I was curious if anyone can tell me approximatly how many rpm's a turbo or super must spin at in order to create a decent amount of boost, say 8 to 10 psi. Any other details you could provide on how they work would be appreciated.

superchargers don't have lag because they are driven by the crankshaft...begin to make power right away. their disadvantage is that they put drag on the engine when you're not "on the gas"...

i believe both turbos and s/cs increase power by increasing the concentration of air in the cylinder.

nitrous, from what i know, makes power differently. it displaces the air in the cylinder. nitrous does not burn hotter or with more power than air, but it does burn much faster...allowing more fuel to be burned in less time = more power.

Turbo/Super chargers are basically air compressors. The more air you can feed your engine, matched with fuel, = more power. The higher you can compress it, the more air molecules make to ignition, and therefore bigger, better boom so to speak.

Think a feasible electric charger could be designed using an alternate powering system then the normal car electrical system?

If you want some free horsepower go to an electric fan. Nitrous is free horsepower and will give you more than either a turbo or supercharger I think, just not for very long depending on your tank size.

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Originally posted by megashawn:
I appreciate your help. What I was actually thinking of back when I posted this was trying to use an electric motor and a separate power system to turn a super charger like device. I've seen similar ideas, but none with gains I was hoping for.

Turbo/Super chargers are basically air compressors. The more air you can feed your engine, matched with fuel, = more power. The higher you can compress it, the more air molecules make to ignition, and therefore bigger, better boom so to speak.

Think a feasible electric charger could be designed using an alternate powering system then the normal car electrical system?

"Waiting for your modern Mesiah to take away all the hatred that darkens the light in your eyes, still I'm waiting on..." - Disturbed

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power is too much as is weight of motor and alternater needed to power the compressor and eltric motors have lag too
turbo is allmost free power and eazyer to mount a intercooler to drop air temps from compression and way lite too
btw no a leaf blower willnot work

smaller turbos spin up faster as do closer to the ext ports ones
twin turbo's will rev up faster than one bigger one will
ideal setup maybe one turbo per cylinder but complex toooo

hotroder and F-1 race fan tooo
and volvo 245turbo driver

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Originally posted by John Myers:
different turbos spin at different rpms, but i believe they're generally around 100,000 rpm. turbos have lag because they work off of exhaust pressure...there's isn't a lot of exhaust pressure at 2000 engine rpm to make any real boost...different turbo designs and sizes do better at making power at different engine speeds.

superchargers don't have lag because they are driven by the crankshaft...begin to make power right away. their disadvantage is that they put drag on the engine when you're not "on the gas"...

i believe both turbos and s/cs increase power by increasing the concentration of air in the cylinder.

nitrous, from what i know, makes power differently. it displaces the air in the cylinder. nitrous does not burn hotter or with more power than air, but it does burn much faster...allowing more fuel to be burned in less time = more power.

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100,000 RPM is a bit fast. (Quite a bit) On even the smallest turbos the tips of the rotors would be supersonic. That is the last thing you want to happen.

You've got the story mixed up on nitrous too. Nitrous makes power because it is an oxygen carrier. When heated in the combustion chamber it releases more oxygen. Extra fuel is required when running nitrous in order to keep the fuel/air ratio correct. You don't just dump in NOX and forget about it. If you did that the engine would lean out in no time and you would have melted pistons and more troubles. The combustion temp DOES go up since the engine is a 'heat engine' and it takes heat to make power. More fuel/air means more heat. Nitrous engines will have forged pistons instead of cast to deal with the extra heat and mechanical abuse that the higher RPMs cause.

and did someone say turbos work off of hot air? Dont be rediculous. It's air movement. You think stagnant hot air is gonna turn that turbine? Do those turbines in dams turn cuz the water is cold? Its physical work of molecules in motion.

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Originally posted by ExtravagantDreams:
Actually 100,000 rpm is quite correct. They may not spin that fast, but ive seen them tested up to 150k.

and did someone say turbos work off of hot air? Dont be rediculous. It's air movement. You think stagnant hot air is gonna turn that turbine? Do those turbines in dams turn cuz the water is cold? Its physical work of molecules in motion.

Ohh and i think I read someone saying lag is due to the air having to travel much farther... Nope.. lag refers to the time until sufficient boost.

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I also researched the turbo speed a little farther and found 100K to be common. I wonder how they keep turbulence under control at speeds like that.

On the subject of twin turbos, they're not always in parallel so to speak... A much less common arrangement, for example on a Subaru Legacy twin turbo, is where the turbos are in sequence, one after the other. The first is a small very light one that spins up quickly which reduces lag, and the second is a larger heavier one that takes longer to spin up but provides good boost later.

And some cars are twin charged - they have a turbo and a supercharger :)

ExtravagantDreams - I'm pretty sure that hot exhaust gasses are important - more heat and pressure means more energy to transfer to the turbine...

ps. Do you actually drive a skyline?

On the hot air thing, I'm pretty sure that the hot exhaust gas is what is used to drive the turbine itself. I don't think it matters if it is hot or not, but it will be hot coming out the exhaust. The key, is to get as cold air as possible into the engine. I believe that is where intercoolers and such come into play.

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Originally posted by megashawn:
Well, Thanks all for the additional info. Skyline-GTR, welcome to the forum, nice nick btw.

ps. Do you actually drive a skyline?

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Nah, I wish! One day...

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On the hot air thing, I'm pretty sure that the hot exhaust gas is what is used to drive the turbine itself. I don't think it matters if it is hot or not, but it will be hot coming out the exhaust.

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Yeah thats true, it's not really going to be an issue in a car since the gasses are always gonna be super hot leaving the engine. But there is a big drop in exhaust gas temperature through the turbine - so that heat's being but to good use somewhere - ie. extra heat energy (and therefore pressure) gets converted to extra kinetic energy in the turbine. Hotter is better...

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The key, is to get as cold air as possible into the engine. I believe that is where intercoolers and such come into play.

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Very true... compressed air coming from the turbo is hot, so the intercooler is essential to reduce the temp and make the air more dense. Even better is a Chargecooler system which spays cold water on to the intercooler for extra cooling...