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Old 09-18-2006, 07:26 PM   #1
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Bore vs Stroke vs Displacement

Code:
Engine               Bore  Stoke  Disp.
------              ----- ------  -----
Team Orion Wasp Rev 13.80  14.00  2.094
OS TZ Speed Tuned   13.80  14.00  2.094
OS TZ               13.80  14.00  2.094
JP Racing FX-03     13.80  14.04  2.100
Novarossi LL3       13.70  14.25  2.101
Sirio STI           14.00  13.70  2.109
GRP Ninja           14.02  13.79  2.129
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.
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Old 09-18-2006, 08:20 PM   #2
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Quote:
Originally Posted by rmdhawaii
Code:
Engine               Bore  Stoke  Disp.
------              ----- ------  -----
Team Orion Wasp Rev 13.80  14.00  2.094
OS TZ Speed Tuned   13.80  14.00  2.094
OS TZ               13.80  14.00  2.094
JP Racing FX-03     13.80  14.04  2.100
Novarossi LL3       13.70  14.25  2.101
Sirio STI           14.00  13.70  2.109
GRP Ninja           14.02  13.79  2.129
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.
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.
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Old 09-18-2006, 08:59 PM   #3
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Does it mean that a bigger bore will give you more torque? Or am I looking at it the wrong way?
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Old 09-18-2006, 09:18 PM   #4
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Quote:
Originally Posted by nitrodude
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.
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Old 09-18-2006, 10:10 PM   #5
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Quote:
Originally Posted by EdwardN
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!"
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Old 09-18-2006, 11:42 PM   #6
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Quote:
Originally Posted by EdwardN
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.
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
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Old 09-19-2006, 09:03 AM   #7
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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
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Old 09-19-2006, 10:39 AM   #8
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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?

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Old 09-19-2006, 11:46 AM   #9
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Quote:
Originally Posted by mtveten
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?


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.
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Old 09-19-2006, 11:54 AM   #10
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Quote:
Originally Posted by EdwardN
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.
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?
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Old 09-19-2006, 01:09 PM   #11
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Mark: This is what Uriah had to say...

Quote:
Originally Posted by Grinder
The LL3 will have a torquier feel than the LS3. The LS3 powerband comes on smoother than the LL3. The LS3 is happier at high revs, than the LL3. LL3 can be a little trickier to tune, and seems to run slightly warmer than LS3. Overall performance, I would say both are similar, just different powerbands. Both are extremely fast.
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Old 09-19-2006, 01:43 PM   #12
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Quote:
Originally Posted by 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
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.
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Old 09-19-2006, 02:38 PM   #13
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Hmmmm... More interesting info...

Code:
Engine               Bore  Stoke  Disp.
------              ----- ------  -----
Axial.12RR Spec 1   13.76  14.00  2.082
Check out the graph guys....

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

mxwrench!
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Old 09-19-2006, 02:53 PM   #14
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Quote:
Originally Posted by rmdhawaii
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.
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.
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Old 09-19-2006, 03:29 PM   #15
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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
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