Seneca waste gate
 

Quick question.
Can't find it in the information manual.Anyone know what type waste gate system and control is used on the Seneca 2 TSIO-360 Continental eng's. Thanks in advance.

ummmm, there isn't one?

There is a fixed wastgate on the Seneca's I flew for my IR. Hence to set t/o power you advance the throttles only about half travel to get the 40" for take off power, but then every 1000' have to keep pusing them forward to maintain climb thrust. If you exceed 40" by much, a flap opens to prevent you overboosting the engines, and you get a yellow overboost light on.

C.............ough

Seneca 1's that I've flown weren't turbocharged.

Seneca 2 & 3's were. They used a fixed wastegate system + an overboost warning light & an overboost relief valve.

As I recall the warning lights came on at 39.8" & the valve opened at 42". Don't quote me though!

The Seneca 2 had 200HP at 2700/40", the Seneca 3 220HP at 2800/40" but that's time limited and 200HP at 2700/40" is max continous.

The wastegates had to be calibrated with maintenance test flights to ~12,000 to measure the MAP obtained at full throttlet then adjusted on the ground if necessary.

[This message has been edited by Tinstaafl (edited 30 April 2001).]

Sorry wasn't refering to a Seneca I(one) but a seneca that "I" flew!

It was actually a Seneca 2.....

C........ough

[This message has been edited by Cough (edited 30 April 2001).]

One of the big differences between the Seneca system and others that I've used is that there isn't a 'waste gate' in the normal sense of the word. On 'proper' turbocharging systems the waste gate allows exhaust gasses to bypass the turbocharger altogether in order to limit the boost and so you can firewall the throttles just like a normally aspirated engine. In the Seneca (and the Turbo Arrow) if you push the throttles open too far the turbocharger keeps on increasing the boost. The first you know is when the warning light comes on as you reach the max allowable MAP and then a relief valve opens downstream of the turbocharger to limit the overboost. This means that all the air that you've expended hard work on to pressurise is dumped so you actually waste power if you overboost. What a great system I don't think!

Seemed to remeber that the limit was 40", but the overpressure valves opened and the lights came on at 42" - i.e past the normal limits.

Refer to the 'What's your worst aircraft' thread in this forum for popular opinion on the Seneca!

Regarding the subject, Stan Evil post pretty much describe it. As far as I remember the max MAP on the PA34-200T was 40" (overboost light came on at 39,7") and the overboost valves opened at around 43" and the engines was allowed to run at 42" for max 10 sek, allthough 40" was SOP.

A wastegate is basicly a little piston that is controlled by a pin. There is a little pipe on the pressure side of the intakemanifold. This pipe end up in a regulator which is more or less a little
cylinder. The increase in press push this piston in and the piston is conected to a pin that regulate the piston in the waste gate, which bypasses a certan amount of exhaust around the turbocharger. When more press is required a spring draws the piston in the regulator back, causing the piston in the wastegate to close and more exhaust will come through the turbine, causing more press which again push the piston in the regulator, which again causes the piston in the wastegate to open and so on. Since this system is sensitive to wear, my personal belive is that continental have chosen to keep it simple an just fitted a overboost valve.

[This message has been edited by Danish Pilot (edited 05 May 2001).]