wstrohm

Our 1994 RX-7 has 72 K miles on it. The car, which was bone-stock, failed CA emissions testing, only 12 K miles after the 60 Kmile maintenance. I bought a Bonez downpipe and catalytic converter from RP and installed it last week, along with a new Bosch O2 sensor. The car failed again, but differently. I have summarized the test results in the table below.

CA Emissions Specs for 1994 RX-7 (Orange County), for year 2002:

Test ......RPM......%CO2.....%O2.....HC(ppm).....%CO ......NO(ppm)

15 mph..----........----..........---.......88...............0.52 .........1006
25 mph..----........----..........---.......53...............0.50 ..........866

Stock Test Results, 72173 miles 7/18/2002

15 mph..1841......15.0........0.4.......24........... ... 0.07...........118 PASS
25 mph..2874......15.0........0.0.......49........... ... 0.61*...........44 *FAIL

Bonez Downpipe/Cat, Bosch O2 Sensor, 72461 miles 8/05/2002

15 mph..1925......14.5........0.5.......59........... ... 0.02............37 PASS
25 mph..2921......14.7........0.0.......83*.......... ... 0.18.............7 *FAIL


All tests were run on the same machine by the same tester. Notice that although
the CO and NO measured values were greatly improved by the Bonez cat, the HC
numbers more than doubled at 15 mph and almost doubled at 25 mph, which failed
the car at 25 mph.

I have now spent over $1000 on parts. Ari has stated that the Bonez cat with downpipe should pass CA tailpipe testing, and I bought the kit with that understanding. We are now going to take the car to Irvine Mazda for troubleshooting; however, they do not guarantee that anything they do will result in passing smog (even on a stock car).

I would like to hear whether anyone thinks removal of the warm-up catalytic converter ("pre-cat") is responsible for the increased hydrocarbons, whether the Bosch O2 sensor might not be the correct type (it is a P/N 11027), or whether the problem might be due to some mistake I made when reassembling the car.

Because of a nut which was frozen to one of the studs mounting the pre-cat to the turbo outlet, I had to remove the rear turbo intake air pipe, the "air pipe and control valve assembly," which I believe some people call the "Y-tube," and all the associated vacuum hoses and inline air valves in the air intake system.

I put it all back together in accordance with the 1994 Mazda RX-7 Workshop
Manual, using new gaskets and O-ring where indicated. I also bought a
right-angle rubber hose from Mazda to replace one that had hardened into
"plastic," and a new downpipe-to-turbo outlet metal gasket. I have torque
wrenches, and torqued everything (where it was possible). The Bonez downpipe is
wrapped with a layer of Thermotec insulating wrap. Also, the car runs and idles very smoothly, and is quiet, but it seems down on power relative to performance before the work I did, which is a mystery to me.

This car is due for registration on September 12. I would appreciate as many suggestions as anyone can offer.

Thanks!

---- Bill

mjw

iTrader: (1)

I know there will be some people who disagree with me on this, but I say that testing without the precat in place will affect your emissions testing results. I find it hard to believe that running the precat makes no difference. Here is my theory, your CO went down because you installed a new cat, but your HC went up because you aren't running the precat anymore. Test with the precat back on and the Bonez HF cat, along with some other smog test tips possibly.

Matt

rynberg

Please post your testing conditions. With the pre-cat off, the car needs to be FULLY warmed up. As in a 1/2 hour of decent to hard driving to get the main cat fully warmed up. Also, 12k is a lot of miles for spark plugs. They should probably be changed. Also, when you put the Bonez hi-flow cat on, was the air pump hooked back up?

mjw

iTrader: (1)

Rikki:

I am sure you are aware of this, but passing emissions in MD and passing emissions in CA are two different things. I know of multiple people who have not passed emissions in CA w/ a downpipe, putting the precat back on for the test can't hurt anything. Try running some denatured alcohol in the tank as well.

Matt

hapa

Bill, emissions in CA are tricky. First are you running your airpump into your Bonez cat? Second, why did you change O2 sensors? I've known a few FD's that have passed smog without the Pre-Cat. I wouldn't think it's the reason you failed. Why did you change to a downpipe and Bonez CAT? Was it clear that the stock cat. was bad? Also, why did you change the 02 sensor?

Plugs make a huge difference in emissions. I keep a brand new set of BUR7EQP's just for SMOG testing. Make sure you run the 7's in the leading, the reason Mazda went with 7's versus 9's is for emissions. If I were you, I would put all of your stock equipment back on (as long as it is in working condition), and put new leading plugs in. Next I would clean out your purge tank (small black plastic tank below the intake elbow). Make sure the car is hot during testing. Go for a long drive before the test and when you pull into the station, leave the motor running all the way through the test. Post some more information for your car.

eric

maxpesce

I passed CA emissions (Test Only) on first try (July 01) with DP, STREETPORT, and Stock (30k+mi OLD) Cat. The test was done approx 1000 miles after my rebuild.

bad PLUGS will affect HC results - put in new ones just prior to the test also run the car HARD for 10 Min and do NOT let it cool down before the test - check for excessive fuel pressure at idle and/or Leaky injectors

Mr rx-7 tt

iTrader: (5)

My brothers car with a PFS computer, dp, cat back and intake passed as a ZERO emmission vehicle in California.
I say put the stock cat back on and make sure the car is warmed up. After it passes put the bonez back on..only a 4 bolt 15 minute job..

gfelber

I've passed emissions in California, Georgia, and Washington using the same Bonez main cat and no pre-cat (yeah, I move around a lot).

The increased HC is no surprise, ceteris paribus, given less restriction. The pre-cat is good for warm-up. No pre-cat = poor warm-up, but otherwise should not affect warm emissions results. Ideally, you want to get the cat as warms as possible. Cold start testers don't often allow you to do this- unless they're extremely busy and don’t care

Seems indicative of incomplete combustion or burning of oil. Things to check are plugs, plug wires, catch "can", and any other leaks. I'd seriously advise against using plugs with 12K miles. And make sure you have a nice pre-mix free tank of premium.

Gene

RonKMiller

New plugs, oil change and fresh, full tank of gas. Nothing to loose. Don't forget anti-sieze on the plugs.

"If you hear hoofbeats, don't go looking for zebras".

GoRacer

iTrader: (2)

Yeah, your plugs are too old. You should have brand new plugs for testing. They will go bad in 8k mi. Don't go to Irvine Mazda for testing, besides they are over priced. The dealer will let your car sit for hours before touching it. You want to go to one of those drive through test only stations. It should not take longer than 15 before they test you and you car will still be hot. You can use 5W-30. I beleive that's the more environment friendly one. There is bottled stuff you can get at the auto store to put in your gas tank that claims to help pass and add some octane boost. Don't put premix oil in the tank though. I was told by my mechanic not to change the O2 sensor unless you get a code that it's bad. I don't know how well the Bosch compares to OEM. If fuel filter is older than 15k mi then change that to. If you can lift the car up, it would be alot easier to change the main cat then precat.

wstrohm

Thanks for all your replies. It seems there is disagreement about whether the pre-cat is needed after warm-up. To answer some questions: the O2 sensor was changed because it was the original with 72K miles on it and the car failed with it on, so I thought it would be a good idea. The oil is relatively fresh (500 miles), I am running CA 91 octane gas, and the car was as warm as it ever gets. No high-speed driving, but the car was rolled in almost immediately after a 3-mile run at street speeds. Water temp was normal. The tech runs the dyno at 15 mph first, with no fan blowing into the radiator, in order to warm up the engine, and both the stock and Bonez 15 mph tests passed. The 25 mph test failed both in stock form and Bonez form, but as you see, on different parameters. I believe there is nothing wrong with the cat or the O2 sensor.

I did install the secondary air path onto the Bonez cat per their instructions. I did not check to be sure the secondary air pump is working. Could that be a problem?

I didn't understand the comment about "the upgraded EGR gasket." I know what exhaust gas recirculation is, but why would a gasket make more or less smog??? Doesn't EGR affect mainly NO? And the car is fine there.

I did note some oil in the turbo output tube, but that would have been present in the stock configuration as well.

I will take the advice on new plugs (and wires? Sounds like Miata advice!) and give it another try. However, remember the stock car passed HC with these plugs and wires. I am sorta shocked that you folks think 12K miles on a set of plugs is a lot. Guess I'm spoiled by piston engines.

I sent basically a duplicate of my original post above to RP; hopefully they will have some input for me.

Thanks again for your time and thoughts, folks.

---- Bill

GoRacer

iTrader: (2)

I don't think that's enough to warm up the car. Yes the needle will say warm but it takes a good 10 min before it feels warm...or go one exit back and forth on the freeway.

RonKMiller

Warm means at least 20 minutes of driving. If you go with new plug wires (and it IS time to get them at your mileage) get Jacobs, they are stout, well made and relatively inexpensive compared to some of the hyped stuff out there. Yep, the plugs really do burn out that fast. One of the downfalls of having 1.3 liter make 255 hp. Make sure you replace with plats - the non plats are worthless. You should be fine on the oil with only 500 miles. I now this sounds elementary, but is your air filter clean as well? It all adds up..........

Good luck and welcome to the wacky world of rotaries - where everything you've ever learned about boingers is about to be turned - around in circles!

(If all this does not work you could have some bad check valves or solenoids. The emissions system is a bear.......)

wstrohm

GoRacer & Ron,

Driving time was just about 20 minutes before test, stop & go. Air filter element has 9205 miles on it.

Are the OEM wires not good (a la Miata)? Who sells Jacobs wires?

If plugs/wires do not fix the emissions, it looks like the pre-cat will have to go back on. I don't want to do that, since this website says it is bad for reliability due to high underhood temps. But if that's what it takes to pass CA smog, that will have to happen.

Thanks again!

---- Bill

Nathan Kwok

I'll bet its the plugs and/or wires. Everything else seems ok but make sure the airpump is engaging properly. Also, running alcohol is practically a guarenteed way to pass, you could probably pass with NO emissions equipment if you run a lot.

GoRacer

iTrader: (2)

code 16 = bad EGR

FD Racer

I read all the above post very quickly, so I may be repeating, but from what I did see.... New plugs, for sure. Pre-cat, dont worry about it, I passed with a downpipe and the stock cat (70k miles). Clean air filter, good. Check to see air pump works & hooked up.... Your oxygen levels were low suggesting it was not working corectly. DO NOT go to a test only station unless you have to, they are alot more **** than the average gas station or small repair place that perform smog test as well as other business. Also, what gear was the tech guy in on the last run, make sure he doesnt rev the motor too much on the 25mph run so the airpump doesnt shut off (~3000rpm)

wstrohm

GoRacer,

With "TEN" and "GND" jumpered in the diagnostic connector and the ignition ON, the Check Engine light is on steadily; there is no flashing. Good or bad? Under normal running, it is off. On my Miata, with TEN and GND jumpered and ign ON, the Check Engine light is off when there is no problem. (??)

FD Racer,

Air pump is hooked up; Mazda manual says it should "be off above 3250 rpm." Note in my table that the 25 mph test on the stock version was run at 2874 rpm, and on the Bonez version was run at 2921 rpm. I just ran a test and the pump shuts off at about 3200 rpm on the tach, so I think it was running when both smog tests were done. That was a great tip, however, and I thank you!

Is there a "failure mode" of the rotary where one of the two spark plugs in a rotor chamber fails and the other one keeps working? How does that affect running? Even though the car runs smoothly, it seems down on power; could say a Leading plug be failing such that one rotor is running only on its Trailing plug? I would think that either being bad would affect emissions, but wouldn't it also cause both loss of power AND rough running?

I have to use a Test-Only smog station since I was so directed by my registration renewal form. Don't know why.

Anyway, I am getting new plugs and wires tomorrow. Once again, thanks for your responses.

---- Bill

wstrohm

We took the car into Irvine Mazda for new plugs and wires. The tech saw my smog results and looked at the car. He checked ignition operation and said the plugs and wires are fine. Basically he did not want to change plugs or wires and said it would do no good. He also said the Bonez cat converter is too small relative to the stock cat and that I should put the pre-cat back on the car. My inclination is to reinstall the pre-cat, leave the Bonez cat in place and have the car retested. From what some of you have said, that might work; others will disagree, I'm sure. After spending over $1000 so far, I'm not inclined to shell out another $1600 for a new, stock cat even if Ari will take back the Bonez stuff. Any more comments?

---- Bill

GoRacer

iTrader: (2)

Told ya not to go to Irvine Mazda. The is one in Laguna Hills. Did they charge you labor for the plug & wire replacement and not even replace them?

If he had the F'n plugs out, he "SHOULD" have replaced them!!! The wires maybe not, but they are less than the F'n labor, damn!

It would have cost you less to pay to have the pre cat & main cat installed and them have the DP and Bonez installed after the test!

For that kind of money you could have went to Tri-Point. I beleive they do smog tests there, unless i'm mistaken. You could have also had a real mechanic figure out what's wrong.

wstrohm

GoRacer,

Maybe you misunderstood me. I haven't spent anything at Irvine Mazda yet. It would have been $280 for plugs and wires, but since the tech didn't install them, the cost of having him look at the car will be quite a bit lower. The $1000 I referred to was for the Bonez stuff, plus Mazda OEM gaskets & hoses, plus two smog tests so far. I don't know whether he pulled the plugs or not; I forgot to ask. When he said they were "fine" I assumed he had run the car on a scope or some sort of ignition tester.

---- Bill

GoRacer

iTrader: (2)

Oh whoopsie I appoligize to Irvine Mazda.

Call Tri-Point and ask if the do smog tests. For some reason I thought I rememberd reading they do. If your car fails, then they can figure out why.

I would replace the plugs anyhow.
Replace the fuel filter.
Get a bottle of Royal Purple fuel inhector cleaner
or Mazda fuel injector cleaner or Red Line.
Replace or clean air filter.
Get a bottle of octane boost or some race gas
Get a bottle of "smog test pass stuff"
(don't know anything about the alchohol the other guys mentioned)
Install the OEM cat yourslef (only temporary for the test)

You should get a 2nd test free when you fail the 1st. If not, go someplace else. So if you fail, install the pre-cat before the 2nd test.

If it still doesn't pass, then it sure wasn't the Bonez stuff.