mikes guide to getting your car to pass smog
04-17-2010, 05:19 PM
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Join Date: May 2002
Location: California
Posts: 22,465
ive lived in CA all my life, so all of the cars ive owned have had to pass smog (even the 68 mustang), and since we have to do it so often it includes 4-5 rx7's a year. my procedure is actually really simple. not only have i not had one fail in a loooooong time, the average rotary is CLEANER than the average piston engine.
in CA we have a visual, but since i go to the same guy 5-6 times a year, for the last 4-5 years, he will let me slide as long as it passes out the tailpipe.
anyways my pre-smog check is very short at this point, and is actually the same for every rx7, not just the FC.
we have two tests in CA, the "enhanced" test, which is the IM240 dyno test, and the i guess "non enhanced" which is a stationary idle/2500 rpm test. the dyno test is by far the easiest of the two, the unloaded idle test can be tricky. this guide is geared to the dyno test.
1. i'm assuming the car basically runs ok. it needs the air pump, acv, and a converter to be there. it can flood on hot starts, it can smoke when its cold, or between shifts, we are only testing it warmed up at light load @2600-2800rpms.
2. i check the ACV to make sure it functions. on the FC its easiest to reach under the fender and make sure there is no air coming out of the ACV vent hose between idle &2500ish rpms. the alternative is you can take the hose off @the ACV, but that requires doing something, so i just reach under.
what you want the ACV to do is to put the air pump air to what mazda calls PORT AIR, http://foxed.ca/rx7manual/manuals/Training%20Manual the training manual shows why and how this works.
3. in the event that the ACV is not working, it can be for a couple of reasons. the first being the valve is bad. the ACV uses two diaphragms to operate 2 plungers, and the diaphragms fail from the heat. you can either repair, replace, or find some hardware and physically shim the valve open the way you need it to get port air.
the second reason the ACV isn't working is the control system. on an FC this is very common. ECU uses the TPS to turn on or off the two vacuum solenoids, that actuate the valves in the ACV. so the TPS needs to be good, and adjusted. also the vacuum lines NEED to be hooked up CORRECTLY. on the turbo the diagram is NOT good enough, and on the NA its easy to swap the 2 hoses in the front of the intake. if i am at this point, i will disconnect the hose @the ACV and at the solenoid and make sure it is the same hose.
4. EGR; this makes no difference, its not used during the test, AND even if it was, the passages are so small its like bringing sand to the beach. in fact ive often forgotten to install it on the car. it CAN be a vacuum leak though, so it can cause other idle problems
5. split air. this is also not used during the test. i know that big shiny pipe looks like it does something, but again, you can leave it at home, and it has no effect on the smog numbers. its popular in texas, to put the air pump right to the split air pipe. this only puts the air pump air to the rear half of the cat, while the factory PORT AIR method puts the air IN FRONT of the cat. the texas way works, but the factory way works BETTER
6. timing. timing has very little effect on HC and CO, which are the two "hard" ones for the rotary, but it DOES have an effect on NOX. advanced timing will raise NOX, and usually there is a TON of margin so its not a problem.
7. o2 sensor, @15 and 25mph the car will be in closed loop, and it will be running on the o2 sensor, so it needs to be hooked up. i've never had to go further than that, but my buddy does have FD's fail with a bad o2
8. non stock parts. in my experience the following parts have no effect on smog. air cleaner, radiator, downpipe/header, intercooler, TB mod, msd's.. so far the ONLY thing that's mattered is the airpump/acv/cat
9. CATS. you should have the main cat. beyond that its not super critical. the pre cats are mostly there to warm up quickly, and we don't test that. these cars should all pass with just the main cat.
10. PCV/charcoal cannister. i usually leave this alone, but the one car i did without it, it still passed, so it may not be used during the test? in CA they do check to make sure the fuel tank holds vacuum, but so far i havent had a problem with that
pre check. before i go, i'll go sniff the exhaust, it should feel like the air coming out of a dryer vent, it should be hot and it shouldn't really have a smell to it. if it does smell, then you might want to go and recheck that everything is working.
my smog guy likes to precheck the car before he starts the actual smog test, which is nice, cause you can see if it passes before you spend the $$. we did one car in particular that this helped a lot. it was a 10ae with a weak/bad engine, it fails horribly @idle, but at 15mph, its squeaky clean, it doesn't start on its own, barely idles, but passed the smog test....
in CA we have a visual, but since i go to the same guy 5-6 times a year, for the last 4-5 years, he will let me slide as long as it passes out the tailpipe.
anyways my pre-smog check is very short at this point, and is actually the same for every rx7, not just the FC.
we have two tests in CA, the "enhanced" test, which is the IM240 dyno test, and the i guess "non enhanced" which is a stationary idle/2500 rpm test. the dyno test is by far the easiest of the two, the unloaded idle test can be tricky. this guide is geared to the dyno test.
1. i'm assuming the car basically runs ok. it needs the air pump, acv, and a converter to be there. it can flood on hot starts, it can smoke when its cold, or between shifts, we are only testing it warmed up at light load @2600-2800rpms.
2. i check the ACV to make sure it functions. on the FC its easiest to reach under the fender and make sure there is no air coming out of the ACV vent hose between idle &2500ish rpms. the alternative is you can take the hose off @the ACV, but that requires doing something, so i just reach under.
what you want the ACV to do is to put the air pump air to what mazda calls PORT AIR, http://foxed.ca/rx7manual/manuals/Training%20Manual the training manual shows why and how this works.
3. in the event that the ACV is not working, it can be for a couple of reasons. the first being the valve is bad. the ACV uses two diaphragms to operate 2 plungers, and the diaphragms fail from the heat. you can either repair, replace, or find some hardware and physically shim the valve open the way you need it to get port air.
the second reason the ACV isn't working is the control system. on an FC this is very common. ECU uses the TPS to turn on or off the two vacuum solenoids, that actuate the valves in the ACV. so the TPS needs to be good, and adjusted. also the vacuum lines NEED to be hooked up CORRECTLY. on the turbo the diagram is NOT good enough, and on the NA its easy to swap the 2 hoses in the front of the intake. if i am at this point, i will disconnect the hose @the ACV and at the solenoid and make sure it is the same hose.
4. EGR; this makes no difference, its not used during the test, AND even if it was, the passages are so small its like bringing sand to the beach. in fact ive often forgotten to install it on the car. it CAN be a vacuum leak though, so it can cause other idle problems
5. split air. this is also not used during the test. i know that big shiny pipe looks like it does something, but again, you can leave it at home, and it has no effect on the smog numbers. its popular in texas, to put the air pump right to the split air pipe. this only puts the air pump air to the rear half of the cat, while the factory PORT AIR method puts the air IN FRONT of the cat. the texas way works, but the factory way works BETTER
6. timing. timing has very little effect on HC and CO, which are the two "hard" ones for the rotary, but it DOES have an effect on NOX. advanced timing will raise NOX, and usually there is a TON of margin so its not a problem.
7. o2 sensor, @15 and 25mph the car will be in closed loop, and it will be running on the o2 sensor, so it needs to be hooked up. i've never had to go further than that, but my buddy does have FD's fail with a bad o2
8. non stock parts. in my experience the following parts have no effect on smog. air cleaner, radiator, downpipe/header, intercooler, TB mod, msd's.. so far the ONLY thing that's mattered is the airpump/acv/cat
9. CATS. you should have the main cat. beyond that its not super critical. the pre cats are mostly there to warm up quickly, and we don't test that. these cars should all pass with just the main cat.
10. PCV/charcoal cannister. i usually leave this alone, but the one car i did without it, it still passed, so it may not be used during the test? in CA they do check to make sure the fuel tank holds vacuum, but so far i havent had a problem with that
pre check. before i go, i'll go sniff the exhaust, it should feel like the air coming out of a dryer vent, it should be hot and it shouldn't really have a smell to it. if it does smell, then you might want to go and recheck that everything is working.
my smog guy likes to precheck the car before he starts the actual smog test, which is nice, cause you can see if it passes before you spend the $$. we did one car in particular that this helped a lot. it was a 10ae with a weak/bad engine, it fails horribly @idle, but at 15mph, its squeaky clean, it doesn't start on its own, barely idles, but passed the smog test....
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