Mixture question

[jdbubb at verizon.net (Dan Bubb)]

Yes, but......
As an example, lets say the lift of the control plunger is 1mm at idle and 10mm at WOT.
You adjust the mixture screw to move the plunger up .1mm. The idle AFR is changed by 10%. The WOT AFR is changed by 1%.
I have no idea the actual amount that the control plunger is open or moves from idle to WOT, but I imagine the numbers aren't too far off.
So, considering that the idle adjustment is constrained to be in the range where the engine will actually idle, the amount you can change the WOT high RPM AFR is pretty minimal.
Dan


From: "Brett Van Sprewenburg" <brett@netacc.net>
Sent: Tuesday, May 23, 2006 11:59 AM
Subject: Re: Mixture question


> 
> On May 23, 2006, at 11:05 AM, Drew Mac wrote:
> 
>> On 5/23/06, Dan Bubb <jdbubb@verizon.net> wrote:
>>>
>>> It's long been my understanding that adjusting the mixture on CIS
>>> mostly affects idle and has less and less of an effect as the fuel
>>> metering plate moves higher.
>>
>>
> 
> Yes, this is the case (idle mixture affected more so then high rpm
> running).  Here's an excerpt from an email I wrote back in December
> of 2000:
> 
> From the Bosch Fuel Injection book chapter 5, section 2.1 "Mixture  
> (CO)":
> 
> "To ensure that the basic air-fuel mixture is in the best range for  
> emission
> control, all continuous systems have a provision for mixture adjustment.
> Although this adjustment is made at idle, it affects the basic sensor- 
> plate
> and control-plunger relationship over the entire range of operating  
> conditions.
> For a given lift of the sensor plate, the lift of the control plunger is
> adjusted to change the amount of injected fuel, and therefore the air- 
> fuel
> mixture."
> 
> 
> Remember this is a mechanical bias adjustment that changes the  
> relationship
> of the air flow plate to the fuel metering plunger for the entire  
> operating range of
> the mechanical plate.  For a given volume of air moving through the  
> air box,
> the plate will "float" to the same height.  Alter the relative  
> relationship to
> the fuel metering plunger via mechanical means and you've got a  
> change in fuel
> delivery for a given volume of air at every value of the air flow plate.
> 
> So, yes, it alters the AFR throughout the operating range of the air  
> flow metering
> plate and therefore engine operation.
> 
> ==Brett
> 
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