mag cooling at the expense of cylinder cooling

[prkaye]

I have two tubes running from holes in each side of the back of my baffles - one to blast cooling air on the mag and the other on the hall effect sensor. This keeps the mag and hall-effect sensor cool, but obviously steals cooling air away from the cylinder fins.
For breaking-in new cylinders, do you think I should cover these holes to maximize cooling air directed through the cylidners? Will the mag be ok running for a few hours without cooling air directed over it?

 

[lr172]

I have two tubes running from holes in each side of the back of my baffles - one to blast cooling air on the mag and the other on the hall effect sensor. This keeps the mag and hall-effect sensor cool, but obviously steals cooling air away from the cylinder fins.
For breaking-in new cylinders, do you think I should cover these holes to maximize cooling air directed through the cylidners? Will the mag be ok running for a few hours without cooling air directed over it?

My mag has been happily making sparks for 950 hours without a cooling blast tube. They are not necessary and reduce cooling efficiency.

 

[drill_and_buck]

Phil,

If you have an electronic ignition, rather than a standard mag, that question should be directed to the EI manufacturer.

Good luck with your project.

-Mike

 

[Dan 57]

Not sure what you are talking about Phil… the mag and hall-effect sensor, maybe a description of your ignition system would help.

In any case, the standard cowl openings are over dimensioned, this to warrant proper cooling on the ground. This in turn means that in flight, and despite those air bypasses, your new cylinders should have an ample supply.

I also notice your ship being flying for quite a while already, and assume the engine was broken in with the same cooling configuration at the time.

 

[Marc Bourget]

Have you checked the "Delta P" between upper and lower cowl spaces?

If you're close to 5.5" H2O, you meet Lyc's specification for any 4 cyl engine and probably don't have to worry about whether you're shorting a cylinder of cooling.

 

[prkaye]

Not sure what you are talking about Phil… the mag and hall-effect sensor,

I have a mag on one side, and a LSE Plasma on the other side. I originally put in cooling blast tubes for each.

I also notice your ship being flying for quite a while already, and assume the engine was broken in with the same cooling configuration at the time.

My old cylinders were those ECI Cerminil ones that broke in very quickly and easily (but were known to commonly have problems later in life). But even after break-in, i've often struggled with CHT's on climb-outs, for the last 12+ years. In the months leading-up to a piston ring failure and extensive IRAN last Dec, i was frequently getting well over 400F in climb-outs even on cool days. I'm just trying to chase down every factor i can to avoid repeating this very expensive experience. Even buying a new mag every year would be a lot less expensive than the engine repair i just went through.

..

 

[Roadjunkie1]

Cooling ducts.......

I have two tubes running from holes in each side of the back of my baffles - one to blast cooling air on the mag and the other on the hall effect sensor. This keeps the mag and hall-effect sensor cool, but obviously steals cooling air away from the cylinder fins.
For breaking-in new cylinders, do you think I should cover these holes to maximize cooling air directed through the cylinders? Will the mag be ok running for a few hours without cooling air directed over it?

I have multiple holes in the back baffles: one for each mag; one for the gascolator; one for the oil cooler; one for the cabin vent. I have never had problems with cylinder cooling. In fact, I have problems keeping the cylinders warm enough. RV-4's are know for being better at cooling than the other RVs. I have the standard cowling openings. There are holes in the in ramps as well: two for the alternator. Overkill? Never had heating problems, vapor lock, alternator problems. Seemed like a good idea at the time and seems to be working well. RV-9's may be another issue as far as cooling.....

I think the small amount of air "robbed" from the cylinders is not going to make that much difference. I worked very hard at making sure my baffling seals were tight against the cowling everywhere. No leaks. IMHO....

Hall effect sensor.....

 

[prkaye]

Hall effect sensor??....

Sorry, "Hall Effect Module". This is what Lightspeed calls the module they put on the accessory case that is part of their Plasma electronic ignition systems. Although they may not use that system anymore, it was part of the system when i bought it about 14 years ago. It's a cylindrical thing with a serial port and a green LED on the back that has a gear and plugs into you accessory port where a mag would normally be mounted. It somehow senses the crank position to time the ignition firing. Based on the name, i'm assuming it senses something called a "hall effect"? i never bothered to look up what that is.

 

[Roadjunkie1]

Hall effect sensor....

Sorry, "Hall Effect Module". This is what Lightspeed calls the module they put on the accessory case that is part of their Plasma electronic ignition systems. Although they may not use that system anymore, it was part of the system when i bought it about 14 years ago. It's a cylindrical thing with a serial port and a green LED on the back that has a gear and plugs into you accessory port where a mag would normally be mounted. It somehow senses the crank position to time the ignition firing. Based on the name, i'm assuming it senses something called a "hall effect"? i never bothered to look up what that is.

A Hall effect sensor (or Hall sensor) is a type of sensor which detects the presence and magnitude of a magnetic field. The output voltage of a Hall sensor is directly proportional to the strength of the field. Hall sensors are used for proximity sensing, positioning, speed detection, and current sensing applications. Probably has to do with the position of the drive for the Lightspeed system for ignition timing....maybe.....

 

[Dan 57]

Thanks for the details Phil.
There are thousands of aircraft flying around with no mag cooling blast. Also not aware of the requirement for the sensor.
So if you are the least worried, plug these openings with some HST or the like, break them cylinders in, and then remove the HST. But it shouldn’t be necessary.

Getting regularly 400+ temps sounds high, the more so under your latitude, once the engine’s broken in. Not sure how precise your T indication is, also, if not already done so, climbing with reduced power, at flatter angle (flying solo for me is 23/23 climb at minimum 100KIAS) and a rich (somewhat leaned for altitude OPS) mixture.

 

[chaskuss]

I have a mag on one side, and a LSE Plasma on the other side. I originally put in cooling blast tubes for each.

My old cylinders were those ECI Cerminil ones that broke in very quickly and easily (but were known to commonly have problems later in life). But even after break-in, i've often struggled with CHT's on climb-outs, for the last 12+ years. In the months leading-up to a piston ring failure and extensive IRAN last Dec, i was frequently getting well over 400F in climb-outs even on cool days. I'm just trying to chase down every factor i can to avoid repeating this very expensive experience. Even buying a new mag every year would be a lot less expensive than the engine repair i just went through.

..

Phil, do all your cylinders run hot during climb out? If not, which ones run hot? Good advice from Marc Bourgot to check pressure differential.

 

[claycookiemonster]

How would I prepare to do such a thing?

I'm finishing up the engine install and beginning wiring. When I hear someone suggest that I check the pressure differential in the cowl, part of me thinks that's obvious, and another part of me things that's very exotic. Someday, once flying, I may have to do this. My question now, is how would I prepare now to do that later? Or any number of the exotic/obvious checks that may be suggested here?
Did you guys run new sensor wires up front to evaluate this? Did you run pressure tubes, like static ports up front to test this? Should I be laying in an extra set of sensor wires above and below the baffle and just letting them lie there until the day comes when I want to run such a test? And, supposing I am able to install the sensors, what device are you using to read the delta P? Or the delta Temp? Or the cowl exhaust versus air intake measurements? Whatever the test de jour is?

 

[lr172]

A Hall effect sensor (or Hall sensor) is a type of sensor which detects the presence and magnitude of a magnetic field. The output voltage of a Hall sensor is directly proportional to the strength of the field. Hall sensors are used for proximity sensing, positioning, speed detection, and current sensing applications. Probably has to do with the position of the drive for the Lightspeed system for ignition timing....maybe.....

It is used by the EI to know when the engine is at TDC and the speed at which it is spinning. Multiple magnets are used and one is left out of the symmetric layout/pattern. From this it can know exactly where the crank is at any point in it's rotation and therefore precisely control spark events relative to crank position. A HE sensor is usually good to pretty high temps and needs no cooling. However, the LED light implies some chips and other electronic goodies that may not deal with the heat so well. I did not provide a recommend on the HE module as I have no experience with it or its environmental limitations. The mag definately does not need a blast tube. Nothing in there that can't handle under cowl temps. I have a home made HE module on my 6 and it needs no cooling. However, it is just the HE sensor with no other electronics. MFR rated it for 125C.