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 maximum RPM. 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). 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).

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 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"

Return to Macs Products Home Page