GM's Duramax Diesel engine

JATO_RaT · Oct 5, 2001

Re: GM\'s Duramax Diesel engine

Richard, perhaps I am misunderstanding this. I thought your point seemed to indicate that the Duramax just barely beat the specs of the Ford and Cummins engines so as to attract customers by enticing people with specificationitus, especially those who feel it necessary to have the more is better mentality. My end point here is that I am offering the author of this post some confidence regarding his original post and really don't care about brand or diesel wars. Pointing out that the Isuzu built Duramax diesel for GM has all the makings of success and that even with its aluminum heads, will still in all likely hood be a big contender. The Allison transmission people have a reputation as big as Cummins and if they are having problems as you mentioned, it will be resolved.

P.S. I have a Ford 7.3 naturally aspirated International diesel. By todays diesels it is the most underpowered and I do feel it to be anemic, especially when going up to the mountains, but I don't care, when the wheels fall off, I'll go find another used truck to buy. The prices they want for new diesel trucks to me is so absurd be it Ford, Chrysler or GM.

cowboydoc · Oct 5, 2001

Re: GM\'s Duramax Diesel engine

Oh yes that's definitely my point Rat. They all do that. Like bgott pointed out they don't put out their max's because then they have nowhere to go. When Ford came out with the new powerstroke they beat cummins. Then next year Ford went ahead of cummins and back and forth. Was one better than other? Did it mean anything that one had 5 or 15 more hp than the other? No. All I meant was don't get too caught up in the hp #'s. Ford is at 285, I think dodge is right around there now and chevy is at 300 right now. Next year you will see dodge or ford will have the high hp. It's just not a meaningful argument to compare hp between any of them as it is so easy to make one like the other. It's just a marketing game with them. I hope the duramax is hit. Competition is good and it makes the others that much better. Because of Chevy with the 5 speed allison now ford is going to be making a 5 speed auto. Good stuff all the way around and we win by getting better trucks to drive.

With regard to your aspirated truck you would not believe the difference a turbo will make on that truck. Before the powerstroke we put a turbo on all of ours. It was like night and day. You can get one for about $1500 and about $2500 installed. If you've got lower miles on your truck and figure on keeping it awhile I'd definitely do it. You will be pretty happy with it.

JATO_RaT · Oct 5, 2001

Re: GM\'s Duramax Diesel engine

Richard, I would consider it only because my trips up to our place in Tahoe make that diesel smoke. At over 7000 feet altitude, it sucks, or should I say it doesn't suck enough. Banks sent me info and I wrestled with it and perhaps will seriously consider it, but right now though I'm wrestling and having fun doing it by the way with picking a tractor. JD's new series due out later certainly didn't make it any easier. I wish I had some photos and specs on the 4170 if in fact thats what will replace the 4700. Rat...

cowboydoc · Oct 6, 2001

Re: GM\'s Duramax Diesel engine

Rat,
Also look at ATS and Hypermax. We always put in the ATS systems. They were very straight forward. I did so many of them that I could do one in about two or three hours. The last one I did I'm pretty sure we paid $1200 for and that included the pyrometer. If you're mechanically inclined at all they are straight forward. ATS also has a great service dept. and will help you over the phone with any q's on install.

RobertN · Oct 6, 2001

Re: GM\'s Duramax Diesel engine

So, learning to drive fire engines and such, everything has turbo's(cat 3208's), as well as does my new turbo Cummins Dodge.

Years ago, everything was supercharged. What advantage does one hold over the other? A supercharger makes power from an idle to redline/governer, a turbo does not.

What is it about turbo's? Are they cheaper? Superchargers were reliable for a lot of years...

No one has been able to explain why turbo's are "the thing".

RobertN in Shingle Springs Calif

gordon · Oct 6, 2001

Re: GM\'s Duramax Diesel engine

Older Detroits were two stroke and the supercharger was perfect for them. To scavenge the air at all speeds.

Gordon

bgott · Oct 7, 2001

Re: GM\'s Duramax Diesel engine

It takes power to turn a blower. Turbos are using waste gas so it's free boost, not much parasitic loss.

Anonymous Poster · Oct 7, 2001

Re: GM\'s Duramax Diesel engine

<font color=blue> It takes power to turn a blower. Turbos are using waste gas so it's free boost, not >>>much<<< parasitic loss.</font color=blue>

The working word here is not very >>>much<<< parasitic loss. Turbo's are not free of parasitic drag, it is just that they lower the amount of parasitic drag to a "reasonable" level.

Check this site for an excellent short description on turbocharging:

http://gcoast.com/turbo/technical.html

A short quote from the site:
"Without getting bogged down in a lot of detail let's say that conservatively a turbo will only impose about 10-15% of the parasitic loss of an equivalent supercharger."

Turbocharging is more than just slappin a turbo from that burned up tractor onto your Buick, but when you get it right you really do some good.

The Volkswagen TDI (turbo direct injection diesel) springs to mind as a particularly good example of that with 1.9 liters and 90 DIESEL horsepower (which means gobs of torque) and the ability to crack about 50 miles per gallon in a slippery car like a new beetle.

Anonymous Poster · Oct 7, 2001

Re: GM\'s Duramax Diesel engine

oops, blew that link, try this:

http://gcoast.com/turbo/technical.html

cp1969 · Oct 8, 2001

Re: GM\'s Duramax Diesel engine

The two-stroke Detroits HAD to have a supercharger; they wouldn't run without one.

Some models (262, 350, IIRC) had turbochargers in addition to the supercharger.

gordon · Oct 8, 2001

Re: GM\'s Duramax Diesel engine

That is why the superchargers were perfect for them. /w3tcompact/icons/smile.gif

Gordon

JATO_RaT · Oct 9, 2001

Re: GM\'s Duramax Diesel engine

You could always tell the GM 2 strokes, they had a distinctive whine. Rat

RobertN · Oct 9, 2001

Re: GM\'s Duramax Diesel engine

What is it about them that they have to have one? Did the turbo not have enough low rpm output, or not enough boost?

Our Water Tender, WT28 has a 350hp 2-stroke diesel. It definitely has a unique sound compared to the Cummins in my Dodge and the Cat-3208's in our two engines.

RobertN in Shingle Springs Calif

RobertN · Oct 9, 2001

Re: GM\'s Duramax Diesel engine

I found this link, which described things well for me. Now it makes sense.

http://www.howstuffworks.com/diesel-two-stroke.htm

RobertN in Shingle Springs Calif

RobertN · Oct 9, 2001

2-stroke theory

I found a couple cool websites, and now understand why a Supercharger works well with a 2-stroke diesel.

Basically, the 2-stroke has no intake stroke; incoming air has to be forced in.

A chainsaw is different. As the piston comes down, pressure is generated in the crankcase. The piston passes the exhaust port, which blows allows the exhaust to blow out. As the piston continues to the bottom of it's stroke, the intake port is exposed. At that time, the gas/oil mixture which is under pressure in the crankcase is forced into the cylinder. Then the piston comes up again, closing the ports, and goes under compression. Then it fires again.

The 2-stroke diesel needs the blower, because it does not use the crankcase to generate the pressure to force the air into the cylinder. The 2-stroke does not have the "suction" to pull in gas/air, like a 4-stroke, so that air must be forced in.

So, when the intake valves open on the 2-stroke, the air must be blown in. the blower is not just a performance item, it is mandatory for the function of the motor.

For a 4-stroke motor, you do not need a blower or turbo; they are hi-performance items, basically. A normally aspirated diesel works just fine, like our Kubota's and Deere's. On the intake stroke, the "suck" the air in to the cylinder. That turbo just gives it some extra boost.

It still sems though, that a supercharger would give a more linear power band than a turbo, even with it's inherent parasitic losses.

http://www.howstuffworks.com/diesel-two-stroke.htm

RobertN in Shingle Springs Calif

StanInCalif · Oct 9, 2001

Re: 2-stroke theory

Yes, indeed, Robert- a supercharger, esp. the Roots type, as used by Detroit Diesel, adds power throughout the power band, as you say, in a linear fashion- there are no surprises. In contrast, most turbocharged engines have two powerbands, and are at their best when run at a more or less constant speed in the mid and upper ranges of the RPM scale, as in over the road trucks and ag tractors. Here, the efficiency of the turbo is appreciated, as it captures some of the energy wasted in the exhaust. One might say that a supercharger is more effective, whereas a turbo is more efficient.

gmason · Oct 15, 2001

Re: GM\'s Duramax Diesel engine

Well I'm glad to see that this thread has been very well viewed. Thanks to everyone with their feedback and web links. Many of which I had already visited.
I went ahead and took advantage of the 0% financing and last Friday found a 2002 GMC 2500HD Crew Cab (loaded). GM has a great website that you can do your own dealer inventory searches online. I found mine that way about 130miles away.

Now for the real kicker for ya'll, the MSRP on this thing was 43,343. and I was out the door at 36,599. I have a relative that works for EDS and I was eligible for the GMS pricing(2.5% over dealer COST).

I have made a couple of FOrd Super-Duty friends very "green".
The Duramax engine purrs along at 65mph and I can carry on a conversation next to the hood with it running.

This may be a topic for another posting, but I heard from a dealer that said that they've shutdown the plant making the GM HD trucks because a supply problem with the Allision Trans. Seems like Ford is puitting them into their trucks next year and they can't make them fast enough for 2 lines of trucks.
I never saw more than 2 Duramax trucks on any dealer's lots, and most had 0.
I feel like a almost stole this truck for the price I paid and the features.

gary

cowboydoc · Oct 15, 2001

Re: GM\'s Duramax Diesel engine

Glenn,
Congratulations on the purchase of your truck. Glad to see you got such a good deal.

However, Ford won't be putting the Allison into their trucks. Ford manufactures their own transmission and it is true they are going to a new transmission next but it will be built by Ford and not Allison. Again another mfg. raised the bar and the trucks just keep getting better.

Richard · Oct 15, 2001

Re: GM\'s Duramax Diesel engine

>The Duramax engine purrs along at 65mph and I can carry on a conversation next to the hood with it running.<

You must be a VERY fast runner I suppose??

/w3tcompact/icons/wink.gif /w3tcompact/icons/laugh.gif
Richard

patrickg · Oct 15, 2001

Re: GM\'s Duramax Diesel engine

Gary, I have followed the Duramax story since it was a rumor. Except for the lab rat factor I would have no problem getting one. I used to be an early adopter in most tech areas but with time have learned being first with the new shinny ball can have significant downsides. You can always tell the pioneers, they are the ones with arrows protruding from their backsides! If this unit had 4-5 years behind it with a clean record and only modest changes I would say GO FOR IT. If you have BIG $ and don't care, GO FOR IT. Single, good job, need an ego boost, GO FOR IT! If you think a belt AND suspenders is a good idea in certain situations, wait a year or two.

I have a 1997 Dodge turbo diesel 4wd extended cab (pre quad cab) with after market service body. 12 valve Cummins. I went to 4 inch exhaust, Dr. Performance pump and injectors, Gear Vendors aux overdrive. This gives me (not counting 4wd low range) 8 forward speeds and two reverse (automatic tranny with BD low stall speed torque converter). I have a gear for all ocassions, any hill in the interstate system. I have plenty of torque and about 300 HP. I have plenty of power for gross wt plus hill climbs at 11,000 ft plus. I spent a lot of time and money on this truck to make it do about what a Duramax powered truck with Allison tranny does off the show room floor, almost.

I have a list of other stuff like 12,000 pound winch, extreme duty bumper, dual shocks, custom eliptical variable rate coil springs, and on and on that aren't matched from any show room stock GM product (or anywhere else for that matter) B U T for engine and tranny if it weren't for the lab rat effect, I'd vote solidly for the Duramax/Allison.

Oh by the way, I do not shill for Dr. Performance... B U T the claim that they could give me massively increased torque and HP capability AND increase my fuel economy at the same time were true. All I can say is I keep the records and ran the numbers. Same roads, same loads, etc. I get a mile or two more per gallon while pulling the same hills at higher speeds in higher gears. There might be something to the claim that higher injection pressures through finer orifices for shorter periods of times burns more fuel while injecting less fuel through increased combustion efficiency. At first I had high EGT problems and couldn't stay on the throttle as much as I wanted but that was adjusted out, the original instalation was tooooooo rich. Now I'm a happy camper. I would be a richer camper if I had been able to buy the Duramax/Allison instead of having to customize the hell out of the Dodge.

Patrick