nt

30 valves (5 valves per cylinder) vice 24 valves (4 valves per cylinder)?
V6 (Audi) vice Straight (aka inline) 6 (BMW)?
The difference in power output?
There are many other differences too, please be more specific.

Regards,
Rodney

'99 A4 1.8tqms

nt

internal combustion engines first had 2 valves per cylinder, or at least that's as much as my knowledge goes back. One intake valve to allow fuel/air to enter the cylinder and one exhaust valve to allow exit of the exhaust gases. As time went on, we began to add valves.. 3valves per and 4 valves per cylinder. On the three valve config, the extra valve is another intake valve. This allows the mixture to be more even and thoroughly pushed into the combustion chamber. This is also the reason for "angle valve jobs".. this allows the mixture to flow more evenly, I believe. I think the mission is to have the mixture be completely consistent in terms of vaporization, and to have the mixture be evenly distributed throughout the chamber. The fuel burns faster and more completely, I believe. The 4 valve is set up as 2 intakes and 2 exhausts. Faster in, faster out. Now Audi has 5 valves... 3 small intakes and 2 small exhausts. Better apparently. I am no engineer, this is just my experience. There is probably much more to the story, but this is the fundamental idea, I believe. Too long?
Conker '00 S4

Three intake valves can cover a larger area than two larger valves of the same total area, thus increasing the amount of fuel mixture reaching the cylinder for firing. Only two exhaust valves are used as the force of the firing helps to force out the exploded mixture.

Frank

driven the A4 2.8 so can't help you there. The BMW engines are about as good as they come as far as smoothness, power, etc.

It does help to improve combustion by limiting air intake at low RPM to increase air velocity and induce tumbling which aids in better fuel air mixture, at higher RPM it allows for more air flow. People also state it allows for central placement of the spark plug, which is considered optimal. However, many if not most 4 valve cylinders have the same placement.

These same issues are addressed in other ways by BMW. The extra valve does affect engine performance but it has been blown out of proportion by marketing folks as it is a noticeable diference whereby people can scream our engine is higher tech than yours.

Hugh
1.8Tqms Avant APR'd Borla'd

BMW engine is better - smoother and more torque. Also, BMW makes the best handling sport sedans in the world. I have driven and owned several BMWs over the years. Handling wise I would rank BMW, Audi, MB in that order.

Audi has quattro and a much better price here in the US. Howvever if you look at sales in Europe where the price is similar - I belive Audi is outselling BMW. Hence in my belief Audis are a bargin here.

Reggie

98.5 30vQMS

Check out the article about 5 valve technology in the engine FAQ and also, the link below to Audi's explanation of its advantages.

Regards,
Rodney

'99 A4 1.8tqms<ul><li><a href="http://www.audiusa.com/passion/technology/e_valve.html">Audi of America 5 valve info page</a></li></ul>

I have the 2.8 and it is very smooth...except for a little vibration at idle; 1,000 miles.

I like the on the road handling of the quattro better than the BMW I tested. The A4 has a great combination of straight line stability AND agility. Also, in the wet I'll take the quattro over the BMW. The BMW is also a great car and some people prefer its handling at the limit where you can wag the tail with rear wheel drive.
However, Consumer Reports rated the quattro better in emergency handling than the BMW.

Frank