Question: Recalibrating computer for fuel consumption accuracy?

[86-ZZ3]

I've changed the injector size (and fuel pressure) in my '86. Just wondering if there's a way to recalibrate the dash computer to accurately reflect fuel consumption in the MEMCAL or elsewhere?

 

[Tin butcher]

To get the fuel mileage feature accurate, you will have to have the programming in the MEMCAL modified. You need to find someone with the equipment to erase and burn chips. Since you changed injector size, they will want to datalog to check the BLMs (fuel mixture) and adjust the injector pulse before they erase and burn the chip.

I just read your other post - you have already found someone to burn chips. If he is using a disassembler program for a Camaro, the location won't show up to change the corvette display. Your 86 uses a 32 mask, I don't know that location. In 87 they use the 32B mask - "In 32B, the display gallons/hr constant is located at location 712 with a default value of 122 (decimal) or 7A (hex). This raw value (in decimal)must be divided by 32 to convert to gallons/hour." (I got this information from someone a lot smarter than me!) If your tuner can find the location, he can either edit it in raw hex or add the location to his program. Hopefully this will help.

 

[Tin butcher]

For those using the 1989 program with 6E, the address for the fuel display is 620. The default value is 3.776. I found instructions on another forum and was able to add the fuel display into my Tuner Pro program.

 

[Hib Halverson]

I've changed the injector size (and fuel pressure) in my '86. Just wondering if there's a way to recalibrate the dash computer to accurately reflect fuel consumption in the MEMCAL or elsewhere?

It is true that to get a return of accurate fuel economy display may require a custom calibration, let me ask you....why did you change the injector flow rating?

 

[vetteoz]

In 87 they use the 32B mask - "In 32B, the display gallons/hr constant is located at location 712 with a default value of 122 (decimal) or 7A (hex). This raw value (in decimal)must be divided by 32 to convert to gallons/hour."

Nice info ,
got any numbers on how to convert to imperial gallons instead of the default US gal?

 

[tequilaboy]

From your other posts, it is not clear to me which mask you are using, $32, $32B or $6E.

For the 1986 $32 Mask:
The address for the gallons/hr display constant is: 70C.

For the 1987-88 $32B Mask:
The address for the gallons/hr display constant is: 712

For the 1989 $6E Mask (as already stated above):
The address for the gallons/hr display constant is: 620

This value should be adjusted along with the injector constants. Typicaly using 6 lbs./gallon for the conversion.

Note: If there is still significant error in the displayed economy (assuming that fuel pressure has also been taken into consideration), this is a good indication that the injector offsets for battery voltage and low pulse widths may also need to be corrected for the specific injectors in use.

Here is an excerpt from the $32 Mask:
;------------------------------------------------------
; DISPLAY Fuel Rate Scale Factors
;
;------------------------------------------------------
LC70C: FCB 122 ; Gals/Hr Inj flow rate
; CALIB = Arg * 32, (3.8125 G/Hr)

For conversion to imperial gallons, just divide the us gallons/hr display value by 1.2 which would result in a flow rate of 3.175 imp. gallons/hr for the default value.

Change 122 (decimal) -> 102 (decimal) or 7A (hex) -> 66 (hex).

 

[vetteoz]

For conversion to imperial gallons, just divide the us gallons/hr display value by 1.2 which would result in a flow rate of 3.175 imp. gallons/hr for the default value.

Change 122 (decimal) -> 102 (decimal) or 7A (hex) -> 66 (hex).

Thanks

 

[Tin butcher]

I’d like to welcome tequilaboy to this forum. Tuning my vette would have not been possible without him being willing to share his knowledge. I learn something every time I read one of his posts. I used his instructions to add the fuel display into my Tuner Pro program! Of course, what makes forums work is everyone willing to share their knowledge.

 

[roger longman]

Hi Tin, like Hib I would also be pleased to know the reason for changing the injector flow rating. Roger.

 

[aklim]

Hi Tin, like Hib I would also be pleased to know the reason for changing the injector flow rating. Roger.

Well, if you use say 42pph injectors like I do or even 36pph ones, your mpg calculation in the computer will be so far off that you will look like you are getting 40 mpg when you are getting 15.

 

[86-ZZ3]

For those using the 1989 program with 6E, the address for the fuel display is 620. The default value is 3.776. I found instructions on another forum and was able to add the fuel display into my Tuner Pro program.

Hi, could you post a link to that forum where you found this info, or give me a link? Thanks

 

[86-ZZ3]

let me ask you....why did you change the injector flow rating?

Engine that can take more fuel/make more power?

 

[Hib Halverson]

Engine that can take more fuel/make more power?

A question in reply to a question.
Hmm...

Good luck with the project.

 

[Tin butcher]

Hi, could you post a link to that forum where you found this info, or give me a link? Thanks

I couldn't get the link to work - sent you a PM

 

[86-ZZ3]

A question in reply to a question.
Hmm...

Good luck with the project.

The ZZ3 crate motor has been in my car for 14 years. Spec'd at 345 hp on the stand with Rochester Q-jet, headers and and mine can breath (tri-Y headers and aftermarket intake). 26 lb injectors aren't out of order (I think the 22 lb injectors max out at 275-290 hp?) . Just thought it'd be good to have a real tune for it.

 

[roger longman]

Hi, I get the line of thought but I don't understand the correlation. Over to you Hib. Roger.

 

[vetteoz]

your mpg calculation in the computer will be so far off that you will look like you are getting 40 mpg when you are getting 15.

My hot 383 HSR with 30lbs shows same mpg as the stocker.