Miata Mailing List: October 1997, Message #192
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From: 	Paul Turin <pturin@ssl.berkeley.edu>

Subject: Re: 96+ owners/chargers

Date: 	Wed, 1 Oct 1997 16:36:39 +0000



Nope, the EGR is open in varying amounts any time the car is warm,

including acceleration and heavy load, and not deaccelerating or idling. I

don't think the lean condition is caused by the fuel system, as my car has

the stock injectors (same as 94-95's? good Q, have to check that), and the

standard BEGI fuel boost pump and VRGFPR. I've tried running the fuel

pressure as high as 120 psi at full boost (shouldn't need more than

100psi), with no effect. Currently have it set at the recommended 55psi at

atm and 100psi at 8psi boost.

 

The EGR system is the same as the '95's, at least, except that it has an

"EGR boost sensor" that measures atmospheric and EGR pressure. This

sensor's output is taken into account in calculating the injector pulse

width, according to the manual, but they don't say how it's used. Normally,

it would see between -5 and 2 psi or so, and under boost its seeing

somewhere between 8 and 20 psi. I suspect that this voltage being too high

is contributing to the problem. Experimentation continues!



Paul Turin



>

>So how does the EGR work on the Miata.  Doesn't it close at WOT?  If so,

>wouldn't this give it a constant pressure, eliminating any effect on the

>determination of the fuel maps at least at WOT?  Also are you sure that the

>full lean isn't an indication of the limitations of the fuel system,

>pump/injectors/regulator as opposed to the ECUs handling of fuel maps?  Has

>anyone attached a fuel pressure gauge to a boosted OBDII Miata?

>

>Frank Mowry

>

>