I have been studying the following diagram for the stock FD ECU from the FAQ list and reading numerous posts.

http://www.autosportracetech.com/RX-7/ecu.htm

Here are a few of conclusions:
1) Below 27% throttle, the ECU doesn't look at intake are pressure.
2) Above 27% throttle, the ECU uses are intake pressure.
3) Above 12 PSI boost, the stock ECU cuts fuel
4) Knock is only likely in high-RPM, high-load and lean conditions.

I would really like to know more about what the ECU is doing in each of these zones. The descriptions on the page I reference above are helpful, but really to course (decrease, increase, feedback). I changed the diagram from above to try to demonstrate what the ECU is doing.



Green = increase fuel
Yellow = feedback
Red = decrease fuel

So what do you guys think, am I understanding this correctly?

 

Don't know if this will help you. Discussion about the stock ECU & mods.

https://www.rx7club.com/3rd-gen-archives-73/stock-ecu-10-psi-myth-308996/

 

The red area is actually total fuel cut - when you're there, no fuel is being injected. This is pretty standard with most fuel injection systems - not only does the car run better, but it doesn't afterburn (pops in the exhaust), uses less fuel, and is better for the catalytic converter.

If you'd like a better understanding of the ECU (and a lot of the other systems in the car) get the 1993 RX-7 Service Highlights book. It's around $35 or so from Malloy Mazda, and it explains a LOT of the theory and "why" behind the car's systems. Excellent resource to have - also bigtime explains the turbo systems, etc.

Dale

 

Ack, so anything over 12psi under WOT and the stock ECU really does hit fuel-cut..

I always thought in the end it was really more CFM-based...

I guess with mods like dp, catback, intake...

It's understandable that @ 12psi, it would hit fuel-cut.

So gay!

I hate stock ECU. I am hoping for a PFC w/ Commander by the end of December.

I've gotta do some research as to how much boost I can safely run on stock radiator and IC, if I do end up upgrading to an alluminum AST and at least a better fuel-pump.. Gotta do some of those fan-mods too. Gah. So much to do! lol :P

 

It's not gay, fuel cut is there to save your engine. When you get a PFC, you'll set fuel cut just above your tuning point to save your engine in the case of an over-boost. The stock ECU is doing the same thing.

The stock ECU also handles knock retarding (which the PFC doesn't). The stock ECU is great for what it is. However, if you want higher than stock performance, you need aftermarket parts all around.

 

Are you saying that the fuel cut in the two red areas at the bottom also protect the engine? Since this range is near closed throttle and the ECU doesn't appear to consider manifold pressure, it seems that it is only trying to improve fuel efficiency (as Dale mentioned).

 

Fuel cut and low fuel usage are two different topics. IMO, that graph can be confusing. i.e. lowering fuel and cutting fuel yield different result. Being on full throttle and having fuel cut is a different feeling than coasting down a hill with no fuel being supply to the system. Both have no fuel being applied but two different results.