29cc strocke or not???

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dunerrunnner

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Hi, I'm about to order a new head kit for my 26cc fuelie dunerunner, but i'm not sure if should get a 36mm head to use with my stock crank, or get a 35mm with 2mm stroke crank.


I want to get torque on take of and high rpm's.


Thanks.
 
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Isnt the rule the bigger the piston more TQ but less RPM? For a stroker I wouldnt go bigger than 28.9, for a non stroker 28.5. If you want better performance from any head get a ported one, stuffed crank, lightened piston, and nice pipe. And keep in mind too much power can be a bad thing. I do admit though the ONB full mod 30.5 is awesome! I talked on the phone last week when I ordered my engine head kits and was amazed at the RPM I was told that motor makes! Check out the video on ONB site. Keep in mind though thats on a 2wd. Unreal sounding! Smoking the tires! But not in my Rampage!
 
You want TQ on takeoff and high RPM? Call ONB tell them that, what vehicle its going in, and what pipe you have and ask what he recomends.
 
Croozer said:
Don't get hung up on the big bore kits, they don't make more power than a well built 26cc unit.
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Are you kidding me? So displacement has zero effect on performance....You know better than that.
 
It depends on how you measure power......... :D You know like how a honda 4cyl can make tons of (horse) power but not get a lot of work done? HP is only part of the equation!
 
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Obeast44 said:
Are you kidding me? So displacement has zero effect on performance....You know better than that.
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I've seen the results of side by side testing on a dyno and the big bores fail to impress.


Those big bores look great on youtube videos but you will check into heartbreak hotel when you line up next to a well prepped 4 bolt Zen 26cc engine.
 
What I have read and what I think what youre saying is:


On a dyno powerband of the 34mm ported is very good but 36mm not as good. 34mm are more appropriate for the application of a rc car geared for 40-45 mph. So basically in theory say a 36mm would have a too low powerband when most of us drive our cars at the mid to upper end.


So basically a the powerband of a 34mm will have a more broad powerband while the 36mm is mostly down low. That makes the 34mm more responsive at any throttle position.


Gearing can improve the larger engines response but it cant help at the bottom end and top end at the same time so the 34 is at an advantage.


So the larger engines do have more power, and can get more work done (watts) but its not as effecient/effective as a smaller engine at harnessing the power for this rc application.


Kind of like how a 9000kv motor can put out more power (watts) at the same Volts as a 4000kv motor but the 9000kv isnt as effecient/effective as the 4000kv in offroad even taking gearing into consideration. The 9000kv is more powerful but it has the wrong powerband for offroad. Vice versa is true too. The 4000kv would not be effective in a carpet racer as the 9000kv even taking gearing into account. Sometimes more power can be slower.


I think the 34/36 debate is similar: which motor on the same voltage is best suited to my application and which motor on the same blend of fuel is more suited to my application? Which motor can produce a powerband I can use the most effectively in my application taking fuel blend and gearing into account?


Is all of this the correct theory? Things like this are hard to prove!
 
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HP=TORQUE X RPM / 5252


1HP=746 Watts


That makes it easy to see you need TQ and RPM. It also makes it easy to see you can have tons of RPM and no TQ but lots of HP which isnt a good idea. You need a balance. This doesn't show the powerband though or the powerband of an engine installed in a RC car with load applied.


I like to use watts. Not getting into it but I started reading about watts when I noticed the escort cosworth's power was measured in watts and wondered why.
 
HP is only the working product to give what power an engine have, on a dyno you only measure Torque.


You also cannot compare an Electric motor and a Gas motor, both work differently, an electric motor give alsmot a constant torque for 1 revolution as a gas motor only give one peak torque for 1 revolution.


Also, a smaller CC engine are not winner because it show a higher ''peak'' HP than a bigger CC engine, what is the best is an engine with a torque curve as flat as possible on all the RPM range.


Now, what engine you need is not necessarily what other people think it's better.


don't remember that between 26cc and 29cc there is only 3cc of difference, what you read over the net is not reprentative of the real life, there is tendency to exaggerate on the net.


He already have a 26cc in his dunerunner and want more power, that thing is huge and weight alot, thus go for bigger cc and enjoy.
 
Croozer said:
I've seen the results of side by side testing on a dyno and the big bores fail to impress.
Those big bores look great on youtube videos but you will check into heartbreak hotel when you line up next to a well prepped 4 bolt Zen 26cc engine.
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Actually I wont be checking into Heartbreak Hotel at all. Id gladly line my 30.5Zen against a 26cc Zen all day everyday.
 
i have the ported 29 cy kit plenty of bottom and top end,ported 30.5 in my tt thats another story wow.
 
You can clculate HP on a dyno. Its fair to compare electric and gas because your asking both to do the same thing: work (in our case move an rc car). Aslo we have the option of using either in RC. The numbers don't fully relfect the capabilites each motor/engine. Theres powerband, peak power, peak effeciency, blah blah.....You have to pick whats best suited for your application.


2 quick questions:


1- what engine would you build for a Rampage in a 75ft drag race?


2-what engine would you build for a Rampage in a 75ft drage race up a 60 degree incline?
 
3-which engine for this track: straight flat for 100ft, whoops, 3 6ft jumps some with down sides, 75ft straight, one S turn, 1 U turn, 100 ft straight, 3 corners, 1 jump, 75ft straight.
 
A large or small engine can do what is in the video. Maintain constant speed with good accleration? Yeah youre right you don't need the biggest engine for that. Is the large scale speed record still 97.96mph on a 27.2? Theres a reason he chose the 27.2 over a 30.5 or a 26. He matched his engine to its intended application.


If your being timed in a race, want the most effeciency, or want the best performance your best bet is to match the powerband to its inteneded application. Each engine build has a different powerband. Do you need high rpm, power down low/mid/top/lowmid/midtop, where do you want the most throttle response, top speed, pipe, gearing, etc.etc. If only one engine was all we needed for every stituation there wouldnt be any others. I tried to illustrate that in each of my examples 1,2,3. If I was in a race my life depended on I personally wouldnt use the same engine in all three examples.


This is the real world though, I only want to have fun. I want my car to accelerate fast, go 40+mph, be able to do some mild climbing, be able to floor it while turning and not skid out, and not break the drivetrain. Those are the real limiting factors to me. I don't need to know "between a 27.2, 28.9, 28.5, 26, which one is a few seconds quicker?" Those are my personal engine choices because they all meet my needs and get my job done.


Sometimes you do need a big bore: would you rather have an which would perform better a super built 23 or a super built 28.5 in a Ramp MT?
 
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For a rampage or a 4wd I will definatly choose a 36mm 28mm stroke, and probably bigger for an all aluminum rock with MT tire, however we are limited to 30.5cc for now.


For a 2wd feather Baja, this is another story since you loose a lot of traction, less moving parts.... etc.. your always in high RPM, where a small engine enjoys working.


It'll be interesting to see the Ron E's (I think) 35cc, I'm curious to know how much RPM that engine can make....
 
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