Engine/Transmission (1998.5 - 2002) BSFC Comparison

[Vaughn MacKenzie]

Ever wonder how fuel consumption curves compare between the different generations of engines that have been available in HD Ram pickups? TDR has published BSFC charts (brake specific fuel consumption) at various times over the years which indicate expected consumption rate per horsepower at various RPM. I found some of these and decided to dump the numbers in Excel in order to superimpose the curves. I found a 1st Gen 160hp intercooled VE chart, early 2nd Gen 175hp P-Pump, and an early 24-valve 235hp manual VP44. Here are the results for your enjoyment



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[mwilson]

Nice chart, makes the point quite nicely.



Mike.

 

[The patriot]

Got one with a 215 pump?

 

[Mhannink]

Got one with a 215 pump?

i am curious the difference between the p pump models, also would be nice to see the common rails.



based of that chart it looks like it would be best for a p pump to run about 1700, its a little higher then the best spot, but gives you a little extra power to keep from lugging while cruising.

 

[Vaughn MacKenzie]

Patriot there is a 215 ISB one, I will plot it in as soon as I get some time. I do recall it uses slightly more fuel per HP across the board. I think there is a HPCR one somewhere too.

MHannink you can see how fixed timing of the P-Pump causes a straight ascending line as RPM increases. Bear in mind when timing is set higher then it will push the "sweet spot" up higher. I think Joe Donnelly commented 17-18 degrees puts the sweet spot in the 1900-2000 RPM range but don't quote me on it. Based on the chart theoretically the P-pump 12-valve will get the best mileage of all engines when operated at its ideal RPM, it uses 2. 7% less fuel than the 235hp 24V at 1600rpm. But if gearing isn't ideal, such as towing with an automatic where you need to drop out of overdrive, the 12-valve quickly gets pushed out of its efficient zone. If the charts are true then you can crank along at 2500 RPM in your 24-valve and get the same MPG as a 175hp P-Pump rig does at 2000. Another way to look at is the 175 P-pump burns 10. 5% more fuel per HP generated than a 24V at 2500 RPM, which is significant.

It is interesting the 3 engines in the comparison are about the same efficiency at 1800 RPM.

 

[HBarlow]

The chart is interesting. If all is based on accurate testing the 24 valve is obviously the more desirable engine of the three for fuel economy as well as engine operating band. I'm surprised because I had always heard/read on TDR that the 12 valves weres so fuel efficient. It seems that the 24 valve heads and improved air flow made a huge improvement.

 

[The patriot]

Vaughn, I meant a P7100 215 engine.

 

[Vaughn MacKenzie]

I looked through a ton of issues last night and only find the ones I posted above. I only have about 10 more to leaf through.

 

[S.Morris]

Be interesting to see how the various common rail engines compare also

 

[Nyoest]

Fascinating. I will dispute it as far as my experience though.



My truck is a 96 xcab 4x4 5spd 4. 10 longbed 12 valve. Wife's is 01 xcab 4x4 4. 10 short bed 6spd 24 valve. Both stock tire sizes, both cooper tires and mileage with the wife driving hers 17. 5 on average. Wife driving mine 20 on average. Many variables do come into play but whenever we take a trip it's always in my "fuel saver".

 

[Vaughn MacKenzie]

There is definitely a lot of variables. Where do you have your timing set?

My '96 in my sig pulling the travel trailer I used to have to Maine and back averaged 13. 5mpg for the trip traveling at about 65mph. The same trailer behind my 2-wheel drive 6-speed '03 HO consistently got 15-16 at the same speed. Being 2wd probably helped though.

But unloaded on the highway the 2wd '03 got only the same MPG as the 4x4 '96 at the same speed, 20-21 at 70-73mph.

I wish I had a common rail BSFC chart to compare too, I don't think TDR ever published one.

 

[Nyoest]

My timing is now set at 15. 75 degrees. I still get 21. 8 with a custom plate and PDR cam. When I was crazy about the the numbers it was bone stock 13 degrees.