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?? Has sombody changed my rear end ??

THEFERMANATOR said:
The addition of a turbo is what is costing you the most on liage from the 6.2 to the 6.5.
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Well if thats the case I will pull the vac line off the WG. The vaccum pump was bad when I got it and the PO said it got 21 mpg. But he was figuring it with the speedo 5 mph fast. :skep:
 
Snot Rocket said:
I just ran my first full tank of fuel threw this truck. Not to happy with 16.5 mpg.
My 6.2 was 20 mpg almost every day. From what I have read that is about the norm for this truck. It just sucks that both trucks only go 450 miles on a full tank. Just this one takes 10 more gallons to fill it. Really makes me wish it still had the original rear end in it.
Time to read up on fuel saving mods I can do.
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Try 13-14 MPG.

That's my 98 K2500 ECLB with fresh everything (including GEP long block), 4L80E and 4:10 final....
 
I know my BURB with 4.10 gears and teh 6.5 stock got about 15 driving it at 68-70 on FLAT ground. After an exhaust, intake, #9 resistor, and an updated GM PROM it went up to 18. The biggest gain was noticed with the chip which dropped my cruising boost down from 2-2.5 to 1-1.5. The newer GM calibrations are MUCH better than the origanals as far as milage and driveability goes. The people with ATT see a big jump in milage as well as it is a much more open turbo at cruise since it is a non wastegated unit, and will typically only see a pound or so at cruise.
 
Is there a DIY sticky on the #9 resistor mod? I have been searching for one and can not find it. If there is one can somebody give me a link please? I dont like to be spoon fed information but I'm at my wits end trying to find this.
I would like to see what it is and what it does. If it would help my mpg I might try it.
 
Snot Rocket said:
Is there a DIY sticky on the #9 resistor mod? I have been searching for one and can not find it. If there is one can somebody give me a link please? I dont like to be spoon fed information but I'm at my wits end trying to find this.
I would like to see what it is and what it does. If it would help my mpg I might try it.
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Pull the connector off the pmd, two paper clips should fish it out. Might be in there too tight for paper clips as it "grips" two of the pins. Careful pulling it out if its tight, its just plain old phenolic style circuit board and somewhat fragile.

Installation is just push it in good and square.

IIRC, each value is a step of .3 mm3 fuel.

#5 to a # 9 is 4 steps and an extra 1.2 mm3 of fuel.

Hardly worth the trouble IMO.....


Sent from my iPhone using Tapatalk
 
Sounds easy enough just pull the #5 out and put in a #9. Seeing how my PMD is on a heat sink already should be a piece of cake. Just dont understand how adding more fuel would help my mpg. But if it dont I can always switch back.
Thanks for the how to on this. I figured sombody would have done a write up with pics and sticky it for us noobs. I guess I could do that.
I was serious about disconecting the waste gate vaccume line. I could put it on a switch in cab if I needed to pull something. But flat land cental IL. don't see much spool out of the GM-4 anyway. Would that give me a boost in the mpg?
 
Do not pull the vac hose off the wastegate, it'll smoke to high heaven & EGT's will run too hot. 2 ways to improve the mpg, slight increase maybe had with a custom tune, larger increase will come from keeping a brick placed under the the accelerator. Seriously keep the rpms under 2K for a tank & see what ya get. Checking mpg on a diesel requires many tanks to avg out the gallons per fill due to the foam along with confirmation from a GPS that yr speedo is correct.

HTH's
 
geez, that isnt good mpgs at all, and you even have a 2wd! manual transmission does do better, but not that much better.

I agree with crankme69, these turboed trucks hate RPM, I was able to get 18.5 mpgs out of my 8500 lb 1 ton dually once, but that was 58 mph at 1900.

The naturally aspirated trucks dont mind the RPMs nearly as much, I was turning about 2700 on a road trip in my 91 diesel, and it still cleared 20 mpgs. I fill all my stuff to overflowing, and shake it around to get all the air out, so I feel it is pretty accurate.
 
Well last tank I gave it a good dose of Lucas injector cleaner. I feel it did some good. This tank I started it on a diet of Howels. I hope to see some improvement as I'm also keeping her under the 2k mark. My daily drive is 40 miles round trip with only 20 of it highway.
I'm also looking into opening up the exaust system in hope it will help. If I delete the cat and muffler and go to a 4" straight pipe. Will I start getting boost creep?
 
A 4" exh will give 1-2 mpg improvement, it will also give you as much performance gain as any single other mod. I don't know what you mean by boost creep but I think boost will come on quicker as the exh flows more freely.
 
I'm sorry I thought that was a universal term. On my Mitsubishi if I have the boost controler set at 14 psi. If the exaust is open up to a more free flowing system. That same 14 psi setting would now be as high as 18 psi. Caused by the lack of back pressure in the exaust system. Do I not have to worry about that on this truck because the boost is controled by the ECU?

On a side note: Is there some reason we can't use the same waste gate control system on these trucks that Mitsubishi uses?
It is such a simple system that can be controled from the drivers seat. Can be set to open at 8 psi or set to launch your heads into orbit with just a turn of the knob. Just wondering?
 
the biggest improvement I have notice on over the shelf products is the silver bottle power service. I have a injector with an issue on the 91 diesel, as it pukes out a huge cloud of smoke on startup, but running the PS, it doesnt do it.
 
The boost will likely go up a bit due to the freer flowing exh.
Snot Rocket said:
I'm sorry I thought that was a universal term. On my Mitsubishi if I have the boost controler set at 14 psi. If the exaust is open up to a more free flowing system. That same 14 psi setting would now be as high as 18 psi. Caused by the lack of back pressure in the exaust system. Do I not have to worry about that on this truck because the boost is controled by the ECU?

On a side note: Is there some reason we can't use the same waste gate control system on these trucks that Mitsubishi uses?
It is such a simple system that can be controled from the drivers seat. Can be set to open at 8 psi or set to launch your heads into orbit with just a turn of the knob. Just wondering?
Click to expand...
 
not for the same reason tho. you'll get faster boost response because the turbo is working less. gassers have to have a bov diesels don't
 
ak diesel driver said:
not for the same reason tho. you'll get faster boost response because the turbo is working less. gassers have to have a bov diesels don't
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Ya and gassers have a butter fly valve and diesels don't. That is why they have to have BOV. But the BOV has nothing to do with spool time.
The more open exaust will make it spool faster. But can it cause it over boost the engine? (raise it to the danger level)
I know my gasser turbo system just trying to learn this system.

I guess I should have titled this thread "Learning something new!"
 
The answer is no. The boost on the 6.5TD with the electronic IP stock OEM is controlled by the ECU. It reads the barometric pressure (sensor on firewall) and along with the manifold pressure to manipulate the wastgate to control the correct boost pressure for elevation.
 
If there is an increase in boost due to a larger exh it will likely just cancel out to the resulting lower back pressure. I wouldn't worry about it. I don't think there will be any increase in cyl pressure
 
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