TheSamba.com :: View topic - Using an LM 2 for tuning and smog (for a beginner)

Wed May 29, 2013 12:11 pm

I thought I'd create a new thread about this particular procedure for part of my quest to pass smog. I would like this thread to be noob friendly and to only cover the basics.

Assuming, all basic maintenance has been done and you are using a stock exhaust with a bung on the CAT for an O2 sensor, the replies following should help with the tuning procedure.

I have already calibrated the LM 2's O2 sensor, so what is my next step besides attaching the LM 2 O2 sensor to the CAT and plugging the LM 2 into a power source?

Do I simply start adjusting the AFR using the adjustment screw when the engine is cold or do I need to warm up the bus first and then adjust the AFR? What AFR/lambda number should I be shooting for? 14.1 and one?

In one of Steve's threads he said he was able to achieve cooler head temps along with really good smog numbers with a minimal hit to power, how did he do that? What was the process?

Wed May 29, 2013 12:53 pm

Since you are wanting to pass smog please do the following after reviewing this: http://www.ratwell.com/technical/Smog.html

1. Set your dwell and timing to factory specs. You can set it back to 28 - 29 BTDC at full in after you pass smog. I got nailed on this one last time.

2. Once your LM2 is calibrated, take the bus out and warm it up. Bring it home.

3. Set your idle CO to the factory spec. There should be an orange sticker on the back of the engine lid that spells out what the number is supposed to be.

4. Run the engine at 1500 RPM and post the result here.

5. Run the engine at 2500 RPM and post the result here.

6. Run the engine at 3500 RPM and post the result here.

7. If the lead is too short put a passenger in the back seat with the LM2. Run the bus in 2nd gear at 15 mph straight and level. Post the result here.

8. Do test number 7 in 3rd gear at 25 mph and post the result here.

9. Passenger in the back - get out on the freeway - run flat and level on I-80 at 65 MPH for a couple miles. Post the average it shows here.

Wed May 29, 2013 10:38 pm

When you say to set m timing to factory specs does that mean I should be setting it at 7.5 degrees to the left of zero at idle (do I warm the engine first when doing timing?) instead of 28-29 degrees at 3500 rpm?

Thu May 30, 2013 4:11 am

Yes, time it at 7.5º BTDC and set the idle speed to the correct 850RPMs.

Thu May 30, 2013 5:59 am

Randy in Maine wrote: Yes, time it at 7.5º BTDC and set the idle speed to the correct 850RPMs.

Yes - like Randy says but just for the smog test. Set it back to 28-29 degrees BTDC at 3500 with the hoses off after you pass the test. They allow 3 degrees off the sticker but I was like 3.1 off and they flunked me the first test. Everything else passed so I had to go back and wait in line again after I reset the timing to the sticker. Basically you don't want to give them any opportunity to flunk you. Most states want the older cars off the road now if they are later than 1968 and earlier than about 2003 so they are starting to get picky on these cars. Their testing shows that the cars on the road from 1969 - 2003 emit the most smog compared to 2004 and later cars. There are so few 1968 and earlier cars on the road they don't care about them.

Thu May 30, 2013 5:29 pm

Just freaking awesome! After returning from my drive I go to install the LM-2 O2 sensor and upon first use I get a freaken E2 error code:| re calibrating it doesn't clear the code, wtf!

Somebody really hates me:|

Thu May 30, 2013 5:37 pm

one of these:

Error 2 Heater circuit
open
1. Damaged sensor cable.
2. Cable connector not fully seated
3. Sensor Damaged

1. Inspect sensor cable for rips or tears.
2. Verify Sensor is fully seated into
connector, make sure it ‘clicks.’
3. Replace Sensor

Thu May 30, 2013 6:01 pm

False alarm:o I had the sensor in the top port as opposed to the bottom port.

I do have an exhaust leak, unfortunately it's in the muffler and it's because of a bad weld job. I don't know if bus depot will take care of me with this as I have also painted it....|:|

As of right now CO is at 1.01-1.06 and I don't think I can turn the screw any more (it feels loose).

Thu May 30, 2013 6:08 pm

Ok for the first set of results we have:

Idle = 1.01-1.06 lambda
1500 = .98
2500 = .94
3500 = .97

I'm trying to figure out the logistics of the rest of the tests. How does it look so far?

Thu May 30, 2013 6:48 pm

stop what you're doing and fix the exhaust leak. 02 sensors do not tolerate leaks. you are going to get false readings. i don't care if it is the size of a pinhole...fix it

Thu May 30, 2013 7:30 pm

skills@eurocarsplus wrote: stop what you're doing and fix the exhaust leak. 02 sensors do not tolerate leaks. you are going to get false readings. i don't care if it is the size of a pinhole...fix it

The leak is after the O2 sensor (its at the flange that connects to the tail pipe).

Thu May 30, 2013 8:36 pm

Ok here are the results for tests 7, 8, 9:

2nd gear @15mph = 1.0
3rd gear @25mph = 1.01
65mph average of three runs = 94.3

Engine oil temps were way cooler with these settings at about 200 degrees whereas before my temps on the same drive would put me around the 220 mark. However getting to 65mph was harder and going faster than that would have brought me close to redline.

So the question becomes; are these numbers good enough to pass smog?

And

If I want to get some of my top speed back do I mess with the AFR or just redo the timing to 28 degrees and my speed should return?

Thu May 30, 2013 8:50 pm

So to recap:

AFR figures are calculated using the theoretically optimal air fuel ratio of 14.7.

1500rpm = .98 lambda or 14.41 AFR
2500rpm = .94 13.82
3500rpm = .97 14.26
2nd gear @15mph = 1 14.7
3rd gear @25mph = 1.01 14.85
65mph = .943 13.86

Thu May 30, 2013 11:13 pm

I think the bus should pass smog if everything else is Ok. Be aware that those numbers, while really good for smog - darn near perfect - are in fact too lean for it to run cool. Mine is set just a tad richer to cool it and it also passes smog. Right now lets get you past smog.

How much did you have to adjust the idle mixture to get it right? In other words, were these numbers like this without changing anything since the last test?

If you pass this time and nothing else was changed, my guess is that the old catalytic convertor was worn out. We can work on tweaking the bus to run cooler after you get past smog. Be sure to keep a spreadsheet or logs of the readings with dates, what adjustments were and circumstances so you can compare those numbers in the future.

Thu May 30, 2013 11:29 pm

SGKent wrote: I think the bus should pass smog if everything else is Ok. Be aware that those numbers, while really good for smog - darn near perfect - are in fact too lean for it to run cool. Mine is set just a tad richer to cool it and it also passes smog. Right now lets get you past smog.

How much did you have to adjust the idle mixture to get it right? In other words, were these numbers like this without changing anything?

To get to the initial idle CO levels I had to adjust it a lot. No further adjustments were done after setting timing at 7.5BTDC and idle to 875.

Also why record the AFR at 15mph in 2nd and 25mph in 3rd? I would never drive the bus like that.

Fri May 31, 2013 4:25 am

SGKent wrote: I think the bus should pass smog if everything else is Ok. Be aware that those numbers, while really good for smog - darn near perfect - are in fact too lean for it to run cool. Mine is set just a tad richer to cool it and it also passes smog. Right now lets get you past smog.

How much did you have to adjust the idle mixture to get it right? In other words, were these numbers like this without changing anything since the last test?

If you pass this time and nothing else was changed, my guess is that the old catalytic convertor was worn out. We can work on tweaking the bus to run cooler after you get past smog. Be sure to keep a spreadsheet or logs of the readings with dates, what adjustments were and circumstances so you can compare those numbers in the future.

Playing devils advocate here. Maybe not the time and place but I have noticed in tracking my AFM that mixture at cruise on flat surface is 14.7 normally. Full throttle its 12.5 under load. One would think cruising with 14.7 AFM would cause me to run hot ??? Not the case. My oil temps after 1hr run time of driving 45-65 mph are 185-195. Head temps never over 350 driving in the foothill mountians. I have given thought to popping the top on my AFM to adjust running mixture to make it rich but am on the fence consodering my oil temps and head temps are perfect. Just some food for thought.

Fri May 31, 2013 8:26 am

curtis4085 wrote: SGKent wrote: I think the bus should pass smog if everything else is Ok. Be aware that those numbers, while really good for smog - darn near perfect - are in fact too lean for it to run cool. Mine is set just a tad richer to cool it and it also passes smog. Right now lets get you past smog.

How much did you have to adjust the idle mixture to get it right? In other words, were these numbers like this without changing anything since the last test?

If you pass this time and nothing else was changed, my guess is that the old catalytic convertor was worn out. We can work on tweaking the bus to run cooler after you get past smog. Be sure to keep a spreadsheet or logs of the readings with dates, what adjustments were and circumstances so you can compare those numbers in the future.

Playing devils advocate here. Maybe not the time and place but I have noticed in tracking my AFM that mixture at cruise on flat surface is 14.7 normally. Full throttle its 12.5 under load. One would think cruising with 14.7 AFM would cause me to run hot ??? Not the case. My oil temps after 1hr run time of driving 45-65 mph are 185-195. Head temps never over 350 driving in the foothill mountians. I have given thought to popping the top on my AFM to adjust running mixture to make it rich but am on the fence consodering my oil temps and head temps are perfect. Just some food for thought.

Matt - there is a huge difference between sea level and 4000' - 5000' ASL where you are. Not only are you 3 degrees cooler per 1000' but you have less air to compress so the head temps are cooler. No bus has cooling issues at altitude. Come to sea level and try again. California's Central Valley ranges from sea level to 200'. Get out into some valleys in California - Death Valley, Coachella Valley etc and there are areas below sea level. Not only do we have days that are 110+ but we have the added atmospheric compression to deal with too.

Fri May 31, 2013 10:40 am

SGKent wrote: curtis4085 wrote: SGKent wrote: I think the bus should pass smog if everything else is Ok. Be aware that those numbers, while really good for smog - darn near perfect - are in fact too lean for it to run cool. Mine is set just a tad richer to cool it and it also passes smog. Right now lets get you past smog.

How much did you have to adjust the idle mixture to get it right? In other words, were these numbers like this without changing anything since the last test?

If you pass this time and nothing else was changed, my guess is that the old catalytic convertor was worn out. We can work on tweaking the bus to run cooler after you get past smog. Be sure to keep a spreadsheet or logs of the readings with dates, what adjustments were and circumstances so you can compare those numbers in the future.

Playing devils advocate here. Maybe not the time and place but I have noticed in tracking my AFM that mixture at cruise on flat surface is 14.7 normally. Full throttle its 12.5 under load. One would think cruising with 14.7 AFM would cause me to run hot ??? Not the case. My oil temps after 1hr run time of driving 45-65 mph are 185-195. Head temps never over 350 driving in the foothill mountians. I have given thought to popping the top on my AFM to adjust running mixture to make it rich but am on the fence consodering my oil temps and head temps are perfect. Just some food for thought.

Matt - there is a huge difference between sea level and 4000' - 5000' ASL where you are. Not only are you 3 degrees cooler per 1000' but you have less air to compress so the head temps are cooler. No bus has cooling issues at altitude. Come to sea level and try again. California's Central Valley ranges from sea level to 200'. Get out into some valleys in California - Death Valley, Coachella Valley etc and there are areas below sea level. Not only do we have days that are 110+ but we have the added atmospheric compression to deal with too.

Good to know. Thank you.

Fri May 31, 2013 12:43 pm

I passed!!!!

I'll post the numbers later tonight but I finally passed!

I almost failed too because I set the idle timing with the vacuum hose connected and he tested the timing with it disconnected, doh! Easy fix though.

Fri May 31, 2013 12:47 pm

ivwshane wrote: I passed!!!!

I'll post the numbers later tonight but I finally passed!

I almost failed too because I set the idle timing with the vacuum hose connected and he tested the timing with it disconnected, doh! Easy fix though.

I always set idle timing with vacuum hose connected.