GM's Duramax Diesel engine
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JATO_RaT
Veteran Member
Re: GM\'s Duramax Diesel engine
You could always tell the GM 2 strokes, they had a distinctive whine. Rat
You could always tell the GM 2 strokes, they had a distinctive whine. Rat
RobertN
Super Member
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
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
Super Member
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
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
Super Member
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
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
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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.
<font color=green>stan</font color=green>
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.
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
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
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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.
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
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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
>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
Veteran Member
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
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