Electric turbocharger - Oh BOY!

The downside of TurboCharging.....or even traditional SuperCharging.

In order to take advantage of boost, intercooled boost, the base/engine compression ratio must be reduced from that that would be optimal for simple cruise. The more INTERCOOLED precompressed BOOST that can be used, made available, the lower the base compression ratio must be so as to not terminate the engine with FULL boost.

That's why the Mazda CX-7, Acura RDX, and Ford's entire EcoBoost engine group have such relatively poor hwy FE. All of these engines make use of DFI which would typically allow a CR of 12:1. But instead in order to accommodate BOOST mode the engine must run in detuned/derated mode 98% of the time.

That's the advantage of an SC that can be switched on and off, or in the case I have described, an SC that can be widely modified in performance. Add the new Toyota e/VVT-i capability to also switch engine modes and you have a SuperCharged engine with STELLAR FE.

So the answer is...Modify the engine compression ratio "on the fly".

 

There are two forms of wasted energy in the ICE exhaust system. The waste heat is one and this thread has focused on it. The other is exhaust back pressure which is inherent in both the catalytic converter and the muffler (exhaust flow volume times back pressure = wasted power).

The back pressure in the catalytic is not something that can be eliminated due to laws against modification (BMW uses a low back pressure catalytic), but there is something that can be done about the muffler. Take a look at my papers on "Active Noise Cancellation".
Quieting The Environment: Noise Cancellation (General tutorial paper)
Quieting The Environment: Noise Cancellation ( Discussion relating to "off road" Machines)
"Noise Cancellation Systems," Chapter 34 in Automotive Electronics Handbook, 2nd Edition, ISBN 0-07-034453-1, McGraw-Hill, (January 1999).

There is an opportunity to salvage 2-5% MPG (and up to 10% peak HP, 5-7 hp in our Prii) with this technology.

JeffD

 

Interesting topic.

Willie Willford put a turbo in his 2000 Insight and increased his hp from 70 to around 105.

Installing a electric turbo would be easier, however there are "hairdryer" kits to be avoided.

If you get a quality electric turbo kit, the issue is the draw on the batteries.

 

Hi Jeff,

Very Interesting! I am currious as to the pressure transmission effects due to the active muffler? So, does the active mufler represent a short, or an open to the pressure waves coming down the pipe? Or does it present a lossy element, and if so, is that loss resulting in electricity that can be sent to a battery? Can the impedance actually be controlled? This might actually be used to do three things at the same time, ram tune the pressure at the exhaust valve, silence the exhaust, and generate electricity...

 

When tuning for minimal sound , the system acts as a short circuit at the end of the exhaust pipe and reflects the pressure wave back towards the ICE.

The loss is in the passive element (a glass pack, straight through muffler) and the reflections are absorbed as they bounce back and forth between the ICE and the "mirror" at the tailpipe.

yes, but then the exhaust "note" will come out. If you adjust the exhaust pipe and manifold length so that at cruising speed you get the desired effect at the exhaust valves.

You do have to use about 25 watts of electrical energy at peak HP ICE output to generate the "AntiNoise", but this is about 1/25 of a horsepower vs the 50-75 HP that the ICE is generating at that time.

JeffD

 

Thinking about this, I guess the active mufler is a short to the pressue waves. As its launches a pressure wave back up the pipe out of phase with the pressure wave coming down the pipe.

OK, we must be in sync. You answered as I typed the above.

Comment - why not put the glass pack (passive element) on the outflow side of the active muffler, and put a generator (piezoelectric, thermo electric, moving coil) on the inflow side to generate the power you need for this device?

Also, one could cut up into the rear bumper gaurd, and put ia cone exhaust. Because, withthe pressure waves strpped off the flow, the megaphone effect would not be an issue, and then the flow could generate better thrust? Or am I all wet on that one?

 

You need the passive element in the loop to help stabilize the feedback control system. The system models the noise as well as the acoustic path from the speaker system input back to the digital input to the algorithm.

The "removal" of the pressure wave requires that:

• The antinoise and the noise propagate in tandem from the end of the exhaust pipe.
• The residual microphone can hear the results of the cancellation so that the controller can work it's magic.

So the "cone" must not get in the way of the overall system operation. I can't speak to the damp thrust question as my Prius is not a jet propelled vehicle.

JeffD

 

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Not quite a chcken/egg. I agree that if you remove all of the heat from the exhaust, the exhaust volume will be greatly reduced thereby reducing the back pressure. The other factor is the flow constriction in the muffler which is what the Active Noise Cancellation system reduces.

JeffD

 

Ignoring heat and focusing on backpressure and air displacement (output), wouldn't something like a dam's turbine (like a mini wind farm inside the muffler) work to recapture energy at little risk? Perhaps this is what people are already saying here, I'm a tad technically inept

 

Sorry to disillusion you but the active noise cancellation DOES NOT, of itself, reduce/affect the back pressure. The anti-noise system simply enlarges the effective volume of the muffler incrementally as the pressure wave arrives and then decreases the volume...basically AVERAGING the flow and thereby eliminating the NOISE.

Think of it as a hydraulic pump accumulator system, or even a filtering capacitor in a full-wave rectified DC power supply.

The anti-noise muffler, like the capacitor or accummulator, simply serves to "smooth", average, the flow and thereby eliminate the pulses/noise.

 

However, an active system can potentially replace a much more restrictive passive system. Both active and passive muffler systems work like the filter capacitor in your example, and both need to service the same average flow. The difference is that the active system can provide a lower series resistance.

Tom

 

If only I could get past their web master's lack of tools ... like grammar check.

 

Agreed.