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Discussion Starter #1
hey all,

planning for a blower and i was just wondering. the vortech kit comes with 30lb injectors, but i would prefer to run a larger size, preferably 42lb. anyway, i was just wondering: will i have to change or modify the mass-air in order to get it to work with the larger injectors?

my plan was to install the blower at my buddy's house, then drive it to the shop and have it dynotuned. in any case, i would like to know what i should do...

gino
 

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killerpony said:
hey all,

planning for a blower and i was just wondering. the vortech kit comes with 30lb injectors, but i would prefer to run a larger size, preferably 42lb. anyway, i was just wondering: will i have to change or modify the mass-air in order to get it to work with the larger injectors?

my plan was to install the blower at my buddy's house, then drive it to the shop and have it dynotuned. in any case, i would like to know what i should do...

gino
The MAF will have to be calibrated to the injectors. If you're just going to drive it immediately to the shop and have it tuned, after the install, just leave the stock 19s in there, and STAY OUT OF BOOST! But, yes, you'll need a properly calibrated MAF, no matter what size injectors you use - unless you have the tuner adjust for the discrepency with the chip.

Take it easy!
josh
 

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Re: Re: technical question about mass-air and fuel injector size...

32Vpwr said:


The MAF will have to be calibrated to the injectors.
how does one go about doing this, shouldnt you just program the computer and tell it what the hell your running and be done with it.
 

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Like I said, a tuner could adjust for the calibration discrepency. Otherwise, you have to send the MAF back to pro-m to have it re-calibrated, or if you have a c&l, order the sample tube that corresponds with your injector size. If you want to keep the stock mass-air, I believe pro-m will recalibrate it.

Take it easy!
 

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Discussion Starter #7
ttt

how come the supercharger kits come with new injectors, but no new mass-air? how is it that they can package a kit in which they leave a difference between the two?

also, what changes would have to be made to the tune if you got a mass-air that was matched to the injectors? if you got a novi-1000 kit (that comes with 30lb injectors) and bought a seperate mass-air meter that was calibrated to 30lb injectors, how would the car run?

gino
 

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The Mass air flow meter (MAF meter) just measures amount of air, and really isn't calibrated to certain injector. It is calibrated to measure up to a certain amount of air.

The computer looks at the amount of air from the mass air meter and figures out how much fuel to inject based on the injector size. It normally wants to output about 1 unit of fuel for every 14.7 units of air.

If you change injector size you need to tell the computer about that, and it will then adjust how much fuel is injected to maintain the 14.7:1 a/f ratio.

However, for most people in the world, there is no way to change the injector size, most people don't have chip burning capabilities and Ford didn't give us a dial on the dash for specifying injector size.

So the next best thing is to fool the computer by telling it you are sending less air than you actually are, and the computer will then send less fuel, which is good, since your injectors are bigger.

And that is why you can buy a "30 lb MAF meter"... meaning if your car came with 15 lb injectors and you put this meter on it would tell the computer you had half as much air, so the computer sends half as much fuel, which will work great with 30 lb injectors which flow 2x as much as the stock 15 lb'er. If you put that "30 lb" meter on a car that came stock with 20 lb injectors, that meter is actually a "40 lb" meter since it is halfing the airflow.

Really the meters should be called "100% larger that a 96 Cobra calibration, not 'calibrated for 48 lb injectors'"

If you fool the computer in this manner, it is bad because the computer sees half as much airflow and thinks you're barely loading the car, so it adds in all sorts of timing advance to help low-load driveability. But since you're actually going wide-open-throttle down the street, guess what? You're getting too much spark advance and could get detonation.

So if you change the size with a meter calibration, you need a dyno tune to setup all the tables in the computer to account for this. Hmmm... back to the chip again anyway!!!

The only time you want to get a meter with a different calibration is when you're flowing more air than the stock meter can flow. This is the notorious "pegging the MAF meter problem". If you're just changing injectors, change it in the chip, if at all possible.
 

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Discussion Starter #9
that was an awesome response! it's exactly what i was getting at. so in your opinion, the stock Mass air with a chip tune will be able to keep up with the 30lb injectors that come with the kit...right?
 

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Excellent post, John.
The straight answer I was looking for.
Thanks.
 

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If you just run the base vortech kit the stock mass air is OK. If you up the boost level, then the MAF is gonna peg. There are many, many posts about this already.

If you run the base kit, you don't need 42's. If you up the performance to a point where you need 42's, you'll need a MAF with more range too.

I think JMS now sells matched MAF/injector/chip sets.

David
 

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I installed the base 8lb Vortech kit on my 96 GT and it pegged the MAF at 5000 RPM. I had to upgrade the MAF because you can't fix a pegged MAF with a tune. I went with the Lightning MAF and decided to go ahead and get 42lb injectors to get a matched set. The car doesn't actually need the 42lb injectors and is only using about 65% of the capacity of the injectors. The car is making 368RWHP and 363 RWTQ and is running rich on the top end.
 

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This is sort of off the subject but sort of not...

If you grind the post out of the stock MAF meter, it will flow more air through it, but the electronics will still record the same amount. Or, saying it another way, for the same amount of air flowing through, the MAF will now report less voltage.

According to APE, a stock 80mm Cobra (24 lb) MAF meter with the post cut out, and the appropriate transfer function in the computer, won't peg with any horsepower level that the stock s-trim kit will put out.

Note I am not advocating grinding the post out... but if you wanted to go cheap and extend the range of the stock MAF meter and if you can reprogram your maf xfer function, this is one way to go.
 

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dont f with the post in the maf, if you do your right back in the boat of fooling the eec, THATS BAD. jslagel said it right DONT FOOL THE EEC OTHERWISE YOUR JUST ASKING FOR PROBLEMS. If you just spent 4k on a supercharger, why wouldnt you spend another 300 for a good chip that can tell the computer what your doing with the maf/injectors???

just a few quotes from a guy that has forgotten more info about the ford eec than most of us will ever know.

A MAF measures Mass Air Flow. That is the mass of the air flowing into the engine.
There are two small wires inside the MAF that get an electric current ran across them. As the current flows the wires heat up and as the wires heat up, the resistance changes. The MAF has circuitry inside it to measure this change in resistance across the two hot wires.

The more air that flows across the hot wires the cooler the wires get and the more the resistance changes, hence more air flow. If it is a high density day, then there is more air density and thus more cooling so more air density is automatically compensated for. The same is true for altitude. The lower air density does not cool the wires off as much so it measures less air flow.

Now, here is why you should NEVER have a K&N filter on your car. The oil from the filter migrates into the MAF and onto the hot wire. The wire is now insulated and will measure less air flow than what's really flowing into the engine, thus shifting the engine lean, this is bad.

While I'm K&N bashing, I have another point. Let's give you a rag to cover your mouth. Then I want you to run around with the rag over your mouth and breath through it. Now, let's do the same thing but this time I'm going to put oil on the rag. Which way do you think you will breath better? We have a few knowledgable medical people here, answer that question.

I have NEVER seen a K&N filter gain power over a paper filter if the dimensions of the filter are the same.

To make the insulation worse, once oil gets on the hot wire, it will now collect more dirt, thus insulating the wire even more.

Have you cleaned your MAF lately?



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