Keep in mind that Tracy has tuned intake and exhaust.
How far away from the exhaust ports do you join the headers into one?
I've been told that you can gain as much as 20 HP with the tuned exhaust.

On the intake, it doesn't have to wrap over the engine. It could stay on the intake side. From the ports all the way out to the cowl cheek and back. Or you could make a "snail" as PL suggested - basically bending the tubes into a circle. In the last case it will probably be better to have butterfly valves near the ports. I'm thinking a 3/8" to 1/2" thick manifold flange should be thick enough to hold 4 or 6 butterfly valves and their shafts.

I now have a new excuse for holding off on changing to tuned intake and EFI: waiting to see what Tracy comes up with next.

Finn

Russell Duffy wrote:

Greetings,

I bolted on Tracy’s prop today, and ran the engine some.  This was partly to make sure I can top off the coolant tomorrow, and partly (mostly) to see what I get for static rpm.  Tracy stated that he typically got between 5100 and 5200 rpm static, and as expected, I’m below that.  My best mixture rpm was 4800, with the more typical mixture of 47XX.   I could always hope that my intake is just going to be more efficient at higher rpms, but what are the chances :-) 

Unfortunately, the intake continues to exhibit signs of transition problems, so it’s only a matter of time until it goes away.  To get any sort of decent throttle acceleration, the mixture has to be on the rich side, about 3:00, otherwise you can watch the mixture fall off to nothing, and the engine sags.   Deceleration needs to be just the opposite, around 9:00.  I’m now convinced of two things- I would be better off with smaller injectors (38 lb/min on order to replace the current 50 lb/min), and I MUST get the injectors back closer to the block.

I have a short, straight intake, that can be modified to work, and I could also use tubing to make my own short intake from scratch.  Hard as I try, I just can't see a way to make a "proper" EDDIE intake fit the the confines of my RV-3 cowl.  Since I will want my best tuned rpm to be around 7000, the short version of manifold may work better than it has for others.  I just haven't made a decision on what to try next though.  I'll probably feel compelled to try a short intake, and see if it's better or worse than what I have now.  At least I can collect some benchmark numbers for comparison. 

If anyone has any brilliant ideas, I'd like to hear them.

Cheers,

Rusty (flying with wood tomorrow)