Low manifold pressure on takeoff?

[Gash]

I just did a takeoff where the engine only made about 15 inches MAP at full throttle, mixture full rich, 950 ft pressure altitude. The engine sounded the same, felt like it was making full power, and takeoff distance was normal. Fuel flow on takeoff was redlined, as expected.

The MAP slowly crept up to 20 inches while flying close to the airport at 3,000 MSL, full throttle. It never went above 20 inches though.

I tried unsuccessfully to Google this, search John Deakin's old articles, reading through my "Fly the Engine" book, etc. and am not finding anything. It seems the main discussion in other threads and articles is instead on high MAP. Does anyone have an idea what might be causing my low MAP on takeoff? I think I've ruled out a bad MAP sensor as I'm getting normal indications on the ground with the engine stopped.

[vic syracuse]

Have you ever cleaned the line between the sensor and the cylinder? They can get clogged over time. I clean mine out every year.

Vic

[lr172]

Originally Posted by vic syracuse

Have you ever cleaned the line between the sensor and the cylinder? They can get clogged over time. I clean mine out every year.

Vic

+1
You would notice a difference in power and fuel flow if your were actually pulling that much vacuum compared to WOT and 29"

Larry

[Gash]

Originally Posted by vic syracuse

Have you ever cleaned the line between the sensor and the cylinder? They can get clogged over time. I clean mine out every year.

Vic

Thanks Vic. I'll go take a look at it. What do you use to clean out the line? I would probably use 100LL unless there's a more elegant solution.

[vic syracuse]

I use Brake Clean or any other solvent.

Vic

[dtw_rv6]

I just went through this myself, and the guys above are correct. My MP gauge eventually stopped altogether. Pull the fitting at your engine connection first. Mine was packed with black gunk that was as hard as concrete. I used 0.035 safety wire and a good soak in MEK. An ultrasonic cleaner might accelerate this process.

[BillL]

Your symptoms indicate black goo in the hose/line. 100LL works just fine.

[Gash]

Thanks everyone! I really appreciate it.