Yeah so my car failed emissions on saturday even though i was so sure i was gonna pass with the new cat. So heres the deal i have the same exhaust setup as Scott 89t2 except for the fact that my split air tube was mangled beyond repair so i went without my airpump. Now my question is is it possible to pass without the air pump functioning? Also i get the suspicion that my o2 sensor is failing because my afm guage gets really random readings every now and again (ie the whole thing will light up) and i know this could be a pretty major factor as well but im just curious as to how much the air pump does.

Ill post the inspection report but here are the numbers:
HC: Limit-0.800 g/m Reading:3.1322
CO: Limit-15.0 g/m Reading:21.345
NOx:Limit-0.4596 g/m Reading:2.00 (at least i passed one )

 

when your afm lites up like that it should just be the closed loop thing the ecu does...im not 100% on why or what its going but from what i understand its pretty normal....

 

No its different than the closed loop thingamabober youre refering to, at least i think so. I think you mean where it sweeps from side to side when you keep it at constant revs. But i mean every light on the guage lights up at the same time and stays on for .5-1 seconds.

 

Wow, run some alcohol through that thing and try again! I never knew Milwaukee had emissions testing, that must suck.

 

Oh believe me it does especially because i was so sure that cat was gonna pass me, well on the bright side i saw a sign at a gas station right by my house that says free emissions testing. I bet they are going to rethink that after i come in two or three times =) Forgive me for not knowing but what would running alcohol through do?

 

Lower your emissions considerably, though make your car run like crap and make it run hotter. Search and you'll find a bunch of info

 

you need the air pump to bring air (oxygen) into the cat and/or exhaust ports. Without it, the cat is likely to fail quite soon.

For more info,
you can have a peek at my webpage (in sig) under emissions->secondary air

or do a search in this very forum

Hugues -

 

Why would they sell a cat without an air port if its just going to fail soon? Its not a stock btw if tahts what you were assuming.

Also nice informative site, i now know that it probably isnt be the egr because i passed NOx with flying colors.

 

NOx is usually not an issue even without an EGR on the 7.

Well, all I can tell you is that you need air for the cat to perform.

About why you need an air pump:

What follows is a general statement for all kind of cars (not just the 7)

you need air to be injected into the exhaust for 2 reasons:

1) allow combustion of HC past the combustion chambers (that is in the exhaust ports)

2) allow (fresh) air to reach the cat for proper chemical reaction

The mazda engineers chose to have a dual system (air goes to exhaust port or directly to cat via split air pipe depending on rpm and some engine conditions). I would think that back in the day they thought it was an "optimal" setup (and maybe it still is today).

Hugues -

 

Yes, as above, you need the air pump. Just passed Jersey emissions with flying colors ('89TII). Bonez DP, Bonez hi-flow cat and air pump operating.

 

OK well thanks for all the suggestions im going to replace the o2 sensor and take that gas station up on its free emissions test, if it fails again I guess ill have to order a split air tube and a few other parts.

Also just one more thought, is there a break in period for cats? Because i took the emissions test the day after i got the cat welded together so it maybe had 30 miles on it.

 

bumppp

 

cats usually smell pretty bad when they're new but I don't know about the effectiveness. You also want to make sure it's good and hot. Flog the crap out of the car for a while and roll into the testing station all hot, it should help.

 

yep, run the car hard before you get the test and don't shut it down, if they aren't ready for yu just let it idle so they stay nice and toasty. they have to remain hot to work and thats why they need that air injected, more oxygen = more heat inside the cat leading to a better chemical reaction. I passed my S4 w/o a split air pipe and one 2.5 inch cat located pretty much directly under the driver (maybe a tad more downstream than the stock location). I had the car idling for about 20 minutes waiting for the test. Come to think of it I've passed NY emissions every time w/o a split air pipe, I've always had it removed w/ all my exhausts on this car. One year I actually had the car run zero hydrocarbons without a split air pipe (I do not know how but I swear it happened, on my first motor). The past few years I've passed on the emissions dynos, not just the sniffer. The year I pased w/ no HC's it was just a sniffer and my AFM was leaned out a bit (NA FC's run RICH). If everything else is in good shape in your motor/emissions equipment you should pass if the cats are hot.

 

Yeah im pretty sure my car is running really rich but i also think the new o2 sensor might help this a bit. But good to know it is possible to pass without the air pump, so ill just keep trying.

 

I doubt the o2 sensor will help you any, it's basically just there for 5th gear and closed-loop mode.

 

Does the cat knock down the HCs? for some reason I thought it was only for the nox. I can't pass either airpump and cat installed? Do cats just stop working over time even when they are not clogged? Mine's not clogged but the HC are 2x the limit (ie 4g/m on a limit of 2). Is that the kind of reduction you can get from a new cat (88NA). Sorry for highjacking your thread but I thought it was related.

 

It's the opposite. NOx is controlled by EGR. All EGR does is pipe some exhaust back into the intake, which causes the intake charge to burn at a cooler temp. Rotaries tend to not have a problem with this (The flame front in a rotary engine moves slowly compared to a piston engine) --this is how they got away with removeing the EGR from the S-5 motors.

HC and CO are controlled by the cat, mixture and ACV.

If your ACV is Malfunctioning, you can just run the airpump directly to the cat via a piece of hose attached to the split air pipe --bypassing the ACV altogether.

Since you said you don't have a split air pipe, here's what I would do:

Your cat should have a pipe sticking out for the split air pipe. The split air pipe connects with a flange (unless some dipshit cut off the flange) Now become that dipshit, cut off just the flange, and attach the rubber hose you ran from the air pump to the pipe from the cat.


If your car is a series 4 NA, your 5th and 6th ports will now be inop (which it sounds like they already are if the SAP is crushed) causing a noticable decrease in high rpm power.

Do a search on 6ports to find out how to get em working again.

 

Actually, an S5 NA would have inop ports with this setup as well. The S-5 needs air pump pressure to work both the VDI and the 6P.

Even still it should get you through an emmissions test...

 

nice i know the guy thats inspects mine!! just pay him $30 and throws the sticker on!! easy for me..... hehehe!! : p