Trying to get stock gas mileage (MPG) calculator working (Z33)

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Lurch586
Posts: 8
Joined: Tue Feb 07, 2017 1:23 pm

Trying to get stock gas mileage (MPG) calculator working (Z33)

Postby Lurch586 » Tue Feb 07, 2017 2:06 pm

So Google searches on the net reveal nothing. I'm hoping to get some help solving a bit of a mystery. I'm not sure if this is a completely unsupported function on my Platinum Pro PnP for the Z33. I have one installed on my turbocharged Altima SE-R. So far, everything seems to work well enough, except for the MPG calculations that the car used to give me. These calculations show up as Average MPG and Distance Til Empty (DTE) on my Trip meter, as well as the silly instant MPG gauge on the 350Z-style triple cluster. With this new ECU, I apparently get 99.9 MPG average, my DTE is as high as 999 miles on a full tank, and the instant MPG gauge needle stays pegged on "gas-sipper" values (i.e. the car is either off or not moving)...

... except for when I decelerate my car to around 10 mph as I come to a stop. The needle then "blips" softly in the gauge to a little more than 35 mpg, then goes back to the "not moving/off" position. This is strange. If this feature is not present in the Haltech ECU, then what's sending the signal to the gauge that momentarily moves the needle every time I decelerate to a stop? The 10 mph point when this occurs also reminds me of my Idle Control on my current tune. It's currently set at a 7 mph Max Idle speed. So a working theory is that as I decelerate to 7 mph, the ECU switches to Idle Control and momentarily begins to send the requisite signal to the gauge (although incorrect). But if this is happening, why is there no apparent signal during moving operations?

Because MPG = mph / gallons per hour, I believe the stock ECU sends two signals to the car's instrument cluster for doing this calculation: the vehicle speed (mph) and the injector duty pulse width (usually in milliseconds). Either in the ECU or in the cluster, the injector duty pulse width is converted to gal/hr, because if you know your injector's fuel output per pulse-width, then it's a matter of multiplying the pulse width by a known constant.

More background: Before I installed the turbo and ECU, I had the engine rebuilt and ID1000 injectors installed. With the stock, UpRev-tuned ECU and new injectors, the gauge still worked, although I suspected the MPG values were off because I was seeing higher-than-normal MPG readings. I doubted that MUCH larger injectors, a tune and lower compression ratio pistons somehow got me better MPG.

So there you have it. I'd love to make these little functions work again. Thoughts?

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HaltechMatthew
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Re: Trying to get stock gas mileage (MPG) calculator working (Z33)

Postby HaltechMatthew » Tue Mar 28, 2017 4:32 pm

I cant remember back to the development of this ECU, and I dont know what an Altima is, but my guess is your vehicle maybe uses different CAN data for this.

cux350z
Posts: 25
Joined: Mon Mar 28, 2011 6:06 am

Re: Trying to get stock gas mileage (MPG) calculator working (Z33)

Postby cux350z » Sun Jun 11, 2017 9:06 am

Same thing on my Z33. 99.9mpg all the time.

Haltech may not be able to send this data to the white control box or the can network...it should be based off the IDC.


Was inflated when i had the harness piggy back edition due to larger injectors and the OEM ECU not knowing (oem ecu, white control box or whatever only saw the low IDC)

Lurch586
Posts: 8
Joined: Tue Feb 07, 2017 1:23 pm

Re: Trying to get stock gas mileage (MPG) calculator working (Z33)

Postby Lurch586 » Tue Jul 11, 2017 12:55 pm

cux350z wrote:Same thing on my Z33. 99.9mpg all the time.

Haltech may not be able to send this data to the white control box or the can network...it should be based off the IDC.


Was inflated when i had the harness piggy back edition due to larger injectors and the OEM ECU not knowing (oem ecu, white control box or whatever only saw the low IDC)


Sorry to hear you have the same issue. Not a big thing, just a small detail. What's the IDC?

For HaltechMatthew, the Altima is a 4 door sedan by Nissan for the US and Canadian markets. Like its cousin the Maxima, it's powered by the VQ35DE and is also PnP with the Z33 Platinum Pro. Integration has been nearly seamless so far. The loss of the fuel consumption data through stock meters is the only unforeseen loss of stock functionality I've seen, other than what you advertise (stock WB O2 sensors, etc).

So cux350Z just confirmed to me that z33s lose stock fuel consumption readings. This is what I wanted to know, and if there was possibly a workaround. I believe it's the ECU just not sending out the requisite signal.

cux350z
Posts: 25
Joined: Mon Mar 28, 2011 6:06 am

Re: Trying to get stock gas mileage (MPG) calculator working (Z33)

Postby cux350z » Thu Jul 13, 2017 11:31 am

Depends on where the calculation is done.

If a separate computer is monitoring the Injector Duty Cycle (IDC) and basing the MPG of the stock flow rate in CC/MIN vs the upgraded size, it is gonna be off by the ratio if FLOWoem/FLOWnew.

If it is not a separate output from the ecu and is the actual output to the inj/coil pack then the Haltech cannot scale it.

Lurch586
Posts: 8
Joined: Tue Feb 07, 2017 1:23 pm

Re: Trying to get stock gas mileage (MPG) calculator working (Z33)

Postby Lurch586 » Thu Jul 13, 2017 12:53 pm

The vehicle's combination meter (i.e. "dash cluster") has an onboard computer that recieves 2 signals and does the calculation: one non-CAN from the vehicle speed sensor and one CAN signal from the ECU. Guessing at this point that the Haltech doesn't send out that specific IDC or similar signal natively.


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