Why not go with valvetronic v. individual TB

[5erman]

So you always hear how "instant" of a response you get on an M car with individual TB due to less pumping losses and the air being practically "knocking on the door of the throttle body" right near the valve to get in there instead of having to travel way from the start of the single TB like in a traditional car.

I have had the pleasure of owning the n52 valvetronic I6 engine with no active throttle body and it simply uses valve lift to control air into the cylinder. Response is INSTANT and I cannot see it being any better eith individiual throttle bodies in the MD. I think valvetronic is the newer and better technology for instant response and reduction of pumping lossess.

It makes sense to since there is not throttle plate to have to open at all-the air is always "on tap" sitting right at the valve waiting to be sucked in instantly, not waiting for the throttle plate to open and let it in.

Do guys who have driven both a valvetronic engine and M engine agree that the valvetronic has instant throttle action more so than the M? (not talking vanos here guys) The N52 is the only I6 to have valvetronic as well as the more recent v8's in the 545 and 550 e60s.

I think they will definetly go this road for the next M-Can someone think of any additional benefit of individual TB that I am missing. I think valvetronic is one of the best technologies in decades to make a dent in throttle response and smoothness.

[mkoesel]

Originally Posted by 5erman

The N52 is the only I6 to have valvetronic as well as the more recent v8's in the 545 and 550 e60s.

The N55 also has Valvetronic. And, FWIW, the N62 V8 is dead now (not incl. Morgan and Wiesmann, who will switch to the N63 soon also). The new N63 turbocharged V8 doesn't have Valvetronic, but it's pretty likely that its successor will.

I think they will definetly go this road for the next M...

I won't say definitely yet, but I would give it a real good chance, especially since the engine will probably share basic architecture with the N55.

[5erman]

I was just looking more for any reason ata ll that ITB has ANY advantage? I just think it is old technology that allowed almost what valvetrtonic allows onlynot as good but valvetronic has better throttle response and less pumping losses-the 2 factors why m division uses ind. throttle bodies.

would also help fuel savings too that they so desperately want by further reducing pumping loss

[gr8000]

Valvtronic as a system is not fast enough in actuating valves in high-reving applications. The end result as compared to ITBs is similar (if not identical) for engine speeds of up to 7,000rpm, but beyond that there are system limitations.

[adc]

Originally Posted by 5erman

I have had the pleasure of owning the n52 valvetronic I6 engine with no active throttle body and it simply uses valve lift to control air into the cylinder. Response is INSTANT and I cannot see it being any better eith individiual throttle bodies in the MD. (...) Do guys who have driven both a valvetronic engine and M engine agree that the valvetronic has instant throttle action more so than the M?

I am currently driving a 328i vert loaner and I can tell you that the M3 has better throttle response.

I don't know if it has to do with the throttle mapping or not - don't forget that both systems have a computer between the gas pedal and the actual system - but it's just better in the M (in normal mode).

I think it simply has to be below a certain number of msec, with anything below that threshold being experienced as "instant" by the driver's brain.


But - go ahead and try an M3, see how you like the throttle response.

[GregW / Oregon]

Originally Posted by gr8000

Valvtronic as a system is not fast enough in actuating valves in high-reving applications. The end result as compared to ITBs is similar (if not identical) for engine speeds of up to 7,000rpm, but beyond that there are system limitations.

Correct.

"Valvetronic is actually less efficient at high rev than conventional engines, let alone VTEC. ...the camshaft drives the long intermediate rocker arms, in turn drive finger followers, this generates quite a lot of friction. Therefore the efficiency and refinement of Valvetronic engines drop rapidly at over 6,000 rpm. No wonder in the foreseeing future BMW will not equip its M-power engines with Valvetronic." --Autozine

http://www.autozine.org/technical_sc...ne/petrol2.htm

[mkoesel]

"Valvetronic is actually less efficient at high rev than conventional engines, let alone VTEC. ...the camshaft drives the long intermediate rocker arms, in turn drive finger followers, this generates quite a lot of friction. Therefore the efficiency and refinement of Valvetronic engines drop rapidly at over 6,000 rpm. No wonder in the foreseeing future BMW will not allow its M-power engines to rev above 7000 rpm." --Autozine

Just fixing that part of the quote for them.

[Pete_vB]

Originally Posted by 5erman

Can someone think of any additional benefit of individual TB that I am missing.

Yes, a few...

Valvetronic uses a stepper motor to actuate, and it takes some time. In the original version this was 300 ms (.3 seconds) to go from full closed to full open. This is a long time- about as long as a shift in a manual trans takes, and remember you close the throttle, shift, then open the throttle again in that time in a shift. So the original valavetronic was much slower response than ITBs; they have since improved, but I haven't seen times quoted.

The second issue is related to the "friction" mentioned above. The issue with friction isn't a direct one; it's not as if the extra 60 hp between an ITB S54 motor and an N52 is being absorbed in friction at the cam.
Instead the higher friction of the Valvetronic design would be magnified with stiffer valve springs, and stiffer valve springs are what's needed to run a more aggressive cam and/ or higher rpm. So valvetronic is limited to less aggressive cams and lower peak RPM- a serious drawback.

Of course BMW is working on both issues, and if they can remove them then as you suggest valvetronic should be as good or better than ITBs. Currently, however, ITBs hold a significant advantage, especially for normally aspirated for M applications.

[C ///M]

Originally Posted by Pete_vB

Yes, a few...

Valvetronic uses a stepper motor to actuate, and it takes some time. In the original version this was 300 ms (.3 seconds) to go from full closed to full open. This is a long time- about as long as a shift in a manual trans takes, and remember you close the throttle, shift, then open the throttle again in that time in a shift. So the original valavetronic was much slower response than ITBs; they have since improved, but I haven't seen times quoted.

The second issue is related to the "friction" mentioned above. The issue with friction isn't a direct one; it's not as if the extra 60 hp between an ITB S54 motor and an N52 is being absorbed in friction at the cam.
Instead the higher friction of the Valvetronic design would be magnified with stiffer valve springs, and stiffer valve springs are what's needed to run a more aggressive cam and/ or higher rpm. So valvetronic is limited to less aggressive cams and lower peak RPM- a serious drawback.

Of course BMW is working on both issues, and if they can remove them then as you suggest valvetronic should be as good or better than ITBs. Currently, however, ITBs hold a significant advantage, especially for normally aspirated for M applications.

QFT. Definitely curious to see which way things go. I used to think that M cars would always be NA, so I've gotten used to the idea that I'll never be able to foresee which way BMW will go.

[creepy coupe]

Also worth remembering is that throttle butterflies can. on part throttle positions, cause faster gas speeds and help improve low end torque.

[3XTR3M3]

Originally Posted by mkoesel

Just fixing that part of the quote for them.

Ouch