[Diy_efi] RE: Timing and dyno pulls

[Eric Deslauriers]

DATA: A 97 M3 gets 2-4mpg less on the highway on 87 octane than 89 or 93.
And you can really tell that the power went away. Note that you don't hear
the pinging, but you do feel the engine back off significantly where it
usually pulls.

There *are* some cars that come stock that actually take advantage of the
higher octane rated fuels. :)

This was a friend of mine's M3 (US spec, 240hp 3.2L, stock).

Ditto my 98 K1200RS motorcycle. It supports 87 octane through knock sensors.
But you can really tell when you're running it (Sometimes, in Nevada, you
gots to take what you can gets).

Eric D

> -----Original Message-----
> From: diy_efi-admin at diy-efi.org [mailto:diy_efi-admin at diy-efi.org]On
> Behalf Of Adam Wade
> Sent: Thursday, December 19, 2002 4:07 PM
> To: diy_efi at diy-efi.org
> Subject: Re: [Diy_efi] RE: Timing and dyno pulls
>
>
> --- William Shurvinton <shurvinton at orange.net> wrote:
>
> > No: dave's point: Best power is way off detonation
> > in a race engine. My question, why does a modern
> > road car gain 10HP when run on high octane (real
> > test, think it was a BMW) when all it has to go on
> > is the knock sensor.
>
> > Inference: it must be running close to knock all the
> > time.
>
> Often, that is the case.  With the lean mixtures
> reguired for current emissions, lower-octane fuels
> often require retarded timing to prevent detonation,
> IME.  Usually in cars like the BMW, you will find a
> recommendation in the manual for a higher-octane fuel
> in any case.  Just because you CAN run it on a
> lower-octane fuel doesn't mean it's a great idea.  As
> a rule, I tell people to run the lowest octane they
> can without pinging; if the car retards timing on a
> knock sensor, use what the manual recommends, in
> general.
>
> > I quoted F1 because it is an extreme case. The
> > engines are run at riduculous coolant temps and revs
> > and until recently were billet unobtanium.
>
> I like to think in many ways they still are.  ;)
>
> > I like beryllium in space apps, but not sure I want
> > it in my car.
>
> Sure makes repairs a bit more difficult, I should
> think.  ;)
>
> > However the coolant temp in this case is due to not
> > being able to get the heat out, not because the
> > engine liked the heat.
>
> True, although again I think they are primarily
> concerned with components failing when they get too
> hot over anything else.  As I'm not a design engineer
> for an F1 team, I can't say for sure.  :D
>
> =====
> | Adam Wade                       1990 Kwak Zephyr 550 (Daphne) |
> |   http://y42.photos.yahoo.com/bc/espresso_doppio/lst?.dir=/   |
> | "It was like an emergency ward after a great catastrophe; it  |
> |   didn't matter what race or class the victims belonged to.   |
> |  They were all given the same miracle drug, which was coffee. |
> |   The catastrophe in this case, of course, was that the sun   |
> |     had come up again."                    -Kurt Vonnegut     |
>
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