PDA

View Full Version : Low manifold pressure indication



Dave Saylor
02-18-2011, 10:25 PM
On my IO-540 the manifold pressure has never read over about 28 inches, except when the engine is off. Then it reads ambient pressure.

Most other planes I've seen read closer to ambient pressure at full throttle.

It's been this way since the engine was new. The engine seems to make good power based on fuel flow, temps, and performance, so I don't think it's a weak engine. RPM is fine.

Idle is fine so I don't suspect a manifold leak, but maybe I'm missing something there.

I take MP off the aft right cylinder primer port, which I think is the standard location.

All I can think of is some kind of blockage but there's just not that much to go wrong between the filter and the primer port. I've checked everything I can think of.

Any ideas?

Rob Hickman
02-21-2011, 07:40 PM
If it reads correct on the ground the sensor is reading correct, I suspect that Van's filter and intake is the real problem.

What were the other planes? and how were you measuring them?

I only get around 28 at 2700 RPM in my RV-10.

I get 29.1 in my RV-4, same size filter 4/6 of the airflow.

brianjohnson
03-02-2013, 04:54 PM
Mine reads well below ambient pressure on the ground. It read correctly on my old D-10, but I haven't checked it in the air yet with the AFS.

brianjohnson
03-03-2013, 11:09 AM
Seems to read low at anything other than very low RPM. I noticed that the top calibration point is way out of sync with the displayed sensor value when it should be fairly close, but I'm not sure the bottom calibration point is correct either, so what is the correct method to calibrate it? The manual says it shouldn't require calibration.

brianjohnson
03-03-2013, 11:10 AM
btw - when I say low, I mean VERY low, not just a little bit off.

Rob Hickman
03-03-2013, 07:18 PM
I suspect that you have the high pressure turbo manifold sensor. I will get the numbers for you in the morning.

brianjohnson
03-04-2013, 05:41 AM
The D10 was set to sensor type 1, which is listed as Dynon P/N 100434-000. The only other setting besides the green/yellow/red ranges was position, which was set to left.

brianjohnson
03-04-2013, 06:14 AM
I did a little more research and that part number is Ballenger SNSR-03066 / Delphi 12247571

Rob Hickman
03-04-2013, 09:57 AM
Change the sensor type in calibration to 41201 Turbo and try it.

brianjohnson
03-23-2013, 06:34 AM
Got caught up in some other things, but it's still not reading correctly on the ground or in the air. It's closer, but still off by quite a bit

Rob Hickman
03-23-2013, 09:42 AM
If you set the EFIS Altimeter to zero feet the Baro on the EFIS should match the Manifold pressure.

We have three different manifold sensors that can be selected. Since you are not using our sensor will have to guess what you actually have.

1. Select P/N: 41201 Turbo and press SAVE.
2. Return to the EFIS main run mode and set the Altimeter to zero feet.
3. Read the BARO value on the EFIS screen at zero feet.
4. Return to the Manifold Calibration menu.
5. Use the Shift Adjust setting to make the Manifold read the EFIS Baro value at zero feet.
6. Press Save

brianjohnson
06-03-2013, 05:35 AM
I think the problem might be the lasar ignition system. It tees off the manifold pressure line to it's own sensor, which I'm guessing would cause both sensors to read about half of what they would normally read?

Rob Hickman
06-03-2013, 08:10 AM
Only if you have a leak.

brianjohnson
06-09-2013, 04:45 PM
it turns out that it was only slightly off the standard turbo settings. It was easy to check today because the barometric pressure was almost exactly 30.0 and the value was only off by about 50. What does the value correspond to anyway? I found a chart with millivolt readings for all the pressure settings for the sensor I have, but the values were way off compared to the sensor readings displayed on the EFIS.

Rob Hickman
06-10-2013, 11:06 AM
it turns out that it was only slightly off the standard turbo settings. It was easy to check today because the barometric pressure was almost exactly 30.0 and the value was only off by about 50. What does the value correspond to anyway? I found a chart with millivolt readings for all the pressure settings for the sensor I have, but the values were way off compared to the sensor readings displayed on the EFIS.

Call me from the plane.. (503) 263-0037 ext 202