Air Fuel Mixture
04-30-2008, 05:23 PM
#16
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Join Date: Jul 2004
Location: SE Michigan
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Thanks everyone for the advice.
I replaced the hoses to the WUR today and did some quick runs.
At idle I bumped it up to 10.9AFR and I am now at 13.5 cruising (no boost) and 11.0 - 11.8 on boost. Still a bit rich.
The hoses must have been bad.
I am going to try and adjust the idle to 12.0 at idle and see what happens on boost. If I can get to it tonight I will. (kids first)
I replaced the hoses to the WUR today and did some quick runs.
At idle I bumped it up to 10.9AFR and I am now at 13.5 cruising (no boost) and 11.0 - 11.8 on boost. Still a bit rich.
The hoses must have been bad.
I am going to try and adjust the idle to 12.0 at idle and see what happens on boost. If I can get to it tonight I will. (kids first)
05-01-2008, 02:39 PM
#18
Burning Brakes
Join Date: Apr 2006
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In other words, if a person were to set the idle via the mixture screw to deflect the control arm more and increase the fuel injected, to even an eye-watering rich exhaust cloud, it would not ensure that under boost the AFR would be correct. Many people run their idle CO pretty high (close to 3%, myself included) in an attempt to ensure a nice rich mixture during boost - and it probably helps somewhat at the expense of fuel economy- but the best solution is a properly operating WUR and/or an adjustable Brian Leask-ish WUR - especially if you're playing around in the upper stratosphere of boostdom.
05-01-2008, 04:21 PM
#19
Racer
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The CO or idle mixture adjustment screw has very little effect on AFR above idle. The faster the engine runs the less effect it has.
Raising control pressure leans out the AFR and also raises the fuel return line flow to the gas tank while less fuel is sent to the injectors by the fuel distributor.
CIS can be confusing in the beginning and takes a little while to understand everything thats going on.
You have to get the CIS fuel pressure gauge along with wideband AFR gauge to help find a baseline and readjust all the running paremeters as you adjust it.
If you get the adjustable WUR from Brian Leaske he is very helpful through emails or phone after you get it on the engine and start adjusting it.
Raising control pressure leans out the AFR and also raises the fuel return line flow to the gas tank while less fuel is sent to the injectors by the fuel distributor.
CIS can be confusing in the beginning and takes a little while to understand everything thats going on.
You have to get the CIS fuel pressure gauge along with wideband AFR gauge to help find a baseline and readjust all the running paremeters as you adjust it.
If you get the adjustable WUR from Brian Leaske he is very helpful through emails or phone after you get it on the engine and start adjusting it.
