Yamaha 62T/61X Displacement vs. Bore/Stroke Combinations

N

njfl

X-H2
I keep an Excel spread sheet that takes bore and stroke as variables and calculates displacement in ccs. Here it is. There is a lot to be learned from this. First of all, look at the trends. Each 1mm increment of bore gives a lot more increase in displacement than a 1mm increase in stroke.

For those of you who want to play around with your own spread sheet, the equation is:

displacement = 0.001*2*stroke*3.1415927*(bore/2)^2

Enjoy.


HTML: 
Displacement vs. Bore and Stroke Combinations for Yamaha 62T/61X-Based Motors																		

All bore and stroke units in millimeters (mm)


Bore		OEM	cc		+4mm	cc		+5mm	cc		+6mm	cc		+8mm	cc		+10mm	cc


81.0		68	701		72	742		73	752		74	763		76	783		78	804
81.5		68	709		72	751		73	762		74	772		76	793		78	814
82.0		68	718		72	760		73	771		74	782		76	803		78	824
82.5		68	727		72	770		73	780		74	791		76	813		78	834
83.0		68	736		72	779		73	790		74	801		76	822		78	844
83.5		68	745		72	789		73	799		74	810		76	832		78	854
84.0		68	754		72	798		73	809		74	820		76	842		78	865
84.5		68	763		72	808		73	819		74	830		76	852		78	875
85.0		68	772		72	817		73	828		74	840		76	863		78	885
85.5		68	781		72	827		73	838		74	850		76	873		78	896
86.0		68	790		72	836		73	848		74	860		76	883		78	906
86.5		68	799		72	846		73	858		74	870		76	893		78	917
87.0		68	808		72	856		73	868		74	880		76	904		78	927
87.5		68	818		72	866		73	878		74	890		76	914		78	938
88.0		68	827		72	876		73	888		74	900		76	924		78	949
88.5		68	837		72	886		73	898		74	910		76	935		78	960
89.0		68	846		72	896		73	908		74	921		76	946		78	970
89.5		68	856		72	906		73	919		74	931		76	956		78	981
90.0		68	865		72	916		73	929		74	942		76	967		78	992
90.5		68	875		72	926		73	939		74	952		76	978		78	1003
91.0		68	885		72	937		73	950		74	963		76	989		78	1015
91.5		68	894		72	947		73	960		74	973		76	999		78	1026
92.0		68	904		72	957		73	971		74	984		76	1010		78	1037
 
N

njfl

X-H2
I was originally going to do that, but the "Manage Attachments" function does not allow .xls file extensions. If someone can tell me how/where to post it I will.
 
michael950

michael950

for me to POOP on!
Location
Houston, TX
cookerq62 said:
plug this =(((A2/2)^2)*PI()*B2*C2)/1000 into excel in cell D2

cell A2=bore
cell B2=stroke
cell C2= the number of cylinders


I don't know how do upload an excel file or I would just attach it
Click to expand...

From another thread.


displacement.JPG
 
Last edited:
N

njfl

X-H2
Someone send me a PM with your email and I'll send you the .xls file and you can upload it somewhere and post the link.

I asked Superjett if vBulletin would support real-time html calculators in a thread but he said no. Plus, he correctly pointed out that there are a ton of displacement calculators on the web.

The point of listing all of the combinations in tabular format was mainly to show things like how much more gain you get from a mm of bore increase versus a mm of stroke increase and such.
 
N

njfl

X-H2
EightySeven550 said:
Just change the file extension to .jpg and tell people to change it back when they download it.
Click to expand...

I tried that in the past and just tried again. vBulletin recognizes that it is not a valid image file. EightySeven550 PM me your email and I will send it to you to figure out how/where to put it.
 
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Waternut

Waternut

Customizing addict
Location
Macon, GA
I don't want to hi-jack the thread but I figured this was going to be a power related displacement vs stroke discussion. I always thought that the bigger the stroke, the bigger the torque, but lower the max rpms. I'm sure there are other variables but what would be the performance difference between the stock stroke 85mm bore 772cc, +4 stroker 82.5mm bore 770cc, and the +5mm stroke 82mm bore 771cc? I can't see the displacement itself making any difference between the three but surely that actual performance would be different.
 
SUPERTUNE

SUPERTUNE

Race Gas Rules
Location
Clearwater Fl.
jfw432 said:
I don't want to hi-jack the thread but I figured this was going to be a power related displacement vs stroke discussion. I always thought that the bigger the stroke, the bigger the torque, but lower the max rpms. I'm sure there are other variables but what would be the performance difference between the stock stroke 85mm bore 772cc, +4 stroker 82.5mm bore 770cc, and the +5mm stroke 82mm bore 771cc? I can't see the displacement itself making any difference between the three but surely that actual performance would be different.
Click to expand...

Yes, longer strokes can make more torque for a Superjet/Waveblaster
Long stroke, long rod small bore will make the best hp at the same cc due to the leverage of the stroke and the ease to fill a smaller bore more efficiently.
But keep in mind of all the porting configurations when adding stroker cranks, this can kill you if you don't get it right to fit the combination.
 
ItsRixter

ItsRixter

SoCal Wav Jumping shiznit
Location
Sunny Diego
On the topic of bore and stroke can someone explain a little on compression?
Why is that my sj 701 with 185 psi runs on 91 octane yet my 760 motor with 185 needs 100 octane? Look at the ADA racing site...noticewhen the 760 domes hit 185 psi they list 98 octane. Yet on the 701 head the domes for 185 list 91 octane.
 
#ZERO

#ZERO

Beach Bum
Location
Florida - U.S.A.
ItsRixter said:
On the topic of bore and stroke can someone explain a little on compression?
Why is that my sj 701 with 185 psi runs on 91 octane yet my 760 motor with 185 needs 100 octane? Look at the ADA racing site...noticewhen the 760 domes hit 185 psi they list 98 octane. Yet on the 701 head the domes for 185 list 91 octane.
Click to expand...
The exhaust port roof is 2mm taller on the 760 cylinder which causes the cranking compression to be lower and the dynamic compression to be higher.
 
masterblaster

masterblaster

X-H2
SUPERTUNE said:
Yes, longer strokes can make more torque for a Superjet/Waveblaster
Long stroke, long rod small bore will make the best hp at the same cc due to the leverage of the stroke and the ease to fill a smaller bore more efficiently.
But keep in mind of all the porting configurations when adding stroker cranks, this can kill you if you don't get it right to fit the combination.
Click to expand...


interesting,how much does torque come up with the setup mentioned above,with the longer stroke,long rod setup if you add to it a big bore 85 mill flat top piston?
 
Lucifer

Lucifer

Jet Junkie
Location
Croydon PA
A simple displacement formula

Hi All.
I came across this page while creating my first excel file ever. Its a simple displacement calculator.
Here is the formula I use for calculating engine displacement.
As it consists of a simple product, the math is easier to program in a spreadsheet, Its easy to punch into a calculator and its easy to remember.
It works regardless of the unit of measurement entered, ie. inches or cm or mm, as long as its uniform for bore and stroke.
Also, it calculates displacement to a very precise number. Useful in many ways.


bore * bore * stroke * .7865 * (number of cylinders) = displacement
The result is the displacement multiplied by 1000. For the answer, Eliminate the last 3 digits and substitute a decimal point for the separator.

For example, on the 61x or 62t motor: 81mm * 81mm * 68mm * .7865 * 2 = 701, 790.804 mm3

As we don't really need such an exact figure, multiply by .001 and format the result cell to display 2 decimal places and not display the thousand separator to eliminate the extra decimals.

81mm * 81mm * 68mm * .7865 * 2 *.001 = 701.79 mm3

So my formula looks like this in Excel
bore * bore * stroke * .7865 * 2 * .001 = product

Hope this helps make things easier for you all
Lucifer
 
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