Hi All,
Is the " pinch test " applicable for High end needle settings or Low end needle setting ? I am a bit confused, as in some article its explained in the High end needle setting section while some in Low end settings.
I have both Car and Aircraft engines...

Pls clearify...

Regards,

Justin.

Just low end for me on my 2 cycle stuff. I "think" I can still hear well enough to set the Hi End with a tach and my ears.

Pinch test can be used for either/both needle setting as covered in considerable detail in the tuning sticky at the top of forum https://www.rcgroups.com/forums/showthread.php?t=205602

Steve

It's more suitable for the low end because of the time it takes to get a reaction. At full throttle the engine is using fuel so fast it can be difficult to hear any difference before it starts to die from lack of fuel if it's even close to being tuned correctly.

Perhaps I just have good ears then . I've always used the pinch test as the last check on the top end before flying, just to be confident that nothing's changed and I'm still running a little rich.

OTOH I'm not much of a needle twiddler and tend to just leave my engines alone once I have them running well.

Steve

I use the pinchtest for the LSN.

HSN test is done by holding the plane vertical with it's nose straight up at WOT.

Pinch test is good for both high and low ends. It reacts faster for high end but the principles are the same. As others have said, the Tach is best for high end stuff especially four stroke engines. The thread at the top of this topic is well worth reading and using.

Cheers,

Chip

What's the thinking when holding the plane vertical for the high end mix? What do you listen for?
Thanks KMR

Originally Posted by Connexxion

I use the pinchtest for the LSN.

HSN test is done by holding the plane vertical with it's nose straight up at WOT.

Connexxion,

But you are not explaining how you can tell if it is properly set.
In fact I think someone else is asking.

I do not wanr to finish your post for you. That would be impolite on my behalf.

Zor

Originally Posted by Zor

Connexxion,

But you are not explaining how you can tell if it is properly set.
In fact I think someone else is asking.

I do not wanr to finish your post for you. That would be impolite on my behalf.

Zor

LOL, I'll do it...

...holding the plane vertically at WOT, if you pinch the fuel line, the rpms should -increase-. If they drop off, the HSN is too lean. Open the needle a couple clicks and repeat.

I get really paranoid when I have to hold the plane nose up wot. I just do it on the table then go for a fly. If its too lean I just quickly land the plane and richen it up 1/8th turn and test on the table then refly/test. If it is too lean while flying all you have to do is cut the throttle and land. While idleing comming around setting up for landing...the plane is useing the slow idle setting and wont damage the engine. Then again I tend to run just a tiny rich all the time just to be safe. I like to see a smoke trail when I fly.

Jay

Originally Posted by skybanker

I get really paranoid when I have to hold the plane nose up wot. I just do it on the table then go for a fly. If its too lean I just quickly land the plane and richen it up 1/8th turn and test on the table then refly/test. If it is too lean while flying all you have to do is cut the throttle and land. While idleing comming around setting up for landing...the plane is useing the slow idle setting and wont damage the engine. Then again I tend to run just a tiny rich all the time just to be safe. I like to see a smoke trail when I fly.

Jay

Hi skybanker,

A little imaginary situation here _ _ _
I am with you at the field and you made all your adjustments or touch up on the table and you declare ready for a flight.

There you go with a beautiful take off and the airplane is climbing nicely, left climbing turn, leveling downwind about 200 feet and you tell me "that engine is running lean, I better land and make it a little richer".

I then ask you "what make you say it is too lean ?"

What do you answer me ?

Zor

Originally Posted by Hemikiller

LOL, I'll do it...

...holding the plane vertically at WOT, if you pinch the fuel line, the rpms should -increase-. If they drop off, the HSN is too lean. Open the needle a couple clicks and repeat.

"Pinching" the fuel line with the engine WOT while holding the plane vertical is not a very good idea. In fact its a good way to lose a few fingers or a hand when it suddenly slows down.

It goes like this: tune the high end to peak rpm on the ground with the plane sitting horizontal. You find the peak rpm by turning the needle in too far so that the rpms start to fall off----which means you found the lean point. Now back the needle out about 3/4 turn from the point of being lean and then hold the airplane vertically and see if the rpms increase. And don't just hold it there vertically, do it like recycling a condom and shake the f--k out of it while it is vertical. Once you get "the ear" for a properly tuned engine you'll find its no big deal to do.

Rube

Originally Posted by Rube Goldberg

"Pinching" the fuel line with the engine WOT while holding the plane vertical is not a very good idea. In fact its a good way to lose a few fingers or a hand when it suddenly slows down.

It goes like this: tune the high end to peak rpm on the ground with the plane sitting horizontal. You find the peak rpm by turning the needle in too far so that the rpms start to fall off----which means you found the lean point. Now back the needle out about 3/4 turn from the point of being lean and then hold the airplane vertically and see if the rpms increase. And don't just hold it there vertically, do it like recycling a condom and shake the f--k out of it while it is vertical. Once you get "the ear" for a properly tuned engine you'll find its no big deal to do.

Rube

Don't want to be anywhere around during the last bit.

Originally Posted by Rube Goldberg

"Pinching" the fuel line with the engine WOT while holding the plane vertical is not a very good idea. In fact its a good way to lose a few fingers or a hand when it suddenly slows down.

I don't think it's any more dangerous than twiddling a needle with the motor at WOT sitting on the ground. If the plane is too unwieldy, have a helper hold the it up for you. I've been doing this for 20+ years and never even brushed up against the prop. Most of my stuff is 40 size, so it's no chore to hold it by myself.