Gypsie wrote:
Just so I understand let me hypothesize for a moment:
The O2 sensor tells the ECM if there is too much or too little fuel which in turn, along with the information gathered from the afm, tells the injectors to give more or less fuel.
The Cat, through the affect of exhaust gasses passing through the material, burns off residual excess fuel. If set up properly using the Federal controls (coil, afm, ecu, dizzy, etc and mix dialed in to a close proximity to 13-14.7 on the Lambda scale, or even using the Colin method of AFM adjustment) the Cat will do it's task without the feedback offered by the O2.
Kinda-sorta. What is often lost in discussions of cats is that back in 1981, there were two kinds of cats commonly used: oxidation-only (aka. "2-way"), and the new-fangled oxidation-reduction (or "3-way") cats. 2-way cats, which didn't require O2 sensors (but which did need oxygen-rich, engine-destroying lean mixures) were installed on Federal-spec Vanagons. 3-way cats, which require a "lambda-feedback loop" using an O2 sensor, were installed on CA-spec Vanagons. The Vanagon user's manual, if you're fortunate enough to have one, explains this on page 78.
So even with setting the AFR to as close to 14.7 as you can, the Federal system won't be able to provide the lean-rich-lean-rich cycle that the 3-way cat needs to do its job effectively. Having said that, I'm pretty much running the same sort of setup on my van, simply because my Canadian-spec van didn't come with a cat, I needed to install a cat to import it, and 2-way cats just aren't sold anymore, so I'm stuck with a 3-way cat on a Federal model. So far, the cat hasn't melted down, but I don't know if it's actually doing any good.
If you want further reading on catalytic converters, I found this pretty good article from a Google search. It's technical enough, but doesn't require a Master's degree in chemistry:
http://www.bearriverconverters.com/data/CatOpp.pdf
Gypsie wrote:The condition of the Cat is unknown anyway so we will set to the best of our abilities.
The ultimate goal is minimum disassembly of the Cali engine components (ie exhaust system, heads etc.) to be installed and used for a short period of time while the Federal engine is rebuilt. After completion, the Cali engine will be worked and reinstalled into the Cali donor rig.
I follow, but things usually take longer than you expect, and that applies in spades to engine rebuilds. You may find that the "short period of time" stretches out to several months. But the exhaust parts are accessible with the engine in the car, so if you all decide to swap the components at some point, it won't require dropping the engine.
Another advantage of using the Federal exhaust is that you have the option of replacing the cat with the straight pipe that came standard on Canadian models (if you can get away with it in your jurisdiction). It's VW part number 021-251-541. CIP sells it for $50
http://www2.cip1.com/ProductDetails.asp ... 21-251-541
aircooledchris wrote:if the Federal setup used a CAT as well, but didn't have an O2 sensor, then I wouldn't worry too much about hurting the CAT.
See discussion above on 2-way vs. 3-way cats.
aircooledchris wrote:I am going to try and run all of the CA setup on mine, but with federal heater boxes and 72-74 style exhaust. Im thinking of just putting the CAT right between the extractor and the muffler. Since the CAT has an O2 test port on it, I can still use the stock O2 sensor. (or even swap the sensor for one with the two wires coming out of it, one for the CA computer and one for an LM-2.)
I'm a bit confused about this: the 72-74 exhaust was a big muffler that bolted directly to the heat exchangers. No extractor involved, and no real place where you can stick a cat. (I'm assuming we're using "extractor" in the commonly-used sense to describe an aftermarket twisty-tube "performance" style exhaust that thas been flogged to us VW enthusiasts since the 1970's). So if you're considering bolting a cat onto the output of an extractor, then you may find that the exhaust gases will have cooled off too much by the time they get to the cat for it to do any good.
Same goes for the stock, unheated O2 sensor: it needs to be hot to work. Using a wide-band with an LC-1 would take care of the sensor heating issue, but wouldn't do anything for making sure the gases are hot enough for the cat. I suspect I'm running into the same issue with my 3-way cat in the stock Federal location. I have an EGR probe stuck in my exhaust just after the U-bend, and even though I've only taken it for short drives around the nieghborhood, the temperatures I'm seeing aren't very encouraging.
