Diablo tunability

[Northshoremb]

I have a 2015 Hemi 8 speed with 3.92 gears and 34" tires. I get my best mpg at 80km/hr which avg 24mpg and hits 30 mpg on the flats no wind. BUT or speed here is 90km/hr so at 90-100km/hr my avg drops huge to 15mpg and 17-18mpg on flats.
What I'm wondering is can the tuner be programed to adjust the rim at certain speeds? Can I get it to run under 2000rpm at 90-100 instead of at 80?

 

[Ratket]

with a tuner no.. only way would be bigger tires.. or gear swap.. both would slow the truck down.

 

[regularcab2500]

Im pretty sure the only way to truly do that is to go with a numerically lower gearing. You may be one of the few that would actually benefit from taller gears.

 

[Csanders1992]

Im pretty sure the only way to truly do that is to go with a numerically lower gearing. You may be one of the few that would actually benefit from taller gears.

Bigger tires would do the same thing


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[regularcab2500]

The truck would also need to work harder to turn bigger tires. On paper it makes sense but just not realistic.

 

[Csanders1992]

Whether you do gears or tires it'll do the same exact thing. Tires play just as big of a role on your final drive ratio as your gear ratio does. Taller gears will make it work harder as well


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[regularcab2500]

Again that makes sense mathematically youre right. But think about it even if it reduces his effective gear ratio its still gonna hurt his mpgs simply because the tires are larger. He would need like a 41.5" tire to make up the same difference as going from 3.92 to 3.21 anyway.

 

[Northshoremb]

I have 34" Toyos now and don't wanna go bigger cause then again you are losing mpg. Not like these 34" extremes havnt lost me enough mpg now already

 

[Pickles]

RPM-->Wheel rotation is just a physical reality of your setup. No tuner can do anything about that - it's simply a mathematical calculation between the engine rpm, your trans and final gearing and tire size.

You want 30mpg on flats? Buy a Honda Accord.

 

[xrsman]

RPM-->Wheel rotation is just a physical reality of your setup. No tuner can do anything about that - it's simply a mathematical calculation between the engine rpm, your trans and final gearing and tire size.

You want 30mpg on flats? Buy a Honda Accord.

Or an ecodiesel

 

[xrsman]

OP my truck hemi 8 speed, 4x4, 3.92 gears with 5" lift, 35's, hemifever 91 octane tune, S&B CAI, and MBRP cat back gets high 11 to low 12 L/100 kms all day doing 90 km/h on cruise. My RPM usually sits at 1400-1500 doing 90. I'm not sure what it is doing 100, but I know it's less than 2000. I wonder why yours is acting so different?

 

[regularcab2500]

His must not be going into a higher gear like its stuck in 6th or something. Maybe a tuner would help give it extra umph to get into the highest gear instead of riding in the top of a lower gear. I obviously dont have an 8spd though so idk what gear it should be in and such.

 

[xrsman]

His must not be going into a higher gear like its stuck in 6th or something. Maybe a tuner would help give it extra umph to get into the highest gear instead of riding in the top of a lower gear. I obviously dont have an 8spd though so idk what gear it should be in and such.

Well without my tuner my truck will cruise in 8th gear no problem so it had the power. Maybe it is stuck in 6th or 7th though

 

[Northshoremb]

OP my truck hemi 8 speed, 4x4, 3.92 gears with 5" lift, 35's, hemifever 91 octane tune, S&B CAI, and MBRP cat back gets high 11 to low 12 L/100 kms all day doing 90 km/h on cruise. My RPM usually sits at 1400-1500 doing 90. I'm not sure what it is doing 100, but I know it's less than 2000. I wonder why yours is acting so different?

Ya with same motor, gears and you have even bigger tires and lift your getting 12ltr per 100km.....wow that's 19mpg. At 90 km I'm only getting 15-6 mpg. Like I said only time it kicks into MDS is around 80km. What's you avg in town milage stop and go. If I just drive normal no stomping it I'm 12 mpg in town

OP my truck hemi 8 speed, 4x4, 3.92 gears with 5" lift, 35's, hemifever 91 octane tune, S&B CAI, and MBRP cat back gets high 11 to low 12 L/100 kms all day doing 90 km/h on cruise. My RPM usually sits at 1400-1500 doing 90. I'm not sure what it is doing 100, but I know it's less than 2000. I wonder why yours is acting so different?

Ya with same motor, gears and you have even bigger tires and lift your getting 12ltr per 100km.....wow. at 90 km I'm only getting

 

[xrsman]

Ya with same motor, gears and you have even bigger tires and lift your getting 12ltr per 100km.....wow that's 19mpg. At 90 km I'm only getting 15-6 mpg. Like I said only time it kicks into MDS is around 80km. What's you avg in town milage stop and go. If I just drive normal no stomping it I'm 12 mpg in town

Ya with same motor, gears and you have even bigger tires and lift your getting 12ltr per 100km.....wow. at 90 km I'm only getting

My MDS will even kick in doing 90 if the road is nice and flat! Around town I usually around 13.5-15. I keep my foot out of it though! I do a lot of in town driving so usually my average isn't that good. Right now I'm at 12.6 because of in town driving. The last 2 highway trips have been 11.8 and 11.7, so in town is throwing me off! Lol