Yannis

It will and although i haven't been able to confirm this 100% i believe that it will be from next year.

Nikos120i

Next year???

That's a pitty. I guess I'll suit myself with an A3...

I wish it would come out in a few months.

martinbo

Mirage, that's a good question... and I'll answer it in an unscientific layman's fashion becuase I'm too lazy to go and look up the technical details.

The 5 valve head first appeared in Audi products in the mid to late 90's in the A4 1.8 litre engine. If I remember correctly it was a double overhead cam unit with 3 inlet valves and 2 exhaust valves per cylinder. It was subsequently turbocharged with fabulous results ushering in a new era for mass produced turbo engines.

The idea behind multi-valve engines is to maximise control of the volume of air / fuel mixture by utilising the maximum surface area of the cylinder head in the combustion chamber. In multivalve engines, the inlet and exhaust valves require less valve lift (how far a valve opens into the combustion chamber) than a 2 valve head to ingest the same volume of air and fuel. Less valve lift means the valves can open and close faster allowing an engine to perform optimally at high rpm - something that 2 valve single overhead cam engines can't do without severly impacting on the all-round useability of the engine.

5 valve engines were quite in vogue in the late nineties: VW Audi 1.8T, Ferrari V8, Toyota 1.6 RSI, Yamaha R1.

With the adoption of direct injection in the VW FSI engines, the centre inlet valve has been removed as a necessity to make way for the injector that sprays fuel directly onto the head of the piston.

Interestingly, 5 valve engines appear to be out of favour again... both the Yamaha R1 and Ferrari F430 returning to a four valve head.

Mr. M

Just awesome Martin, just awesome... Thanks for your input.

So from what I understand, multi-valve engines improved the efficiency of engines, but direct injection superceded it of late.

Are there any benefits of a 4-valve engine over a 5-valve engine, so much so that the F430 and the Yamaha R1 reverted to a 4-valve configuration? Plus, why don't they just go direct injection?

Sorry for the flurry of questions.

martinbo

Nope, direct injection doesn't supercede multi-valve heads; rather it complements existing multi-valve efficiency. What direct injection does is get a finer mist of fuel closer to the point of ignition. The finer the mist (or level of stratification), the more droplets of fuel you get, the greater the surface area of fuel to be ignited. This gives a much quicker and more efficient combustion process. Very clever advances in Piezo crystal technology now allows for an oscillating crystal to spray the fuel mist in a cone shaped pattern over the piston in multiple bursts per ignition cycle. Amazing. So, the injectors get the fuel into the combustion chamber, the inlet valves introduce the air and the exhaust valves discharge the burnt gasses.

Multi-valve engines are here to stay for the foreseeable future - it's the actuation of those valves that's destined to change significantly over the next few years. Solenoid controlled electronic valve actuation must be on the cards for production cars soon...

4 Valve heads have many advantages over 5 valve heads notwithstanding the aforementioned freeing up of space for the direct injector. The most significant of which is the lessening of complexity and engineering costs associated with the 5 valve head.

Mr. M

Gotcha Martin. You're a walking encyclopedia!