ISUZU has added a new engine and made wheelbase and chassis component changes on its 12,000-lb GVWR truck, which it has renamed NPR ECO-MAX.
“It is a much different vehicle than the rest of our product line, so now it's been given a new name,” said Rob Cadle, manager of product planning. “NPR ECO-MAX is a way to differentiate it. We made so many changes because we want to focus on a very high fuel-efficiency commercial vehicle.”
To accomplish that, Isuzu is using the 4JJ1-TC, a 3-liter, 150 hp engine with 282 lb-ft of torque and an Aisin 6-speed automatic transmission, with an expected 20% improvement in fuel economy.
The truck is EPA2010-certified using a chassis dynamometer instead of an engine dynamometer, a method that dictates certain body and tire requirements:
Body limits (to be noted on the incomplete vehicle document): vehicle frontal area limit of 73.1 square feet; vehicle curb weight limit of 9660 lbs.
Tire specifications (to be controlled by Isuzu distribution): Bridgestone R250 steel rib (highway) tire is standard; and the rear traction tire will be a factory-installed option for cold-climate operation.
The truck has a different frame and driveline from the other N-diesel models. The frame width has been narrowed 4" to 29.5", and the frame has a lighter weight for lower GVWR: 5600 cab/chassis curb weight, 150 lbs lighter than the 2009 NPR, even with the new emissions equipment.
The frame narrows to 29.5" ahead of the third cross member. The side rail section has been reduced .08" to 8.43". The frame has a yield strength of 44,000 psi.
Truck body partnerships
The NPR ECO-MAX has two programs with body partners:
Aero Van Body Program: composite construction, 85" wide × 79" high body size; 12', 14', and 16' length options; cargo ramp and tie-down options; demonstrated fuel-economy improvement of over 10%; 19 mpg measured fuel economy, fully loaded, at 55 mph.
Tool Pro Utility Body Program: open and enclosed versions: lightweight aluminum construction with 1750 lbs for enclosed van and under 1000 lbs for open body; 10-year limited warranty on the body; ladder, towing, and security packages.
Cadle said the completed vehicle frontal area can be calculated for several industry-standard body sizes. A 96" wide body must be limited to 79" inside height and mounted close to the frame rail to meet requirements. Isuzu's front area calculator can be used to set up van body mounting (www.isuzutruckservice.com).
The 4HK1-TC engine, with 210 hp and 441 ft-lb of torque (manual) or 190 hp with 397 ft-lb of torque (automatic), comes on the NPR-HD (14,500 GVWR), NQR (17,950), and NRR (19,500). New parts are the cylinder heat, piston, con-rod, crankshaft, block (high rigidity), and parent bore (eliminates cylinder liner). Fuel economy is improved by 8% over 2010.
The steering system has been modified to allow increased wheel cut angle. Vehicles with 16" tires (ECO-MAX and NPR-HD) see wheel cut increased from 42.5/32.7 to 49.5/35.5 degrees. Vehicles with 19.5" tires (NQR and NRR) see increases from 42.5/32.7 to 46.5/34.3 degrees. Turning diameters circles are reduced by 1.2/2.8 feet on average on 19.5"/16" tired vehicles, respectively.
NRR's front gross axle weight rating has been increased from 6830 to 7275 lbs through the use of higher strength material in the axle, with no dimensional change. An increased-capacity power steering pump and steering gear have been introduced along with the changes. Front spring rates have been increased to support the higher gross axle weight.
New for the 2011 MY, all vehicles with an Aisin automatic transmission will feature PTO torque converter lockup. In park or neutral, lockup is on when: the PTO signal is on; the engine speed is more than 1200 rpm; the turbine speed is more than 1150 rpm; or the output shaft speed is less than 250 rpm. In park or neutral, lockup is off when: the PTO signal is off; engine speed is less than 1100 rpm; or the output shaft speed is more than 300 rpm.
On the NQR and NRR, the side-mount fuel tank has been moved backward due to space required by the SCR system. The tank-mounting bracket is in the region where the frame will be cut for stretch. The tank will have to be removed prior to the wheelbase stretch. A new fuel cooler requires the fuel-return line to route inside the right-hand frame rail. The line will have to be extended for stretch. Because of this, the in-rail tank will be used for 2011 stretch. Fuel lines will still have to be extended, with no tank removal required.
The DEF level gauge is integrated into the dash on all 2011 diesel models. If the driver does not refill the DEF tank, the vehicle will implement a series of speed restrictions. If the vehicle is run completely out of DEF, the vehicle speed will be limited to 5 mph. Similar actions will be taken if a fluid other than DEF (water, diesel fuel, etc) is put into the vehicle, or if the SCR system components are tampered with or malfunction.
Cadle said US production of N-Gas vehicles will resume in April. Vehicles will be built in partnership with Spartan Motors and product specifications will be very similar to the 2009 N-Gas product: it will still use the GM 6L V-8 Vortec engine with the new 6-speed GM automatic transmission; and 12,000 and 14,500 GVWR with standard and crew cab configurations will be offered.
Cadle said that bodies up to 91" inside height do not require special engineering approval, assuming that: vertical CG is less than 63" above ground; 30-40% of the weight is located on the front axle; and no axle is over GAWR with the vehicle level loaded to GVWR.
He said 102" wide mirrors can be ordered as a port-installed option for use with 102" wide bodies (14,500 lbs and greater GVWR). They can also be installed at the dealer after the vehicle is wholesaled. NPR ECO-MAX (12,000 GVWR) is not approved for bodies over 96" wide.