zimzalahbim

My Feedback: (8)

i have not seen any 4-strokes on any websites. i know that 2 strokes are the king of power, but are there no 4-strokes for 1/8scale buggies?

Mike Abrams

The only 4-stroke engines are for helicopters & airplanes, a 1\8 buggy couldn't handle the power of those engines.

zimzalahbim

My Feedback: (8)

well from what i understand, the 4-stroke would need twice the displacement as the 2-strokes we use to deliver the same power, i.e. GP motorcycles recently shifted from 500cc 2-strokes to 1000cc 4-strokes, and motocross bikes are also making the shift. 2-stroke=250cc, 4-stroke=450cc. so we would need an engine with twice the displacement, but the cooling head is much smaller on the 4-strokes that i have seen. it would be cool to have low end grunt, and unmuffled rumble. i love the 2-stroke sound, and 40,000 rpm's, but having a pushrod 4-stroke on an RC car!

neil.jb

2 strokes are much more powerful than their 4 stroke equivelents although 4 strokes tend to be more fuel efficient because they tend to rev a lot lower producing more torque

mxwrench

OS FS-26S-C for 1/10 scale and OS FS-40S-C for 1/8 scale. The motors definitly are not as powerful in stock form as their 2 stroke counterparts, .12 for .26 4stroke and .21 for .40 4stroke. I have recently begun a development project with the OS 26 4stroke and so far things look good. Here is a dyno run with some of my modifications.

Light blue is std OS FS-26S-C completely stock, broken in and run with std os pipe and silencer.
Green run is OS FS-26S-C with my first attempt header and megaphone
Dark Blue run is OS FS-26S-C with header, megaphone, and new intake for 6mm carb.

Very impressive gains so far,
hp .38-->.64
TQ .14-->.18
Peak rpm 20,100-->27,600

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

Just for comparison the BEST Italian rear exhaust race engine in the .12 size I have tested so far only produces .78hp@33,000 rpm, and a typical .15 sport engine makes .5hp@26,000. This is true measured hp, not some fabricated manufacturers estimate.

BK
www.nitrodynesystems.com

zimzalahbim

My Feedback: (8)

in terms of size, is the .40 4-stroke much bigger than a .21 2-stroke? does it weigh much more, and is the overall height something to consider? are you manufacturing your own pipes and silencers? and neil, the 4-stroke is much more fuel efficient because there is an intake and exhaust valve to manage fuel in/out of the cylinder.

mxwrench

I'm not sure of the actual dimensions of the .40 4 stroke. Check out the OS web site and compare OS FS-40S-C to a VZ-B21R. The 4 stroke is more fuel efficient because there are half as many intake cycles than a two stroke, and they usually rev a bit lower. However the intake lasts longer on a 4 stroke so the difference is less than half. Maybe around 35% better fuel economy. These OS engines have a ton of valve overlap, (Where both intake and exhaust valves are open at the same time), this makes them very inefficient, similar to a two stroke. This is why they respond so well to loop scavenging (Pipe reflected sound wave and back pressure forcing unburned fuel back into ex-port).

And yes Dirtbug, I do plan on offering Headers, and pipes for these 4 stroke engines once I get a little more development done.
I also plan to market the special intake manifolds as well as CNC heads with better flow, more compression, and much better cooling ability.

I would really love to see these 4 stroke engines become as popular here in the states as they are in Japan.

BK

www.nitrodynesystems.com

zimzalahbim

My Feedback: (8)

so how much do you think a worked mill will cost after you finish with it? i did a search, only found 1 place with the .40 engine, and it was around $250.

HighSierra

My Feedback: (2)

sad that tower no longer sells the .26 and I've never herd of the .40

I'd like to drop the os .26 into my Nitro blizzard (my only land based RC) I'll take 4-stroke sound and torque over 2-stroke whine anyday!

mxwrench

OS is about to release a new version of the OS FS-26S-C. It will be the FS-26S-C ver II. They are already available in Japan. Hopefully Tower will sell the new version. Check out the OS website to see specs. www.os-engines.co.jp Use AltaVista Bablefish to translate Japanese to English. Lots of hype but not much has changed. New carb and new valve cover. Thats it.

As for the modified .26, I haven't given it much thought. I will probably offer the pipe and silencer for $70.00 ,intake manifold for $35.00, Titanium valves for $50.00 and the Piston assy for $40.00. I'm not sure how much I will charge for the new head assy. Depends on how much it takes to develop and produce. I have yet to make the prototype head but I plan to relocate the intake port to the side for more direct intake path, and most touring cars need the carb to the side anyway. I really don't want to have a intake manifold with a 90 degree bend in it. The new head and valve cover are going to have MUCH larger heatsink fins for better cooling, a new combustion chamber shape, and maybe use a turbo type plug. I might try Titanium rocker arms but we'll have to see how it goes.

Hopefully we can all get the rules changed to allow these small four strokes to run in the same class as the two strokes. Maybe more manufacturers would offer 1/10 scale conversion kits for their top line race cars.

BK
www.nitrodynesystems.com

zimzalahbim

My Feedback: (8)

how does the crank and everything get lubed? i saw on the exploded view that the piston has a ring, and the carb is righth on top of the head.

mxwrench

Dirt bug, the crank and bearings get lubed via blow by, or fuel leaking past the ring. The camshaft is basically lubed by the assembly grease that is put in when it is assembled. Also the cam gets some of the blow by. The rocker arms get lubrication via the pushrod tubes. I didn't think it would work well but theres always plenty of oil under the valve cover when I take it off!

BK
www.nitrodynesystems.com

zimzalahbim

My Feedback: (8)

what material is the sleeve and piston made of? i have been reading the "ultimate nitro engine guide" and there is some discussion about large cc nitro engines using rings. if the performance of your engine enhancements, and the overall price rivaled something like a WS7II, i would definately make the switch. also, the nitro guide mentioned the use of a 2-speed tranny for 4-stroke use, so does that factor into your plan, or do you plan on will your mill have enough umph to hang?

HighSierra

My Feedback: (2)

2 speed trans makes sense.....considering the engine is only going to safely get up to 12,000 RPM.... I bet the valeves start floating at 13-14k

mxwrench

HighSierra, The model engine we are talking about here is the OS FS-26S-C car engine. It has a useable range of 3,000-22,000 rpm. The model you must be thinking of must be the airplane version. I believe it has a peak rpm of 13,000 rpm. The use of a two speed In my opinion is not necessary. My modified .26 is capable of 27,000 peak rpm. With valve float happening around 28,000. Hopefully with Ti valves and rockers I might be able to get this to 30,000. This would only be 5,000 rpm shy of most two strokes. Add the fact that you can engage the clutch much earlier on a four stroke due to it's awesome torque down low. I think it should be very compareable to two stroke power spectrum just 7,000 rpm lower in the range. Look again at the dyno graph, it shows the engine peaking at 26,500.

As for the piston material, I believe it is high silicon aluminum. And yes this engine has a piston ring.

Hope I have answered your questions.

BK

zimzalahbim

My Feedback: (8)

perhaps my next statement doesn't pertain to nitro engines that are used frequently, but doesn't the fuel residue (i.e. left inside the crank area, and not accessible for after run oiling) cause everything to rust or corrode? i use after-run oil each and every time i finish running for the day, because nearly every nitro engine guide advises its use. so do you think that the crank, push rods, cam will receive adequate protection (after-run oil), or if the engine is not run regularly, will you encounter a rusty crank? or do you propose that enough after-run oil can seep through the piston rings to protect everything below the engine head.

Kysi

jave you dynod other engines, like rb's rossi, fantom etc?

mxwrench

Kysi,
I have dyno'd, Novarossi .12, Novamega .12, Top .12, RB .12, Palmaris ps.12, Thundertiger .15, and Sirio .21 engines so far. The top italian .12's are all very close to eachother, they just vary in power characteristics.

BK

p113

if you had a four stroke the gearing could be much higher but the weight would be much more that a to stroke there also less compact
and for the job or powering rc cars 2 stroke is definiately more suited

but if you want a 4 stroke and your doing a self build click on the link

[link=http://www.honda.co.uk/garden/GardenStoreLookupServlet?hidActionDetail=GetBrushc utterDetail&hidBrushcutterID=8&hidTitle=Brushcutters&hidCategoryID=2]4 stroke link[/link]

i know it a strimmer BUT its 35cc easy to strip down to its engine 4 stroke powerful and ive used it 1 pull start from cold no choke just a few sqirts of fuel and very economical

mxwrench

I spoke to OS today and they reported that they would not be importing the OS FS-26S-C Ver II to the states due to lack of sales with the previous version. I gave them the rundown on what I was doing development wise and they basically said that if I could show the interest was there they might change their mind and import a small quanity. Let me know what you think. If the OS FS-26S-C Ver II was competitive in modified form and could compare to full race .12's would you be interested in racing them? If so how much would you be willing to spend on modifications? I think the retail price for the engine stock is $199.00. So if you spent $200 in modifications it would still cost less than alot of Italian race .12 engines.

Let me know what you think, should I push for this engine to be imported to the states or should I scrap the four stroke development project altogether?

BK

www.nitrodynesystems.com

shain

My Feedback: (1)

I been searching high and low for a good price 4 stroke of this type for my tmaxx and I know they are not planning on importing them anymore. However, arn't they basically airplane/heli engines and couldn't we just use a similar four stroke airplane/heli engine and rig them to work in the rc car? We already have to rig these discontinued engines to work well in rc car and I don't think it would be any harder to do the same for the airplane/heli engines. I am sure someone has done it, just wondering if it's possible.

mxwrench

Shain, the four stroke engine you are looking for is specifically designed for car use. An airplane engine doesn't have the rpm capability that the car engine does. I suppose you could buy a OS FS.30 and use a crank, cam, valve spring set, intake manifold and carb from an OS FS-26S-C engine. These parts are still available from tower hobbies if you wanted to make the conversion. Without these parts though, the OS FS .30 is limited to 13,000 rpm vs OS FS-26S-C's 20,000 std rpm limit. With the pipe and intake manifold I developed and a good carb from a novarossi type engine the rpm limit is raised to 27,000 rpm and the tq is up 30% and the hp is up 45%. Hopefully when me head is done we will be able to match the output of a Novarossi type engine. However we will always fall short in the rev dept. The four stroke is able to use the lower rpm (start at 5,000 vs 12,500 with a two strroke). So the rev range stays nearly the same.

Four stroke useable range 5,000-27,000 =22,000
Two stroke useable range 12,500-38,000 =25,500

My $.02

BK

http://www.nitrodynesystems.com

mxwrench

Hello all, I just thought I'd share my latest findings. I tried some different glow plugs and found the plug from a OS rotary or wankle engine worked best. I achieved a substancial tq gain. The front side of the curve jumped up quite a bit!

Green run= engine in previous modified form with modified exhaust and 6mm carb
Blue run= all these changes plus RE glow plug

Much more to come! Stay tuned, I should have the CNC head ready to test in a few weeks!

BK

http://www.nitrodynesystems.com

elvisreturns

It depends what youre looking for only a 4 stroke can make that roar on a drive by only a 4 stroke has that torque

powder_king

That is the biggest line of bull**** I have ever heard of. With proper mods they could take a .80 of bigger. It would be trying to fit everything that would be the problem. Just like my dad stuck a 454 chev big block into a jeep cj-5 and it would pull catwalks. Nothing broke untill he rolled down a bank sidehilling but the drive train took the power. (330 hp) Where stock was abot 130hp So think before you say dumb stuff like that.