Quote:
Originally Posted by Boss330
The S55 doesn't even have a single throttle body... 
Valvetronic takes care of the TB business on modern BMW engines. So, in effect every BMW engine with Valvetronic has what equals ITB, since air flow to each cylinder is controlled by the valve lift on each cylinder.
In fact, probably better than ITB since the intake valves only allow air flow when air flow is needed. On a ITB setup the TB is still open even though the cylinder is not drawing air in (like on the combustion or exhaust stroke). |
I am not sure this is an advantage of Valvetronic... What would be the negative effect of having the TB open when the intake valves are closed
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IMO, a big benefit of dispensing with the throttle bodies is a significant reduction of pumping losses, especially at smaller throttle openings. IIRC, earlier versions of Valvetronic were not deemed "fast enough" for applications in ///M engines (S85 and S65). This is why they retained the individual throttle bodies. With the advancement of the technology, Valvetronic was first applied on an ///M engine with the S63.
Quote:
Originally Posted by Boss330
And some DI engines today don't even have a throttle at all, they run like a diesel (but with a spark plug obviously) with only the amount of fuel injected regulating the power output.
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I did not know this. If it is possible, that would be pretty cool and a very good brakethrough. I always thought that gasoline requires a (near) stoichiometric mix to ignite. I guess they found a way to create the proper mix just around the spark plug for it to work.
Any references to such an engine? I would be interested to read about it.