carburation/exhaust hints please
Discussion
i decided to temporarily tweak my '84 turboEsprit to pass california smog check. i only care about getting carbon monoxide reading down the day of the test. since performance/economy is not an issue, does someone know a quick way to make the adjustment, hopefully without buying a manometer or CO meter. thanks everyone.
Given how stringent California emissions standards are, tuning by ear probably isn't going to get you there. And if you fail the first pass, doesn't that kinda put you on their radar screen forever after?
I suggest you either take it to a shop that can to an emissions tune-up on it, or beg/borrow/buy a CO meter. A 4-tube manometer would be good as well.
Is the engine stock... cam timing, ignition timing, air pump, carb jetting?
If CO is high, then the mixture is rich. And if the engine runs great, then the mixture is most likely too rich to meet Calif emissions standards.
However, if you start leaning out the idle mixture and go to far, then the HC will go up. There's a sweet spot you can't just see or hear, so trying to dial it in without a CO meter is risky.
If you tune the mixture for best running since that's easiest to hear, then it's too rich. From there, lean the mixture until the engine begins to miss or run rough. Then it's too lean, misfiring and the unburned fuel spikes the HC. Somewhere in between best running and too lean is where you want to be. I can't tell you where that is... you need a CO meter. But generally speaking, as lean as possible consistent with smooth, even running. Each misfire is a spike on the HC scale and will kill you during the test.
Good carb balance will have a lot to do with smooth running, and smooth running will keep HC down. That will make it easier to lean the engine a bit more in search of the CO reading you need without failing HC. The manometer will make balancing the carbs much easier, but you can get close by using a rubber tube to listen to the hiss volume in each barrel. Of course, you would have to remove the plenum to do that.
General guidelines...
If the CO is high:
1. Air cleaner dirty, or airflow restricted
2 Oxygen sensor malfunction, doesn't apply.
3. Choke stuck or out of adustment.
4. Devective PCV valve, doesn't apply.
5. Devective charcoal canister
6. Imporper idle speed
7. Idle mixture too lean.
8. Dirty or leaking carburetor
9. Improper carb float level
If the HC is High:
1. Fouled plugs or defective wires, cap or rotor.
2. Improper ignition timing.
3. Vacuum leak.
4. PCV or EGR valve malfunction, doesn't apply.
5. Mxture too lean.
6. Misfire (loaded).
7. Inoperative air pump.
8. Weak cylinders - low compression, valves, rings.
If CO and HC are High:
1. Oxygen sensor malfunction, doesn't apply.
2. Mixture too rich.
3. Ignition problems (primary or secondary).
4. Carburetor malfunciton.
5. Vacuum leak with rich mixture.
6. Excessive fuel pressure (regulator).
Good luck,
Tim Engel
Lotus Owners Oftha North
I suggest you either take it to a shop that can to an emissions tune-up on it, or beg/borrow/buy a CO meter. A 4-tube manometer would be good as well.
Is the engine stock... cam timing, ignition timing, air pump, carb jetting?
If CO is high, then the mixture is rich. And if the engine runs great, then the mixture is most likely too rich to meet Calif emissions standards.
However, if you start leaning out the idle mixture and go to far, then the HC will go up. There's a sweet spot you can't just see or hear, so trying to dial it in without a CO meter is risky.
If you tune the mixture for best running since that's easiest to hear, then it's too rich. From there, lean the mixture until the engine begins to miss or run rough. Then it's too lean, misfiring and the unburned fuel spikes the HC. Somewhere in between best running and too lean is where you want to be. I can't tell you where that is... you need a CO meter. But generally speaking, as lean as possible consistent with smooth, even running. Each misfire is a spike on the HC scale and will kill you during the test.
Good carb balance will have a lot to do with smooth running, and smooth running will keep HC down. That will make it easier to lean the engine a bit more in search of the CO reading you need without failing HC. The manometer will make balancing the carbs much easier, but you can get close by using a rubber tube to listen to the hiss volume in each barrel. Of course, you would have to remove the plenum to do that.
General guidelines...
If the CO is high:
1. Air cleaner dirty, or airflow restricted
2 Oxygen sensor malfunction, doesn't apply.
3. Choke stuck or out of adustment.
4. Devective PCV valve, doesn't apply.
5. Devective charcoal canister
6. Imporper idle speed
7. Idle mixture too lean.
8. Dirty or leaking carburetor
9. Improper carb float level
If the HC is High:
1. Fouled plugs or defective wires, cap or rotor.
2. Improper ignition timing.
3. Vacuum leak.
4. PCV or EGR valve malfunction, doesn't apply.
5. Mxture too lean.
6. Misfire (loaded).
7. Inoperative air pump.
8. Weak cylinders - low compression, valves, rings.
If CO and HC are High:
1. Oxygen sensor malfunction, doesn't apply.
2. Mixture too rich.
3. Ignition problems (primary or secondary).
4. Carburetor malfunciton.
5. Vacuum leak with rich mixture.
6. Excessive fuel pressure (regulator).
Good luck,
Tim Engel
Lotus Owners Oftha North
Gassing Station | Esprit | Top of Page | What's New | My Stuff