[Diy_efi] boosted compression ratio

[Bernd Felsche]

On Sun, Dec 22, 2002 at 12:50:24PM +0000, Mike wrote:
> At 08:00 PM 21/12/2002 -0600, you wrote:
> >I'm currently rebuilding my project Honda. Wondering what kinda
> >CR you guys would recommend. My engine management system is a
> >modified OEM ECU by Hondata. I will have full control of
> >fuel/timing map and boost through an electronic boost controller.
> >I also have a knock sensor with individual cylinder retard.

> Interesting, ? Can you elaborate on your knock sensor relationship to
> which individual cylinder retard is managed - or do I infer you have
> multiple knock sensors...

> ie. If you have one knock sensor - how do you know which cylinder
> to retard by how much - especially at higher rpms, is there a low
> rpm cutoff for this algorithm ?

Because the detonation occurs in a narrow time window after spark;
usually after TDC. So you know which cylinder because it's the one
recently fired.

AFAICT, that's how Bosch and others have been doing knock management
since the mid 1980's.

On my car, the retard is rather aggressive; and it will drag other
cylinder timings back is there's more than 6 degrees difference
(IIRC) between cylinders so they all still fire fairly evenly. Quite
a noticeable power drop; very sensitive to humidity.

"Pings" quite audibly at times from low revs, even with Ultimate 98.
But not on humid days. On a cooler day, with say 80% humdity, it
feels like the engine is putting out at least 10% more mid-range and
even more low-end torque than with 50% or less RH. Of course; as it
gets even colder, it doesn't matter that there's 100% RH; it'll
still ping.

> Does this occur at about say 4000 rpm ?

30 milliseconds between sparks; no problem.

Let's talk about 12,000 rpm. :-)

-- 
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