dlp@akgua.UUCP (D.L. Philen [Dan]) (11/06/85)
In a recent article I suggested using a Unisyn to set your SU carbs. Another
article suggested using a Colortune. Now a few comments about setting up
engines. Both items work very well and give reproducible results. I
have no problems with using either device, but consider this (I bet you
haven't considered this).
All these devices set the engine to run best AT IDLE. The real
problem is to set the engine to run at RPM. This is usually difficult
unless you have a really gullible friend who doesn't mind riding on
the fender, next to a screaming engine, while doing 60 mph or more.
If you are really after getting the most from your powerplant you want
it adjusted to perform best at some rpm other than idle. I could best
illustrate the problem we face in the Southeastern (now Sportscar)
Vintage Racing Association (SVRA). We take a stock (35 year old),
1250 cc, 4 cylinder, MG TD engine (XPAG) designed to red line around
5500 rpm and "slightly" modify it to run at 7000 rpm. That is a
really different beast than your run-of-the-mill engine. It doesn't
run well at idle, and usually only "comes on" around 4500 rpm.
The problem is how to set the carbs to run best at 4500-7000 rpm.
A lot of trial and error is usually envolved. Sometimes you take it out,
run it up to speed, shut off the engine, coast to a stop, and pull the plugs.
As you see this is quite time consuming, but it points out some of the
problems in setting up an engine for max. performance. Not only is the
carb involved, but also the ignition system and spark advance mechanism.
This is not a trivial problem and I mention it only so that you will
realize that setting the carb at idle is not the definitive answer, but
merely the most practical solution to a complex problem. For driving
my street legal MGTF I still use my Unisyn. I have used the Colortune
and it works well too.
Press on Regardless. Dan's English Car Garage akgua!dlp
CAUTION! All parts falling off this car are of the finest English workmanship.