rmdhawaii

iTrader: (4)

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.

EdwardN

iTrader: (1)

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.

nitrodude

iTrader: (8)

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

EdwardN

iTrader: (1)

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.

rmdhawaii

iTrader: (4)

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!"

asw7576

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

DaRollaRacer

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

mtveten

iTrader: (29)

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

Warmac

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.

Warmac

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?

rmdhawaii

iTrader: (4)

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

rmdhawaii

iTrader: (4)

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

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. As my knowledge grows, I have a tendency of changing my mind about what I want to get. 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.

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.

rmdhawaii

iTrader: (4)

Hmmmm... More interesting info...

Check out the graph guys....

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

mxwrench!

Osiris 75

iTrader: (18)

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.

DaRollaRacer

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