WH Hemi Fuel Economy Issue?

[TyronR]

Hi,
I do want to mention didn't buy a V8 for the fuel economy, but for the noise, fun factor and simplicity. But I am getting around 27-32L/100 around town now and it has been consistant for about 6 months now. I only use 98 fuel so it is a bit expensive. I don't think I have a lead foot as generally it changes up gears between 2000 and 3000rpm, but I do blow the cobwebs out id have to guess 4 times a week.

When I originally bought the car maybe 2-3 years ago, I was getting around 15-16L/100km around town when it was stock and on 29" tyres. With the mods I have done, I'd expect around 20-21L/100km and wouldn't be asking the question if it was around there but I am just concerned I could have a problem.

The car is an '07 WH 5.7L with around 130,000km. The mods I have done which I know would affect the economy are a 2" lift, bullbar, and 32.6" tyres. Other than that, just deleted the centre muffler and intake silencer (for both visibility down the front of the engine on the tracks if I need to check and induction noise) - moved the intake air temp sensor into side of airbox, if that is important to note.

I can live with it, but if I can get an extra 30% range out of a tank then I'd definitely like to chase that up. The factory spark plugs could be due for a change as I think I read around 140,000km somewhere. Cheers, hoping for a bit of input

[brad.jones]

Basically same car, same year, similar milage, similar mods. I get 20L/100kms around town. On the highway on a big trip, fully loaded with swag on the roof I can get it down to almost 14L/100kms if I really baby it and keep the MDS activated.

I have reprogrammed the tire size in the ECU so the odometer and fuel calcs are more accurate. I actually found this seemed to make a difference to how the transmission shifted too.

Have you actually calculated the fuel consumption manually by using the actual distance traveled from say your GPS / Google maps? You might surprise your self like I did. The consumption might not be as bad as you think.

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[TyronR]

Originally Posted by brad.jones

Basically same car, same year, similar milage, similar mods. I get 20L/100kms around town. On the highway on a big trip, fully loaded with swag on the roof I can get it down to almost 14L/100kms if I really baby it and keep the MDS activated.

I have reprogrammed the tire size in the ECU so the odometer and fuel calcs are more accurate. I actually found this seemed to make a difference to how the transmission shifted too.

Have you actually calculated the fuel consumption manually by using the actual distance traveled from say your GPS / Google maps? You might surprise your self like I did. The consumption might not be as bad as you think.

Sent from my Pixel 3 using Tapatalk

I haven't done a calculation like that. I might need to invest in a tuner but its hard to find one that works in AU. What tuner did you use?

[brad.jones]

I just used http://jscan.net/ with https://www.jaycar.com.au/obd-ii-eng...ology/p/PP2145

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[slippery]

as said above....with your tyre size going up somewhere near 10 percent, the speedo is also out by the same amount....you need the speedo recalibrated and youll drop 2L/100 instantly.

[slippery]

as for the other 10L/100 youve lost yikes!, start doing the usual like pcv clean, intake clean, new plugs, throttle body clean etc etc

[Classic Boy]

Put in new O2 sensors preferably mopar genuine ones are worthwhile and will pay for themselves in few months of driving.
My ex daughter’s 2003 I6 WG improved from 14.6L/100kms to 11.6 with a new front O2 sensor general driving but mainly on the highway.
I tried an aftermarket brand and there was an improvement but when I swapped in a genuine mopar sensor the biggest gains happened.
O2 sensors can be significantly degraded without any codes.