Soap thanks for backing me up. Have been running the stock program for a little while because my street program was pinging. Found that my program was giving me 16.5deg timing and .850 volts on the o2. With the stock program I see 13.5deg timing and .920 volts on the o2. I am not telling you to go out and try this as your results may vary.

I have the IT24 plugs in (much colder) the 255 pumps (higher fuel pressure) which will give a richer condition. Also my stock program only has 13.6deg timing and most see 16deg.
Not saying I am an expert, but I have been around for a while and know a thing or 2. I did build my motor myself.

 

well im thinking of running a 3lber w/ no chip, but not for long, i'm gonna get one probably a month after the install.

 

Couldnt get away with that here in CA with our fuel. 18 psi is a lot for the stock computer. Whats your Af #'s?

The 255 pumps dont increase pressure, just volume. If you want increased pressure, buy an adjustable fp regulator.

 

The computer works by measuring the airfow with the MAF. Then it takes that number, looks up a table based desired A/F number, and calculates how much fuel to inject. If you raise the boost, you are obviously putting in more air, but the computer directly sees this because the MAF will be higher. The stock program is very rich, so the A/F numbers should be safe.

Typically with increased boost the timing needs to be retarded. But the factoty calibration is already very safe on the timing. Why don't one of the tuners step in here and tell us what the stock timing is, and what range they burn the chip for at +2 +4 or +6. That would settle the argument right away. As long as their chips have the same or more timing than stock, then stock is still safe.

The other benefits of a chip sure are nice though. Especially the shifting.

 

well only idea i can think of is, nobody wants to lose money.

also i found this on nloc

 

Stock AF on my L on the Dyno was 10.8.

You think the computer can compensate for 10 psi of addtional boost and youre safe? Youre nuts.

Strap that non chipped, 18 PSI the dyno and lets get a AF readout. That will settle it.

 

Your ok as long as you don't max out your voltage on the mass air meter, like you said the computer chooses wich fuel and timing based on the voltage. I thought also the manifold air temp along with mass air voltage played a part in what fuel and timing the computer chooses even in open loop.

 

I don't think that anybody who hasn't seen the code that runs on the ECU can know for sure everything that comes into play. In my limited experience with ECU's the open loop fuel calculations come from a measured mass flow from the MAF in g/sec. Then a lookup is done in the open-loop table to determine the desired A/F ratio. So you no mass of A, desired A/F, and the can calculate fuel mass. The last step is to calculate a pulse width from the injector calibration. Who knows exactly how many trims there are to that number, but that's the basic equation.

When in closed loop mode, the same thing happens but the O2 sensor feedback is used to control the actual delivered fuel mass. So even if the MAF calibration goes out, the delivered A/F is still the same (to some maximum allowed trim).

The air temp is used to correct the timing. Since knock is related to temperature and pressure, the starting temperature is important to see what the timing should be. The pressure is also, but the ford ECU doesn't measure pressure, but infers it from the MAF reading at a known engine speed.

So as a I said before, if you put more air in, the computer can directly measure and still deliver the apporapriate amount of fuel (assuming you fuel system is sized big enough and you MAF sensor has enough headroom). The timing is the only thing that could be wrong. But then most of the chips advance the timing rather than retarding it. The limit on how far you can go before needing a chip is when you need less timing than the factory program is giving you. My gut feeling is if you're not getting detonation, then your alright. In my truck, its easy to hear. Just keep your ears peeled for that sound.

 

I think we are talking apples and oranges. The problem with higher boost levels in California is the gas. We only have 91 octane fuel here. We use a chip in Ca to remove timing at higher boost levels. 100 octane unleaded in Ca. costs about $5 to $6 a gallon and is only available in a few places. I am sure you can get away with a lot more in states that have better gas than we can here. Now, if you have a tank of 100 octane go for it , more boost, more timing and more power at those levels. It is just too much of a pain and way too many $ to use 100 anywhere than the track. Skip

 

I will agree that the PCM should be able to adapt to additional boost ( I'll leave it for you to decided exactly how much...) while under closed loop. However, if the PCM in the truck is anything like what they used in Fox-3 mustangs, then once you goes WOT, the computer goes into open loop and switch to a fixed fuel map. Some people have suggested feedback from the oxygen sensors are still used as input while in open loop, but I've seen several dyno sessions on my '93 GT that suggests otherwise. IMO, if you are running more than 2# of boost, it is probably a good idea to use a chip to keep it on the safe side during WOT and probably drop the shift RPM a bit to avoid over-spinning the blower.