Our goal at Mac's Products is to provide you , the modeler, with the finest exhaust systems available anywhere at any price -- at no compromise to quality. Mac's Products is dedicated to designing and building the best exhaust systems for airplanes, boats and helicopters.

We test our products on the latest engines to generate the most accurate tuning information. The purpose of this tuning page is to help the modeler in tuning his exhaust system.

Tuning the exhaust system is actually quite simple. Tuning is determining the length of the system at which the engine achieves the best RPM for your application. In case you have an engine for which there is no tuning suggestions available, we suggest you first break the engine in properly, trying to have at least 30 minutes of running time. Some engines need to have special treatment at the beginning, in which case you need to consult the manufacturer's suggested break-in instructions. Next, run the engine at full speed, open-face (with nothing attached to the exhaust, although this may not be possible with some engines whose carburators require muffler pressure, in which case we have actually hand-squeezed a sealed fuel tank - PLEASE UNDERSTAND, anything above open-face is tuned. How much above open-face is according to the capability of the motor, exhaust system & ect. and what you want to do within your application). Next, put the full-length header and tuned pipe on the engine and run it. If the RPMs are less than the open-face reading, cut 1" off the header (1.5" for engines over 1 cubic inch) until the RPMs are above the open-face reading. Then cut the header .25" until maximum RPMs. Or, when the next cut causes a decrease in RPMs, this is the best tuning length for static and vertical performance (fun flying, aerobatics and hanging it on the prop).
(Please note! Inside the silicone tube, the header tube and the front of the tuned pipe should very close together, but not touching, about 1/8" apart.)

Unless you were really hanging the airplane on the prop, the 4" length would be close to be giving you the maximum vertical performance, and would therefore be an excellent tuning length for your airplane.

The exhaust system consists of the header (which attaches to the engine exhaust), the silicone tubing (connector), and the pipe. The exhaust system not only reduces sound, but, when tuned to the correct length, will increase the engine's RPM.

We test our products on the ground and in the air. Our ground testing is done on a test stand. We mount the engine and exhaust system and record the engine's RPM. We start with a full-length header, cut it off in 1/4" increments and record the RPM at each point. We then plot a chart for each engine.

Our headers are full-length to cover those model applications that need extra length. You can run the header full length, but your total system length will be longer than most engines require for tuning. Your engine will perform well, but your system will not be producing all the power that it is capable of. The header is the easiest part in the system where length adjustments can be made.

We provide the chart below to show you the correct header length to produce a tuned system. Look up your engine and find the recommended length. This length is measured from the front of the header mounting plate along the length of the header tube. Refer to the diagram below for more information. Use a tubing cutter or hack saw to cut the header. File the sharp edges inside and out. Wash the header with soap and water to remove all filings and dry thoroughly. Connect the system and mount it securely. YOU ARE NOW READY TO RUN.

Since engines and propellers vary, we suggest that to start, you cut the header 1" longer than the peak RPM length indicated on the chart.

NOTE: This information is only to aid the modeler in tuning. As each engine will vary in performance and since slight changes in engine manufacturing may cause significant differences in tuning, Macs Products cannot be held responsible for any variances.