Brand of Gasoline

[Louis-Alain Richard]

You know what ?

I'll borrow two identical cars from a Press fleet, drive them in parallel
for 500 km, and report back the results. That way, we'll have a
semi-scientific data point... And that'll will fit right in one of my next
editorial for the magazine...

More to come.

Louis-Alain


> -----Message d'origine-----
> De : Grant Lenahan [mailto:glenahan at vfemail.net]
> Envoyé : 21 septembre 2012 14:11
> À : Cody Forbes
> Cc : Louis-Alain Richard; <quattro at audifans.com>
> Objet : Re: Brand of Gasoline
> 
> Yes, completely right. That's why i noted that there is only a finite
> amount of advance possible.  So the idea that we'll just keep advancing
> and get more economy is fallacious.  At high vacuum you are already at
> optimum, likely.
> 
> Advance is (mostly) dealing with the elasticity of air, and the finite
> speed of the flame front expansion, and that especially at high rpms, you
> actually need to begin well before TDC to apply maximum expansion through
> the majority of the power stroke. Start at TDC and the piston is well down
> its stroke before the expansion applies much force.
> 
> however, do it too soon and you begin to oppose the travel of the piston -
> reducing economy and power.
> 
> This in fact is what knock (aka pre-detonation) is,and why it is
> potentially harmful.
> 
> Grant
> 
> 
> On Sep 21, 2012, at 1:34 PM, Cody Forbes wrote:
> 
> > I think there may be some misinterpretation possibly. Timing advance has
> an optimum number which you get ZERO benefits for surpassing. This is
> easily to see on a braked Dyno (not an inertial) with a tuneable ECU. I
> can, and have, watched torque numbers increase to a point as I advanced
> ignition timing and then at a certain point the torque will start to go
> back down. Typically on race gas or E85 I see peak torque in the mid RPM
> range 2-4 degrees before I see knock. At higher RPM the spread is greater.
> On 93 octane it depends on boost level and the engine. The 1.8t powered S3
> race car I tune will easy run 15-18 PSI on 93 with no knock at peak
> torque. Along with watching peak torque rise and fall you can also see EGT
> fall until about the same as when you make peak torque then more advance
> causes EGT to start increasing again.
> >
> > I'm sure that BMW ECU tries to keep it advanced, but only to the mapped
> optimum. Going beyond that is DECREASING efficiency. If its running on a
> lower grade fuel than required sure it'll keep increasing as much as it
> can, but on the proper grade of fuel it shouldnt be the case.
> >
> > -Cody Forbes
> >
> > On Sep 21, 2012, at 12:41 PM, Louis-Alain Richard <5145727795 at bell.net>
> 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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