RE Diesel Performance:
At many diesel shops, the first step in a low power drivability
complaint it to test the fuel.There is some reeal pee-water out there. I
did an informal survey, and found most fuel is around 45 cetane, with some
as low as 42. Most states do not have a cetane requirement for a retailer
to market their fuel as "Premium," so you may not be getting 50 cetane even
when you by Premium. I know Total has 50 cetane and I think Texaco and
Standard do. The 6.2 and 6.5L engines, and most other diesels, like around
50 cetane fuel and thats where a fuel cetane enhancer can help. 50 cetane
fuel isn't available everywhere.
I personally did some dyno tests of Stanadyne Performance Formula
on a 6.2L NA diesel (so listen up CUCV owners) for a magazine story. It was
worth 8hp over the untreated 45 cetane diesel. How much gain YOU get will
depend on the quality of the diesel fuel you run. If you are using 50
cetane fuel, you may not notice a big, or any, perfomance increase with the
Stanadyne. OTOH, the stuff will amaze you when used with lower grades of
fuel. It's especially good for improving winter or winter blended fuel
(either #1 for extreme cold, or a #1 & #2 blend), which have fewer BTUS
that straight #2 and produce less power. The higher cetane fuel n also help
cold starts and reduce white smoke.
As to general diesel performance, more power comes from more air
and fuel. Increasing fuel rate alone is no good unless you can increase
airflow as well. Increasing intake airflow by reducing inlet restriction
may help, especially with a naturally aspirated (NA) diesel.Reducing
exhaust restriction cn also help. Look at how much black smoke you are
producing now on a long, steep highway hillclimb at full power. NA diesels
will produce more than a turbo diesel. If very little smoke is produced,
you could probably increase the fuel rate a bit (see manual). If lots and
lots of smoke is the result, try the same hill with your air filter
disconnected. If the smoke is dramatically reduced and power feels better,
a freer flowing intake may help 9or perhaps air filter service. Black smoke
will increase with a load aboard, so you want to tune for your most common
situation, full or empty.
As top the exhaust, you could hook a pressure gauge up to the
exhaust (as far up as you can, tapped into the exhaust manifold even) and
measure backpressure on a 1-15psi gauge. It should be near zero, or under
4psi under a full load for best performance.
Do the big GI trucks have a pyrometer (EGT, exhaust temp gauge)? If
so, you could use it as a tuning tool. You should easily be able to get
over 1000 degrees at full power/load. Being that this is a big industrial
diesel, probably well over 1000 degrees ispossible (the 6.2L max is 1150
intermittant, 900-950 continuous). If it's a turbo diesel, you should
attain the maximum rated boost as well. My diesel perfomance tuning
experience is with small diesels and, though the principles are the same,
the execution differs. I may be oversimplifying this as well, but I had a
few moments and thought I'd pass a few tidbits along over my break,
Jim Allen
This archive was generated by hypermail 2b29 : Sun Jul 02 2000 - 23:51:29 PDT