Is there a comparison chart between a 6.6 Duramax and the 454.


Posts on the RV.net by nonbelievers cannot or do not want to believe the mileage that a 6.6 can get. They may not want to admit that they did not do their homework before buying a tow vehicle that drags a 32 foot trailer. The weight charts show the crewcab with the 8.1 can haul 15,500 as to my 15,400 (extcab duramax). These guys are really funny http://www.dieselplace.com/forum/smileys/Big Smile.gif





Thanks ahead of time

There is a question that will always start a pizzing match between Diesel and Gasser owners.

I have no hard numbers to give you, but I do know that if gassers are so much better, then why aren’t the big rigs running gas instead of diesel?

Personal experience is that my 3500 7.4 liter SRW would always, consistently get me 8-10 mpg. Air on, air off drive hard, drive easy, it just didn’t seem to matter.

What did matter was pulling, the gas motor would always handle the load but at a much higher RPM burning more fuel. My Dmax handles towing in a lower RPM range with much less effort.

Too many conditions can make a drastic change in mileage. I pulled a Corvette out to a show from KC to <st1:place><st1:City>Effingham</st1:City>, <st1:State>IL</st1:State></st1:place>. in a enclosed 19ft tandem, (approx. 7-8k lbs.). On the way out, west to east, I got 17.2 mpg, on the way back, into a head wind from an approaching storm, it went down to 14.8. Either way, my gasser would have never even come close to these figures.

Just my .02 cents worth. Edited by: HD-Nate

for what it's worth.... pulling my 20ft toy hauler loaded the same from Tucson to Phoenix with cruise set at 72. Both trucks equipped the same outside of engine, trans and gears.


my 2002 stock 8.1L/A (with 4.10 and 285's) (20,000miles on truck) - 6-7mpg up and back. Wish I had 5th gear lock out, shifted often.


my 2004 stock D/A with the same 285's (2500 miles on truck) - 10mpg up and back. Never needed lock out only shifted once or twice.


again just my eval on the two engines.


Also the dmax was better in the winter pulling the same trailer in the hills going up hunting in the mountains of Northern AZ. (from Tucson @ 2400ft to Egar area @ 9800ft)


edit: At 3K miles I'm gettin 12.5 MPG around town. The best I could get from my 8.1L was 13 empty on highway.


cmcEdited by: CMC-GMC

I have had a 98 3500 dually with the 454, and a 01 3500 dually with the 8.1L. the 454 got 6-8 mpg towing approx. 6500-7000lbs. the 8.1L got8-10mpg. towing the same weight depending on the terrain. I assumed it did better due to the 5spd. allison. my current 04 D/A on a recent trip to florida towing approx. 7000lbs. averaged 16.9 mpg. this was the actual calculated mpg. the DIC mpg. was actually better at 17.4 mpg. to someone who tows alot of miles the fuel savings are tremendous.

I had a 94 7.4L C3500 CC. That baby got 9.5 miles to the gallon solo, loaded, or just sittin' there. My '01 K3500 gets 16.5 around town, 19.5 on the highway(solo), and 14.5 loaded (9K lb 5ver).


No contest....http://www.dieselplace.com/forum/smileys/Clap.gif


JP

What alot of people miss also is that a diesel can run at its peak horsepower for extended periods without harm. Run a gas big block wide open for extended periods and see what happens.

Those gasser guys are'nt worth our timehttp://dieselplace.com/forum/smileys/Throw%20Up.gif


Seriously though, there is simply No comparison between a gasser and a diesel. The diesel will consistently get better mileage, the fuel is generally considerably cheaper, the longevity is MULTIPLES of the gasser and the overall power is better. (remember, its TQ. not HP. that tows the load)


I know it sounds stuck up, but it's true; The gasser guys are just jealous cuz they could'nt or would'nt cough up the extra $$ for the diesel. Period.


Personally, I just did my first tow with my Dmax and averaged 9.4 MPG round trip over the cajon pass and back with just about 1600 Miles on the truck averaging overall about 65mph pulling a 9K toybox. I got up to 75 at times without really trying. Im sure it will improve with break in and less speed

FWIW, The 8.1L is a 496 cubic inch motor. Not a 454.

FWIW, The 8.1L is a 496 cubic inch motor. Not a 454.





In addition, for the most part it's still the same animal. Look at a bare long block and it's almost identical to the Mark VI 454 and 502 that GM sells in it's performance line. There are some cylinder head and intake changes, but the basic design remains the same.


I too had a 454 powered truck- '90 K3500 SRW. The engine pulled like mad, but pulling the race truck it'd be lucky to break 8 MPG (5K load, open trailer). The Dmax gets 13.5-14 pulling a 28' toy box (7K load, more wind wall).


Dmax wins hands down. IMHO.


A local fellow pulls a 26' with a SC dragster, and won't use anything but the 8.1. He's been a big block nut for 25 years, and won't change.


To each their own, I guess. Edited by: MinnDmax

remember, its TQ. not HP. that tows the load

Torque is just a measure of force, with no consideration given to speed. Horsepower is torque times rpm, i.e. the combination of the force you can generate and the speed you can generate it at.

Maybe you don't care about the speed at which you can tow a load, but I sure do.Edited by: ZFMax

I sold my 454 k3500 dooley last week. After pulling the backhoe with the 2500HD, I decided I no longer needed it. I still have a couple of other trucks at the farm if something needs to be pulled and the dmax is not available and a fellow offered more than I could refuse for the gasser. It pulled strong but loved the gas stations too much. With the hay wagon loaded or the flatbed with the backhoe on it, the gasser rarely got better than 6-7 mpg and the dmax will do around 12-13.

Don't mean to be anal but the 8.1 L is the 502 motor.


(62 cu-in per Litre approx.) http://www.dieselplace.com/forum/smileys/Embarrased.gif


I know my old 350 punched out 1973-88 C20 HD, (long story, many parts), got 13 mpg no matter what I did to improve milage. I built it for pulling and it loved to drink.


My 04 K2500 got 15.5 mpg the first tank and I haven't filled up since. Too much salt on the road just to go to work. I take my beater to work. http://www.dieselplace.com/forum/smileys/Big Smile.gif

remember, its TQ. not HP. that tows the load

Torque is just a measure of force, with no consideration given to speed. Horsepower is torque times rpm, i.e. the combination of the force you can generate and the speed you can generate it at.

Maybe you don't care about the speed at which you can tow a load, but I sure do.


Your right, but Torque is what gets the load moving. My point was that horsepower is always refered to as the important number where Torque is more important.


HP keeps you going yes, but torque is the more relevent measure.

Back in March I got out of my 2000 GMC 1 ton 4x4 CC with the 454. While it had lots of power there is just no comparison to a Duramax.


Last winter coming back from Houston (Houston Livestock Show) pulling the stock trailer with 1 ton of shot in it. Head wind at 40 MPH. Speed of 70 MPH(I tried anyway) 5.5 MPG!


I know for a fact that the Duramax would have done alot better.


Around here I get about 13 MPG average. (farming)


With the old 2000-454 I got about 9 MPG average. (farming)

I inherited my '97 Prowler fifth wheel and a '99 GMC 2500 with the vortec 7400 engine to pull it with. The big block had enough power, but it came at the expense of poor mileage. I traded the '99 GMC in on my current '01 Silverado 2500HD with the Duramax. I have the same driving habits, drive the same daily roads and pull the same fifth wheel now as I did with the big block. Here's my real-life comparison...


Empty driving: 454-11 to 14 mpg, Duramax 17-21 mpg


Towing 10K fifth wheel: 454-5.5 to 8.5 mpg, Duramax 10 to 13 mpg

My point was that horsepower is always refered to as the important number where Torque is more important.

Torque is just force, with no regard for speed.

Horsepower is the combination of torque and speed.

So when you make a statement like that, you're effectively saying it matters more how hard you're pushing than the combination of how hard and how fast you're pushing.

I contend that it's the combination of how hard you're pushing and how fast you're pushing that defines performance, and if you consider one without considering the other, you're looking at a meaningless number.

I mean, you can make a million ft-lbs of torque with a common hand-held battery powered drill motor if you gear it deep enough. You'd have to time the revolutions with a calendar, but you could do it. Torque by itself, without considering the speed it's made at, is just simply not a meaningful number for understadning performance.

And when you consider the speed you're making it at, you're talking about horsepower.

Davesmax.....I think it's a 496, not to be confused with the older 502.

I got to chime in on this "little" debate.


I am on my second Duramax, loved the first one, the second one is even better, will probable let my father "buy" my 04 LB7, and get an 05 LLY, when they get the "new production bugs" worked out of the new engine, but I am sure it will be great.


Back to the HP vs Torque debate. WHAT COUNTS US THE USEABLE HORSEPOWER!!! We don't go out and buy a $100,000+ farm tractor and check the torque rating, no they are rated in HORSEPOWER, that is what we pay the big bucks for. Now a farm tractor has its peak HP at a few hundred RPMs under max RPM, and you run full throttle most of the time, letting the load set what RPM she is able to "pull" at, say 2150 High Idle, 2000 RPM rated RPM and pulling at 2010.


What matters on our trucks is that at the driving RPMs. 1500-2400, the Duramax has much greater horsepower than any gas engine available in these pickups. Horsepower is a function of torque and RPM. Would you rather have an engine that produced a whopping 800 ft lbs at 1000 rpms, but only 400 ft lbs at 2000 RPMs, A LB7 or an LLY would greatly outtow that engine, even though that other engine would have more peak torque. What matters to me is that the LB7 has about 520 ft lbs from 1500-2500, which is the range that I operate in, and the LLY has about 590 in that range.


The great thing about the LLY, is besides decreased Turbo Lag, the increased torque amounts to about 13.5% more useable horsepower in the RPM range I generally drive, which means much better acceleration with or without load without having to go up to the shift point.


A LITTLE COMPARRISON CHART


AT 2000 RPMS, the LB7 creates 198 HP and LLY 225 HP, to create the equivalent HP, the RPMS that are required for the 8100, 6000 and 5300 are given.


LB7 LLY


8100@415 ft/lb 2505 2843


6000 @340 3059 3470


5300 @280 3714 4214


The Torque figures for the GM gas engines were taken from the GM torque curves on the GM powertrain website, with the numbers taken at 2000 RPMs, granted the torque max for the 8100 is 450, 360 for the 6.0 and 325 for the 5.3. The calculated RPM requirement would only be scewed a little bit on the 6.0 and 8.1 and a little bit more on the 5.3, since the RPMs that are required to produce the HP are so high, and closer to its torque peak.


What you cannot argue is that while the LB7 and LLY produce 198 and 225 HP at 2000 RPMs respectively, the 8100, 6000, and 5300 only produce 158 hp, 129 hp, and 106 Hp at 2000 RPMs.


That is why they ain't got the grunt to tow in overdrive, and the RPMs have to scream. An LLY at 2000 Rpms should tow and accelerate at the same rate as a 6.0L at about 3500 RPMs, which gives that seat of the pants 'power' feel.


Good luck on this one now,


Hunter

You're absolutely right.

All the high torque rating really means on a diesel is that it makes it's power at relatively low rpm. It doesn't somehow make the diesel's 300hp stronger than some other motor's 300hp, it just means you don't have to wind it up to get it. Which is a good thing. But to say the torque figure is what matters, not the horsepower figure, is wrong. That's what I was addressing.

ok I agree, but what Im addressing is that horsepower is not the only factor. I know it definately matters, but so does torque and it seems to be overlooked alot.


Your drill motor analogy was good http://www.dieselplace.com/forum/smileys/Big Smile.gifEdited by: 2MuchFun

Don't mean to be anal but the 8.1 L is the 502 motor.


(62 cu-in per Litre approx.) http://www.dieselplace.com/forum/smileys/Embarrased.gif


I know my old 350 punched out 1973-88 C20 HD, (long story, many parts), got 13 mpg no matter what I did to improve milage. I built it for pulling and it loved to drink.


My 04 K2500 got 15.5 mpg the first tank and I haven't filled up since. Too much salt on the road just to go to work. I take my beater to work. http://www.dieselplace.com/forum/smileys/Big Smile.gif





The 8.1 is not the 502. The 8.1 is a different design and is 496 Cu in. I asked a GM representative that very question several years ago when they first came out. They insisted that it is a completely different block. The 502 is from the decades old 454 block.

Thanks for all the input. I kind of thought the 454 might be different than the 8.1


Also a special thanks to JDTRIP. I have gotten the same towing mileage 16.5 average while towing a 25 ft 5ver. The gas guys on the RVnet say that is impossible. Yes it was in the UP of Michigan and flat land but the mileage was amazing. Going to do a trip to New Mexico through the Grand Canyon . Do not expect 16 but it has to be better than a gasser.


Truck is an 03 GMC 2x4 extcab D/A shortbed positraction

For the torque/hp debate, i would much rather have my 525hp Cummins and 1900# of torque than a hopped up Dmax in my Peterbilt pulling 80-120,000#.


The Dmax has more torque at 1000rpm than any GM motor makes anywhere in the powerband.


Also the peak torque is now at 1600 rpm which is cruising speed and the peak hp is way on up the rpm band.

my '03 2500HD 4x4 ext cab D/A gets a solid 4-5mpg better than my '02 2500HD 4x4 ext cab 6.0 did, and the Dmax is not broken in fully yet either!

General info, bore and stroke of the following engines-


454- 4.25" bore, 4" stroke


502- 4.446" bore, 4" stroke


496 (8.1) - 4.25" bore, 4.370" stroke


Dmax 6.6L- 4.055" bore, 3.897" stroke


The conversion from cubic inches to liters is .0163. Example- 454 X .0163 = 7.4002 liters

After checking all the places I could find the specs on them they all say the 8.1L is a 496. The 502 is the 8.2L Heres a place wher eyou can get a short block 8.2L. I got a friend researching one to put in place of his 454 in his motor home. http://www.sallee-chevrolet.com/ChevyPartialEngineBlocksStandardDeckBigBlockV8s/502cipe.html





Oh and my old GMC 454 dually got 9mpg loaded (cab over pulling vw baja) or unloaded. Man she loved the gas stations.


cmc

General info, bore and stroke of the following engines-


454- 4.25" bore, 4" stroke


502- 4.446" bore, 4" stroke


496 (8.1) - 4.25" bore, 4.370" stroke


Dmax 6.6L- 4.055" bore, 3.897" stroke


The conversion from cubic inches to liters is .0163. Example- 454 X .0163 = 7.4002 liters





Sorry guys, math error http://www.dieselplace.com/forum/smileys/Embarrased.gif


And for the record, I didn't mean to give the impression that the 8.1 was the same design as the 502 motor. I assumed they would have updated from that pig. I was just doing a quick math exercise, (which I hosed up. DOH!)http://www.dieselplace.com/forum/smileys/Ermm.gif

454 vs Dmax? Nobody has a stick big enough to make me go back to a 454! Traded in a 96 454 3/4 ton extened cab L/B 5 speed. Nicest truck I ever owned, until now. I pull a 24' steel horse trailer with 10' living quarters, completely loaded with 3 horses and enough food and water for a weekend it tips in at 14,400. Phoenix to Flagstaff is 1200' to 7200' over about 150 miles. A few long pitches that just tore the guts out the old girl. 3rd gear screaming and hotter'n blue blazes for miles and 35-45 mph. Get to Flagstaff and fillup - 3.6 to 4.5 mpg depending on the traffic and ambient temperature.


Now with the Dmax/Allison Juice at level 2 same trailer and weight its a much different story. I do the speed limit. Two different trips - one with the cruise at 65 I got a true 9.4 mpg. Second trip I 'drove it like I stole it' the only limiter was the EGTs. So I drove 70 to 80 mph, got to Flag and filled up and got an honest 9.1 mpg.


Around town - to and from work, the best the 454 ever got me was about 9mpg. Same daily trips in the Dmax I get 14.2 to 16.1. The reason for the delta is quite simple, at level 4 occassionally I just can't stop myself from blowing the doors off a few of the smarta$$ rice burners and a pony of two!


I made the right choice and will never go back to gas!