GMs new 6.2 di seems to get great mpg

The new GM trucks are 600 lbs. lighter thanks to greater use of aluminum. Fuel is sent to fewer cylinders when the load is light on the engine. The trucks have 8-speed transmission with more overdrive gears and smaller gaps with the lower underdrive gears.

What surprises me is how infrequently the manufacturers of trucks and SUV's go for improving fuel economy. For the past 20 years the horsepower and 0-60 times have been the selling points to buyers. The people who cared about MPG bought a 45 MPG Prius or a 30 MPH Subaru Forester. I took a middle approach and have a 45 MPG Prius and a 15 MPG diesel truck. Guess which one I drive 80% of the time.

Direct injection of gasoline was invented here, but no takers from
'our' OEMs...the Japanese (Isuzu) licensed it first and had a truck
V6 in the late 90's. Early 2000's had Toyota offer it here, but the
injectors were not capable, yet. So supplemented by port inject at
the higher throttle settings.

Over time in a very competitive market...they will all have very similar offerings

Power, MPG, comfort, ratings, etc



They will all have a host of problems during their teething periods. Some more
than others and will reap the benefits (loyalty, market share, awe factor, etc)

That also depends on how management plays marketing...GM had direction injection
gasoline ICE's years before Ford, but upper management decided such a wonderful and
powerful thing...that they dictated only for their lux badge...Caddy. Ford
beat them to the truck market and the ECOBOOST reins top dog for now

This GM V8 6.2L's spec sheet looks just like Ford's V6 EcoBoost...but GM decided to
keep the displacement to a larger V8 and get the MPG with cylinder deactivation.
Ford chose a smallish V6 with forced feeding

Turtle mentions that, that V6 is forced fed air similar to a big block gasser
of yesteryear

Laugh, because folks don't know what he is saying and double laugh as think he
gets the similar headache I get on similar techie discussions... :B



Current whizbang is direct injection, cylinder de-activation, variable cam timing,
very good materials/production science, etc

Next gen will be GDICI (gasoline, direct injection, compression
ignition...no spark plug). This may greatly reduce diesel in 'cars'
and light duty trucks...NOx will still be the bugger, as these will
have very high combustion chamber temps

As usual, the racers will have this first. Not just track anymore, but
street racers...pony cars...muscle cars...exotics/super cars...

DI gasoline engines were developed to meet strict emissions and fuel economy requirements so it is not surprising to see those numbers.

The problem with engine braking on the 6.2L is similar to thee Ecoboost. They have enough power that the engine doesn't need to exceed 3000rpm very often and there is not enough compression braking at that low of engine speed. Spin either one up to 5000rpm and it will help slow down. Not as much as a diesel with exhaust brake, though.

I wouldn't think Direct Injection would affect engine braking at all (gasoline application). In fact, most manufacturers increase compression ratio when they do move on to Direct engine. If anything, it should have a higher engine-braking effect. Gasoline DI engines still have the throttle plate and all the other bits associated with gas motors, they still have the pumping losses that make them less efficient than diesels.

bgum wrote:
I would think it would work better than a HEMI but it would be good to hear from someone with experience.

Why do you say that?

We have a 2015 Yukon Denali and it's lifetime avg (3000mi) is 18.7 and I got 20 from Boise to Twin Sunday at 80 mph with a 1000 lbs of tile in the back. I love this engine. My work truck is a 2500 with 6.0 and I don't like it.

I would think it would work better than a HEMI but it would be good to hear from someone with experience.

So this is a direct injection engine? Not sure how well that would work for a truck that tows since it leaves you very little compression braking for the hills.
It would be great to hear from someone who uses one.