modeltronics

My Feedback: (27)

Gary
If you are interested Randy Rich of Rich's brew will sell you synthetic oil (Ucon) at a good price. I just bought 4 gallons of it. My next batch of fuel will be half Ucon and half Super Techniplate to cut the castor content down. I have also bought nitro from him in the past.

the Wasp

My Feedback: (1)

if you are using 6v or higher or a really fast throttle servo, or both, try slowing the servo speed down in the TX settings or try a slower servo. specially at 6v or higher. I had a very good acrobatic pilot teach me that way-way back.

Jim

Jesse Open

Just around the corner

RoKit

No,, but like to know how they look inside.
The engine looses power now and then in the 5000-7000 rpm range.
Idles fine at 1800 and top at 9200 with a MAS 16x8

RoKit

Thanks,, That was one of the first things I experimented with.
I am using a 2S Lipo for the ignition and a Hobbywing 10ampUBEC for the plane.
Also reading evrerywhere on internet about Saito R3s original manifold design issues,
And nobody seem to have done a DIY modification ??

Glowgeek

Yeah, I know what you mean. I researched for hour upon hour trying to determine if an FA170R3 would be a good pairing for my P-47. During my searches for performance specs I ran into people having issues with the engine; the lower cylinders flooding out, top cylinder running firecracker hot etc. Even onboard glow or cdi wasn't helping much because of the poorly designed intake manifold.

So I started looking at CH and MMM gas conversions but the 20% loss in power output running gas vs. methanol killed my interest.

Then you came along, experiencing the same issues. I think Bert (1967Brutus) identified the issue as residual oil collecting in the intake tract. That sounds like what's happening to me as well. Let the engine idle long enough (low velocity air) and the intake pools oil in certain areas of the intake tract causing uneven cylinder temps.....rev it up and those oil pools get drawn in causing momentary uneven mixtures. At full throttle where intake velocities are highest the 170 runs fine.

A conversion to gas does help simply because the fuel mix contains less oil to begin with. The combination of running gas and using a modified intake manifold, CH or MMM, seems to yield a very good running engine.

I know, it seems a big secret as to how CH and MMM changed the intake manifold design. I'm sure it's not really a secret, it's just that no one has posted pics. No pics online at all, that I can find. All I can recommend is to purchase a manifold or complete gas conversion kit........and don't forget to post pics.

Can you elaborate on "looses power"?
Is it leaning out or going rich/excessive smoke?
Does it do the same running gas or methanol?

RoKit

Yes that is correct,,
There have been theories about the cause. Most probably oil and fuel "pooling".
I have tried various oil contents with methanol and gas as well,, the changes in running character are very small.
So my conclusion is that there is a "fundamental" design flaw playing with me.
As I understand it it´s not only the FA170R3,, but all the Saito R3´s. However the later year models, some have
been re-designed,, but still not perfect running.

I will absolutely not order a commercial "kit",,
I simply refuse to spend more money on on a engine supposed to be "high end".
But I love tinkering and will test my own solutions and share with the hobby community.
At this point I am mostly interested to compare and to know more about the theoretical impact
the manifold volume have on a Saito R3 and what to expect if the volume is small versus bigger,
and the velocity stagnation within the manifold..

I spent this winter renovation of my old lathe,, so now I can do some actual tests.
Attached is my principal sketch with approximate intake messures.





EDIT:

Can you elaborate on "looses power"?
When flying level for 20-30 seconds at about 3-4000rpm and try to go for 8-9000 rpm it hesitates a LOT at about 6-7000.

Is it leaning out or going rich/excessive smoke?
What seem to happen is that one cylinder flame out probably #2.
The smoke is coming later when it re-ignites.

Does it do the same running gas or methanol?
Yes, but less distinctive on gas., I use about 8-10% oil with gas and 18% with methanol

Glowgeek

I get that, I wouldn't want to spend more on it either.
I look forward to seeing the results of your tinkering Rob. Did you see the pic that Bert posted of his ASP 400 R5 with the swirled intake manifold passages over on the RCG Saito thread? That design seems to work quite well at reducing fuel pooling.

RoKit

Yes I have Bert´s picture, but that is way different from Saito R3 and I cant se how to replicate something like that.
I will post pictures of mine as soon as I am able to test the engine.
The weather here is cold , but spring is slowly coming so it will be ok within 2-3 weeks.

1200SportsterRider

Thankyou much.

the Wasp

My Feedback: (1)

have you tried to close the spark plugs gaps a bit? I remember back some 13, 15 years some one having this type problem around the same RPM and he found closing the plug gape a bit fixed his problem.

Jim

RoKit

Thank´s Jim.
No I have not, but tested several different plug brands. Not sure it might be related
since it is a typical behaviour regardless running on gas or methanol and glow & methanol/ 5-20% nitro..
But off course I will test that too //

Jesse Open

How well is this engine broken in?

I have had the 90, 120, 170 and a 325. Once broken in, they ran well.

RoKit

I know that many owners are happy with the performance.
There is also many who are unhappy. Maybe different people and applications
have different level of expectations.. I don´t know.

The later Saito design changes "sort of" confirms there is an issue.

My specific engine have had about 3 gallons 5-15% nitro-methanol.
I also tested about one gallon gas.

Jesse Open

Hard to say. I do a lot of running at part throttle but not tolerating unreliablebor delayed transition
No complaints here with methanol fuel glow nor spark ignition.

Can't comment regarding gaspoline fuels.
My engines were run solely on methanol blends.

RoKit

The first word I think of when reading is,, Congaratulations !! :-)

Jesse Open

Probably got a bit lucky as my first one was probably the easiest. It was the FA-90 R3 and was pretty well broken in when I inherited it. Flown on an easy to fly Ford Flivver.
The next 120 R3 was also used, just a good running engine . The 170 R3 was new and had a Keleo. That one would not settle down until after the second gallon.

My fuel uses only 14% total oil and 14% nitromethane.


I cannot say regarding gasoline but generally gasoline mixture settings are more critical . Methanol settings a bit more tolerant.


Being a non-fuel,it would seem oil migrations downstream of the carb should not be that upsetting. Fuel vaporization probably yes.
And gasoline has the postive edge there, especially when temps drop.

Just speculation however.

1200SportsterRider

Keep those temperature measuring devices away from it and it will run just fine. They only lead you to fix what ain't broke.

Jesse Open

Plus one on that!

RoKit

I wish it was that easy

But when you se and hear a "non response" from the engine in flight when you need it the most..
Well that engine is grounded in my book.

Hyjinx

Brilliant statement.

Jesse Open

Yessir, something usually learned very early on, at least should be.

RoKit

Not sure what you mean,,, you are welcome to explain.

the Wasp

My Feedback: (1)

you know I have 2 friends that had 2 st gassers of different sizes, different brands, and USA and China made. I believe there was 3 engines, on the ground the engines ran great, in the air they ran great then they stall/stop running. these 2 guys tried everything to fix their engines, different carbs, different plugs, different ignitions. different casket, different everything. one guy tried 3 different carbs and 3 different ignitions. that one was a BME 105 twin with a lot of time on it.

I felt I knew what the problem was. there was only 1 thing left to go wrong. today I still believe it was the Bearing Seals, once the seals heated up good in flight they started to leak air. but the engines were sold so we will never know if I was correct or not.. what else could it have been?

Jim

the Wasp

My Feedback: (1)

remember, if you are into RC and you are not flying. you are only going around in cyricles. unless you are going 170MPH and faster.

Jim