Sweet spot for 6.2 diesels?

[Ratau]

At what rpm is a 6.2 engines fuel consumption and power output the best?

Is there a graph or table that show RPM versus fuel delivery for DB2 IP's?

Will there be a difference in this RPM between a NA or Turbo engine?

[Robyn]

The 6.2 N/A which is the bulk of the 6.2 engines as delivered will happily run all day at 2200-2500 RPM.

Pulling them down below 2000 RPM with tall gears seems to be a bad idea and the MPG can actually go down some.

The turbo fuel deilivery as compared to the N/A will always be more when you start working the engine harder and making the turbo work.

It takes fuel to make boost and with boost and more fuel comes more HP
The more power over the stock rating the more fuel you are going to burn.
Now once you get the little fellow onto the sweet spot the mileage can actually go up some due to the increase in efficiency with the turbo.

Banks engineering published some power and torque graphs with their products for the 6.2 engines and you can probaly get a copy from them or maybe find it on the net.

Hope this helps

Robyn

[Ratau]

Robyn

The direction I'm steering the topic is to seek for the sweet spot and then decide to do with final drive. Currently running 3.08 gears on 33" wheels. (23rpm = 1mph in OD) I don't see better mileage than 18 mpg and although the engine is in good condition but the old Blazer fall on it's face for the smallest uphill.

[More Power]

My 1982 6.2L GMC K1500 delivered 24-mpg fuel economy at 1850-rpm and at 65-mph.

The torque peak for these NA engines occurs at 1800-2000 rpm. The BMSFC (Brake Mean Specific Fuel Consumption) chart I have (that was produced by GM) shows best fuel economy occurs in this rpm range. Our work last summer while at Peninsular Diesel's shop in Michigan reinforced this. Our test of a NA 6.5 on an engine dyno produced best measured fuel economy at 1800 rpm.

If you want/need more horsepower, you'll have to run at a higher rpm. If you want best fuel economy, you'll need to run the 6.2 in the sub-2000 rpm range.

Jim

[Robyn]

Jim
Thanks for clarifying this subject.
I had an 82 Blazer with 3.42 gears and it did just about what you report on yours

The 86 Burb I had was setup with 4.10 gears and its mileage was not much less out on the road, maybe 21 tops.

Seems the 6.5 TD is no match for these numbers though :(

Too bad we cant have a mileage screw in the cab to trim the fuel rate when we just want to get there and save a few gallons.

best I have seen on my 94 TD Burb is 19 Hwy

Robyn

[More Power]

I should add that I drove that 3.42 geared 1982 GMC for about 150,000 miles with a 3-speed automatic. At 65-mph, engine rpm was in the 2400-rpm range, producing a fuel economy range of 17-19 mpg.

Installing an overdrive equipped 700R4 increased fuel economy by a minimum of 5-mpg at the same speed. :)

Jim

[damork]

My 1983 GMC Jimmy with a 6.2 consistently delivered 23-24 mpg with a 3.73 rear axle and a 700R4 automatic with the engine spinning 1850-1900 rpm, was doing it beyond 200,000 miles when I finally sold it.

[HH]

My 1983 GMC Jimmy with a 6.2 consistently delivered 23-24 mpg with a 3.73 rear axle and a 700R4 automatic with the engine spinning 1850-1900 rpm, was doing it beyond 200,000 miles when I finally sold it.

What size tire were you running?

[Ratau]

Jim & Damork

The tire size makes the difference so reply please.