A few Questions about AFM

[sblake01]

(Bugs float.)

Makes me think of the early 70s VW ad that said ''The VW will definitely float, but it will not float indefinitely.''

[roanokejim]

Yeah right, thanks for your information. I also encounter the same.

[sblake01]

Yeah right, thanks for your information. I also encounter the same.

Spambot from Philippines:

http://www.stopforumspam.com/ipcheck/203.87.176.21

[sparrow6190]

jeeze, everyone always has these crazy ideas why, and how things work.

the idle bypass screw controls how much air goes past the flap, and not through it, thus at idle you wont have much air going through so the small hole has a great effect, and it DOES effect your entire mixture all the way through, it is a BYPASS, as it it bypasses the flap, the more you have it closed the richer your mixture is because it is actually being forced through the flap.. so yes, its not just as simple as "just idle"

I'm not sure if it was answered yet, but it just is an old car with an old mechanical electric fuel system, STUFF GETS OLD.... but all you need to do it take your AFM cover off, losen it counterclock wise around 4 teeth, after 30+ years you people REALLY should expect something like that.... I like my AFM idle adjustment screw set at about 2+ full turns out from bottom now.

This is the only real way to richen up your mixture all the way through, unless you get a potentiometer and hook it in line with your temperature sending unit.

then you need to set your idle bypass and idle adjustments until it pulls smooth all the way from stop to 6k+.. you can use common sense to a point but an A/F meter would be amazing...

I absolutely love(HATE) how everyone thinks of these outlandish ideas, so intricate and silly when its always something so simple, like a clogged fuel filter or crimped line, an old spring, a lose connection or a broken wire that would have been easy to trace.

After upgrading to headers, 2.5exhaust, xr3000 ignition, drilled t-bar with lighter springs and no vacuum, and lots of mechanical advance this is what I needed to do, and now its a total beast, for cheap-o-hell too...

Edited June 26, 2011 by sparrow6190

[240260280z]

jeeze, everyone always has these crazy ideas why, and how things work.

Yes, and that was back in mid-April; ~ 10 weeks ago.

With respect to the bypass screw affecting a/f ratio over the whole range, you should recheck your claim. Its effect greatly diminishes as the flap opens.

Edited June 26, 2011 by Blue
I felt like it

[FastWoman]

jeeze, everyone always has these crazy ideas why, and how things work...

I absolutely love(HATE) how everyone thinks of these outlandish ideas, so intricate and silly when its always something so simple, like a clogged fuel filter or crimped line, an old spring, a lose connection or a broken wire that would have been easy to trace.

Sparrow, I think it's extraordinary you're calling people stupid and silly after only 12 posts (not that other posts of yours aren't helpful). This isn't that sort of forum. We're a bit kinder and gentler here. People here almost always offer constructive suggestions and solutions here without getting insulting about it. We have people here of all knowledge and skill levels, from rank beginners to Z restoration professionals.

Argneist's problem, BTW, has already been solved. It was a hole that eroded between the EGR inlet on the intake manifold and the main body of the manifold, resulting in LOTS of exhaust gas bypassing the EGR valve and flooding/killing the #4-#6 cylinders. IMO, that's a bit less than obvious. In fact I've never heard of that happening on a car before.

I have to give this beginner a whole lot of kudos for diagnosing this weird problem (with a bit of help from his friends on this forum), when a few professional mechanics thought there was nothing wrong. (Note: every other cylinder was missing in the firing sequence, so the exhaust beat was steady.) I mean, we're talking about a guy who at one time was terrified to turn a screw, for fear of hopelessly destroying his car. (Sorry, Argneist! ) And here he/we accomplished something the pros in his area didn't, because they didn't have faith in his car, dismissing it as one of those bumbly old antiques that "just runs like that." I think that's what this forum is all about.

Edited June 26, 2011 by FastWoman

[sparrow6190]

Yes, and that was back in mid-April; ~ 10 weeks ago.

With respect to the bypass screw affecting a/f ratio over the whole range, you should recheck your claim. Its effect greatly diminishes as the flap opens.

yes it effects the entire range not just the idle entirely

[Zed Head]

sparrow, I think you missed the point (actually several points). The air bypass volume is large in comparison to the volume of air passing by the throttle blade at idle. But it's tiny in comparison to the volume of air passing by the throttle blade at higher RPM.

Check out this site - www.zcar.com . It will probably offer you more enjoyment, and fit your style better.

[sparrow6190]

I was running lean at top, and much better at lower rpms IF i tightened the bypass, because it has a great affect at idle and has less effect for the more air that is actually being pushed through and metered at high RPMS with high air flow. So all i had to do was turn the spring CCW inside the afm about 4 teeth or so, then open my bypass more for a richer mixture at idle and up.

not really... you are just insisting that I don't understand.

it was running lean, at choking out. im about to install a potentiometer inline with the temperature sending unit too because of the mods ive done

Edited June 26, 2011 by sparrow6190

[sblake01]

Sounds more like you are working within your own logic...........

[argniest]

Im back...for a moment in time. I have only good news and more good news since my last postings.

I have increased the gas mileage from 7 to 8, to 14, to 18, and now 25 mpg on the highway going 65 to 70 mph. That was just a few days ago. The car is purring I swear!....Besides the MASSIVE intake leak that was inside the intake system and almost impossible to know about (even for people who have worked on these cars for 30 years and didnt remember this problem could actually happen, but then later remember oooooh crap thats right the inside of the EGR housing can actually be eaten away by the corrosive exhaust, causing the massive air intake leak which completely screwed up everything!!!! with the engine and sent me on a long wild goose chase, but taught me so much and I ended up replacing everything from the gas tank to the fuel injectors and everything in between. And I was a person who had never touched a car before. It has been such a pleasure getting to learn how to work on cars, and have it be a Z car)

Oh well, I have been working on many little things on the car, and some other important things like the TVS switch and the AFM. My TVS switch was bad and misconfigured. I had a spare one I bought, so I was comparing the two. Well once I got it adjusted, my gas mileage got somewhat better. But all along, I had been testing it with an Innovate AFR computer exhaust sniffer. And learning and watching the AFR's. Now I know a LOT more about how all these things are linked together.

And then I turned my attention to the AFM. I took the black plastic cover off, and adjusted it clockwise about 5 teeth the first time, and then two more teeth CW. And that is how it is now. And The car is driving better than ever!!! Its sounds good, it feels great, its getting 25 mpg on interstate...and I can GO FAST as I want. It gets 18 to 20 mpg in town depending on how its being driven.

I could write a lot more....but I just wanted to follow up with this great news. It took me a while to learn all this stuff, and how they were all related, and make little by little changes to the idle screw, AFM bypass screw, the TVS switch and the AFM wheel/potentiometer/spring. I am very very happy about how the car drives now.

I can take it up to 5500 rpms in any gear (wellllllllllllllll I havent done that in 5th gear until I get on a race track).

After fixing the massive intake leak in the EGR housing, all these other things needed to be dealt with one by one. Many other things were checked/dbl checked...but those things I mentioned are what needed the adjustment.

Brand new the 78 was supposed to get 28 mpg and 18 mpg in town (I am just going by the original gas mileage sticker, because I got all original paperwork with my car). So for an engine that has 187,000+ miles on it now, my performance and drivibility, and mpg, and air to fuel ratio's are telling me that my engine is about as good as its gonna get!!!!!!!!!! I am very happy with it, drive it every day, and many long trips crusing at night, even on a 300+ mile trip a few weeks ago to see an old friend. Was beautiful trip beautiful vblue sky day!

Also, I meant to mention, that one of the drivibility problems was that the engine was surging/stalling in the higher rpms. At first maybe around 3500, then 4000, then 4500, etc

But, as I adjusted all these things as best as I could, those drivibility problems went away. They are history now as best as I can tell.

Now I can just barely step on the gas and the car wants to go!!! And when I shift into higher gears, I feel it wanting to immediately go faster. It was NEVER like that before. So yeah, dialing all those things in transformed the car. Powering up hills is no problem in 1,2, and 3rd. I love going up huge hills in second gear now. I can feel the torque of the engine pushing and pushing, and plenty more to give......

Now I want another, that is in worse shape and needs a lot of work, that is cheapo, that I can take my time and just restore it from ground up. Doesnt matter how long it takes...because I have my blue baby to drive anyway.

I could have never ever done what I did, without all the kind words, and patience, and help from people here, and many others in my life as I mentioned in my posts. Thanks Z universe!

I cant even believe how much I have learned. I know I got a million miles to go, but from where I was at last year, I feel like I have come a million miles to get here. And now many things seems sooooooooooooo simple to me.

Edited July 18, 2011 by argniest

[240260280z]

You learn from doing and you learned a lot! I am very happy for you...your are in the realm of Bosch L-Jetronic experts Now go tune a Porsche, BMW or Alpha from the 80's and strut your stuff!

Alpha

BMW

Porsche

Edited July 18, 2011 by Blue