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oil pan 4 07-16-2011 07:37 PM

High MPG work truck
Back in 2006 I was looking for an old 2 wheel drive 6.2L diesel chevy blazer to be my home improvement and work truck, road trip, medium duty towing and mild off road machine. I knew $3/gal fuel prices were here to stay and I had to do with out certian things to get good fuel economy (like no 4wd, no huge tires, and slow to get up and go).
I had always heard diesel chevy blazers get very abnormally high fuel economy for a "SUV". Lengend had it the after market (banks engineering) turbocharged 5-speed versions were getting nearly 30mpg highway, but they are very rare.
Really who would sell a truck that gets up to 30mpg highway?
I looked high and low for a chevy diesel and setteled on a 6.2L diesel suburban with a TH700 (the fuel economy transmission). It turns out my truck also had 3.08 rear end gears too.
EDIT: the build sheet says it has 3.08 gears but the axle had been swapped for a 3.42 gear axle at some point before I bought it.
In stock form it got an impressive 15mpg city and 20mpg highway. Looking under the hood I knew there was lots of room for improvement.

First thing I did was change the air filter, motor oil and diff oil to synthetic. That didn't quite give me +1mpg but I started putting up 21mpg Highway for the first time.
I started off the real mods by tossing the very restrictive warm air intake and hand building a ram air intake set up. I could tell this was a choke point.
That netted gains every where, low end and high end power, fuel economy a clear +2mpg gain and increase in over all driveability. I also made it so the ram air could be pulled and almost instantly converted into a warm air intake for improved operation in the bitter cold.
Several month later changed tires, slightly taller. No change in MPG that I could see. I expected it to go down.
My second big mod was tossing the stock 5 blade 21 inch belt driven clutch fan and replacing it with "universial fit" electric fans.
The fan swap netted me nothing but gains also: Engine was quieter, smoother running, cranked over faster, warmed up sooner in cool weather and produced a 2.2mpg gain in combind city and highway driving.
At this point the big bad suburban was putting up solid 25mpg highway MPG numbers.It stayed in this configuration the longest.

Next big mod was I upgraded to 2.5 inch free flowing exhaust. Suprizingly no MPG improvement that I could clearly see. I didn't expect to see much anyway. Only gains to be had were with high end power and 100'F or so reduction in peak EGTs.
The final mod before the insanity started was I installed the more open and free flowing non-EGR factory "J-code" intake manifold.
Picked up 1MPG for $60 and a 45 minute install time. (I wish they were all so easy).
With the external engine mods done I was able to get 17mpg city and 26/27mpg highway.

oil pan 4 07-16-2011 08:06 PM

The insanity starts
The last part of 2009 I pulled the heads off the engine to get 2 stuck and non functioning glow plugs removed and port and polish the intake and exhaust ports.
That project quickly snowballed out of control.
As I tore the engine down more and more I found more and more problems. First it was broken glow plug tips jammed into the crown of 2 pistons. Then very bad cylinder bore taper then to top it off I found minor block cracks.
Fast forward 14 months later:
The heavily modified 6.2L/6.5T hybrid motor goes in.
I had a well known local diesel machine shop ballance the engine internals.
Picked up a "fluidampr" harmonic ballancer. (not cheap)
File fitted top, second and oil rings for each cylinder.
modified the oil ring spring to be "low tention" for less ring friction.
Ported and polished the heads
reseated the valves.
Polished the back side of the valves.
Machined the heads for valve seals (to consume less oil)
Bought a new updated 6.5L turbo block and got ahold of a like new, but used turbo crank.
Reused the 6.2L non-turbo heads on the 6.5L short block, that resulted in 22:1 compression ratio.
Went against every one on "dieselplace dot com" and converted the engine over to an electric water pump.
All the mods I did my self, unless noted. All the mods were done to improve fuel economy, power and allow less oil to be leaked or consumed.
I got it fired up and running good then 3 days later I had to go to afghanistan.
So I have no idea what kind of fuel milage the new engine gets. But, useing the same injector pump fuel settings as before the new high compression engine has a lot more power and made no smoke what so ever (that means all the fuel is getting burned now).
The truck has been sitting for months, untouched in that configuration.

oil pan 4 07-16-2011 08:25 PM

A rational person would have stopped there
Since I have been away I have started to hord parts for a turbocharger install.
The factory turbo system boosts power and doesn't do much for fuel economy, so I am going with mostly aftermarket parts.
I am going to combind the banks engineering turbo exhaust manifold with a modern Holset VGT out of a 2007+ cummins.
The VGT gives power and economy to diesels.
(remember banks engineering helped build those 30mpg SUVs so I hunted down some of there parts)
I am also going to run an intercooler where banks and the factory setup never did.
I am also building up to run water mist injection (yes it does boost fuel economy on diesels).
And have been considering a day time alternator delete with a twist. Where I Install solar panels on top of my truck to power the electrical system and build bracket with a pully that will allow the alternator V-belt to be quickly removed or installed and tentioned with out tools for night time or PTO use.
(not going to bother with an A/C clutch on an alternator type rig)

Has any one tried any mix of these mods on a diesel or gas engine to get better fuel economy?
Any one have any input on my alternator delete or water injection?

Tygen1 07-17-2011 10:20 PM

I believe you are breaking new ground here. It's neat to hear all that you have done. I've also heard about the 6.5's getting great economy.
The '07 Holset VGT is a pretty big turbo, both by size and it's air flow capacity.
What sort of power are you shooting for?

oil pan 4 07-18-2011 07:28 AM

Total horse power is a secondary consern.
Due to my high compression (even for a diesel) and depending on boost pressure temperatures I think I should limit my self to 15 to 18 psi.
It has to be less than 300 horses. 250Hp is proven to be real safe on these motors.
Over all comparing the HE351VE to a GM4 and GM8 the Holset was more efficienct where I wanted it, the surge line was further to the left due to the silencer ring and modern compressor design and provided more LB/min at lower pressure more efficiently (the right side of the map also looked better than GMx).
The GMx turbos use 60mm compressors, where the inlet to the holset is 60mm.
Also building my own simple 3 stage boost controler and 3 stage water mist controler "black box".
I will be tossing the electronic controler used on the holset and replacing it with a air/mechanical controler of my own design.
You are right about me breaking new ground.
Other people have installed intercoolers on factory or banks setups, a few people have installed water injection and even fewer (like 2 people) have attempted to run a HE351VE on a 6.5L (non intercooled).
No one has tried to put it all together. Let alone put it all on an engine with a lot of internal modifications.

Diesel_Dave 07-18-2011 09:58 AM

On the 6.7 Cummins, I've seen the HE351 put out 30 psi boost, so it might be a little oversized. It will probably get the job done, however. You might want to look at one of the wastegate turbos off the pre-2007 5.9 Cummins. With a compression ratio of 24, I would be careful with adding too much boost because of high cylinder pressures. If you really want to do it, you may have the beef up the head bolts, etc.

As a fellow diesel guy, I'd love to live next door to you! I'd love to have the shop/tools/money/time to do some of these types of engine mods.

oil pan 4 07-18-2011 10:31 AM

The Holset HE351VE is perfectly at home putting out over 30psi. I have the compressor map with hand writen notes on the front and back taped up in my wall locker.
I briefly looked at the H35 and HX40 serries.
The H35 seemed too small. The HX40 and HE351VE share the same compressor but the 351 has VGT and a smaller turbine than the 40.

The reason why compression is so high is because originially I didn't plan on running a turbo. But I think I can work around the higher compression with intercooling and water injection and I wont be running much boost.

trooper Tdiesel 07-20-2011 03:57 PM

i would start with 6 or 8 psi and see how your EGT temps are, and go from there.

you seem to know all ready but ill say it for others...
24/1 with a turbo is truly in a hazmat zone for faluer, if you don't know your EGT and boost presser, even then a long grade under load could take it out.

on the 6.2L they had pore cooling of the rear most pistons and the added stress of a turbo can take them over the braking point.
i love the electric water pump idea, BUT. if its pumping to fast or slow it could cook the engine do to lack of cooling. other than that its a grate idea.

your using a 6.5L block with 6.2L heads right? this should help the rear piston over heat/valve cracking/piston melting/ issue.:eek:

theres two gen of 6.2L if you did'ent know.
later heads have smaller valves to take the added stress, ford 7.3L 1993/94 and isuzus 2.2L 1986/87 did the same thing with there IDI diesels when they made them turbo d with the high compression.
before computerized DI injection came to on road use.

oil pan 4 07-20-2011 05:34 PM

I am fully planning on intercooling and running water injecion continously anytime under load (anything above 2 or 3 psi of boost). I could top out at 8-12lb of boost.
I have an EGT and will install a boost gauge. I am even going to go so far as to install a drive pressure gauge at least during testing.
Also I installed the 92+ cooling system minus the belt driven pump. I am also going to add another coolant bypass to get even more flow though the block.

Note from the future: The engine and HE351VE have no problems dealing with 14 to 15 psi.

slowmover 02-05-2012 06:21 PM

I'm one of a number looking forward to this truck coming together. Anything lately?

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