Fuel pressure regulator

[IPRESS]

I hate to ask questions as it shows how little I know, but here goes.
What benefit and how does a fuel pressure regulator work for a 1st gen miata (95)? I saw that Bob had one on his ITA Miata at ARRC. (Just so I don't look totally dumb) I guess it would help lean out the A/F mixture? How do they work ie manually, do they overide the ECU?

[Eagle7]

The ECU does not control fuel pressure. In a racing context (WOT), the ECU does not use any feedback to control mixture. It controls the opening duration of the fuel injectors based on RPM, air flow/pressure, air & water temp, etc. With a certain opening duration, the amount of fuel squirted is proportional to fuel pressure (or pressure squared or cubed - I forget). By adjusting the fuel pressure you can move the air/fuel ratio up or down across the entire RPM/load spectrum. If there are rich or lean spikes, adjusting fuel pressure will not remove them.

[leawil]

Flow is a function of delta of squared pressures across the injector.

Raises a question I've been pondering. Is there any way to evaluate need for/benefit from increased fuel pressure other than making back-to-back dyno runs at various fuel pressure setting?

Also begs question of EGT. If fuel/air mix gets too lean, possible to burn an exhaust valve. Anybody got thoughts/guidelines on that?

[C. Ludwig]

Raises a question I've been pondering. Is there any way to evaluate need for/benefit from increased fuel pressure other than making back-to-back dyno runs at various fuel pressure setting?[/b]

A proper way? No.

Also begs question of EGT. If fuel/air mix gets too lean, possible to burn an exhaust valve. Anybody got thoughts/guidelines on that?
[/b]

EGT is determined by more than mixture. A seriously rich mixture combined with seriously retarded timing can produce very high EGTs. Tune for fuel mixture with your wideband and a dyno. Optimum mixture for peak power should fall within a relatively safe range of EGT. Next tune ignition timing based on dyno results. Most IT engines will be able to run MBT (minimum best timing) without a knock issue. If there is knock you need to either bring more octane to the table, fix a possible problem, or decide how much power you are willing to sacrifice.

[x-ring]

Flow is a function of delta of squared pressures across the injector.

Raises a question I've been pondering. Is there any way to evaluate need for/benefit from increased fuel pressure other than making back-to-back dyno runs at various fuel pressure setting?

Also begs question of EGT. If fuel/air mix gets too lean, possible to burn an exhaust valve. Anybody got thoughts/guidelines on that?
[/b]

Gee, look who showed up here. Welcome to the party!

Chris is right, you could adjust, run a few laps while watching the instruments, adjust, etc., but the dyno is the way to go.

[leawil]

Yes, Ty, I guess this means I'm officially out of the Spec Miata community and in the IT community.

[x-ring]

Now you can hang with the cool guys.