since 1940

Aircraft parts
for those who work on airplanes

  Home |  Software | Knowledge Base |  Customer service |  Products  

Home> Continental & Lycoming TroubleShoot

Split manifold pressure on twin engine aircraft 

. On twin engine Lycoming Turbocharged aircraft using the TIO-540 engine, during full throttle operations, differences in manifold pressure between engines may be acceptable as indicated between maximum and minimum on the manifold pressure tables of Lycoming Service Instruction 1187G. This is typical of normal operation of the density controllers as they respond to slight differences in induction air temperature caused by filters, heat soak and other variations in the induction systems. These engines use heat shields on the exhaust pipes to shield the induction tubes. If the shields are missing they will cause an induction air temperature difference and corresponding difference in density controller operation between one engine and the other. This will be seen as a difference in manifold pressure. If differences exceed the values shown in the manifold pressure tables of S.I. 1187G then check for proper installation of heat shields.

1. Propeller blade angle not adjusted properly.

2. Controllers out of adjustment.

3. Excessively dirty air filter. Problem may be more noticeable when aircraft is flown to altitude because of the decrease in air density.

4. Alternate air door leaking. Although door may appear to close on the ground, it may be opening slightly in flight due to vibration or air currents. To determine if this is happening, tape the alternate air door shut and fly aircraft to altitude and observe manifold pressure. Be sure to remove tape upon landing.

5. Incorrect hydraulic lifter's or hydraulic lifter's bleeding down too rapidly. On turbocharged engines, manifold pressure will come back together when pressure gets above 30 inches.

6. Restriction in airframe or engine induction system. 

 

distorted wye pipe Piper Seneca II

 Aircraft: Piper Seneca II  powered by the continental TSIO-360-E engine which uses the rajay turbocharger and a fixed wastegate.

Symptoms: Throttles, Manifold pressure, RPMs and fuel flows equal on both engines from sea level up to 8,500 feet (sea level temps were apx 85F)

At 8,500 feet you would have to increase throttle on the right engine to maintain the same power (MP) as the left engine

At 10,000 feet the right engine would not develop rated HP, even at full throttle and at this point there was I would say a 3" split in the throttles.


The pressure relief valves had been checked, the induction system including the alternate air doors had been checked for leaks and the air filters were clean etc.


After the defective wye pipe was changed the throttles stayed together and the right engine would develop rated horse power. 
New and old wye pipe on Piper Seneca II
New wye pipe

7. Leaks in airframe or engine induction system.

8. Sticking wastegate.

9. Incorrect (wrong pressure) spring on wastegate actuator.



 

 
 

 

 

 

online privacy policies 
 site terms of use
terms and conditions of sale

 Information about how to download this site for off-line reading

  Webmaster: john@sacskyranch.com 

Copyright 2003 by Sacramento Sky Ranch Inc. All rights reserved.  Prices subject to change without notice. Not responsible for typographical or misprint.
Disclaimer: sacskyranch.com contains abundant information relating to aircraft maintenance. The information provided  is not intended to supercede or supplement the F.A.A. approved  maintenance and/or operator’s manuals. Those F.A.A. approved manuals must be utilized when performing maintenance and/or operating aircraft.