Even while the 6.5 was being phased out, GM engineers at the Romulus Engineering Center continued to add refinements to the 6.5L turbo diesel engine.

As was discussed in this month's Turbo Tips column, the pistons used in the 1999 model 6.5 saw a reduction in compression ratio from 20.2:1 (in the 1997-1998 models) to 19.5:1. Lower compression ratio pistons improve engine durability by reducing the peak flame temperature during combustion.

The oil capacity of the 6.5 was increased in the 1999 model year to 8 quarts. Up from 7 quarts used in all earlier models.

The 1999 model C/K trucks are being equipped with the GMT800 cooling system originally intended for the new Silverado body style trucks. The added cooling provided by a 21" 9-blade composite fan and enhanced water pump allows for a stock power increase to 215 hp and 430 lb-ft. The '99 model engine uses the same hi-capacity engine oil cooling system incorporated in the 1997 model year. This increase in oil pump capacity is being used to increase oil cooler flow rates of 100% and allow additional flow volume to feed the piston oil spray nozzles.

New for 1999 is a 3000 rpm governed limit and an exhaust pressure regulator system designed to reduce white smoke on a cold start. Also, beginning in 1999, the catalytic converter was removed without affecting the emissions certification.

AM General plans to continue with the enhanced 6.5 Turbo Diesel into the foreseeable future for both military and civilian models. They plan to build these engines after production ceases at General Motors. The exact site for the new 6.5 engine plant hasn't been determined yet, but Dayton Ohio is the odds on favorite. Reports on this exchange mention that several GM 6.5 engineers are being transferred to AMG, which should provide a seamless engine production transition under the new management.

Our sources inside Detroit Diesel Corporation say the new GM Duramax 6.6L diesel trucks (and new Dodge diesel trucks) will be offered with a new 1000 series Allison overdrive automatic. The 1000 series is a 5-speed automatic with a 4th direct gear of 1:1, and a 5th gear 0.71 overdrive. This transmission is rated up to 375 HP and 545 lb-ft of torque, and a GVW of 22,000 and GCVW of 26,000 lbs. (This lends weight to the reported GM DMAX power output.)

DETROIT - General Motors announced recently that it has signed a memorandum of understanding with AM General Corporation to explore future product, marketing and distribution opportunities. Contained within the final agreement, GM will acquire the ownership of the HUMMER brand name world-wide, and will assume responsibility for marketing and distribution of HUMMER vehicles in 2000.

Peninsular Diesel reports they are developing a new high-end 350 horsepower marine 6.5 Turbo Diesel, with several examples now in durability testing. Additionally, Peninsular has an experimental on-road 6.5 engine that has been dyno'ed at 400 horsepower, using a twin turbo setup. Expect some new product offerings from Peninsular in the near future.

AM General offers this 6.5L Turbo Diesel emblem (Part # 06008595) used on their civilian Hummer. AMG also has another almost identical emblem which reads 6.5L Diesel (Part # 06008839). Retail price for these are $10.62 and $7.45 each respectively from any AMG dealer. The emblems come with double-stick tape, so they can be easily installed anywhere on your truck. Visit the AM General corporate web site and take advantage of their dealer locator.

The 6.6L Duramax diesel engine (Isuzu designed - GM built) that GM will use to replace the current 6.5 in their C/K truck line is scheduled for release in the 2001 model year GM trucks. This means the new diesels will be available to the public during the fall 2000 introduction of the 2001 models. The Diesel Page is scheduled to receive a full product description on the new GM diesel sometime soon. This GM info packet should include pictures, power specifications and other technical data. We plan to run a feature on the Duramax as soon as that information becomes available.

The Duramax will be running with 4 valves per cylinder, an electronically controlled HEUI common rail injection system, and most likely an intercooler. We'll have to wait and see if the rumored dual overhead cam and 550 lb-ft I've heard about are a reality. If so, the entry level power will be competitive.

Due to the tight emissions regulations for the light-duty vehicles, only the 8600 GVW and up trucks will get the Duramax. This means all the light-duty 1500 and 2500 series trucks and Suburbans won't have a diesel option. However, rumors have it that all three of the auto manufacturers are working on a lightweight hi-tech V-6 diesel for the lucrative Sport Utility market, so expect some progress in this area. Higher oil prices will spur them along.

It took over 18 months from the time I first heard of the Duramax 6.6 before GM officially announced their intentions. I heard the first reasonably solid Caterpillar rumor about a year ago, so the possibility is still alive for the GM trucks to have the dominant diesel puller in the yet to be announced "Super Duty" line of heavy-duty GM trucks. The first Caterpillar yellow Silverado Super Duty 3500 will shake the industry.

The Diesel Page 6.5TD Power Project continues to move forward. Most of the planned upgrades have been installed, with the exception of the Jet Performance 4L80-E automatic overdrive transmission. The project 6.5 is performing beautifully, and is now exceeding every design goal set for it.

Jim Bigley

Back to the What's New Page.
turbo@thedieselpage.com
www.62-65-dieselpage.com