When is the best MPG achieved? Should the EGT and boost both be as low as possible?

I pretty sure on the EGT part because the higher the EGT the more raw fuel that is not being burned, right?

But what about the boost? If the EGT's are relatively low and the boost is 0-5psi, does that make for better mileage than low EGT's and a hight boost?

Maybe I'm running around in circles here. I'm just looking for some ideas as to what to look for in the gauges to get the best fuel mileage.

Don't have a boost gauge so I am not sure what kind of boost I am running, but my best mileage has been below 2k and on the freeway. Keeping it around 70 and I get 19-20. At these speeds my pyro is right at 600. I think the real killer of mileage is high rpms, she likes to drink above 2k. See ya

Your best mileage comes from the min rpm your engine is not lugging in. CRUISE IS THE DEVIL AND KILLS YOUR MPG!

CRUISE CONTROL WAS INVENTED BY SUADI ARABIA, IT IS THE DEVIL!

Rip that damn cruise control out your truck and flip the bird to the the Saudis

If i was President i would outlaw all cruise controls, they just put money in OPEC's pocket!

Your best mileage comes from the min rpm your engine is not lugging in. CRUISE IS THE DEVIL AND KILLS YOUR MPG!

CRUISE CONTROL WAS INVENTED BY SUADI ARABIA, IT IS THE DEVIL!

Rip that damn cruise control out your truck and flip the bird to the the Saudis

If i was President i would outlaw all cruise controls, they just put money in OPEC's pocket!

So I guess it's safe to say.....you don't like cruise control.LOL I think I've read that in a couple of posts somewhere.

That is an understatment LOL

Not sure about the exact numbers for cummins engines, but I'll tell you what works for International engines. The numbers should be similar.

Don't worry about boost.

Keep RPM below 2000.
Keep EGT (pre-turbo) below 600 degrees.
If you can control RPM at all, shift about 1300 RPM.
Air the tires up as hard as possible without crowning the tread.
if you can live with one, a tonneau cover helps a lot.

i can 22mpg if i behave with it but usually 17-18 it hard to go 65 when you can go 85:Thumbup: , jr

My buddy gets 26 in his 01 2500 4x4 short box,I'll have to ask him what hes got done to it.I once got 1100 kms out of a tank on the highway in my 97 12v auto long box ext 4x4.Thats with nothing but a bhaf and a well maintained truck,but I never broke 2000rpm.On the other side of things recently I burned over 200 litres in 1250 kms going 90 miles an hour,so yes the rpm has alot to do with it

Boost should have a lot to do with it. If you are running boost at all that means you need less fuel to get the same power. But that means no smoke so its not as fun....:Thumbup:

In my expirience generally speaking the cummins and most diesel trucks for that matter achieve better milage the lower the RPM down to about 1500 RPM, or just high enough RPM to keep the engine from lugging.

Now this I could be totally wrong on but I would think the less boost one produces the better the fuel milage. Because the more fuel we give are engines the more boost we make, so if we give it less fuel and see less boost then we should see better fuel milage. At the same time the higher the EGT the more completely we are burning the fuel we give the engine so that would mean it is working more efficantly. That being said in theory the higher the EGT with the least amount of boost should net the best fuel milage. :blah: Does any of that make sense :shrug: Sounds good in theory anyway

The biggest bennefit I have ever seen to affect my milage is engine speed. One example is most of the time with my lead foot I usually get about 16mpg driving 50/50 intown and highway with 4.10 gears. But last summer I was working out of town and had to commute about 130 miles a day to work. I had a choice of 2 route's to get there one was interstate 75mph the other was back highway 55mph. Since I have 4.10 gears I chose the later of the two. So for two weeks I drove this back route and set my cruise at 60mph most of the way. and for the first week my milage jumped to 19.8mpg and the second week it was 19.6. that was running about 1950 RPM instead of my usual 1800 to 2200 RPM.

Dang that was a long post :blah: :blah: :blah:

:HappyMugs ...Josh

Like they have told you,rpm and load. With my 24 V CTD,i found that if i keep it under 2000RPM cruising,it makes a huge difference.I have 4.10 gears,so 2000RPM is only 64 mph on the speedo,I have larger tires,so its off by 3-4 mph.SO 2000RPM is 67-68MPH,if i can keep it there I can get 17mph highway easily,but i seldom do,andRPMs end up at 2200-2300,and mileage drops to 15 hiway.

IMO, EGT is the best indicator of fuel mileage at part throttle cruising. In the 70's we were working on ways to increase fuel mileage on the first Cummins NTA motors.

I had an old mechanic tell me that to get mileage/efficiency you need to consume the energy produced by the fuel in the cylinder and not on the way out heating exhaust components. A motor blowing flame out the exhaust stack is just wasting energy that otherwise could have been used to press the piston. From what I've experienced he was right on.

Turbos are just a drain on Volumetric Efficiency (and fuel mileage) UNTIL they receive enough velocity to start making boost. Sizing is everything with turbos. Generally a bigger exhaust housing is better if you are after part throttle mileage. That's not going to make the feds happy though causing turbo lag and temporary smoke until they spool up.

Most of the newer factory housings are small enough that waste gating at higher flow rates is necessary just to keep necessary Volumetric Efficiency. That's why part throttle fuel mileage is less on most of the newer high back pressure systems.

All of our best fuel mileage diesels at low power (light throttle) conditions were naturally aspirated. But that can turn around real quick if you want more power at higher fuel rates.

--Paul

i got a 12 v and im getting 23-24 city and 20-22 high way with 4.10 gears

My 06 is getting 19-20, w/ 13k on it. my dads 98 12 valve gets 20-22 wish i got that with mine.