>> We ran the p-port engine again today on the EFI system
>> and slide throttle. Runs great. Will idle below 1000 RPM.
>> Starts easily. Idles smoothly more or less under 1500 RPM.
>> The mixture through out the RPM range is better with
>> the $200 manifold referenced fuel pressure regulator
>> but still a bit rich on the low end and a lean on the
>> high end. We are running out of dyno time to do further
>> mixture and ignition timing tuning. Max HP was 222. I used
>> Tracy's Mode three to set the mixture richer by eight clicks
>> over the entire MAP and RPM range. We did no Mode 1 tuning.
>>  From here on out final tuning will be done with a prop
>> load in the air at altitude. The EGT's track together within about
>> 40 F which Dave says is not that bad. Could be a
>> difference in fuel injectors. Perhaps one runner at
>> the slide throttle is leaking more air than the other.
>> No time to build a new sealed slide throttle before Dave must
>> dyno another engine. We will do one more run tomorrow or the
>> next day with Jerry's muffler.
>> Next project is to bench test some fuel injectors.
>> Paul Lamar

Am I missing something here? - If I follow the thread of this testing - by
eliminating the butterfly restriction of the carbs, you only LOST about 20HP?
Vance

Don't try to draw any conclusions from that number.
That was just an initial run with the EFI. We have a tuning problem.
The mixture and ignition timing are far from optimized.
If you run it at low RPM for long the plugs foul. Too rich.
It is still too lean on the top end to be comfortably
by running it long enough to set the mixture. The carb was doing
a much better initial job of keeping the mixture in the ball park
throughout the RPM and MAP range.

There needs to be a steeper slope to the default EFI mixture curve
as a function of MAP. Therefore one must creep up on it by running
the engine at increasing prop load 500 RPM at a time and setting the mixture.
That is the way Tracy allows one to tune the engine in the air.

Perhaps Tracy could offer a steeper slope as a default option.
That would be a better starting point for this engine. In the
final tune the mixture as a function of MAP may not, neigh
probably not, be a straight line. MAP alone is not
an indicator of HP. HP is a combination of MAP and RPM.
Right now fuel injected is a straight line function of RPM.
MAP, on the other hand depends on load, runner length AND RPM.

Another feature that would be nice is a down loadable mixture table
using a PC and USB port as most other EFI system manufacturers offer.

We ran out of expensive dyno time. IMHO the runners are still too long.
At 7500 RPM the HP was climbing towards the second harmonic.
My guess.  Tuning for the second harmonic is dumb because
the runner skin friction loss is twice as high.

Paul Lamar

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