Weber 32/36DGV verses the Weber 38DGES

Gnarly4X
(carpal tunnel)
Wed Nov 02 2005
09:06 PM
power. It also produces higher emissions and potential engine damage.
When the engine is under sever load and a low RPM (like climbing a steep hill in top gear) then engine temperatures rise and will
begin to ping. That is normal. That is desired. Yes, you are damaging the engine and melting the piston. (More on that later). That
means that you have crossed the line are no longer is that compromise zone. That is good because engines are not meant to be
operated in that fashion. PINGING MEANS IT IS TIME TO DOWNSHIFT.
Engines, particularly motorcycle engines, make their power in the upper 1/3 of the RPM range. If you are under sever load, you
want the tachometer up near red line. That is where the engine was designed to run and it is by far the easiest on the motor.
When you are lugging an engine, the oil pressure drops and the piston rods begin hammering against the crank shaft because
there is no longer a high-pressure film of oil to prevent it. Likewise, the crankshaft in turn hammers against the block (or case). In
either case, the damage you are doing to the bearings is far worse than the slight amount of aluminum being burned away. If you
switch to a higher octane fuel to prevent the pinging, you may not realize you are destroying your bearings.
You could also retard your timing or richen the carbs to prevent pinging under severe load on whatever octane gas you desire.
But again, this will mask the bearing damage you are doing. It also moves the threshold of that "sweet spot" downward. Now you
will not have pinging under sever load, but you will also not have complete combustion under normal conditions (such as
cruising), and that can lead to poor fuel economy and excessive carbon deposits.
In a nutshell, the engine should ping if properly adjusted, under low RPM, severe load conditions. Next, you should use your
transmission to avoid those conditions.
--
Larry Piekarski
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Re: Weber 32/36DGV verses the Weber 38DGES
Quote:
interesting information on pinging...
found here http://www.msgroup.org/Contrary/NEG037.html
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>Pinging is the sound of damage being done to your engine.
That is not true. In a normal non-pinging engine, the spark plug fires at the desired time and initiates a spherical
flame that moves across the combustion chamber consuming the air/fuel mixture as it goes. This flame increases
the temperature and pressure in the cylinder and creates your power. When the combustion chamber temperatures
get high enough, it is possible for the air/fuel mixture to spontaneously combust (pre-ignition). This is what happens
when a car "diesels" on runs on after the ignition is turned off. Commonly the source of the ignition is from carbon
deposits or simply a sharp edge on the piston or head surface.
When both pre-ignition and regular ignition occur simultaneously, you get two flame fronts moving towards each
other. When they meet, they extinguish each other with a loud pop. That pop is the ping. This effect is similar to
turning off the acetylene on an oxy/acetelene torch. The ping is not harmful. But it is an indication that there is
something amiss, something that may be silently damaging you engine.
One source is excessive carbon buildup. That means nothing is wrong and the engine simply needs a good
cleaning, ON THE INSIDE. The reason for the excessive carbon could be due to an oil consumption problem, either
leaky valve seals or worn piston rings. Either way, the head needs to be removed to solve the root cause, the can be
decarboned at the same time. An engine is normally good at burning away carbon on it's own. The problem could
also be due to mal-adjusted carbs or a dirty air filter causing the engine to run way to rich. Again, that is a problem
that needs correcting and a 1/2 bottle of Techron engine deposit cleaner will quiet it right up. In no case does the
pinging from carbon cause engine damage.
The other cause of pinging is excessive cylinder temps. As the temps rise, the sharp edges of the piston will ignite
the mixture. The excessive temperature will also start to melt the piston. Again this could be due to a number of
situations. One case would be a dirty air cooled engine or a water cooled engine with some problem with the cooling
system. The other possibly is that engine was designed to run that hot (like a race engine) and simply needs higher
octane. This will in time cause engine damage, but it is again and indication of a problem. If the engine is dirty,
higher octane will cause the pinging to go away, but it is still running too hot.
Contrary to what the gasoline companies advertise, engines never need to change octane. If a new engine is happy
with 87 and at 40,000 miles starting pinging, that means is time for some maintenance, not higher octane. Many
european cars and bikes need higher octane because of their better fuels. The US has the "worst" fuel in the world.
Germany starts the fuel grades at 96 octane, the their engines are designed to need it. Now, many foreign
manufacturers "de-tune" their engines to run on our 87 octane gas. If your engine needed 89 or 92 octane new, then
that is what you must run. If it didn't need 92 new, and does now, look for a problem.
Your comment, however, about altitude was right on track.
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