjustments of the throttle switch?    Set the TPS using the 1400 RPM method, and get idle and cruise working again. Then lets see what the WOT numbers look like. Maybe we can entertain some modifications to the TPS to close the WOT contacts deeper into the pedal?

Gotcha - I originally set mine using the 1400rpm method and haven't fiddled with it yet - but now I know not to!  Ya I was thinking about just bending the lil WOT contact arm a bit but I should have new numbers for you Thursday or Friday night before I fiddle wit it.

My reasoning for wanting to bend the WOT enrichment pin would be that it seems to think freeway driving (3500 rpm) counts as WOT which seems a bit silly to me, no?

The adventure continues haha.

Edited March 17, 2021 by chaseincats

[240260280]

The TPS has a switch at both ends but only one toggle to rotate....so if  you adjust for the the idle enrichment to drop out earlier, you also cause the WOT enrichment to come in earlier, they both are affected..... you really need an independent adjustment for each of the two switches. It can be fabricated.

Edited March 17, 2021 by 240260280

[siteunseen]

8 minutes ago, 240260280 said:

The TPS has a switch at both ends but only one toggle to rotate....so if  you adjust for the the idle enrichment to drop out earlier, you also cause the WOT enrichment to come in earlier, they both are affected..... you really need an independent adjustment for each of the two switches. It can be fabricated.

I bet that's why my guy bent the vanes with his fingers. 

[chaseincats]

3 minutes ago, siteunseen said:

I bet that's why my guy bent the vanes with his fingers. 

Can you pop the cover off and take a picture of the arm spacing?  That would be awesome

[siteunseen]

[chaseincats]

2 minutes ago, siteunseen said:

Wow ya that is a huge difference compared to the pic I put up last night.  I'll get some numbers/rpms for you near the end of the week and then I'll do some bending.  Any idea what RPM you have to hit before it connects to the WOT tab?  I set mine using a multimeter on the bottom two pins and twisted the sensor so that when it got above 1400 the contacts would lose continuity.

Edited March 17, 2021 by chaseincats

[siteunseen]

We have some bad weather coming in the next few days but maybe this weekend I could hook up my timing light that shows RPMs and tell you something then.

[chaseincats]

Just now, siteunseen said:

We have some bad weather coming in the next few days but maybe this weekend I could hook up my timing light that shows RPMs and tell you something then.

Sounds great, thanks!

[siteunseen]

Looking at my picture I can see the middle vane is twisted a little. Wonder if that's what he did for some reason?