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Pponk 0-470-50 static RPM

pa11driver

MEMBER
1975 180J with a Lycon built ported and polished pponk 0-470-50 with 7.5:1 pistons and 3 blade 86” Mac 401. What static rpm should I be seeing? I see about 2550. Accelerates to 2700 in the climb after breaking ground. Seat of the pants doesn’t feel very powerful. About like the stock motor 180’s I’ve flown. It’s been this way as long as I’ve owned it. It has good compression, zero valve leakage. Governor tests fine and the prop blades are set at 9 degrees on the flat stop. Runs 24gph and about 2.5” of MAP less than ambient at wot.
 
What does the STC for the engine and prop say??? A constant speed prop should hold max RPM until you pull it back What is the MAX RPM FOR THE STC?????
DENNY
 
What air filter is installed? -2.5" might be improved with a Donaldson element. If using a Brackett temporarily remove the foam element and test for more MP?

Gary
 
What is the certified maximum rpm (red line) for that engine? The type certificate for unmodified 0-470s says either 2550 or 2600 rpm.
Unless Pponk raised that limit, your engine is turning the correct rpm. The error is your governor is set wrong by allowing the engine to turn higher than that number after take off.
 
My pponk max is 2700. As others have said, if you are not able to get full rpm something may be awry with you governor/ prop setup..

sj
 
Max rpm on a pponk is 2700. Just curious what folks with that particular prop and engine are able to static. North point says it should static 2700. Measured the flat pitch of the prop and changed the governor already.
 
Prop fine pitch stop set too coarse..?

Check STC or TCDS for degrees, then prop overhaul paperwork. This should rule in or rule out..
 
If you suspect low power, check your muffler flame comes to be sure they haven’t collapsed.
 
If you suspect low power, check your muffler flame comes to be sure they haven’t collapsed.

805f98a5f2dddb02d15b29b1a3cca068.jpg


A new muffler from acorn welding doesn’t have the baffle in it


Sent from my iPhone using Tapatalk
 
Max rpm on a pponk is 2700. Just curious what folks with that particular prop and engine are able to static. North point says it should static 2700. Measured the flat pitch of the prop and changed the governor already.

If the STC holder puts max rpm at 2700 on an engine with a constant speed prop, it should turn 2700 at full power.

BUT, is your tachometer accurate? Have you verified tach accuracy with a digital tach checker? If not, do that first.

MTV
 
Max rpm on a pponk is 2700. Just curious what folks with that particular prop and engine are able to static. North point says it should static 2700. Measured the flat pitch of the prop and changed the governor already.

Just to clarify, my pponk with Mac 401 statics at 2700 (or a little more..)

sj
 
Great, thanks. Any idea what manifold pressure you have at WOT? (Relative to ambient pressure and altitude)
I'll have to check next time I'm out. Never noticed mp.

sj

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If your altimeter pressure window is accurate, in flight reset the altimeter to "0" feet. Read the approximate air pressure at that altitude if still in range, then reset to previous reading. The MP WOT should approach that value. How close depends on how tight the engine is internally (induction and cylinder) plus volumetric efficiency among several factors.

Edit: https://pilotinstitute.com/what-is-manifold-pressure/ Offers some insight about the values and trends as the engine wears. Keep notes in your logbook to review during periodic maintenance.

Gary
 
Thanks, I’m curious what people with 180’s see for that gap between ambient pressure corrected for altitude. Like I mentioned, I’m currently a bit lower than I’d expect. About 2.5”
 
As an addendum to my previous post, the FAA apparently considers a mechanical tach that reads within 100 rpm of actual to be "airworthy". That's not acceptable to me, which is why I have an electronic tach, which was also verified with a digital tach checker. A faulty tach could easily make that much error.

MTV
 
Thanks, I’m curious what people with 180’s see for that gap between ambient pressure corrected for altitude. Like I mentioned, I’m currently a bit lower than I’d expect. About 2.5”

A check pilot once mentioned ~-2" MP from ambient was good in the C-185. Clean air filter and tight efficient engine, etc. Then discovering why was almost impossible, so I took his word and flew on. Later with fresh overhauls I kept track of that for several engines - fixed pitch and CS. Seems about right with some variance between engines and gauges.

An opinion. 1-2" drop is mentioned as well: https://www.pilotsofamerica.com/com...ent-pressure-and-map-at-full-throttle.143502/

Gary
 
~2” drop is typical. O-470-50 180J I fly turns 2700 static- hits that before WOT. At first blush, sounds like you have an issue.
 
What aptitude are you at. Fine pitch stop is set for sea level to not over rev. At our altitude we are always 100 rpm shy.

Some Guys slightly massage the stop to get full RPM on take off especially on floats.

Caution! If the governor fails you need enough thrust to maintain flight at full fine and bellow redline to find a save place to land. That is why the fine pitch stop is there.

If you blow the motor after the governor fails you have a bad Day.

Everything you mess with effects something else.

So if you mess with stuff better know what you are doing.

Aircraft intakes are awful at best with continental and the O470 being about as bad as it gets 2.5 below ambient is good for them.

No porting in the world can make the air flow better through that carb and the y splitter in the system, often you can get more gain from cleaning up flow through the intake than from porting.

Depends on what engine, one without the other does not help much.

Whatever goes in the intake has to go all the way through carb intake valves and out the exhaust. All components need to be able to flow at the same rate to make more power.

That got longer than expected cheers......
 
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