chuskers

I have a Saito 200TI on a new Hangar 9 Spitfire, and discovered a symptom at the worst possible time: on takeoff.

First, I broke in the Saito thoroughly with 2 gallons of fuel, and it was hitting prime RPM figures on the ground, with smooth running at all throttle settings.

After mounting it to the plane, I took it out to the field and once again had a very smooth run-up on the ground with a same-sized propeller (16"). After several taxis up and down the runway, I began a takeoff roll, and as the tail came up and the Spit lifted off, the rear cylinder dropped out. Fortunately, the 200 on one cylinder has just enough power to keep this bird in the air, and I completed the circuit and successfully landed.

Next, the cowl came off, we put it on the stand, and doublechecked needle settings, etc. Everything seemed to run great, but when we raised the tail to simulate the takeoff roll, the rear cylinder immediately dropped out, followed by a rather large amount of fuel blow-by out the muffler (for the rear cylinder)

After much tinkering, etc., we weren't able to eliminate this, so I decided it was time to do some research back home. I confirmed that all of my valve clearances and glow plugs were on point. I've also found online that the 200 was designed to have the rear cylinder run a bit richer for cooling reasons, so it is more sensitive to running over-rich than the front cylinder.

The best theory I can arrive at is that the standard fuel tank position in this aircraft (see attached image) is way too high for the carb position on the 200. When I bench-ran the engine, the tank centerline was below the carb. On the Spit, when the tail is resting on the ground, the end of the clunk is once again below the carb. But when the tail raises up, the tank centerline rises significantly above the carb, perhaps forcing the mixture over-rich?

Perhaps an Iron Bay or Cline regulator would help alleviate this? Looking forward to ideas/thoughts/questions.

TomCrump

Can you lower the tank position ?

1QwkSport2.5r

Lowering the fuel tank OR adding a fuel pump and demand regulator are the options here; as outlined in the other forum where this question was asked.

chuskers

Thanks everyone! Unfortunately all of the servos are immediately below the tank... there is no room to lower it without completely reworking the inside of the fuselage. I'm leaning toward trying a fuel regulator... interested if anyone has had experience with them.

I'm typically a big fan of being on-spec... I'm thinking that Hangar 9 was betting most people would be putting gassers in this plane, and as I understand, Walbro-style carbs are much more tolerant of tank position.

1QwkSport2.5r

I'd call Horizon before doing anything major and costly.

chuskers

Thanks everyone! I'm going to start with a fuel regulator and work from there. Very much appreciate the input- I wanted to make sure I wasn't missing something completely different.

Hobbsy

My Feedback: (102)

The Fuel Regulator assembly has been in constant production since 1996 and includes two plastic tee's for filling your tank, one brass tap, and one plastic check valve to pressurize your fuel tank.

It sells for $43.95 plus s&h. To order, send an email to [email protected] with your shipping address and desired quantity and we will reply with a Paypal invoice.

Iron Bay Model Company Wheeling, W.Va

http://www.ironbaymodelcompany.com/i...ebsite_010.htm

nilsreinert123

I also have a 200 ti on a Spitfire and it has been running very good for over a year now , before you start to add and change stuff you must check the low speed needle setting , it should be as lean as possible. What fuel are you using ? I have been using 15% synthetic oil 15% nitro. Its all about the low speed needle.

GoNavy

My Feedback: (15)

I have a Magnum 160 twin cylinder running on a Cline regulator, because the low position of the carburetor made it impossible to align the tank c/l with the carb. The fuel does not siphon thru the regulator.

I have used regulators with other 4 stroke singles and a 2 stroke Bully 120 with success. The only issue is priming the engine. You might crank and crank and think you have a bad plug. In most cases I need to temporarily block the muffler exhaust and use an electric starter to build up the pressure. If the carb is accessible, you can prime through the carb. Choking alone on the Magnum doesn't seem to pull the fuel through the regulator.

chuskers

Thank you everyone!

I purchased and installed an Iron Bay fuel regulator, and the symptoms were eliminated in ground testing... next step is to get back in the air.

Nils, thank you - as I fine-tune I will put your advice to use. GoNavy, your priming advice is also of great help. I found I was able to choke my carb by hand and draw the fuel through with 1 1/2 revolutions. Runs great now!

GoNavy

My Feedback: (15)

That's interesting. All of my regulators were Cline units. The Magnum 160 has a choke and I tried that without success in drawing enough fuel (hand cranking) to start.
Perhaps the Iron Bay unit works a bit differently than the Cline.

Hobbsy

My Feedback: (102)

Both the Cline and the IronBay will pass fuel when chocking, they do work differently from each other, the internals work almost opposite each other.

the Wasp

My Feedback: (1)

Hobbsy,, am I wrong here ???,,, over the years I have seen a lot of photos of the IronBay unit, because the Fuel Inlet is in it's center, it looks to me that the IronBay unit has a shut off valve on it's Diaphragm at it's fuel inlet that stop's the fuel going into it as the engine come's down off the throttle, so because it's an "On Demand" unit this would help the engine from loading up with fuel at idle after coming off the throttle

???

Jim

Hobbsy

My Feedback: (102)

I am not sure how to say this, in the IronBay the fuel pressure from thank aids in opening the fuel valve, which is a common Schrader valve for tires. In the Cline the fuel pressure tries to keep the fuel valve closed, that's why I said they work opposite each other. I do know that they will work on engines from a little Saito .30 up to and including the Saito 2.20. Now, John at IronBay was hesitant to say the IronBay regulator would flow enough fuel for the 2.20 but it did. Several on here have worried that there was something wrong with their regulator when they couldn't make their engine run super rich when using a regulator. You said the magic word, "demand" the regulator only feeds the engine what it demands plus a couple of hundred rich. I like the regulators for their consistent running from full tank to empty. Some say the regulators won't work with air bleed carbs but they work just fine. There is still demand at idle. Getting a fuel line on the inlet of the IronBay is a bit of an effort but is doable.
.

chuskers

Fascinating stuff - thank you for sharing, everyone!
There is one additional point of curiosity for me, from the other forum... I installed the Iron Bay regulator without a check valve on the muffler pressure line, and achieved steady fuel flow on two tanks that I ran through on the ground.

If the Iron Bay is demand-driven, and the single carb on the Saito 200TI appears to be pulling enough fuel at all tank levels and throttle positions, is there a particular need to add a check valve to significantly increase tank pressure? Could this be a rare situation where the 200TI has a higher-than-average carb suction? I've emailed Iron Bay in case there's a specific reason the regulator needs high supply pressure. But it sure seems to work well with standard muffler pressure!

I have about a week before I'll get a chance to fly it, so I have some time to do more thinking

the Wasp

My Feedback: (1)

edited, I would say because the Unit is not setup as a pump, it needs a given amount of pressure to help make the Diaphragm to move for a given size engine, so the larger the engine the more pressure it will need,,, I would start your plane and hold it nose up and upsise down to make sure you have enough Tank Pressure without the Check Valve,

Hobbsy,, I found this photo, you can see on the center of the Iron Bay's Diaphragm that it has a Plug type Valve that will plug off the Feed Nipple,

Jim

Hobbsy

My Feedback: (102)

Yes sir, the feed nipple is plugged off by the Schrader valve, the diaphragm opens the Schrader valve against the valves spring and the tank pressure. The fuel draw at the carb pulls the diaphragm toward the Schrader valve stem allowing fuel to flow. I talked to John at IronBay in 1996 or so and his words were that, "it only takes a breath" of fuel draw to allow fuel to flow. That could very well be my own picture. That's my take on it, if others see it differently, let er fly. PS, the reason that I called John was that I was curious to see if he had a special Schrader valve made with a weaker spring to serve this purpose but he assured me it was a standard Schrader valve. A replacement would be cheap if ever needed.

the Wasp

My Feedback: (1)

Hobbsy, I had a Magnum 180 4St, it would never idle well at all when the fuel tank was full, I had to have the idle set high to keep it from stalling, at that it would pull the plane (a 76" span Edge w/APC 17X8w) while at idle,, but when the fuel tank was low I swear that engine would idle around 1400 RPM,,

everything in my mind told me that engine needed a Regulator, some people said a regulator would work, then some others that have been in the hobby for 30 years told me it wouldn't work,, I still think it would have worked, but I burned up the engine,, I hope to order my new Saito 125 this week, I will be ordering 2 new IronBay units too

Jim

Hobbsy

My Feedback: (102)

You'll love the 1.25 it's as user friendly as can be.

chuskers

Hey everyone,

Thanks for the inputs! I definitely plan to do some more nose-high-nose-low tests before flying, to be sure.

John from Iron Bay provided the following background to me today, and I rec'd permission to share:

"The check valve is a device to create pressure in the fuel tank. This in turn forces fuel into the regulator regardless of tank location or g-forces.

For example, in the 1990's I built a 4-engine DF 747 Jumbo Jet for a NASA research project. The tank had to remain on the CG which meant two engines were 8' away from the tank, and two engines were 6' away. No big deal when sitting on the ground, but when in flight two engines would invariably be a foot or so above the tank and two below at any given time as the plane rolled. This was a nightmare and caused flame outs from both flooding and starving.

Addition of four regulators, one for each engine, and a pressurized fuel tank eliminated all problems because the tank location was no longer a function of the fuel delivery system. The only thing that mattered was keeping the regulators close to the carbs.

If your carb has good vacuum, and your tank is relatively close to the engine the check valve is not always needed."

Hobbsy

My Feedback: (102)

You have to understand the fuel is being pushed through the regulator at atmospheric pressure when you're choking, when not choking the low pressure created by the venturi will flow fuel but won't be adequate during nose up and maneuvers When there is no tank pressure the regulator really has nothing to do, it's just additional plumbing.

the Wasp

My Feedback: (1)

Hobbsy,, one guy that told me that the Regulator would not work on my Magnum told me I needed to lower my Fuel Tank. well my God, cut up my plane's frame to lower the Tank so the engine would not pull so much Fuel while at Idle, just what an On Demand Regulator is made to do, they work great on Weed Whips

Jim

Hobbsy

My Feedback: (102)

If you try one you'll be impressed at how consistent the engine runs from full tank to empty. Plus, you no longer need to run it rich at full tank so it won't lean out at lower fuel levels.

captinjohn

I am trying to get this website working again. I was not to active posting, but done some reading since hand surgery. How do I finish changing my email so this all works again? MORE ADDED .. I can do some things on here, but cannot change to my new email address so I can sell some New engines I have in the classified section. Thanks John

Hobbsy

My Feedback: (102)

John, on the thin blue bar above, click User CP on the left most end, then Settings and Options on the left column, then Edit E-mail, that should get you there.