The NextGen speculation thread
 

According to http://www.mazda.com/publicity/relea...3/070322a.html we will have to wait a while for the new rotary. This is the bit on rotaries: "Rotary engines- Introduce a new generation gasoline rotary engine with enhanced power and fuel efficiency toward the start of the decade beginning in 2010. "

So how are they going to do it? Can you improve both power and fuel efficiency with FI, or is that simply oxymoronic? Or would they go to some kind of common rail technology? Note elsewhere in this statement they intend to "Introduce Mazda’s independently developed Smart Idling Stop System (SISS) in the Japanese market in 2009." Could this be adapted to a rotary, and improve the poor heavy traffic fuel consumption?

Now, altogether, "2, 4, 6, 8, we just wanna spec-u-late"

I'm not sure i'd enjoy the SISS in a sports car. If you have a nice exhaust, you'll miss that idle at the red light or right when you pull into a shopping place or gas station. Now in standard vehicles sure, just like a golf cart, press the gas and away you go.

petrol engines have had a common rail for ages so it's not going to help much. common rail

Petrol and Diesel Piston engines have had common rail for ages yes, but have Mazda been using it?

The only mention I can see of Mazda using common rail is in their latest and concept diesel cars.

I would love to see the mazda research into things like different rotor dimensions and the effects on things like torque, HP, fuel efficiency, etc, just for the curiosity.

there must be some subtle difference in diesel 'common rail' technology that separates it from the single fuel delivery rail most petrol cars use.

What makes you say that?

quote from link above "In the Common Rail accumulator injection system, the generation of the injection pressure is separate from the injection itself. A high-pressure pump generates in an accumulator – the rail – a pressure of up to 1,600 bar (determined by the injection pressure setting in the engine control unit), independently of the engine speed and the quantity of fuel injected."

apart from the high pressures, we have always had a common rail, with pressure independent of engine speed. the amount of fuel injected depends on the injectors valving and pressure, but the amount of fuel is ultimately controlled by the engine computer. the reason the rx-8 can run a return less fuel system is that pressure is controlled by the fuel pump via the computer.

I think "Common Rail" is just Boschs patented name.

What I dont get is why a returnless system is so good. If better economy can be had by increasing the rail pressure without power loss, then surely sacrificing the returnless system (whatever its benefits) is worth it.

a return-less system saves money. I think it also doesn't heat the fuel as much?

in theory you could vary fuel pressure to any rpm/pressure you wanted with a return-less system. in the old systems rail pressure was indexed off manifold pressure or vacuum so the pressure drop across the injector remained constant under boost or vacuum.