[TurboS10]

I know of people running HX50's on 2.2 liter race cars with little issues of lag. That turbo is large enough for a big V8. The key is what I mentioned before with the ALS. By retarding timing and dumping raw fuel in the exhaust the exhaust heat and pressure can be greatly increased in drag cars. In rally cars a similiar technique is used between shifts to reduce spool time.

Another strategy is to us a hybred turbo with a very small turbine and a large compressor. Then a large wastegate is used to bypass the extra air that would cause the turbine to become a restriction.

As for the 8 turbo engine, the turbos all produce the same boost. Probably around 15 psi considering what they are using.

Chris

[Nightfire]

and then of course, there is this link http://fasttrackperformance.com/page.../ChrisTTGN.wmv wich will make you wanna have a turbo BADLY!!!








Mike

[87442lover]

Supercharger

Both charger units use power to make power, but a supercharger will give you that low-end power you need + the high end and wont leave you with tons of backpressure in the exhaust.

[TurboS10]

No, turbos do not use power to make power. They use spent heat energy in the exhaust to drive a turbine instead of just letting the heat out of the exhaust. While there is some pumping loss on the engine it is minimal if the turbine is properly sized. Do some reading on thermodynamics.......

Chris

[paperairplane]

I went supercharger. In the forced induction world, what's cooler than a big blower? Mad Max would probably never made a dime if that car had a turbo under the hood.....


Also, just b/c you have a supercharged engine doens't mean you have to chop a huge hole in the hood - look at the new Buick Ultra's, it's a supercharged grandpa ride. (which is only a change of pulleys away from making a nice sleeper...)

[k2mooch]

Originally posted by TurboS10
No, turbos do not use power to make power. They use spent heat energy in the exhaust to drive a turbine instead of just letting the heat out of the exhaust. While there is some pumping loss on the engine it is minimal if the turbine is properly sized. Do some reading on thermodynamics.......

Chris

Chris, not saying you're wrong because I know that you know what you're doing, I just need a bit of clarification on something.

I was under the impression that turbos work on the 'flow' of exhaust gasses to 'rotate' the turbine, not just the presence of heat. This is where the pumping loss comes from because a normally free-flowing exhaust is now restricted and disrupted by a turbine.

Just want to be sure that this is correct, because this information leads me to understand what happens when 'lag' occurs. It's when the engine is revved and has to wait to produce the 'flow' of exhaust to be able to turn the turbine to produce boost to feed back to the intake to increase performance. The fact that the turbo depends on exhaust causes lag, not heat.

I'm not 'saying' this is what really happens, and I'm not 'saying' I'm right and you're wrong. I'm saying this is the first time I've heard something other than what I was told and understand to be true by someone ('you') who is probably more credible than whoever I heard it from. In fact, I'm asking you because I really don't know anyone else who know's their ***** like you do when it comes to turbos. hehehehe.

I'm waiting for a response before I vote because this is pretty much the biggest determining factor for me.




RESPECTIVELY CONFUSED


MoocH

[TurboS10]

I am not thermo guru by any stretch of the imagination.

The best way that I can explain it is that there is a certain amount of energy that is needed to drive the turbine fast enough to make boost. That energy is extracted from the exhaust gas. This energy is in the form of heat and pressure and is expressed as enthalpy(I think), or total energy of the media.

The In an NA application exhaust pressure is minimized to increase flow and decrease the pumping loss to the engine that is needed to expell the exhaust gas. In a turbo engine the exhaust gas is restricted to increase velocity pressure and temperature. This causes a build up of energy before the turbine. As the gas travels through the turbine to reach the lower pressure/lower heat side of the turbine it gives up a portion of the energy to turn the turbine.

When I say that there are pumping losses this is where this comes in. Basically a turbo engine sees about the same power loss as any engine would see with a restrictive exhaust system. I guess you could say that it robs power from the engine, but it is different from a belt/gear driven blower that automatically takes ~10% of the power generated to turn it.......in my mind at least.

Maybe I am just dead wrong.....like I say, I am no expert.

Chris

[Robinson Robin]

Although turbo's do create some restriction in the exhaust which does take power it is no where near the power waisted drawing energy directly off the crank in a supercharged application. I used to vote for s/c but the more I learn about turbo's the more I become convinced that they are Superior

[87442lover]

Originally posted by TurboS10
No, turbos do not use power to make power. They use spent heat energy in the exhaust to drive a turbine instead of just letting the heat out of the exhaust. While there is some pumping loss on the engine it is minimal if the turbine is properly sized. Do some reading on thermodynamics.......

Chris

actually they cost the engine some HP as with superchargers.

The reason?

They create back pressure in the exhaust runners and headers and force the engine to work harder everytime those exhaust valves are opened. They cause more heat and restrict the exhaust flow leaving the car almost totaly useless under 3000 RPM, or when there is no boost(or too little) to compensate for the extra work the engine has to do.

Basicly, when the exhaust valve opens, that exhaust gas in the exhaust system before the turbo pushes against the gas trying to get out of the engine making the engine lose a bit of power first, and then as the piston is still rising the engine now has to force that gas through a small turbine thats causing the restriction and hampering performance. Yes turbos might use less power to make power, but they still USE power.

There is no "free" power added out there, that is nothing that can make power without taking it first. Well... you can count NO2, but the cost of that is in engine wear.

And turbos do not "use" heat, they help create it by restriction and pressure of the exhaust gasses. Heat is a turbos enemy as with any engine part. Back pressure is a turbos friend. I know enough on "thermodynamics" thank you.

[70nova]

My vote would have to go to the centrifugal supercharger. Like a turbo, centrifugal superchargers can be installed underhood and are capable of running a TON of boost, but the supercharger does not require the custom exhaust that the turbo does.

[TurboS10]

Originally posted by 87442lover
actually they cost the engine some HP as with superchargers.

The reason?

They create back pressure in the exhaust runners and headers and force the engine to work harder everytime those exhaust valves are opened. They cause more heat and restrict the exhaust flow leaving the car almost totaly useless under 3000 RPM, or when there is no boost(or too little) to compensate for the extra work the engine has to do.

NO! A properly built turbo exhaust is designed to maximize velocity by using slightly smaller pipe than would be used on an NA engine of the same power output. When the engine is not making boost in the low RPM the increased velocity is a good thing. If there is not enough flow to cause pressure ot build in the exhaust then the system is not robbing any power to speak of.

Originally posted by 87442lover


And turbos do not "use" heat, they help create it by restriction and pressure of the exhaust gasses. Heat is a turbos enemy as with any engine part. Back pressure is a turbos friend. I know enough on "thermodynamics" thank you.

And wrong again.

Perhaps you can explain why EGT will drop ~200 oF as it passes through the turbine housing. The turbine does use heat or more specifically heat transfer. Heat is energy and the turbine extracts energy from the exhaust gas to do work.

Do some reading on ALS and you will find proof of this. By using electronic control of fuel and timing, exhaust heat can be increased at a give RPM to spool the turbo. It is used on rally cars between shifts and on drag cars to spool the turbo on the line when the engine is not loaded and not moving much air. This works because the added heat increases the energy in the exhaust available to do work.

Chris

[willys36@aol.com]

End of story!

[87442lover]

lol turbo, your so wrong its making me laugh, but you can believe what you want to believe.

Willys 36 has got the right idea

And heat is not energy(or at least not that can be used by a turbo ) heat is on of the "by-products" and is not a good thing.

Basicly the way you got it worded is if I take a lighter and sit there and heat the turbo it will make boost, even with the engine off, lol, god you can be funny sometimes.

[TurboS10]

lover,

To say heat is not energy really shows that you have no concept of thermodynamics or basic physics for that matter. It does not make me much difference if you think I am wrong.....you have proven yourself uneducated. Bet it would blow your mind if I told you that heat energy is what makes an engine run, but that is neither here nor there since you dont understand.

Here is the first thing that popped up on google: http://www.powermasters.com/heat_energy.html

Do some reading.

Chris

[willys36@aol.com]

I'm afraid Turbo speaks with straight tongue! Temperature is the enemy of parts of any machine including a turbo but only because of the limitations of the materials used to build it. From a thermodynamic perspective, the higher the temperature the better for process efficiency and power extraction. It is the DIFFERENCE in temperature (potential energy if you remember your science classes - the same as bolder sitting on top of a hill) from which energy is extracted to do useful work. Just like a jet engine in an aircraft, heat is extracted from the exhaust stream through a turbine and converted to energy. That is why the temperature drops - heat is converted to work. The more heat converted to work in a given process, the more efficient it is. The ultimate would be to extract all of the potential energy which would reduce the exhaust temperature to ambient, but then we would have invented a perpetual motion machine and would own the world!