Improved FD

car was tuned about 2 months ago (BDC)

after installing a new Denso (Supra) pump, I'm seeing low to mid 10s AFR, as opposed to the usual low 11s (and it's also significantly cooler compared to when the tune was performed, which is the opposite of what I would expect)

anyway, the car still runs good, just wondering if I can shave off a little fuel off the top using the Commander?

I also dialed down the regulator pressure to 36 psi at idle from 39...seemed to help a little, it was hitting 9s

cewrx7r1

iTrader: (2)

YES you can.
Normal Mazda idle fuel psi is 28-32 psi.
Normal Mazda 0 psi boost/vacuum fuel psi is 36-38 psi, some owners run higher
You set your base pressure at 0 psi.


Adjust your FP pressure to what it was before the install as it is too high.

Improved FD

thanks chuck...although I was told by several "knowledgeable" people that fuel pressure at idle should be 36-38 psi (?)

anyway, will resetting the fuel pressure at low speed affect AFRs at full throttle?

cewrx7r1

iTrader: (2)

Base fuel pressure should be set at 0 PSI( control hose to FPR to atmosphere) with the engine idling, and the fuel pump at maximum voltage (FP ---> GRD in diagnostic box if still using the speed relay).

Any change in BFP will affect the whole vacuum/boost range AFR levels.
When ever changing FPs or FPRs, you should always measure your BFP before and after if you want to prevent having to AFR tune/correct.

If you went from 38 BFP to 42 BFP and your AFRs went up 5%, you could always just reduce your fuel levels by 5% using any of the fuel adjustments.

Improved FD

thanks again, chuck, leaned everything out across the board when I reset the bfp, even the idle is leaner (and smoother)

if I'm seeing 15s and even low 16s at cruise at tip in, is this a problem?

cewrx7r1

iTrader: (2)

If you lean out your idle to best lean idle, and also set cruise from 35 to 100mph at about 16AFR, you will get better mileage and have a clean exhaust.

That is what I do.

Improved FD

we couldn't figure out how to lean out the idle...do you have a link on how to do that, without retuning the whole range? (I'm running 850/1200s)

a link to minor fuel adjustments with the Commander would also be helpful, this section could use a FAQs sticky, but I know you guys have a life :p

cewrx7r1

iTrader: (2)

You definitely need my tuning notes, PM me.

A search on 850 might reveal about using lag to tune idle and why this is needed.