Jump to content
Welcome Guest! Please read more information about our club!

A/F ratio for L28

Stanley
Stanley
in Carburetor Central

Featured Replies


comment_537636
9 hours ago, 240260280 said:

Aim for 14 at idle  (richer is smoother idle but it stinks)

Aim for ~15 to 16 at cruise

Aim for 13 at WOT  (12.5 to 13.5 range is fine)

Right on the money .

Damn AFR gauges are a great tool but you find yourself about having a wreck watching the damn thing and obsessing over it. I say for the most part these engines sound better and run better a tad rich - but might just be me. 

    • Like 1
    • Author
    comment_537637

    Thank you. Once the tune is right I plan to remove the sensor so it doesn't get cooked, and then put it back briefly twice a year when the mix needs adjustment, when the weather turns cold and again in the summer. Not sure I'll really do that but it's the plan. When the car was running rich it was noticeably faster on cold days. 

    comment_537652

    Use just about anything but Innovate. Horrible quality control. They go through 4.9LSU sensors like crazy. 

    PLX and Zeitronics are  is very good,. So is 14PointSeven. Aem is pretty good, especially the new X series.  

    http://speed.academy/aem-x-series-wideband-afr-controller-tested-fastest-responding-wideband-confirmed/

     

    Edited by Chickenman

    comment_537653

    Batch fire requires a slightly richer idle than sequential. 13.8 to 14.0 for a stock Cam. Cams with more overlap require a richer Mixture yet 13.5 range usually works well. Bigger cams also require more ignition timing at idle. This is due to the  EGR caused by the larger overlap. EGR contaminates the idle mixture with exhaust gases and the Air/Fuel mix burns slower. So more timing required. 

    Cruise AFR's  leaner than 15.0 can be difficult unless you have a very strong ignition system. ( Edit :) The stock 280Z Trignition Boxes are too weak to run that lean. You need big spark gaps and lots of current. The 280ZX matchbox distributor is very good on Normally Aspirated engines. With that and plugs gaps of around .042" to .045" you can run 15.0 or leaner at cruise. 16.0 to 1 at Cruise will normally require a CDI ignition Box such as Fast ( Crane Fireball H_6 ) or MSD digital 6. I do not like recommending MSD 6AL boxes ( Analog box )  due to reliability issues. MSD = My Spark Disappeared

    This chart  from MS is not bad as a reference point. Obviously for Normally Apirated only. I like to run the 1500 rpm's a bit richer than Stoich, as it helps with light throttle transitions ( Tip-in ) Scott Clarke has a You Tube video on Tuning Acceleration Transitions . So does Andy Wyatt from Adaptronics and Andy Whittle at MS  . Both Andy's have excellent Tuning channels on You Tube.

    AFR Chart excellant.jpg 

    Edited by Chickenman

    • Author
    comment_537908

    Digital gauge or analog ? I was looking at some on YouTube.  Digital sort of irritating as the numbers  seem to jump around a lot. Zeitronics looked a little better than the others in that respect. But with analog meters (Only saw AEM, autometer and stewart-warner)  the needle jumps around a lot. Maybe the needle mechanisms are cheaply made. I like the look of analog better but that's a minor issue.

    Edited by Stanley

    Create an account or sign in to comment

    Go to topic listing

    Important Information

    By using this site, you agree to our Privacy Policy and Guidelines. We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.