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Any aftermarket 3 way cat is far less superior to a factory 3 way cat for California. Throw on a known good used factory cat and retest for $hits and giggles
Throw on a known good used factory cat and retest for $hits and giggles
"Good used" might be a contradiction in terms for a car last produced over 25 years ago. I replaced my spent CA aftermarket cat (DEC) with a used factory cat and passed this last time (baaaarely). I feel I got a little lucky. It's worth a try if you have one available.
Any aftermarket 3 way cat is far less superior to a factory 3 way cat for California. Throw on a known good used factory cat and retest for $hits and giggles
In original condition, I'd agree, but time takes its toll. Crazy Eddie tried to pass with his original cat last summer. Both the car and the cat had less than 50k miles, and both the car and cat have lived a privileged life (garaged, sealed, removed for track use, etc.). We tuned it down to the point where it would almost pass, but couldn't quite get all three numbers under the limits. Very frustrating actually, as we kept missing by the smallest of margins on 1 out of 3, and it was clearly tuned to be as clean as it was ever going to be without making mechanical changes. Without touching another thing, we put a new DEC on the car, and it passed with embarrassingly low numbers -- close to zero on all counts. The smog tech was even worried the state would think he cheated...
I was suspecting the cat as well, mostly because in the location for it in the 3" LR exhaust I have the cat position seems farther back than with the factory set up, with it leaving space to dump the WG ahead of the cat. That far back it doesn't get hot enough on the rollers to work. Some guaranteed to pass, a new O2 sensor for good measure, and a very hot cat before pulling in next time and see what happens.
What chips are people currently using that pass California emissions, or does anyone have a loaner set of stock chips?
Thanks for the replies!
For what it's worth, I passed once using a SFR (magnaflow) cat in that position. I did work to get it hot first though, and LR may not be using the same kind of cat since not in CA. Your number suggest to me that you have a multiple things going on. Normally you add fuel to bring down the NOx, but your car is already rich, so seems like both tuning and something else is going on. I'd get stock chips (everything) to start, and new O2 sensor (if not replaced with the ignition), and see how far that takes you. Does the motor run nice and smooth or does it miss? Missing can help all numbers go up. You might check the cam belt alignment too just to rule that out. And run fuel additive for a while intended to clean out carbon from the pistons -- not sure any of that works very well, but carbon build up could be part of the issue too. (If you take the intake off, you can look at the back of the valves, which are often a pretty good proxy.) If all that gets you close, but not quite close enough, then a DEC cat will probably drive it home.
It's not running rich. It running just right. The rhodium in the first part of the cat suppose to "break" the bond of the HC and the NOx. The platinum or palladium in the second and third sections of the cat bond the CO to the O and the the C to two O's and two H's to one O. like I said before again and again. Put on a good cat and you'll pass without issue. It's not rocket science it simple automotive smog chemistry. The cat likes high NOx not high HC and that's not high HC in the test shown. I can tell the cat isn't working with those numbers.
Motor runs great with no miss, and makes great power. Installing 951 max chips when they arrive this week, and have a line on some stock chips to try as well (will have appropriate FPR in for both), as the old welt chips may be the cause of some of this, and was a good excuse to upgrade. I ran some cleaner through and tracked it so any carbon left in there will only be removed by a tear down. Plugs looked right last time I checked as well.
Part of this may be my own mistake, the 3 way magnaflow cat I installed, turns out is NOT carb approved, though the company that sold it said it would pass CARB, I missed the slight of words. New CARB approved cat en route now. Will put this in and drive enough to get it hot and straight to smog check without banging it around. I feel a little dumb about it, but what can you do.
Oh and I just did belts 2 months ago and everything is right on TDC. Is it possible to get a usable dyno AFR from tailpipe with a cat in place? I don't have a WB O2 installed yet.
No. That's what the CO test pipe is for. The one that is usually broke off or removed on the crossover, or cat section on the 944. It suppose to reach up behind the cam tower and be capped. Not to be confused with a cat test pipe. That way a CO reading can be measured before the cat. Look under your car and on the top of the crossover you'll see the fitting for it right after the header connection. Let me take a few photos.
This is capped
I have a LR back pressure adapter on the crossover but the CO tube mounts there and passes up to the back of the cam tower for pre cat CO measurements.
Now that I don't know. Im sure the "sniffer" for the smog machine could be adapted somehow. If there's a will there's a way. Could use a reducer hose that attaches them together? It would need to handle heat for a few minutes and not melt giving false readings. Or just hold the sniffer right on the tube?
It's not running rich. It running just right. The rhodium in the first part of the cat suppose to "break" the bond of the HC and the NOx. The platinum or palladium in the second and third sections of the cat bond the CO to the O and the the C to two O's and two H's to one O. like I said before again and again. Put on a good cat and you'll pass without issue. It's not rocket science it simple automotive smog chemistry. The cat likes high NOx not high HC and that's not high HC in the test shown. I can tell the cat isn't working with those numbers.
I'm a little less convinced than you because I've seen these cars run cleaner than that without any cat, but think the upshot is the same: make sure the base tune is good (stock chips in closed loop and not missing), and then try the DEC cat if it still fails.
All of the aftermarket cats are like that, there's just not enough heavy metal in them. That's why the OEM cats cost 4 times as much.
I have two huge magnaflow cats I use when I smog my LS 951 here. They only go on for the smog test, the rest of the time they sit on my garage shelf as my car is largely a track car...
Interesting graph. I've heard that a well tuned/maintained car can pass emissions without a cat. The graph sure makes that seem pretty hard to pull off (at least here in the Denver metro).
I have passed 3 times without a cat in the Denver metro. However, the last 2 times I used an extremely modified emissions tune and was running a mix of gas and e85. Since my cat is gutted I pass visual too. It took 3 tries to get the tune, but in the end it passed with everything well under the limits and it didn't hurt power as much as I thought it would.
It can be done without a cat, but I doubt it can with a stock or common tune.
01-04-2016, 10:28 PM
