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 System Tuning the exhaust system is actually quite simple. Tuning is determining the length of the system at which the engine achieves maximum RPM. 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 tuning 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 1/2" 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. Macs Products Tuning Sheet Engine Side Std-Header Exhaust Propeller Pipe Open face Peak RPM Length ASP 40 RC Zinger 10 X 6 7.5mp 14,000 15100 6" ASP 46 (ABC) Zinger 10 X 6 7.5mp 13,900 14.600 4.375" ASP 61 Ring Zinger 11 X 7 10mp 13,500 14,800 4" ASP 61 (ABC) Zinger 11 X 7 10mp 13,150 14,700 3.25" Enya 40 CX Zinger 10 X 6 7.5mp 14,350 15,400 3.25" Fox 45 BBRC Zinger 10 X 6 7.5mp 14,250 15,100 3.375" Fox Eagle III Zinger 11 X 7 10mp 13,600 13,950 4" HB 61 Zinger 11 X 7 10mp 14,000 14,050 5.125" Irvine 40 R Zinger 10 X 6 7.5mp 13,900 14,600 3" Irvine 61 Zinger 11 X 7 10mp 13,150 13,750 3.25" K & B 40 RC Zinger 10 X 6 7.5mp 12,800 13,450 4" K & B 61 RC Zinger 11 X 7 10mp 12,500 13,200 3.25" Magnum 28 ABC Zinger 8.5 X 6 3.5mp 14,100 14,750 3.5" Magnum 45 ABC Zinger 10 X 6 7.5mp 14,750 15,600 3.625" OS Max 25 FSR Zingali 8 X 6 3.5mp 16,700 17,550 3" OS Max 28FH Zinger 9 X 6 3.5mp 13,300 15,600 3.5" OS Max 32F ABC Zinger 9 X 6 3.5mp 14,700 15,150 3.5" OS Max 32 FLTR Zinger 8 X 6 3.5mp 16,500 16,850 3.5" OS Max 40 FSR Zinger 10 X 6 7.5mp 13,850 14,650 3.5" OS Max 40 SF Zinger 10 X 6 7.5mp 14,500 15,200 3.375" OS Max 46 SF Zinger 10 X 6 7.5mp 14,500 15,250 3.375" OS Max 61 FSR Zinger 11 X 7 10mp 13,700 14,500 3.75" OS Max 61 SF Zinger 12 X 8 10mp 10,600 11,250 6" OS Max SFP Zinger 12 X 8 10mp 10,600 11,650 5" Rossi 40 R Zinger 10 X 6 7.5mp 14,600 15,250 5" Rossi 60 FIRC Zinger 11 X 7 10mp 14,100 14,900 3.5" Royal 40 RC Zingali 10 X 6 7.5mp 12,450 12,950 4.75" Royal 45 RC Zingali 10 X 6 7.5mp 13,850 14,700 4.25" ST S 40 Zinger 10 X 6 7.5mp 13,550 14,850 4.75" ST S 45 Zinger 10 X 6 7.5mp 14,650 15,900 4.25" ST S 61 Zinger 11 X 7 10mp 13,500 15,050 5" Webra 61F Zinger 11 X 7 10mp 13,900 14,550 4.25" Engine Rear Exhaust Propeller Pipe Open Peak RPM 0 Length Face Header Enya 60 XL Zinger 11 X 7 10mp 14,150 15,050 3.25" Irvine 61 R Zinger 11 X 7 10mp 13,200 14,250 4.75" OS Max 25 ABC Mas 8 X 6 3.5mp 17,400 18,600 3.75" OS Max 46 VF Zinger 10 X 6 7.5mp 15,100 15,850 2.5" OS 61 RF Zinger 12 X 8 10mp 10,900 11,300 6" OS Max 61 RFP Zinger 12 X 8 10mp 11,200 11,950 4.25" OS Max 61V Zinger 11 X 7 10mp 13,700 14,450 2.25" OS Max 65 Zinger 11 X 7 10mp 14,500 15,700 3" Webra 61 ABC Zinger 11 X 7 10mp 13,850 15,400 4.125" Webra 61 FBH Zinger 11 X 7 10mp 13,950 15,650 4.35" YS 60 Pumper Zinger 11 X 7 10mp 14,750 15,700 3"