DragStuff

i have a fast af meter, the dual type with sensors in both left and right collector.. when the ignition is on but the motor not running the reading on the meter jumps around dramatically, swings from 13 up to 21 afr.. this is with the motor not running.. does this mean the sensors are faulty or the meter itself.

Could it be a breeze blowing into the collector causing the weird readings? Never used one before, so don't know for sure.

doubt if its a breeze.. sensors are in my collectors and i have an exhaust behind them, exhaust is about 15 feet long with race bullets at the front.. it was sitting in the workshop at the time with no obvious draught going on..

check your ground it should be on the motor. sounds like you are getting RF. Your ground should have less than one ohm resistance. Also o2's will read and do strange things untill they are 600*.

jasper, what ground are you talking about,, engine has 3 grounds on it ,, dont the exhaust ground via the motor

zephyrc wrote:i have a fast af meter, the dual type with sensors in both left and right collector.. when the ignition is on but the motor not running the reading on the meter jumps around dramatically, swings from 13 up to 21 afr.. this is with the motor not running.. does this mean the sensors are faulty or the meter itself.

Whats the part number for your Fast product ? I've been looking at the dual wide band unit, with integrated data logging and playback and think I'm prolly going to pick one up. I'd be interested to know which one you're using.

I think you only have one on the monitor but I might be wrong. How many do you have? If one put it on the back of the cylinder or an intake bolt. This will give you the same ground the o2 has. Take the ohm meter one to that ground and one end to the o2 bung you should have less than 1 ohm. What gas do you run? Race fuel or fuel with led can do strange things. The odd changs sound like interference from something. Does fast have a sight with troubleshooting?

wikd, the part number is 170402, dual sensor..
jasper, will check the grounds as you suggest,, thanks for the help

Not so fast thank me if it helps and I just did not make alot of work for you.

checked the ground resistance and all seems ok.there is only one ground on the monitor.. have run race fuel in the past.. took the sensors out to free air test and they were sooted up,one read 9, very rich and the other was 21, very lean,,, cleaned them using brake cleaner and now the reading is down around 16 at idle.. will keep an eye on them for a few days

zephyrc wrote:wikd, the part number is 170402, dual sensor..
jasper, will check the grounds as you suggest,, thanks for the help

I'm thinking seriously of buy that exact unit - whats been your experience with it and how do you like it ?

wikd,, had a innovate lm1 before this and to be honest i wish i had kept it,, the only advantage with the fast is it uses dual sensors.. will probably go back to a lm1 as i think my sensors are on the way out, probably the race fuel i used on 3 occasions..