Crank case breather options

[kmead]

Running to an external filter will do nothing in regards to fuel economy or power.

This part has nothing to do with the EGR system which is entirely separate and has an entirely different effect on the motor and its running. This is just a simple manner in which the engine collects and burns the oil vapor and vents the crankcase to atmosphere when not running and to a negative pressure source when it is running to draw it into the combustion process.

Running to an external filater may cause the car to run slightly less rich, have a little less tendency to gum up the carb throats if your car suffers from excessive blow by.

What will happen is that you will have more oil mist in the engine bay (attracting dirt), likely to have some oil smell come into the cabin (particularly if your car has excessive blow by) and greater emissions/pollution that could be avoided with few if any deleterious effects on the car..

Plumbing it into the carb will burn the hydrocarbons from the crankcase vent and avoid the above. It should go into the base of the filter and not run into the face of the filter exterior. Oil vapor and gasoline are both hydrocarbons and burn in the combustion process.

Generally it is just a poor practice with little actual benefit and a number of negatives.

[kilrwail]

I'm not going to get into a debate about this. All I can say is "try it". A lawn mower air filter is less than $20 and a bolt to block the EGR input to the intake manifold is inexpensive. Run a tankful of 91 octane ethanol-free gasoline through it and see what you think.

[kmead]

I'm not going to get into a debate about this. All I can say is "try it". A lawn mower air filter is less than $20 and a bolt to block the EGR input to the intake manifold is inexpensive. Run a tankful of 91 octane ethanol-free gasoline through it and see what you think.

EGR and the crankcase vent are very different things, I only referenced crankcase venting. No debate about the EGR.

[Reallyquitefast]

Hello all,

I'm considering a change of air cleaner from the stock 'turtleback' type to something less restrictive, and am reading up on the question of crankcase venting and EGR now. There seems to be some differences of opinion here. Stuartrubin, how did your experiment turn out in the end?

Erik

[rebar1111]

Cars of the '50's had no EGR but did have a PCV vent which vented to atmosphere via an oil separator.

The EGR was added to improve fuel vaporization, especially in cold weather, and therefor better combustion. Unfortunately. this also dilutes the energy from the fuel/air that could have filled that same intake volume. The net result is cleaner combustion but less horsepower.

The PCV and recycling of the oil fumes produces a less polluted environment, by burning the fumes. Unfortunately, these oil fumes alter the fuel/air ratio. The net result is cleaner atmosphere but a fuel which is harder to burn and less horsepower.

Both the EGR and PCV effects on the fuel/air ratio can be, and usually are, compensated for by the factory when the engine is new and in the factory maintained condition, but the will not provide the maximum horsepower.

Any mods to either system should be followed by an adjustment to the carb jets to establish the proper F/A ratio for performance and/or economy.

A non-maintained EGR or PCV system con hurt both economy and power.

An EGR system is most valuable in cold weather and startup periods, but much less effective at normal operating conditions.

The PCV system is functional all the time.

[stuartrubin]

Reallyquitefast, it's hard to say. There may have been an incremental improvement in the smell, but not much. After a bunch of other issues, I have concluded that the Chinese carb is not jetted properly. This is probably responsible for a bad mix, and subsequent smell.

The car is in the shop right now for a bad throwout bearing (thrust bearing?), and done for the season. Maybe next summer I'll work on the jetting.