StealthElephant

Does running slightly rich hurt anything over time (other then fuel economy)?

Obviously being lean creates a heat problem, but does running rich cause any mechanical damage? Alot of FI guyes run rich as a safety....

scottland

its really bad for a catalytic convertor.

its really bad on fuel ecconomy.

and it fouls plugs.

if your car is running rich, find out why it is running rich and fix it.

StealthElephant

My car isn't running rich, I'm just curious.

So it doesn't cause any actual damage to the engine? Running lean can cause overheating, preignition...etc etc, that can destroy an engine....can running rich damage an engine?

RJR99SS

It's not very good for power or fuel economy. But it wont cause any "physical" damage besides creating a lot of soot; fouling plugs and clogging cats.

I saw a few times where rich running cars had a pinging problem because of the vast amount of carbon in the combustion chambers retaining heat.

StealthElephant

So theres no truth that running a little rich will help cool the cylinder down slightly?

RJR99SS

The key word is "slightly".

I'm not sure why you would need that, unless we're talking heavy duty racing.

StealthElephant

It seemed like most people have the attitude that it's better to be rich then lean, but I someone posted that it's not good to be rich either. Personally replacing a Cat is easier then replacing an engine.

8Mike9

I think quantifying the answer is in order.

Running rich for a prolonged period of time, will most likely hasten cylinder bore/ring wear.

The old saying "rather rich than lean" should only be used during the tuning cycle../WOT blasts when rich will probably cause much less damage that WOT throttle blasts when lean.

The idea should be to tune the engine so it's right, not leave it rich.

ZZ28ZZ

Running rich (like 11.5 or 12.5 : 1) is a must at WOT for combustion chamber cooling which helps prevent detonation.

How rich it's running is important. If it's waaay rich, the fuel will wash the oil off the cyl walls which accelerates wear. Fuel can also contaminate the oil leading to excessive wear all through the eng.

If it moderately rich for a short period, the eng will probably be ok.
The cat won't be too happy abt it.

If it's allowed to continue for a long period, the soot will build up in the combustion chamber. This causes the compression to increase and leads to detonation and possibly pre-ignition..