fuel/induction gurus....maf help

[nitrous_bob]

ok to start off, i have built my curent '93 notch about identical to my old '89 notch.

i expected the car to run about 3 tenths slower due to full suspension and power everything.

it was over 7 tenths slower, couldn't get out of the 14's , running 4.10's , et street radials, lt's , on a 5-speed car.

my '89 went 13.20's like this , best run of the night was 14.02 @ 97 w/ a 1.83 60'

now here is my question, the car has a supercoupe meter on it. it's a sc meter for sure, i checked the numbers.

could this be affecting performance? it smells super phat but fp at idle (vac on) is about 32 psi

it appears the sc meter is a 70mm (comparing numbers to a 5.0 meter)
but i'm wondering if the sampling tube is different causing a superrich condition???????????

on the 80 shot NOS 5115 dry kit, it went 13.15@105 1.82 60'
but the old car went 12.52@109

it knocked off the right ET on the juice for the power gain, but so slow to begin with.

help me out guys

 

[Daggar]

It may not be the "sample tube" at all. The transfer functions between the meters may be off all the way through it usuable CFM. Could be fat in some portions while lean in others. I can't say I recall ever looking at the transfer function for a super coup meter so I couldn't tell you what the differences were.

 

[vristang]

Wouldn't one have to load an appropriate MAF Transfer for that Tube?

I can't see how you could expect the computer to know how much air was flowing through that meter. The calibration is going to be off.
I am sure the SC MAF Transfer is not the same as the MAF Transfer loaded on the A9* computer nitrous_bob is running, so the 70mm maf and 70mm mas will not work.
Using the 70mm maf and A9* mas would not work either, as the mas would not be interpreting the signal properly from the maf.

I just don't see any way for this to work without a tuner.

Am I wrong?

I can't say for sure that this is your problem nitrous_bob, but I am not sure this setup is going to work.

What are you using...
computer, A9L or what?
MAS (the sensor) for the stock 55mm MAF on the 5.0?
MAS for the 70mm SC?

jason

 

[Daggar]

Well you're kinda on the right track there vristang.

There's more to it than just a sample tube though. For instance... let's take a C&L meter with electronics from a Lightning. You can swap sample tubes until the cows come home. You may even find one that works well at certain parts of the power range. The thing is: the computers are different and the tranfer functions themselves between the meters would not line up if you graphed them together. You might see something like:

OEM Fox meter:

100 CFM = 0.5v
300 CFM = 1.0v
600 CFM = 1.5v
etc.

Whereas the Lightning meter might look something like:

100 CFM = 0.5v
300 CFM = 0.7v
600 CFM = 1.0v

I just used random numbers to illustrate what I mean but I'm sure you get the point.

... but yes... under those circumstances, a transfer function would need to be loaded but not just for the sample tube, but for the meter itself!

 

[nitrous_bob]

ok, the sensor and meter are both from the SC

this was on the car since i've had it , and i just realized it.

the computer i am assuming is the stock stang puter.
but i'll have to pop the kick panel and check for sure.

the car was all stock excaept for some simple boltons, exhaust , suspension .... little stuff

 

[vristang]

Daggar-
I get ya.
I guess the proper phrasing might be closer to - The MAF Transfer in the computer must match the MAF/MAS combination.

I had to learn all that when I started using the TwEECer.
Turns out C&L does not publish any MAF Transfers for their 73mm tube with a 70mm MAS (regardless of sample tube selection). I had to run a 55mm MAS in order to get a good starting point MAF Transfer.

So, for nitrous_bob...
I guess if the computer is a stock computer you will have an issue to sort out.
You may still find a chip on the computer though?

jason

 

[Daggar]

Daggar-
I guess the proper phrasing might be closer to - The MAF Transfer in the computer must match the MAF/MAS combination.

jason

Perfect... I have just as much difficulty explaining it as anyone (I'm sure you also know that it seems allot harder to explain than to understand, largely due ot the misconception that meters are calibrated to injector size as opposed to the computer's pre-programmed transfer function) but yeah... the transfer function in the computer must be a match for the meter.

 

[Daggar]

Hey Bob,

You say that the meter and computer have been in the car from the get-go. Have you also had the problem all along? --or-- is this a problem that's cropped up recently?

 

[nitrous_bob]

Hey Bob,

You say that the meter and computer have been in the car from the get-go. Have you also had the problem all along? --or-- is this a problem that's cropped up recently?

i haven't had the car 1 year yet.

but yes, been in it since i got it, and not a new prob. i only realized it from this recent trip to the track. my first trip it went 14.60's on 2.73's and et street rad's , but it was bogging , so i blamed the bad times from too much tire and not enuff gear (my '88 notch all stock went 14.20's 2.73 gears and street tires). the smell has been all along.

i am inclined to believe now, that the sensor is calibrated for 30 lb. injectors. i am not 100% sure, but but so far thats what i found. i'm gonna get a different maf (stocker ) to see. they are a dime a dozen for the stocker.

but based on this meter , if it is in fact cal'd for 30 lb'ers and i have 19's.....do you see 1/2 second or more from being too phat. i have to believe so...but i am just hoping too.

and guys thanks a ton. you have no idea how angry i was at the track...my buddies aod car set up like me was giving me a stomping.