ChiefPilot

ChiefPilot

Well Known Member
So I've got a couple of years and north of 450 hours on my -6A and it's running great. Engine cooling, which I was concerned might be an issue, has not normally been an issue. I have an IO-360-B1B w/dual PMags and a Hartzell prop.

Here's the rub - two minutes at full power, high AoA, moderate (2-4G) and relatively low airspeeds (85 knots or less) will have the CHTs licking 425. I'm looking for ways to provide additional cooling efficiency before doing something drastic like louvers or a cowl flap. I'm not opposed to doing a cowl flap; I'll follow DanH's lead there if it comes to it. I'd just like to explore other areas first.

One thing that comes to mind is the nose gear leg fairing. It seems possible that , at high AoA, it might be partially pressurizing the lower cowl. I'm going to be testing this theory out over the next couple of days with some tufting, a GoPro, and then perhaps something to block potential airflow here.

I'm also going to give the baffles a critical examination, but I think the gains there might be small if only because cooling during takeoff and climb is pretty good. Cruise temps are low 300's in the summer and high 200's in the winter.
 
How are your P-mags set up?

To much advance, even a degree or two can have BIG impact on your CHT's.
 
Drop Brad a line and get his take on setting the P-Mags a degree more retarded. The auto advance will still keep things efficient.

We did that after a kick back issue that damaged a starter and similar high CHT's.

Unfortunately, we changed 3 parameters at once, we re timed with a degree or so back, did a complete re seal of the plenum area and fitted auto plugs to replace the aviation plugs on the lower set, complete with new harness from Brad.

Our CHT's dropped 50f following that and we now hardly ever see CHT's over 400,even after spirited aero's.
 
Assuming your oil temps are fine, any sealing you can do to the baffling would be the first, cheapest low hanging fruit to pick.

If oil temp is also high, your thought on gear leg sealing might also be prudent.
 
mike newall said:
Drop Brad a line and get his take on setting the P-Mags a degree more retarded. The auto advance will still keep things efficient.

We did that after a kick back issue that damaged a starter and similar high CHT's.

Unfortunately, we changed 3 parameters at once, we re timed with a degree or so back, did a complete re seal of the plenum area and fitted auto plugs to replace the aviation plugs on the lower set, complete with new harness from Brad.

Our CHT's dropped 50f following that and we now hardly ever see CHT's over 400,even after spirited aero's.
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Version 40 solves the kickback issue and another problem with lost timing marks. If you don't have this update, send them in.

When they come back, use the EICAD program (available on the Emag Ignitions website) to reduce the timing offset to a -1.4 and reduce the max advance by the same amount.

Once that is done, you don't need the jumper.

Then you should see a reduction in CHT's.
 
Brad, with full power and very low airspeed, you are so far out of the design range it'd seem to be challenging to overcome. You would have to almost double the airflow through the engine to achieve cooling similar to cruise.

Dan H is your expert...
 
As mentioned above, set the less aggressive curve, use a Rite System timing tool to find TDC not the OEM marks and a pointer. Then back off a couple of degrees.

Also make sure the FCU flows a7.5GPH at sea level. Many do not. You may need to get the FCU flowed right on a test bench.
 
AlexPeterson said:
Brad, with full power and very low airspeed, you are so far out of the design range it'd seem to be challenging to overcome. You would have to almost double the airflow through the engine to achieve cooling similar to cruise.
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You're probably right. Frankly, I'd be happy with another minute or two before having to throttle back and go LOP. The RV-4 I fly with rarely has temperature issues before I do and as a result he can just wait me out if he so chooses. Argh.
 
RV10inOz said:
As mentioned above, set the less aggressive curve, use a Rite System timing tool to find TDC not the OEM marks and a pointer. Then back off a couple of degrees.

Also make sure the FCU flows a7.5GPH at sea level. Many do not. You may need to get the FCU flowed right on a test bench.
Click to expand...

How much effect on power will backing off the timing like this have?
 
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