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Tuning With An Air/Fuel Gauge


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Yes, you want to bend the arm you have labeled #2. Leave #1 alone.

So by moving the actuation spot, you were able to get it out to about 3/4 full pedal? That's significantly farther then stock. Good luck with the numbers run. Hoping they look great across the board! 

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11 hours ago, 240260280 said:

I still have fond memories of the start of this project cruising in CO's cool purple Z with the AF sensor stuck in the back on the streets of Toronto base lining the L Jetronic. I wish we lived closer together.  Two mad scientists... and more than enough lathes!

You and me too, my friend!! I wish we could spend way more time together.

Maybe next time, it'll be at your place.    :beer:

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51 minutes ago, Captain Obvious said:

Yes, you want to bend the arm you have labeled #2. Leave #1 alone.

So by moving the actuation spot, you were able to get it out to about 3/4 full pedal? That's significantly farther then stock. Good luck with the numbers run. Hoping they look great across the board! 

Right, stock felt like MAYBE 1/4 or so, right?  Do you think I bent it too far?  I tried to bend it back in a bit but it wasn't holding that position and I didn't want to keep messing with it for fear of it breaking...

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9 hours ago, chaseincats said:

Right, stock felt like MAYBE 1/4 or so, right?  Do you think I bent it too far?  I tried to bend it back in a bit but it wasn't holding that position and I didn't want to keep messing with it for fear of it breaking...

Well from the A/F test results you had from before, I don't think you bent it too far. You'll know for sure when you get out onto the highway again and get some new numbers. If it's too far, you'll start to run lean at the high end of cruise before the switch closes and adds the WOT enrichment fuel.

I am a little concerned about the not holding position though... Do you think you fatigued the metal in the bend area?

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It’s actually called grape jelly pearl from kirker paints painted it myself. Depending on the light it’s very purple to blue to almost black. Sorry to derail back to regular conversation LOL


Here is another angle

7ad40b7585dded04253c85f70424d70b.jpg


Sent from my iPhone using Tapatalk

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2 hours ago, Captain Obvious said:

Well from the A/F test results you had from before, I don't think you bent it too far. You'll know for sure when you get out onto the highway again and get some new numbers. If it's too far, you'll start to run lean at the high end of cruise before the switch closes and adds the WOT enrichment fuel.

I am a little concerned about the not holding position though... Do you think you fatigued the metal in the bend area?

It seems to be holding the position I bent it at originally but in terms of bending it back up so WOT comes on earlier it doesn't seem to want to stay in that position...

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Posted (edited)
3 hours ago, Captain Obvious said:

Well, as long as it's holding position, lets hope it's OK.

So when do you get out on the road and see if that takes care of the richness at the high end of cruise?

And so my friends, we shut the book on this project.

I drove the car about 60 miles today and settled on around 14.9-15.1's tooth for cruising and man, I'm floored at this engine.  My other car is electric and I've never driven a gas powered car that runs as smoothly at speed as this does now.  Adjusting the TPS was the key but I was also running it too lean earlier today, as I felt I needed to rely on the WOT pin to get any sort of power out of it.  Richening the cruise out from 15.5 to 14.9ish really was the key to smell, responsiveness, smoothness and power (even before the WOT pin connects).  For reference, that was richening by 1 gear tooth this also changed WOT numbers from 13.3 to 12.2.

I can't thank you all enough - I hope this thread helps others in the future if they decide to tune with one of these gauges.

 

Some other observations due to leanness I believe:

- the car comes to operating temperature faster than before (but does not overheat)

- the car is harder to start now if the TPS is disconnected

Edited by chaseincats
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Excellent!! Glad to hear you're getting good numbers. And remember that you're getting those numbers from a completely open loop analog voodoo box that was designed 50 years ago by some genius from Germany.    :geek:

Seal up all the vacuum leaks, clean the electrical connections, get the fuel pressure where it belongs, tune it (as best you can with limited options) and put it on an otherwise healthy engine. Guess what... It can work! 

So what's the bottom line? What general numbers are you getting for idle, cruise, and WOT?

And also... in the end, you moved the AFM gear about 15 teeth from where it started? That's a lot. Do you think the AFM was messed with at some point in the past thereby changing the calibration? Or do you think that other things have just shifted so much that 15 teeth was required to bring it back to where it belonged?

I should have let you borrow my AFM adjustment tool:
P1140121.JPG

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Posted (edited)
3 hours ago, Captain Obvious said:

Excellent!! Glad to hear you're getting good numbers. And remember that you're getting those numbers from a completely open loop analog voodoo box that was designed 50 years ago by some genius from Germany.    :geek:

Seal up all the vacuum leaks, clean the electrical connections, get the fuel pressure where it belongs, tune it (as best you can with limited options) and put it on an otherwise healthy engine. Guess what... It can work! 

So what's the bottom line? What general numbers are you getting for idle, cruise, and WOT?

And also... in the end, you moved the AFM gear about 15 teeth from where it started? That's a lot. Do you think the AFM was messed with at some point in the past thereby changing the calibration? Or do you think that other things have just shifted so much that 15 teeth was required to bring it back to where it belonged?

I should have let you borrow my AFM adjustment tool:
P1140121.JPG

Absolutely agree and here are the final numbers:

  • Idle - 14.2
  • Cruise: 14.7-15.2 (depending on load)
  • WOT: 12.3

In the end, I moved to the lean side by 2 teeth from where the PO had it set.  I originally moved it 15 teeth back but that was undone once we discovered the TPS's WOT pin was to blame.

Edited by chaseincats
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Those numbers look great. I'm sure you're happy with that! I'd love to see how your engine dynos.

Did you ever put your CARB system back together? Are those numbers with the system connected using the valve in the cap?

Also, out of curiosity, can you see a distinct change at the upper end of cruise when the WOT switch closes and the enrichment kicks in?

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2 hours ago, Captain Obvious said:

Those numbers look great. I'm sure you're happy with that! I'd love to see how your engine dynos.

Did you ever put your CARB system back together? Are those numbers with the system connected using the valve in the cap?

Also, out of curiosity, can you see a distinct change at the upper end of cruise when the WOT switch closes and the enrichment kicks in?

No, I completely took the carb canister out of the picture.  It is still in the car/connected to the tank vent line but its vacuum hoses are disconnected.

Yeah, there is indeed a change when the wot pin connects it feels kind of like when turbo boost comes in on a turbo car.

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Well (in theory) the only change you would/should see with the CARB system connected is that it should run leaner at the low end of cruise because that's where you should be pulling air through the can into the manifold. 1/4 pedal maybe? Somewhere around there.

It should be a pretty tight spike as the ported vacuum that actuates the system cuts off pretty rapidly when the throttle plate isn't over the port hole.

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Posted (edited)
13 minutes ago, Captain Obvious said:

Well (in theory) the only change you would/should see with the CARB system connected is that it should run leaner at the low end of cruise because that's where you should be pulling air through the can into the manifold. 1/4 pedal maybe? Somewhere around there.

It should be a pretty tight spike as the ported vacuum that actuates the system cuts off pretty rapidly when the throttle plate isn't over the port hole.

The problem is that the main carb canister chamber connected to the large vacuum hose (the one that goes directly to the manifold) does not hold vacuum so there's a permanent vacuum leak there and then a slight one via the ported chamber so I just took it out of the picture.

Both chambers are supposed to be vacuum tight it seems - I tested this by spraying carb cleaner on the canister at idle and the rpms rose.

I can confirm later today if the mixture changes with it plugged in though.

Edited by chaseincats
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In the post-credits scene of this thread here are my 'a couple days later' thoughts/observations:

- I pulled a couple of my spark plugs just to see how they looked and they were QUITE grey indicating the car was running very lean.  Now, I don't know if they got like that when we were running off the charts lean earlier and if they will return to how they looked before this or not, but the car seems to be running well and the gauge numbers check out so I guess I'll ignore them?  Could my valve seats suffer if my plugs got toasted like that?

- My car has a delayed start which as previously noted got worse when we unplugged the TPS but will start immediately when I jury rigged the CSV to fire on every start (https://www.classiczcars.com/forums/topic/64824-very-strange-cold-start-valve-issue/) which I'd have though was indicative of running lean.  That said, I have a "Jacobs Electrical" coil/box setup (part number 380672) and the guy in the below video says if you have the wrong coil resistance (this one is correct) or if it is hooked up backwards you'll have weaker spark but the car will still run.  Since the PO rewired this part of the car for the ignition box, could I flip the wires attached to the coil posts or would I risk frying the box?  All the stock wire colors are of course wrong since all wiring comes from the box: 

Video will start at the appropriate time stamp: https://youtu.be/TlxiZXK06lI?t=647

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My thought is If the A/F numbers look that good, I wouldn't worry much about the plugs being light. I've heard (read on the internets) that the old method of reading plugs doesn't work so great on todays fuel using leaner ratios. Burns so clean that lighter colors often result. That toasty brown doesn't happen as much as it used to?

How many miles you have on the plugs? I guess if you're thinking it might be a relic of a previous situation, you could buy new plugs and have a fresh read.

As for the ignition box, I don't know anything about it. Hopefully someone else can chime in.

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20 hours ago, Captain Obvious said:

My thought is If the A/F numbers look that good, I wouldn't worry much about the plugs being light. I've heard (read on the internets) that the old method of reading plugs doesn't work so great on todays fuel using leaner ratios. Burns so clean that lighter colors often result. That toasty brown doesn't happen as much as it used to?

How many miles you have on the plugs? I guess if you're thinking it might be a relic of a previous situation, you could buy new plugs and have a fresh read.

As for the ignition box, I don't know anything about it. Hopefully someone else can chime in.

So I noticed today, one of my injectors is leaking now.  Could the increased head due to running leaner have been the final straw on the seal/hose (not sure which yet) causing it to give?

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LOL. Well there's your reward for tuning your mixtures in so well.

It's certainly possible that there was a slight change in engine temp that aggravated an "already close to failing" piece of injector hose, but I suspect it's more just dumb luck with maybe a little bit of Murphy's Law thrown in there just for comedic value.

And if one of them is leaking, I bet the other five aren't far behind.

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On 3/25/2021 at 8:44 PM, Captain Obvious said:

LOL. Well there's your reward for tuning your mixtures in so well.

It's certainly possible that there was a slight change in engine temp that aggravated an "already close to failing" piece of injector hose, but I suspect it's more just dumb luck with maybe a little bit of Murphy's Law thrown in there just for comedic value.

And if one of them is leaking, I bet the other five aren't far behind.

Well this is interesting, I bought replacement injectors since I'm sure they've never been changed and Rock Auto sent me brown-top 280zx turbo injectors.  Since those flow more I'm guessing I'll need to retune the car right?

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Well color of the plastic doesn't necessarily indicate the flow rate of the injector, but to answer the intent of the question...

Yes, if the new injectors flow more than the old ones, then you'll likely have to retune the system. But hopefully now that you have the other bugs and issues worked out, it should be a much easier process.

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On 4/1/2021 at 9:05 PM, Captain Obvious said:

Well color of the plastic doesn't necessarily indicate the flow rate of the injector, but to answer the intent of the question...

Yes, if the new injectors flow more than the old ones, then you'll likely have to retune the system. But hopefully now that you have the other bugs and issues worked out, it should be a much easier process.

I was sent 5 tan and 1 green injector from Rock Auto.  Besides being annoying, since it seems that the tan is the earlier year's 280 color and the green being later they should all be the same spec right and would be ok to mix/match (http://www.atlanticz.ca/zclub/techtips/injectors/index.html)?  The injector hole on the bottom of both are the same size so that should indicate the same flow rate, right?

IMG_7612.JPG

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