Fuel Consumption formula to use in adx file.

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JohnDee68
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Fuel Consumption formula to use in adx file.

Post by JohnDee68 »

Hi,
I am trying to calculate the instantaneous fuel consumption so it reads correct in the TunerProRT ADX i am using.

VX Commodore V6 3.8L Auto.

Has anyone actually got a correct formula for calculating such value ? The one which is in there doesn't seem to be correct: ( ( x / 100 ) / y ) * 100 where y seems to be VSS in Kph. Not sure what x represents.

I have been looking in to it and it seems valid to be able to use the likes of the MAF, AFR, and VSS to calculate instantaneous Litres per 100 KM per hour, but I cant seem to get it to read right.

I have tried similar to this, but does anybody know if this is on the right path to work it out or not ?

MAF divided by AFR should equal grams of fuel per second ( equates to same as milliliters per second)
Multiply result by 3600 to get mL per hour.
Then use VSS divided by mL per hour should get mL per hour per km ?

Kind regards

John.
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Re: Fuel Consumption formula to use in adx file.

Post by VX L67 Getrag »

it should be selecting packet offset 33 I believe & using this calc ((X/100)/Y)*100 & x link is native & y link is vss
JohnDee68
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Re: Fuel Consumption formula to use in adx file.

Post by JohnDee68 »

HI,
thanks for that.
that is whats in there already, though when i do a log from a trip, it has values in the inf. and high 60-80's l/100km. which is obviously wrong in its calculations somewhere. Yes, at times it does read a reasonable ecconomy value, though given the extreme high values it cant be confirmed the lower ones are even close to being correct.

I wonder if there is even some way that for my PCM ( 16269248) its not matching the data fields correctly? which i think is in the XDF and ADX files, if i understand TunerProRT correctly.

thank you.
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antus
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Re: Fuel Consumption formula to use in adx file.

Post by antus »

has it been tuned? someone could have lied to the computer about fuel flow rates etc, and you might be seeing what the computer is actually thinking is happening.
Have you read the FAQ? For lots of information and links to significant threads see here: http://pcmhacking.net/forums/viewtopic.php?f=7&t=1396
JohnDee68
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Re: Fuel Consumption formula to use in adx file.

Post by JohnDee68 »

Hi Antus,
I am suspecting its due to not ALL data being copied over to the cloned and a tester PCM when my origional failed. (Something I am asking in another post as to the OSE flash issue possibly a reason for missmatch?). Sorry i didnt know what to post in what topics.

To my knowledge, my origional PCM had never had a tune nor tamperred with before being in my posession back in 2004. Im not after more than the factory power from my car, just want factory performance and economy again, where possible. If the economy TunerProRT readings were to be correct, it could possibly average out to the poor 20mpg it physically does at the moment. Where it should be around the 30mpg plus. Ive ruled out prety much every possible physical part as being a cause to the economy drop, so feel and beleive its still computer related (or just tune) and the varient in the fuel consumption readings of well over 100L/km could be evident to the software in the PCM being the cause?

Edited: when i use the mode arrow option on the car to display realtime fuel use, it never goes above the 30 L/hr when the TunerProRt shows higher and above 100s, if that helps? Not sure where the dash gets its fuel use from, PCM i guess?

Id be happy to share a drive log, which might give a clue to the more experienced in helping to find whats happening?
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delcowizzid
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Re: Fuel Consumption formula to use in adx file.

Post by delcowizzid »

Cloning a pcm makes an exact copy and drives and operates just like your original I daily drive on a cloned vx ecu
If Its Got Gas Or Ass Count Me In.if it cant be fixed with a hammer you have an electrical problem
JohnDee68
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Re: Fuel Consumption formula to use in adx file.

Post by JohnDee68 »

Hi delcowizzid,
So if I understand correctly any memory address locations, for example bellow E00 would be likely just data which is used for the current hardware in the vehicle at that time ? Which might be the likes of its MAF air temps, EGR position, IAC Steps, etc i presume (maybe not exactly these types of hardware, but as an example) so at the end of the day they're really irrelevant to the Clone of the PCM's memory locations ?
JohnDee68
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Re: Fuel Consumption formula to use in adx file.

Post by JohnDee68 »

Hi all,

Just thought i'd update my findings on this one in case others may need to refer back to it or has the same issues in the future.

When i use the VX_V6_$BD_Enhanced_v0.9c.ADX ( a good definition file ) I found that on my Vx Wagon 8/2002 PCM the Fuel Consumption appeared to display incorrectly.

I have played with the formula and have managed to work out that under Fuel Consumption the conversion value of "x/100" seems to work correctly ( as the "((x/100)/y)*100" wasn't ) and now close if not identical to the same values of what shows on the instrument cluster as L/Hr. This eliminates the 100+ & "inf" being shown on tables and graphs.

I think i have done it correctly but not sure if that still needs to now be further calculated to get L/100km rather than L/Hr if i am getting the right values of course.
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