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BRS wrote:When I did the cold air intake on the R2300 using a Rotec MKII carb, Rotec cautioned about elbos near the carb. There were none but but I did go ahead and make a flow straightener to dampen any intake air swirl. Perhaps something like this might be helpful.

So here is my shot at it. I figure my fresh air is blasting the side of the air filter and making the flow inside hokey.


It just slides in, a tight fit.


Unfortunately when I took the first picture I hid the bottom of it. I've got a half circle cut in the bottom of the vanes, so the air at the back of the filter can mix. I'll get another picture later.

Here is the bottom of my flow straightener.

You need to get a good reading on the CHT. That's all the matters, really. If the CHT is in line with the others, and within the proper range, then there is likely nothing wrong with the cylinder, so it would be a sensor or display issue with the EGT.

mike.smith wrote:You need to get a good reading on the CHT. That's all the matters, really. If the CHT is in line with the others, and within the proper range, then there is likely nothing wrong with the cylinder, so it would be a sensor or display issue with the EGT.

My CHTs have never been matched, or particularly hot. But in troubleshooting the sensor this is what I've done:
1) swapped the left front and left rear EGT probes. High EGT stayed with the cylinder.
2) swapped the two inputs into the MFD. High EGT stayed with the cylinder.

If I remove my fresh air induction, the problem goes away. When I put the fresh air induction back, the problem comes back. I'd like to find a way to keep it as I am gaining about 150 RPM in climb.

From my borescope inspection, the hot (#1) cylinder definitely looks different on the exhaust valve than the others.

I read through this and I have a few thoughts/considerations:

1. I believe your previous intake was a filter mounted directly on the aerocarb. This would have pulled from the hot "low pressure" area in the belly of the cowl. Your intake would only reduce air pressure and promote the flow of cooling air through the cylinders. With the cold air setup you are no longer pulling intake air from this area, increasing static pressure here, and reducing cooling flow. If you can open the outlet on bottom easily you could test this theory to see if there is improvement. If you have to cut the cowl there's really no easy way to test that I am aware of.

2. I understand the idea of the elbow at the intake causing uneven distribution of flow through the aerocarb; however, i do not believe it would not have went away during subsequent tests with the elbow and no cold air supply. Let us know if the flow vanes help any, I'm very curious about this one.

3. You said you reshimmed your engine. Is it possible you inadvertently created a gap in the cooling baffle seals that is allowing a bypass of cooling air between the seal and the cowl.

Good luck!

WaiexB22 wrote:I read through this and I have a few thoughts/considerations:

Good luck!

Robert,
1) I've had two air filter configurations. One directly attached and one with the elbow. The only reason I swapped was because I didn't have the K&N RC-1980 safetied. It fell off and melted on the exhaust. It is no longer available. No real difference between the two with respect to temperatures, etc. Yes it was pulling hot air from the low pressure side of the cowl for either filter. So far I have not seen any CHT or oil temperature issues with the addition of fresh air induction. Summer is coming though.

2) I don't think the elbow is the cause. I think it is the blast from the fresh air right on the surface of the filter causing turbulence inside the filter. This is my current theory.

3) The baffles still fit nicely. I was a nutjob about sealing for cooling reasons.

I believe the high EGT, and the unbalanced EGTs are purely related to uneven air-fuel mixture. Pretty common in AeroVees not counting the turbo models. So it's not a cooling issue, but a fuel distribution issue.

Still I agree this will reduce cooling air flow which will make our marginal hot weather cooling worse. I have a set of B model side inlets that I'm going to add. But that is another experiment.

It sounds like you're on the right path. I didn't think the elbow would matter much.

I wish I could have made the side outlets work on my setup, but it would have taken A LOT more work and different radiator(s) that were hard to source, so I do not indent to use them at this time. I think they look really nice.

My super simple deflectors. Not much surface area is blocked due to filter radius, pleats, and a slight bend front & rear. The rivet tails in the pleats help keep alignment.

A view of my flow straightener via inspection mirror. Test flight after work today.


I originally used pops for the flow straightener. Got to thinking it would be bad if a mandrel went through the engine. I drilled out the pops and installed solid rivets.

I have seen what a bolt will do to the inside of a cylinder and you definitely don't want a rivet in there.

Let us know if it works.