Pele

iTrader: (28)

You're running rich as ****. Lean it out a little and try again. The second you see a single PPM in the NOx field, pop it back rich again.

funkjaw

iTrader: (3)

Is this an ASM (dyno smog check) or a idle smog check?

rx7man13b

elaborate please. I got a cat welded on and im going to go thru with 1gallon of denatured alchohol mixed with an 1/8th of a tank. I'll post results

rx7man13b

Failed again with the new cat and alchohol


HC dropped from 952 to 580
CO dropped from 7.1 to 3.8
NOx stayed at 0
Now im going to run the air pump directly to the cat and try again. Should i make some vacuum leaks? Try a different premix?

funkjaw

iTrader: (3)

Well first of all you are going to need new plugs, they are definately fouled to all heck. Second the air pump should already be running into the cat. Third you can lean it out quite a bit because if the limits you posted are correct, you will never create enough nox to fail your emissions test no matter how lean it is running. Just lean it out until you start misfiring a bunch then back it off to smooth it out. You should pass smog. I am a smog tech here in california and your limits are twice as high than over here which is lucky for you.

rx7man13b

the smog pump has been off the car since i put the carb on. I thought i had a chance with alchohol and a cat. The plugs are fairly new but ill change them if it will make a difference. How can i lean it out? smaller main fuel jets? Its a Mikuni 44 carb. Do u think i just had too much premix in there? Thnks for the response.

PercentSevenC

Smaller pilot jets. The pilot jets affect both idle and cruise.

rx7man13b

im dum

funkjaw

iTrader: (3)

If you want to make the biggest difference for smog on an Rx7 in my experience is making sure the air pump is working correctly. A working smog pump can bring numbers similar to yours down to practically nothing. I have watched this many times by just engaging and disengaging the smog pump while running in diagnostics mode on the dyno.

rx7man13b

Mine will be pumping directly to the cat, not the stock way. Shouldnt that make it work even better? I know nothing about emmisions lol. New plugs, more alchohol and airpump into the cat. Ill post numbers ASAP. Thanks guys

RotaryRocket88

iTrader: (7)

Most of the air from the pump is directed into the exhaust ports, where it mixes with the exhaust gases prior to reaching the cat. The air that travels through the split air pipe is much less, and it also happens to end up about halfway down the cat itself. A car with a functional stock emissions system should have a better chance of passing than one with a rigged air pump.

That being said, I know some have passed smog by rigging the pump directly to the split air pipe, so you can give it a shot, but you should also drive very easy while it's set that way. Under heavy load, there may be so much air entering the cat that it overheats and gets damaged. Normally, the ACV solenoids prevent air from being pumped into the cat under such conditions.

Also, it's been mentioned twice now, if you're only doing an idle emissions test, adjust the variable resistor. The FSM or a haynes manual will tell you how to do it properly. Turn it as far lean as you can without making the engine idle rough. It will lean out the mixture and drop your numbers.

Pele

iTrader: (28)

I missed the part where you're running a carb.

I hate carbs. You can't connect a laptop or adjust any resistors to change the mixture. You've gotta play with jets and venturis and ****.

RotaryRocket88

iTrader: (7)

I missed the carb statement too. You might go to the 1st gen section and ask about carb tuning there. Very few in this section use carbs.

Pele

iTrader: (28)

1st gen was Nikki carbs stock.

Others that have been commonly used aftermarket are Holley (Modified by RB or standard with premix...) Weber DCOE, Hitachi (I think old school rotarys used some Hitachi carbs and I think the Nikki carbs are based on a Hitachi design.) as well as the Mikuni side drafts.

I'd ask either in the Old School or Gen Rotary, as it's not 1st gen specific carb... Though a lot of those guys do sometimes run aftermarket carbs.

Hyper4mance2k

iTrader: (40)

1 dont premix the day of the test.
2 just have any exhaust shop weld in the biggest one you can find.
3 hook the airpump to pump directly into the cat. not into the port actuators as they are infront of the cat.
4 add 4oz per gall on of denatured alcohol to the mix.
5 make sure your car is really warm drive it for at least 30 minutes before teh test.

if this won't do it then you need to tune the carb.

rx7man13b

Thanks for the response. Only 4oz per gallon of the alchohol? When i went thru the 2nd time, I was on empty and added about 3/4 of a gallon.

flamin-roids

Lean out as much as you can, use 2 magnaflow high flow cats (have them make a custom pipe) and make sure you're tuned up nicely. Replacing the fuel filter, air filter, oil change etc. The magnaflow cats I used to pass are about $55 a piece and with exhaust work it ran me about $150. Also i hear taking the gas cap off helps too. As long as your friend will let it slide.

rx7man13b

How much denatured alchohol is too much? Ill bring new plugs with me and change them there right before the test. Air pump will be run directly to the cat for the test then pulled off agin. My friend will let me add some vacuum leaks should i loosen the header and make an exhaust leak there too? I have till the 26th to pass so my time is running out.

coolmike711

iTrader: (7)

Did you ever pass the test?
I need to do mine this month. I have a bonez high flow cat and no air pump on my 87 TII.

jjwalker

Woah, how the hell was NOx so high? Rotaries aren't really known for extremely high NOx emmisions like that due to thier elongated combustion chamber.

You'll also mess that cat up without some sort of oxygen source being pumped into it. On a two stage converter, the NOx catalyst is on the front side because it needs a lack of oxygen to work, then the air feed tube, then the CO/HC portion, which needs oxygen to burn. That is why there is an air tube in the center of the cat.

ericgrau

iTrader: (1)

A stock cat or a bonez performance cat should work. In both cases you better not be running too rich or too lean or it'll burn up the cat over time. W/e the cat you use, it needs to be able to handle very high temps or the insides will melt.

Most premixes burn pretty clean as long as you don't use an excessive amount. I think any TCW3 stuff will do. But if you want crazy clean stuff, try AMS.

No additives (except maybe alcohol), just use good quality gas like Chevron, Shell, 76 or Texaco. Use low octane, unless your car needs high octane.

An exhaust leak won't affect the concentration of pollutants, only the total amount. They measure concentration. It'll also be crazy loud.

There's a table in the FAQ that tells you what your results mean. If your HC and CO are high but your NOx is low, then you're running too rich or need to pump in more air. If you're not going to retune it then alcohol should lean it out. Drive gingerly and get rid of it ASAP after the test, b/c if you're running too lean and hit the throttle hard you could pop your motor. And in general I'd recommend the honest way using a good tune. Then you're always kosher, there's less to worry about, etc. And if you plan on keeping that cat bolted on for a long time it's necessary to avoid ruining the cat.

The air pump is essential. You'll probably have high CO and high HC but low NOx w/o one like the OP, from having too rich of a mixture at the cat. In fact you might be burning out your cat without one for that reason. Then you'll need an air pump AND a new cat. Again the FAQ has a table that you can compare your smog test results to, to help you find any problems.

coolmike711

iTrader: (7)

my brother in VA passed emissions on a 86 n/a with rb headers, bonez high flow cat and air pump, but the split air pipe was not connected to the cat. the split air pipe was blocked off.