new fuel injectors gone bad
Senior Member
Joined: Aug 2004
Posts: 144
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Your right, it is not adjustable as said but the transfer function should match the injectors. These engines work no different than the 5L Mass air engines.
Consider the Cobra in the mid 90s. They had 24 lb injectors and a matching air meter from the factory.
There should be a matchup with the air meter and the injectors size for proper all around running. If you don't want to consider it, then do some home work and find out what these systems do.
There are ways of tricking within limits but is is not wise to get into all the greif that can result from it.
I didn't just crawl out from under a rock, a few days ago, on all this.
Consider the Cobra in the mid 90s. They had 24 lb injectors and a matching air meter from the factory.
There should be a matchup with the air meter and the injectors size for proper all around running. If you don't want to consider it, then do some home work and find out what these systems do.
There are ways of tricking within limits but is is not wise to get into all the greif that can result from it.
I didn't just crawl out from under a rock, a few days ago, on all this.
That has got to be the most uninformed thing that I have heard in the last week. I am best friends with a custum tuner that now works for SCP.
That MAF has NO FUNCTION besides measuring Air flow. PERIOD. Based on that air flow, the EEC looks off a table and then detirmines based off the injector slope how much fuel to dump. If your MAF flows X it dumps Y fuel. If you change your injectors to flow 50% better, Y = Yx50%.
There is no such thing as a "matching air meter". Sure you can take certian meters from certain fords and swap them and not have to reprogram the EEC, but thats because they have the same transfer function. Has nothing to do with injector sizes, period. That is programmed into the EEC and if you think otherwise, you have slipped into a bad C&L momment. They make you beleive you can swap injectors and reprogram your car by swapping out tubes in the MAF. All that does it make the car or lean or rich by the same amount of more or less flow. It works most of the time, but drivability suffers, because your car still thinks you have the old injectors in but you dont. Think about this for a moment, a EEC is programmed for 19lbs and you put in 24lbs injectors. All you do is swap MAF sampling tubes (a piece of aluminum). How on earth does the EEC know that? It doesnt. All it know know if you want less or moss fuel at any particular time.
BLAH... POINT IS.. MAF's measures air. Thats it Nothing less.. Nothig more. The EEC stores Injector flow rates and spits out X amount of fuel based off what the MAF tells is how much air is coming in.
Chris
Senior Member
Joined: Jul 2004
Posts: 6,200
Likes: 39
From: Easton, Pa.
'''''Swap out sampleing tubes''''
You just admitted the air meter has to have a change to stay within parameters.
If this in not done, the airflow can top out the transfer function before max airflow is reached.
This is just the point I was making in the firs place.
What do you think you are doing by replacing the sample tube? IT'S MAKING THE AIR METER A CLOSER MATCH TO THE INJECTORS a side from the PCM calculations.
What to hell are you talking about?
You just admitted the air meter has to have a change to stay within parameters.
If this in not done, the airflow can top out the transfer function before max airflow is reached.
This is just the point I was making in the firs place.
What do you think you are doing by replacing the sample tube? IT'S MAKING THE AIR METER A CLOSER MATCH TO THE INJECTORS a side from the PCM calculations.
What to hell are you talking about?
Last edited by Bluegrass; Mar 18, 2005 at 11:18 AM.
Technical Article Contributor
Joined: Dec 1997
Posts: 9,417
Likes: 11
From: Windsor,Ontario,Canada
BigJohn,
If you have not reset the PCM, disconnected the battery, since the injectors were installed then do so. If you have then you have a few choices. Put the stock MAF sensor back on. If that doesn't correct the problem then the PCM is not capable to allow for the increased fuel that is available to the engine. There are two ways to correct this. Replace the injectors with 19# ones or cet a custom tune for the 21# ones. I would talk to Mike Troyer in the computers forums. he hails under the name of Superchips Distributer.
Something to ponder. The stock sensor is smaller than the aftermarket one that you installed. Adding a bigger MAF sensor allows more air into the engine. But that is only 1 peice of the puzzle. Your injectors must be able to add more fuel to the extra air. The MAF sends a voltage signal to the PCM and the PCM uses this voltage to determine the amount of air is flowing. It then adjusts engine parameters accordingly. The reference voltage sent to the MAF is 5v so in theory the max voltage back to the PCM will be 5v at max airt flow. The PCM has tables that tell it what to adjust at 5v. And for that matter what to adjust at 1 volt and so on. When the PCM turns on the injector it is held open for a specified amount of time based on the voltage seen from the MAF and what the programming tells it to do. What aftermarket MAFs do is allow more air to enter the engine for a given voltage. Remember the PCM thinks that at say 4.5v there is X amount of air flowing. This is not true because your new MAF is larger. So the PCM will see a lean A/F mix and add more fuel. More fuel + more air = more power. That is how the Aftermarket MAF sellers get to claim more power by using their MAF. Things get tricky when the PCM is not able to adjust the proper amount of fuel to inject because it is at its max limit. Say at idle there should be 10% more air flowing because of the bigger MAF. Or at WOT there should be more air flowing over stock but you cannot go over 5v so the PCM only sees 5v and bases its fuel requirement on the stock MAF. That is where the rich and lean function of the PCM can help to some extent by adding more fuel. If you go over the limit of adjustment then the MAF will not work properly. What you have done by using a larger MAF and larger injectors is exceeded the limits of control that is built into the PCM. So by going back the the stock MAF you might fall back into the parameters that the PCM can adjust for.
JMC
If you have not reset the PCM, disconnected the battery, since the injectors were installed then do so. If you have then you have a few choices. Put the stock MAF sensor back on. If that doesn't correct the problem then the PCM is not capable to allow for the increased fuel that is available to the engine. There are two ways to correct this. Replace the injectors with 19# ones or cet a custom tune for the 21# ones. I would talk to Mike Troyer in the computers forums. he hails under the name of Superchips Distributer.
Something to ponder. The stock sensor is smaller than the aftermarket one that you installed. Adding a bigger MAF sensor allows more air into the engine. But that is only 1 peice of the puzzle. Your injectors must be able to add more fuel to the extra air. The MAF sends a voltage signal to the PCM and the PCM uses this voltage to determine the amount of air is flowing. It then adjusts engine parameters accordingly. The reference voltage sent to the MAF is 5v so in theory the max voltage back to the PCM will be 5v at max airt flow. The PCM has tables that tell it what to adjust at 5v. And for that matter what to adjust at 1 volt and so on. When the PCM turns on the injector it is held open for a specified amount of time based on the voltage seen from the MAF and what the programming tells it to do. What aftermarket MAFs do is allow more air to enter the engine for a given voltage. Remember the PCM thinks that at say 4.5v there is X amount of air flowing. This is not true because your new MAF is larger. So the PCM will see a lean A/F mix and add more fuel. More fuel + more air = more power. That is how the Aftermarket MAF sellers get to claim more power by using their MAF. Things get tricky when the PCM is not able to adjust the proper amount of fuel to inject because it is at its max limit. Say at idle there should be 10% more air flowing because of the bigger MAF. Or at WOT there should be more air flowing over stock but you cannot go over 5v so the PCM only sees 5v and bases its fuel requirement on the stock MAF. That is where the rich and lean function of the PCM can help to some extent by adding more fuel. If you go over the limit of adjustment then the MAF will not work properly. What you have done by using a larger MAF and larger injectors is exceeded the limits of control that is built into the PCM. So by going back the the stock MAF you might fall back into the parameters that the PCM can adjust for.
JMC
Senior Member
Joined: Aug 2004
Posts: 144
Likes: 0
What do you think you are doing by replacing the sample tube? IT'S MAKING THE AIR METER A CLOSER MATCH TO THE INJECTORS a side from the PCM calculations.
Lets put is this way. If you stock MAF was capable of handling enough air flow to accomidate 500hp and your sitting at 300hp. Now your injectors wont handle anything past 350.
You add a blower and your hp numbers will be 400hp. The is 0 need to to add a larger MAF. But you need larger injectors. So you slap in bigger injectors, chip or reprogram your EEC and all is well.
So why are we touching the MAF again?!?!?!?!?!? Closer match to what?!?