1967brutus

Because "efficient burn" is not a function of "metering fuel into an airstream", but of "mixing and evaporating homogeneously" and that is a task basically no tiny carburettor can do on its own. It needs assistance of the rest of the intake tract, and radials are noticably less good at that than singles and twins.

Walbroes are maybe pretty good at metering fuel, but not all that good at mixing the two properly, period. At least the small ones for weedwhackers and our model engines. Not talking about the Walbroes intended for jetskis, skidoos and bikes, those are quite a bit better at it, because they have features like secondary air circuits and emulsion tubes and such.
Glow carbs also suck at it, but those usually get assistance from a spinning crankshaft (2-strokes) or a hot header tube, and glow fuel is less sensitive to it anyway due to its very wide ignitability range. Gasoline is a bit more finicky in that respect.

Your big walbro equipped gasers also run an entirely different fuel/oil ratio, the amount of oil needed to create that big mess simply is not there... I might have said that 20:1 versus 15:1 does no not make a whole lot of difference, but 50:1 DOES make a difference.
2-stroke oil does not really burn off during combustion. A tiny bit does though. Now when there is 5% oil in the fuel, chances are, most of it leaves the exhaust still in liquid state. Some of it burns, most of it not
When there's only 2 or 2,5% of it, chances are most of it either burns off, or evaporates, leaving zero to none "wet" oil messing up your plane.

1967brutus

Look at it from their side: If Saito provides that info, for them it is safe to convey it to you. If Saito does not, it would require them to do measurements. Measurements take time and cost money, that they won't earn back by selling more engines, but which can lead to dissatisfied customers if a customers experience for whatever reason would not match their numbers. And since practical fuel consumption is depending on a LOT of variables, no way of telling if that will be the case.

Had I been in their shoes, I would have responded the same. Why take the risk of a dissatisfied customer? It consumes what it consumes, the customer will find out soon enough how much that actually is.
Now would a customer ask me is a given consumption is acceptable/correct, then I could have answered with a comment like "yes that is to be expected" or "no, probably something is wrong". But not before.

But to answer your question: Without owning one, but based on education, theoretical knowledge and experience with various different fourstrokes in different configurations, for that FG90R I would expect a WOT fuelconsumption of around 90 oz/hr, give or take 10-ish In other words, somewhere between 80 and 100 oz/hr. More with smaller/lighter props, less with larger/heavier props

BarracudaHockey

My Feedback: (11)

I fill up my Hangar 9, rip around for 10 minutes which is about as much as I can stand, land and have half a tank left, If you can track down that tank size you might be in the ball park.

The problem with asking Horizon is you might get a guy that knows one thing and get a dissertation back on RC cars or whatever he's into but if you ask a Saito question he looks in the manual. Versus catching the guy that actually flys giant scale and might give you a better answer.

1967brutus

Which Hangar 9 is that? It's a brand, not a type...

BarracudaHockey

My Feedback: (11)

Sorry I forgot a word
Corsair

planenutzz

interesting discussion on the black goo. My Saito FG-90R3 was spewing copious amounts of black goop but after about 2 - 3 hrs of running has decreased a lot.

The worst engines I have for that is my MVVS 30 (walbro) & DLE-111 (DLE carb), both leave a thick mess after flying all over the model and it is a pain to clean off. I will try what the other chap suggest with WD-40 then some kitchen spray cleaner.
Water Displacement #40 has many good uses!! Not just for Thikol missiles!
Having said that as I have a mix of older well run in engines and new ones I tend to just have one can of fuel I use in all of them and it runs Castrol TT mineral 2 stroke oil, 91 or 95 petrol @ 32:1. Note our octane rating here is different to you guys across the ditch.
95 is hard to find here, my local BP only has 91 or 98 and you have to watch you do not get an ethanol blend with the lower octanes here.

Rough approximation I stole from Dr Google:

USA 91 MON is similar to Australian 95 RON
USA 93 MON is similar to Australian 98 RON
USA 87 MON is similar to Australian 91 RON

cheers
me

1967brutus

Judging by the size of the plane, the engine size it was designed for and experience with other planes of similar size, I't say it came with a 1 litre-ish (32 oz-ish) tank. At least, my Seagull FW190A came with that size. If true, that indeed would suggest a fuel consumption of approx 90 oz/hr

1967brutus

Engines do that. In general the residue decreases after a few hours of runtime. Fairly common phenomenon. They also generally accept leaner mixture and make more power.

Try Castrol PowerRS 2-stroke (might be called Castrol TTS in some places). Your engines will like it.

RichardGee

My Feedback: (156)

Saito does provide fuel consumption for some of their gas four stroke singles, just not their multi-cylinder engines. Example: The FG-40 consumes 30cc/minute @ 7500 rpm
Well, your calculation is about what I assumed from Jaketab's post and the 'mileage' he was getting from the tank in his Zero.
I do find 1.5 ounces a minute at WOT to probably be about right.
I am not a big fan of running radials WOT for any length of time on the test bench, which is why I didn't (or haven't) measured consumption myself.
The issue of fuel consumption is important based on a number of limiting factors with my current tank install.

planenutzz

Indeed though on the Saito I will keep it to the recommended ratio. Here we can only use Klotz KL-200 as the importer won't warrant the engine otherwise.

My Zenoahs, DA, DLE etc are happy to run on the racing motor bike oils. Though I have a mate who is talking me into running on redline so I bought some, not tried it yet.

Will probably need to have about 4 cans with various oils and mixes!!

Run in standard engines 40:1 redline
New engines 32:1 castrol mineral TT
Saito FG90 Klotz KL200 @ 15:1, interestingly my little FG-21 is 20:1 - maybe once the 90 is full run in I can just stick to the 20:1 ??
Supertigre ST2500 converted to petrol will be klotz KL200 @ 12% or approx 8:1, remember this had been a glow engine and does not have bearing races.

planenutzz

I have some Castrol TTS on the shelf , it is easy to get here. Sorry my earlier reference to castrol TT should be 2T mineral.

1967brutus

I get what you're saying, but I cannot say anything about Saito's decision not to provide that consumption info.
No fan of running radials at WOT on the ground either, but if this helps:
If you can do a decent peak RPM measurement, take a good propcalculator and check what output that translates to. Use output in kW (HP x 0,735)
Your engine will by and large (generally accepted rule of thumb for a naturally aspirated gasoline engine) consume 300 grammes of fuel (not counting the oil) per kW per hour.
That converts to 14,1 oz per hp per hour.

I just checked Saito's specs on that engine and Saito claims the engine can produce 6 hp, so that would suggest it is capable of consuming about 84~85 oz of gas per hour, excluding the oil. At 20:1 that would mean we need to add some 4,25 oz to that, and then we are pretty close to the 90 oz I estimated earlier. I only have to retract the "give or take"... Consumption could be less (depending on propsize and throttle regime), but most likely not more than 90 oz per hour.

1967brutus

It is completely up to the user, of course, but personally, I would completely forget the mineral oils, there really are NO situations where mineral are offering ANY advantage over synthetic, or it must be the "shorter break in", and I found that to be dubious as well. In my experience, it takes a ringed engine 20 hours to fully break in, regardless of oil being used, and the only difference I saw was that SOME engines (not all) accepted full load earlier on mineral oil. But in all cases tolerances remained better breaking in on full synthetics.

The warranty condition (Use Klotz or else...) is a dealbreaker of course, but if it is of any help, I know for a fact that a Saito WILL survive on TTS just as well, I have run enough of them even ones that did not leave the factory as a gasser originally to know for sure. I would, in ANY case, not use mineral oil in a Saito single cylinder FG though, on account of the unbushed conrod.

Castrol TTS (later renamed to PowerRS-2stroke) was recommended to me by my local motorcycle workshop owner, who is an avid off-roader. He sells oil and has a shelf full of different brands, all reputable. He was very specific on the TTS' ability to cope with lack of cooling due to mud-caked cooling fins and that was what I was looking for, because I convert glow engines to gasoline, and that means "limited cooling" for me is a given. I need an oil that can handle that. The Castrol proved to do as advertised, I have seen a few engines survive several minutes close to 200 deg CHT (Celsius, not Fahrenheit) without damage.

But it also helps that I can get it for less than €7/litre including free delivery (retail over here is €16~20).

airega1

My Feedback: (204)

Hello, I know this is an older thread but can you tell me where you got the baffles for the 90r3 that attach to the engine
Thank you
Frank Rega

ForcesR

Hello Frank, here is the link to where to purchase the baffles. https://ch-ignitions.com/product-cat...saito-baffles/

Roger

planenutzz

If you have access to a laser cutter I have a .dxf file however it is designed to fit in the TopRC FW-190 cowl.

Didier

Hello guys.

Does anybody know the part number of a membrane kit for carburetor FG90R3?
My engine seems not to get enough fuel anymore. Does not want to go to full power.

What is the best gap for new CM6 plugs? I found a lot different opinions

Thanks

BarracudaHockey

My Feedback: (11)

Plug gap is an exacto blade thickness

ForcesR

Carburetor gasket kit is K10-WYD for the FG90R3.

Didier

Thanks! Great tip! 👍

Didier

Thanks 😊

BarracudaHockey

My Feedback: (11)

It's a feeler gauge that 99.9 percent of us have handy

ccifra73

I am new owner of the FG-90r3 and I am having trouble (I think) with the running temperature of my Engine. I am running with Klotz TechniPlate 15to1 oil mixture with ethanol free 92 octane gas. Prop is 24x12. I ran about a gallon through the engine during break-in. After that I have set the low need at 4 turns and the high needle is at 4 turns as well. Changing the high needle to a lower (2.5 turns) or to 6-7 turns does not seem to affect temp. Anything richer on the low end and cylinder 3 will not come up to temperature. The engine is mounted to my Waco without a cowl. I am not getting temperatures nearly as low as what people are talking about in this thread. At about 3000 RPMs them cylinders are at about 120c (250F) and at 4000 RPM they get to be over 140c (285). With the current settings I max out at about 5800 RPM, but the temp will quickly climb to over 165c (330). I am measuring the temperature with Futaba temperature probes mounted behind the cylinders just below the exhaust. The engine is stock, and it runs really well, better if I lean out the low speed another 1/2 turn.

Is there anything I am doing wrong? Any ideas on how to achieve lower temperatures?

planenutzz

mine runs hot as well, from what I have read be careful leaning too much get it to where you think it is peaking then back off 1/8th of a turn, check temps as you tune. Many are tuning using temp as a guide.
I need to do more running with mine and play with pitch a little to get about 5200 on the ground. They are quite difficult to tun and as you say high speed needle does not seem to do anything. I'll set mine to factory setting and see.

RichardGee

My Feedback: (156)

My first question would be whether your temperature probes are reporting accurately? Do you have an Infared laser thermometer? This would also allow you to check cylinder/head temps at various locations to get an average, and of course compare those readings to what your Futaba sensors are seeing. I would start there.
Your fuel/oil, prop and needle settings are all OK and should not be contributing to the engine producing excessive heat.