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Hi all, I am having trouble with a dual fuel 280ZX/L28 due to gas misfiring/crossfiring which is giving my airflow meter ****. SO with only one spare left I decided to find out what was wrong with the ones that are getting blown up. I find it is the cog wheel inside that is being blown back off the ratchet and making the spring tension too weak. I ran one up and slowly adjusted the screw tension on the spring until it idled nicely, however I read on the L-Jetronic Bosch sites that it is critical to set this spring tension right on. So does anyone have a bench test procedure or some figures or even technical web pages on the specific airflow meter fitted to the Nissans and not just the generic Bosch box. I have played with the cog wheel and fully understand how the tension sets the coarse position of the flap/vane and I have brought it into range of the fine screw adjuster on the mixture control...Now the car runs and starts on both fuels LPG/ULP and it seems to have normal acceleration so I am probably in the ball park, but it would be nice to hear it from someone else. I dont believe the crap about NOT USER SERVICEABLE and YES I might be running too lean or too rich and will dyno the car soon , but just thought I would ask the experts. Also has anyone fitted a hot wire mass airflow box by any chance in place of the mechanical potentiometric type or any aftermarket EFI systems?



Post Edited (Oct 16, 7:53pm)
 

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If it runs good, you have it adjusted right for your car. There is no magic tension that is perfect for every car, these are way too old for that to be the case anymore! Just set it where it runs good and move on..
 

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Check the AFM info in tech tips below

You did fine. Now that you are in the ball park, just read your plugs and measure mpg to finalize tweaks


The AFM and stock EFI system is a crude approximation just slightly better than a carb.

You can not tailor it for the full rpm spectrum thus you must compromise

If you want to optimize fuel delivery from idle to cruise to WOT, you need something like magasquirt.

I get max power if I set the AFM for more fuel. This gives me tons of fun but 19mpg and darker plug deposits. If I lean it out, I get clean plugs and 21-23mpg and acceptable performance.

I am going to emperically test NGK 5 vs NGK 6 plugs later today.



Post Edited (Oct 17, 12:58pm)
 

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Blue, you hit it about right. I have tinkered with my AFM a little, and found that if I lean it a tiny bit, I result in better gas mileage, as in I got ~25 on a trip recently to Wilmington N.C..My main reason for leaning it was a slight bit of smoke during hard acceleration. However, I found the power to be slightly off from what it was although still quite acceptable.

I theorize that over time the spring in the AFM has weakened a little, thus creating a slightly rich condition. Where it was when I started was where it was factory sealed, never been touched.
 

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I found my turbo was running like it was really underpowered. It had a wondering surge and drop of about 400 rpm when stopped in gear. I had Jason show me how to adjust it. I installed new plugs, run out to his house 50 miles away. He pulled 1 plug and it was wet! I backed off on the meter 7 notches. (turned it to the right) Talk about a surprise! It runs like it has another engine in it! Plugs look good too. Thanks Jason! Grasshopper tought teacher!
 

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Oh, I see "Non-US Spec" here...

Sounds like a Down Under vehicle...

The Z31 Conversion would give you the massflow situation you desire, but is your ECU a specifically calibrated LPG component. I know Taxis in Japan were LPG, so maybe that's the setup, and you would have to find the matching Z31 style LPG ECU for your conversion. Or is this some sort of bolt-on conversion kit? I mean, Gas Injection is pretty advanced for the old bosch setup on these cars. Honkin' injectors to be sure.

The Megasquirt Board has had some guys convert down under for LPG.

Good Luck in the search...
 

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Yeah... what you want is, basically...

that the flap is wide open around 3500, giving you "full fuel" and running on the preprogrammed ECU map from there to redline.
 
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