quick afr question

[HULK]

hey peeps, I have a digital afr gauge,

right when i'm say driving around town, my gauge always goes down to between 9 and 10 when i squirt the throttle,

is this normal??:scratch:

[Markey Mark (BD)]

No on part throttle it should be around 14 - 14.5, on WOT (wide open throttle) it should be around 12.0

Whats the spec of your carb mate?

[Jimmy_GTT]

hey peeps, I have a digital afr gauge,

right when i'm say driving around town, my gauge always goes down to between 9 and 10 when i squirt the throttle,

is this normal??:scratch:

If your accelerator jet squirts in than the afr will go down between 10-11 for some seconds. It is normal.
Under other conditions what Mark has written.

[HULK]

standard carb apart from 130 main jet and 100 a/c

running 18psi

wot I get 11.2-11.4
normal driving (motorway) is around 13.5-14

just every thime i lightly press the throttle, ie squirting fuel down the venturi it all ways blips down to around 9.5 until i take my foot off the loud pedal.

another thing......everytime i turn off the ignition/engine i get a HUGE backfire out the exhaust!:scratch:

[tiff_lee]

Isn't 11.2-11.4 a little too rich for WOT? Just from reading the article on the site it states 12.1 for engines under 20 psi and on 'higher boosted' engines aim for 11.7.

That in conjunction with the additional fuel from accl pump jet causing it to reach 9.5 perhaps? and then backfire due to excess fuel .....

Just spitballing here

[HULK]

I know its very confusing, the backfire is obviously caused by overfuelling but dont know where its coming from, it aint dribbling down the carb

also i can turn the boost up to 22psi on the same carb (only running a k-tec 180 )and still only get a 11.9- 12.2 on wot

[tiff_lee]

I know its very confusing, the backfire is obviously caused by overfuelling but dont know where its coming from, it aint dribbling down the carb

also i can turn the boost up to 22psi on the same carb (only running a k-tec 180 )and still only get a 11.9- 12.2 on wot

If you had it set like that does it still drop so low when accelerating and does it still back fire?

[HULK]

If you had it set like that does it still drop so low when accelerating and does it still back fire?

still drops low yes but the backfire is just a mellow pop at that boost

[Brigsy]

130 main is causing the rich part throttle.

Id drill the 2nd stage out a bit, stock main & play with the a/c size, the fuelling will be better across the boards & more mpg. Lean her off a bit on WOT too for more power.

[leesaunders1981]

whats the best size to drill the second stage out too????

[James5]

whats the best size to drill the second stage out too????

You do it in stages of .5 increments dependant on your afr readings until you get an afr at WOT of around 12.1ish :D