[trinity_gt]

Car has Comp 262AH cams, an MRT catted H-pipe, 24# injectors and custom tune. No MIL. Runs great. Gets ****ty gas mileage -- worse than I'd expect but since it runs well and doesn't have sooty tailpipes I figured it was average. Subjected it to a sniffer test today.

First is an ASM2525 40KPH dyno-rollers run. Numbers were:
HC (ppm): 52 (limit 52) PASS
CO (%): 0.01 (limit 0.29) PASS
NO (ppm): 70 (limit 385) PASS

Next was the curb idle test. This is where the wheels fell off:
HC (ppm): 772 (limit 150) FAIL
CO (%): 0.12 (limit 0.27) PASS

So the idle HC output is stupendously high. I'd immediately suspect the MRT cats are bad but except for the high idle HC, the readings are not really all that bad. The car idles well at 750-800RPM, a little lumpy I guess but these are pretty mild cams overall.

I'll get a scanner on it and have a look at the fuel trims I guess. Maybe the tune didn't account for the 24# injectors or something. I'm tempted to put the factory H-pipe with its 4 cats back on and scan it but I'm not sure if even it, with all those cats that are low-miles, squeaky clean and like new, will deal well with that much HC at idle.

Thoughts?

[Stark77]

My thoughts are as follows -
Move to Florida
no state income tax, no emmissions control laws

[02nightmaregt]

no emmissions control laws[/quote]

He!! yea on the no emissions testing. IN just did away with theirs too!!

[tritonofg]

HC=unburned hydrocarbons= running really rich

you can try to run the piss out of the car before the smog test and hope that all the hc's are buned off at the cats (which should be hot) before they reach your exhaust pipes or advance the timing to lean out a bit.

Good luck

[MaxedGT]

HC's are unburned fuel, but if you were rich CO would be high too. Advancing the timing at idle and raising the idle speed would help. The cams are likely the cause. If you're missfiring at idle that will also cause high HC.

[trinity_gt]

Originally Posted by MaxedGT

HC's are unburned fuel, but if you were rich CO would be high too. Advancing the timing at idle and raising the idle speed would help. The cams are likely the cause. If you're missfiring at idle that will also cause high HC.

Yeah, that's the thing: the other measured parameters don't look that bad. Even at idle, with HCs off the scale, the CO% is pretty low. Weird.

I think the cams are the cause of the HCs and the MRT pipe lacks the catalytic capacity (or quality) to deal with it all. I'm tempted to slap the OE H-pipe back on and try it again but want to go back to my tuner first to have him check the scalars for the 24# injectors and bump the idle to 1000RPM. I'll get his thoughts on advancing the idle spark advance as well. If the problem is more overlap from the cams and mixture leaking out the exhaust valves during this time, a timing advance probably wouldn't help. But these guys are local and I'm sure they've dealt with a few modded MGTs facing the province's sniffer test.

But damn...these are supposed to be mild cams. I can't imagine what "stage 2" cam guys are doing in these parts...

[nyuk98gt]

trinity_gt:

I bet your tuner will get you fixed up. It is common that the idle will run a little rich (even stock), especially with cams but, as you said, your cams are mild-ish. Ask your tuner about adjusting the MAF at idle and, also, about injector delay (For injector delay, I would make the numbers in the table a smaller in the table for idle loads and speeds to allow the fuel to vaporize better on the back of the valve. This is mentioned by guys a lot smarter about tuning than me, lol, so I am just passing along what I've read and adjusted in my tune.)

Your numbers look good to me otherwise. In Missouri we used to run on rollers or you could drive past a sniffer van a few times and pass (or fail). My car passed the roadside (van) sniffer a couple of times but I never had to have it sniffed at idle.

HTH,

Chris

[KillaGT]

no god dam emission here too at MS

[MaxedGT]

Originally Posted by MaxedGT

HC's are unburned fuel, but if you were rich CO would be high too. Advancing the timing at idle and raising the idle speed would help. The cams are likely the cause. If you're missfiring at idle that will also cause high HC.

I should have stated that the timing at idle should be retarded not advanced.

[2000GTdriver]

Let us know how it works out. I would like the same cams but also live in an area with the "roller" emissions test. We might switch over to the drive by vans (there are a couple now) but once these guys get their little kingdom built it is really hard to kick them out. Good luck!

[Notchbck93]

ahh, that's what I love about the PMS, lean it out right before and then fatten it back up on the ride home. I am the tuner.

[trinity_gt]

I talked to my tuner. I told him that since my last dyno tune I'd installed a JLT intake and he suggested we stick the WBO2 sensor in the downpipe and verify the state of the tune with the new intake, especially at idle. Then we can up the idle to 1000 and install the factory H-pipe and retest it. If all goes well, I'll put the MRT back in and bump the idle back down to 750 again. I'll post back when I have results.

[trinity_gt]

Little update:

Hooked up my scanner (Autotap with the full Ford package) and read out some values. The long and short term fuel trims are not unreasonable. The shorts are near 0% and the longs for both banks hovering around -5%. In fact this is pretty good. The front O2 sensors show good rich/lean crosses at idle so it's not simply sitting rich. MAF looks pretty steady and stable as well.

One thing I did notice was that my scanner showed the fuel pressure at 54PSI at idle and at 2000RPM. My Ford shop manual says the normal engine-running range is 35-50PSI.

The fuel trims being normal-looking don't seem to jive with the fuel pressure being that high. Thoughts?

[trinity_gt]

Another update...weird results:

Took the car to the tuner and had him verify the settings. Everything seemed pretty much optimal but we didn't want to take any chances so he loaded up a stock MDE2 (factory) tune and upped the idle to 1000RPM and we also swapped out the MRT H-pipe for the factory part.

This place is in a different city than the one I originally tested in so I used a different test facility than the first which may or may not play a part in the results...

The test results: FAIL. Now, however, things were quite different:

40KPH:
HC (ppm): 1 (limit 52) PASS
CO (%): 0.0 (limit 0.29) PASS
NO (ppm): 684 (limit 385) FAIL

Curb Idle:
HC (ppm): 1 (limit 150) PASS
CO (%): 0.0 (limit 0.27) PASS

So now the HCs are just dandy, the CO2 is fine but the oxides of nitrogen (NOx) are nearly double the limit and nearly ten times what was sniffed at the other facility (it was 70ppm). Thinking the issue must be timing advance, I went back to the tuner and we looked at the MDE2 file versus his 93-octane tune (which was used during the very first test...) The 93-octane tune had 31-degrees of timing versus the MDE2 timing of 50-degrees at light load. That must be it, I thought, since advanced timing can cause high cylinder temps and NOx formation. So we took a chance of bringing the idle-speed HC back up by loading the 93-octane tune and leaving its 750RPM idle as is. I went back and sniffed again:

40KPH:
HC (ppm): 0 (limit 52) PASS
CO (%): 0.0 (limit 0.29) PASS
NO (ppm): 696 (limit 385) FAIL

Curb Idle:
HC (ppm): 0 (limit 150) PASS
CO (%): 0.0 (limit 0.27) PASS

HCs better still, NOx worse. WTF? We pull timing out and the NOx gets worse? With the 4-cat factory H-pipe in place?

I'm really stumped. I don't think the EGR pipe was affected in swapping the H-pipe. What are the odds the EGR simply stopped working between the first sniff and now? I saw no MILs at all. I'm going to try the same test facility as was used in the very first sniffing to see what they say but if they come back with high NOx, where's a good place to look??

[trinity_gt]

Final update:

Took the car back to the first test facility this morning:

40KPH:
HC (ppm): 7 (limit 52) PASS
CO (%): 0.01 (limit 0.29) PASS
NO (ppm): 6 (limit 385) PASS

Curb Idle:
HC (ppm): 7 (limit 150) PASS
CO (%): 0.03 (limit 0.70) PASS

So the car now meets the emissions test and I can renew its plates. This was with the 93-octane tune and a 750RPM idle but most importantly, the factory H-pipe. I have to conclude that there's something up /wrong with the test facility that showed my NOx 10x the limit.

[2000GTdriver]

Glad you passed, sounds like it was a real hassle. I wish some of the magazines that test these parts would run an emissions test with them on a Mustang with the stock engine computer and/or custom tune on stock computer. Hope your future tests go better!

[trinity_gt]

Originally Posted by 2000GTdriver

Glad you passed, sounds like it was a real hassle. I wish some of the magazines that test these parts would run an emissions test with them on a Mustang with the stock engine computer and/or custom tune on stock computer. Hope your future tests go better!

Thanks. Actually, if I had done nothing but swap the H-pipe, left the tune as-is and stayed with the original test house, I probably would have done okay on the first re-test. The emissions testing is still a hassle overall and I really wonder about the consistency of these private test facilities housed in oil-change places and muffler shops based on the results I got.

I'm just glad I don't have to worry about it anymore, at least for 2 more years.

[nyuk98gt]

trinity_gt:

The EGR is a big player in keeping NOx down. Yours appears to be working fine. I wonder if the other facility needs to calibrate the sniffer??

Congrats on getting the car passed and for posting up follow-up reports.

Chris

[shallowreef]

In illinois all cars after 96 do not get a sniffer test. Instead they plug into your cars somputer and test everything through there. Wish i could help out but i am trying to figure out why they aren't running the test through your cars computer?

[trinity_gt]

Originally Posted by shallowreef

In illinois all cars after 96 do not get a sniffer test. Instead they plug into your cars somputer and test everything through there. Wish i could help out but i am trying to figure out why they aren't running the test through your cars computer?

It's been discussed because the pass-rate for OBD-II cars is ludicrously high -- over 97% I think -- which makes people wonder if it's really worthwhile going through a $36 sniffer test every two years on vehicles that monitor themselves. I think that there are at least two issues blocking that path though:

1) It's too easy for tuners to modify things to make it appear cars are passing. I can have a tune that will shut off my rear O2 sensors and never see a MIL while I run hollowed-out cats and a plug-in scanner may never be the wiser. Indeed, my MRT cats appeared to be hopeless at idle but I never saw an MIL, probably because the tuner disabled the rear O2s or something.

2) There are too many shops now with a large amount of capital invested in the rolling-road dynos and computer systems to simply decree that 90% of the cars on the road no longer need to use them. It would financially hurt shops that rely on e-testing for a good portion of their revenue. I don't know if the government ever thought of this when instituting the law in the first place: someday testing won't be required...what do you say to the shops that bought all this equipment?

But that's government for you...