Jacked69

I was wondering about something, when I work my way up to my TF p-51 that has a barley used 100 series knight engine in it, well when I get the handle on her hopefully in the spring would I notice a difference between a knight 100 and knight 120? If so how much of a speed difference would I expect? Also does anyone know what the top speed of my p-51 will be with the 100 in her? Just asking so I kinda have an idea how close my sim is to what she will do in real life. Thank you all very much....

hogflyer

What is a knight 100 and knight 120? Are you referring to a Saito Golden Knight 1.00 and 1.20?

Hogflyer

bruce88123

Obviously the plane will be faster with a 120 on it but you are allowed to reduce the throttle. The biggest difference will be on takeoff due to a shorter takeoff and better climb but there will also be more engine torque to fight during takeoff. Prop will probably be slightly larger which will reduce ground clearance a bit. Once up and flying you won't really notice the extra speed all that much as far as being harder to handle. The time to turn around will just happen more quickly. Again, use the throttle. It may not want to slow down for landing as well either but you can do a few things to improve that too.

carrellh

Does the model balance correctly with the existing engine? Is there any nose weight on the plane to get it balanced? There is a reason for these questions.

According to the Horizon web site, the Saito FA-100 weighs 20.9 ounces including muffler
The Saito Large Singles manual says the 120 weighs 820 grams (about 29 ounces) and I think that does not include the muffler.

So, you'll be adding about 10 ounces of engine weight to the nose of the plane. If there is no weight you can remove, you will increase the total weight of the model by 10 ounces. If you cannot move the battery pack far enough toward the tail to offset the increased nose weight you will have to add even more weight to the tail of the plane to get it balanced.

Jetdesign

My Feedback: (8)

What is the reason for changing engines? Do you just want more speed? A comparable two stroke might be a better answer, and save you some money.

ChuckW

You'll be able to spin larger and/or more aggressive props with the 1.25. This, in theory should give better performance. As Bruce88123 pointed out though, there is a weight penalty and that may or may not cancel out any gained performance. You'll also run into balance issues. Those are correctable of course.

the 1.00 will be great. I fly mine with an OS .91FS and it is plenty fast.

Take your time in working up to that Mustang. It is not a beginners plane by any stretch of the imagination. I've gotten a number of flights on mine now and I will say that it flys wonderfully once in the air. I haven't flown many planes that were as stable and smooth. Taking off and landing are another story however. It is a scale P-51 which means it is very squirelly on the ground until you have some speed and the rudder becomes effective. Landings generally need to be a little "hot" which means chopping the throttle to idle isn't always the best option. You also have to be sure to get the touch down just right or it can bounce like a basketball or nose over. That's the nature of warbirds. Not trying to scare you, it is all learnable. Just don't try it too soon and destroy that beautiful airframe.

ChuckW

I think people have been hanged for putting 2-strokes on warbirds. It is just wrong except for large gas engines.

bingo field

He might have thought of pylon racing.....

Jetdesign

My Feedback: (8)

Who said anything about a two stroke? [8D]

RCKen

My Feedback: (9)

If speed is what your final goal is then moving to a 2-stroke will produce more results than increasing the size of a 4-stroke engine. 4-strokes produce more torque and power than a 2-stroke will, which gives them great pulling power. However, a 2-stroke is high revving and will give more overall speed.

Ken

Jester241

I have a 66" hanger 9 P-51 with an VERY powerful O.S. 1.20 surpass. The only good thing about this big engine crammed,and I mean CRAMMED in it is that if your really screw up a take off(which is easy to do with a p-51),you've got the power to pull out of it.

The bad part about that big of an engine is that you run a big prop which makes it(at least in my case) VERY hard to slow up enough for landing unless you've got a big airfield. Not to mention P-51s are known for "nosing" all the time. And with an even bigger prop,your gonna break even more props.

So,stick with your 100......if your think later you need more power,then go bigger. I dont think you'd notice much difference anyway.

ChuckW

Another thing to consider is that the engine is just one part of the speed equation. Props play a role as does the shape of the airplane. The Mustang is pretty streamlined and lends itself to going fast. I haven't had an opportunity to put a radar gun on my TF Mustang with the .91FS and 14x7 prop but I have flown other somewhat fast planes (90MPH-120MPH) to compare against. While the Mustang isn't quite at those speeds, I'd say it does an honest 75-85MPH on straight and level fly by and more in a moderate dive. That's just a guess, it could be more than that. With a higher pitch prop, speed should be even better.

I see a lot of .60 size warbirds with Saito 1.00's and they all perform excellent. I'd say it is a great engine match for that class of airplane. It is reliable, powerful and sounds great.

This is a beginners forum though and I don't want to get too far off track. Scale warbirds should generally wait until the pilot has some experience. I figured that out the hard way a few years back.

Jacked69

Thank you all for your input, I will keep the Golden Knight 100 in her, the plane is balanced perfect with it in there and I would not want to add more weight to balance it, more weight means slower speeds anyway, so its kind of a 2 edged sword IMO. Again thanks for the input everyone.

bruce88123

More weight also means MORE SPEED required on landing to keep the wing flying (not stalled). If you let the CG shift forward you will need more speed to land.

Jacked69

Very good point bruce, did not think of that one....Thank you....