Contour Enthusiasts Group Archives Forums Modifications Duratec Performance Recalibrating a Pro-M 75mm

Originally posted by cvkillacontour98:

---

i have a 75mm prom and it worked good untill i switched from a modified s.e. air box to a modified svt air box. the pro m maf doesn have a better internal design though. it looks less estrictive. is there any way to convert to a m.a.p. sensor.

---

Originally posted by 99cougar:

---

[quote=warmonger

WOW. Don't do that.
With all the new tech that has released for the Contour/Cougar in the last 2 years there is NO reason for that. Not to mention that is a hit or miss thing ANYWAY, and if ProM is still in business it will cost you a good chunk.
The easy way is to just retune your pcm.
Besides, that recalibration crap doesn't work on our cars for fuel adjustments more than say 20% and even if it gets it close you will have unknow problems that crop up as a result of the load miscalculations that are caused in the PCM from the recalibrated MAF.

Get an XCAL2 with your stock code, 24# injectors, and a MAF transfer function matched to your ProM75mm. Then you will be in business.

---

Ok. Thay is what i wanted to know. I have the PRP, but i wasn't sure if the MAF HAD TO BE programmed for your injectors. So i can just use Advantage to setup a Pro-M 75mm MAF to run on some 24# Accel's i have??? I kinda have another car to drive that gets about 40mpg so i wanted to start seriously messing with this software i spent 600 bucks on lol.

I am getting pretty familiar with the software now...but i really do not know how to come up with a MAF Transfer Function. Isn't there a "manual" that SCT makes that explains how to tune using their software?

And just to get this straight...if i buy a Pro-M 75mm MAF i will not have to get it reprogrammed for injectors...i can tune it in using the software i already have correct?

---

Yes and yes.

Demon SVT tuned in his ProM maf very nicely and still uses it. As long as it is working fine and consistently then there is no problem using the ProM.

If you don't have the sheet on the pro-m then you have to use a little reasoning to get into the ballpark so you can figure out the transfer function.

Here is how you do it:
1. determine what car/engine the pro-m was designed for
2. determine what injector size it was altered to meet
3. Grab the stock MAF transfer function for the car in step 1 and load the values of airflow (in kg/hr or cfm or whatever) versus voltage into an excel spreadsheet in two columns.
4. Ask yourself: Is the ProM sized for injectors that are different than the car in step one originally came with?
5. Calculate percent difference in injector size then multiply the airflow values in your spreadsheet by this percent difference and create a new row of values.

This is a ballpark figure for the ProM transfer function that you can load into your PRP software. You need something like 30 datapoints for loading into the software, AND you will need to convert to mass/tic measurements.
This is really just another multiplier so you can make another column next to your computed PRoM data and multiply it by the correct scalar.

I'm feeling nice so I'll look it up for you
Divide by 15,000,000 or 15x10^-7 if you prefer scientific notation.
So you you take all cells with the computed ProM function (corrected for injector size) and then divide each number by 15E-7 and you will have a value in mass/tic that you can load directly into the PRP software.
This just gets you into the ballpark now and you will have to pay attention to your long-term fuel trims to see how far off the this will be.
Lets say for example after one day of driving on this new computed Maf function you observe most of the fuel trims to be -8% to -15% at various rpms when you datalog. Well take that as about an average of 10% too rich, then go to your spreadsheet and multiply all values by about 0.90 or 90% and reload the function into your PRP. The drive and retest.

Lets say that at idle your Longterm fuel trims are showing small values of +3 left bank and -5 right bank. Within +/- 5% you should leave the Maf function alone at idle, assuming your idle quality is good. However, when you are driving around at 50mph cruise, the fuel trims are +10% and +13% on each bank. The plus values show that at that driving range you are too lean. The cruise portion is going to be in the 1.5-2.5 volts range (normally) and you will have to correct that. THe idle portion of the MAF flow usually runs from about 0.6volts to about 1.0volts. In this example your idle is good but your cruise is not. So you will have to multiply the 1.5-2.5% range by 1.10 or add and extra 10% to the curve.

At this point you will be manipulating pieces of the function and the function will no longer be smooth. Graph the function in excel. Look at the general trend of the graph and see what the shape of the curve should look like if it were smooth. They usually look like a weak exponential or a wierd 3rd order polynomial (if you know anything about basic math). Whatever, thats just bonus info but all you've got to do is smooth the transition from Idle to Cruise voltages to finish the job.
Yes this means going value by value from around 1.0volts to 1.5 or higher and "tapering" the multiplier from nothing at idle up to 10% more fuel at cruise, then you may as well pull that 10% all the way to 5Volts.

right?
If you play with these curves in excel a couple of times you'll get a feel for how to dial this in. If you have a wideband you then test your WOT values, or get on a dyno. Then you can finish your MAF function because it usually takes WOT test with a wideband to truly determine what the MAF function is above say 3volts. Once you do that, re-smooth out the function so that it is a nice curve and load it into your car, clear the memory and drive it. Viola, you have a perfectly tuned-in MAF. The beauty of this is that you can boost all day long and the changes in fuel will automatically be calculated for as long as you are drawing in air within the MAF's range and the PCM will keep the A/F right in a safe range the whole time!

You see, this is the kind of Post that I wanted to have a ProRacer pack tuning forum for.