Which computer can i get?

nmcgrawj · Sep 7, 2005

final5-0 said:
Nate

I only asked about the maf and inj's cause the info ain't in your sig and I can't remember everybody's combos details.Gotcha

I'm know nothing about tuning with a PMS but do you build a maf curve? Do you tell the pcm the size inj's your using? Nope

What makes you think the cal is off?Well its pretty common rightbefore they closed...some say the last 6 months at prom there were some pretty shady calibrations. I am having to retune by A TON in comparison to other guys with the same MAF and same injector size.

Since you are using 30's then the first thing I would think is that ProM was told you have a GT and 30lb inj's. They then would set the maf up or, calibrate it, based on that info.

If you told them you had 30's and a COBRA then that could be a whole different story. I told them GT but the calibration still sucks

Again, do you use your PMS to build a maf transfer curve based on the flow sheet ProM sent you and do you use your PMS to tell the pcm the inj size.

I am trying to see if you tune with the PMS by using ProM's cheat method or do you use the PMS to tell the pcm the truth about air flow and inj size.

Grady

You use the PMS to adjust timing and fuel at different levels. Thats it. No more complex than that really.

I think my tune MIGHT be closer to a cobra's "calibration" because i am having to add a lot of fuel to make up for the "slack" in comparison to other guys with similar combos with the same maf/injector setup. This is how i am thinking of it....

A GT will have a calibration that adds more fuel to reach 30lb than factory. A cobra will have LESS fuel added to reach the 30lb need. Since im having to add extra fuel...im thinking i have a cobra "like" calibration with a GT computer anticiapting 19lb injectors so its falling short. Thus, the PMS needs to add fuel. Make any sense?

final5-0 · Sep 7, 2005

nmcgrawj said:
You use the PMS to adjust timing and fuel at different levels. Thats it. No more complex than that really.

I think my tune MIGHT be closer to a cobra's "calibration" because i am having to add a lot of fuel to make up for the "slack" in comparison to other guys with similar combos with the same maf/injector setup. This is how i am thinking of it....

A GT will have a calibration that adds more fuel to reach 30lb than factory. A cobra will have LESS fuel added to reach the 30lb need. Since im having to add extra fuel...im thinking i have a cobra "like" calibration with a GT computer anticiapting 19lb injectors so its falling short. Thus, the PMS needs to add fuel. Make any sense?

Great info and thanks for the quick schooling on the PMS. Now I kinda sorta know which direction to go with my thoughts.

Before I start I want to say that this info makes since to me but it is pretty general and it would be my hope some of the other peeps who tune will get involved to give their two cents worth also.

First of all, ProM uses their cheat method or maf caled to an injector size based from what you tell them about what pcm and inj size you are using.

They know all too well that a GT pcm is set up for 19's and a Cobra pcm is set up for 24's.

If you were to use a Cobra pcm then that whole system of theirs is gonna be all outa whack.

It seems to me that based on what you've told me about the PMS, you need to use a GT pcm cause you have no way to be flexable about the maf transfer or inj size.

am I making any sense

or

have I confused more than I have helped

btw, if you really want to understand about how ProM does their cheat method, calibration thing, or in other words, makes the pcm think something is happening that is not ............................................

check out this link http://www.superstang.com/maf.htm

mafs & injs and how they work together is IMHO, one of the most misunderstood things about modding Stangs and this link does a pretty good job of making it not too difficult to grasp.

Grady

nmcgrawj · Sep 7, 2005

I gotcha Grady and if this calibration was RIGHT or close to it then i would agree. But its SOOO far off that i think its closer to a cobra than a GT.

BUT it doesnt matter...i dont have compression on 5,6,7,1,2 so its not a eec or dizzy issue. Thanks for the help fellas...im gonna go beat up a brick wall now

95COBRA241 · Sep 7, 2005

Hey Grady,

Great link, I read it like 3x's already. I think you do a wonderful service of educating us Neewbies on the finer points of EEC tuning.

In the article it states that if you add a larger MAF (I assume >radius and > inj. lb calibration vs stock) such as say a 90mm caled for 83lb injectors that you don't necessarily have to install 83lb inj's. You can "trick" the pcm into thinking u do with the twEECer or EEC tuner. 2 questions about this.

1. Say u have 19lb injectors, there must a flow limit. Can the pcm really "trick" a 19lb injector into thinking its a 83lb inj. or will that max out the 19lb'ers?

2. My 347 build up will hopefully include reusing my 24lb injectors, Pro-M 77mm MAF (Cobra caled for 24lbs), and a twEECer. Should I run short on fuel is it wiser to recal the MAF to (for arguments sake) 42lbs and "trick" the pcm using the twEECer to think I aso changed to 42lb injectors?
or
change the 24lb injectors to 42lb injectors and "trick" the pcm using the TwEECer into thinking that the MAF has also been changed/recaled to 42lbs?

I hope that makes sense?

nmcgrawj · Sep 7, 2005

95COBRA241 said:
Hey Grady,

Great link, I read it like 3x's already. I think you do a wonderful service of educating us Neewbies on the finer points of EEC tuning.

In the article it states that if you add a larger MAF (I assume >radius and > inj. lb calibration vs stock) such as say a 90mm caled for 83lb injectors that you don't necessarily have to install 83lb inj's. You can "trick" the pcm into thinking u do with the twEECer or EEC tuner. 2 questions about this.

1. Say u have 19lb injectors, there must a flow limit. Can the pcm really "trick" a 19lb injector into thinking its a 83lb inj. or will that max out the 19lb'ers?

2. My 347 build up will hopefully include reusing my 24lb injectors, Pro-M 77mm MAF (Cobra caled for 24lbs), and a twEECer. Should I run short on fuel is it wiser to recal the MAF to (for arguments sake) 42lbs and "trick" the pcm using the twEECer to think I aso changed to 42lb injectors?
or
change the 24lb injectors to 42lb injectors and "trick" the pcm using the TwEECer into thinking that the MAF has also been changed/recaled to 42lbs?

I hope that makes sense?

Injectors run on that scale of power made...so 24s are only good up to a certain point of power. I cant imagine the power pushed where 83s are needed.

You can increase the injector pulsewidth to get more fuel...but it comes to an end sooner or later. Thats when you reach that power level for that certain injector.

Im sure Grady can come in and explain it in a much more detailed and EDUCATED manner.

Pokageek · Sep 7, 2005

Ok, dumb question..can you turn OFF your egr with a tweecer? Mine is leaking and I really don't want it on the car anyway.

a50sn95 · Sep 7, 2005

To understand this with regard to the TWEECER, you have to separate the MAF and the
Injectors in your thinking. The MAF measures air, and the injectors dump in fuel. You have to remove the relation in your head with a tweecer

Back before the Tweecer (and other tuners), if you put in bigger injectors, you had no way of telling the computer that the injectors were bigger. The "trick" was to get a MAF that was re-calibrated to fool the computer to inject the proper amount of fuel with the bigger injectors.
A MAF cal'd for 19# injectors will only measure a maximum of 800CFM of air at 5v.(I'm just making up the numbers, since I don't have the actuals in front of me). So once the engine is drawing more than 800CFM, the computer only gets a 5v signal. If you are really passing 1200CFM, you will be WAYYYY lean, as it doesn't matter what the size of the injectors is, it's only registering 800cfm, so it's injecting the right amount of fuel for 800cfm.
The idea is to get the biggest MAF you can, and enter the curve in the Tweecer. As long as you never exceed 5v, you'll be golden. The BA2800 measures 2800 cfm at 5v, which is a lot of air.
The injectors are sized to the horspower they must support. There is only a certain amount of time available for the injector to inject the fuel requred. Once the injector cannot inject enough fuel in the available time, it's to small, and you risk running lean again.
So , Answers:
1. No, you cannot trick the injector to do anything. Short of having them pulled and modified, a 19 lb injector will always be a 19lb injector. With a Tweecer, you can run the MAF for the 83's, and still use the 19's because you can alter the MAF transfer table the computer uses when it calculates the required fuel. A 19lb INJECTOR IS ONLY GOOD TO ABOUT 350hp, the MAF can't make it inject MORE fuel....

2. Ther really is no shortcut available to you. If you have a MAF calibrated for 24's, you CAN use it, but you risk maxing out the MAF(hitting 5v's while still increasing the amount of air going through it.) which can lead to a lean condition. Same for the injectors. If you exceed thier capacity to deliver fuel (or exeeding the duty cycle), you'll lean it out.
The preferred method for me is to get a MAF for alot of air, which would give alot of room if I add something later. The only catch is that if my Tweecer dies, then the car probably won't run. In that case a correct MAF/Injector combo would at least get you home...

To be clear, using a Re-cald maf without altering the tables is actually tricking the computer. One of the downsides wiht our cars (94-95's) is that alot of the calculations used are also based off load, and this method also messes up the load calculations, which can put too much timing in or not enough, etc...

With the Tweecer, you enter the actual numbers for the maf, and the actual numbers for the injectors, and the computer uses acurate information to make it's calculations, without messing up the load calculations.

Sorry if I rambled, this is a confusing subject to understand. Once you get it, though.....

a50sn95 · Sep 7, 2005

Pokageek said:
Ok, dumb question..can you turn OFF your egr with a tweecer? Mine is leaking and I really don't want it on the car anyway.

Yes, one simple change....

final5-0 · Sep 7, 2005

95COBRA241 said:
In the article it states that if you add a larger MAF (I assume >radius and > inj. lb calibration vs stock) such as say a 90mm caled for 83lb injectors that you don't necessarily have to install 83lb inj's. You can "trick" the pcm into thinking u do with the twEECer or EEC tuner. 2 questions about this.

If you have the ability to change the pcm values, you usually tell the pcm the truth about two things
1) air flow
2) inj size

Mafs and air flow first

In the article you saw that the pcm uses voltage from the maf to determine air flow. That voltage range is 0.0 to 5.0 volts and that is pretty much cast in stone.

Two quick examples to help show things more clearly......I hope

Stock cobra and my sig combo

The cobra will use lets say 65% of the range of the maf and that is cause that is the amount of air flow it can generate.

My combo using the same maf as the Cobra above used 101% or as some describe it, the combo was pegging the maf. The maf was no longer up to the job for that combo. ProM sent me a new maf with a 30lb cal and supplied the spec sheet showing voltage to air flow values as they tested it. As the article stated both mafs send to the pcm voltages in the 0.0 to 5.0 range. The 30lb caled maf uses that same fixed range of voltage to report more air flow to the pcm, again as the article stated.

Can you see the point of how this maf thing is all about air flow.

Think about a forced induction combo and how it is gonna produce way more air flow than my little combo. It also has to stay in that same fixed voltage range as that is all the pcm can deal with. It most likely would be a 42lb caled maf but everything is the same but with more air flow.

Injectors and their size

I won't get into details but in our two examples above.

Stock Cobra has 24's
My combo with the same maf has 30's

There are formulas to determine inj size but I'm sure most peeps can see that you can only go so far with 19's. Look at what Ford did between the GT & Cobra. They thought the extra power of the Cobra over the GT made 24's a necessity.

For my combo, I ran all the numbers and I thought 30's were what I needed to feel comfortable.

To bring it all together ..............................

In my sig you see that I used the Tweecer to tell the pcm that 30lb inj's were being used and the (at that time) stock GT maf transfer was in place. The combo just flowed a bit more air than I thought it might so the little maf was barely pegged.

1. Say u have 19lb injectors, there must a flow limit.

Just use the inj size formulas to determine the size needed but don't forget those formulas use FWHP and most of us think in terms of RWHP.

Can the pcm really "trick" a 19lb injector into thinking its a 83lb inj. or will that max out the 19lb'ers?

The answer is in the above info.

2. My 347 build up will hopefully include reusing my 24lb injectors, Pro-M 77mm MAF (Cobra caled for 24lbs), and a twEECer. Should I run short on fuel is it wiser to recal the MAF to (for arguments sake) 42lbs and "trick" the pcm using the twEECer to think I aso changed to 42lb injectors?
or
change the 24lb injectors to 42lb injectors and "trick" the pcm using the TwEECer into thinking that the MAF has also been changed/recaled to 42lbs?

I hope that makes sense?

I hope you can see the answer in the above info.

I would run no less than 30's with that combo and that is just off the top of my head or my gut feeling. You would, without a doubt, want to run all of the necessary info about your combo through one of the many inj size formulas to make sure things are like they should be.

Its getting late and if I did not do a good enough job of laying this stuff out so it can be understood, read that article again as those guys do better at helping peeps understand than I can. We can talk tomorrow if you guys want to.

To be honest with you, I had to do a good bit of research before I could get my head around the whole maf/inj thing myself. It can be difficult to grasp IMHO.

Grady

95COBRA241 · Sep 8, 2005

Thank yous to both Grady & a50sn95.

I think I'll do the injector research for my combo and the add both bigger injectors (30, 36, or 38), AND a recaled MAF for the final injector size. I thought I could save money by just having to change on or the other.

final5-0 · Sep 8, 2005

Good job of description.

Grady

a50sn95 said:
To understand this with regard to the TWEECER, you have to separate the MAF and the
Injectors in your thinking. The MAF measures air, and the injectors dump in fuel. You have to remove the relation in your head with a tweecer

Back before the Tweecer (and other tuners), if you put in bigger injectors, you had no way of telling the computer that the injectors were bigger. The "trick" was to get a MAF that was re-calibrated to fool the computer to inject the proper amount of fuel with the bigger injectors.
A MAF cal'd for 19# injectors will only measure a maximum of 800CFM of air at 5v.(I'm just making up the numbers, since I don't have the actuals in front of me). So once the engine is drawing more than 800CFM, the computer only gets a 5v signal. If you are really passing 1200CFM, you will be WAYYYY lean, as it doesn't matter what the size of the injectors is, it's only registering 800cfm, so it's injecting the right amount of fuel for 800cfm.
The idea is to get the biggest MAF you can, and enter the curve in the Tweecer. As long as you never exceed 5v, you'll be golden. The BA2800 measures 2800 cfm at 5v, which is a lot of air.
The injectors are sized to the horspower they must support. There is only a certain amount of time available for the injector to inject the fuel requred. Once the injector cannot inject enough fuel in the available time, it's to small, and you risk running lean again.
So , Answers:
1. No, you cannot trick the injector to do anything. Short of having them pulled and modified, a 19 lb injector will always be a 19lb injector. With a Tweecer, you can run the MAF for the 83's, and still use the 19's because you can alter the MAF transfer table the computer uses when it calculates the required fuel. A 19lb INJECTOR IS ONLY GOOD TO ABOUT 350hp, the MAF can't make it inject MORE fuel....

2. Ther really is no shortcut available to you. If you have a MAF calibrated for 24's, you CAN use it, but you risk maxing out the MAF(hitting 5v's while still increasing the amount of air going through it.) which can lead to a lean condition. Same for the injectors. If you exceed thier capacity to deliver fuel (or exeeding the duty cycle), you'll lean it out.
The preferred method for me is to get a MAF for alot of air, which would give alot of room if I add something later. The only catch is that if my Tweecer dies, then the car probably won't run. In that case a correct MAF/Injector combo would at least get you home...

To be clear, using a Re-cald maf without altering the tables is actually tricking the computer. One of the downsides wiht our cars (94-95's) is that alot of the calculations used are also based off load, and this method also messes up the load calculations, which can put too much timing in or not enough, etc...

With the Tweecer, you enter the actual numbers for the maf, and the actual numbers for the injectors, and the computer uses acurate information to make it's calculations, without messing up the load calculations.

Sorry if I rambled, this is a confusing subject to understand. Once you get it, though.....

SQUEEZE&STROKE · Sep 8, 2005

hey nmcgrawj clear out your PM's I have one to send to you...all hell I'll just post it...

That sucks major butt dude. Too bad you live so far away I would help you put a new one back together. If you want to go bigger cubes I have that 331 crank. Its brand new...still in the box. I'd trade that for the shifter too...I just want to get rid of it!

In response to your PM that your problems are due to your shortblock instead of the computer.

nmcgrawj · Sep 8, 2005

SQUEEZE&STROKE said:
hey nmcgrawj clear out your PM's I have one to send to you...all hell I'll just post it...

That sucks major butt dude. Too bad you live so far away I would help you put a new one back together. If you want to go bigger cubes I have that 331 crank. Its brand new...still in the box. I'd trade that for the shifter too...I just want to get rid of it!

In response to your PM that your problems are due to your shortblock instead of the computer.

Cleared....

Thanks man. And thanks for the offer. I WOULD take you up if i was till 302 based. But i stepped up to the 351 and got a "rebuilt" shortblock that i learned the hard way...only run rebuilt things that you know or have rebuilt.

Im gonna either just put a new piston in it or stroke it. Oh well, im pissed but you know what, i can just concentrate on my studies for now, save up, and plan to hit the streets in the spring.

Which computer can i get?

nmcgrawj

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