CLBetten

My Feedback: (16)

I have many hours running my Saito .30 on 20% nitro. It runs, flies best and tunes easiest with a 9X6 prop. and always has. Today I put the first five or so flights on my OS .30 using 10% nitro. I broke it in and first flew it with a 9x6. It was (by ear) turning higher RPM than I like and being touchy on the needle. I switched to a 10x6 and it loved it. I wouldn't expect the OS to out power the Saito. Do you think the higher nitro may increase RPM but reduce torque causing the Saito to want a smaller prop. Next time I fly the Saito I'm going to try lower nitro and a larger prop. I would expect more nitro to translate to more torque and increased top end both? Opinions anyone?

jeffie8696

Engines are designed differently and may have cam profiles that enhance high rpm power or low along with port size valve size etc. Experimenting is the key to getting the most from your engine.

1QwkSport2.5r

Getting and using a tach will confirm or deny if one engine is running faster than the other.

Sport_Pilot

Nitro increase's the cylinder pressure, which increases torque. The higher RPM is because the prop will only have so much torque resistance at a specific RPM and the torque required goes up with RPM. If the torque is not going up with more nitro, then you need a hotter plug. With lower nitro you may need a hotter plug or bigger prop to advance the timing. BTW the nitro itself burns slower than methanol so it increase the required timing advance. But the nitro also is more likely to detonate which requries a colder plug. So for mid to high compression engines you may have to use a larger prop and cold plug to get the ideal timing. The timing advance can be large the drag racers use about 60 degrees for 90% nitro.

CLBetten

My Feedback: (16)

I expected the two engines to have very similar characteristics. I'll take my tach and a couple different props and glow plugs and do a more scientific test.

jeffie8696

That's the stuff

Hobbsy

My Feedback: (102)

Cliff, here are my Saito .30 numbers using a Graupner 10x5.5 and 15% WildCat. I am receiving four gallons of 10% WildCat 2/4 today which is 18% all synthetic. I can get some numbers with that tomorrow.

CLBetten

My Feedback: (16)

I wouldn't expect you to use all synthetic oil? What's your elevation Hobbsy?

Hobbsy

My Feedback: (102)

We are just about sea level here, I've used the full synthetic Wildcat before with great success. I am a nut about using ARO after each engine use.

MinnSpin

My Feedback: (40)

If you haven't already, you might try Marvel Mystery Oil for your ARO as it helps dispense moisture from collecting on things like carb sleeves, especially in corners where tarnish grabs hold not to mention the way in which it lubricates valves, stems, lifters and pistons.

CafeenMan

What does the OS manual say to use?

1QwkSport2.5r

The last engine I saw posted about that was run "per the manual" tossed the rod through the crankcase...

Hobbsy

My Feedback: (102)

The new fuel came about an hour ago, I'm good to go for a while. I have Sig castor to add if the mood strikes.

CLBetten

My Feedback: (16)

I put a battery in my old tach I haven't used for a long time. I wanted to get a fairly close test for calibration. Shouldn't a regular household light bulb measure 6000 RPM?

1QwkSport2.5r

3600rpm is what the tach should read when pointed at an AC light. 60Hz.

CLBetten

My Feedback: (16)

Yup found that. I'm relieved. I love my old tach. Sadly the fellow that built it passed away.

Hobbsy

My Feedback: (102)

Cliff, I did find where my little .30 was not the same as it's larger bretheren, it wouldn't idle slower than about 2,800 on the 5% fuel.

CLBetten

My Feedback: (16)

Here are my results. I fly at about 4300'. Both my fuels are VP Powermaster with 18% oil blend. I didn't run the OS on 20%. The instructions say no more than 15%. I literally used the same props and hubs on both engines. They are an APC 9X6 and a Graupner Super 10X6. I tuned each engine as I would have it to fly. The Saito on 20%: 9" 12,200, 10" 10,050. Saito on 10%: 9" 12,050, 10" 10,000. OS on 10%: 9" 13,100 10" 11,000. The Saito required the needle be open more on 10% it also obviously ejected more oil from the vent. As for the Saito numbers the 20% didn't yield a whole lot more power on either prop. Although I pay the same price for 10 and 20%. I will use the 10% just for the difference in oiling and hopefully increased longevity due to it. The comparison of the 9" props shows the OS well ahead while the 10" only gives the OS a slight advantage. In the end I'm buying only 10% fuel and I'm going to try flying the Saito on the 10X6 again. The idle speeds were all in the 3200 RPM range. I didn't spend much time there and didn't change the idle needles at all. I forgot to mention I run OS F plugs in both engines.*

Hobbsy

My Feedback: (102)

Cliff, just for kicks, when flying my LT 25 in longer grass I run a Graupner 10.5x5 and it quite literally yanks the plane of the ground like a crane was lifting it. The 10x5.5 requires some distance to get off the ground.

CafeenMan

Interesting. I've never had a problem with an OS engine run per the instructions. Their instructions are always very conservative and won't give you nearly the output the engine is capable of.

CafeenMan

I bought a case of that stuff and most of my engines hate it. I have to mix it 50/50 with other fuel to get rid of it.

jeffie8696

I tried using some higher nitro in my OS26Surpass(because its a tiny little four stroke) initially but after the break in it told me it wasn't happy on it and I switched to 15% and it has been very happy ever since. It hauls around my 3 pound SIG 4Star20 wonderfully.

earlwb

The two OS .26 Surpass engines I have on my Twinstar are sporting 9x7 propellers. I have been using 5% glow fuel in the engines and they have been running just fine for me like that.

I put two Saito FA-40a engines on my F82 Twin Mustang and those two engines are awesome for the amount of power that they have. They fit in the same place that the smaller FA 30 engines go and they are about the same size too.

1QwkSport2.5r

Of course it is quite possible the engine didn't last more than 12 flights due to user error and it was a 1.20 4-stroke, but still... I take what the manual says with a grain of salt. The manuals are rarely written by the actual people that designed the engine. I don't want this to end up being a thread hijack, so I'll leave it with this - this is the thread I am referring to: http://www.rcuniverse.com/forum/ques...-destryed.html

On average, my old design 4-strokes only gained about 200rpm going from 5% nitro to 10% nitro.

flycatch

My Feedback: (26)

I run nothing but Saito and have always used a blend of YS 20/20 sold by Power Master. When I got into this hobby I believed all fuels were the same but that is not true.