Poor gas mileage

[tylertrebilcock]

Can anyone offer a suggestion as to why my fuel mileage is so poor, I have played with several different tunes on my quadzilla and still can’t get over 14 on the highway. I’m running 35 in tires. I’ve heard it could be injection pump but it was replaced not to long ago and it’s been running great so it’s hard to believe that’s the problem. I’m also on stock injectors

[JAG1]

Do you have a fuel pressure gauge? If so, what are your pressures showing?

 

Put two stroke oil in that fuel before you damage that new VP. The ULSD does not meet Bosch specs for lubricity on the injection pump.

 

Make sure all intake boots aren't leaking and running a clean air filter, not a K&N filter..

 

Check the turbo for free spin turning by hand. No rubbing or rough spots or excess bearing play.

Edited July 4, 2018 by JAG1

[dripley]

All good advice above. I would have to ask what your gear ratio is? 35's and 3:55 gears will drag the mileage down. When mine was new on  the stock 265's just over 18 mpg was all I got unless I drove 55 or less every where. Is your mpg highway, in town or combined?

[Mopar1973Man]

1 hour ago, tylertrebilcock said:

I’m running 35 in tires.

 

Tires are too big. Plays a huge role in final ratio to the ground. With 35" inch tire your final gear ratio to the ground is 3.19 with 3.55 axle gears. This will make the truck struggle and create high engine load numbers. 

 

Engine load number is exactly how much fuel is being injected. The lower the engine load the better the MPG's. I typically cruise at 15% to 19% engine load.

 

Like myself I've dropped from 265's to 235's to gain a small bit. Now going to be switch 245's which this changes my final gear ratio to the ground 3.69 with 3.55 axle gears. 

 

More said here... I'm aiming for the mid 20's again and close to getting there. 

 

Edited July 4, 2018 by Mopar1973Man

[tylertrebilcock]

2 hours ago, JAG1 said:

Do you have a fuel pressure gauge? If so, what are your pressures showing?

 

Put two stroke oil in that fuel before you damage that new VP. The ULSD does not meet Bosch specs for lubricity on the injection pump.

 

Make sure all intake boots aren't leaking and running a clean air filter, not a K&N filter..

 

Check the turbo for free spin turning by hand. No rubbing or rough spots or excess bearing play.

Running s and b cleaned about 2,000 ago, I’ve been running 15 psi fuel pressure since pump was installed. Can anyone else second running two stroke oil?

1 hour ago, dripley said:

All good advice above. I would have to ask what your gear ratio is? 35's and 3:55 gears will drag the mileage down. When mine was new on  the stock 265's just over 18 mpg was all I got unless I drove 55 or less every where. Is your mpg highway, in town or combined?

Yes 3:55. No in town is like 11 lol. Combined I get like 13 because my daily commute doesn’t run on highway

1 hour ago, Mopar1973Man said:

 

Tires are too big. Plays a huge role in final ratio to the ground. With 35" inch tire your final gear ratio to the ground is 3.19 with 3.55 axle gears. This will make the truck struggle and create high engine load numbers. 

 

Engine load number is exactly how much fuel is being injected. The lower the engine load the better the MPG's. I typically cruise at 15% to 19% engine load.

 

Like myself I've dropped from 265's to 235's to gain a small bit. Now going to be switch 245's which this changes my final gear ratio to the ground 3.69 with 3.55 axle gears. 

 

More said here... I'm aiming for the mid 20's again and close to getting there. 

 

I’m looking to going to 33s in the future, 295, what would be a good gear ratio for the 35s or 33s?

Edited July 4, 2018 by tylertrebilcock

[Mopar1973Man]

11 minutes ago, tylertrebilcock said:

I’m looking to going to 33s in the future, 295, what would be a good gear ratio for the 35s or 33s?

 

For 3.55 axle gears optimal a 30-inch (3.69 final ratio to the ground) or 31-inch tire (3.55 final ratio to the ground)

 

Other than that plan on the high price of axle gearing... Now if you had 4.10 gears in the axle then your 35-inch tires would have a final ratio of 3.69 to the ground. I know a friend that just was down this road he wanted to keep his 37-inch tires so he had to swap to 4.10 gear in both front and rear axle at a price around $4,000 for do both axles. 

 

Looking "Cool" does cost money to do it properly. 

 

Basically, you want your final ratio between 3.55 and 3.73 to the ground for MPG.

[Ed ke6bnl]

I went to 35 in tires and the mileage dropped, I bought a crashed 99 Ram  with 4:10  gears and 80k motor and DTT transmission and exhaust brake Cheap used the 4:10 gears in  my 98.5 ram and it is a good combo but the extra tire size and weight doesn't back into the good mileage arena. I guess you give up a lot for the look. and now all set up for my 5th wheel so i will leave it alone. I do still have the engine and trans to sell in so. California. bought it when both my boy and I had the same truck and he now has a 3rd gen dodge ram

[tylertrebilcock]

35 minutes ago, Mopar1973Man said:

 

For 3.55 axle gears optimal a 30-inch (3.69 final ratio to the ground) or 31-inch tire (3.55 final ratio to the ground)

 

Other than that plan on the high price of axle gearing... Now if you had 4.10 gears in the axle then your 35-inch tires would have a final ratio of 3.69 to the ground. I know a friend that just was down this road he wanted to keep his 37-inch tires so he had to swap to 4.10 gear in both front and rear axle at a price around $4,000 for do both axles. 

 

Looking "Cool" does cost money to do it properly. 

 

Basically, you want your final ratio between 3.55 and 3.73 to the ground for MPG.

Yeah the bigger tires are because I do a lot of off-roading for hunting and such. I’m gonna look into re gearing. 

2 minutes ago, Ed ke6bnl said:

I went to 35 in tires and the mileage dropped, I bought a crashed 99 Ram  with 4:10  gears and 80k motor and DTT transmission and exhaust brake Cheap used the 4:10 gears in  my 98.5 ram and it is a good combo but the extra tire size and weight doesn't back into the good mileage arena. I guess you give up a lot for the look. and now all set up for my 5th wheel so i will leave it alone. I do still have the engine and trans to sell in so. California. bought it when both my boy and I had the same truck and he now has a 3rd gen dodge ram

How do you think 4:10s with 33s would do for mpg and highway cruising speed?

[Ed ke6bnl]

that maybe a good combination I run 33's on my offroad buggy I am sure they are not too much for the Dodge. I think that is a good compromise.  

[JAG1]

95% of the regular participants with 24 valve second gens in this forum run the two stroke in their fuel. Somewhere there is an article or download about laboratory tests done with American fuel. Results show It is to low of lubricity and too high of cylinder wall scoring. It does not even meet Bosch specs for the injection pump on the VP44. So one qt. of TCW3 per fill up with ea tank is good as the test results show. No diesel clean.... makes scoring values even higher.

 

This forum is a very good, has helped so much, it is very educational, a good place to have coffee with every morning.  and will save you this

Edited July 5, 2018 by JAG1

[Hawkez]

13 hours ago, tylertrebilcock said:

Can anyone else second running two stroke oil?

Yes, I run 1 oz per gallon with every fill up.  Today's diesel needs an additive to up the lubricity like Jag said, the 2 cycle oil is a very efficient way of doing that. 

 

HEre are some articles to consider.

 

[Mopar1973Man]

Basically what it comes down to is reducing rolling resistance, rotational loss, and drag. More you lean towards the 3.73 ratio the lower the drag is on the vehicle. Like my design in tire is to put my cruise speed near 2k on the tach. 

 

Then you look at fuel chemistry and lower cetane has more BTU's. This is why the winter fuel drops MPG numbers and summer fuel rises.

 

Then another secret colder the intake air the more it cranks up the timing. The ECM jump up about 3* more timing with IAT temps below 80*F. Hence where my MPG fooler design comes from it retards the timing back to summer values. Cold air is not MPG friendly. Optimally you want 100-140*F IAT temps for high MPG's. 

 

If you are running the Quadzilla you have to be aware of temperatures being the Quadzilla doesn't use either fuel temp or IAT temps at all. So you have to retard your timing map for hot days. Cold days you can advance it. 

 

Wind drag on our truck is pretty good. Lift kits and large tire place you higher in the wind and promote more wind drag and you have to drive slower to reduce that drag. Optimal in the past I found the best MPG in the 55 MPH realm. Just increasing to 65 MPH you've doubled your wind drag. 

 

If you looking for MPG you have to think about it like a race car. Reduce rotational mass and body weight on the truck. 

Edited July 5, 2018 by Mopar1973Man

[Mopar1973Man]

Back to tires... Go to a tire shop that sells racing slicks. Now get a 295's tire and a racing slick and check out the weight difference. 

 

http://hpwizard.com/rotational-inertia.html

 

All the NASCAR racers can't be wrong... 

[dripley]

1 hour ago, Mopar1973Man said:

Back to tires... Go to a tire shop that sells racing slicks. Now get a 295's tire and a racing slick and check out the weight difference. 

 

http://hpwizard.com/rotational-inertia.html

 

All the NASCAR racers can't be wrong... 

I can pick those tires up with my little finger. There's nothing to them. Then all the driver has to do is to figure out how to make them last 50 laps, then whoop into the pits and 14 or so seconds later there back on new rubber without even stopping by the cash register.

 My kind of tire store.

16 hours ago, tylertrebilcock said:

Can anyone else second running two stroke oil?

Yes. Try some and see for yourself. I started using  it 230k ago after installing the VP that is still in service.

Edited July 5, 2018 by dripley

[Mopar1973Man]

47 minutes ago, dripley said:

I can pick those tires up with my little finger. There's nothing to them.

 

This is the point of rotational mass. Guys that race knows you need to ditch parasitic losses down. Rotation weight is a key here. I know you can't run racing slicks on the highway but there are much better options that heavy M/T series 35" or 37" inch tire that is in the range of 120 pounds. I've done it years ago and weighed my 235's vs 265's and there was a 23-pound difference.

 

51 minutes ago, dripley said:

Yes. Try some and see for yourself. I started using  it 230k ago after installing the VP that is still in service.

 

I made it to 243k miles on my last VP44. I think ol' @dripley will beat my highmark soon. 

 

As for 2 cycle oil it's a dual bonus. 

1. 2 Cycle Oil is a natural cetane reducer or BTU increaser. As cetane goes down the BTU's rise. 
2. 2 Cycle Oil is a true lubricant where most diesel fuel additives if you pour a sample in a cup it will evaporate in a short time. Even though the product claim to be a lubricant.

[tylertrebilcock]

Sounds like I’ll be picking up some two stroke oil after work today. Thanks for the advice 

[dripley]

1 hour ago, Mopar1973Man said:

 

 

 

I made it to 243k miles on my last VP44. I think ol' @dripley will beat my highmark soon. 

 

 

I am trying real hard to do that.

[Dieselfuture]

41 minutes ago, tylertrebilcock said:

Sounds like I’ll be picking up some two stroke oil after work today. Thanks for the advice 

Make sure it's ashless,  most run supertec 

https://www.walmart.com/ip/Super-Tech-TC-W3-Outboard-2-Cycle-Oil-1-Gallon/16795065

Edited July 5, 2018 by Dieselfuture

[RottenMutt]

what are your exhaust temps at 65 mph cruse?  i'm thinking late injection timing?

[Evan]

My truck got horrible mileage with 31s and 33s. Power was also falling off. I finally got injectors 7x.009 sac.

 

Factory injectors were so horribly plugged you could see where the fuel was spraying through carbon tracks.

 

Truck power I swear doubled and injectors more than paid for themselves in fuel savings.

 

She now wears 34s has about 2k in bed and still gets good mpg numbers. 

 

I dont run it over 1800rpm when empty. I can go to Grant's pass Oregon drive a few Miles here and there then fuel up to come home. That's going a few miles on a tank .

Stock injectors were no where near making Grant's past on tank