Injectors and MAF for 94 cobra 331

blkcobra50 · Dec 5, 2006

Since I put a 331 in my cobra I have retained the stock MAF w/24 lb injectors. I have posted to see what people think about going with 30 lb injectors and proper MAF. For cobra's, is it still the same concept of getting a MAF that is calibrated to the specific size injector? I wasn't sure if the cobra computer acted differently with regard to MAF and injector size. Thanks for all the help.

Black95GTS · Dec 5, 2006

I think 30s would be a great idea for your combo!

If you change the MAF and the injectors, you're going to have tune your computer for it. You can't just drop them in. There are many ways to do this, via a pro tuner or do it yourself. See the 94-95 tuning section for a lot of info.

Adam

95strokerPSU · Dec 5, 2006

I'm selling my 24lbers and Pro-M 75mm bullet in favor of 30lbers and a lightning 90mm MAF. The Lightning meter is cheaper than Pro-M/PMAS and supposedly more accurate.

I don't know what the cobra computer does with a calibrated MAF.

blkcobra50 · Dec 5, 2006

That is what i thought. The cobra computer was setup for a specific size injector not the MAF. I will most likely buy some 30's and a lightning MAF when I talk to the guy who I want to tune it. Thanks for your help.

BlackVert · Dec 5, 2006

30#ers would be good for your setup

if you use your stock tune, the computer will think your load is higher than it actually is (it will think the air is going cylinders that are smaller than they actually are) , so it will pull timing and add fuel. bottom line ... you will be leaving power on the table and get worse gas mileage.

at the very least, the computer needs to know that it is dealing with a 331ci engine, so it can make reasonable decisions how much air the cylinders can handle and the load the engine is under. load is what it uses for most of its other decisions like fuel and spark timing.

and accurate information about what the maf voltage really means and the size of the injectors can only help it to make the right decisions.

you have probably spent alot of $$$ on this motor, do yourself the favor of getting a good tune for it.

blkcobra50 · Dec 5, 2006

you are right on the money spent on my motor so the tune is the next thing on the list. I would like to get the most power i can out of my setup. I need to talk to the tuner and see what he suggests I do.

WhiteDevil · Dec 5, 2006

Yah 30lb injectors and a PMAS or LMAF. Then get your car tuned!

final5-0 · Dec 5, 2006

You have to be pegging that little meter
considering
I did it with my smaller 302

It really is not an apples to apples comparison when you compare how Ford deals with inj/maf size and how the after market maf manufactures do it.

In your case ... your meter is too small simply because your 331 generates an airflow and maf voltage greater than the oem meter can accurately report to the pcm.

Also ... you have gone beyond the limits of those 24's if you stay with the method of how Ford does it. Remember, they do not use elevated fuel pressure. You may have an afpr, but you can only fudge so much with elevated pressure

I would much rather use a Self Tune or Pro Tune to tell the pcm the actual airflow (maf transfer curve) and inj size being used

as opposed

to using the maf manufactures cheat method of a meter caled for a particular size inj like Chris talked about above where your load factor gets all hosed.

So many, many things in the pcm's programming are based upon that load factor

That is the main reason ... the cheat method works better with the Fox Stangs and not all that great with our Stangs

Fox pcm's are rpm based where ours are load based.

Grady

blksn955.o · Dec 5, 2006

With a decent 331 with some good heads I would almost say go bigger than 30's to like maybe 36lbers. I thought about running 30s on my 306 and still may go that way. Not that you "have" to just maybe go alittle bigger and have some room to grow as far as what your inj. can handle or at least take some load off them.

blkcobra50 · Dec 6, 2006

Grady,
Thanks for the post. Will definitely be going for a pro tune. I do still have to talk to the guy a buddy of mine knows who tunes these things. Bigger MAF, bigger injectors are a must. Would you say to go bigger than 30s? Who makes 36lbers?

95strokerPSU · Dec 6, 2006

FMS makes 36lbers, but I don't think you'll need them unless you plan on adding a power adder.

blkcobra50 · Dec 6, 2006

no poweradders...ok 30's and LMAF with tune! Sounds great.

Is it worth hanging onto a stock cobra upper and lower. and gt40 heads??? I could sell those and probably get the injectors and maf with the $$$$.

WhiteDevil · Dec 6, 2006

Im pretty sure that FMS doesntmake 36# anymore. I looked all over the place for 36# injectors over the summer for my 347 and only found accell.

final5-0 · Dec 6, 2006

blkcobra50 said:
Grady,
Thanks for the post. Will definitely be going for a pro tune. I do still have to talk to the guy a buddy of mine knows who tunes these things. Bigger MAF, bigger injectors are a must. Would you say to go bigger than 30s? Who makes 36lbers?

Tough call on your inj size Q

If I was doing a stroker, I'd be using larger than 30's

but see it from my perspective ... if you will

1) It would be a 347
and
I wouldn't be stopping at 6K
just consider the amount of load a combo like that would produce

Example: like 3rd or 4th gear at mid range with the rpm quickly climbing ...
Epecially in 4th where the wind resistance if working against you ...
Man O Man ... the load is gonna be huge with a big ole stroker
and
that ain't no time to go lean

2) I run stock fuel pressure ... that means ANY size inj I would choose ...
won't act as a larger inj
like can happen
when peeps run elevated pressures

3) I have pcm access which gives me ...
the ability to adjust for low pulse width over fat conditions which can happen ...
when you go past 24's and cause all kinds of drivability issues

Honestly Though ... I can't imagine anyone
going to the trouble & expense of doing a stroker
and
think they are gonna tune it with an afpr & dizzy twisting

I think its best for you to ask your Tuner about your inj size concerns

Let us know what you find out

Grady

blkcobra50 · Dec 6, 2006

I am going to call the tuner tomorrow to see what he recommends I do.

In a perfect world I would have done a MUCH different combo but that is what I had readily available and was pretty much within budget.

Thanks again guys,
John

blkcobra50 · Dec 8, 2006

Well I spoke to the tuner last night for a while and he gave me some good pointers. He recommended that I go with a PMAS 80mm MAF and a AFM powerpipe. I asked him about the size injectors and he said that 24s are fine for a non-blown application. I trust this guys judgement as he has a wealth of knowledge with regard to mustangs. He also said that in my case with the cobra computer, it pulls timing as I really get on it. So in order to get the most out of my combo he told me to get some dyno time and have chip burned taking care of those computer functions.

The other route he specified was to get a PMS but with that comes more $$$ and still dyno time. He also said that I would need a new fan controller (I forget the actual reasoning). I think it was something like in the cobras the fan is controlled by the computer. The fan comes on at around 205 degrees. That would need to be changed.

I do not know what I should do. I will be getting the MAF and mostly likely the powerpipe but as for the dynoing I am still up in the air. I do not see myself modding this car any more than it is now after I do the MAF. So having said that a chip might be the best choice.

What do you guys think?

final5-0 · Dec 8, 2006

blkcobra50 said:
Well I spoke to the tuner last night for a while and he gave me some good pointers. He recommended that I go with a PMAS 80mm MAF and a AFM powerpipe. I asked him about the size injectors and he said that 24s are fine for a non-blown application. I trust this guys judgement as he has a wealth of knowledge with regard to mustangs. He also said that in my case with the cobra computer, it pulls timing as I really get on it. So in order to get the most out of my combo he told me to get some dyno time and have chip burned taking care of those computer functions.

The other route he specified was to get a PMS but with that comes more $$$ and still dyno time. He also said that I would need a new fan controller (I forget the actual reasoning). I think it was something like in the cobras the fan is controlled by the computer. The fan comes on at around 205 degrees. That would need to be changed.

I do not know what I should do. I will be getting the MAF and mostly likely the powerpipe but as for the dynoing I am still up in the air. I do not see myself modding this car any more than it is now after I do the MAF. So having said that a chip might be the best choice.

What do you guys think?

What I think is .......... I'd just tune it myself

Here are my thoughts about each issue in the order you listed them

Thats a good meter ... I got no probs with the choice

Believe I could fab up a pipe for a lot less $ than the AFM

I would not sleep good at night with 24's in my Stroker

Now ... Lets talk about that pulling timing subject

True ... you do have a tip in retard
but
The GT pcm retards exactly the same amount

I mean ... its not like it don't advance spark as the rpms climb just because its a Cobra pcm

Actually ... If I was gonna pick from the two pcm's to use without a tune for a h/c/i combo ... I'd run away from the GT to the Cobra as fast as I could

As for the dyno time

Sure, with a tune you'll fix issues with:
load factor
maf/inj's
various other little adjustments for good drivability (closed loop)
spark/fuel tables for max power (open loop)

As for the fan temps

Maybe he is saying ........
the PMS may not have access to that particular pcm parameter

About that last paragraph

If you wanna bypass a lot of dyno time

Thats one of the benefits of Self Tuning
The street is a whole bunch cheaper

Seriously Speaking Though

So many more options become available to you .........
which you have control over I might add
when you Self Tune

As for this guy and your feeling good about him tuning your Stang

If he put your Stang on the rollers, I'd have to think he could burn you a chip to take care of all your concerns

So ... the stuff I said above about the different pcm's would be moot when he does his dyno tuning thing

the 24's however

I'd wanna be hittin em with extra pressure to make them act bigger

Grady

blkcobra50 · Dec 8, 2006

I know what you are saying about the injectors. I would have thought to go bigger than 24's but I trust him. Maybe the only way I can get away with 24s is because of the Ecam?

Self tuning would be great because then I would learn a whole lof of various pcm parameters that I do not know now.

What kind of power/driveability increase would I see putting the car on the dyno rather than self tuning with a pms on the street?

blkcobra50 · Dec 8, 2006

What tuning device should I use for self tuning?

Black95GTS · Dec 8, 2006

blkcobra50 said:
What tuning device should I use for self tuning?

There's many threads about this in the tuning section. Basically its PMS vs. TwEECer. You'll also need a laptop and a wideband O2 sensor to self tune. And get ready to do some research no matter which method you chose.

I know you respect your tuner, but 24 pound injectors aren't enough for a 331 HCI. 24 pound injectors aren't enough for most 302 HCIs, unless you up the fuel pressure.

Adam

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