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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.

PLEASE Note! MACS headers are not designed to support the tuned pipe or in-line muffler that they connect to the motor they are attached to. We suggest to double joint the Tuned Pipe system. Use two silicone connectors and an aluminum connecting tube between the shortened header and the tuned pipe. And then use that aluminum connecting tube to tune with (easier to take out and put back in than removing the header and put back in).

Tuning the 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.)

Example of theoretical engine XYZ .61

Open-face 14,000
Header full length
at 6.25"
13,800
5.25" 14,300
5" 14,500
4.75" 14,700
4.5" 14,900-
4.25" 14,900
4" 14,800

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.


Macs Products Tuning Sheet
Engine Side Exhaust Propeller Pipe Open face Peak RPM Std-Header
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"
MDS .68 FS Pro Zinger 11 X 7 10mp 13,700 14,600+ 3.5"
Megatech M61 Zinger 11 X 7 10mp 13,700 14,400 3.5"
MVVS 40 APC 10 X 6 7.5mp 14,600 15,700 5.75"
MVVS 40 Zinger 10 X 6 7.5mp 13,000+ 14,000 5.25"
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 FX Zinger 11 x 7 10mp 13,100 14,600 3.5"
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 61 SF-P 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"
TT Pro 120 Zinger 15 X 8 15qp 9,600 10,400 7.5"
Webra 61F Zinger 11 X 7 10mp 13,900 14,550 4.25"
UAV Webra 120 Zinger 15 X 8 15qp 9,800 10,600 6.75"
ThunderTiger .46 Pro Pending
ThunderTiger .61 Pro Pending
MDS .46 FS Pro Pending
MDS .58 FS Pro Pending
OS 46 FX Pending
OS 91 FX Pending
SuperTiger GS .45 Pending
SuperTiger 2300 Pending
Engine Rear Exhaust Propeller Pipe Open
Face
Peak RPM 0 Length
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"
OS Max 140RX APC 16 x 14 20ls-qp 7,800 8,700 7.25"
TT Pro 120R APC 16 x 14 20ls-qp 7,400 8,000 10.5"
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"
UAV 120 LS APC 16 x 14 20ls-qp 7,450 8,100 6"
YS 60 Pumper Zinger 11 X 7 10mp 14,750 15,700 3"




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Macs Products
7935A Carlton Rd.
Sacramento, CA 95826