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MetalJim
Dodge Dakota
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1/09/2005
06:31:20
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 Subject: RE: Supercharger or Turbo?
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DOC thats some good info, but I'd just like to clear up some your information about turbos. A better description of a tubo is that the exhaust spins a turbine, which in turn spins the compressor. All turbo systems will utilize a wastegate. The wastegate's purpose is to vent off excess exhaust gas when maximum boost is reached. You see, the turbine will spin uncontrollably without one - which in turn will churn out as much boost as the compressor possibly can. Although more boost is better, it is not always desirable and you really only want to run as much as the engine can handle. I know that if the turbo that I intend to put on my car had no wastegate it would boost to somewhere around 20-25psig...and I really only want to run somewhere around 12 psig max boost(for now) on pump gas or the engine will see detonation. The wastegate has nothing to do with reducing lag. An improperly functioning wastegate can cause lag, but thats a whole different topic.
Also, a turbo-compressor generates no more heat that that of a pulley driven one of the same size. That particular case is proven by Boyle's law. I will say that the turbine section of a turbo will get extremely hot and in turn heat up the engine bay. In practice, poorly designed turbo systems will deliver a "hotter" charge to the intake manifold because of the extreme heat eminating from the turbin and exhaust manifold. If you design the air intake properly(CAI, scoop, etc) and use methods to reduce the exhaust heat within the engine compartment(coatings, shields, etc) you can virtually eliminate any heat transfer to the actual air charge.
And hybrid basically backed up my original point about using a centrifical supercharger, which was it is difficult to change boost levels with them. In case you're wondering about the decrease in boost he is correct - Adding an intercooler will lower the pressure seen at the intake manifold. It is a phenomenon called pressure loss and it is caused by interference with the turbulators inside the intercooler. You can't get something for nothing. An intercooler is an essential component to a properly designed turbo system because of how drastically it increases the density of the air charge, but in order to cool the air it must be directed at the intercooler walls so that the heat exhange can take place. Some intercoolers have less pressure loss at the cost of being less efficient, and some are more efficient at the cost of causing more pressure loss. You guys can do your own research on intercooler efficiencies, the main point is the fact that having one actually allows you to run a higher boost just because it is there. To take advantage of this on a turbo system, you would simply adjust the wastegate to open at a later pressure. One a supercharger you would need to change pulleys to get the boost pressure you want, that is if one is availiable. Which brings me back to my original point - with a turbo you can set the boost pressure to whatever you want very easily.
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hybrid
Dodge Dakota
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1/09/2005
10:59:07
| RE: Supercharger or Turbo?
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ed,
I'm very familiar with turbo's and the effects of tuning and cooler dense air.
I was mainly addressing the issue of pressure loss with a supercharger and intercooler.
All of my work has been with turbo's, making up lost boost is easy, a simple re-route of one hose.
I'm not sure what you mean about "restriction" but yeah cooler more dense air will create more power then a hot charge.
10psi thats 80 degree will make a lot more power then 10psi thats 180 degree's.
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ed
Dodge Dakota
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1/09/2005
11:06:25
| RE: Supercharger or Turbo?
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With the word restriction I mean an engine with the wrong camshaft, to open and close the valves, and heads that don't flow enough air, exhaust is also important to get rid of the forced air the charger is ramming into the engine.
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hybrid
Dodge Dakota
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1/09/2005
15:42:46
| RE: Supercharger or Turbo?
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ED,
Gotcha,
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dt4.7
Dodge Dakota
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1/10/2005
10:46:58
| RE: Supercharger or Turbo?
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Message:
Okay I would like to add more power to my 4.7 through the use of forced induction and dont know if i should get a turbo or supercharger. I know quite a bit about superchargers but from seeing some turbos race at the track and hearing more about them on the web I kind of like the turbo. Does someone make a turbo kit for the 4.7? I know they have complete kits for supercharged systems. If they dont make a turbo kit could you explain what I would need to do to get one. Like what kind what exactly I need and all the good stuff. If I got a turbo Iwould not be able to put it on myself cause I have know idea. I do have experience with superchargers. Thanks for any help.
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hybrid
Dodge Dakota
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1/10/2005
12:35:18
| RE: Supercharger or Turbo?
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Message:
dt4.7,
If your not doing this yourself because of lack of knowhow, I would highly recomend that you either contact someone who can build you a custom turbo set-up or opt for the supercharger.
There is a lot to know before tackling a task such as fabricating a turbo set-up. I got lucky and mine was was piece of cake (both that I did on my car). I've also done several of them for friends.
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