HI all, I still consider myself a newbie so I figured I should ask rather than chase my tail. First a little background. I have a 90 burb w/ 350 AT 2WD 700r4 I've been trying to make it a little more fuel economical so I've been bumping up the timing and keeping the BLM's on average around 125. I wanted to make sure this was not the cause for failing smog. there are 2 emissions tests & I failed both. The first is the 25MPH test RPM was at 1280 Test Standard My reading HC(PPM) 136 253 Fail CO% 1.66 .64 Pass CO2% 13.6 Info O2% 0.9 info Nox(ppm) 853 977 Fail Dilution >6 14.2 The second is the 15MPH test RPM was at 1371 Test Standard My reading HC(PPM) 139 253 Fail CO% 1.24 .75 Pass CO2% 13.5 Info O2% 1.1 Info Nox(ppm) 926 1418 Fail Dilution >6 14.2 Info My SA table has lots of advance below 50 Map and gets closer to factory above that. Example @1200 RPM X 40 Map Factory timing is 0x52H and I'm at 0x76H Can that be the cause of failing? or do I need a new cat? Thanks in advance for all your help. EDIT: Forgot to mention this is a TBI, Original bin was ASDU, 7747 ECU. The truck has leaky valve seals (It smokes after it's been sitting for several hours)

The first is the 25MPH test
RPM was at 1280

Test Standard My reading
HC(PPM) 136 253 Fail
CO% 1.66 .64 Pass
CO2% 13.6 Info
O2% 0.9 info
Nox(ppm) 853 977 Fail
Dilution >6 14.2

The second is the 15MPH test
RPM was at 1371

Test Standard My reading
HC(PPM) 139 253 Fail
CO% 1.24 .75 Pass
CO2% 13.5 Info
O2% 1.1 Info
Nox(ppm) 926 1418 Fail
Dilution >6 14.2 Info

My SA table has lots of advance below 50 Map and gets closer to factory above that.

Example @1200 RPM X 40 Map Factory timing is 0x52H and I'm at 0x76H

Can that be the cause of failing? or do I need a new cat?

It looks like the cat efficiency is low @ 15MPH test (O2=1.1%) I don't know on the 25MPH test-O2 is a bit lower. If it were up to me I would replace the cat & retest. What is your timing in degrees?
P.S. are you in Calif?

No, I'm in Tx,

Not sure what you mean by my timing in degrees, but, idle timing is set 0 with the timing bypass disconnected. As for the example above, the calculated numbers are 28.83 for factory and I've set it to 41.48.

here is the 30-100 Map @1200 RPM if that help
43.59 42.54 41.48 40.78 38.67 35.86 31.99 28.48 25.31 23.20 18.98 16.87 15.12 11.95 11.95

As long as you can burn your own chips, run the test with about 10 degrees total spark advance in the areas of the test. It'll help both HC and NOx.

Too much spark advance really hurts NOx, and also hurts HC some.

Sounds good.

Any long term concerns with the cat or anything with hi NOx or HC?

If your HC's are 253, your cat is probably already toasted. A working cat will knock down HC's pretty well. Yours isn't. You might be experiencing a slight misfire, but it's pretty hard to find on a V8.

NOx won't hurt a cat though.

41 degrees is a lot of timing. That will raise your NOX and HC for sure! I agree with RednGold86Z: burn your own with minimal timing, just for the test. Don't forget to make sure the base timing is correct for the test. Good luck.

Forgive my ignorace but what is "the base timing"?

Should I set the whole table to 10' accross the board?

Ok, I set the whole table to 10,

Added HEET (yellow bottle)

And PASSED!!!!

HC was 75 & 95 respectivly
And NOX 45 & 63

Ok you passed emissions with nice numbers. Something to consider though. Why are you running 41* of timing with Swirl Ports. They definately don't need it.

If BOTH your HC and NOx are failing, there is NOTHING you can do with tuning to make it pass.

With tuning, you can "trade" HC for NOx and vice versa. BUT NOT BOTH.

This suggests that possibly something mechanical is not right. Such as a catalytic converter and/or EGR.

Too many HCs are usually a cat and too many NOx are usually an EGR.

Hey Fast,

I was bumping up the timing to try to get it more fuel economical. I was getting 13mpg on the highway.

Intersting table you attached, its more retarded than the asdu I started with, asdu.JPG


So I kept on bumping it until I saw pings. Did I do something wrong?

Here is the SA I'm planning on running tomorrow. Are there any concerns with running too much of a SA?
myasdu.JPG

Any feedback would be greatly appriciated.

Thanks Grim,

I'll take a look at the EGR in a couple of months when the weather cools off. It's starting to warm up right now, 102'F today, it's only gonna get worst.

That ASDU table has something wrong with it. I am posting both ASDU and ARHT which are both of the $42 .bins that I have. Both have very similar tables. I am going to guess that either your XDF/ECU file is not correct or the BIN had been modified.

Too much spark advance will actually hurt fuel mileage and could hurt the engine. All the values you have higher than 42* are limited to 42* by the ECM. The actual distributor can only advance the timing a little over 42* BTDC before it starts crossfiring to the next cylinder. If you advance the distributer 6* BTDC it will allow you to run 48* advance (this is why TPI cars are run at 6*, they have 47* programmed into some load/rpm areas).

Sounds like the weather here in DFW where I am. I think it could qualify as the surface of the sun.

Ok, I'll have to look for another bin, that shows something closer to yours.

Yeah, the weather is very similar to DFW, I'm in Bedford
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BTW, how much advance is too much?

Ok, I'm looking at the moates ASDU file http://www.moates.net/files/1)%20Sto...5/asdu9567.bin and It loos like the same one that I have.

I'm seriously confused.

Really, I am in Bedford too on the Hurst border. I live about 2 minutes from 121 and Bedford-Euless Rd.

You have probably seen my old Red/Grey van running around and not even realized it. Its a loud SOB and pretty darn quick too.
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Try another ECU/XDF file. I bet the one you have has an error.

LOL, Big white burb with a blue stripe running through it. Never miss it in a parking lot

I'm off 121 and harwood. Yeah spitting distance from eachother.

I'll try to find another XDF.

So I'm probably not running 42' advance...

I am going to say that it is safe to assume you are running about 10* lower than you are seeing. Based on an idle timing of 16* on ASDU and you are seeing 26*. Really seems as if the 9.81* bias has not been accounted for in the XDF.
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If you have AIM shoot me an IM. I can send you the best $42 XDF that I have. Red83brick

You're right,

I was using the one from tunerpro.net 7747-mine.ecu. The one at moates shows about 10' lower.

So am I still too advanced?

You are running alot of timing for my taste with these heads. I simply do not see the need if everything else is up to the task. Ignition system working well, cylinders sealing reasonably well, and the fuel system operating correctly.

More spark advance does not mean more MPG. A certain amount in a few places can help. However it is easier to find fuel economy in the VE, AE, DE and DFCO than the spark tables on a stock engine.

Considering I have 26 posts (mostly from this tread) and you have over 4K I'm all ears

Is there a primer or anything that I can read or somthing?

Thanks

Post count doesn't mean anything other than I have a loud mouth, lol.

In all honesty though I have tuned ALOT of engines in different chassis.

The TBI tuning thread in the TBI forum has ALOT of information in it.

Basically

1.) Tune VE tables using BLM correction (EGR and CCP disabled)
2.) Rough in spark table
3.) Tune AE
4.) Tune DE
5.) Fine tune VE table and spark
6.) Enable EGR and correct tables
7.) Adjust TCC settings

Cool, I'll dig in tomorrow. Need to get some rest. see you around town.

Same here man

I didn't get into this in my previous posts, but this is what I am running in a vehicle of similar weight and aerodynamic properties. I am sure you suburban has some crazy tall rear gear ratio as well. GM loved to put 3.08s even with the 700r4. If you are lucky you get 3.42s. Mine has GQ1 which is the standard gear ratio which for a 1983 G20 Van was 3.08s. Great fun those are, lol. My 700r4 is setup to shift at 4,800-5,000 rpm @ WOT and it does the 1-2 shift at ~41 mph and the 2-3 upshift at ~80 mph. My point is I am running the stock timing table (a few stock numbers were negative but the 7730 would not work with them so they are 0, and the highway spark mode has been enabled) with my engine and having great luck with it. You can listen to how quick it runs up the gears up to speed especially since I stalled it up to about 1,300 rpm before smacking the throttle. Also notice how nice and flat the torque curve is the fuel table depicts this well. I have a feeling you will find a very flat VE table as well if you are tuned close to what the engine needs.

http://s243.photobucket.com/albums/f...t=101_1403.flv

Even from a 25 mph roll in 2nd gear it picks up quick at low rpms (Notice Grubbs and Bell HS?).

http://s243.photobucket.com/albums/f...t=101_1400.flv

Stock rear end I beleive was a 3.42. Now it's a 3.08 off a 87 burb. Speedo is off by 10%

I'm still looking up info for AE but I have brought the timing back to stock...

YOu have quite a collection of videos and picks. I love the supper charged caddy. All yours?

I take it the 305 TPI in the van is not stock... I take it you did the conversion yourself?

The caddy is not mine, but I have it on there because its an awesome ride.

The Dodge Truck, the S10, and the Van are mine. The Vans transformation is pretty much shown through the pictures.

I did the TPI conversion myself. The 305 is only mildly built, but still has stock 187 casting 305 swirl ports on it. Thorley Tri-Y headers, Mild hydraulic roller cam, stock flattop pistons, balanced and blueprinted. I also have total seal rings and other good parts. This build was all about maximizing HP/TQ and fuel mileage.

For AE you want just enough fuel for a smooth take off as you move the throttle. I often find that these stock setups drown the engine in fuel.

I'm picking up a Jack n Box burger and will be right back to answer any other questions.

Heh heh heh,

We call it crack in the box. I love their chiabata bacon burgers.

I guess the problem with AE is I don't know what I'm looking for. I think I have a smooth take off as is.

We probably need to get together for a beer or something so I can get a better understanding.

Thanks again.

Now that sounds like a plan I could live with.