we Just installed a t3/t4 kit on a friends impreza...and he has an AFC....I was wondering if the afc hack would work on that car?
it uses a MAF sensor, instead of MAP

 

I though Mass Air units could see (albeit a certain amount) of boost and still compensate, especially with the aid of an AFC..?

 

Possibly.

I am sure the MAF puts out a voltage between 0-5V but the range of measurement is different. The MAF measures how much air is going in the engine directly, the MAF just measures pressure and does a bunch of math to get the amount air flow.

You could probably get it to work, but I am not sure if the result will allow a smooth transition. If you do it post here, I am sure Honda will be going to MAF eventually.

Randy

 

A MAF system is not subject to the rule of not seeing boost like our speed density systems. That's why it is a much bette system to convert to FI because it just see's how much air is flowing past based on how cool the "hot wire" gets and adds the appropriate amount of fuel. Then the only liniting factor is the injector pulsewidth.

Using larger injectors and having the AFC cut them down would work but the part of the hack that's really useful to us is cutting the MAP signal enough to not trip a CEL and that is not needed on a Mass Airflow system.



[Modified by 5 Liter Eater, 1:26 PM 3/29/2002]

 

That's exactly what I was thinking.. so why would you need an AFC hack for the MAF system?? The purpose of the AFC hack is primarily to prevent the ECU from seeing boost while still maintaining the ability to deliver the right amount of fuel, which you wouldn't have a problem with if you're usuing a MAF setup right?

 

so the MAF is able to see boost w/ out throwing a cell?? I did not know that.

 

It doesn't see boost at all, it just meters air flow not pressure. I'm assuming that a cars ECU can be programmed to cut fuel or ignition when the flow rate reaches too high (For example if the airflow reading on a DSM gets too high, the ECU cuts fuel), but it can't see boost no matter how you hook it up.

 

Mass Air Flow

Manifold Absolute Pressure

 

I was thinking air flow = pressure...in what respect do they differ?
Is it sort of like how the T25 at 7psi does not equal the T3/T4 @7psi?

how does an MAF function as far as controlling fuel curves?

 

Pressure is simply that, pressure. You can have pressure without airflow, for example when you drive into the mountains and have to pop your ears. That's caused by a reduction of air pressure.

Flow is the actual volume of air being taken into the engine.

You can have low pressure and lots of flow as well as high pressure and hardly any flow.

If you look at FI cars with a MAF sensor, you'll see that most of them have the sensor near the air filter. Even if the sensor was capable of reading pessure, it wouldn't be able to see boost from that location. Instead it would see a LOT of vacume because from that point air is only going in, not building up and creating pressure.

 

This is a rough guess from what ive heard about them, but does a Mass air flow sensor read how much extra air is being added and compensate by adding fuel automatically? . I know some ford products use these instead of a Map sensor.

 

thanks newt2



So how does an FI car using an MAF sensor work? What does the ECU base its fuel/ignition tables on?