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flamini2(at)COMCAST.NET
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 Posted: Fri Feb 09, 2007 6:47 am Post subject: Exhaust test |
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Not as fast as a Tailwind but interesting;
Dennis in Chicago
RESULTS OF EXHAUST SYSTEM TESTS (January '07)
I decided to conduct a comparative test of three different types of exhaust systems available for the RVā€™s. The 4 into 1 collector system, the standard crossover system and the 4 pipe system. Each of these systems had previously been installed and flown a minimum of 50 hours on my RV-7A. Each one of these systems are considered standard exhausts for the RVā€™s.
The tests were conducted using the Flight Data System (APF 30) in the aircraft. It was my goal to measure True Airspeed, fuel burn, EGTā€™s, gallons per hour, percent HP, and also monitor engine smoothness with each system. It was assumed that any instrument error would be the same for each system so it was not a concern. It was not a goal to measure the different sounds or noise levels that each system produced. The results on the RV-7A, I0-360 M1B engine, 265 hrs.total time, with ECI Titan cylinders are as follows. All flights were at 8000 ft. density altitude (taken from the Flight Data System) and full throttle
System 1: 4 into 1 collector This system required cutting a hole in the bottom cowl and bringing it out beside the nose gear. I then spent a number hours fabricating a fairing around the collector and tail pipe. I wanted a smooth fairing to get all the speed that I could.
Density Altitude 8000 ft. OAT 23.0 F. RPM 2400 MP 21.9in.
EGTā€™s #1 1270 #2 1340 #3 1277 (at)4 1308
IAS 179MPH TAS 202MPH GPH 10.0GPH 71% power
Note This RPM produced a rough engine.
RPM 2500 MP 21.9
EGTā€™s #1 1263 #2 1322 #3 1265 #4 1298
IAS 182MPH TAS 206MPH GPH 10.6 73% power
Note The engine was smooth at this RPM
RPM 2600 MP 21.9
EGTā€™s #1 1265 #2 1325 #3 1271 #4 1294
IAS 186MPH TAS 210MPH GPH 10.9 76% power
Note The engine was very smooth at this RPM
System 2: Standard crossover for the M1B engine. No cowl modifications required.
Density Altitude 8000 ft. OAT 8.4 F RPM 2400 MP 21.3 in.
EGTā€™s #1 1294 #2 1293 #3 1249 #4 1255
IAS 180 MPH TAS 202 MPH GPH 9.4 70% power
Note: The OAT was somewhat lower than in Test #1. Engine was smooth at the RPM.
RPM 2500 MP 21.3
EGTā€™s #1 1305 #2 1291 #3 1250 #4 1250
IAS 182 MPH TAS 204 MPH GPH 10.2 72% power
Note The engine was smooth at this RPM
RPM 2600 MP 21.3
EGTā€™s #1 1309 #2 1292 #3 1260 #4 1256
IAS 184 MPH TAS 208 MPH GPH 10.7 75% power
Note The engine was smooth at this RPM. The flight data system oscillated between 208 and 209 MPH so I used the lower number.
System 3: 4 pipe exhaust. No cowl modifications required.
Density Altitude 8000 ft. OAT 32.7F. RPM 2400 MP 22.4
EGT;s #1 1315 #2 1303 #3 1299 #4 1265
IAS 178 MPH TAS 202 MPH GPH 9.8 71% power
Note The engine was smooth at this RPM
2500 RPM MP 22.4
EGTā€™s #1 1315 #2 1303 #3 1299 #4 1266
IAS 183 MPH TAS 206 MPH GPH 10.4 74% power
Note The engine was smooth at this RPM
2600 RPM MP 22.3
EGTā€™s #1 1308 #2 1296 #3 1282 #4 1258
IAS 186 MPH TAS 210 MPH GPH 10.9 76% power
Note The engine was smooth at this RPM
The outcome of this test is somewhat in line of my thinking that most exhaust systems will perform about the same at power settings at or below 75%. Fuel burn may vary according to wx conditions and leaning techniques. My assumption is the variance in manifold pressures that were indicated are due to the different OATā€™s. Differences in EGT readings may be due to variations in probe locations on each system ie. The actual distance of the probes from the exhaust port.
The factory literature for the 7A shows the top speed is 210 MPH and this test is in line with that speed. We all want to go faster, but in reality a couple more MPHā€™s are hard to obtain and the answer may not be in the exhaust system alone but a combination of factors. I hope this test will help in selecting the right system for your aircraft- engine combination.
One test that I also conducted was to bring the throttle to idle during approach and landing to see if any of the systems would backfire and pop. I could not get any of the systems to do it as the fuel injection system (idle mixture) is set properly and there are no induction leaks on this engine.
Larry Vetterman , Vetterman Exhaust Inc. (vetxaust at gwtc.net)
related: Vetterman's section in Van's online store
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IslPilot(at)aol.com
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| Posted: Fri Feb 09, 2007 7:51 am Post subject: Exhaust test |
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so has Dave B put a crossover or 4-1 on your old steed?
tnx for the info.
Paul F. Baron
Cell: 773-551-3713
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