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Old 03-01-2013
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Default 4 stroke coming

http://www.roarracing.com/?p=1814

ROAR proposes specifications for 1:8 competition 4-stroke engines

To encourage the development of new technology for 1:8 nitro racing, ROAR is establishing guidelines for four-stroke engines that, if produced, will be permitted to run alongside the current two-stroke engines at any ROAR National Championship or sanctioned event.
Four stroke engines have dominated the SX world, and they’ve eclipsed the performance of the two-stroke engines once thought to be superior in terms of total power and power-to-weight ratio. The proposed specifications are taken directly from the displacement increases permitted in SX racing, and the bore and stroke dimensions are in direct proportion to the engines powering modern SX racing machines. As is often the case, technology and specifications that are ideal in bigger engines don’t always translate to the engines used in RC racing, but as a starting point, these will be the recommended specifications. ROAR encourages any engine manufacturer to confidentially discuss these specifications with ROAR prior to construction using a different specification.
Converted four-stroke airplane engines have been tried at random points in our past, but these engines were never configured for high power output, or for the rigors of RC car racing – they were simply airplane engines adapted to fit RC cars. But proper four-stroke technology applied to RC car engines can offer increased efficiency, a reduction in exhaust noise, and as seen in the SX world, potentially much more usable power.
Due to the higher number of moving parts, the costs of a four stroke engine can be greater, so economy in the design is paramount. There are some allowances in the proposed specifications that could mean additional costs. These are all open to discussion and perhaps the specifications can be more narrow if it’s proven that a simple and less costly technology can produce similar results to those that are more costly.
Proposed specifications:
Bore: 23.15mm
Stroke: 14.96mm
Displacement: 6.30cc (.384 c.i.)
Single cylinder only
2 to 4 valve configuration
Must use a single camshaft
Pushrod or OHC permitted
Spark or glow ignition
Air cooled only
Additional specifications will develop if and when engine manufacturers decide to produce such an engine, but these basic specs are sufficient to begin the discussion.
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Old 03-01-2013
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what fuel do they use nitro or petrol
i would be tempted with anything four stroke 1/8th especially if it uses pump petrol
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Old 03-01-2013
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Originally Posted by johnnygibbon View Post
what fuel do they use nitro or petrol
i would be tempted with anything four stroke 1/8th especially if it uses pump petrol
specs say spark or glow ignition so both id guess
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Old 03-01-2013
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Didnt hpi show one of these last year?
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Old 03-01-2013
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4 strokes are used for aircraft a lot, smoother delivery of power one of the advantages and more torque letting you swing big props

http://www.osengines.com/engines/osmg0830.html

this is smaller than the spec given and costs about £130, OS are the masters of these engines in the rc plane world so the tech is there there just needs to be demand to encourage a differant power delivery for cars. One newish development is you can now run electronic ignition on a nitro 4 stroke which means no more glow plugs and it can't be a massive leap to convert it over to gas use.

dedicated gasoline engines are around but not so small sadly mostly used in large scale but they sound so good in multi banks

listen to this radial engined monster

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Old 04-01-2013
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i think i want a 4 stroke buggy that runs on petrol not nitro not 2 stroke but 99 octane petrol from the pump just like my car and my bike ( the 1st production off road bike to come with fuel injection)
petrol 8th buggys thumping down the track
im in
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Old 04-01-2013
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When I went to brooklands in 2006 and watched the RC bike worlds a chap called Graham ( he may well have worked for Amerang or Thunder Tiger at the time ??? ) was running a 4 stroke engine in an RC bike, was longer than the other bikes to allow for the engine but it was reliable and went well !!!
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Old 04-01-2013
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This sounds interesting but at the risk of being a killjoy i'd be a bit cautious about this, it could be a ruse to suck more money out of people under the guise of the "environmentally friendly"/"now available in the UK" routine.

4-stroke dirt bikes undoubtedly have come on a long way and are impressive but they've also made the sport a lot more expensive for the average guy in the street, and a lot of people are apparently now going back to 2-strokes because they're simpler and cheaper to maintain. On the other hand 4-strokes are able to dominate at the top level because the factory teams are able to afford a complete engine rebuild after every race.

In the '90s Honda built a 400cc 2-stroke for the Dakar Rally called the EXP-2 which was more powerful and cleaner than the equivalent 4-stroke.

Wikipedia:

"With the utilization of a redesigned exhaust port valve and the ARC (Advanced Radical Combustion) system engaged, the engine would produce a pre-ignited combustion effect at low throttle that would completely burn all fuel in the chamber compared to how a conventional two-stroke engine would lose part of the intake charge.[1] The result decreased two major drawbacks of two stroke technology of both incomplete combustion of fuel at low RPM and expulsion of unburned fuel at high RPM".

Check out this link also:

http://www.motorcycle.com/manufactur...xp2-14293.html

This may be a good thing or it may not, but the fact remains that politics and fashion killed off 2-stroke motorcycles and a lot of people now mourn their departure, check out how much an immaculate Suzuki RG500 or a Honda CR500AF (a made-to-order CR250(alloy)-framed, CR500-engined motocrosser) sells for.
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Old 04-01-2013
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HPI brought out a 2 stroke earlier this year that uses pump petrol like a strimmer engine, i think it will be more like the rc planes that run on nitro and are 4 stroke the pipes are tinny and are very torquey
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Old 04-01-2013
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The aero guys are using cdi systems and spark plugs to convert 4 stroke nitro to petrol/gas.

They still require oil mixed with the fuel to look after the engine though.

have a read of this

http://www.justengines.co.uk/acatalo...xperience.html

the key if running 4 stroke is that the torque of the motor is much higher at lower rpm, setting a clutch is going to be really tricky. You would need a very soft spring to get the earlier engagement and i would guess gearing would need to be differant. If i had the cash i would love to try and work with one of the existing 4 strokes and see how viable this is
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Old 04-01-2013
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I'm not sure this will happen to be honest. Four strokes are inherently more complicated and thus expensive and heavy. With the power required for a rally cross buggy the revs will need to be quite high for a four stroke and this generally means that pushrods are out of the question, and an overhead cam and drive will be hard to develop and expensive.
Also you have to think of the lubrication, I can't see splash feed from a sump working as every time you crash the cylinder could fill with oil. The only way round it that I can see is sealed pre lubricated roller bearings for the crankshaft and con rod, but this would mean that the con rod would be much larger and heavier which would restrict engine speed again and you would still need to lubricate the piston/liner.

Maybe ROAR know something we don't but if this does happen I will expect the engines to be expensive to buy and maintain.
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Old 05-01-2013
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Quote:
Originally Posted by badger5 View Post
I'm not sure this will happen to be honest. Four strokes are inherently more complicated and thus expensive and heavy. With the power required for a rally cross buggy the revs will need to be quite high for a four stroke and this generally means that pushrods are out of the question, and an overhead cam and drive will be hard to develop and expensive.
Also you have to think of the lubrication, I can't see splash feed from a sump working as every time you crash the cylinder could fill with oil. The only way round it that I can see is sealed pre lubricated roller bearings for the crankshaft and con rod, but this would mean that the con rod would be much larger and heavier which would restrict engine speed again and you would still need to lubricate the piston/liner.

Maybe ROAR know something we don't but if this does happen I will expect the engines to be expensive to buy and maintain.
solutions are above your post, there very toquey so you change the gearing masivly, and you put oil in the fuel for lubrication
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Old 06-01-2013
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I think 4 stroke is very likely to happen.
Personally I like the added tuning potential and great noise. I have been working on my own 4-stroke engine for a while (7.7cc DOHC, so higher RPM capacity). To test the principle I have fitted my buggy with an ASP 56 4-stroke. I'm soon going to start running it.
Clutch and gearing issues are pretty easy to overcome. Oiling as Mark has stated is not a problem, piston ring blow-by lubricates the bottom end from oil in the fuel. One big issue is heat, these run a lot hotter than current racing two-strokes. Both because of the extra friction and the fact they don't blow most of their fuel straight out of the exhaust, taking the heat with it. The plus side is they are much less thirsty and cheaper to run.
Here's my set-up.



Although this is still a glow set-up, I think the holy grail is going to be spark ignition petrol. That's my target for the 7.7cc engine. Glad to see HPI has got the petrol idea coming in their 2-stroke.
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Old 07-01-2013
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http://www.justengines.co.uk/acatalo...xperience.html

have a look on this link Longrat, they allready make an electronic spark system for the engine you have fitted. Then you can try running petrol
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Old 07-01-2013
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Thanks Pro4nut, yes I am aware of that CDI unit and am pretty sure I am going to test it. Really nice that they also now supply spark plugs with the same thread as a glow plug, that's been a big issue in the past with most engine builders making their own.

The other issue with petrol is that you need so little per power stroke that nitro engine carbs need to be closed up a great deal to avoid running rich, which makes the needle setting very sensitive. But it seems most people manage to run them successfully. I am planning a fuel injected system for my engine which should avoid this problem and give other benefits, in the future.
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Old 08-01-2013
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This is nothing new,
4 stroke engines was around for cars years ago! Theres a reason why they died out!!!
Maybe before Marks time but Kyosho Supertens used to have optional 4 stroke fitting kit, sound was fantastic! but cost was too high and OS being only manufacturer did not help that.

As i said to Mark already 4 stroke engines will come into place if they have power or price or both improvements over 2 stroke.
RPM has always been the key factor in RC and 2 stroke will always win over 4 stroke.
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Old 08-01-2013
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Indeed those cars did die out. They do have a very strong following in small groups though. The problem was they were not really race cars, but commanded similar prices. Bashers would not pay those prices for something that on the surface looked the same as any other non-race road car from HoBao, Thunder Tiger etc. Plus there's a lack of understanding generally of 4-strokes in the car scene. It would have helped a lot if other manufacturers had jumped on it too and used the OS engines in their cars, but as far as I remember it was only ever Kyosho.
The real 4-stroke fans were all putting bigger engines into their race spec cars. One guy actually produced a kit for a while for the Associated RC10GT truck (Thumper RC). In that class the OS 26 was competitive with the 2-stroke .12s.
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Old 09-01-2013
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You also have to consider that OS aren't the only manufacturer any more with ASP making some decent engines for good prices.
As i have mentioned things have moved on, the cars have developed around high RPM 2 strokes so some work needs doing for sure but it would be nice for something different to appear
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Old 27-01-2013
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Quote:
Originally Posted by pro4nut View Post
4 strokes are used for aircraft a lot, smoother delivery of power one of the advantages and more torque letting you swing big props

http://www.osengines.com/engines/osmg0830.html

this is smaller than the spec given and costs about £130, OS are the masters of these engines in the rc plane world so the tech is there there just needs to be demand to encourage a differant power delivery for cars. One newish development is you can now run electronic ignition on a nitro 4 stroke which means no more glow plugs and it can't be a massive leap to convert it over to gas use.

dedicated gasoline engines are around but not so small sadly mostly used in large scale but they sound so good in multi banks

listen to this radial engined monster

That sounds So Sweeeeeeeeeeeeeeeeeet
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