difference between 4 cycle and 2 cycle engine?
 

Kyosho is comming out with 4 cycle engine cars.
What is advantage of 4 cycle engine in terms of performance?

If 4 cycle means 4 stroke the only advantage is in fuel consumption.

don't feed him full of crap.

A 2-stroke, or 2-cycle fires once every 2 strokes of the piston, and has no valves, only ports.

and a 4-stroke, fires once every 4 strokes of the piston, the advantages, 4 stroke has a cooler running temperature, they are more durable and much more "torqish". they run at lower RPMs, and are smoother.

A 2-stroke will wind out alot quicker which gives it much quicker acceleration, but in the long run, a 4 stroke of the same size will have almost twice the top-end of the 2-cycle.

E-mail me if you need to know more.

Before you go accusing me of blowing smoke up someones arse maybe you should check your facts mate. A 4 stroke having only 1 combustion cycle for every 4 strokes will make roughly half the power of an equilivently sized 2 stroke. Its just basic physics.

A 2 stroke will always out power a 4 stroke whereas the 4 stroke will have more torque. 2 combustion cycles vs 1 combustion cycle every 4 cycles.

Uhhhhmm.... no...... that's BS. A 4 stroke has much more torque, which will accelerate out of a corner faster than a 2 stroke. RC Car Action has done a lot of tests on this in previous issues. Why do you thing airplanes use 4 strokes??? Torque....

On the other hand..... a 4 stroke will run out of leg on the top end- it has much heavier components to spin, and the RPM range is much narrower than a 2 stroke. Two strokes are running 42K+ rpm these days!! There is no 4 stroke that is going to match that RPM. Do the math, and tell me what will run FASTER on the top end.... assuming both engines are running through the same drivetrain. If the gear ratios are the same, and the 2 stroke will out RPM the four- the 2 stroke will be faster. I don't care if the 4 stroke has twice as much horsepower- if it's doing less RPM than a two stroke (geared with the same final drive) it will be slower- period.

It's simple physics......

let me tell ya somthing

torque=power

yea...... torque = power, but we also are dealing with gear ratios here and RPM limits of each engine.

Use a simple rollout /speed calculator and we'll see the winner here.

With a 1.5 HP Nova Rossi 2 stroke- capable of 40K rpm, and a FINAL drive of 4.00:1, with 60mm tires, theoretical top speed would be= 70.275 mph.

Do the same math on a 3.0 HP 4 stroke capable of only 30K rpm and you get a top speed of 52.707 mph.

Horsepower matters, but the winner here is RPM and gearing.

check this site for a neat little top speed calculator- http://www.pbracing.com/info_rcgears.html.

Does it mention horsepower or torque?? No....

Need a math lesson?? just PM me........

:weird:

Torque does NOT equal power.

Power (W) = Torque (Nm) * rotationfrequency (2*pi*RPM/60)

A 2-stroke may get much higher RPM than a 4-stroke, but they have poor torque, especially at high RPM.

Comparing both types of engines with the same gearing is unfair to both. 4-stroke will have much better acceleration, 2-stroke will have much better topspeed. I think you will find both are reletively close in performance when you find different optimal gearing for each for a given track.

how do I find out the gear box ratio???

What I was stating is that, as torque increases so does horsepower. torque is the numerator in your equation, so yes, it makes sense that more torque= more horsepower. heres the simpler version of the same equation for the mathematically challenged....

Horsepower= (Torque*RPM)/ 5252

from many runs on a real engine dyno, it's amazing how the HP and torque values cross at 5,252 RPM... always...

I also stated earlier that the 4 stroke would accelerate better, and the 2 stroke would have better top speed- with the same gearing. I don't think there are any factory kits that could be geared right for a 4 stroke using available off the shelf parts.

I think we are on the same page here, but others...... I'm not so sure:D

Has anyone seen 4 stroke engine V-ONE-RRR or FW-05R run?
Anyone from japan?
Check out the japanese kyosho web site using online translator and you will see the 4 stroke engine kit for FW-05r and V-ONE-RRR. They also have a nice video( but you have to download at original site). you can see the V-ONE-RRR Running.
So, if geared right, 4-stroke will have much better acceleration?

if geared right, a 4 stroke will unglue the tires!!

2stroke vs. 4stroke?? What????
 

First let me say your all on crack!!!

At this time there is NO 4stroke r/c engine that will out run a 2stroke. The technology of todays r/c 4stroke engines is way behind that of ALL r/c 2stroke engines. Even the cheap RTR engines are way ahead of todays r/c 4stroke engines.

If you were to compare a .12 sport engine (Fantom .12 for instance) to a .26 4stroke engine (OS Surpass .26 car engine), first you would get a max rpm difference of around 17,500 rpm. The .12 2stroke would have a max rpm of say 32,500 and the .26 4stroke would have a max rpm of 16,000. So gearing would definitly have a crucial role in comparing.

The 4stroke makes 1 power stroke per 2 rev. of the crank where the 2stroke makes 1 power stroke per rev of the crank.
4strokes make more torque on their power stroke due to the fact that the combustion pressure acts on the piston all the way down the power stroke. 2strokes on the other hand let the combustion pressure excape the cylinder around 2/3'ds the way down, and out the exhaust port. To make matters worse on the 2 stroke, the piston is fighting secondary(crankcase) compression at this time.
Your average 2stroke has a 85deg. power phase duration, where
your average 4stroke has a 155deg. power phase duration.
However the 2stroke gets to make a power stroke every rev. so that bumps the 2strokes power phase duration to 170deg., 10% more than the 4 stroke.

That said, you would need to double the displacement of your 4stroke to mathmaticaly equal the power of a 2 stroke.

Now to correct a few statements:
4 strokes run much hotter than 2 strokes. Always. (Remember the Kyosho Super 10 four, is required a fan driven off the crank to keep it cool).

There are no 4 strokes capable of 30,000 rpm. Valve float limits this physically.

A 2 stroke will wind out alot quicker due to the drastically reduced rotating mass compared to a 4 stroke.

The 4 stroke will NOT have twice the top end of a 2stroke, valve float prevents a 4 stroke from having rpm capabilities anywhere near a 2 stroke.

A modern r/c 2 stroke has the luxury of taking advantage of tuned pipes which makes them way more volumetrically efficient than a 4 stroke could ever hope to be.

Compare a 125cc 2 stroke mx bike with a 125cc 4stroke bike. 2stroke= 38hp, 4stroke =15hp.

Until very recently technology of 4 stroke singles has been in the stone ages. In the last 3 years 4 stroke single technology in the mx field has improved enough that 250cc 4strokes are now able to compete with 125cc 2 strokes. And that took F1 type technology to accomplish!

I challenge anyone to compare a .12 2 stroke to a .26 4 stroke on a dyno and show me how a .26 4 stroke could possibly make more power.

BK
Factory Honda mechanic for Mike LaRocco
Designer of the X-Dyno for Xtreme r/c magazine

http://www.nitrodynesystems.com

Wow Thanks everyone for the information.
I am overwhelmed. Although I am still confused. ( due to my lack of basic knowledge of the engine)
THEN, back to my original question, why would kyosho make 4 stroke engine for their car? what advantage do they see by doing this?

Hey BK, You are the guy in X-RC CAR Mag right?
Are you having fun testing all the engine?
I was wondering what engines are gonna be on the next Issue?
Keep up the good work....:cool:

i guess this is because the japanese like to try something different all the time. most of us would just want the fastest engine we can afford (can we handle the power ? we will worry about it later).

i think maybe with the right gearings, a 4 stroke car can do good on a small, technical track. that would be a competition of skills, not guts. but without actully drove one, it is hard to tell.

data

Regards to superten require a fan for 4stroke. The 4stroke engine was originally designed for airplane. As you see all airplane engine doesn't require huge fins or heatsink head to do the cooling due to the propeller is driving air flow over the engine. OS modified the .26 or .40 4stroke to fit on a car without altering the external casting. Secondly, the 4 stroke doesn't have huge heatsink head like our 2stroke due to the over head valves. It's main cooling are from the small fins around the cylinder wall.

The main advantage of 4 stroke engine is fuel efficency and huge torque produce on low rpm. Hence it can geared to very low gear ratio to make up lack of RPM comparing to 2stroke engine. A properly geared car for 4 stroke engine will be just as fast as properly geard car for 2 stroke entry level, 1HP rated, engine. But for each tank a 4 stroke might last 2x than 2 stroke engine so 4 Stroke engine is good for multiple hours endurance races.

From what I understand, the Japanese kinda have a cult following for the 4 stroke sedan class, It's not the fastest but it is becoming very popular.

Yes, testing engines is alot of fun, but sorry I can't say what were testing

I agree that 4 stroke engines have a huge advantage in the fuel consumption dept.

I will get ahold of a .26 surpass 4stroke engine and test it against a .12 sport engine, and post my findings.

Should be interesting to see exactly what the differences will be.

BK
http://www.nitrodynesystems.com

until the neighbors complain.

do you know what kind of fuel the 4 stroke runs ?

looking forward to it and nice work on the dyno.

There is a speical blend of fuel for 4 stroke engine but that's for planes. If anyone here have ran 4stroke version of kyosho superten fw04 or any contact with OS can share some light on this.

The RC car 4 strokes run on standard car fuel. I think that they recommend lower nitro content though.

It would be interesting to see just how much power the OS 4 stroke could make with a lighter valvetrain.

Comparing an OS .21 VZ-R Turbo 2 to an OS FS 26 SC...

The .21 VZ-R:

Displacement: 0.211 cu in (3.5cc)
Bore: 0.654 in (16.6mm)
Stroke: 0.630 in (16.0mm)
Practical rpm: 3000-42,000
Output: 2.5 ps @ 34,000 rpm
Weight: 11.1 oz (315.5g)


The 4 stroke:

Displacement: 0.269 cu in (4.4 cc)
Bore: 0.728 in (18.5 mm)
Stroke: 0.648 in (16.4 mm)
Practical rpm: 2000-22,000
Output: 0.5 ps @ 17,000 rpm
Power Output: 0.5 bhp (ps) @ 17,000 rpm
Weight (FS-26S-C): 8.56 oz (243 g)


As you can see the .21 puts out 5 times the power at twice the RPM.....

Bear in mind, all the research and development going into 2 strokes has yielded these power figures.

I'm sure with development we will see power increases in 4 strokes, and i think 4 strokes should run superchargers of some sort to increase output.

Perhaps dual overhead cams and 4 valve engines to increase power?? 4 stroke tuned exhausts, larger heatsink head etc.etc.
Just needs time and development, but 2 strokes will probably always have more power.

I heard a rumour that honda has designed a revolutionary 2 stroke that uses no oil, and is more economical than a 4 stroke.....


The fact that 2 stroke nitro engines have like 3 moving parts wins me over.....simple yet extremely effective...

Wow? That much Difference? :eek

4 strokes...
 

OK, I have a OS FS-26S-C Four stroke car engine on the way! I will dyno it when it gets here and post the results. I will also compare to a TOP .12 rear exhaust engine and post those results also.

My plan is to test the mini 4 stroke in stock form, then rip into it and see what kinda changes we can make.

First I plan to redesign the head with much larger cooling capacity, and a higher compression head with better port design, via CNC.

Second, redesign piston and rod for more compression and lighter weight.

Third maybe regrind the cam with more lift.

Definately a tuned pipe with a nice megaphone.

Maybe change the rocker ratios to gain more lift.

Maybe larger valves.

Maybe Supercharger similar to YS 63 airplane engine.


Not like I don't have enough projects going on right now but this thread got those wheels turnin' in my head, and I think it should be interesting to see what we can come up with!

Wouldn't it be cool to see a 4 stroke car engine that could outrun a 2 stroke on the track!!

Sounds like a tall order but who knows? 6 years ago who would have thought that a 250cc four stroke could EVER out power a 125cc 2 stroke! Now they have 5 hp on the little MX bikes!

Can't wait to get started!!!

BK

I just can't wait to see it.
Maybe you can make your own brand of Engine and sell it.
Keep us updated.

Dyno test of 4stroke vs. 2stroke
 

Sorry having trouble posting image...

Dyno test 4stroke vs. 2stroke
 

Here are the results of the 2 stroke vs. 4 stroke dyno tests.
The blue lines are the OS FS26S-C 4 stroke and the green lines are the AE ThunderTiger .15 sport engine. Both are completly std. No modifications.

Note: The four stroke came with no exhaust so currently I am using a short headpipe and FS26 silencer I picked up today.

Results clearly show the 4strokes superior torque in lower rpm's.
Almost 50% more than the .15 2 stroke. However the 4stroke is definitely limited in the rpm dept. Powerband is very narrow compared to the 2 stroke.

Later I will show more tests as I make progress in testing.

BK

I've got a 4 stroke Kyosho FW04. Haven't tried 4 stroke fuel yet but I've heard it improves power. Not sure how valid this info is but I just run what the other 4 stroke guys are running at my track. 20% with high castor oil content.

mxwrench is pretty much right too about the 4 strokes info.

I'm very interested in the development of this "modified" 4 stroke. I'd like to see stronger pushrods paired up with stiffer valve springs. That would certainly give it a little more RPM. And with a new profile cam with bigger valves that you're making, I'm sure it will be a beast in the top end. But definitely keep us updated. I love running my thumper but just wished it had more power!

where to buy?
 

I am wondering where to get this 4 cycle engine and what else do i need to put it in my car,, or do i need a whole new car. i have an MTX3

To answer your original question. 200mm cars were originally designed to run on smaller twisty tracks which they do in most parts of the world. For this type of track the 4-stroke would be a huge benefit due to its awesome low end torque for brilliant acceleration.

Profoxcg,
 

Profoxcg,
Unfortunately right now OS has stopped selling the FS-26S-C engine, and is very hard to find. The good news is they have a new version coming out soon. Hopefully, anyway! I have not confirmed if they will be selling them in the US yet. The new engine is called the OS FS-26S-C VerII, original huh?
Anyways, I have made huge improvements to the FS-26S-C over the past few weeks, see my post on this forum 'OS FS-26S-C development project'. I show my dyno graphs detailing my improvements! As far as what you would need to stick one in your mugen, I'm not sure yet. I hope to offer a conversion kit for all popular models of 'competitive' car kits in the near future.

Check back soon to see my latest results in development!

BK

great info thanks !
 

Thanks,

I love those original names lol

Two-Stroke VS. Four-Stroke Test Vehicles.
 

These two HPI MT conversions were of mine were featured In RC Nitro magazine December 2002.

I have not fully tested them head to head. I think it could answer a lot of questions.

Who would like to pilot the Two-stroke and where should we do it? I think it's time to get them dirty.

Nolan Farmer
farmer Plastics and Machining Inc.
Jamestown Colorado

You might claim to know a lot, but you've just said something that, in terms of physics, is plain, no-question-about-it, simply WRONG.

Torque, or, to use the scientific term, turning moment = force x distance from fulcrum. (Fulcrum means the point about which a turning object - in this case a drive shaft - pivots.)

Power is the amount of kinetic energy produced by the engine, therefore the amount of kinetic energy wich the car has.

Basically, to use equations:

Torque:

M = F x D.

Power:

KE = 1/2 x M x Vsquared.

Incidentally, concerning these two equations, the upshot of the first one is that the greater distance from the fulcrum, the more the torque applied to the ground by your car, so technically, by fitting bigger wheels, you will give your car more torque, but this doesn't improve acceleration, because bigger wheels are heavier. However, this is partly why big wheels are good for rock crawlers, which need loads of torque but not much acceleration. The upshot of the second equation partly explains why 4-stroke engines produce more low-end power, but 2-stroke engines produce more high-end power: as you can see from the equation, where M means Mass, the more rotating mass there is the more power there is. This partly explains the low-end power of 4-strokes; they have a heavier rotating mass, because of all he valves and springs and pushrods that they have. 2-strokes are better at the high revs for the same reason: they don't have any valves, or anything like that, so they have a much smaller rotating mass, so because of momentum (which is another story altogether which i won't go into here) they can rev higher, and becaue the equation tellls us that the more V (Velocity) there is, the more power there is.
This isn't actually the full story, but it is the basic reasons why 2-strokes and 4-strokes are different. The part that I havn't gone into is the chemistry of fuel consumption, and efficient burning of fuel. You probably don't want me to go on about Hydrocarbons for dozens of lines, so let's just leave it at that, eh?

So, there you have it, the PROPER explanation of just what's going on with engines.

:D

Torque = rotational force (for example one lb/ft is equal to the force of one pound applied one foot from the axis of rotation)

Power = the rate at which work is done (work is the ability to move an object that has mass)

What are your qualifications? I'm no expert, but I've never seen the equation Mass = Force x Distance. Maybe you are reffering to Work = Mass x Distance or maybe Force = Mass x Acceleration.


The reason why a car with smaller wheels accelerates faster has nothing to do with weight, but because the final drive ratio is higher. For each complete cycle of the engine, you have to move the car a shorter distance (the circumference of the tire) with the smaller wheels.

Your argument about applying more torque with the bigger wheels is flawed because you're looking at the system backwards. Try turning a nut with a longer wrench, and it will be much easier to turn. But in the case of a wheel, the force isnt being applied TO the fulcrum (the nut in my example), it is comming FROM it. Think of it like this: you're standing in place holding a pole, on the end of that pole is a 10kg weight. Will it be easier for you to pivot about your position with a shorter pole or a longer one? The length of the pole represents the radius of a tire.

Also while the weight of engine components do play a role in power output, it is not a significant factor in the different power characteristics of two-stroke and four-stroke engines. If this was the case, simply increasing the weight of a flywheel on a two-stroke engine would give it the characteristics of four-stroke. This concept also means that the entire valvetrain in a four-stroke engine is nothing more than a means to increase the rotating mass inside the engine. This is certainly not the case. Though the extra mass and friction in a four-stroke are definately what help reduce its maximum RPM, they are not what give it its advantages.

Wow, this is an old thread...

I've raced 2 types of 4 stroke powered cars against 2 strokes. One was at club level races at my home track, and the other was all over the Pacific Northwest in a series that averages about 200 entries per round. I run a Perry VP-30 fuel pump and WildCat HeliMix 30% fuel in both.

Car 1 is a Kyosho Ultima ST type R (2WD gas truck) with a heavily modified FS26-C. I've never raced it in a series for 2 reasons: 1, it's not legal. 2, it falls apart every gallon or so.
The reason it falls apart is because I moved the intake port from the back of the head to the side, and the intake manifold is held in place with JB-Weld. The alcohal in glow fuel attacks epoxy-based glues, so after about a gallon, it simply falls apart.
This truck is VERY competitive running 30% full-synthetic heli fuel, an OS 2 needle slide carb and bored out FS-52 muffler. Of course, it's geared to the moon, and as such will keep pace with a P-5 powered 1/8th scale buggy on the long backstrait.

Car 2 is a Traxxas Revo, which I race in the Unlimited MT class in the Northwest Championship Tour. It is powered by a modified OS FS52. Mods are:
FS40-C cam, valve springs, and spring seats
3 needle slide valve .21 2 stroke buggy engine carburetor
Surpass 90 muffler with bored-out stinger
Competition in this class is pretty tough, with most guys opting to run a TM18. There are some who run big block 2 strokes in their Revos, and a few LST drivers running the Collari .32! So far, I've not found myself wanting more power, and at most tracks I don't need more speed. I eat up the 2 strokes exiting corners, so of course I do better on tighter/loamier tracks.
This truck is very much in the prototype stage, and it's made 3 A-mains at 2-day races this year. Results of those races were 6th, 8th, and 4th. At the 8th place race, I set fast lap in qualifying and felt like I could have won, right up to the 11:30 mark when the transmission let go. I was in 2nd at the time and the guy in 1st ended up breaking. I'll get 'em this year!:sneaky:

The FS26C compared to the NovaRossi .12 I used to run has faster throttle response, more controllable power, and has this wicked little kick right when you think the engine's going to sign-off in over-rev land. You can see this on MXWrench's dyno charts of the modified 4 stroke on his website. In Dyno-land, it's a nice little peak. On the track, it's a power-lift at the end of a medium size strait. The 4 stroke also gets better fuel economy.

The FS52 compared to the 2 strokes I race against has more bottom-end accelleration, instant throttle response, but runs out of gear on a bigger track. It just can't breath as well as the FS26C, so there's not as much power on top. I've got taller gears on order for next season. 15/38 is stock. I was running 19/36. I will be running 20/35 next season. It has worse fuel economy than the TM18s, and about the same as the .28 - .32 big blocks.