[Diy_efi] RE: Timing and dyno pulls

Adam Wade espresso_doppio at yahoo.com
Fri Dec 20 00:04:34 GMT 2002


--- 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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