Used 18mm Engine Comparisons

On the forums, questions come up about the differences between Estes and Quest 18mm engines. 
Here's two fired 18mm engines.
An Estes B6-4 is on the left, a Chinese made Quest B6-4 on the right.
The Estes engine burns cleaner, the Quest nozzle is black and sooty.

Inset picture, view from the top of the engine,
The Estes ejection has blown the clay cap out and off the engine.
The card stock ejection charge cap usually stays in the Quest engine. It can pivot and let the ejection charge blow by.

From the side,
The Estes engine is almost 2 3/4" long.
The Quest engine is 2 11/16" long.
There is a little "play" (slides up and down) in the Quest engine when a standard engine hook is used.

The Quest stick on label is sometimes removed, if it was applied loose and prevents the engine from an easy insertion into the engine mount tube.
Quest engines can leave soot inside and around the rear of the rocket. The Quest ejection charges are not as strong as the Estes.

TIP: The Quest engines work best in shorter, smaller diameter models that don't require a large interior area to pressurize at ejection.
TIP: The Quest B6-4 engines can boost your rockets higher than an Estes B6-4.
Don't use Quest C6 engines in heavy or odd-ball rockets. The longer burning Quest C6 engines do not have the boost strength of the Estes C6 engine.