GM's Service Information (SI) has 2016 vehicles listed already in the drop down boxes. We are less than 10 years out with the 54.5 mpg standards. They are going to have to figure this out soon.
GM's Service Information (SI) has 2016 vehicles listed already in the drop down boxes. We are less than 10 years out with the 54.5 mpg standards. They are going to have to figure this out soon.
You're looking at real world numbers closer to 40mpg. I believe it's doable. My turbo Sunbird has achieved 36 with my wife driving. I also believe we've lost ground. The two Aveos we have use smaller version of the same engine in the Sunbird yet they achieve mid to high 20's on the highway! What??? Our 2001 Malibu was also high 20's. Not impressed when cars of the '90s were high '20s to low '30s with V6 engines and Chevy Sprint / Suzuki Swift was in the '40s.
Look for different NOx controls so autos can move toward higher intake mixture temps. Stop playing HP wars and build cars that get good mileage. Put Vroom-Vroom go fast into a different category and let buyer pay for privilege of going faster and using more fuel. And no more "cash for clunkers" that wipes out used car market!
Here's something to think about. The 99-02 Chevy minibuses in our fleet achieve roughly 9-10 mpg on average with the 5.7l engine. Those buses were also available with the tiny 4.3. The tq/hp ratings of our 5.7 are 330 / 245 and they move the bus along just fine. When I spec out a new bus the only engine I can get is the 6.0 which is generating average fuel economy numbers in the 7-8 mpg range. The 5.3 is rated for 338Tq/315hp, more than the L31, yet GM won't supply that engine in anything larger than a single wheel chassis cab.
Ford likes to do the same with the 6.8L V10 but with enough fighting you can get the smaller engine. Ford has the bus builders convinced that asmaller engine won't survive in a dually chassis with 10,000lb gvw but we've got vans with 200k and the 5.4 is still running just fine. And the fuel economy is 2-3 mpg better. While that may not sound like much, in a fleet using over 20,000 gallons of fuel a month that 2-3 miles per gallon is worth money.
Hands down the old L31 is a better truck engine than the 5.3 or even 6.0. The reason GM does not offer the 5.3 in a bus is lack of low end torque. But what do they expect with a smaller displacement engine and gigantic ports.Originally Posted by 1project2many
While the actual design is over 10 years old, my Titan does as well as any V8 fullsize truck on the road on gas, especially around town.....The reason, lots of low and midrange torque that keeps you off the throttle in daily driving.
I mention this because my sisters 14' 5.3 was rated something like 22 mpg. and my Titan 18 mpg. We ran the same trip, have almost the same size tank, got almost the same range, and both got 18-19 mpg running 70-75 mph. Pretty sad that GM fuel economy does not even come close to advertised.
Last edited by Fast355; 04-16-2014 at 07:21 AM.
No torque, but the anemic 4.3 was available with loose converter in one ton applications. We're in town, stop and go, so not much help no matter what size engine or where torque production is. BSFC is maximum at peak torque so I'll take a loose converter and power vs torque to move along.
I will say that shop truck with 6.0 pulls stuck buses all day long without breaking a sweat. I can get reasonable mileage on the highway if I keep it below 70. But as soon as I hit a couple of lights there goes the economy.
Currently rebuilding 5.7 engine for bus and trying HT383 cam. Nice experiment for an otherwise stock vehicle.
Just my $.02, I would try a set of 1.6:1 full roller rockers rather than the HT383 cam. The HT383 cam has a bit more overlap than the L31. But it will be interesting to see what happens.
I have the 4.3 converter in my 4L80E in my G1500 with the 5.7.
Not sure where you have seen that BSFC was highest at peak torque??? BSFC is often LOWEST at peak torque and falls off on both ends. Take the project Vortec TPI built for the something old, something new article.
It peaked in BSFC between 3,300 and 5,000 rpm and was relatively flat between .4 and .43 lb/hr/hp, which is a stellar number for an old 5.7
http://www.gmhightechperformance.com...ck/page_3.html
Last edited by Fast355; 04-16-2014 at 03:21 PM.
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