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ianb1268

To Much Power?

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This isn't an IHC, but some may find it interesting. I had purchased myself a '94 Dodge Ram 3500, 5.9l Cummins. I wanted to set it up to have a wide, power band, lots of torque, but still able to get excellent mileage.

The game on this is volumetric efficiency. When the piston travels down on the intake stroke, ideally the cylinder would be filled right to the brink with air. Unfortunetly mother nature puts her limitations on us. On naturally aspirated engines, the intake manifold is under atmospheric pressure (14.7 psi up here). As the piston travels downwards, the stagnet air wants to stay stagnet. Time is required to get everything moving, in order to get a cylinder full, so we generally can only run about 1550-1600 rpm to stay efficient. On turbo charged engines the intake manifold is always under positive pressure, this filling of the cylinder occurs a lot faster than naturally aspirated, so we can run at a higher rpm and still stay efficient. Turbo charged engines pull their best at around 1800-1850 rpm. With this cylinder full of air, we want to match an air/fuel ratio, depending on how much load we are pulling, upper explosion limit on diesel is about 100/1, lower explosion limit is around 30/1. Along with this we want an accurate timing. Under load. the rich mixture ignites very easily, so a guy wants to run about 10 degrees advance that way it doesn't ignite to soon, and try to force the piston back down during compression stroke. As I am cruising down the highway under very little load running lean, that lean mixture doesn't want to ignite as easily, so the timing has to be advanced to around 20 degrees.

So this is were I set up my engine. 3 inch exhaust has been installed for better breathing. The Bosche pump and injectors have been pulled, sent off, and calibrated so I get full fuel at 1800 rpm. Lighter governor springs were used for quicker governer respond, but not to light, this would cause surging. I run a 4 speed automatic tranny, overdrive and lock up converter. Problem with factory trannies, is that they shift really smooth. This is accomplished by increasing the amount of slippage of each clutch pack, in return we get more wear and heat. My tranny has a beefed up torque converter with very low stall speed, extra meat on it for the lock up disc on it, I want it locked in as soon as possible to utilize that diesel power. A tranny shop put in extra clutch packs, and increased the oil pressure, to reduce the slippage between each shift. It is more aggressive, but will get a lot better life out of the transmission.

This old thing puts out a lot of torque, I have climbed the mountains of British Columbia, when cruising at 1800 rpm, it never shifts, just stays locked in overdrive, and the engine does all the pulling. And, I get 30 miles to the gallon when driving under normally conditions.

I heard a strange rattle the other day, pulled the tranny, and the flex plate was destroyed. This may be the weakest link in my system. I am going to try another OEM flex plate, if it doesn't stand up, then I will have to see what the aftermarket has to offer.

Sometimes having a lot of power really brings out the weakness in every system, it was probably never meant to see so much torque and hard shifting, but I love it, so I will have to find a solution. :rolleyes:

This isn't an IHC, but some may find it interesting. I had purchased myself a '94 Dodge Ram 3500, 5.9l Cummins. I wanted to set it up to have a wide, power band, lots of torque, but still able to get excellent mileage.

The game on this is volumetric efficiency. When the piston travels down on the intake stroke, ideally the cylinder would be filled right to the brink with air. Unfortunetly mother nature puts her limitations on us. On naturally aspirated engines, the intake manifold is under atmospheric pressure (14.7 psi up here). As the piston travels downwards, the stagnet air wants to stay stagnet. Time is required to get everything moving, in order to get a cylinder full, so we generally can only run about 1550-1600 rpm to stay efficient. On turbo charged engines the intake manifold is always under positive pressure, this filling of the cylinder occurs a lot faster than naturally aspirated, so we can run at a higher rpm and still stay efficient. Turbo charged engines pull their best at around 1800-1850 rpm. With this cylinder full of air, we want to match an air/fuel ratio, depending on how much load we are pulling, upper explosion limit on diesel is about 100/1, lower explosion limit is around 30/1. Along with this we want an accurate timing. Under load. the rich mixture ignites very easily, so a guy wants to run about 10 degrees advance that way it doesn't ignite to soon, and try to force the piston back down during compression stroke. As I am cruising down the highway under very little load running lean, that lean mixture doesn't want to ignite as easily, so the timing has to be advanced to around 20 degrees.

So this is were I set up my engine. 3 inch exhaust has been installed for better breathing. The Bosche pump and injectors have been pulled, sent off, and calibrated so I get full fuel at 1800 rpm. Lighter governor springs were used for quicker governer respond, but not to light, this would cause surging. I run a 4 speed automatic tranny, overdrive and lock up converter. Problem with factory trannies, is that they shift really smooth. This is accomplished by increasing the amount of slippage of each clutch pack, in return we get more wear and heat. My tranny has a beefed up torque converter with very low stall speed, extra meat on it for the lock up disc on it, I want it locked in as soon as possible to utilize that diesel power. A tranny shop put in extra clutch packs, and increased the oil pressure, to reduce the slippage between each shift. It is more aggressive, but will get a lot better life out of the transmission.

This old thing puts out a lot of torque, I have climbed the mountains of British Columbia, when cruising at 1800 rpm, it never shifts, just stays locked in overdrive, and the engine does all the pulling. And, I get 30 miles to the gallon when driving under normally conditions.

I heard a strange rattle the other day, pulled the tranny, and the flex plate was destroyed. This may be the weakest link in my system. I am going to try another OEM flex plate, if it doesn't stand up, then I will have to see what the aftermarket has to offer.

Sometimes having a lot of power really brings out the weakness in every system, it was probably never meant to see so much torque and hard shifting, but I love it, so I will have to find a solution. :rolleyes:

A picture of the eaten flex plate.

post-5914-1158347443_thumb.jpg

post-5914-1158347704_thumb.jpg

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No such thing as too much :D it's just knowing when and how much to use that many seem to have problems with :wacko: and of course a driveline that can take it and a chassis that can apply it.

Funny ian, I've always thought your setup was the truck for me, except I want a stick, and last week I finally got to drive one all day moving cattle pulling a stock trailer and I must say I was really disappointed in the power. Now this may have just been this truck as it didn't seem to have had a lot of attention paid to it in awhile, and the owner certainly hasn't pondered probably any of your points, but I must say Unit #2 with a BBC produced in the height of lowered hp and smog ratings with an auto faired better. :(

I must say your a thinker, not too many people give much thought about whats happening under that hood once the keys released nowadays. :)

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No such thing as too much :D it's just knowing when and how much to use that many seem to have problems with :wacko:

Funny ian, I've always thought your setup was the truck for me, except I want a stick, and last week I finally got to drive one all day moving cattle pulling a stock trailer and I must say I was really disappointed in the power. Now this may have just been this truck as it didn't seem to have had a lot of attention paid to it in awhile, and the owner certainly hasn't pondered probably any of your points, but I must say Unit #2 with a BBC produced in the height of lowered hp and smog ratings with an auto faired better. :(

I must say your a thinker, not too many people give much thought about whats happening under that hood once the keys released nowadays. :)

What year did you try? When it comes to automotive diesels, personally, I like to stick with about 94-99 models. Running the smaller turbos with wastegate valves, the sheer power and response can be staggering. EPA had a real crack down after that, forcing the OEMs to detune to meet emission requirements. Anything before that were real work horses.

If a person likes the laws of physics, there is a life time of study inside of an engine. ^_^

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It was a 94 2500 4x4, standard, reg cab LWB. With the hp wars all the new diesels are in and subsequent poorer mileages the old 12V Cummins and they're great fuel mileage really appealled to me. You've definately shored up the problems the autos had and thats why I would shy away from them, not to mention I haven't recently seen 60K laying around the house. :huh: Maybe it was just this one and I'll have to try some more?

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It was a 94 2500 4x4, standard, reg cab LWB. With the hp wars all the new diesels are in and subsequent poorer mileages the old 12V Cummins and they're great fuel mileage really appealled to me. You've definately shored up the problems the autos had and thats why I would shy away from them, not to mention I haven't recently seen 60K laying around the house. :huh: Maybe it was just this one and I'll have to try some more?

You don't have 60k lying around? I think you tried out a dog. Dodge never really had a good gear ratio on their manual transmissions, other than that, the power was always great, and the mileage, the only problem I have ever run across is on crew trucks. Idling all day and night, Cummins never run very hot, and really slobbered alot when idling for long periods. I have run across Ford 5 ton chasis with 6.9L in them, I am sure mine could power one without a problem.

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ian

Would you mind posting front/back pics with maybe some white paper behind of the damaged area? Inquiring minds want to know. :oB)

mike

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ian

Would you mind posting front/back pics with maybe some white paper behind of the damaged area? Inquiring minds want to know. :oB)

mike

Well Mike, finally got the other picture. My fall tune up doesn't usually include pulling the transmission. Needless to say, its up and running good. :)

post-5914-1158531449_thumb.jpg

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From what I can see the cracks appear to have started some time ago and has taken time to failure? I suspect the replacement was identical-in the cutout area-as the old one. My guess is vibration, either the torque converter or an engine harmonic. Will send a note.

mike

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From what I can see the cracks appear to have started some time ago and has taken time to failure? I suspect the replacement was identical-in the cutout area-as the old one. My guess is vibration, either the torque converter or an engine harmonic. Will send a note.

mike

Thanks for the input. I don't feel any vibration, it is a smooth running machine. I do know a little about the history of the truck, it was used to haul loads not rated for the truck. Maybe this started the problem, and I just finished it off. The new one is identicle, so I don't think it is a normal problem. I am just glad it didn't let loose while driving up a steep grade. :o This is a new one for me, I will have to keep an eye on it, sure makes a person think twice about overloading a truck.

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Overload a pickup truck??? :o:o I've never heard of such a thing......... :P:P

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Coupla things stuck out to me...

What do you mean "running lean"? Most diesels always run with an excess of air since most have no throttle plate, the fuel is metered according to load and speed. An 'excess of air' would be what I consider 'lean'.

And the statement that "Turbo charged engines pull their best at around 1800-1850 rpm" This may be true for your 5.9, but certainly isn't true for other diesel engines, particularly the V8s.

Comments?!?

Thanks.

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Certainly diesels are considered excess air. Lower burning limits of diesel is approximetly 30 parts air to one part fuel. Any richer the fuel will not sustain combustion. On the lean side it is about 100 parts air to one part fuel. Any less, the fuel will not sustain combustion. Between these two points is where you run a loaded engine. That is no secret, it hasn't changed in about 200 years, basic thermodynamics is basic thermodynamics, how you choose to explain it doesn't really matter.

As far as engine rpm, that is also no secret. They were run slow in the 1900's. But as the popularity for horsepower grew, the manufacturers raced to keep up. At the end of almost every manufacturers engine line, the camshaft timing was retarded to squeeze every bit of horsepower out of it until the replacement came out. This brought up the rpms, narrowed the torque range, and was very innefficient. Emissions were of no concern, fuel was inexpensive, rpms ran high, sold a lot of engines. Alot of piston liners on diesels were only attached at the top, lugging them down created liners walking around, and was hard on the bottom end. Take a 444 Cummins and old R12 Mack with dry sleeves, then compare to which will withstand heavy lugging loads. We had both in a fleet I worked in, the old Mack could handle it no problem.

Ask yourself what was the first thing manufacturers did when they started designing formula engines to meet the rising fuel costs and emissions in the 90's. They slowed the engines down, mounted those liners solid into the block and built huge bottom ends.

Design limitations have always been the same, the public, and enviromental protection agencies drive the manufactures a certain way. Unless you believe technology is somehow going backwards, the burning of carbon based fuels efficiently is reaching its limitations. And how we have gotten there has been known for at least a 100 years, it just took computer technology to aid us on the journey.

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Overload a pickup truck??? :o:o I've never heard of such a thing......... :P:P

Yeah, if it fits and moves it can't be overloaded! :rolleyes::rolleyes:

Glenn

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dwight, take a look @ the differance in the torque curve for a v-8 and a I-6. Keep in mind that HP and touque a directly proportional and tied in with RPM. The lower the RPM you make the HP at the higher the tourqe at that level. So if you have to rev a V up to 5000RPM to get 300HP and an I up to 3000 to get 300 HP the I will generate higher torque numbers, I will have to look for the formula I havn't seen it in a while.

Ian, check out http://www.turbodieselregister.com/ if you have not already. That is a group that can get the power out of the engine and to the ground reliably. I have a '97 2500 4x4 5spd and have towed up to 20,000 lbs of payload with it on a trailer and it is still a daily driver. It may not win drag races, generate the most power, or pull the most weight, but the turtle won the race, not the rabbit B)

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Thanks for the website link. I always enjoy some new reading material.

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