After spending several hours on the dyno today, I got to work to find
several bug that need to be fixed RIGHT AWAY. ARRGGH.
I had hoped to determine an ideal needle lean for cruising, richer
under power. One that would give me good gas mileage and would not
cause predetonation. The short form of what I learned is that if I'm
running racegas at the track, the needle I choose won't make a big
difference in the power the engine produces. I had hoped to also get
some dyno runs with the smaller (high boost) blower pulley. I just
didn't have the time to do that.
I have gotten the cage welded so that it is now SCCA legal, the front
wheel bearings properly shimmed, and the cage and exposed metal in the
interior is now painted (white) and looks a lot better. Thanks to
everyone who's helped.
One of the things that I was trying to research was piston position
versus RPM at various loads. I've noticed that cruising on the
freeway, I run about 5-10" Hg of vacuum. It seemed as if no matter
what the rpm, the piston had risen about 5/8" at 5" vacuum. (Sorry, my
guage is in SAE units and I'm using 1/8" because that's what's on the
needle profiles).
I was rather surprised because I expected piston/needle position to be
more dependent upon flow.
Likewise at full throttle, it seemed as if the piston was full open
(is that 11/8" ?) pretty much from about 2500 RPM on up.
The other interesting datum is that mixture did not make much
difference (maybe a couple of HP) anywhere between 0.7% and 9%
CO. This dyno test got me to work really late (like 3PM rather than my
normal 8AM), so I can't really analyze the data right now. I'll try to
have a friend scan and OCR the dyno runs for you to analyze.
I've been running a conservative 8 degrees advance (at idle - 860 RPM,
looked like about 30-32 full advance) to prevent pinging on street
fuel. My max power on street gas was 97-99 HP at 5800-5900 RPM
(best was on a stock BBA needle 1.3% CO 99.3 HP at 5913 RPM, 99.3 MPH 4th
gear).
I swapped another needle or two through, and since the richest needle
gave close to the same power, I decided that I would just run it this
weekend at the track, as it was the "safest". I put that needle back
in (a custom profile, the aforementioned modified BBA).
The tank was nearly empty, I think I actually started to run out of
gas on the run, so I put in 1/2 gallon of street gas, did a couple
more runs then added 2 gallons of 110 Octane race gas.
When I switched to race gas my maximum power dropped to about 86
HP. We advanced the timing up to 14 BTDC, and got 100.7 HP at 6041 RPM
at 9.6% CO).
I had hoped to get a dyno reading with the 66mm blower pulley on race
gas, in addition to my runs on the 76mm pulley. I would very much like
to purchase an 84-86mm pulley so that when I go back for my "final"
set of dyno runs I can compare if I get more power on street gas with
higher boost, and probably less advance, or if a little less boost
will allow me to get more advance, and therefore more power.
I was very surprised at the amount of power I lost going to mostly
racegas. The car runs a lot smoother on race gas, but I think that
this weekend I'll try 104 octane rather than the 110.
I also datalogged the readings off my O2 sensor for each of the
runs. I've got the time that I started datalogging marked on each dyno
run readout so we can compare readings off the O2 sensor with the
readings off the gas analyzer on the dyno.
I hope to get a much better writeup of my research and conclusions,
which I hope will help others. With luck, I'll also have good mapping
of O2 sensor voltage to the readings off the dyno gas sensors. This is
something that could prove useful to others trying to dial in their
cars without spending $100/hour on the dyno.
Speaking of dyno time, I'd like to give a big plug for, and thankyou
too Randy at Integrity Automotive in Scotts Valley. He's been very
generous with me, so if you have any carwork that needs to be done,
and you live any where near Santa Cruz, consider taking your car to
him and telling him that I sent you.
Larry
--
I've found something worse than oldies station that play the music I used to
listen to. Oldies stations that play the "new" music I used to complain about.
lrc@red4est.com http://www.red4est.com/lrc
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