i passed smog (3rd attempt) last week with headers, exhaust, and the help of shad @ driving ambitions. Give him a call if you want to pass it legally
thats where i'll be taking mine if it doesn't pass.
CA smog is out to get us
- Thread starter Bruce in SD
- Start date
thats where i'll be taking mine if it doesn't pass.
Hi An,
I cleaned the air temp sensor and just received new spark plugs so will install this weekend and run the car to get some miles on her. I am thinking about also cleaning the EGR valve before I try to get a smog test again since it will be my third try. I also had my Porsche 928S4 pass at another station near work so think I will try that station vs. the one it failed at. Will keep you posted bu possibly will try before the 4th of July weekend.
Correct, I believe that any car produced previous to 1976 is exempt. That is why all these rat rods are being built, no CARB and they can spew what ever they want. CARB is so useless.
This table shows desired EGR valve lift versus rpm and load for a 91 NSX M/T
This table shows desired EGR valve lift for a 91 NSX A/T
The EGR is pulse width modulated by the ECU based on this duty control map. The value refers to the desired amount of physical lift of the valve which is self-calibrated for varying vacuum levels by the input of the EGR lift sensor. So the original poster was correct in assuming that M/T cars have a harder time passing smog than A/T cars for this reason alone.
Going by the tables, testing an M/T car in 2nd gear at 1500 RPM is almost a guarantee that it will fail. Assuming that the dyno is free wheeling (no load) the EGR valve is simply not commanded to lift by any significant amount - 5-16% isn't going to cut it. Maybe you can present your tester with this evidence to persuade him to test in 1st gear. Alternatively, you could adjust the parking brake to apply a slight load to the rear wheels during the test. As a last resort this table is relatively easy to modify.
-Matt
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Hi All,
I changed my spark plugs and cleaned the intake air temp sensor which was pretty oily before cleaning and then ran a full tank of premium gas with a bottle of seafoam. Then refilled gas with Chevron premium and drove for about 15 minutes (not spirited since it was rush hour so went up and down Central Expressway and then took it to Friendly Smog in Santa Clara (Jimmy- owner, Tony- tester) and it passed. Here are results as it was still pretty close:
2014 3rd Results- Passed
rpm: 1542 HC: 22 CO: .04 NO: 613 (vs. last measurement of 909 and 1073)
rpm: 1730 HC: 22 CO: .03 NO: 451
Note that I used a different Smog Test station this time since I had luck with them with my Porsche 928S4 also without issue. So not apples to apples as I did not want to go again to Century Automotive in Santa Clara again as it failed twice miserably on the NO.
I changed my spark plugs and cleaned the intake air temp sensor which was pretty oily before cleaning and then ran a full tank of premium gas with a bottle of seafoam. Then refilled gas with Chevron premium and drove for about 15 minutes (not spirited since it was rush hour so went up and down Central Expressway and then took it to Friendly Smog in Santa Clara (Jimmy- owner, Tony- tester) and it passed. Here are results as it was still pretty close:
2014 3rd Results- Passed
rpm: 1542 HC: 22 CO: .04 NO: 613 (vs. last measurement of 909 and 1073)
rpm: 1730 HC: 22 CO: .03 NO: 451
Note that I used a different Smog Test station this time since I had luck with them with my Porsche 928S4 also without issue. So not apples to apples as I did not want to go again to Century Automotive in Santa Clara again as it failed twice miserably on the NO.
Thanks. Load off my mind with the bs CA is putting our cars through. A note from Tony the tester was that NO is usually affected by the CATs so he was surprised that it passed with spark plug and cleaning of intake air temp sensor. So possibly better gas and different smog station made a difference ???
True enough, which is why you want them hot. A dirty IAT sensor screws up the air/fuel mix so badly that the cats can't do enough.
Just smogged my car and posting it here to provide more data points. These are the measured values. The average values are much lower. Which value does CA use to determine if you pass or not, measured or average values?
My NO reading is increasing every year so does that mean my cats are going out?
My car is a '91 74k miles, 6 speed.
rpm: 1673 HC: 52 CO: .12 NO: 361
rpm: 2862 HC: 49 CO: .08 NO: 400
My NO reading is increasing every year so does that mean my cats are going out?
My car is a '91 74k miles, 6 speed.
rpm: 1673 HC: 52 CO: .12 NO: 361
rpm: 2862 HC: 49 CO: .08 NO: 400
I just smogged my car yesterday and it barely passed, 92 nsx with 87k miles NO was at 750 for the low rpm test... max was 785 i believe.
I just passed - barely... For me the "too close for comfort" was HC -- 15mph - MAX 80 - I was 80.... 25mph - MAX 62 - I was 61.
Car runs PERFECTLY!
EDIT: Found the answer.... no parts needed. The Comptech headers cool off too fast -- the cats need to be REALLY, REALLY HOT. I thought I had gotten them hot enough, but the smog check guy just dicked around too long before running the tests. FYI!
Car runs PERFECTLY!
EDIT: Found the answer.... no parts needed. The Comptech headers cool off too fast -- the cats need to be REALLY, REALLY HOT. I thought I had gotten them hot enough, but the smog check guy just dicked around too long before running the tests. FYI!
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Below are the results for my '93, running on 17/18's, and as hot as I could get her, no check engine lights. My smog mechanic recommended checking the following, in this order:
- Check/Clean IAT Sensor (I use a comptech oil filter)
- 02 Sensor (unlikely if no check engine light supposedly)
- New Spark Plugs (I may not have changed mine ever, currently at 86k)
- Change to OEM wheels (his strongest recommendation as engine speed is too low)
- New Cats
Any other recommendations? If it comes down to purchasing oem wheels which I currently do not own, I may be inclined to get short gears (plus clutch :/), depending on how much it will all cost.
15mph/1520rpm - 25mph/2359rpm HC 224 - 51 CO 0.69 - 0.07 NO 1278 - 102
Test #2 : 15mph/1516rpm - 25mph/2385rpm HC 250 - 80 CO 0.75 - 0.17 NO 2041 - 257
Harry, my smog from two years ago was like yours, barely passed. Not sure what changed...
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wow those numbers are off the charts....bad 02 sensors don't always throw a check engine light... Would be good idea to change plugs... I don't think wheels matter cause i ran 18/19 on my smog check... My only high number was nox... Everything else was within or below spec...i'd clean the iat for sure...
That was my second test, last week I got these numbers from a different station, interestingly 25mph passed. Could there be such a variation between shops, the cats were equally hot for both tests:
Test #1 : 15mph/1520rpm - 25mph/2359rpm HC 224 - 51 CO 0.69 - 0.07 NO 1278 - 102
Test #2 : 15mph/1516rpm - 25mph/2385rpm HC 250 - 80 CO 0.75 - 0.17 NO 2041 - 257
I think I'll go ahead and clean the IAT, get new spark plugs, and maybe new cats and see how she does...
Tai:
See the edit to my post above yours.
Cat heat may not be your only issue, but could be an important part.
Smog stations are supposed to calibrate their equipment every day or two.... so that shouldn't be it.
See the edit to my post above yours.
Cat heat may not be your only issue, but could be an important part.
Smog stations are supposed to calibrate their equipment every day or two.... so that shouldn't be it.
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SHE PASSED! Thanks for the tip Harry, last time I took her in I had to wait after warming her up and let the car idle for 25 minutes, which clearly wasn't enough to keep the temps up. This time I got her really hot, hopped on the dyno, and she passed below average on HC, CO, and above average but comfortably below max for NO. I also cleaned the EGR, IAT, and installed new injectors, so thankfully I can stop sweating over this for a couple more years.
One more thing, I heard that they may consider exempting OBD1 cars in a few years in Ca, hopefully this rumor is true!
One more thing, I heard that they may consider exempting OBD1 cars in a few years in Ca, hopefully this rumor is true!
I'm Theo a nsxprime member and also own a smog mechanic shop in Modesto CA. I can give honest advice and honest smog inspection. I will not do any illegal smog inspection so please don't ask but the least I can do for nsxprime memeber is give them the best advice I can.
Smog dynamics
830 Kansas ave c-3
Modesto ca 95351
209-529-1975
Smog dynamics
830 Kansas ave c-3
Modesto ca 95351
209-529-1975
It was time for my 29K mile stock '92 to get tested. It passed no problem. The NO was amazingly low. Only the HC at the 15mph test was close to the max but changing the plugs may lower that (it did on my friend's '91 that repeatedly failed this part of the test).
Vytas: those are clean levels, I bet you didn't know the technician, correct?
I went to Frontline Auto Performance based on a recommendation from a friend who had his NSX tested there. Andrew was the tech there.
Another option...all you NSX owners can move into Mariposa County. We are smog exempt. I'm enjoying it up here in the boonies---deep into Redneck country.
