Brand of Gasoline

[Grant Lenahan]

I realize all that, but still disagree with your buddy that:

1 the degree of back-off at partial throttle (say, below 50%) is significant
2 that, given the ability to back off, regular gas is detrimental (meaning, will do permanent damage to the motor)

If it does damage, apparently their knock sensor feedback loop is not working. By definition.

I'd like a really good explanation of how that can be so. At 50% throttle the effective compression is ~ 5:1. 

Just because he works for BMW does not mean he can repeal the laws of physics.

And remember, we're trying to explain a LARGE difference, not a marginal one.

Grant
On Sep 21, 2012, at 12:41 PM, Louis-Alain Richard wrote:

> Spent the night with my good friend Lucian, a mechanical engineer that is a
> tech/sales trainer at BWM Canada. He also translate and writes the teaching
> material from Munich. He knows a bit about cars, let me tell you.
> 
> I've asked him about knock sensing in BMW engines and he said that knock is
> monitored all the time. Even on the highway at part throttle. More, he said
> the ECU will try to advance timing all the time, until knock events are
> detected, and then back up a bit. It will do that again and again and again.
> That way, the ECU knows that it extracted the last bit of energy from each
> liter of fuel for any conditions (temp, speed, gradient, atmospheric
> pressure, etc). 
> 
> This fact do confirms the theory that Premium fuel is not only for WOT
> events, but is beneficial all time on an engine that is mapped for it. 
> 
> And regular gas is detrimental for such engines... 
> 
> Picture the G37 IPL convertible that I drive this week. I'm SURE the
> preceding journalist didn't fill her up with premium. At low speeds, 25 mph,
> I can clearly hear knock with a steady throttle when the 7-speed auto trans
> gently upshifts. And every time I accelerate the tiniest bit... Sounds like
> an old Tercel from the 90's.
> 
> Fuel economy is appalling : 17l/100km in town, that is 14 mpg.
> 
> Will empty the tank this weekend and report back with Premium.
> 
> Louis-Alain
> 
> 
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