[Diy_efi] boosted compression ratio

[Mike]

At 07:09 AM 23/12/2002 +0800, you wrote:
>Mine's not a turbo engine.

mmm Well OK, then I interpret you are after max ignition advance
as a fuel economy measure and havent modded the chamber or
built an engine from parts so arent facing a high/unclear CR
issue which necessitates highest octane... ?

If that were the case, then I'm not sure max economy would be
consistent with max ignition advance *just prior to detonation*,
there may well be a shifting 'window of opportunity' etc.

And it depends a lot on the ECU and its mapping, changing the
base timing may do very little to overal economy, remapping
the ECU will likely give you more economy gains at the expense
of driveability.

There seems to be some anecdotal evidence and I seem to recall
observations from others on this list that max power wont
necessarily happen where ignition is advanced to just before
the point of detonation.

How about extractors, using that with ULP might well be (in the
long run) cheaper than BP 98 and high ignition advance ?

You also mentioned you want the engine to last another 250,000K
or so - well your aim of max ignition advance before detonation
may be inconsistent with that due to the 'silent detonation'
issue which robs power just prior to readily noticable detonation
and may stress the rod bearings etc !

>Besides; the base engine of a road car shouldn't need a rebuilt
>nowadays until well over 300,000 km. Turbo and exhaust probably will
>require replacement at that stage in any sort of performance
>application.  Various bits of plastic in the engine compartment tend
>to be come brittle after 5000 hours at high temperatures, so they're
>more likely the cause of problems with electrical "gremlins" and
>various air leaks being par for the course.

For N/A thats fairly normal. All those people I know who run
turbo engines with fair power output tend to rebuild after
250,000K - I'm doing another engine/head in next 3 months in
preparation for some more serious power and my engines done
about 235,000K but was thrashed a few times when it was stolen
and the previous owner was a bit erratic. After a few mods
 I'm now getting about 170Kw (flyhweel) but aiming for 320 - 370Kw
(flywheel) in the next build. Even at the lower power I wouldnt be
comfortable reliability wise after 300,000K.

I'm curious what your engine configuration is and what your
objective re ignition advance is ?

rgds

mike


_______________________________________________
Diy_efi mailing list
Diy_efi at diy-efi.org
http://www.diy-efi.org/mailman/listinfo/diy_efi