Jeff,s apex front mount hp #,s from dynotech!

[hlmrx1]

Can anyone explain that in simple terms?

Compressing air creates heat see Boyle's Gas Law or Adiabatic Efficiency
(compressor pressure, charge density, combustion chamber ratio/design)

Gasoline’s autoignition temperature is approximately 495*F
(Terms used: pre-ignition, detonation, autoignition)

The more efficient your compressor/intercooler the lower your intake charge temps
(adiabatic efficiency and aftercooling)

The lower the intake charge temperature the lower the octane requirement will be
(less likely to ignite before the spark plug initiates combustion)

I thought that SC's had less heat than TC's therefore they would run cooler thus run more efficiently, no?

 

[lakercr]

Can anyone explain that in simple terms?

Compressing air creates heat see Boyle's Gas Law or Adiabatic Efficiency
(compressor pressure, charge density, combustion chamber ratio/design)

Gasoline’s autoignition temperature is approximately 495*F
(Terms used: pre-ignition, detonation, autoignition)

The more efficient your compressor/intercooler the lower your intake charge temps
(adiabatic efficiency and aftercooling)

The lower the intake charge temperature the lower the octane requirement will be
(less likely to ignite before the spark plug initiates combustion)

I thought that SC's had less heat than TC's therefore they would run cooler thus run more efficiently, no?

Don, the heat on a turbo is on the exhaust side, and the heat is part of what makes the turbo work. On any internal combustion engine, about 1/3 of the energy produced goes into turning the crank. Another 1/3 is absorbed into your cooling system, and the other 1/3 goes directly out the tail pipe. It is the last 1/3 that you care about with a turbo. The thermal energy created by combustion, as well as the kinetic energy of the exhaust gasses working against the turbine wheel are what drives the compressor. Heat on the turbine side you want, heat on the compressor side you do not.

It is a simple law of thermodynamics that when you compress a gas, you also raise it's temperature. Therefore, both a SC and a turbo will raise the temperature of your intake charge. The amount the temperature is raised is dictated by a number of parameters (next time you're in the shop I'll show you how to read a compressor map). Bottom line is that there is a sweet spot for every compressor, and that is the range you want to run it in for optimum performance with reliability. A simple analogy would be to walk over to your stereo and turn it up as loud as you can without distorting the sound. Your volume knob is probably somewhere between the 12-1:00 position. Turn the knob the rest of the way around and it makes more noise, but it isn't pleasant, and you'll very quickly blow a speaker. Same thing with a turbo/SC. Drive them outside of their efficiency range and you start putting massive amounts of heat into your intake. You boost gauge might read higher (just like the stereo might sound louder) but the performance is going in the wrong dirrection.

So assume that the turbo and SC are both flowing similar CFM at comparable efficiency ratings. The intake temp as it reaches the intercooler should be similar. Now we have to look at intercooler efficiency. The ideal intercooler would show no pressure drop from the inlet to the discharge side. That isn't physically possible, but the goal is to keep this drop as small as possible. The surface area of the IC that is exposed to ambient air is also very important. Count the number of individual tubes that make up the IC core (I know the CPR IC has 17, not sure about the SC offerings). More tubes increases the surface area available for heat exchange, and helps to keep the pressure drop minimized. You can build an IC with less tubes and maintain a similar pressure differential, but you would have to make the core thicker to do it. A thicker core with less individual tubes (and the same internal volume) will be less efficient than an IC with a thinner core having a greater number of tubes.

Now go back and re-read what Hammer wrote about efficiency, intake temps and octane.

 

[HAMMER]

The compressor section (scroll & impeller) on the Rotrex supercharger is identical to that of a turbocharger. So the heat generated from the compression of air would be identical if they were the same size. In the case of this thread the Rotrex C15-16 is smaller and less efficient at compressing air, which creates heat, than CPRs GT-series turbocharger in the higher CFM ranges.

The drive side temperatures of the Rotrex supercharger ranges from 120 to 140*F at high load. The drive side of a turbocharger runs up to 1100-1200*F at high load. Some of that heat is transferred mechanically through direct contact with the compressor side (scroll & impeller) and some is transferred to the compressor side (scroll & impeller) through trapped and radiated heat.

That is why I stated earlier in this thread, even though these are not the same size compressors, I would have liked to see a comparison of the temperature differences: Ambient vs Scroll Discharge vs Intake Manifolds.

The parasitic draw of the Rotrex superchargers is VERY low at low rpm and increases as pressure/rpms increase. Relieve that pressure with a Bypass-Valve and the parasitic draw is again VERY low.

The Rotrex compressors used in our application:
C15-60 (wt 6.4 lbs) parasitic draw at max pressure approximately 12hp.
C30-74 (wt 11.2 lbs) parasitic draw at max pressure approximately 24hp.

To add-on to lakercr’s intercooler information see this link:
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Bell Intercooler FACTS PAGE: http://www.bellintercoolers.com/pages/t ... html#FAQ_1
----------

 

[BlueByYou2000]

Ive got about 400 miles on my CPR Apex and all I can say is WOW. This thing is just nuts. I thought my 03 RX1 Turbo was fast. Unreal power and toying with other sleds has never been more fun. I couldnt be happier.