GLRogers

My Feedback: (2)

PlaneKrazee
Joystick

Thanks for the input. Easy enough to try on next time out which I am hoping will be Saturday.

PacificNWSkyPilot

My Feedback: (19)

Could that cause it to flame out when you advance the throttle? That's what happened to me, and I'm determined to figure out why. It idles perfectly, and throttles up perfectly, but when I get it into the air and try a slow idled-down flyby the RPMs are up substantially higher than they should be. I advanced the throttle to do a go-around, and it kicked and bucked for about 5 or 10 seconds, and then died. Unfotunately I didn't get another chance to do any other testing or adjustments as it was in a bad spot and I dinged the plane. Didn't tough the Syssa, though.

I want to make sure this is straightenened around when it ends up in the next bird, which is on its way right now.

~ Jim ~

Joystick TX

I'm not sure about the in-air flame out. But it seems like being rich on the low end could cause it. Mine never did that, it just took about 5 to 10 seconds to get to a slow idle on the landing approach after flying the downwind leg at about 1/4 throttle. I landed HOT a few times before I got it fixed. We have several hundred feet of grass runway with tall weeds at the EOR, so there was no need to throttle up and go around. BTW, past the weeds are TREES so a go-around with a poorly running engine is dangerous. The adjustment required was very minor, seems like it was only about 1/8 turn.

I am still new to gassers and am still afraid to play with the adjustments very much. I did blow about two tank fulls of gas trying different adjustments to see what would happen when I first got the engine. It seems to be more sensitive than my FPE, but once the adjustment are right on, they seem to be good for several months. I still don't like to mess with them at all unless there is a known problem. If the engine is running good, I don't try to get that last 50 RPM out of it like I did with the glow engines.

Truckracer

My Feedback: (19)

I owned a Syssa and for my style of tuning and flying, I couldn't get use to the carb with the accelerator pump! I had numerous flameouts because the low end was set overly lean because I set the low end based on how the engine accelerated. With a normal carb without the accelerator pump, I adjust the low mixture so the engine just accelerates smoothly when the engine is warmed up to full temperature. When cold, it is not unusual for my engines to not accept throttle from idle ... they become normal when up to operation temperature. Yes I do adjust the low speed needle for a best compromise between how the engine runs at low to mid stick and how it accepts throttle changes. Has worked for me for many years and I usually have great running engines. The trouble with the accelerator pump is that it masks the engine being too lean at low speed as the burst of fuel when the throttle advances will allow the engine to accelerate as if the mixture is correct even when the low speed is a bit lean. Carbs with accelerator pumps have to be adjusted to where the idle seems a bit too rich on acceleration for the actual setting to be correct. The problem here is that in a situation where the idle is slow and the engine is running a bit lean at idle, sometimes the accelerator pump doesn't add enough fuel to overcome the lean condition when the throttle is advanced .... the result is silence as the engine gasps for fuel and air and just gets mostly air!!

Todd sent me a different carb w/o the accelerator pump and it worked very well without any of the above listed quirks. The replacement carb was the same one used on the tried and true Zenoah G-26. Very few of the Walbro carbs we use for RC applications have accelerator pumps .... the Syssa being a rare example of one that does.

Since my Syssa adventures, I have since switched to a DLE-30 and its power curve more suits my style of flying. Just to be clear here, this post is in no way putting the Syssa down .... it is a great little engine of the highest quality. I just couldn't get along with the original carb .... a personal preference thing I guess.

Your problem may be a different one but for me ..... nix the accelerator pump.

PlaneKrazee

My Feedback: (14)

I was taught by a very good IMAC competitor to: warm the engine up, lean the low end until it quits on throttle up and richen until it will take the throttle. Adjust the idle trim a little higher than minimum and fly it. Works for me. I haven't had a dead stick landing (other than running out of fuel) in years.

BTW, we might be talking 1/16th turn one way or the other to get it perfect. And you should be tuning the high needle only 100 rpm richmax from the get go to prevent excess carbon.

Truckracer hit the nail on the head. Richen the low end a tad.

My MT 70s runs better if the low needle is slightly rich and the high end peaked.

PacificNWSkyPilot

My Feedback: (19)

Okay, I've been told to lean out the low end in one post earlier, and then to richen the low end in somebody else's post.

I lean toward it being too lean, and here's my reason why. When I did my pre-flameout slow fly-by, I couldn't get it to idle down. It was running at a pretty high idle, and there was no decent response at all, like the throttle wasn't working. But I checked the linkage, it was fine. And i shouldn't say there was no response, there was a change when I applied the throttle, mostly hiccuping and erratic sounds. I gave it more throttle to try to go around, and that's when it quit. One thing for certain, it was fine....perfect even... until it got to the point where it was at full running temp. That's when the trouble started. The first time it was on the ground. The second time I thought I was okay and didn't wait until it heated up. Big mistake. But at least the Syssa was fine.

I'll get it worked out. There's no doubt in my mind. I was just wondering if these symptoms sounded familiar to anybody.

The symptoms truckracer described were not too far off from mine, but enough that I know we're talking about different behavior.

I also know in some cases a gasser and a glow act exactly the opposite of each other, when a glow is heating up at the low end it needs more fuel, whereas a gasser MIGHT need to be leaned at that point.

Probably the most frustrating thing to me is that the gasser worked perfectly a few months ago. So I'm assuming it's either the weather (the heat here in Texas) or the gasoline, which smelled just fine and is only a few months old. It's easy to eliminate that one, just brew up some fresh mix. I just wanted to see who else might weigh in with some ideas.

I thank you guys, and I listen to anything said. It helps me to weigh my options...

~ Jim ~

JoeAirPort

My Feedback: (41)

If it won't idle down, low needle too lean. Richen it.

PacificNWSkyPilot

My Feedback: (19)

It does idle down, right up to the point when it won't (when it's hot). Right after that it balks and dies. So...you say, that's a sign that it needs to be richened? On the low end needle? Both?

Thanks.

~ Jim ~

RPool

Quote..."If it won't idle down, low needle too lean."

Joystick TX

I think you need to take the TIME it takes to idle down into account. To me, it makes sense that if the engine takes a long time to get to a low idle, that indicates a rich condition. If it was lean, there would be no fuel to allow it to run for a long period of time. If the idle is just high, that could indicate a rich condition.

I have not had any problems with the accelerator pump, but I am using a light-weight spinner and a light-weight prop (Vess 18") with a low pitch (6"). My engine spool-up is as fast as the servo can move with no hesitation at all.

The pump may cause a problem if a heavy, or large diameter, or high pitch prop is used because the pump would be putting in more fuel than the engine could burn which would cause a "temporary" rich condition with a fast trottle up.

Flying style does matter, I like to really "punch it" when I take off, so I like the instant throttle response that the pump provides.

PacificNWSkyPilot

My Feedback: (19)

There ya go. Two opposite pieces of advice.

Both have good points.

I'm still convinced the engine temp is pivotal to what is really happening here. It does not happen in the air or on the ground when the engine is cooler. It only starts to occur when it it's good and hot. And remember it never happened before, and this was the first 95 to 100-degree day I've flown it.

The prop is a wood Zinger.

~ Jim ~

JoeAirPort

My Feedback: (41)

Sounds like some issue with the engine. The only thing my properly tuned gassers do is increase idle RPM as they warm up. In fact my glow engines did the same. It's totally normal. What you're seeing is not normal IMO. If mine take long to reduce to idle RPM it's always too lean. If it drops down right away....so low it almost quits, that's too rich. Tweak your low needle and see if it goes away. The forum gives suggestions, which are proven or disproven only by trial. If you find that needle tweeking won't fix it, then there's something wrong with the engine.

Joystick TX

Cooling could be your problem. It is an easy fix. I had to open up the exit a bit on my GSS at the start of summer.

Recently, it was over 100 degrees here for 18 days in a row and I flew almost every other day and I never had to adjust the needles.

PacificNWSkyPilot

My Feedback: (19)

Steve, If you could show me how much you opened yours up to achieve the best cooling, I'd appreciate it. You know how it is, we estimate that we've got enough flow, and we always try to be conservative and not cut up our cowls any more than we have to. If you had to open yours up some more, then you've been through it. Mine is also a GSS, so I can simply follow suit. As soon as that brown truck shows up at my door, that is!

Thanks, I appreciate it. I hadn't discounted that it might be getting too hot, that was rattling around in the back of my tiny little mind.

~ Jim ~

ghoffman

My Feedback: (3)

This is the way the cowl is cut on my EF Extra. It looks minimal, but with the ES pipe, the exit area is pretty big. I saw an IR cylinder head temp of about 180F after taxi'ing back in on a hot August day.
http://www.youtube.com/watch?v=vg6YtO17oNQ

Joystick TX

For the GSS, I just cut a 3/4" by whatever the cowl width was out of the rear of the cowl. I put a picture of the front opening, which is rather large and before I made the rear opening larger, in my gallery.

The exit area opening should be 3X the inlet area. Internal baffling like they do on "real" aircraft may also be required to direct the flow around the cylinder.

Computing areas of odd shaped openings is not fun for me, so I cheat a little with some TLAR engineering. I bend a piece of wire to the shape of the inlet opening then bend it into a square and compute the area. Then I do the same for the exit opening. I cut untill I get the correct ratio. This method may not satisfy a math PHD from MIT, but IMO it is close enough for hobby work.

If someone has a better or easier method, post away!

MTK

Gary,

Where did you get that really cool red anodized header? I want one

PacificNWSkyPilot

My Feedback: (19)

Steve,

Thanks for the tips and the photos. I checked your Gallery and got a really good look at yours, that tells me what I need to know about mine. I'm certain that my openings were correct on the bird I had it mounted on, I had at least that much flow-through, actually a lot more. So, that's good.

Back to my gas mix and my mixture screws. One thing I'm not familiar with here in Texas is how long gas mix will remain viable in a garage that often is 90-something degrees. I keep it in the shade, mostly.

I had a friend recommend that I use aviation gas, he says that it doesn't lose octane while sitting around like regular gas does. I wonder if Todd has any thoughts on that? It seems to me there would be quite a difference in Octane with that, and as I recall, Todd once told me that this engine was designed to run well on just regular gas, and may not run well on higher-Octane stuff.

~ Jim ~

ghoffman

My Feedback: (3)

It is the standard header that I had anodized. I was doing an anodizing run for my company, and they just added it to the batch run. After running it for a few hours, it is now kinda pale pink. I will be doing an anodizing run next week, so if you want to send me one I will get it done for you.

MTK

I ran AvGas in mine for two flights. The 100LL AvGas has much too high an octane rating for the SAP...engine ran fat throughout its throttle range. Mid range was particularly fat. Leaned it out some and it helped. Engine did not die in the air but was close.

AvGas is designed for higher compression and higher altitude running. Higher compression could result in pre-ignition or detonation, so AvGas controls that. Vapor locking that could happen at high altitude operation is also controlled by AvGas. Neither of these conditions are found in operating the SAP180HP so AvGas is of little or no value.

Nevertheless, AvGas has a great odor when compared to stinky AutoGas. It is also much more stable than autogas which means prolonged storage doesn't affect it.

A realistic maximum storage time for autogas is around 2 months. Last March I mixed 5 gallons of autogas which lasted 5 months...much too long. Gas had turned back in June. However, the engine still ran on the poorer quality gas, but I wouldn't recommend that. Now I only mix 1 gallon at a time which lasts a month give or take, for my style flying.

ghoffman

My Feedback: (3)

I have a couple of gallons of NASCAR unleaded, 100% gasoline from New Hampshire Motor Speedway with 50:1 RP in it. I will try it Sunday, weather permitting.

PacificNWSkyPilot

My Feedback: (19)

Yeah, I had some issues with gas fumes coming back from the field the other day. I had to ride with the window open. My gas can it a safety can, seals absolutely. But the plane had been knocked around, so I couldn't control all aspects of that. I'm going to make sure I bring a garbage bag to tie around the plane in case of such an occurance.

Jim

Joystick TX

I try not to keep gas over a month for my plane engines. I only mix one gallon at a time, which I burn in a week, so I never have worried about storage time. Been using 87 octane with 10% ethanol with no problems so far.

I have used gas that was almost a year old in my mower and weed eaters without noticing any problems, but they are not high performance engines.

rmathews

My Feedback: (1)

Texas Sky Pilot,I had the same gas smell problem driving home from flying,started pluging the vent line and this cleared the smell up. Rich

PacificNWSkyPilot

My Feedback: (19)

I've never had this problem before. The plane had been busted up some. I've got plugs for the vent line, though, so it can't hurt to do it. Thanks.

~ Jim ~