OS FS26S-C 4-stroke development
 

Hi all, I don't know how many of you are following the 4stroke thread, but I thought I would start my own thread regarding the development of the tiny OS .26 4stroke engine.

So far I have only scratched the surface of what I think this little engine is capable of.

Let me know what you think of the idea and any suggestions are always welcome.

I will keep posting results as testing progresses.

So far I have only tested the engine for base tests and compared it to a .15 thundertiger sport engine (std).

This dyno comparison is on the '2stroke vs. 4stroke' thread.

I designed my first attempt at creating a new header and silencer for this engine and will post dyno runs below.

the green run is the std OS .26 4stroke straight out of the box, broken in, and tested with a available short header and std silencer.

the blue run is the same OS .26 4stroke, with bushings replaced with bearings for camshaft support, and my header and silencer added.

I was very suprised with the results that the header and silencer made.
peak rpm was increased from 18,500 to 24,500
peak hp was increased from .38 to .54
peak tq showed no increase but tq range broadened substancially.

Much more to come...

BK

Awesome work, Keep it coming:D

Wow that's lot of jump from the stock HP.
is it the pipe or the bearing?
Can this engine fit in 1/10?

The change was definitely the pipe. The bearings for the cam only eliminate parasitic losses from bushing drag. The bearings might increase revs slightly but I didn't show an increase when I tested the bearing change by itself.

The difference with the pipe change was incredible. Really increased response also.

I have a few more pipe ideas to try before I settle on one.

BK

how about a picture of the stock pipe vs your new pipe and do you have any results of checking of just running a straight header.

More progress!!!
 

For those interested,

I have made a bit of progress today on the OS FS-26S-C development project. I made a new intake manifold and fitted a 2 needle carb from a 2 stroke engine I had lying around. The new carb has a bore 1mm larger than the std os carb.

The gains were substantial;
peak hp .54-->.64
peak tq .16-->.18
peak rpm 24,800-->26,500

Granted we lost a little bit of power on the front side, but I think with a better quality carb that has more precise metering we can get that back easily.

Dyno run explaination:
Light blue run is std OS FS-26S-C
Green run is the run from my previous post.(New pipe and silencer)
Dark Blue run is the latest run.(New pipe and silencer, and new manifold and carb)

I havn't even started messing with the compression or the ports yet!!

Looks like we might have a winner here after all!!

I'll post more on this project as I have time to mess with it. I gotta get some real work done!!

BK

Good stuff. Can't wait to see how much more power you can squeeze out of the engine. Looks like I might be putting my OS .26 back in my FW04 soon.

OS FS-26S-C VerII
 

hello all,
I just wanted to see if anybody has heard any news if OS will release there OS FS-26S-C VerII in the states. They have them showing on their Japanese website but not on their English website. Maybe someone from OS, or a hobbyshop with some inside info can help us out! I really hope to see these engines in the US soon!

Check back soon to see dyno graphs of my latest improvements!

BK

How about some pictures of the motor, pipe and carburator. instead of these graphs.

Pictures...
 

I will show pictures of all modified components when development is finished and the parts are ready for sale. In the mean time I will try and post a few seek peeks of the engine on the dyno in the next few days.

BK

I'd like to see a picture of the Dyno.

Where did you get it? What do they cost? How realistic are their readings?

But interested in pics of the engine, too.

Dyno answers
 

Red,
If you would like information on the dyno please visit my web site. http://www.nitrodynesystems.com . I originally designed the dyno to test some exhaust systems I am working on. I had so much interest I decided to manufacture them for sale. The price for a complete dyno is $4995.00. I realize that is not cheap but the cost of components and labor involved in machining dictates such a price. (this price does NOT include laptop computer).

As far as accuracy and repeatability is concerned, I believe this dyno to be VERY accurate, but more importantly is is extremly repeatable. I can repeat runs within .01 hp. It also has real time weatherstation capabilities, for correction factors.

One thing I have found is that most manufacturers that publish hp figures are full of c*&p. The best .12 engine I have tested so far is .78 hp. Which in my opinion makes sense, 1.6 hp from .12ci simply is not possible!! If you compared these claims to a top fuel dragster making 5000 hp, they make 10 hp per cubic inch. If you were to compare the claims of manufacturers, they claim 13.3 hp per cubic inch. Does that make sense?

BK

I was lucky to be invited by Brian to test couple of engines. I can tell you that device is realy cool tool.
We were running my engine on it and we did repeated runs many times and it has never fail-always, if I don't change setting on engine, was mshowing the same numbers in HP, torq and RPM.
Great tool for anybody who is looking for max power from engines. Specialy good for modifiers who is doing their work from the sky, so they can check how one or other type of modding affecting performance.
I hope I will be able to run my P/S sets on it to compare to original. I know how it is better on track, but will be very interesting to see in #s
Edward

Hey, BK

Can you tell me what engine it is that makes .78 HP?
You can PM me if you can't tell...
I won't tell anyone....

OS FS-26S-C VerII availability...
 

I spoke to OS today and I was informed that OS US was not planning to import the OS FS-26S-C Ver II to the states. The reason was that due to lack of sales of the previous version they don't feel they could sell enough units to warrant stocking the engine.

I discussed what I was working on and that I feel that the engine may be competitive with some more development, we just need to get race organizers to allow the engine to race with the .12 two strokes.

Let me know what you guys think. If the OS FS-26S-C Ver II was competitive with the two strokes but got way better fuel mileage, and had way more torque on bottom would you consider racing it? What would you be willing to spend to make it competitive? I realize that competitive .12 two strokes can range between $350-$650. What would be the limit you were willing to spend to race the four stroke?

Please give me some input on what route to take, should I push to get this engine in the us or should I scrap the four stroke project?

You think you can price it around $250?
I Think that is reasonable price....

Re: OS FS-26S-C VerII availability...
 

I doubt that this engine will be slow. With a little modifying this new 4 stroke version will be a lot faster than a 2 stroke. I would only pay $150 for when I have the money. In japan this engine is the option package for the Kyosho V one RRR.

I doubt they would sell any since current rules only allow 2-stroke engines. If you were to get it as fast as current JP's, Rex's and Sirio's, you would hold an unfair advantage because of fuel consumption.

I disagree, I think they should be pretty close performance wise. Yes the four stroke might get slightly better miliage but they also will be a bit heavier than the two strokes. And if they do get slightly better fuel miliage that may be the reason for some drivers to change. The four strokes will always have some drawbacks compared to two strokes, like engine rpm.

Are you completly apposed to alowing four strokes to compete in 1/10 touring classes? If so is fuel consumption the only reason?

BK

I like the idea..... four strokers sound cool and if they can be made competive I would run one. If too many people whine they could always have a "4 stroke" class:nod:

No, I'm not opposed to four strokes. I'm just offering a view from ROAR's perspective. Change is good but very hard. As a matter of fact, I'm planning to get the four stroke conversion for my Kyosho.

i'm sure they sound lots quieter, and quieter is always better for tracks maintaining presense and new tracks opening in better places. It appears EFRA is always doing things to get them quieter, so Its possible that they may be open to 4 stroke developement.

Also 2 stroke gas engines will be illegal in a few years, who knows if they start to look at the hobby industry.

As far as gearing goes, its possible to change internal drive ratios on belt cars with diff pulley sets.

Makes want to put my OS 40 4stroke in a 1/8 on road! Wonder if I could get it geared tall enough?

id go a OS 52 4 stroke....that thing would be sweet

Latest developments
 

Hello all, I just thought I'd report my latest findings with this little engine. I haven't had much time lately to mess with this engine lately, but today I was able to make a few runs. Basicly I just made a few base line runs and then tried a new glow plug with a different temp range. I have included a copy of the latest dyno run.

The green run is the engine with the same modified parts as before. (Header, megaphone, 6mm 2 needle carb, intake manifold for new carb, and ball bearings on the camshaft instesd of brass bushings).

The blue run is the latest development with RE glow plug instead of type F. (The RE glow plug is std for OS Wankle or Rotary engine. It has a slightly cooler glow temp).

The increase wasn't huge but I think it was signficant.
Peak HP .64 --> .67
Peak TQ .18 --> .19
Peak rpm stayed the same.

Note: torque really picked up substancially all the way up the front side of the curve.

More to come! I am in the middle of designing the CNC head so it will be interesting to see what difference that will make. I am going to include Ti valves and Beryllium bronze valve seats with the new head. Also I have several new exhaust ideas to try!

Jamie; I wouldn't mess with the .52, it is not designed to rev like the FS-26S-C and FS-40S-C. I think the most rpm you would see out of the FS .52 would be around 13,000 VS 27,000 with the S-C versions.

Are you going to try putting that motor in the rules would be allowable if you just talk to ROAR. Are you a ROAR member? If so you can make your posts on rc-racing.com conferences and go to ROAR conference. Now is the time because the ROAR excom is meeting early october.

I think it would be interesting to find a equivalent for 1/8th scale cars, just need to work with the manufacturer on a different pulley set for gearing lower internal ratio. Is there an equivalent motor available?

WOW, those performance figures rival an OS .12 CV-R!!! (.66hp)

Man i am so loving the 4 stroke development....who knows whats next....



Dude, howabout an RB innovations supercharger?? One of them has got to make a difference in a 4 stroke motor....

good one mr shirlock, if you read what he said about his dyno is that it reads ITS own values, which are more realistic then 1.6hp .12's The most powerfull race motor that he has tested on his dyno has pushes .78hp. That menas that .67 hp out of a 4-stroke with insane torque is very close, considering the stock motor puts out .38 on his dyno.

WTF?? , an OS .12 is "quoted at 1.0hp, but actually puts out .66, which is the same topend that the OS 4 stroke has....

you dont understand, the dyno that RCCA uses and the one that MX wrench build are two different machines. The .66 number that you probably got from RCCA or RC Nitro, is not in any way shape or form compariable to MX's dyno. On his it probably would only pull .45hp at best.

Its apples to oranges. His dyno uses existing software from go-kart dyno's (I think thats where its from). The other mag's dyno has custom made sotware, that could calculate hp differently or have a bug, or just be pushed numbers.

I apologise if your getting the .66 number from his dyno, and Im in error, but I have yet to see him post any dyno numbers from a CVR.

Dyno numbers
 

Guys, let me try to clear this up...

My dyno is an inertia accelerometer or inertia dyno. When I designed it I used industry proven formulas to calculate the flywheels moment of inertia. These formulas can calculate how much torque is required to accelerate any given inertia to a specified speed in a specified time. I used actual torque output figures from current engines to determine the approximate flywheel inertia and therefore flywheel size. I have verified my flywheel moment of inertia using online industry inertia calculators. My flywheel is 99.9% accurate to test engines of this size. The numbers I calculated suggested it should take 10 seconds to accelerate my flywheel inertia to 40,000 applying .15 ft. lbs. average torque. Turns out my dyno takes 10.3 seconds. The dyno is 99.9% accurate as long as the software knows EXACTLY how much inertia I am accelerating. This is very important to accuracy.

As far as RCCA's so called dyno is concerned I hear the dyno they had made never worked properly and they are back to using airplane props to determine TQ output.

Well, in my opinion that doesn't work. Airplane propellers aren't designed to run in a stationary position. The number of variables is to great. First, propellers cut thru air, the path they take is sort of like the threads of a bolt. Spiraling thru the air, cuting thru and forcing itself forward at the rate of it's pitch. If you hold a prop stationary and raise it's rpm, it quickly overcomes the rate of air flow it can draw thru it's blades and succombs to prop wash. While in motion, each prop blade always encounters clean air. An example of propwash is similar to a jetboats impeller cavitating. In the boats example cavitation occurs when the impeller sucks air and cannot force water in or out. In the airplane propellers case each blade of the prop is stuck in the wash of the previous blade and it's effect to push air is reduced dramatically.

Secondly, any propellers effectiveness is dependent on the relative air's density, or it's concentration of molocules. Thin air is much easier to compress than thick air. Barometric air pressure is always changing. This is similar to your car running at sea level and your car running at 5000 ft. There is a huge difference in the amount of compression at sea level and at 5000 ft.

There are formulas to calculate how much tq is required to turn a given propeller at a given rpm, however this requires the propeller to be turning itself thru clean unspoiled air in a cork screw pattern. By holding the propeller from moving thru the air all these formulas go straight out the window, therefore rendering any accurate measurement of power impossible. An engine can turn much higher rpm with a prop while stationary, but this rpm always drops when the prop is properly loaded by traveling forward thru the air. This is why I believe the majority of measured HP figures printed by RCCA are inaccurate.

Unless there are ways to account for prop wash and air density's effects on propellers, I personally would never put any stock in the results from these types of tests.

I hope this answered any doubts people may have to the accuracy of my dyno's figures.

Sorry for the long post.

JPHRacer: my dyno uses software originally developed to test full size v-8 race engines. Since then the same software has been adapted to test many different size engines, from r/c glow engines, gas r/c boat engines, go-cart engines, motorcycle engines and even 1500 hp alcohol fueled dragster engines. This software has proven itself time and time again. Thanks for helping to explain the differences.


BK

So how is Novarossi claiming their HP figures? They say 1.5 - 1.6 for their latest 3p -5p .12 engines. I like how your doing this 4 stroke testing, but I just wish their was an industry standard of HP values being used out there so as consumers we arnen't biffed. There should be one source all manufacturers get their hp numbers and that should be through someone 3rd party like you. Imagine if we as consumers got the industry to use a 3rd party dyno checker to get their numbers, kind of like a ROAR approved engine list. Would you be willing to perform this service (paid of course by manufactures)?

Tomkelly,
Hopefully this is what will happen soon. I am not planning on testing for all manufacturers, at least not at this time, but, I am offering my dyno's for sale to all manufacturers, or anyone else who want's one for that matter. I hope my dyno WILL become the industry standard and we can get some consistency from all parties.

So far I have quite a few manufacturers of engines already awaiting their dyno's and even more interested and awaiting a demonstration that will take place in October. Hopefully all will follow suit and we will get some consistency.

However I am not opposed to doing testing for manufacturers from time to time.

BK

Progress report...
 

Hello all,
I just recieved a OS FS-26S-C Ver II today from OS. I am going to dyno it this weekend. I will post results when I am finished. No major differences, except carb and valve cover. Rocker arms look a little different but as far as I can tell they are the same ratio. Maybe a different material.

I also just finished a pair of Titanium valves and a lower cyl for my other test 26S-C, I will test them also and post results.

Till then,

BK

mxwrench,
So you happen to have any pictures of that new .26?
How did the carb and valve cover change?
The engine is still available but only in Japan is that right?

Let us know how much faster the new .26 is over the old .26. Not sure whether I should buy the new one to replace my current engine.

Nr1Drillah, there is a pic of it in the RCCA forums.

Thanks, but where is that?
You wouldn't happen to have a link now would you?

Thanks, Drillah

Thanks Dan.

Since this engine likes to get REALLY hot, I wonder why they did not make the new one with bigger fins or even put some fins on the valve cover.

:confused:

OS FS-26S-C VerII
 

Hey guys, here are a few photos of the new Ver II I recently aquired. I checked this new engine over very carefully and I noted the following changes:

New carb with single needle w/5mm bore and new type manifold --> up from 4.6mm previous

New valve cover --> not sure why, maybe for logo placement

New design rocker arms --> slightly larger arm and much better material. Probably to prevent flexing.

Slightly thinner piston skirt thickness --> lighter weight

A few other cosmetic changes --> new machining on crankcase, new backplate shape

Sorry, no increased lift or duration of cam shaft

Here is a photo of the new engine next to the old one...


BK