Brand of Gasoline

[Grant Lenahan]

That's step #1 - the control.

Grant

On Sep 22, 2012, at 12:57 PM, Cody Forbes wrote:

> Drive them both under identical conditions first to verify that they are as identical as you think they are ;-). 
> 
> -Cody Forbes
> 
> On Sep 21, 2012, at 2:29 PM, Louis-Alain Richard <5145727795 at bell.net> wrote:
> 
>> 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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>> 
>> 
>