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New project 99 2500hd suburban 6.5TD

S

sd455

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white rock B.C
View attachment HPIM1580.pdfView attachment HPIM1580.pdfhttp://www.thetruckstop.us/forum/images/attach/pdf.gif

Just recently pick up this 99 Burb, for what I think is a steal. The 2nd owner was not prepared to invest the money to chase down an intermittent stalling problem and moved on to a new truck. after a few months of no takers I made an offer and he accepted. The truck is an LT and is full load including leather. I'm intertested in finding an OEM front split bench in pwer/leather to replace the captains chairs. Is there any such thing?

So far I have changes all fluids, replaced the Lift pump with an OEM delco, replaced oil,air,fuel filters,removed the muffler and soot trap and replace with 3" pipe all the way back. replaced a few nuisance items and getting ready for a major clean.

I also removed the running boards, silly looking mudflaps and bug deflector and added a front air dam.

I have a new PMD/Heat sink and a new set of shocks waiting to be installed. I also just picked up a set of OEM H2 wheels and am currently in the process of choosing tires...settled in on the idea of a 285/70/17. Hoping to drop HWY rpm a bit as the truck has 4.10's

Currently getting about 15.2 MPG with mostly hwy driving, and hoping to increase that to 19- 20mpg.....Is this realistic?And if so what path should I take to achieve this? I read some mileage threads that seem to mostly have generic ideas...looking for maintenance/tuning suggestions

I'm considering a heath PCM/turbomaster in my quest for better power, and will be adding guages before hand.

I have been lurking here for a bit and found alot of great information, so thanks in advance to everyone here for the future inputs.

Cheers!
 
19 to 20 mpg is unrealistic, especially with 4.10s. The best I've seen was brushing 18 mpg pure highway and that is in the '95. 17 mpg seen more often on highway.

Get the Diamond Eye 4" turbo back exhaust and get a new mandrel bent crossover for starters.
 
ak diesel driver said:
if mileage is all your after stick with the vac system and get a reflash that work's well with it
Click to expand...

I was curious about that. I spoke with Bill Heath, and he scoffed at the idea that the turbomaster inhibited mileage. I am after more power , but not at the cost of mileage......its a turbo diesel, so IMO I should be able to have both. There seems to be a few different opinions about Turbomaster/Vacuum set up-What gives?
 
Big T said:
19 to 20 mpg is unrealistic, especially with 4.10s. The best I've seen was brushing 18 mpg pure highway and that is in the '95. 17 mpg seen more often on highway.

Get the Diamond Eye 4" turbo back exhaust and get a new mandrel bent crossover for starters.
Click to expand...

I just did a 3" system, and not so sure that the 4" will build much more power considering the 3" downpipe. I have a flowmaster crossover and mandrel downpipe on order for now
 
That looks really good, not so old either. You should check the fan clutch to see if it a spin on type or bolt on to the water pump. If you have the spin on type then you also have the latest high output water pump which showed best flow balance between heads. That with the later 9-blade fan is a good setup that wouldnt need to be touched.

On an NA engine going huge on the exhaust doesnt always do much, but with turbo science, pressure differentials is what its all about. Straight pipe itself creates a backpressure with length, add turns and its more. So changing to 4" all the way back does help, its not a wasted effort even from 3" straight pipe. The weakest link in a chain doesnt apply to fluid dynamics, which is why even though the downpipe is 3" that the rest of the system being bigger helps.

I would recommend an Amsoil nanofiber filter, get in touch with Ashton (Wrecker) for a good deal. You can also get cetane boost from him.

Make sure your coolant is sitting close to 200F, 195F ACDelco T-stats for best economy.

Is this a 2wd or 4wd? The taller wheels will lower cruising rpms, what size tires do you have now? You can get reasonably priced 255/75/17 tires that would be less than 1/2" ride height shorter than the wider 285/70. 255 would leave more turning clearance in the front wheels and have less rolling resistance. Youll also likely need to modify your VSSB module to correct the speedometer for taller tires.

If the vacuum setup is functioning I would leave it there, I preferred it when I had a GM turbo. If it fails in the future then you could consider throwing on a manual controller. You could save some money on the PCM reflash from Kojo, through WalkingJ Designs. You can talk to Kojo to tell him the goals of the programming, to get mileage.

If you got flat land cruising you might get to 19mpg, depends on the speed/rpm youre going.
 
the older n/a 6.5s and 6.2 got better mileage than the turboed ones. It takes fuel to make boost if you had a chip set up to give little or no boost at light loads and then came on heavy with lots of throttle that would be the best setup
 
ak diesel driver said:
turbo is also an exhaust restriction when not needed
Click to expand...

Very true, even just having the exhaust go up into the turbo and out the small wastegate is a restriction. Which is why using some of that waste heat to build a small amount of boost can be beneficial. Sitting at 2-3psi of boost at whatever speed you normally cruise at is good. Unless you put in a wastegate from the crossover to the exhaust which would allow much less exhaust restriction through the turbo. The GM turbo is pretty close to 1:1 efficiency at real low boost, but drops off in efficiency pretty quick after that.
 
buddy said:
That looks really good, not so old either. You should check the fan clutch to see if it a spin on type or bolt on to the water pump. If you have the spin on type then you also have the latest high output water pump which showed best flow balance between heads. That with the later 9-blade fan is a good setup that wouldnt need to be touched.

On an NA engine going huge on the exhaust doesnt always do much, but with turbo science, pressure differentials is what its all about. Straight pipe itself creates a backpressure with length, add turns and its more. So changing to 4" all the way back does help, its not a wasted effort even from 3" straight pipe. The weakest link in a chain doesnt apply to fluid dynamics, which is why even though the downpipe is 3" that the rest of the system being bigger helps. I always thought that exhaust temp dictated the need for a larger exhaust, and that as the exhaust travelled through the system and cooled less space was required to allow flow. That said, I have always worked with gassers and what I'm seeing with Diesels is the exact opposite. In my mind the ideal would have been 4-5" downpipe into a 3-4" system.


I would recommend an Amsoil nanofiber filter, get in touch with Ashton (Wrecker) for a good deal. You can also get cetane boost from him.

Make sure your coolant is sitting close to 200F, 195F ACDelco T-stats for best economy.

Is this a 2wd or 4wd? The taller wheels will lower cruising rpms, what size tires do you have now? You can get reasonably priced 255/75/17 tires that would be less than 1/2" ride height shorter than the wider 285/70. 255 would leave more turning clearance in the front wheels and have less rolling resistance. Youll also likely need to modify your VSSB module to correct the speedometer for taller tires.
Thats great advise on the tires, I just never thought that I could get that size. I was originally going to go with a 235/85/16, until I found the H2 wheels.The truck is 4wd, can you explain the VSSB correction?

If the vacuum setup is functioning I would leave it there, I preferred it when I had a GM turbo. If it fails in the future then you could consider throwing on a manual controller. You could save some money on the PCM reflash from Kojo, through WalkingJ Designs. You can talk to Kojo to tell him the goals of the programming, to get mileage.

If you got flat land cruising you might get to 19mpg, depends on the speed/rpm youre going.
Click to expand...

I will be trying for 20, on flat ground at 65 mph,with no load.


 
buddy said:
That looks really good, not so old either. You should check the fan clutch to see if it a spin on type or bolt on to the water pump. If you have the spin on type then you also have the latest high output water pump which showed best flow balance between heads. That with the later 9-blade fan is a good setup that wouldnt need to be touched.

On an NA engine going huge on the exhaust doesnt always do much, but with turbo science, pressure differentials is what its all about. Straight pipe itself creates a backpressure with length, add turns and its more. So changing to 4" all the way back does help, its not a wasted effort even from 3" straight pipe. The weakest link in a chain doesnt apply to fluid dynamics, which is why even though the downpipe is 3" that the rest of the system being bigger helps.

I would recommend an Amsoil nanofiber filter, get in touch with Ashton (Wrecker) for a good deal. You can also get cetane boost from him.

Make sure your coolant is sitting close to 200F, 195F ACDelco T-stats for best economy.

Is this a 2wd or 4wd? The taller wheels will lower cruising rpms, what size tires do you have now? You can get reasonably priced 255/75/17 tires that would be less than 1/2" ride height shorter than the wider 285/70. 255 would leave more turning clearance in the front wheels and have less rolling resistance. Youll also likely need to modify your VSSB module to correct the speedometer for taller tires.

If the vacuum setup is functioning I would leave it there, I preferred it when I had a GM turbo. If it fails in the future then you could consider throwing on a manual controller. You could save some money on the PCM reflash from Kojo, through WalkingJ Designs. You can talk to Kojo to tell him the goals of the programming, to get mileage.

If you got flat land cruising you might get to 19mpg, depends on the speed/rpm youre going.
Click to expand...

Havent figured out how do brak down the quotes properly....duh,sorry,

Anyways, On the exhaust I always thought the larger pipe requirement would be at the front of the system where the gasses are hot and require extra airspace to flow, and as the gasses cool the requirement would diminish....hence my feeling that if anything, the place for the 4 or 5" pipe would be the downpipe. That said this is my first attempt at tuning a diesel,and a turbo.

I like your idea on the tires and will investigate before purchasing, I also prefer that slimmer look as well on a mostly street driven truck, plus the less wight the less inertia to overcome.Can you explain the VSSB module adjustment process?

I will look into the fan and report back.
 
Nice looking Burb, since it's a 99 it should have the better cooling.

Post up your VIN number and we can breakdown the RPOs on it and see what other goodies it has, such as a rear locker or high capacity airbox.
 
88gmctruck said:
Nice looking Burb, since it's a 99 it should have the better cooling.

Post up your VIN number and we can breakdown the RPOs on it and see what other goodies it has, such as a rear locker or high capacity airbox.
Click to expand...

I have the original window sticker...It was folded up in the owners manual.

It show locking diff but doesnt say anything about the airbox.
 
All the RPOs will be in the glove box on a sticker. The better cooling started during 99 model production, so if yours was built in 98 or first couple months of 99 it might have the older style water pump. Build date is on the door jamb sticker, upper corner normally.

For the exhaust, with fluid dynamics it doesnmt matter where the restriction or backpressure is generated, its all cumulative, so even though a 4" downpipe would be nice, the real backpressure is from the 20 feet of pipe behind it.
 
sd455 said:
I spoke with Bill Heath, and he scoffed at the idea that the turbomaster inhibited mileage. I am after more power , but not at the cost of mileage......its a turbo diesel, so IMO I should be able to have both. There seems to be a few different opinions about Turbomaster/Vacuum set up-What gives?
Click to expand...

In laymans terms (which is typically the extent of my ability!), the TM won't hurt... but the Vac system is better (not by a lot, but still better). The Vac system will adjust for things like atmospheric conditions and altitude, thereby giving a more precise control of fuel usage.

Maybe someone else can give a better explanation.
 
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