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All Forums >> RC Cars, Buggies, Trucks, Tanks and more >> RC Car Engines >> Car Nitro & Gas Engines >> 4-stroke for RC?
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4-stroke for RC? - 8/18/2004 4:22:46 AM   
zimzalahbim



Posts: 715
Joined: 2/12/2004
From: mobile, AL, USA
Status: offline 		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?
       Post #: 1

RE: 4-stroke for RC? - 8/18/2004 5:09:25 AM   
Mike Abrams


 

Posts: 45
Joined: 7/24/2004
From: Copiague, NY, USA
Status: offline 		The only 4-stroke engines are for helicopters & airplanes, a 1\8 buggy couldn't handle the power of those engines.

(in reply to zimzalahbim)
       Post #: 2

RE: 4-stroke for RC? - 8/18/2004 6:07:45 AM   
zimzalahbim



Posts: 715
Joined: 2/12/2004
From: mobile, AL, USA
Status: offline 		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!

(in reply to Mike Abrams)
       Post #: 3

RE: 4-stroke for RC? - 8/18/2004 1:17:42 PM   
neil.jb



Posts: 801
Joined: 7/31/2004
From: , UNITED KINGDOM
Status: offline 		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

(in reply to zimzalahbim)
       Post #: 4

RE: 4-stroke for RC? - 8/20/2004 10:15:04 AM   
mxwrench


 

Posts: 104
Joined: 9/11/2003
From: Victorville, CA, USA
Status: offline 		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

Attachments
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(in reply to neil.jb)
       Post #: 5

RE: 4-stroke for RC? - 8/20/2004 3:02:30 PM   
zimzalahbim



Posts: 715
Joined: 2/12/2004
From: mobile, AL, USA
Status: offline 		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.

(in reply to mxwrench)
       Post #: 6

RE: 4-stroke for RC? - 8/20/2004 5:35:30 PM   
mxwrench


 

Posts: 104
Joined: 9/11/2003
From: Victorville, CA, USA
Status: offline 		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

(in reply to zimzalahbim)
       Post #: 7

RE: 4-stroke for RC? - 8/21/2004 3:33:45 AM   
zimzalahbim



Posts: 715
Joined: 2/12/2004
From: mobile, AL, USA
Status: offline 		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.

(in reply to mxwrench)
       Post #: 8

RE: 4-stroke for RC? - 8/21/2004 3:54:09 AM   
HighSierra



Posts: 572
Joined: 1/7/2002
From: Nor Cal, CA, USA
Status: offline 		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!

(in reply to zimzalahbim)
       Post #: 9

RE: 4-stroke for RC? - 8/21/2004 6:33:15 AM   
mxwrench


 

Posts: 104
Joined: 9/11/2003
From: Victorville, CA, USA
Status: offline 		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

(in reply to HighSierra)
       Post #: 10

RE: 4-stroke for RC? - 8/21/2004 6:42:36 AM   
zimzalahbim



Posts: 715
Joined: 2/12/2004
From: mobile, AL, USA
Status: offline 		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.

< Message edited by dirtbug -- 8/21/2004 1:43:21 AM >

(in reply to mxwrench)
       Post #: 11

RE: 4-stroke for RC? - 8/21/2004 6:49:22 AM   
mxwrench


 

Posts: 104
Joined: 9/11/2003
From: Victorville, CA, USA
Status: offline 		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

(in reply to zimzalahbim)
       Post #: 12

RE: 4-stroke for RC? - 8/21/2004 12:13:26 PM   
zimzalahbim



Posts: 715
Joined: 2/12/2004
From: mobile, AL, USA
Status: offline 		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?

(in reply to mxwrench)
       Post #: 13

RE: 4-stroke for RC? - 8/21/2004 3:31:12 PM   
HighSierra



Posts: 572
Joined: 1/7/2002
From: Nor Cal, CA, USA
Status: offline 		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

(in reply to zimzalahbim)
       Post #: 14

RE: 4-stroke for RC? - 8/22/2004 5:06:50 AM   
mxwrench


 

Posts: 104
Joined: 9/11/2003
From: Victorville, CA, USA
Status: offline 		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

(in reply to HighSierra)
       Post #: 15

RE: 4-stroke for RC? - 8/22/2004 8:13:20 AM   
zimzalahbim<