I've been searching but.. MAF, TB, ad injectors questions...

sizemoremk

sizemoremk

Registered User
I am trying to figure out what exactly the bigger MAF and TB and injectors do for you.

At what point is a MAF upgrade and injectors needed? These seems to be done as a set... Will bigger MAF and injectors be any good without the EEC asking for more fuel? ALso what do the lbs in injectors mean exactly?

And when is a throttle body upgrade needed?

Is there any use to either without EEC tuning, or engine work?

Which one is done first?

I've been looking, but can't seem to pull them all together.
 
sizemoremk said:
I am trying to figure out what exactly the bigger MAF and TB and injectors do for you.

At what point is a MAF upgrade and injectors needed?
Click to expand...
At about 250-260rwhp
These seems to be done as a set... Will bigger MAF and injectors be any good without the EEC asking for more fuel?
Click to expand...
A reduction of restriction through a larger MAF may result in as much as 10rwhp gain, or not. Depending on "other" things which are not so easy to define.
ALso what do the lbs in injectors mean exactly?
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That is the amount of fuel in lbs that each injector will flow at 100% duty cycle (wide open) at the rated fuel pressure.

And when is a throttle body upgrade needed?
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Hard to say, any SC may gain 0-5rwhp from a 70MM TB.

Is there any use to either without EEC tuning, or engine work?
Click to expand...
Yes but tuning helps.

Which one is done first?
Click to expand...
None should be done until your engine airflow requires it. A stock motor will not benefit substantially from any of it. You need to do exhaust first.
 
What does the MAF trigger exactly?

I know there is a curve and it sends information to the EEC, but I don't quite understand what it does. I knwo the TB allows air to come in, and that a bigger one will allow more air, but don't understand what the MAF does, besides restrict flow???

Still kinda fuzzy on the injector measurement...

So a 30lb injector will flow 30lbs at what pressure? Does't the fuel pressure change via command from the eec smehow???

Thanks!

BTW Exhaust is comming!
Resonator is ont he way :cool:

I'm going 2.5 to the resonator, 3" to the back to hook into the split in the stock exhaust into the muffler.

Also just ordered the Ford Focus intake I seen here.

And then maybe a 10% pulley.

Then I am gonna hook into the O2 sensors, and maybe replace them to check things out with an AF meter.

Then maybe a 50-75 shot of NOS for the strip.

I started taking my 3year old to the dragstrip a few weeks ago, and now I've got the fever :)

My boy loves the "Mytangs" and "tbards" Good kid :D
 
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The size of the injectors is determined by the amount of air you can pump through your engine. The injectors must be able to flow enough fuel at a given fuel pressure at a given duty cycle to maintain a given air/fuel ratio.

Enough givens for you?

The MAF senses the amount of air entering the engine and outputs a signal to the EEC. The need to change the MAF comes from the existing MAF being unable to accurately report a signal the EEC can understand at higher air flow rates. I.E. it is like when the A/C can't keep up with the temp in the house. Setting the thermostat to 68 doesn't make it 68 if it's so hot outside it can't cool anymore. Well the max Air a maf can read is 900 CFM, running 1000 CFM through it is still only going to look like 900CFM to the MAF and thus to the EEC.

Thus a new MAF is necessary to read the extra air. Of course since the MAF sits in the flow of air, often times a new MAF is necessary to allow more air to even flow through the engine. I.E. a bigger opening.

Fuel pressure is a fixed value that the EEC expects to be within a + or - range. So it doesn't control fuel pressure. Forced induction engines (like ours) compensate for the additional fuel needed when under boost by referencing fuel pressure against manifold vaccum. When under positive pressure, fuel pressure is increased beyond the fixed value.

The EEC controls the fuel/air mixture by measuring the incomming air, determining engine load, and then adjusting injector pulse widths to distribute the proper amount of fuel into the engine to achieve the proper fuel/air mixture.

Injector pulse width is the measurement of the length of time an injector is open to allow fuel to flow through it. With the known fuel pressure, the known air mass, the known injector SIZE and known engine load the EEC can compute the necessary pulse width for each injector to achieve the required fuel/air mixture.
 
Adding to what Mike said is that the Mass air is a restriction at its current size..You will gain power by changing it out because the new one will be larger thus being less a restriction. That being said 42lb injectors and a properly calibrated mass air will last you for quite awhile power wise and is a good size to go to with the mods you have in mind
 
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