1992 Mazda Miata, 1.6 Liter Engine 94,000 miles, Stock engine has very low power.

So my car passed the smog test with the timing set at 16 degrees btdc. The correct timing should be 10 degrees. I tried to test at 12 degrees which is acceptable limit. The smog technician said he could not get the car to run at 15 mph in second gear. "I had my foot to the floor" these cars historically have no bottom end power. Did he shift from first too early? Is there an RPM limit for the test? Will a different final drive ratio affect test?

Answer:

The smog technician probably shifted from 1st gear to second gear because the smog machine has a specific RPM (approx. 300 +/-) requirement during the 15 mph portion of the enhanced smog test. Your Mazda may have very well turned the dynamometer, but only in first gear and with the rpms too high; and so the technician switched to 2nd gear and your Mazda was unable to perform. The smog machine is calibrated to require a specific rpm during both the 15 mph and 25 mph portions of the smog inspection. So... The fact that your Mazda was having trouble turning the dynamometer in 2nd gear indicates trouble with the engine, or since you pointed it out, a drive train ratio problem. If you have made modifications to the drivetrain, we have to recommend you switch back to the stock system. Assuming your vehicle has no emissions related problems there should be no reason it should have trouble performing on the dynamometer.

posted by SmogTips Support