It could work to richen fuel but will not work the other way around. The
unburned PCV "fuel" will *not* combine with excess O2 in the exhaust pipe
upstream of the O2 sensor.
Furthermore, the SBEC usually runs rich @ WOT anyway. Unless you have a major
increase in air intake,too little fuel is seldom a problem. Most of the
aftermarket "chips" lean out the mixture for improved performance.
Dr. Pat
----------
>From: Dkota4by4@aol.com
>To: dakota-truck@buffnet.net
>Subject: DML: F/A Ratio?
>Date: Sat, Mar 20, 1999, 11:19 PM
>
> This is off the DiRT list. Does this sound like it would work to anyone?
>
> ____________________________________________________________________
> Wanna richen your air to fuel mixture to get more horsepower, even when
> your PCM is in 'closed loop' and getting feed back from the O2 sensor?
>
> Get two 5-6 inch pieces of one eighth, or three sixteenths, inch diameter
> tubing made of stainless steel. Stainless steel brake line stock are a
> good source.
>
> Bend a smooth 90 degree curve in each of the stainless tube near one end.
>
> Drill an appropriate sized hole in both of your right and left exhaust down
> pipes for the tubing to fit snugly through. Choose a spot for the holes
> fairly near to where the cast iron manifolds or headers end. Insert the
> tubing with the 90 degree bend going 'downstream' so that the open end of
> the tube goes toward the catalytic converter end. Push enough tubing in the
> hole so that the tube is about one quarter to half an inch away from the
> exhaust pipe wall. Weld the stainless tube to the exhaust pipe in this
> position.
>
> Now you have what engineers call a 'pitot' tube pointing backwards in your
> exhaust pipe. As the high speed exhaust gases rush by the backward looking
> tube opening - they create a partial vacuum and suck air into the exhaust.
>
> The O2 sensor will sense that added oxygen and think that your engine is
> running too lean an air/fuel mixture. It will then 'richen' the mixture.
> You may need to pinch the outside opening of the tube to keep from
> richening it too much.
>
> ( If you have a 1996 or later Ram with the OBDII system, if you richen the
> mixture too much the O2 sensor behind the catalytic converter may give you
> a 'check engine' light. But you can run a richer mixture up to 13 and
> still meet the pollution specs - and anything richer than about 13.5 to one
> doesn't make any more horsepower. This is why Dodge can sell a smog-legal
> "Performance PCM Computer" ! )
>
> A neat thing about this trick, according to the guy who told me, is that it
> is almost self-adjusting once you get the tube hole pinched to the right
> size. The more rpm the engine builds up, the more the exhaust gas velocity
> increases, and the more 'O2-sensor-foolin air' you draw in.
>
> ------------------------------------------
> Not interested in power tricks,
> but want to lean out your air to fuel mixture to get more mpg? If you lean
> the mixture out to about 16 to one, the economy should go up 5-10%
>
> How do you fool the O2 sensor to go lean?
>
> Make the stainless tube modification just like above, but intead of leaving
> them open to the air, connect them with a tee to the PCV valve hose.
>
> The 'blowby' gases in the crankcase always have some unburned gas. If you
> draw this gas into the exhaust pipe ahead of the O2 sensor, the blowby will
> combine with what excess oxygen is in the exhaust pipe and reduce the
> oxygen content further before the exhaust gases reach the O2 sensor. The O2
> sensor will sense a 'rich' mixture and tell the PCM to lean out by
> shortening the injector pulses.
>
> If the mixture gets too lean, pinch the rubber line to the PCV valve a little.
>
> An added benefit of this trick is that it may create a partial vacuum in
> the crankcase. Racers sometimes do this on purpose.
>
> A crankcase vacuum does three small but good things for power, economy and
> reliability:
>
> 1. It reduces crankshaft 'windage' or air drag.
>
> 2. It reduces the pressure on the bottom side of the pistons. Reducing the
> pressure on the bottom of the pistons has the same effect as increasing the
> pressure on the top of the piston. It makes a little more power.
>
> 3. A crankcase vacuum slows down, or even stops, engine oil leaks !
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