Just like the title says, how good is the PCM at adjusting to modifications. I hear it hates cams, but if I were to do heads, intake, exhaust and bolt ons, would the computer adjust itself to run this combo, or is a tune absolutely necessary? I would like to hold off the tune until I can afford it and a cam swap and do those two together, but for now I just want heads and intake.
To what point can the PCM "retune" itself?
- Thread starter dstang01
- Start date
Stanger007
Founding Member
I wouldn't see a problem with heads, exhaust, intake, pullies, etc.
Where most guys get in trouble is larger throttlebodies/cams but moreso, improper installation/adjustment of the installed mods or parts that were bad before. If you've got a vacuum leak, you are going to have a crappy idle. The same can be said for an exhaust leak around the O2s.
A full tuneup, code running and replacement of questionable sensors will get you on the right foot before doing any mods.
Wes
Where most guys get in trouble is larger throttlebodies/cams but moreso, improper installation/adjustment of the installed mods or parts that were bad before. If you've got a vacuum leak, you are going to have a crappy idle. The same can be said for an exhaust leak around the O2s.
A full tuneup, code running and replacement of questionable sensors will get you on the right foot before doing any mods.
Wes
Here are some more thoughts about modding a 94-95 Stang
and
Doing it with an un-optimized pcm
The pcm's ability to ... adjust ... learn ... re-learn ................
or whatever word you choose to use here
It has a focus on Closed Loop Driving
or
Driving conditions that are light load conditions and NOT wot conditions
however ... WOT conditions can be effected but lets not go there now
We are of course talking about the pcm's ... Adaptive Strategy
It is pulsewidth that gets the adjustment from the pcm and while there
is a range of adjustment ... it is limited.
I have come to believe this ..........
peeps think the pcm is more capable in this area than it really is
Honestly ... the thing to be concerned about is the need for more fuel
When you go down the path of looking for more power and start adding
more mods on a 94-95 stock Stang ... lack of fuel will be the first big issue
you will encounter.
You know you need more fuel to feed the additional air flow
so
You need larger inj's
Not only do you need larger inj's ... you need a meter with matching cal
Now is the time to say ... A 94-95 Stang's pcm is load based
The pcm uses the amount of load at any given time to A C C U R A T E L Y
command the C O R R E C T amount of spark and fuel
Here is where you can get into trouble with the load based pcm
The aftermrket meter matched to your new inj size ... It hoses up the load
Simply Put ... You no longer have accurate data being delivered to your pcm
This can snow ball into many different drivability issues.
The thing to remember here is ... the larger the inj size ...
The more likely you are gonna have more and more issues
Now ... you can find some relief with upping the fuel pressure
but
That little trick ... it can only go so far
You will have to deal with all this before you do a cam
and
If you look at a 94-95 Cobra ... it is a REAL example of proof
About cams
Yes ... a rule of thumb is ...........
The lower the lsa value ... The more the possibility of drivability issues
You see what is going on here ???
A focus on running tuneless .....
Well ... You take a ... double hit ... on the negative side of things
1) Larger inj's & meter hosing up all the pcm's load factors
2) Sure ... A cam with wimpy specs can be pcm friendly
but
Power is most likely left on the table with that approach
Your idea of doing everything but the cam will push your airflow
up to the point the 19's will not keep up at oem fuel pressure.
I'd tell you to up the pressure as you add more and more mods.
You then need to decide upon how much power you're gonna go for.
Based upon that goal, I'd then make a decision on inj size, meter
choice, cam specs, and tune the pcm accordingly.
Grady
and
Doing it with an un-optimized pcm
The pcm's ability to ... adjust ... learn ... re-learn ................
or whatever word you choose to use here
It has a focus on Closed Loop Driving
or
Driving conditions that are light load conditions and NOT wot conditions
however ... WOT conditions can be effected but lets not go there now
We are of course talking about the pcm's ... Adaptive Strategy
It is pulsewidth that gets the adjustment from the pcm and while there
is a range of adjustment ... it is limited.
I have come to believe this ..........
peeps think the pcm is more capable in this area than it really is
Honestly ... the thing to be concerned about is the need for more fuel
When you go down the path of looking for more power and start adding
more mods on a 94-95 stock Stang ... lack of fuel will be the first big issue
you will encounter.
You know you need more fuel to feed the additional air flow
so
You need larger inj's
Not only do you need larger inj's ... you need a meter with matching cal
Now is the time to say ... A 94-95 Stang's pcm is load based
The pcm uses the amount of load at any given time to A C C U R A T E L Y
command the C O R R E C T amount of spark and fuel
Here is where you can get into trouble with the load based pcm
The aftermrket meter matched to your new inj size ... It hoses up the load
Simply Put ... You no longer have accurate data being delivered to your pcm
This can snow ball into many different drivability issues.
The thing to remember here is ... the larger the inj size ...
The more likely you are gonna have more and more issues
Now ... you can find some relief with upping the fuel pressure
but
That little trick ... it can only go so far
You will have to deal with all this before you do a cam
and
If you look at a 94-95 Cobra ... it is a REAL example of proof
About cams
Yes ... a rule of thumb is ...........
The lower the lsa value ... The more the possibility of drivability issues
You see what is going on here ???
A focus on running tuneless .....
Well ... You take a ... double hit ... on the negative side of things
1) Larger inj's & meter hosing up all the pcm's load factors
2) Sure ... A cam with wimpy specs can be pcm friendly
but
Power is most likely left on the table with that approach
Your idea of doing everything but the cam will push your airflow
up to the point the 19's will not keep up at oem fuel pressure.
I'd tell you to up the pressure as you add more and more mods.
You then need to decide upon how much power you're gonna go for.
Based upon that goal, I'd then make a decision on inj size, meter
choice, cam specs, and tune the pcm accordingly.
Grady
earleys94gt
Active Member
I went the route of putting in a "small" cam, the Steeda 19.
This cam only has .480 lift, and works well with the stock ECU.
I put this cam in because the heads were being replaced on the motor, and I figured 'why not while I'm in there.'
I know this is not the most aggressive or optimum cam for my combo, but I don't plan on making a ton of horsepower.
Like Grady said, one of if not the biggest 'tune decider' is the injectors. I haven't tuned my engine yet because I still need an intake, and with that comes the injector install.
With putting the heads on, you might be okay. But with the heads AND the intake, your are going to be straining those stock injectors. And you will need larger ones, and a tune.
The best advice myself and others can give you, is to PLAN AHEAD. Figure out what your goals are, what you definately want out of the car, and assemble the parts to make it happen.
On something as important as a tune, don't skimp on it. Better safe than sorry.
This cam only has .480 lift, and works well with the stock ECU.
I put this cam in because the heads were being replaced on the motor, and I figured 'why not while I'm in there.'
I know this is not the most aggressive or optimum cam for my combo, but I don't plan on making a ton of horsepower.
Like Grady said, one of if not the biggest 'tune decider' is the injectors. I haven't tuned my engine yet because I still need an intake, and with that comes the injector install.
With putting the heads on, you might be okay. But with the heads AND the intake, your are going to be straining those stock injectors. And you will need larger ones, and a tune.
The best advice myself and others can give you, is to PLAN AHEAD. Figure out what your goals are, what you definately want out of the car, and assemble the parts to make it happen.
On something as important as a tune, don't skimp on it. Better safe than sorry.
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