VegasInvasion

I'm only one man and there are many states I can't reach to make this possible, so here's my guide on emissions tuning for modified cars. I do this professionally for GravityImports.com

Foreword: If your engine light is on and you don't know what the code or the problem is, this guide is way over your head. Fix your car first.

OBJECTIVE

The emissions process cumulatively sums and periodically polls all the data. You want to give them the least amount of data in order to pass.
Spend as little time accelerating as possible so the cumulative CO2 and fuel samples (CO) stay low, without using so much power that the polled data is too high.
Keep enough ignition advance to curb all unburned fuel (HC) output.
Keep AFRs and ignition reasonable enough to avoid high combustion temperatures (NOx).

PREPARATIONS

1.) You must run in closed loop (after tuning of course). A wideband is preferable, but many cars can get by on the stock O2. Many states require a post-cat O2 (96+), however they rarely check to see if it's operating, just that it's installed.

2.) For lightly modded cars, all you should need is a stock map with an active O2, so ignore the rest of this if you're just running bolt-ons.

3.) For turbo, remove the wastegate spring - for internal gates, disconnect the arm so the flap stays open. We need to reduce the airflow as much as possible without choking. If you have stock injectors available, you may even pass as-is with a stock map and stock O2.

4.) For compression over 12:1, good luck you might want to see if you qualify for an alternative fuels exemption (ethanol). Using two cats on E85 worked for me on a 12.5:1 GSR, otherwise you'll have a difficult time not burning a ton of pump gas or risking knock which spikes NOx levels.

5.) Use a 190-degree thermostat. Hotter engines burn less fuel - if you don't pass on higher compression, use a 170 thermo. The more restrictive your intake is, the less fuel you'll need. Same goes for exhaust.

6.) If you have an aggressive cam, there's a fair chance you won't pass. Use stock cams if possible, or retard them with cam gears. For SOHC, retard the cam 8 degrees, make sure you're not getting piston contact. For DOHC, retard the intake cam 8-10, but leave the exhaust cam closer to 0 so we can burn that combustion longer.

7.) Don't forget to set your base distributor timing to OEM spec.

8.) Use premium fuel. It burns cleaner, leaner, and give us more wiggle room. It may increase CO, but usually not enough to fail you if it's tuned right.

BASIC TUNING PROCEDURE

1.) Set all your targets under 60% throttle to 15:1 AFR - most of the smog test is done in part throttle. If you find you're accelerating very slowly or hesitating, do not add ignition yet - just add fuel. If you're exceeding 13.5:1 AFR and you're still slow to accelerate, add ignition and reduce fuel if possible - keep in mind this may increase NOx - probably not by a huge value though especially if you're running ethanol.

2.) None of the smog test should really require more than 60% throttle, but if it does, try to target 14:1 AFR, or 13.8:1 if you find yourself flooring it to get anywhere. If you're not hitting atmospheric pressure with the wastegate open, you have little choice but to re-spring and hope they don't rail on it, or throw on a stock header.

3.) For high compression, you have to maintain normal target AFRs. You can try to lean out (let's say 10%) and retard ignition (say 5*) to reduce CO but you may run into a higher HC reading since you'll have to spend more time accelerating. Cam angle adjustments can help with that. You can then advance ignition, but if you end up with high HC or CO in conjunction with high NOx, it's time to upgrade the cat and revert to richer numbers.

4.) Some engines or dished pistons under 9:1 CR will experience bucking or hesitation when using stock ignition tables. You should have plenty of room to advance 3-5* without compromising NOx due to the extra room in the combustion chamber.

CONCEPTS & DIAGNOSTICS

1.) Again these are the three main readings to consider:

a. HC (Hydrocarbons, AKA fuel in vapor form)
*Typical causes of high HC with high CO:
- Vacuum or exhaust leaks cause the O2 to overcompensate
- Misfire due to ignition components (spark plugs, coil, ICM, crank sensors, wires), compression/ head gasket issues, or faulty/ leaky injectors.
- A bad/unplugged sensor (O2 or temp) or bad wire causing invalid readings which dump tons of fuel.
- High or low battery voltage or bad ground/ main relay.
*Causes of high HC with low(er) CO:
- The catalytic converter is not converting HC into CO. Replacing or adding an extra one is sometimes all you need, especially if you have an eBay "high flow" cat.
*Causes of high HC and high NOx:
- Misfire, bad injector, vacuum leak
- Engine knock and/or a bad tune
- Bad temp sensor or overheating - never trust the cluster ECT gauge, it's never right.
- High backpressure due to a clogged cat
*How to manually lower HC:
- Reducing fuel delivery by means of fuel pressure, injector size, fuel maps/tuning
- Advancing ignition keeps HC in the engine longer to burn it off before it exits - this can also raise NOx. Be sure your NOx readings are super low before advancing ignition.
- DO NOT add Heet or E85, this is a noob hack and could damage your engine.

b. CO (Carbon Monoxide, a product of burned fuel)
*Typical causes of high CO with low HC:
- Your cat is working but you're just too rich, this is typically combined with high NOx due to advanced ignition, a sensor malfunction, a bad injector, or bad fuel.
- Cams are too advanced or cam timing is off.
- Burning oil or coolant
*Causes of high CO and high NOx:
- Bad tune, cams are too advanced, or spark plugs are too hot.
- You're using ethanol or Heet when I told you not to.
*How to manually lower CO:
- See high HC, do not advance ignition.

c. NOx (Nitric Acid, a result of high combustion temperatures)
*Typical causes of high NOx with normal HC and CO:
- Engine knock, cooling system error, or very high intake temperature.
- Exhaust backpressure


--- Feel free to add to this or ask questions, I'm sure I'm missing something.

raverx3m

iTrader: (1)

I would have to disagree on isoheet
I passed 2 cars like that
half a tank and 2 cans of isoheet dropped emissions almost in half car didn't run right at higher throttle because of different burning properties of alcohol but it passed with amazing results

then one time I overdid and put 2 cans of isoheet in less than a 1/4 tank of gas. car stumbled when driving and failed idle also but passed cruise

so don't stuff that sht in there

also do not use bosch sensor I used it twice with bad results
switched to oem or NTK sensor and problems went away(yes it was the correct sensor for my car according to bosch)


import tuner tested different tricks to pass emissions

http://www.importtuner.com/tech/impp...missions_test/

raverx3m

iTrader: (1)

ok finally found another article to confirm

my downstream sensor output mirrors the upstream sensor with a slight delay which means dead catalytic converter...

heres another good article
http://www.totalcardiagnostics.com/s...er-diagnostics

OneBadTurboCRV

That could have been confirmed with an infrared temperature gun. Exit should be hotter than inlet.

I haven't studied the write-up yet, but great job for posting!

raverx3m

iTrader: (1)

i borrowed a shop obd2 scanner that reads graphs in real time but couldnt find where it said how the downstream output should look like. with working cat it supposed to be stable and not fluctuate like the upstream one.

but i also might have some injector issues too lol.

the second one tells how to perform tests and what to look for pretty detailed

VegasInvasion

Raver, Heet is full of ketones, which not only corrode your fuel system but burn much faster and can grenade a tuned engine. Yes, it can make some poorly running cars pass, but that's not how I do things in my business.
This thread isn't meant for noobs with stock cars, it's meant for people who want their performance builds to beat smog the right way, safely.

Bosch narrowband sensors ARE garbage, but most performance cars will need a wideband to properly tune for emissions anyway.

Good call BadTurbo, a temp gun is a great way to test for a bad cat. I'm not sure why they don't do it at the emissions centers.

PhilDrach

Guys, I have a 1995 Honda Civic and it has failed its last 3 emissions test because of high CO levels. I need tog et it under 1.07%. The first time it was at 2.8%, then 2.6%, then 2.0%. I have been going to a local shop and I trust the guy. He has replaced the O2 sensor. He also cleaned out the catalytic convertor because there was a lot of carbon build-up in it and he told me to keep filling it up with premium gas and to put in an engine cleaner when I go and fill up and then to keep driving it a lot before I get it tested again.

Now I was at Valvoline the other day getting an oil change and I asked the guy about it and he said that in Honda's over time the "idol control solenoid" goes bad and makes the engine sound like: . It has been doing this ever since I was handed the car down to be from my sister. Now I know nothing about this and the guy at Valvoline told me to bring it someone who works with Hondas and just tell him about the idle control solenoid and he will know what to do about it.

Any one know what I'm talking about and provide some input for me?

VegasInvasion

This isn't an open thread for troubleshooting basic emissions issues, but since you already posted, you have a vacuum leak. Search the forums and you'll find a solution for it.