[Fiacco819]

I've never read up on any "tunable" MAF's. I'm being offered a 90MM SCT Ba-2400 with filter for for $125. I know its a bit large for a N/A car, but I have plans to supercharge in the future. So here's some questions:
-How do you feel about the Ba-2400?
-I'm running 47# injectors, so obviously I'll need a tune.
-I'm Just getting the MAF, so what will I need for a chip, or can the stock computer compensate for no chip?
-I'm really green when it comes to the tuning, so any thorough explanations would be helpful. (I've always been more of a changing jets kinda guy =] )

its on a 93 coupe, AFM 4" power tube joined with 75mm accufab race TB

[FastStang91Lx]

It's not too large, and no it won't compensate on it's own for the large injectors.

[Fiacco819]

So all I know about this setup is the SCT MAF isn't "calibrated" for injector size. I would need a custom tune to program the computer to know that its a 90mm MAF, and 47# injectors. Curious to understand how this works, and what other items i'll need. I'm very interested in expanding my knowledge

[FastStang91Lx]

Basically the computer reads the maf signal which varies in voltage. It uses that signal, plus a few others sensors to determine the amount of fuel to spit out the injectors. When you 'calibrate' a maf to a larger injector size, you are essentially using a percentage of the signal according to lb/hr to equal what a 19lb injector to air ratio would be, since the computer still thinks you are using 19's. This is a very basic way to explain it, but there is much more that actually goes into it.

[fogged306]

Stock computer can't compensate for that large of an injector accurately, even with a MAF that has a calibration for the 47's. You'll need a chip burned or an aftermarket tuner like a quarterhorse, tweecer, or PMS.

What faststang said is correct. The MAF outputs from 0-5 volts. Depending on the amount of air flowing through the housing, the voltage will vary accordingly. For example, if you have a stock meter and the car is idling at it's target RPM of 672, it would be flowing about 15kg/hr and the voltage would be .17 and at 5000 RPM it would be flowing 700kg/hr at 4.3 volts (completely made up numbers because I'm too lazy to look up a stock MAF curve but they illustrate the point). There is a table built in to the computer that takes those voltages and knows what kg/hr each one means, this is called the MAF curve. The computer uses this data to know how much fuel to spray for a given amount of air entering the engine. It knows the precise amount of fuel to spray because the specs of the injectors are programmed in to the computer as well. It knows exactly how much fuel will be sprayed for any given puslewidth the injector is fired.

So now when you change injectors without changing the tune, the computer has no clue that it's spraying more fuel per pulse width. To compensate people use calibrated MAF's. Those actually under-report the kg/hr per voltage to trick the computer into thinking there's less air entering the engine than there actually is, so it will shorten the pulsewidth and spray closer to the correct amount of fuel. The problem with this is that the computer uses the amount of air readings and the throttle position readings to calculate load. The more load, the more timing it pulls. If you have a MAF that's under-reporting the amount of air entering the engine, the computer is going to mis-calculate the load the engine is actually under and won't pull enough timing. This means you will have a greater chance of detonation under load. There's a lot more to it than that, but that is one of the main reasons that when you change injector size, you want an actual tune and not just a calibrated MAF. The farther you get from the stock 19's the worse the problem becomes. If you had 24's and a cal'd MAF, it would hardly be an issue, but with 47's and your engine, you absolutely need a tune to run right. That's a lot of injector for a stock stroke mildly modded N/A engine. It can easily be compensated for in the tune, but you can't just slap those on with a cal'd MAF and expect it to work fine.

[Fiacco819]

Fogged,I greatly appreciate every time you have came and answered my questions, your truly a wealth of knowledge that I'm trying to soak up like a sponge haha. I've tried reading around a lot to get a good base of what goes on in the tuning process and how the MAF and injector size is calculated in the computer. I ended up buying the SCT MAF, but without the chip. I understand this will most likely run VERY poorly or not at all with this MAF and my 47# injectors untuned.

I've looked into the quarterhorse that you seem fond of, but still havnt found an article like "How To" so i'm not sure I'm ready to commit into buying a tuning software. If you know any that I can keep reading up on, I'd enjoy reading up. But If I choose to have a tuner tune it for me, what chip is recommended, and any other things I can do to make it easier for the tuner, and cheaper for me?

[fogged306]

No problem, and believe me, I'm no wealth of knowledge. I have a very basic understanding of tuning. I haven't really scratched the surface of it to be honest, lol. It's pretty involved.

You're better off without that chip because there's only a small chance it would have worked for your specific application. If it was a custom burned chip for a car that didn't have your exact mods, it wouldn't have been ideal, and if it's a canned tune chip from a company it's not ideal for anyone's car. The first few threads here answer the basic questions about the QH and tuning in general with that style tuner. You can also go here and download the software you would use for the QH for free. Binary Editor and EECAnalyzer are the two programs you would use. They allow you to download them and play with them for no charge, but to write the tunes and actually use them on the vehicle you have to register them, which is what you have to pay for. There's help files built in to EECAnalyzer that are very useful. You just go to whatever tab you want to learn about and click the help button and there's usually pages and pages of info that explains just about everything you want to know about the subject.. or at least enough to give you a basic understanding so you can use that knowledge for tuning.

You can either go that route or just go to pops, or somewhere that knows fords, and have a chip burnt. You can also get a quarterhorse and then have pops write you a tune for it. That way you can get up and running with a custom tune from a professional and then take your time learning how to use the QH and as you mod the engine, you can mod the tune accordingly. That saves you from ever having to buy another tune or chip ever again.