iwantaCUMMINS

Just wondering.

phox_mulder

Length of the stroke basically.

Longer stroke with the same horsepower equals more torque.

I always wondered when I first started as well.

Saw gassers advertised as 300 HP and 300 Torque.

Whoo, hoooo!

Same HP Diesel gets 600 Torque, and at lower rpm.


phox

welder27

It also has to do w/ the compression in a diesel...a gasser has like 8:1-10:1 and a diesel has 17:1 (just ballpark figures). More compression = more energy released. And the turbo will give you more torque too.

Haulin_in_Dixie

And there are more btu's of heat in diesel fuel than gas.

J BODY

Just a few short years ago the v-10 was king in the torque department in the Dodge truck line. Gobs of torque at a low rpm. Now the diesel is king, but the mileage seems to be slipping down as the torque wars go up. I think we are on the down hill curve on the diminishing returns graph on power vs. economy.

Dieseldude4x4

Stroke and more work from the diesel fuel.

welder27

"I think we are on the down hill curve on the diminishing returns graph on power vs. economy."

I've never thought of it that way...interesting, but very true. The big rigs only get somewhere between 5-9 mpg when hauling on the highway. But I guess when you think about it, if you had a gasser that could possibly haul as much weight as a big rig they'd be getting around 2-5 mpg.

2manydogs

When you think about your average Sub-urban with a big block getting 10 MPG at maybe, 7,000 lbs., 6 MPG moving 80,000 LBS. is pretty reasonable, dontcha know! Also, on the torque question, diesels have a longer burn time, as in positive cylinder pressure for more degrees of crankshaft rotation. Another plus that helps with the longer stroke. Jim

infidel

My feeling is that emissions regulations is the main culprit for lower mpgs.
It really doesn't make sense to me when you consider that even though an individual rig will make less smog what about the additional emissions produced by the extra amount fuel that must be delivered by truck, pipeline, etc?

j-fox

The lose of mileage is due to EPA regs.
Their process makes an engine use more fuel to reduce what comes out of the tail pipe. NEVER understood this idea.
To save the world we must use more??
If you are old enough to remember carberators, you can see whay they did.
I had a 71 chevy, 2bbl cab 350 , from factory it would at best get 14 on the highway.
I removed the heads and replace them with smaller chamber heads for a raise in compression and dropped a smooth 4 bbl carb. guess what it ran smoother and could get 21 on the highway. Just a little humor, but the world is still here!!!
They are doing similar things to the Diesel engine.
The old 12 valves could be tuned to get high 20's for mileage.
Try that with anything made today!!!

End of rant!!

Redleg

You match a gasser to the cubic inches of a big rig, they might match mileage with the rig loaded and the gasser empty.

I'm sure the compression ratio is a factor too.

Haulin_in_Dixie

You did good. I saw many Chev pickups fromt he late 70's and early 80's that got 7 and 8 mpg and had a hard time getting over 10. The Fords were pretty well known for 300 six getting 17 with a stick, 302 getting 15 to 16, and 460 around 15. My 79 Ram van gets 14 on a good day. Fuel injection brought in some better mileage. The '98 Dakota, 4wd, 318 got 17 all highway. Want mileage, I had a 91 GEO, got 47 out of the showroom, on the highway it would get 50 plus and had good power for running 80 on the back roads. Little 3 cylinder was a good motor especially with the cat off it. Right now I have a 86 Jeep Commanchie engine rebuilt 15,000 ago, gets 17 and celebrates when it gets to the top of a hill. "I made it, I made it, I made it"

Haulin_in_Dixie

I didn't notice this one before. You have to be an old codger like me to answer that one. It used to be done that way quite a bit. A stock Chrysler 413 in a Mack with a four by four. A 427 Chevy in a tandem axle, tow speed rear, pulling gross loads, ok not 80,000 but the old limits, 73,280 and 71,000 in New York. Yeah the Chevy would get 4 mpg as a chassie cab, 4 with the equipment to pull, 4 with an empty trailer, and 2 or 3 with a gross load. It would last less than 100,000 miles if you could keep the heads and rocker arms on it long enough to get there. The 348 was even worse. In the 60's there were a lot of them and the smaller diesels started to be the standard, 4/71 Detroits, 6/71 Detroits, 237 Macks, 220 Cummins in the bigger trucks. All of them guarenteed to get 4 empty and close loaded. Second gear was normal for climbing a hill. Todays stuff is fantastic, my Dodge has more power than a million or so miles I drove in big trucks.

Climbing some of the passes in the Northwest, you could see the smoke trail for miles back down the pull as you went up. No air either, prop the door open with your foot for a little more air at 5 mph going up. Going down was worse, you knew what you were doing or you died. Several times with the little engines I smoked the brakes at the high speed of 10 mph or so and stopped at the bottom glad to be alive. A short one that would weed out the inexperienced was Fancy Pass. You were always glad to get that over with. Technology will demand more mileage and power.

The diesel mileage keeps getting better and better and the comfort and safety is better and better.

j-fox

I better clear up something!!!
The chevy I had was an Impala, not a truck!!
I had several friends at the time who did the same /same car.
Then got smarter and bought Dodges!