Lower idle speed (Full Version)

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MetallicaJunkie -> Lower idle speed (5/7/2008 3:15:00 AM)

i have a saito 150 what prop would giv me a lower idling speed, i remember the last time i used this engine i had hard time achieving a low reliable idle speed.... which prop size would get me closer 16x8 zinger pro or a 15x 10 apc

id like to confirm what i was told at the field with RCU as i trust my fellow modelers here as well



w8ye -> RE: Lower idle speed (5/7/2008 4:59:23 AM)

A 16 X 8 APC will give you the lowest idle.

Next best would be the 15 X 10 APC.

Wood props are lighter than composite props and do not idle as well



MetallicaJunkie -> RE: Lower idle speed (5/7/2008 6:16:44 AM)

ok i dug deep and found a 16x12 apc pattern prop would that be too much for a saito 150, its on an old lanier edge 73" wind span



FlyingPilgrim -> RE: Lower idle speed (5/7/2008 7:11:04 AM)

16x12 would be too much, get a 16x8. Like Jim said, the APC is heavier, so it will give more flywheel effect, allowing a lower idle speed.



rexracer -> RE: Lower idle speed (5/7/2008 1:46:11 PM)

I'm curious as to how low an idle you want. With the low speed set correctly, that engine should easily idle around 2000 rpm. I have a Cline regulator on my 180 and it definitely helped in the idle department. I've had it idling as low as 1350 rpm with no glow heat. I wouldn't trust it that low, though. It will idle all day at 1800 rpm with the MA Classic 18x6.



MetallicaJunkie -> RE: Lower idle speed (5/7/2008 2:17:48 PM)

i dont have a tach yet, but i want it as low as possible yet reliable.... the reason im concerned about this is because last time i used the 150 the lowest reliable idle was too high, i had to really force the plane down, also someone had to keep hold if it on the ground on the lowest idle it would want to roll fast.... thankfully i joined a a club a couple of months ago that has some 4 stroke buffs im sure its just a matter of adjusting it correctly....

this is what it was doing last time i used it.... i would get the idle to about where wanted it, then the engine would start popping and it was really shaking the fuse

thanks



rexracer -> RE: Lower idle speed (5/7/2008 3:36:57 PM)

Yeah, sounds like you need to get it adjusted right. If your buddys can't get it to work, there are people here that can help.



Ed Cregger -> RE: Lower idle speed (5/7/2008 3:53:07 PM)

Real high pitch pattern props are going to pull your model around on the ground at idle. They will also make it difficult to land your model with the engine running. Friends of mine used to have to kill their pattern ship's engine on approach, in order to get the model down on our small field with any predictability, due to the huge pitch they were running in their props.


Ed Cregger



blw -> RE: Lower idle speed (5/7/2008 5:11:31 PM)

The low speed needle valve is set too rich.



MetallicaJunkie -> RE: Lower idle speed (5/7/2008 9:38:24 PM)


quote:

ORIGINAL: blw

The low speed needle valve is set too rich.


I have a feeling it is..... i have it set flush like the directions say.. ill give it a try tonight when i get home



Nathan King -> RE: Lower idle speed (5/7/2008 10:31:04 PM)

quote:

ORIGINAL: MetallicaJunkie


quote:

ORIGINAL: blw

The low speed needle valve is set too rich.


I have a feeling it is..... i have it set flush like the directions say.. ill give it a try tonight when i get home


In my experience, a flush needle head on a Saito is quite rich. Just take some time and tune the thing up. I'd bet you'll have it easily idling at 2000 in no time at all.



MetallicaJunkie -> RE: Lower idle speed (5/8/2008 1:42:30 AM)

thanks for the suggestions guys, leaning out the low end was the trick.... i dont know how close it is to 2000 , im happy now



Campgems -> RE: Lower idle speed (5/8/2008 3:31:01 AM)


quote:

ORIGINAL: MetallicaJunkie


quote:

ORIGINAL: blw

The low speed needle valve is set too rich.


I have a feeling it is..... i have it set flush like the directions say.. ill give it a try tonight when i get home


There is more than just low idle speed to consider. You want the enging to pull at its maximum performance, idle at a reasonably slow speed and make the transistion betwee the extreemes without stumbling or quiting.

Adjust the high end for maximum RPM less about 400 rpm to the rich side depending on the conditioning of the engine. Fully broken in you can get away with 300 rpm rich but with a new engine, I would go around 600 rpms rich.

Then you adjsut the idle . Set the throttle as slow as the engine will run without stalling and then at this throttle setting lean the idle to achieve maximum RPM.

Go back and adjsut the high end again.

Go back and adjust the idle again. This thime the idle should be much slower.

The work on the transistion.

Run the engine up after it is warmed up and hold it at full throttel for a few seconds to clear out any loading. Go to full idle and let it run there for a count of 20 to 30, the punch it full throttle. It should jump to the throttle. If it dies as soon as you punch it, the idle is set to lean, open it up 1/16 turn at a time until it jumps to life. If it stumbles and snort before increasing RPM, it is to rich and again adjust, this time to the lean side, 1/16 turn at a time until it jumps.

Go back over the whole sequence one more time and then don't screw with the jets unless there is a big change in temp, humidity, or a new fuel mix.

You just have to have a tach to do this. Once you have adjusted an individual engine a number of times, you will be able to hear that engines and determine what needs to be done. Untill you get to know the engine though a tach is necessary. As soon as a tweek at the field doesn't work like you thought it should, start from step one, otherwise you are going to meander further and further from the proper setup.

The previous suggestion of a 2000 rpm idle is a good target. A couple of our guys with big birds use an air brake setup to slow down the plane after landing. You might look into setting up someting like this on your transmitter after you get the idle taimed.

Don



MetallicaJunkie -> RE: Lower idle speed (5/9/2008 5:22:09 AM)

thanks for te indepth reply, i went flying today the idle was great but i couldnt get the engine to run great on the high end, im going to"reset" the engine to factory settings and print your post and tweak it here at home befor i go out tot he field again on saturday.... another reason i suspect the the high end lacked wass because i was trying to get rid of a batch fai and some 10% i mixed together..... ill use some fresh 15% next time



Cyclic Hardover -> RE: Lower idle speed (5/9/2008 3:13:06 PM)


quote:

ORIGINAL: MetallicaJunkie

i dont have a tach yet, but i want it as low as possible yet reliable.... the reason im concerned about this is because last time i used the 150 the lowest reliable idle was too high, i had to really force the plane down, also someone had to keep hold if it on the ground on the lowest idle it would want to roll fast.... thankfully i joined a a club a couple of months ago that has some 4 stroke buffs im sure its just a matter of adjusting it correctly....

this is what it was doing last time i used it.... i would get the idle to about where wanted it, then the engine would start popping and it was really shaking the fuse

thanks


I can relate to this now. I have a 40 size P-51 withga Saito 100. Trying to prop it right for speed but at the same time, it was to roll around pretty fast even when its nearly shut off.



Nathan King -> RE: Lower idle speed (5/9/2008 4:57:50 PM)

quote:

ORIGINAL: Cyclic Hardover


quote:

ORIGINAL: MetallicaJunkie

i dont have a tach yet, but i want it as low as possible yet reliable.... the reason im concerned about this is because last time i used the 150 the lowest reliable idle was too high, i had to really force the plane down, also someone had to keep hold if it on the ground on the lowest idle it would want to roll fast.... thankfully i joined a a club a couple of months ago that has some 4 stroke buffs im sure its just a matter of adjusting it correctly....

this is what it was doing last time i used it.... i would get the idle to about where wanted it, then the engine would start popping and it was really shaking the fuse

thanks


I can relate to this now. I have a 40 size P-51 withga Saito 100. Trying to prop it right for speed but at the same time, it was to roll around pretty fast even when its nearly shut off.


If your prop pitch is really high (which is probably is since you're propping for speed) your airplane may never slow down as well as you want even with a low idle. Case in point: one of my old pattern (60 sized) airplanes. I'm running a tuned pipe in the thing with a 12x12 prop, it has retracts, and the airframe is really 'slippery.' Needless to say it just won't slow down quickly even with a nice 1900RPM idle. Like me, you've got a lot of engine in a relatively small airframe with a prop pulling lots of air per revolution. Set up your approach as you begin the upwind leg (yes, I said upwind, not downwind). Once I decide I want to land I drop the gear ASAP to add drag. Stay fairly low with not much throttle and turn downwind. I personally have to cut the engine the second I'm level at downwind. I let it glide and make a nice gentle (NOT steeply banked) turn for final. At this time I am making a nice shallow approach still on idle. Occasionally I may have to blip the throttle just a bit (sometimes not). When I reach the threshold I really let her get into a nose high attitude to create as much induced drag as possible. By the time I flare, I've just run out of elevator (VERY high AOA) and the airplane still isn't exactly coming in at a snails pace but will sit down very well.

If you're confident in your piloting skills you could cut off the engine during final. I've done this, but personally don't like the extra risk involved.



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