In April 1952 the DSpr.2 proved this modification impressively in Comet demonstration with clean exhaust.

All final designs have to meet NASA's goals for less noise, cleaner exhaust and lower fuel consumption.

While possibly grating, Mr. Seaton says the whine is worth tolerating for the improved mileage and cleaner exhaust.

I had blown the stack, used live steam to blast clean the exhaust.

Hot-bulb engines also produced cleaner exhaust fumes.

Nevertheless, catalyst-equipped engines produce cleaner exhaust than lean-burn engines.

At the same time, emissions regulations were demanding cleaner exhaust.

Combination of exhaust particulate filter and catylist makes exhaust very clean.

I just felt I ought to get out and fill my lungs with some good clean exhaust fumes.

This results in a very clean exhaust (second only to cryogenic LO/LH) and a distinctive clear flame.