Tuning With An Air/Fuel Gauge

[chaseincats]

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?

[Captain Obvious]

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.

[chaseincats]

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?

[Captain Obvious]

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.

[chaseincats]

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?

[Captain Obvious]

Well regardless if they flow the same, that's pretty annoying. The color may not matter, but on my engine, I would want everything to at least match.

So I have no idea if the size of the opening on the bottom is the only thing that would affect the flow rate. I kinda doubt it. I suspect there are other internal geometry areas which could affect the flow rate too. In other words... Just because the hole in the bottom is the same, I wouldn't assume they flow the same.

You could test them to compare the rates:

[240260280]

[chaseincats]

2 hours ago, Captain Obvious said:

Well regardless if they flow the same, that's pretty annoying. The color may not matter, but on my engine, I would want everything to at least match.

So I have no idea if the size of the opening on the bottom is the only thing that would affect the flow rate. I kinda doubt it. I suspect there are other internal geometry areas which could affect the flow rate too. In other words... Just because the hole in the bottom is the same, I wouldn't assume they flow the same.

You could test them to compare the rates:

Good point about them matching regardless of flow rate.  I just took a look at the bottoms to compare what was on there (left) and the Bosch ones I bought (right) and they look way different.  Are the ones that were on there for the turbo or just some weird reproduction maybe?

[240260280]

Effective fuel hole diameter  in carbs and fuel pressure determine fuel flow. I think it is the same for injectors.

Fuel pressure in injectors is relative to manifold air pressure rather than absolute air pressure otherwise  a negative pressure in the manifold would combine to  "suck extra fuel".

[chaseincats]

And here is the end of the post-credits scene for this feature-length thread: after 3 separate mismatched injector shipments from rockauto, I finally got 6 matching ones and sent the rest back.

Took the car out today for the first time and interestingly enough, with the new reman injectors, I needed to richen the car a bit to get it to our numbers.  I expected the old injectors to have had a diminished fuel output due to age but who knows.

[siteunseen]

Fj707 x 6 for me.

[Captain Obvious]

11 hours ago, chaseincats said:

after 3 separate mismatched injector shipments from rockauto, I finally got 6 matching ones and sent the rest back.

Woof. I suspect those old injectors had been knocking around in boxes for so long, they probably started consolidating them and mixed them up.

Glad to hear you're back on the money!