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Surging

D

dekky111

Well Known Member
RV-7A with an O-360 and a constant speed prop. Got grief. Was running rich causing engine to "load up" @ full power--cured by leaning. Sent the carb off for a Service Bulletin rebuild on the floats. Now at full power, the engine surges rhythmically. Not cured by leaning. Fuel flow is 17.4 gph @ full power. CHT's/EGT's all normal. Engine runs smooth @ 23/23 or 24/24, just a full power problem.

Any clues? I'm tired of looking for alternate landing spots with every take-off (good exercise, though).

Jack
24 hours
N811AK
 
First questions:
Which prop governor?
What ignitions?
Happens every single time or does it seem to be more pronounced in certain conditions (hot, cold)?
 
Not gonna say for sure it's NOT the engine, but I'd be looking REAL hard at the prop governor. What model is it?
 
scard said:
What ignitions?
Click to expand...
Does it do this when running the left, right and/or both ignitions?
Easy test and if it is the same on the left, right, and both, it is probably not the ignition.

If it changes, you have just found your problem.

Good luck.
 
Governor

Jack,

If you have the Jihostroj governor - consider that as a potential culprit. Many surge at full power, particularly on cold days. Check the old threads for info on this.

Rob
 
Governor is MT with a Hartzell blended airfoil prop. Does this on mag, elec ign, or both.

E-mailed MT today and got a response. They have a problem with the blended airfoil prop and their model B prop governor. They have agreed to a rebuild upgrade to model F.

I'll let you know if it works

Jack
 
dekky111 said:
Governor is MT with a Hartzell blended airfoil prop. Does this on mag, elec ign, or both.

E-mailed MT today and got a response. They have a problem with the blended airfoil prop and their model B prop governor. They have agreed to a rebuild upgrade to model F.

I'll let you know if it works

Jack
Click to expand...

That will probably do the trick. They have problems with the "B" model in general. I had one that surged too. Had the "F" revisions done, it got a little better, then I bought a PCU5000X and have been very happy ever since.
 
scard said:
That will probably do the trick. They have problems with the "B" model in general. I had one that surged too. Had the "F" revisions done, it got a little better, then I bought a PCU5000X and have been very happy ever since.
Click to expand...
Scott,
I'll hope the F revision works. If not, the PCU5000X will be the choice. Who makes it? Where is it available?

Jack
 
MT Gov

I had the same problem and sent the Gov back to MT. Once it was updated to F mod it 's been fine.
If you do a search you'll find quite a few others have had the same problem.

Peter
 
MT Governor Rework Resolved Issue for me

I see this is an old thread but wanted to say thanks and pile on.
Governor in question is a P-860-4 REV-E with an IO-360, and Hartzell Prop, RV-7.
Experiencing RPM oscillations on takeoff, it would bounce back and forth between ~2530 - 2670 RPM. If you weren't ready for it , it could put you back on the runway after rotation :eek:
The blogs all suggested it was the governor being too old of a REV.

Finally got it out to the MT guys in FL, they were helpful and responsive. I had to pay for the rebuild (had been 7 years) but this rework fixed the issue have a rock steady climb RPM.
Something about the speeder spring (I think) It is now REV-H
Anyway ... thanks
 
Had the same problem with an MT governor and it was long before the Hartzell Composite prop existed.

Switched to a PCU5000 built for me by Aerotech(now Aircraft Propeller Service). Been completely trouble free since.
 
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