Are there any 4 - stroke engines new not old that can run without nitro?
I Know that Laser engines run without nitro but i am interesting for 0.52 and laser engines does not make one.
In case i wiLl buy an OS 52FS and run it without nitro it will be running reliable or not?

Hello Johnny; I have a Laser 100 that I run on 0%, so I always have some 0% around. I have used that same 0% on my Enya 46's and just about all of my Saito's 30 to 150. It works just fine on all of them. Maybe the idle isn't quite as reliable, and maybe I lose 2 or 3 hundred revs off the top, but if it's the only fuel I brought with me, it works just fine.

I haven't tried it in an OS four stroke, since I don't have one in a plane right now, but I do remember using 0% in one of my OS 90 four strokes, and it worked just fine there.

I would say, buy some ane try it; you're not going to harm anything as long as you don't try to run too lean. I'm pretty sure you'll be pleased with the way it'll run.

Without nitro, most 4 cycles idle lousy.

I think once it's run in it should be ok, until then you will have to run it with a higher idle. Use a lower pitch prop so you can land. What type of plane are you going to install it on? You can probably run a APC 13X4W. My HP 49 spins one fine on 5%.

If you want a good idle then you are going to need nitro. Probably around 10%.

The early Saito 65s and 80s seemed to run OK with low nitro. Any engine intended for the American market will be compressed to handle 20-30% nitro, the result is an engine that really needs a little nitro to run very well at all. By all means try some no nitro fuel, it may work acceptably well for you.

American market engines are not designed to run on 20 to 30% nitro. Very few need that YS being probably the only one. The rest all run just fine on 5 to 15% and 10% is what I run ALL my glow engines on.

Early Saitos had very high compression (I read somewhere that it was around 14:1) so they could use zero nitro. This didn't suit the American market so they were redesigned with lower compressions. One of our club members machines down the crankcase on his later Saitos to sit the cylinder lower down to get 13.5:1 and then uses zero nitro.

Not true. I have two saito 30's, three 45's, three 80 Twins, a 40, a 90 twin, and a couple of 120's and they all run great on 10% nitro. They are not high compression ratio engines and were all made before 1984. Saito never made anything that was 14 to 1. All my early Saitos were purchased in Japan when I was stationed there and the Japanese use low nitro fuel, 5 to 10% just like I use in the US.

The original 65 and 80 had compression so high that was and still is "off the scale". Lower compression and a little nitro makes engines so much more user freindly, plus it allows the power hungry to tip the nitro can without throwing props off as much.

I sold dozens of 65's when I worked for Hobby Shack and they didn't have compression higher than any others. I ran my 65 on Hobby Shack's White Lightning fuel which was 10% nitro and 20% castor and it ran just fine. Had no complaints from customers about high comprssion and not running on 15% nitro. How do these rumors get started?

Go and find the RCM review for the 65 from 1986. Saito FA65 compression ratio 12.7:1. This is very high by industry standards then and now. This may not cause any problems using fuel that the mfg intended, they never thought people would be feeding them 30% nitro. Later the compression was lowered.

They didn't think anyone would be using 30% nitro because the instructions said not to. They clearly stated to use 10 to 15%. There is no four cycle engine that needs 30% nitro. Even the YS which likes high nitro only needs 20% and that's why powermaster makes YS20/20 fuel. The high nitro use didn't start until the last ten years or so and that was certainly well after the 65 came out.

It's not the manufacturers fault that people can't follow instructions. In all the years I worked for Hobby Shack I never heard anyone having any problem with Saito engines because of high compression ratio and I sure never saw any manifestations at any of the local flying fields. The amount of fuel with more than 15% nitro sold at the San Diego Hobby Shack was negligible. I sure don't know who was using 30%. We didn't even carry fuel with that much nitro except for Cox fuel. YS20/20 didn't come out until the last few years or so.

Just exactly which month in 1986 was this RCM review?

When was the compression of the 65 and 80 lowered, and how can we tell the high compression from low? (Short of turning it over... I'm thinking more about how to spot the high comp engines in the used market.)

I've read that OS Suprass 4 strokes have a higher cmpression ratio that Saito's and hence run better on lower nitro. I don't have the personal experience to know one way or ther other, but's it is an interesting difference if valid, and might sway ones purchasing decisions.

Hello, Johnny. I see you are in Athens, Ispent time there in the USN. You are near or at sea level, so nitro aint really needed. I live at 3,000' above S/L, and use 10% all the time. ASP/MAGNUM and my RCV CD58 love it. You should try 0% and see how it runs for you. The higher the nitro level, shorter the engine life! Happy Tuning.

Altitude has almost nothing to do with the amount of nitromethane needed. I live AT sea level and use 10% in all my glow engines. Nitro helps the idle in 4 cycle engines.

The Laser 70 may be a bit more powerful than a 52 Surpass; but not by much. The rule of thumb with Lasers is a given displacement is equal in power to the next LOWER displacement of one of the higher-compression Japanese engines.

This is what I was told, anyway. And my several years of experience with a Laser 150 has borne it out; my Laser 150 puts out about the same power as a Jap 1.20 four stroke.

Mine was broken-in with, and has been fed a steady diet of, 15% nitro fuel. Neil Tidey of Laser told me that the nitro wouldn't hurt anything, and would give a slightly smoother, lower rpm idle; but his engines are designed to run on no nitro and do so just fine.

Mine, on 15% fuel, has been without question the most reliable glow engine I've ever owned. I have to adjust the mixture twice a year, when our season changes (we have two; hot, and not quite so hot ).

Kweasle,

I just got down from my attic with the bound volumes of RCM from 1986. There is no engine review of a saito 65 in any of them. Just which month was this review in???

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Except Enya and Laser, or pre 85 OS, or pre early YS90AC, or, or ,or.....<G>

LOUGHBD Now that heli's are more popular and special fuel is stocked for them. Flyers are grabbing the 30% trying to make their 4 stroke perform like a YS super charged. If YS had'nt started the 20-20 craze the bulk of engines would still be on 10-15%. I personally think the extra oil in 30% HELI makes the nitro less potent and a 20-20 YS blend would be about the same. Look Americans invented musle cars but we limited ourselfs to go in a straight line.

Heli flyers have been using a lot of 30% for MANY years; not just recently. There are two main reasons: because it does indeed make an engine perform better, on both high and low ends. More power, better idle and easier mixture adjustment. The other reason has to do with lemmings and being cool, but we won't go there... And all of this was a very long time before YS engines became even close to being commonplace in helicopters.

I used it for a while. It really makes a difference, both in engine performance and the thickness of your wallet. That's why I stopped using it; the cost was getting totally out of the box.

As to the extra oil diluting the "power" of the extra nitro, well... there are several schools of thought on that. Without doubt, the most vicious thread wars I have ever seen in fifteen years of perusing these hobby boards have been all about fuel, and the differences, real or imagined, between a certain few leading brands. All of which is rather retarded... when you think about it, the variables involved make an objective comparison FOR EVERYBODY impossible. What works good in your machine and climate may not do so well in mine, etc., etc. But it was great entertainment...

Anyway... I went back to 15%, and run that in everything from a .12 buggy engine to the Laser 150. In my experience, most any quality engine will run on most any quality fuel, assuming all you're looking for is reliable running.

If you're determined to be the next Chip Hyde, Curtis Youngblood, etc., or simply must have the baddest, most powerful performance, etc., etc., then by all means cough up the dust for 30% nitro. The fuel mongers will love you for it...

Use nitro for performance - use an on-board glow driver for idle.

On-board glow driver = weight, weight = bad.

How would one increase the compression in a modern 4-stroke like the newer Saitos (1.25, 1.00, .82a etc.) if one wanted to try to tune for more power? The engines now are made to run with some high nitro, but you could tweak the compression to be as high as possible without detonation or preignition your specific nitro level.

my sc 91 fs runs just great on 0 %. I have removed one headshim though.

Magnum 120 fs will run on 0% without a problem. I tried this myself and it does work. I had to do a bunch of tuning and I lost about 300 rpm compared to 10%.