polygaryd

hey guys i am having a little trouble passing emissions my car is right on the line of pass fail and ofcourse my luck it fails. it runs to rich at idle but passes the 2500rpm part of the test. i went into my bin file and changed the air fuel ratio to 16 i assume thi smeans 16 parts air to 1 part gas which in turn will lean it out. but this didn't help to much. so i went into my bin again and found under the arrays section pe % change a/f ratio vs rpm. now i saw that at 2000 rpm it is at .89 at 2400 rpm it is at 1 and 2800 rpm it is at 1. now this is the area where it passed so i go down to the 400 rpm and 800 rpm section and find 1.06. do i turn those values down or up to lean them out so it will pass at idle?

Sorry for the long post but need help and fast so i can get inspected.. MA sucks

funstick

could you post the 5gas data from the emiisions testing center. going lean will of course drop co2 raise hc's and create all sorts of havoc. it would be better to make sure you have a futioning cat and run the engine a hiar bit richer at idle.

polygaryd

here are the stats..

pollutant reading limit
hc ppm idle 410 220
hc ppm 2500 rpm 87 220
co % idle 1.17 1.20
co % 2500 rpm .75 1.20


now obviously i want to cut down on the hydrocarbons at idle and still maintian low co. i have a flowmaster high flow cat i dont know if that matters. now if you can help me tune my chip a little that would be great. i understand i dont want to lean it out cuz that will raise hc's which i dont want at all but riching it will raise co right? so what do i do. i want to have the car run at idle like it does at 2500 rpm is that possible?

Grumpy

There are a few basics you need to make sure your've done before thinking of tuning to pass.

ie

Fresh oil, the PCV system allows for crankcase fumes to be sucked into the engine, if they're ladened with HC, from age that's a mark again you.

Run the engine HOT, so it's internal friction is low, and the car will run artifically lean.

Raise the idle speed, to min the self egr'ing effect at idle.

Do a 20 min or so freeway run to get everything FULLY up to temp..

Cat's loose their peak effeciency rather quickly.

Denis.V

You can try to force increments in min idle speed by turning the idle adjust screw. If the car run @ 1100 RPMs the HC will be differents.

High limits. My local limits are:

HC ppm = 100 max. , at idle & 2500 RPMs
CO % = 0.5 max., idle & 2500
(CO + CO2) % = 6.0 min., at idle & 2500

funstick

the hc will go up as you lean it out. try going towards 13.9-14.7 add timming. that cut it down tremendously. also it should keep co and co2 down as well.

Ed Maher

You don't mention what your combo is, i'll take a stab that based on your rudimentary knowledge of tuning that it's near stock?

If so, you shouldn't need to do any special tuning to pass emmisions. A near stock car that fails emmisions is a sign that something is wrong with it.


If you are far from stock with osme kind of nasty head / cam combo, my first move would be as suggested to raise the idle speed a few hundred RPMs, ideally as high as legal for the test.


BTW, for the love of ***, don't go playing with tables you don't know what they do. PE fuel has NOTHING to do with anything for an emmisions test. You are aware you can and will blow your engine up in short order of you do the wrong things to the wrong tables. PE fuel would be an example of a table to understand before you change it.

polygaryd

hey guys my setup is pretty stock i mean i have a k and n air filter right on the throttle body i have an air foil on it. i have headers with air tubes . it is an 87 GTA with the tpi 350 in it i put a 5 speed in it. i changed it from mass air flow to speed density and when i took the test i had 93 octane fuel in the car if that helps and or makes a difference. i haven't changed my pe fuel tables yet so i am all set for now i will turn down my air fuel ratio i leaned it out so i will put it back to 14.7 or maybe lower like suggested. thanx guys

Ed Maher

OK, since it's stock, it should have no problems passing emmisions. Custom tuning to get through emmisions is the realm of things that go lump lump in the night.

Besides all the stuff already mentioned (fresh oil, tune-up, hot engine, raise idle speed) , if all else fails you might want to just go for a new cat. After all those years there is a chance the stocker is just not getting it done anymore. A properly functioning cat can make all the difference in the world.

Pablo

iTrader: (1)

how are you adjusting your air fuel ratio without a wideband oxygen sensor?

Ed Maher

He's probably doing it with the stoich AFR constant that TPI ECMs have. Don't try to read so much into a newbie post, helps to just be familiar with the available adjustments.

kevm14

Increasing the AFR, numerically, should decrease HC emissions, until you run into a lean misfire. Up until then, HC should be inversely proportional to your AFR...and at idle, the AFR should be pretty much right around stoich. My guess is he has an idle misfire that's not caused by AFR or spark, but by something else (ignition system might need a tuneup, for example).

funstick

could it be a lean missfire at 16:1 or so. sure could.

kevm14

From the sounds of it, he went through the first time without touching the stock calibration...which is why I think he has a misfire at idle (plugs, wires, coil, distributor, uh, EGR, ICM, etc.).

funstick

if you look at the rest of his emmision data you can blantantly see that its a lean missfire. also you can create tons of HC running lean without a missifre.

JP84Z430HP

Not sure how much help this tidbit is, but in a technical training course I took earlier in the week, I learned that 15% lean WILL cause a lean misfire. Therefore, I see how 5-10% could increase emissions.....

kevm14

Are you saying it was lean misfiring the first time he brought it through with a most likely stock calibration? And in his efforts to fix it, he made it worse?

Are you also saying that an incomplete burn (not a misfire) due to running lean, would also increase HC? I agree if that's the case...I just would have called the incomplete burn a misfire, but that might not be correct.

funstick

thats what im saying. it burning but so poorly that its hardly burning at all. i bet this stock motor has a rediculous lope to it.

kevm14

Then some factory calibrations are farther off than some of the more knowledgable people I know would care to admit (not on this board).

RBob

iTrader: (1)

The headers may be contributing due to O2 sensor placement. If the O2 sensor is in the collector (or far enough back from the heads) you will need a heated sensor.

RBob.

funstick

if you have a pre 1988 TPI system and you changed it to S/D there whole problem could be that the camshaft profile are quiet a bit different. if thats the case then youll need to do some Ve table work as well. It is also possiable that your headers are cuasing trouble.

polygaryd

hey guys thanx for all the info so far. i have flowtech shorty headers the o2 sensor is in the collector but it is very close to the stock position that it would be in if the manifolds were in the car. i dont think i need a heated o2 sensor. my motor runs mint by the way no lopey idle or anything. the sd conversion could be a problem. i am looking into it.

kevm14

No misses or other lumps (caused by incomplete burn) at idle though?

funstick

fp check. what model year is the engine originally ? what camshaft is in it flat tappet or roller and is it a stock cam ? theres are things that will cuase some trouble. is you base timming at 6btdc ?

polygaryd

my motor is totally stock for my 87 GTA besides the mods i listed. the cam is stock and the engine is original from 87 i would assume i never changed it. i really dont know though since i am not the original owner. i am assuming since i didn't do anything to it, it is stock

polygaryd

yeah i dont dont know how to do ve table work either maybe you guys could help me with that. because i do have a pre '88 and i did convert it to sd with the help of the article on this website so that very well could be the problem. and i have no misses that i can tell. seems to run awesome i watch the rpm guage and it is steady as could be also i listen and fell for lopeyness but i cant seem to find any

anesthes

iTrader: (12)

Ed's right, but i'll add my 2 cents:

Unless your running 9's in the 1/4; your idle, and most part throttle should be well within emissions.. PE is for making power.
Somethings wrong with your engine (i.e, vac leak, egr not working, injector leak/sticking, etc), or your emissions hardware (air pump, diverter, catalytic converter, etc)

Another thing. I've found with testing, messing with the AFR doesn't do anything. The code isn't designed to work with true AFR.. It toggles, and it really can't toggle much beyond stochi (in any direction). You're better off forcing open loop, if a dramatic change in AFR is desired - but again, fix your mechanical stuff first.



-- Joe

funstick

nah long tube headers really strugle with emissions. O2 sensors also struglle with them alot. i wind up tunning alot of cars open. loop. or i force the blm to 128 as the minimum entry. also if your trying to idle and engine at say 13.6 having the BLM/INT correcting it back is a pita. i like leaving the fuel trim in tact in casethe engine runs lean or something bizare happens but if im trying to get the bastard to run richer in a few places then i just lock the BLM lower limit to 128 and the IT to 128. although since you have shorty headers i highly doubt your having the o2 sensor cooling loses and transport delays i always seem to have to battle with.

polygaryd

hey guys more troubles for my car.. i turned down the air fuel mix to 14.5 to try to richen it up like you guys advised and guess what my car still fails like there is no tomorrow. i changed the oil again and went to get it inspected it now tested with 471 hydrocarbons at idle much more than last time. i dont get it... what could be wrong. i am looking to you guys so i dont have to go the dealer and pay out the butt for parts and labor.

anesthes

iTrader: (12)

Dude.

go into your prom, change open loop enable to be like 255 degrees f.. Modify your injector constant, if its 22 make it 23.

Your HC's are showing too much fuel. you need to lean it out.

The afr code doesn't do anything. You need to force open loop, and adjust injector constant.

-- Joe