Bore vs Stroke vs Displacement
 

How much does bore, stroke and displacement factor into your engine purchasing decision? Do the same undersquare and oversquare performance concepts apply to the performance characteristics of R/C engines?

Thanks! :)

Answers.com:

- Undersquare: http://www.answers.com/topic/undersquare

- Oversquare: http://www.answers.com/topic/oversquare

Formula used to calculate displacement:

Displacement = (PI/4 * Bore^2 * stroke) / 1000

If I need to use a different formula, please let me know. :sweat:

You have pretty much answer on your question with those links. I just want to add:
Force which is pushing piston down is equal to pressure multiply on piston top area. So bigger diameter means more force will be pushing piston down. So base on your links and force you can make your decision. Also as a tip, I iwll recomend use timing calculator to calculate engine capacity ( you will not need to use formula). Timing calculator you can find http://www.palmarisracing.com/Timing_Calculator.htm
I hope I was helpfull.

Does it mean that a bigger bore will give you more torque? Or am I looking at it the wrong way?

In reasonble limits yes. About 1% in force, make math, pressure is about 85 Kg sm^2. But defenetly we have to take to concideration all other variables as strock, connecting rod ratio (with shorter strock we can make connecting rod shorter) etc. Answer is Yes.

What I've been told, is that a longer stroke means more torque. In the examples above, just by stroke length alone, the LL3 would appear to have the most torque. Are you saying that this isn't necessarily true? Would it also be incorrect to assume, that just because the STI and Ninja have the shortest stroke, that they also have the lowest torque?

Thanks for answering my questions. I'm slowing but surely getting smarter. ;)

I know Robert... "Get the STI!" :sneaky:

Hi Edward, this is Anthony.... last time we met in your place ( 3 BRB p/s/r ).

How are you ?

The BRB p/s/r is doing very well :smile:

Get the STI. There's more than enough torque and it just keeps on revving. I find where other engines reach max revs (on 200ft straights), the STI just keeps on accelerating. If only the straight was longer...

Dave

So if all are motors are supposed to be limited to 2.1cc how does Sirio and GRP get away with a slightly larger displacement?

BTW anyone have an on track performance comparison between the ll3 & ls3? I have both and although the ll3 is supposed to have more torq mine feels as though it revs higher with the same torq but and a slower spool up than my LS3, is it just my tune or are others getting the same result?

Mark

You have to give way for tolerances, it would be 2.1cc + or - the tolerance. It's like your fullscale car, the engine might be rated at say 2000cc but if you look closely at the engines specs it may be 1980cc on one car and 2010 on another but they are still considered 2000cc engines.

EdwardN, again you come to the rescue. Where is the cut-off point between long-stroke and short-stroke, i.e. up to what length conrod is considered short stroke and over that long?

Mark: This is what Uriah had to say...

Thanks Dave. I know you guys are giving me a solid recommendation. :nod:

I'm 99% sure that I'm going to get the STI, but I just need to be absolutely sure it has the most potential to take out the JPs. I know that my tuning, setup and driving need to do the rest. :D As my knowledge grows, I have a tendency of changing my mind about what I want to get. :sweat: I guess it's all part of the discovery and learning process.

I made one bad engine choice this year (nothing having to do with competing against the JPs BTW) and I don't want to make another. :sneaky:

Now that my TZ issues have been worked out, I'm pretty happy with it. I really like the low-to-mid range powerband. It makes it easy to drive fast on our track.

Just FYI Edward, this is the track I race on:

- Picture - It's not L shaped BTW

- Video - Both leaders are running MTX-4s w/JPs.

Hmmmm... More interesting info...

Check out the graph guys.... :sneaky:

http://www.axialracing.com/details.p...imgID=1&type=2

mxwrench! ;)

Well, a guy at my track has a JP, and on the straight I edge him slightly. But absolutely no engine I run against can pull me on the straight. It just doesn't scream like the other engines, but it has a smooth acceleration. So, if you are trying to compete with JP's, Sirio is the way to go. My track is small and technical like yours.

Yeah, another one thing that I failed to mention in my previous post (Osiris nailed it) is that the STI's powerband is really smooth (This, of course, does not mean that it isn't powerful). It makes for easy driving.

Dave

If you look at mxwrench's comparisons of the JP and the TOP, they're similar to what Axial's results were for the respective engines. Assuming both Axial and mxwrench's dynoing methods are similar because of these results, we see that the Novarossi LS3, Sirio Evo 3 and the Orion Wasp are more powerful.

Dave

The results are similar I think because mxwrench built both dynos.

im gona stay with jp and novarossi from now on WHY DAVE you know why i cant run the damm sirios there not for me cuz i break them all the time. and now the LL3 has more torque whether you feel it or not the LS3 has less. the sti has more power i dont know how to explain better but the ninja should have more power.

Ahh, that's too bad Wally. I liked the fact that we were the only two to venture beyond the mainstream Novarossi engine.

Dave

ok ok ill get a crank for it but i still have my evo2 i just need a button and a con rod oh lol a carb.

Why do you think that is all listed motors above more powerfull? Because HP numbers is higher. Let me explane to you how the dyno results calculated. HP numbers comming from torq multiply on RPM (where max torq was read) and multitply on some coeficient, I think it is .53. So if you look on the number right then you will find it is not what it looke like. Please keep in mind that our clutch usualy engaged at about 28-29 K RPM, so please look which engine has more torq at taht RPM and how you have to set up other engines to get the same torq, Also look which engine has more torq on the end of curv it will show you how engine will keep pulling on end of straight. So after analizing all this points you will understand that it doesn't look like just pure numbers. Remember HP sell engines, torq wins the races.
So if you want to make your decision-chose for your self-is this modded or stock then you have choice in modded and stock engines.
BTW, Axial motors 2 nd place on winternats and it was running against one of moddifyed engines from your list (literaly) and won it, PreNats 1 st place, Texas Biggie TQ and won etc-I don't have time to list everything. If engine is not powerfull how is that happened?

All you need to list is the last biggest race The IFMAR SEDAN WORLDS in Australia What Happen to AXIAL I guess nobody wants to run it because they know the motor is not fast enough meaning Too SLOW, the only reason axial won the Texas biggie is that no body else was there to race, if Swauger or Cyrul is there axial would have not TQ or won at all, i guess you can't bragg about axial winning anymore because you run out of drivers that are willing to run axial

On Winternats everybody (or almost everybody ) was there,On PreNats Swager was there, also Tosolini, On Nationals Ron Atomic went straight to the A-main and finish 7th. Worlds, why would we go to the worlds spend tons of money and don't have top level driver-all of the top level drivers unfortunately for us had contract with other companies-to get 27 th place?As far as nobody wants to run our motor-well I think it is your guess-so far it was represented well, got very good results (see above). I think it is pretty good for start. And belive me it will continue like that. Please remember and talk to people in RC community, if I sad belive me, then it means this will happened. So far for last 3 years nothing what I promised was faulty.
Edward

Thanks Edward. I understand what you getting at. ;)

Osiris 75, Dave and Wally: Thanks guys! Really appreciate the continued feedback and support. :)

Kyosho should send you guys a free t-shirt or something. :D

Well, I believe the drivers made a good choice not running Axial, because they know it is not fast or reliable, well I saw some of your post saying it will never overheat, yes it may not overheat but when you run it and it temped in at 400 + degees the motor flames out anyways causing vapor lock (preventing fuel to reach the carburetor resulting in to hard to start or no start at all) so what good is the motor if you can't get it started, Axial will be a great motor............well maybe someday........ if you find the missing link. but for now please be humble, do not try to be too proud of it until it is proven consistent and tell Axial to lower it to about $150.00 then maybe it will be worth the money nor $300.00+ that's a joke

maybe ill try one of these axial motors and see and if it blows up like a os ill say here

Wally! Is this why you've got problems with your STI cranks? :lol:

Do you destroy engines on a regular basis or is this something new? :sneaky: By "os" do you mean an O.S. engine??

Mate what engine/s do you run ,have you owned a Axial to justify you dissing it ???

yes o.s and iv never blown up a novarossi or novarossi base motor they just wear out and i do run them alot

I owned every engine that is worth the money, I don't waste money on something that is worthless, I don't have to own an AXIAL to justify my comments, it's proven, that is why no body runs it in the worlds because everybody who competes in the worlds wants to have a chance to win.
THAT MEANS IF YOU RUN AXIAL YOU WILL HAVE 10% CHANCE OF WINNING IN A BIG RACE, meaning if every body breaks down and you are the only one that is left, now you tell me WHO IS YOUR DRIVER at THE WORLDS? WHO?........NOBODY

You can never blow up an Axial..........because it is not fast enough

In generaly speaking you defenetly don't need to owe anything to justify nothing. The question is how credible your justification is. So far Axial attend banch of races and pretty much always end up on A-main (regardless who was present- I am sure it is stupid to start list races and attended people here again) and it is proven by results which you can find everywhere on. So far you didn't bring one single sample when Axial engine didn't perform. So I personaly will put on question your qualification to make any justification in RC, even your name doesn't appear on any races. So you just one of the proven keyboard basher.
Good luck.

I am just telling the truth, why you can't handle the truth?

:lol: :lol:

You guys!! This is what I'm picturing in my mind: http://www.nitrokb.com/temp/

hmm
 

oh boy

you dont know me to well do you LOL my 2 o.s motors the piston blowed up real good like, cuz the con rods wore out realy fast and i did not change them. ONE DAY OF RUNING.

And how old are you??? 30-plus... Ok... Not trying to flame... Just making an observation... Goodluck with all your broken motors... :deathstar

RC_Alan

:lol: :lol: :lol: im just saying that i dont break novarossis and all other motors i try i break over the past 10years or so, oh and im 39

:lol: :nod:

RC_Alan