[silverado]

I've had my 330i (manual, sports) since Saturday and I've driven it very spiritedly (though I haven't yet "floored" it) and I must say that I did not notice this hesitation. Also remember that to completely turn off any possible engine interference that tries to stop skidding, you need to hold the DSC button down for 3 seconds or more until you see the warning triangle in your display. Simply pressing the button once puts the car in DTC mode (dynamic traction control).

[CC 330i]

Originally Posted by silverado

I've had my 330i (manual, sports) since Saturday and I've driven it very spiritedly (though I haven't yet "floored" it) and I must say that I did not notice this hesitation. Also remember that to completely turn off any possible engine interference that tries to stop skidding, you need to hold the DSC button down for 3 seconds or more until you see the warning triangle in your display. Simply pressing the button once puts the car in DTC mode (dynamic traction control).

I have the same car and I haven't noticed this yet either. I have almost 800 miles on my car now, and it pulls fine. I will say that if you keep the accelerator at the same position as the car accelerates, you can feel a big increase in power at about 3500 RPM and then again at 4500 RPM, which I am figuring is the Valvetronic and VANOS becoming more effiicent for that RPM.

I am still leaning toward the automatic transmission or the DBW or traction control causing this difference that some people are obviously experiencing.

[Gnosis]

I've heard that BMW is NOT including the Valvetronic system on the "M" cars simply because it doesn't react fast enough to throttle transients. Let's hope that the on-throttle lag isn't what they were referring to.

Damn it - I didn't think that that could become a potential problem...

I'm an engineer so I understand very well how this system works and how it could affect the engine. And - I hate to break it to you but this *could* be the culprit.

If the responsiveness of the valvetronic system isn't fast enough (I seriously doubt it's as fast a regular dbw butterfly throttle system) when you floor the gas pedal then the valves won't open enough and the engine will be "strangled" for a brief moment. This means that the engine managent won't be able to give it more fuel and you won't get your desired ponies. Not right away at least. Hence the experienced lag.

Let's hope that this isn't the reason because then it won't be an easy fix... let's hope it's either some break in program or a too soft dbw programning that can be fixed with an update...

and yes - get the highest octane fuel you can find. always.

and no - engine cleaning products won't do anything to a new engine (nothing good at least...).

[romeo26]

so would you feel the big increse in power in the 325 at the rpm's that cc 330i posted ??

[Gnosis]

Sure you would! Like he said it's related to the VANOS and valvetronic.

But I don't think it's *primarily* to do with the valvetronic. Because if you floor the pedal the valvetronic adjust the valves to open as much as possible and then it stays there. So any change in engine behaviour after (oh well - let's say a second) you floor the pedal hasen't to do with the valvetronic.

I'd place my bet on the VANOS and general engine characteristics.

Here's more on how an engine behaves at its basics:

Practically every petrol and diesel engine have some point in the rev range at which they are the most effective at turning fuel into power. This is usually where the torque peak is.

Similary all petrol and diesel engines have some point in the rev range where they can transform the most fuel per timeunit. This is usually very close to where the horsepower maximum is.

As the rpm goes up so does the potential horsepower you can get (within limits of course). But this growth of rpm and power isn't always 100% linear (even if that's what BMW strives for - more or less). There will always be sections in the rev range where the engine runs better or worse. Exactly why this is is very complicated and entire engine departments spend years trying to figure out exactly how it works.

But all you need to know is that the engine runs better in some parts of the rev range than others - and it's the way it's suppose to be.

[shipo]

Originally Posted by Gnosis

I'd place my bet on the VANOS and general engine characteristics.

Hmmm, well maybe. I'm also thinking that the acoustics of the intake manifold have a lot to do with it. In the case of the 325i engine, there is a point where the shock waves of the opening and closing intake valves are perfectly in tune (ie. arriving at the valve face just as it is opened to its fullest extent) and the engine develops a noticeable surge. The most dramatic example that I can think of was my business partners’ old 260Z, which he had modified with dual side-draft Webers. That damn thing felt like you were driving a turbo charged car of the early to mid 1980s, between idle and 2,500 rpms that car couldn’t get out of its own way, but above that, YIKES, it damn near broke my neck the first couple of times I drove it simply because I wasn’t expecting the surge.

In the case of the mill in the 330i, which has a three path intake manifold, the surging might could well be less noticeable simply because, in theory at least, the manifold is built in such a way that the shock wave acoustics are optimized across a very broad range of rpms.

Best Regards,
Shipo

[Gnosis]

You are right in everything you're saying. The engine of the 330i is optimized for a very broad powerband. And the intake system is built to work well over the entire rev range - and adjust "the acoustics of the intake manifold" depending to where you are in the rev range.

I kind of included all this in the "general engine characteristics" just to make it simple Maybe it was an oversimplification...

Anyway - that 260Z sounds nice! Really hard tuned normally aspirated engines can be "hairy". Like old normally aspirated rally car engines - nothing, nothing, nothing.... then "BWWWAAAHHHHHHH!!!!!!" and off we goooo!!!!