gas anaylsers??

[Supercharged Nat]

has anyone ever used one? and how useful/ acurate are they. ive been looking at the gunson ones but i dont want to commit to buying one until i know itl be ok/ suitable...

 

so your thoughts please. while im here, anyone know where i could pick one up with out spending a huge amount?

[Tom]

mate the easiest thing to do is get a lambda probe (not a planar/wideband) weld a boss in your exhaust and fit it, pref as close as possible to the engine.

 

then get your multi meter and put it accross the 2 signal wires - run the engine and get it hot - perfect burn is 0.45v, higher than this is richer lower is weaker.

 

to ensure its working give it an air leak (servo pipe off) or continuously tap the thottle to richen it up and you should see the voltage move.

 

a bit crude but it should work fine

 

n.b you may have to power up the heating element in the sensor if you're trying to read it at idle. but don't do it until the exhaust has warmed it up a bit cos it will break it otherwise (thermal shock)

[Supercharged Nat]

hmm good thinking. whats the difference between a wideband and the probe you mention? how would i know what one i have?

thanks.

[Tom]

A wideband probe is a whole different story - a normal probe (jump type) will tell you rich or lean but not by how much.

 

A wideband sensor is much more sensitive sensor and the readings are measured in current and voltage on 2 seperate scales - i'm not gonna go into the full workings of it cos it will just confuse you (it confuses me) - it is a much more complex probe and by itself it will not tell you anything

[Supercharged Nat]

ok thats cool, but i really want to know the Co content of the emissions, the lamda doesnt seem to be able to do that? ive already got a lambda sensor and air/fuel ratio gauge fitted in my car but the Co can vary from 2.5% and 5.5% with out the airfuel ratio gauge showing a different reading.

 

thats why i was thinking along the lines of the gas anaylsers?

[Tom]

at idle? thats odd, especially as the sensor's not seeing it. Does the afr gauge change when running?

[Supercharged Nat]

yeah the gauge changes when driving. just at idle, i can vary the mixture screw enough to pass or fail an emissions test (mot) but the gauge will stay on the same led.

 

what would be handy is a reference of voltages to afr's. you say .45v is perfect burn- that being 14.7:1??

 

i will check the wiring if the gauge/sensor to make sure it all ok, but its been like that sice i installed it. (it should be noted that if i turn the mixture screw right in - so the engine wont idle hardly, it will go round to lean)

 

But like i said, i would like to know the Co content of the exhaust and the gauge doesnt seem to be able to provide that. i originally fitted the gauge to make sure the carb wasnt leaning out top end or mid range etc (due to the blower ive fitted). if i could use to give a more accurate insight as to whats going on under different load conditions that would be good.