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Author Topic: Saito 40 CL Revisited  (Read 2332 times)

Offline Bob Reeves

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Saito 40 CL Revisited
« on: November 04, 2008, 05:30:04 AM »
Spent the last 3 days playing with and putting test flights on various Saito 40 Four Stroke configurations. Yesterday Joe Gilbert brought out his T-6 to add to the mix as we hadn't quite got there with it yet and needed to do a little more experimenting.

If you are interested in four strokes and haven't been following my trials and tribulations, this thread will give a little more insight into what prompted this latest go around.

http://stunthanger.com/smf/index.php?topic=10668.0

A little more background.. I have really been satisfied with the way my Saito's run and most that have seen them have been pretty impressed with the power and consistency I'm getting out of these little valved wonders. One day we decided to see how one of my Saito 40's would stack up against the TT 36 Joe Gilbert was flying his T-6 with. We swapped out the TT for one of my Saito 40's and Joe flew it a couple times. The next day Joe ordered a Saito 40. BTW: The Saito bolted right up, mounting holes are the same. After Joe's Saito CL engine arrived and a little more experimenting I started the above thread.

Also I have a confession to make.. I have been preaching about my engines burning fuel thinking all along that if you fill a 4 ounce tank you are using close to 4 ounces... Well I noticed real quick that when I filled the tank using a syringe I could only stuff 3 1/2 ounces in it and when I fuel it from the pump on my flight box I don't fill it quite full. All this time I have been thinking I was using close to 4 ounces when according to the markings on a syringe it's really closer to 3.

What I wanted to accomplish over the last 3 days was... Using my setup as a base line I wanted to first see how the stock Saito CL engine (set up exactly as Saito recommends) compared to my engines and see if the new Brodak Y&O 11-6 could be made to work. The props I am using are Rev-Up 11-7's which are a bit hard to come by and I would really like to find a current production prop that works as well. We also wanted to see if the hard tank on the T-6 could be made to work as well as the clunk tank on the TwistMaster.

The two airplanes used for the test flights were my 8 year old TwistMaster and Joe's T-6 which was built by Don Hutchison. The engines were Joe's new CL 40 broken in properly and two of my Saito 40's one is a well used eBay RC engine that has who knows how much time but still runs great. The TwistMaster has a 4 ounce clunk tank and The T-6 has a hard tank that can be ran Uniflow or conventional vent.

First up was the stock Saito CL set up on the TwistMaster, I used 10-20 all synthetic fuel, the recommended 11-4 APC prop and started with the insert in the venturi. After a couple flights I removed the insert and ran it wide open. We then put this exact set up on the T-6 with the hard tank and ran it both with uniflow and standard venting. All flights were on muffler pressure with the needle valve set just on the rich side of peak RPM.

While the CL venturi was on the T-6 I went back to one of my modified RC carbs on the TwistMaster with the Brodak Y&O prop, PowerMaster YS 20-20 fuel and adjusted the choke screw for 8400 RPM to compensate for the reduced prop pitch.

After flying both the T-6 with the Stock Saito CL set up and the TwistMaster with the 11-6 prop we pulled the modified RC Carb off the TwistMaster and put it on the T-6 with a Rev-Up 11-7 and YS 20-20.

Yesterday was a pretty good day for this as the wind was blowing 12 to 15 MPH which would challenge most pilots and engines. No question, Joe and I both agreed along with our observer Tom Martin the best of the bunch was my original set up on the TwistMaster with the clunk tank. Joe is going to switch out the hard tank on the T-6 and keep the modified RC carb.

Please understand we are splitting hairs here. The stock Saito set up does work (without the insert) and so did the Brodak prop but we were not after "good enough" we were after "as good as it gets". I am now completely convinced the set up I developed with the help of Brad Walker, Doug Moon and Allan Perret two summers ago is as good as it gets.

The stock Saito CL set up with the insert in was.. well guess the best word to describe it is "wimpy", It just didn't have the drive and authority in the wingover and square 8 my set up does. Without the insert it was much better but still had issues with lap time speed up on a conventional tank (both clunk and hard) and sagging on uniflow.

The 11-6 prop with my set up was better than the stock Saito set up by a hair. It didn't speed up quite as much during the flight and didn't quite have the drive going over the top. It was a flyable set up that if I wasn't spoiled by what I have been use to I would probably be perfectly happy with.

Every since 4 strokes started appearing in CL circles most have discovered what we proved to ourselves yesterday.. Plastic RC tanks just work better than hard tanks. Joe's last flight yesterday was with the T-6 on a hard tank running muffler pressure non uniflow. It did run well but it burped on the down leg of the vertical 8 and quit when he did a loop toward the end of the tank (tank still had about 1/2 ounce of fuel).

Some of you will say the early quit was fine and on two strokes a cut off loop is part of the game. My thoughts are with a 4S we are only starting with around 3 ounces for the pattern and might be taking a big chance on it quitting early. We are pretty sure the burp in the vertical was the pick up tube being uncovered on the down leg which I have never seen happen with a clunk. As I said we are splitting hairs.. Yes a hard tank will work but.....

Where do we go from here....

First, it was about 75 deg with 40% humidity yesterday which (except for the wind) were pretty good conditions. This hasn't told us what the Stock Saito CL set up or an 11-6 prop will do on a 95+ degree Oklahoma or Texas day. I have a pretty good idea but can't really prove anything till next summer.

Sorry Saito you didn't quite make the mark with your recommended CL set up. I have the CL manifold off Joe's CL engine and plan on doing further testing and development. I am going to start by drilling out the spray bar hole to the same size as a PA (see the above link) and add my nylon screw choke adjust. If that doesn't work I'll try the spigot insert I made with the OS needle. I have no doubts I can get the CL manafold working as well as either my modified RC carb or my modified UHP just not sure which way I will need to go yet.

Sure wished I could talk John Brodak into adding an 11-7 to his Y&O prop line or even Eric Rule to his. The ones coming out now are really good looking props and I believe an 11-7 in either line would be as good as the Rev-Up. problem is I'm afraid to ask as I'm not sure how many they would actually sell.

I didn't credit Allan Perret in the previous thread for giving me the original idea of modifying the stock RC carb, couldn't remember his name and had to look it up in my old email archives.Thanks Allan..

Well know you know everything I do about the Saito 40 I have spilled my guts and hope this helps.. A few pictures would be good right....


Offline Allan Perret

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Re: Saito 40 CL Revisited
« Reply #1 on: November 04, 2008, 11:02:22 AM »
Thanks Bob:
Appreciate the recognition of my contribution to your 4-stroke development. 
I am still chasing that "good as it gets" set up myself.  I don't get to fly much so my progress is slow compared to yours.   Even still I did manage to win 1st place with my Saito40/Pathfinder at last year's Baton Rouge contest in both P40 and PA (advanced class).  But the wind was just about a perfect light breeze, and I feel my setup is still marginal if its blowing.  Only recently swapped over to a plastic clunk tank,  but I still have some sagging in 1st part of pattern and later in overheads.  Everything else is per your set-up;  YS 20/20,  RevUp 11-7, 8300~8400 RPM. 
    I have a slightly used Saito 56 (RC version) and one of the new 62 c/l versions.  Plan on putting one of them in a Magnum I have.  I also have one of the T.Dixon venturi's I had bought for the 56 which I suspect would fit the 62 also.  Which way would you go with the 62, factory c/l venturi or the Dixon?  I would probably modify either one with an air screw adjustment. 
 
Allan Perret 
Allan Perret
AMA 302406
Slidell, Louisiana

Offline Bob Reeves

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Re: Saito 40 CL Revisited
« Reply #2 on: November 04, 2008, 12:19:02 PM »
Hi Allan,

Yes the Dixon 56 venturi will fit the 62 and I would use it, mainly because you have it and bolting it on is easier than modifying the RC carb. Replace the ST spray bar with a PA, stick a 1/4-20 nylon bolt down it's throat or figure out some way to adjust the choke area and you should be good.

Not sure I can help with the 40 via long distance but 83~8400 sounds a tad fast with that prop. What length lines are you running? You may be OK with the choke adjustment but need to richen the needle a bit more and possibly shorten the lines.

It's sagging because for some reason it isn't getting enough fuel when it needs it. Lots of things can be the cause and besides the normal stuff, fuel line leak, plugged filter etc. which you have probably already eliminated as the cause.. you are dealing with an engine that is very sensitave to fuel delivery. 

The 40 seems to be allot more finicky about this than the larger engines. I was fighting a problem with the 40 on my Ringmaster 576 and finally traced it to a leak where the pipe plugs into the head. A little high temp RTV fixed it. On another one we found a very small sliver of silicon fuel tubing in the spray bar.. Guessing it was cut off when the fuel tubing was installed or was inside the tubing from the factory.

Good luck and stay in touch
Bob

Offline Allan Perret

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Re: Saito 40 CL Revisited
« Reply #3 on: November 04, 2008, 02:00:04 PM »
Using 60' lines, eye to eye. 
If I had to guess, I might be running the needle a little to lean. 
I have had some runs where I set it too close to peak and it bogged down bad and got hot.  But that Saito takes a licking and keeps on ticking.
Allan Perret
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Slidell, Louisiana

Offline Bob Reeves

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Re: Saito 40 CL Revisited
« Reply #4 on: November 04, 2008, 02:40:45 PM »
Might be running it a bit lean, I run 58 feet eye to eye with lap times right at 5 seconds.. Next time out try this.. Put it on 58 foot lines, leave the choke screw where it is but richen the needle to drop the RPM down to ~8200 and let me know how it does..

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