Catalytic converter and stench

[JimmyC]

I am plotting an attack on my exhaust stench. I plan to do the standard tuning things and rebuild the carbs, but I am wondering if anybody has tried a catalytic converter on a Pinzgaue? If ican get one to work it should kill the stench, but I am afraid it will either not light up or burn up because the exhaust is so nasty.

[audiocontr]

Changing to pinzissi ignition completely changed the exhaust smell.

[pcolette]

Changing to pinzissi ignition completely changed the exhaust smell.

Ditto!

[JimmyC]

I am really surprised by that but am willing to give it a try. I take it you mean the new one and not Petronix (which I have)?

Does it change the timing?

Any idea what happens that makes the stench stop?

Thanks

[pcolette]

This may answer some of your questions: http://www.pinzssi.com/

I have it installed on both my 710's and they're easier starting, smoother running and much cleaner exhaust. I had the carbs rebuilt and setup by Jim L. at the same time.

[muttandjeeps]

Pinz SSI de-stinkified my last Pinz, and is the best thing going...just my .02

[63rover]

Keep in mind that misfires and backfires kill cats. The matrix collapses and plugs the pipe. If you add a cat be prepared to be very patient warming the engine up before driving to avoid the popping that will destroy a cat. Another concern would be placement with sufficient heat shielding. Likely it would need to be after the heat exchanger so as not to over heat that and before the muffler. That puts lots of heat near the batteries. Hmmm. Let us know what you decide.

One more thing. Cats also restrict exhaust flow and therefore reduce power.

Good luck.

Clive

[JimmyC]

I have been doing a bit of reading about ignition and exhaust stench. One thing that I found out is that an engine needs more advance at part throttle than full throttle to get good combustion. The Pinz does not have a vacuum advance so it does not get this advance at part throttle.

The Pinz SSI has a lot more "mechanical" advance than the standard Bosch. At 1500 RPM the Bosch fires at about 17 degrees BTDC but the Pinz SSI fires at about 23 degrees. I wonder if the stench cure is due to more advance timing.

I am surprised with how different the advance curves are.

[JimmyC]

I have installed the catalytic converter and preliminary results are good. So far I have not gotten the exhaust smells or eye irritation since installing it. I do occasionally get a smell something like burnt rubber, but very faint and it is non-irritating.

I was worried about it getting hot enough but that does not seem to be a problem. Within a mile of install I stopped to check it and there was red light coming out of the tail pipe. I then began to worry about it getting too hot, but it seemed to run cooler after that. I believe it was burning off something from the manufacturing process.

I am fitting a heat shield and another hanger, but neithe seems to be a pressing issue.

[kdiqq]

Be careful, the cat will get substantially hotter than the muffler and if your Pinz isn't running perfect, it will amplify this affect. The cat actively burns unspent fuel, so be aware it needs good space to not scorch anything.

I don't agree with this mod, but I don't need to looks like you did a good job, looks clean, and I'm glad you solved your problem! Just be careful!

Sent from my Z30 using Tapatalk

[JimmyC]

Don't you think the shovel makes a good heat shield?

RI am pretty concerned about it over heating myself. I am driving around with a big jug of water just in case. I was going two minutes at a time between checking and am up to 10 minutes. So far excess heat has not been a problem except when I first ran it. When I first ran it there was a dull red glow coming out of the pipes but it cleared up pretty quick. I think it was something put on the catalyst when it was new. I have since cooled it all the way down and ran it again with no problems.

I got some insulation for a turbocharger and am making a heat shield. Also have a better thermometer coming to help monitor the temperature.

[mopar]

PINZSSI burns cleaner because it fires on both the compression and exhaust stroke ala wasted spark hence why setting the the timing is so easy because you find TDC doesn't matter which cyl because it is fire 180 form each.

[JimmyC]

I have the SSI system but have not started playing with it yet. From looking at it so far it seems the major two differences are the multiple Sparks and much more aggressive mechanical advance. Multi spark is a well established technique to improve the reliability of combustion at high vacuum and low RPM. My Pinz does have poor combustion at high vacuum, likely due to mixture dilution with exhaust, and I expect the multi spark to help with this.

I am curious about the advance curve. Compared to most distributors the mechanical advance is pretty aggressive, particularly at low RPMs. In one way a lot more advance at light load makes sense because combustion is slower, but on the other hand retarding the timing at idle usually reduces hydrocarbon emissions. I think this is because the throttle has to be opened a little more (idle speed adjustment screw) to compensate for the retarded timing. This raises the manifold pressure reducing exhaust dilution and therefore better combustion.

I would be surprised if the waste spark(s) have much effect on emissions but I get surprised pretty regularly. It does seem like it introduces a complexity to the timing since the intake valve opens late in the exhaust stroke so you cannot fire too late.

[JimmyC]

I have had a little more time to run with the catalytic converter. Although it does seem to help, it is not 100%.

My stench problem has always seemed to correlate with engine braking followed by WOT. A typical example is climbing a hill with hairpin turns where you engine brake going into the turn and accelerate coming out of the turn. On engine braking I have seen misfires indicated on the oxygen sensor data and small backfires in the exhaust so I know combustion is problematic in this condition. I attribute the stench to hydrocarbons produced when combustion is problematic. I think the combustion is problematic due to exhaust dilution at low intake manifold pressure.

I also have had some eye irritation, probably due to NOx, but I have a harder time saying exactly when it is a problem,

I have a test hill near my house, about 1,000 feet of gain with four hairpins. I can now get up and down the hill with only an occasional faint and brief smell. I now have no eye irritation. The stench used to be notable on ths hill.

I am still getting an occasional smell off road but I have not been getting it often enough to say when yet.

My thermometer shows that I am getting temperature rise across the catalyst going down hill but not up. I think going up there is not enough residual oxygen passing through the catalyst for it to work on hydrocarbons or CO. My mixture is a bit rich for the catalyst (12.5 to 14.5) when going up.

I am surprised by how much exhaust cooling I am getting between the headers and the tail pipe. I am losing about 150 F. The catalyst would work better if it was closer to the headers.

I am not sure what if anything I will try next. Maybe try retarding the timing a bit slowing the idle speed down and then opening up the throttle idle setting to compensate. This should decrease vacuum with the throttle closed so should help combustion. I also suspect that a bit more richness at idle may help. I have one cylinder that is running like 100 F cooler than the others but so far have not been able to figure out why. It may be lean.

Not sure when I will get around to changing out to the SSI.

[TechMOGogy]

But the SSI could fix your issue better than anything you've done or are planning, plus you already own it!
I don't get it?