Engine/Transmission (1994 - 1998) Just bought 98 12v now what?

[TBartlett1]

Hey guys, I'm the proud new owner a 98 12v qc long bed. The PO installed bosch 300's, 4 inch turbo back exhaust and intake. Its currently in the middle of a transmission rebuild using goerend's triple disk converter, billet input, billet flexplate, more clutches and some other goodies... my question here is for the sake of mileage, would it be worth the money to buy ddp 75hp injectors and a fuel plate? I'll be driving 700 miles round trip to pennsylvania once a month and would like to make the beast breath most efficiently.



For those of you with the 50 or 90 hp injectors from ddp, did you notice any change in mileage like they advertise?



And what kind of fuel plate do you suggest?

 

[snappy]

The first bomb I'd do would be an air intake. From your post, the truck still is stock there. Then I would check the mileage. A 10 plate would be the next bomb as well as a governor spring kit. If mileage is the first goal, I'd install factory 215 injectors or DDP2. Timing is also a big influence on fuel mileage. The right foot also has a powerful influence on mpg. Congrats on the new truck.

 

[hsmith]

Mine would do better if like Snappy said the right foot wasn't so heavy. Still have no problem getting 17 around town. Seldom do I make any trips without towing the tt, which still is 12+. Leaving Wednesday on a 500 mile run empty. I'll see what it does then.

 

[TBartlett1]

Thanks guys. The truck came with a k&n intake, which by the way i'd like to change to a better air filter preferably one that will filter down to atleast gravel size. Hsmith, let me know how you did on your trip.

 

[DValentine]

I like the DDP2 injectors. I get 17 to 18 running 75mph. I have a stock plate. Timing is advanced to 17 degrees. It does OK towing a large 5er.

 

[HerbW]

I just drove my truck on an over 300 mile round trip from Sandy, Oregon to Sunriver, Oregon and back plus a little bit in between. I got 22. 07 MPG! Best ever for me. I topped it off both times for real mileage figures. I have a 12 valver, 354s, a number 8 plate and my new billet converter stalls at 1600 RPM. I think it's got something to do with lower RPMS from the converter boosting the mileage. Love it! I did have to watch the pyro temps going over Mt. Hood in OD though. Now to change out my oil sender again. To bad I can't find a local dealer to do the TSB 08-22-09. The 98 12 valver is a hard one to find. Enjoy!

 

[Joseph Donnelly]

First of all, get a three piece exhaust manifold and "contain" the Killer Dowel Pin. Then get injectors around the 215 HP size for combined power and mileage and bump the timing up to about 15 or 15. 5 degrees.

 

[HerbW]

Joe, Are 215 hp stock injectors what you mean? I also need a new three piece manifold. I can see my manifold has shrunk at 108k miles and in time something is going to give. Any recommendations for brands at the cheapest price? Thanks, Herb

 

[TBartlett1]

Congrats Hsmith on your mileage achievement! The bosch 300's in mine are giving me approx. 65 or so hp, right? If I got a hold of a 3rd gen stock turbo say, from a 325hp 610# engine would I see any benefit running that in conjunction with the setup I have right now?



I've decided on the #8 plate so since I'm already there should I just buy the 3 or 4k governor spring? (I know the 4k requires valve springs) what would be the suggested route?

 

[TBartlett1]

I meant HerbW. When I went to reply I was just going off memory, I didnt scroll down and actually look at the posts... :-laf

 

[Vaughn MacKenzie]

TBartlett1 the gov springs partially depend on how they're installed but with the 3K set in my '98 it pulls strong to 3700-3800 and has no trouble pegging the tach.

 

[Cummins12V98]

I went from a set of Piers rebuilt 215 injectors with at least 100k on them to DDP stage two injectors and was told they would get as good or better mileage but that is not the case. I have lost 1/2 to 1 mpg and I would say the power is not that much improved and they are smokier than the 215's. Thinking about going back to the 215's and selling the DDP's.

Ron

 

[Midnite]

What gears does your new 12 valve truck have? If you have 4. 10s you could benefit from taller than stock tires, and maybe even slightly more timing advance depending on your rpms at cruise speed. If you've got 3. 54s then you'd still probably benefit from taller tires. I get almost a 10% mileage improvement (admittedly on a 24 valve) by going from 235-85R16s to 255-85R16s (31" vs. 33").

 

[TBartlett1]

I believe I have the 3. 54 ratio.

I called TST Thursday to order the fuel plate and spring kit and was talked into getting the #5 plate. The temptation of 270hp 650# was too great. Note: tbartlett1 has just started down the slippery slope.

 

[TBartlett1]

I believe I have the 3. 54 ratio.



I called TST Thursday to order the fuel plate and spring kit and was talked into getting the #5 plate. The temptation of 270hp 650# was too great. Note: tbartlett1 has just started down the slippery slope.