Twenty years of reengined tug

[David Isaac]

Is this Chev engine a true LS1 or is it substantially modified? What have they done with the cam timing have they had to close up the lobe centres to get the torque / power they need at 4500 WOT. Is it computer controlled and injected or mechanically controlled and injected? I would assume the former. This is obviously at max power output at that RPM which is limited by prop pitch.

 

We used to do similar things to these and Ford push rod V8 engines in Jet Sprint Boat racing and we had special cam grinds that closed up the load centres so we were getting nearly 400 HP at 4500 RPM but they were right on the detonation limit which is not what you wanted in an aircraft engine (and we used Avgas). They also had a pretty rough idle, difficult to start due not a low enough manifold pressure at start, would flood easily and be difficult to restart flooded and used huge amounts of fuel. So the fuel consumption per HP on the Chev would probably be similar to the Lyc in an aircraft application ... is that he experience?

 

What is the TBO on the LS1, we have been told it is 1,000 hrs on the Ford V6 ...

 

 

[Exadios]

Is this Chev engine a true LS1 or is it substantially modified? What have they done with the cam timing have they had to close up the lobe centres to get the torque / power they need at 4500 WOT. Is it computer controlled and injected or mechanically controlled and injected? I would assume the former. This is obviously at max power output at that RPM which is limited by prop pitch.We used to do similar things to these and Ford push rod V8 engines in Jet Sprint Boat racing and we had special cam grinds that closed up the load centres so we were getting nearly 400 HP at 4500 RPM but they were right on the detonation limit which is not what you wanted in an aircraft engine (and we used Avgas). They also had a pretty rough idle, difficult to start due not a low enough manifold pressure at start, would flood easily and be difficult to restart flooded and used huge amounts of fuel. So the fuel consumption per HP would probably be similar to the Lyc in an aircraft application ... is that he experience?

 

What is the TBO on the LS1 we have been told it is 1,000 hrs on the Ford V6 ...

This and [usr=http://http://www.vansairforce.com/community/showpost.php?p=231798&postcount=10]this[/url] may answer some of your questions.

 

 

[David Isaac]

Thanks Exadious,

 

Apparently they are stock factory with extra refinement in the fuel air ratios on the factory computer.

 

 

[Guest rrobut]

With all the chat about the ls1 in the pawnee I had to post a reply and quell the misconceptions.

 

I speak with some authority since I am the person who supervised the installation and did the test flying of the Kingaroy Pawnee pictured above.

 

There is a Pawnee with an ls1 V8 flying at Benalla. It was at Lake Keepit a few years ago but they were not happy with it so it moved to Benalla where everyone is very happy with it's operation. The installation was done by a Lame in Bundaberg over a 12 month period, commencing inJune 2005.

 

The V6 installation proved the concept of auto engines for glider tow operations.

 

The PSRU is a Northwest Aero products psru with a 2:1 belt reduction drive (They are no longer in production)

 

The RAA instructor at Dalby does have an engine and psru for sale but he has not done any installations for DDSC gliding club

 

The engine is standard.we felt that no mods were required since the power output at around 4200rpm is about 260hp and we do not need more than that so the engine is operated de rated. This rpm is also about the top of the torque curve.

 

It operates normal computor controlled fuel injection.

 

Normal take-off rpm is 4300, but go thru the gate on the throttle and you get 4400rpm

 

The climb rate with a glider attached is 600-650fpm.We recently did a tow to just under 10000ft and the tug was airborne for 18mins.13mins for the tow up and 5 mins to get back on the ground.And that was in still air at 5:00am.

 

We often reduce the rpm to 4000 when airborne and still get 600fpm.

 

Normal lycoming driven Pawnees average 8 tows/hour if the club is looking after the engine correctly on the descent.

 

We are getting at least 11 and sometimes 12tows/hour, because we can close the throttle at glider release and not worry about shock cooling.

 

rate of descent at 80kts about 1800fpm with that big (84inch) prop out the front windmilling and providing the drag

 

We burn 95 octane unleaded (50cents/litre cheaper than avgas at the moment).fuel burn is about the same as the o-540 pawnee.

 

We are running a little richer mixture than would be used in a car to guard against pinging and detonation.

 

The engine is so nicely engineered that I wouldn't be surprised to get 2000+ hours TBO.We do not have anything specified.

 

R

 

 

[Guest ozzie]

I seem to recall that Southern Cross at Camden had a V8 Pawnee in the early 90's.