| Joe,
It was the original design of PL, expanded for the 3-rotor. It used a solid 3/8" teflon slider. When I initially built it I didn't allow for expansion of the teflon slider and so the hotter things got the tighter the slider was in the cavity. He now recommends thin sheets of teflon bonded to an aluminum slider. I didn't try that, so I don't know if it corrected the problem. I modified my slide throttle by opening the tolerances up until it would work when hot.
But then it also leaked. Like I said earlier, the fuel would puddle before the slide. If there wasn't a perfect seal between the plates and spacer, you'll get leaks onto the exhaust. Not a good situation. This could have been part of the problem I was experiencing with rough idle.
Also, the slide throttle does not allow for balancing the individual rotors. So, precision is the word when drilling. My pieces were built using a Bridgeport, but then I had to weld the short tubes to the outer plates. I may have gotten things a little "off" when cleaning up the welds. But I could feel one rotor cutting out during ground ops. I tried fine-tuning it with a small fine file, but was never happy with the results.
And it didn't allow for a truly positive method of retaining the throttle cable. The design as shown did not provide for a lock nut or setscrew to keep the throttle cable from backing out. Mine never did, but the thought was always in the back of my mind. It was also very difficult to screw the throttle shaft into and out of the assembly for installation and removal of the slide throttle. I feel that part of the design could use a bit more engineering to address this issue.
Those are some of the issues that I've identified. I'm sure that most could be overcome, but I ran across these sweet little one-barrel throttle bodies for approx. $100 on ebay. So, I bought them and ended up using them. They have ball bearings for the throttle shaft, which makes them smooth as silk. They have a bung located downstream of the butterflies for the primary injectors. So, no more fuel puddling. The only real problem with them was that the intake incorporated a bell-mouth. But I was able to work around that. If it wasn't a p-port engine I could have gone with one larger TB before the intake plenum, but p-port engines run better with the butterflies near the ports. These fit the bill nicely. And it idles much better now.
Mark
P.S. Part of the idling problem was that I didn't have diodes installed on the fuel injectors. Best I can tell, this is a problem for the 3-rotor engines running the EC-2 controllers. Once I added those the idle improved a lot.
On Sat, Nov 24, 2012 at 10:23 AM, <jskmberki@windstream.net> wrote:
Mark,
Do you have any info on the throttle bodies like brand and source? Can you expand on problems with the slide throttle? How thick was the slide? Thanks for any help
Joe Berki
Limo EZ
13b P Port
On Saturday, November 24, 2012 7:36 AM, Mark Steitle <msteitle@gmail.com> wrote:
> Doug,
>
That's true. It is almost like an entirely different engine, especially the MAP readings. I guess you could compare it to installing a radical cam in your family driver. It would drastically alter the driving characteristics. Tracy is working on a fix for the MAP issue on P-Port engines. It only hits two addresses between idle and 4500 rpm. Hopefully, the fix will help it to run smoother through the transition.
>
It also required a whole new intake. I tried the slide throttle, but there were some issues I didn't especially like, so I built one using three 46mm snowmobile throttle bodies. It has worked out great. It especially improved the idle characteristics, probably due to having the primary injectors located downstream of the throttle plates. I had some fuel pooling issues with having them located upstream. The snowmobile tb's also operate much smoother than the slide throttle. At idle, vacuum sucks the slide against the downstream side plate with a significant force, making it difficult to work the throttle.
>
> And... it now burns more fuel than before. DUH! I could throttle back and fly slower, but who wants to do that???
>
Mark S.
>
On Sat, Nov 24, 2012 at 3:43 AM, <DLOMHEIM@aol.com> wrote: >
Mark Steitle wrote:
>"...What I can say is that I picked up 20+ knots on the top end over the original side-port 20b motor".
That is outstanding Mark! I'd almost bet that your PP modification was one of the "easiest" ways to gain those hp numbers vs. a turbo / supercharger add on? Probably wouldn't seem like it as you were going through the "tweaking" phase, etc... :)
Doug
> |