Engine/Transmission (1994 - 1998) will star wheel adjustments affect EGT's

[jeepcjsrule]

From what i understand adjusting the star wheel twoard the engine provide more fuel at low boost and causes smoke but i havent sen any info if it will effect egt's?



my truck is stock for know but i do have egt and boost guages, installed them last weekend.



any way just curious before i start fiddling with the truck!

 

[M Barnett]

I'm sure somebody here knows more than I do about it, but seems like it may cause the egt's to rise quicker.

Michael

 

[Blakers]

Does the star whell have any bearing on anything once you have boost? I'm sure someone can answer this.



I have not adjusted the star wheel or AFC housing yet, but I think they effect mostly your pre-boost time. My highest EGTs are when she's pulling hard and I have good boost.



Blake

 

[Deezul1]

It shouldnt because the star wheel allows more fuel with less boost at low RPM and doesnt effect fueling at top end as far as I know.

 

[Reb.B]

it could raise egt's faster, but not enough to notice or harm anything, it's when u are on the plate that the egt's need to be in check. the only time the star wheel could effect egt's is on a really hopped up vehical, and u have the vallet switch on and the star wheel is full forward, then it could become an issue.

 

[drees1]

The star wheel sets the preload on the AFC spring. The spring works against a diaphram that has the boost line on one side. As boost builds the spring compresses and allows the rack to give more fuel. This system prevents excess fuel and smoke delivery before the air is there in boost to burn it. At higher boost levels the AFC link should be retracted and the rack should be on the fuel plate. But that is not always the case. If the system is not adjusted correctly, and you have a big HP plate, then you could ride the AFC for quite a ways up in the rpm range before you get on the fuel plate limit.



So to answer your question, the star wheel can effect egt, particularly in low rpm high load (1500 - 1750+) where boost may not be built up yet to allow full retraction of the AFC control. You can experiment to see what happens. It depends on how your truck is modified and where in the speed range you are concerned.



I have my truck set up for minimal smoke right now and I tow heavy in double overdrive a lot. If I lug it to 1600 or so my EGT is up to 1,100 or so and boost may only be 10 - 12 psi. At that point, I doubt I am on my fuel plate, rather on my AFC link. So, adjusting my star wheel for more fuel may raise my EGT. But, in doing so I would get more boost, which would compensate somewhat, but be smoky. Clear as smoke!!



Think of it this way. The maximum rack travel during operation is limited by 2 features in the pump. The plate controls max fuel as a function of rpm, and the AFC controls max fuel as a function of boost. Either plate or AFC can be the limiting factor at any time. The AFC is generally limiting on the low end as boost builds with speed. The governor can request rack travel from idle to the lesser of either the plate limit or AFC limit.



Doug Rees