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View Full Version : Car fails emissions test in TTC, then passes in sequential, wtf lol.



KevinB6876
08-22-2005, 06:18 PM
Supra failed smog. I was surprised to say the least. I suspected TTC was the culprit because of reduced back pressure in the exhaust producing better cylinder scavenging and more exhaust gases. Spent 5 mins and set it back to sequential, passed with flying colors. The 94 failing number dropped to a 54 passing number, almost half, just by going back to sequential turbo operation. I'm surprised TTC fails CA smog.

The only explanation I can think of is that TTC reduces back pressure in the exhaust at low rpm's because there is no primary turbo spinning. By reducing the back pressure in the exhaust at low rpm's with TTC mode, the engine gets better cylinder scavenging of residual exhaust gases and better volumetric efficiency at low rpm's. By getting better cylinder scavenging of exhaust gases and better volumetric efficiency at low rpm's, the engine produces more exhaust gases and therefore more emissions, and therefore fails emissions testing.

With sequential mode, there is a primary turbo spinning and increasing back pressure in the exhaust as well as muffling exhaust noise. In sequential mode, with exhaust back pressure increased from a primary turbo spinning in the exhaust, the engine gets worse cylinder scavenging of exhaust gases and worse volumetric efficiency and therefore produces less emissions, which passes a smog check.

I don't know how the hell PHR is gonna make a single turbo kit that passes a CA emissions test and gets a CARB exemption order # when the car in TTC mode, which acts like a single, won't pass emissions. I am starting to think a CARB exempt single turbo replacement that passes CA emissions might be bullshit because the car won't even pass emissions in TTC mode. But if PHR can do it, more power to them. I'd just be surprised if they could do it, since the car doesn't even pass in TTC mode.

Fucken smog station didn't even care about my illegal adjustable bleeder valve on the wastegate line and illegal HKS intercooler piping. I guess they let small shit slide here and there, and only trip on big shit. They didn't even ask me for a CARB # for the intake (which had a CARB # I was prepared to show them), and this was a CERTIFIED CALIFORNIA TEST ONLY CENTER. Damn joke. Good for us I guess. They did however, check for a CAT by looking under the car in detail lol. He was surprised as to why the car failed. Then when I brought it back an hour later for retesting in sequential mode, he was surprised that the car passed no problem and asked me wtf I did. I told him it was a vacuum line, and he was like jesus christ which vacuum line was THIS that made the difference between pass and fail? He was like that's one hell of a vacuum line!! lol. Anyways fuck the world.

carendt242
08-22-2005, 06:45 PM
i passed in TTC w/o a problem. which gas did you fail?

if you failed in TTC, something else must be wrong. what were your overall numbers? in both? vs legal thresholds?

Importsupyours
08-22-2005, 10:36 PM
which TTC method passed and which failed?

RSA Supra
08-23-2005, 10:36 AM
Interesting.

KevinB6876
08-24-2005, 02:29 AM
i passed in TTC w/o a problem. which gas did you fail?

if you failed in TTC, something else must be wrong. what were your overall numbers? in both? vs legal thresholds?

The failed test number was 97 for "HC (PPM)" at 15mph, I believe "HC (PPM)" means hydrocarbons. The max allowable is 84. This was in TTC mode.

Then in sequential mode with a reset ECU, an hour later, this same "HC (PPM)" at 15mph dropped to 56. Again, the max allowable is 84. This was in sequential mode and was a pass.

KevinB6876
08-24-2005, 02:30 AM
I thought I'd also mention this was done at a CA certified test only center.

KevinB6876
08-24-2005, 02:39 AM
which TTC method passed and which failed?

Mine was the "5 minute TTC" from the New Zealand supra owner's website.

carendt242
08-24-2005, 12:38 PM
what were your other numbers? for both tests? they all work in tandem; seeing 1 number doesn't necessarily help.

TRD94JZA80TT
08-24-2005, 04:10 PM
What's up kevin, nice write up. I still think some if not most supras should pass in ttc, but who knows definately, what I was thinking is that may be your cats weren't warmed up enough to do its job the first time and your car was running a little on the rich side in ttc. Usually if you run your cats hot like above 300degrees, it really affects and reduces the hyrdrocarbon parts per million. If you have all the 5 readings/numbers, we can try to figure out what happend and what did what. My car is in permament ttc, and I don't want to have to, you know, do the dirty. But never the less thanks for givin me the heads up on a thing like this. Lateron man

KevinB6876
08-24-2005, 06:23 PM
Here are ALL the numbers for both tests as requested. I guess it's possible my CAT's weren't warmed up, I dunno. It was like a 20 min drive to the smog station and I didn't get on it at all. So here's all the numbers for both tests:

Failed Test Numbers:

15mph & 1547rpm, %CO2 = 14.5, %02 = 0.3, HC (PPM) = 97, CO % = .13, NO (PPM) = 133
25mph & 1609 rpm, %C02 = 14.5, %02 = 0.2, HC (PPM) = 49, CO % .05, NO (PPM) = 39


Passed Test Numbers:

15mph & 1547rpm, %CO2 = 14.5, %02 = 0.2, HC (PPM) = 56, CO % = .03, NO (PPM) = 53
25mph & 1609 rpm, %C02 = 14.5, %02 = 0.1, HC (PPM) = 49, CO % .05, NO (PPM) = 3

As you can see, there are significant reductions in about 3 of the #'s when comparing both tests.

KevinB6876
08-24-2005, 06:26 PM
woops, sorry the rpm's for the passed test numbers were 1489rpm (15mph) and 1530rpm (25mph), respectively.