kris

Is it uncommon to see 97% with 12lb, downpipe ,gutted cat, rb cat back? I am runnin base mod. This seems kinda high.

matt_ledbetter

Yes, that is very high... Is that with the base maps?

With no intercooler, your intake temps are probably so high that it is dumping in as much fuel as possible.

Do you have the commander? What temps do you see after a few minutes of spirited driving?

-Matt

ech

My readings were similar, and I run a set of maps that are slightly richer than base mod. Now they are much lower (in the %80s)

A lot changed - new motor, y-pipe, Radiator, and cleaned injectors. of these I suspect the last change.

I know that in closed loop - the ecu will compensate for clogged injectors with more fuel - but I have no idea if it applies the correction to open loop (WOT, etc) as well. Just a thought.

kris

My intake temps on that run were 32c. Does a weak fuel pump cause higher Injd? The filter is new, i am gonna order the 225 hp walbro anyways.

matt_ledbetter

That's not bad... Especially for a stock intercooler...

The weak fuel pump would not cause high inj duty cycle. At that point, you are in open loop. Any problems with fuel delivery will not be compensated for and you will most likely lose your motor.

I only see about 85% (at 14lbs) with the mods listed below and I'm also using the base maps. Are you *sure* you are using the base maps and not modified SR maps?

-Matt

kris

My pfc was bought at rx-7 store. It is unaltered. Is there anything i need to check in my maps? Will different maps change the duty cycle? I thought only larger injectors will change the cycle...

matt_ledbetter

The Inj duty cycle is a representation of the "open" time of the injectors. The injector is basically pulsed to allow the flow of fuel.

If you manually change the maps on the pfc you will see the injector duty cycle change accordingly. If you jacked all the numbers up as high as possible, you would see 100% duty cycle, etc...

If you put in larger injectors, you are changing the duty cycle as well as the injector pulse will be shorter to allow the same amount of fuel to be injected.

There are maps available at the top of the Power FC forum. Just compare your maps with the base maps.

-Matt

kris

I definatley have the base mod maps. So what else could cause such high inj%? So what area should i start looking in now? The high duty kinda worries me. Thanks

matt_ledbetter

During open loop, the Power FC has no idea how much fuel it is really injecting. The Injector duty cycle is simply using the inj size entered via the commander and the maps to figure out the total percentage of inj pulse.

Anything wrong with your car will not come in to play. The inj duty cycle is not directyly related to power created. Adding a pump, larger lines, etc will not change it either. Larger inj's will, but only because you then change the injector size via the commander.

What are you basing the 12lbs of boost on? An aftermarket gauge? What is the commander showing for boost?

-Matt

kris

My commander showed high .82 for boost.

matt_ledbetter

*most* Power FC's read low. Mine reads .82 when my Blitz gauge and EBC read close to .95. Odds are you are running 13-14lbs of boost.

There aren't many things it can be. Either fuel maps or something is causing the pfc to dump a ton of fuel. Most likely intake air temps.

-Matt

matt_ledbetter

Just to clarify... Yes, colder intake temps require more fuel. But, as intake temps get too high, most ecu's will dump fuel to prevent detonation.

-Matt

adax

iTrader: (2)

Looks like the PFC actually injects less fuel as intake temps rise up to about 70 C. Then if under boost, more fuel is injected. It does retard timing in response to elevated intake temps to prevent detonation though. Also remember the response time of the stock intake temp sensor is about 5 minutes which is a pretty big weak link in the system, negating a lot of the programming.

Alan

KZ1

inatek temperatures have such adn insignificant effect on combustion temperatures, why woudl they contribute to detonation. I kno wthe PFC retards timing before wtaer temp is 65C and after 95C or maybe it is 99C. anyway, eveyne always says how hot intake leads to detonation, I just can't figure that out. the determining factor for combustion temps is the a/f ratio. Yes cold air will give you more power, but combustion temps will remain the same.

50tooslow

Hotter air is less dense. It contains less oxygen molecules which are needed for combustion. This causes a lean condition which raises the combustion temps leading to pre-ignition of the fuel (detonation).

KZ1

wouldn't it create a rich condition as there is now less oxygen and same fuel? we are obviously assueming that air intaek sensor is very slow and doesn't have time to react.