Author Topic: Smog Question (Read 4684 times)

BUDDERS · « **on:** Jun 29, 2010, 09:05:03 PM »

So I went to smog my '87 2wd Toy today and it didn't pass on the 15mph test. The NO levels were too high. The max allowable is 789 PPM and mine was 1204 PPM. Two years and 508 miles ago (yes you read that right - it sits a lot) my NO level on the 15 mph test was 1119 PPM and the max allowable then was 1128 PPM at the same smog station with the same smog tech.

The only thing that was different with this smog test is that it has some older gas in it now and the Max allowable NO levels dropped 339 PPM.

Now my question is why did the max NO levels drop so severely? The motor in this truck is a 22re and is pretty well hopped up with a TRD midrange cam, 12.4:1 compression (probably why the NO is high), header, intake, bigger racing valves...yadayadayada.....and it runs great, but I don't think it will ever pass smog with this high of NO unless I through in a stock motor. Does anyone have a clue what to do?

88yota · « **Reply #1 on:** Jun 29, 2010, 09:29:37 PM »

I had very high nox levels....a new cat fixed it down to nothing

emsvitil · « **Reply #2 on:** Jun 29, 2010, 09:40:33 PM »

Add a restricter after the cat to add backpressure... (about 3/4" hole).

The backpressure will help with EGR which will reduce NOX

Take out after test.

BUDDERS · « **Reply #3 on:** Jun 29, 2010, 09:50:02 PM »

Quote from: emsvitil on Jun 29, 2010, 09:40:33 PM

Add a restricter after the cat to add backpressure... (about 3/4" hole).

The backpressure will help with EGR which will reduce NOX

Take out after test.

Really? Will that drop it 400 PPM? Are you talking about a plate with a 3/4" hole bolted between the flanges or a smaller diameter section of pipe?

emsvitil · « **Reply #4 on:** Jun 29, 2010, 09:58:11 PM »

Holes add up to about 3/4" hole.

The EGR valve needs some backpressure to work. It might just do it............

BUDDERS · « **Reply #5 on:** Jun 29, 2010, 10:21:02 PM »

Hmmmm....now you got me thinking.

8D3TOY · « **Reply #6 on:** Jun 30, 2010, 08:01:44 AM »

I just failed due to high No (see my post in how to pass smog) I added some RPX gas kicker, recomended in the thread went back the next day and passed with flying coclors. There were some other factors so there is no hard proof the RXP wroked but it didnt hurt. $6 at AutoZone is easier than a new cat.

yotarunner85 · « **Reply #7 on:** Jun 30, 2010, 08:54:54 AM »

Have the same problem with my 85 22RE (cam, big valves, higher compression, & header) every smog. My NOX were at 1200. So what I did is tee into the vacuum line that goes to the EGR valve then tee in to the ported vacuum line off the throttle body & hide the vacuum line under the intake plenum. What this does is at part throttle the ported vacuum source applies more vacuum to the EGR valve than normal causing the EGR vavle to open more & that = less NOX. After the smog I take the vacuum line off and throw it in my glove box for next time. Been doing this for the last 8 years. Also what helps is making sure that the cat is real hot. I sit outside the smog shop & run the engine at 2000 RPMs untill he is ready to smog it. Good luck.

BUDDERS · « **Reply #8 on:** Jun 30, 2010, 10:35:23 AM »

Quote from: yotarunner85 on Jun 30, 2010, 08:54:54 AM

Have the same problem with my 85 22RE (cam, big valves, higher compression, & header) every smog. My NOX were at 1200. So what I did is tee into the vacuum line that goes to the EGR valve then tee in to the ported vacuum line off the throttle body & hide the vacuum line under the intake plenum. What this does is at part throttle the ported vacuum source applies more vacuum to the EGR valve than normal causing the EGR vavle to open more & that = less NOX. After the smog I take the vacuum line off and throw it in my glove box for next time. Been doing this for the last 8 years. Also what helps is making sure that the cat is real hot. I sit outside the smog shop & run the engine at 2000 RPMs untill he is ready to smog it. Good luck.

So what exactly are you bypassing? The modulator, the VSV or both? I understand that your trying to open the EGR earlier which makes sense although I don't know if it will help that much.

yotarunner85 · « **Reply #9 on:** Jun 30, 2010, 01:32:08 PM »

Not really bypassing anything just adding more vacuum. The modulator applies vacuum to the Egr and I tee into the line that goes to the Egr. The other end of the line gets teed into the ported vacuum line off of the throttlebody so it only applies the vacuum to the Egr at part throttle. Runs crappy but thats what I do to get it to pass. Oh I also back the timing off to 3 or 4 degrees from the stock setting.

8D3TOY · « **Reply #10 on:** Jun 30, 2010, 10:53:01 PM »

I read on a smog site that high NOX is a product of high combustion chamber temps, instead of getting it really hot just get to normal operating temp. I went from 1276 down to 62 with no mods other than normal operating temp and RXP gas kicker in the tank.

yotarunner85 · « **Reply #11 on:** Jul 01, 2010, 09:06:25 AM »

Yes, NOX emission are a product of high combustion chamber temps, not to be confused with engine temps. Raising the compression on an engine will raise combustion temps. NOX emissions are produced when the combustion temps are above 2500 degrees. What the EGR does is let a controlled amount of exhaust gas into the combustion chamber, which is inert and doesn't burn. This inert gas takes up space in the combustion chamber so less of a air fuel mixture will enter the combustion chamber, effectively lowering the compression, combustion chamber temps & NOX emissions. The reason I run the engine at 2000 RPMs before the smog is to make sure the Cat is at operating temp. Catalytic converters are more efficient when at operating temp. allowing them to burn off more pollutants (CO, HC, & NOX).

gtoyonrocks · « **Reply #12 on:** Jul 01, 2010, 09:17:46 AM »

There is a entire section on the forum on how to pass smog, just do a quick search.

BUDDERS · « **Reply #13 on:** Jul 01, 2010, 11:14:27 AM »

Quote from: yotarunner85 on Jul 01, 2010, 09:06:25 AM

Yes, NOX emission are a product of high combustion chamber temps, not to be confused with engine temps. Raising the compression on an engine will raise combustion temps. NOX emissions are produced when the combustion temps are above 2500 degrees. What the EGR does is let a controlled amount of exhaust gas into the combustion chamber, which is inert and doesn't burn. This inert gas takes up space in the combustion chamber so less of a air fuel mixture will enter the combustion chamber, effectively lowering the compression, combustion chamber temps & NOX emissions. The reason I run the engine at 2000 RPMs before the smog is to make sure the Cat is at operating temp. Catalytic converters are more efficient when at operating temp. allowing them to burn off more pollutants (CO, HC, & NOX).

Thanks for the education. I took all of the Toyota classes through T-ten except for the smog class so smog no-how is definately my downfall. I think I'm going to try a combination of replys above.

hilux-1983 · « **Reply #14 on:** Jul 01, 2010, 12:10:51 PM »

Quote from: BUDDERS on Jul 01, 2010, 11:14:27 AM

Thanks for the education. I took all of the Toyota classes through T-ten except for the smog class so smog no-how is definately my downfall. I think I'm going to try a combination of replys above.

I graduated from the 1st T-TEN class program in AZ 22 yrs ago. In fact Iyogo Togo(toyota's president) came for the ribbon cutting ceremonies. Some of my old instructors are still there(GateWay College, Phx, Az) Yeah, they didn't cover carburated smog stuff, only efi. From what I can remember anyway.

gtoyonrocks · « **Reply #15 on:** Jul 01, 2010, 02:03:12 PM »

Check out this post by Mike. There is a lot of good info in there. I hope this helps. http://board.marlincrawler.com/index.php?topic=1119.0;highlight=how+to+pass+smog

yotarunner85 · « **Reply #16 on:** Sep 16, 2010, 08:48:18 AM »

Just got my 1985 Toyota 4Runner smogged (in San Diego county) and passed. I backed the timing down 3 degrees from stock and ran a vacuum line from the ported vacuum on the throttlebody and teed in to the EGR line.(I do this to keep my NOX down due to my engine mods.) Also got the cat hot before the test.
Here are my results:

15 mph / 1815 rpms / 14.17 co2 / 1.42 o2 / 113 hc / 0.03 co / 570 nox /
25 mph / 1848 rpms / 14.65 co2 / 0.64 o2 / 73 hc / 0.01 co / 299 nox /

Good for another 2 years.

BUDDERS · « **Reply #17 on:** May 22, 2011, 09:08:14 PM »

OK, so I finally got around to smog this truck again after failing back in October.

All I did was get my EGR valve to open up earlier by adding a small vacuum line and a couple T's under hidden under the throttle body and add the RXP additive to the gas tank. I ran a full tank of gas with the additive through the motor until the fuel tank was dry (I'm glad I was there to turn it off before the fuel pump burned up) and then topped it off with a new tank of '91 octane and ran it over to the smog shop.

My NO levels went from the low 1200 PPM to 289 PPM!!!!!!!! This was on low speed idle which I failed before.

I passed with flying colors!!!!!!

The smog print out sheet had the state average at 450 and something PPM. Mine was well below average.

Thanks guys for the help. I guess you gotta be smarter than the smog machine with these old trucks......

yotarunner85 · « **Reply #18 on:** May 23, 2011, 02:12:05 PM »

Right on

Good for 2 more years $Beer Chug\'n$

jimbo74 · « **Reply #19 on:** May 23, 2011, 02:16:59 PM »

i am interested if your few hidden vacumum lines were what did it or not?

are you going to leave them in, or take them out? out of pure curiosity, i'm not trying to bust you

lol

was there a vacuum deficiency you had before?

BUDDERS · « **Reply #20 on:** May 24, 2011, 04:30:59 PM »

Nah, I bet the vacuum lines for the EGR had nothing to do with it. I think it opened up about 300 rpms lower.

yotarunner85 · « **Reply #21 on:** May 24, 2011, 05:24:25 PM »

Take the vacuum lines out and retest, then you'll know the difference. That's what I did, but I have access to a smog machine.

BUDDERS · « **Reply #22 on:** May 25, 2011, 06:54:37 PM »

I don't have access to a smog machine anymore. I have to pay to get it smogged and I wanted to do everything as much as possible to get it to pass without taking it in for a 3rd time.

yotarunner85 · « **Reply #23 on:** May 25, 2011, 07:49:30 PM »

I know what you mean it's a pain in the

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