On The Port & Polish Job. On My Semi Trucks It Only Seemed To Make A Difference At Peak Output Of The Engine Power . I,ll Go With The Cpl 1550 And Keep It All Stock . Another Friend Of Mine Said The Same Thing On The Cpl And Claimed Over 20 Mpg If He Kept His Dodge 1 Ton Under 70 Mph, He Has 4.10 Gears And A Nv 4500 . I,ll Have A 1 Ton Dually With 3.31 Gears And A Nv5600 Or A618 Dodge Auto. Havent Made My Mind Up Yet On The Trans. I Want To Cruse At About 1600 - 1800 Rpm,s At 65-70 Mph .
The '94-'95 auto was rated at 160hp(I think CPL 1550 but could be wrong- I'll check my '95 if I remember). The '94-95 5 speed trucks were rated at 175hp.(I'll try to check the cpl # of the '94 chassis cab if I remember as well). My '95 auto(4.10 gears) gets aroun 17 mpg around locally- I might could pull more out of it if I stay off the throttle and back off the star wheel. I don't know what it will do on the highway as I've never taken it on the interstate. It runs 2k rpm at 67mph. My '96 180hp truck, 3.54 gears(that runs like a dog compared to the other CTD's we have) gets 18-19 on the interstate. It runs 74mph at 2k RPM. Both trucks are 4wd, 285/75/16 tires. I suspect it will be a little better with pizza cutter tires and 2wd.
My moms truck is an interesting one. Its a '98 quad cab, auto, 3.54 gears and 2wd. I'm sure she gets over 20 mpg, maybe 22+, but I can't recall the numbers since I last drove it long distance. With the stock 245/75/16 tires it runs similar rpms to my '95- maybe 2k rpms at 67 mph. I have to note the speedometers on these dodges are often off from the factory I think. My '96 had 265 tires on it when I bought it- and it was off compared to the speed detection signs law enforcement uses on the interstates. Now with the 285's it is dead on.
I don't the CPL is the only thing you need to look at- sure its a starting point- but look more at what the engine is outfitted with- and timed at. There are some small timing differences and I think that has an effect on mileage. I suppose the higher you go on timing, the better the mileage may be(to an extent). But there is a point at which you can have head gasket problems according to the BOMBers on the TDR. I've heard reports, mostly from the Jeff Garmon racing guys that his race trucks with huge hp numbers are reaching 25-30 mpg on the highway when not really getting on the fuel. They have timing set well into the 20's. This is all conjecture I suppose since I don't have firsthand experience in this area. I personally wouldn't set a DD high fuel mileage truck that high since I bet it affects low rpm performance, idling, and starting... driveability?
I guess the point is the CPL may be a good starting point- but there are probably ways to tune in almost any on road CPL for efficiency(and still have available power).
Thanks Guys All I Know For Sure Is I,ll Be Running 3.31 Gears In The Rear End, 19.5 Rims With Commercial Radial Tires , Drw , And Its Looking Like I,am Going Nv5600 Trans. I Have A 1993 Dodge Overdrive Auto Trans But I,am Afraid It Wont Hold Up In My 1 Ton Pulling A Heavy Trailer With Truck Loaded Also. I Sure Hope I Can HiT 20 Mpg With A Cruse Speed Of 65-70 Mph. Recon I,ll See. I Want To Cruse At About 1600-1800 Rpm,s. I,am Leanning Towards A 215 Hp Stock Setup. I Have Both Fuel Pumps So I Can Go With The Best Setup Out There.
Bob, the Cummins I bought was getting a verified 22-24mpg at 65mph, loaded, with 3.55's and the 47re. I am not very confident in that trans either, but it has had some valve body work and regular service, so we'll see. Power was dynoe'd at Blue Chip Diesel at 210hp/610ft.lbs. It has a smaller turbo housing on it, and a VE pump. Nothing special.
I'll get you the CPL in when I get back to UT if you still need it.