Difference between revisions of "Calculating port timing"

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This is a short article about calculating port timing. This is copied and pasted off the Technical board, and it's about advancing timing. It also includes a helpful tool.
+
{{TOCright}}
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This is a short article about calculating [[port timing]]. This is copied and pasted off the Technical board, and it's about advancing timing. It also includes a helpful tool.
  
 +
Advancing the timing is pretty simple. You just need to calculate the current timing.
  
Advancing timing is pretty simple. You just need to calculate the current timing
+
==Calculations==
  
 +
<blockquote>D=(180-cos^-1((T^2+R^2-L^2)/(2*R*T)))*2 </blockquote>
  
D=(180-cos^-1((T^2+R^2-L^2)/(2*R*T)))*2
+
<blockquote> T=R+L+C-E </blockquote>
  
 +
*R is stroke divided by 2
 +
*L is the [[connecting rod]] length (90mm in a [[Puch]])
 +
*C is the distance of the crown of the [[piston]] to the top of the [[cylinder]] in [[TDC]] (Deckheight)
 +
*E is the distance between the [[port]] and the top edge of the cylinder
  
T=R+L+C-E
+
Everything is measured in millimeters.
 
 
 
 
R is stroke divided by 2
 
 
 
L is the conrod length (90mm in a [[Puch]])
 
 
 
C is the distance of the crown of the [[piston]] to the top of the [[cylinder]] in [[TDC]] (Deckheight)
 
 
 
E is the distance between the [[port]] and the top edge of the cylinder
 
 
 
 
 
Everything is measured in millimeters  
 
 
 
  
 
And then fill in the desired timing and reverse-calculate it.
 
And then fill in the desired timing and reverse-calculate it.
 +
==For E50's==
 +
Here's the easy way out for people with the Puch [[E50]] engine.
  
 +
{| border="1" cellspacing="0" cellpadding="8" width="45%" style="background-color: #F5F5F5; border: solid 2px #FFD700;"
 +
!colspan="2"|E50 port height (mm) in relation to timing (degrees)
 +
|-
 +
|
 +
{| border="1" cellspacing="0" cellpadding="8" align="center" style="background-color: #FFFFFF"
 +
|-
 +
|'''Millimeters''' ||'''Degrees'''
 +
|-
 +
|21.5 ||193.7
 +
|-
 +
|22 ||191.1
 +
|-
 +
|22.5 ||188.5
 +
|-
 +
|23 ||185.9
 +
|-
 +
|23.5 ||183.2
 +
|-
 +
|24 ||180.6
 +
|-
 +
|24.5 ||177.9
 +
|-
 +
|25 ||175.2
 +
|-
 +
|25.5 ||172.5
 +
|-
 +
|26 ||169.8
 +
|-
 +
|26.5 ||167
 +
|-
 +
|27 ||164.3
 +
|-
 +
|27.5 ||161.5
 +
|}
 +
|
 +
{| border="1" cellspacing="0" cellpadding="9" align="center" style="background-color: #FFFFFF"
 +
|-
 +
|'''Millimeters''' ||'''Degrees'''
 +
|-
 +
|28 ||158.6
 +
|-
 +
|28.5 ||155.8
 +
|-
 +
|32 ||134.7
 +
|-
 +
|32.5 ||131.4
 +
|-
 +
|33 ||128.2
 +
|-
 +
|33.5 ||124.8
 +
|-
 +
|34 ||121.4
 +
|-
 +
|34.5 ||117.9
 +
|-
 +
|35 ||114.3
 +
|-
 +
|35.5 ||110.5
 +
|-
 +
|36 ||106.7
 +
|-
 +
|36.5 ||102.8
 +
|}
 +
|}
  
Or just take the easy way out...
+
:(Courtesy of [http://www.puchforum.net Puchforum.net])
 
 
 
 
Port height in relation to timing in a Puch [[E50]] engine. All in MM and degrees.
 
 
 
 
 
21,5 - 193,7
 
 
 
22 - 191,1
 
 
 
22,5 - 188,5
 
 
 
23 - 185,9
 
 
 
23,5 - 183,2
 
 
 
24 - 180,6
 
 
 
24,5 - 177,9
 
 
 
25 - 175,2
 
 
 
25,5 - 172,5
 
 
 
26 - 169,8
 
 
 
26,5 - 167
 
 
 
27 - 164,3
 
 
 
27,5 - 161,5
 
 
 
28 - 158,6
 
 
 
28,5 - 155,8
 
 
 
32 - 134,7
 
 
 
32,5 - 131,4
 
 
 
33 - 128,2
 
 
 
33,5 - 124,8
 
 
 
34 - 121,4
 
 
 
34,5 - 117,9
 
 
 
35 - 114,3
 
 
 
35,5 - 110,5
 
 
 
36 - 106,7
 
 
 
36,5 - 102,8
 
 
 
 
 
(Courtesy of Puchforum.net)
 
 
 
 
 
There are also tools you can use.  Like [http://home.planet.nl/~moelk037/Jaap's%20Puch%20Calculator.exe Jaap's Puch Calculator].
 
 
 
 
 
 
 
Quick translation of the program:
 
 
 
 
 
Spoel-/uitlaattiming = Transfer-/Exhausttiming
 
 
 
 
 
Timing (In degrees)
 
 
 
Portheight (in mm)
 
 
 
Deckheight (in mm)
 
 
 
Stroke (43mm standard)
 
 
 
Con. rod length (90mm standard)
 
 
 
 
 
 
 
Inlaattiming = intake timing
 
 
 
 
 
Timing (in degrees)
 
 
 
Intakeheight (in mm)
 
 
 
Pistonlength (At the longest point, in mm)
 
 
 
Deck (in mm)
 
 
 
Stroke (43mm standard)
 
 
 
Con. rod length (90mm standard)
 
 
 
 
 
 
 
Poortbreedte = Port width
 
 
 
 
 
True width (in mm)
 
 
 
Portmap width (in mm)
 
 
 
Bore (in mm)
 
 
 
 
 
 
 
Snelheid, toeren = Speed, RPM
 
 
 
 
 
Speed (In KM/H)
 
 
 
RPM
 
 
 
Front sprocket (In number of teeth)
 
 
 
Rear sprocket (in number of teeth)
 
 
 
Internal gearing (Leave it the way it is for Puch)
 
 
 
Tire radius (In meters. The length that the tire rolls for one revolution, if you catch my drift)
 
 
 
 
 
 
 
Informatie = Information
 
  
 +
==Other Tools==
 +
There are also tools you can use, like [http://home.planet.nl/~moelk037/Jaap's%20Puch%20Calculator.exe Jaap's Puch Calculator]. Quick translation of the program:
  
Place the radio button at the variable that's unknown. (The variable you want to calculate)
+
*''Spoel-/uitlaattiming'' = Transfer-/Exhaust timing
 +
:Timing (In degrees)
 +
:Port height (in mm)
 +
:Deck height (in mm)
 +
:Stroke (43mm standard)
 +
:Con. rod length (90mm standard)
  
Oh and for an automatic, useable timings are:
+
*''Inlaattiming'' = intake timing
 +
:Timing (in degrees)
 +
:Intake height (in mm)
 +
:Piston length (At the longest point, in mm)
 +
:Deck height (in mm)
 +
:Stroke (43mm standard)
 +
:Con. rod length (90mm standard)
  
 +
*''Poortbreedte'' = Port width
 +
:True width (in mm)
 +
:[[Port map]] width (in mm)
 +
:Bore (in mm)
  
Exhaust timing:
+
*''Snelheid, toeren'' = Speed, RPM
 +
:Speed (In KM/H)
 +
:[[RPM]]
 +
:Front [[sprocket]] (In number of teeth)
 +
:Rear sprocket (in number of teeth)
 +
:Internal [[gearing]] (Leave it the way it is for Puch)
 +
:Tire radius (in meters -- the length that the tire rolls for one revolution, if you catch my drift)
  
150-160: Low exhaust timing. Torque, not high revs.
+
*''Informatie'' = Information
 +
:Place the radio button at the variable that's unknown. (The variable you want to calculate)
  
160-170: Very useable timing. Good torque and some power in the mid to high range.
+
==For Automatics==
 +
For an automatic, usable timings are:
  
170-180: High exhaust timing. Very limited use. Almost no torque with a narrow powerband at high revs.
+
*Exhaust timing:
 
+
**150-160: Low exhaust timing. Torque, not high revs.
 
+
**160-170: Very usable timing. Good torque and some power in the mid to high range.
For the intake timing, calculate the blowdown.
+
**170-180: High exhaust timing. Very limited use. Almost no torque with a narrow [[power band]] at high revs.
 
 
 
 
Blowdown of 25: Low blowdown. Wide powerband with little peak. Rides well for everyday use.
 
 
 
30: Pretty narrow powerband. Low power at low revs, higher power at high revs. You need a well tuned clutch to be able to ride with a blowdown as high as this, or it will stall out.
 
 
 
35+: Way too high for an automatic. This is only rideable on a well tuned variomatic or shifter engine.
 
  
 +
*For the intake timing, calculate the blowdown.
 +
**Blowdown of 25: Low blowdown. Wide power band with little peak. Rides well for everyday use.
 +
**Blowdown of 30: Pretty narrow power band. Low power at low revs, higher power at high revs. You need a well tuned clutch to be able to ride with a blowdown as high as this, or it will stall out.
 +
**Blowdown of 35+: Way too high for an automatic. This is only ridable on a well tuned variomatic or shifter engine.
  
 
As a rule of thumb, a blowdown higher then 28 isn't for everyday use on an automatic. Don't go higher than 28 if you don't know what you're doing ;)
 
As a rule of thumb, a blowdown higher then 28 isn't for everyday use on an automatic. Don't go higher than 28 if you don't know what you're doing ;)
 
  
 
Good luck and have fun.
 
Good luck and have fun.

Revision as of 16:47, 17 August 2008

This is a short article about calculating port timing. This is copied and pasted off the Technical board, and it's about advancing timing. It also includes a helpful tool.

Advancing the timing is pretty simple. You just need to calculate the current timing.

Calculations

D=(180-cos^-1((T^2+R^2-L^2)/(2*R*T)))*2

T=R+L+C-E

  • R is stroke divided by 2
  • L is the connecting rod length (90mm in a Puch)
  • C is the distance of the crown of the piston to the top of the cylinder in TDC (Deckheight)
  • E is the distance between the port and the top edge of the cylinder

Everything is measured in millimeters.

And then fill in the desired timing and reverse-calculate it.

For E50's

Here's the easy way out for people with the Puch E50 engine.

E50 port height (mm) in relation to timing (degrees)
Millimeters Degrees
21.5 193.7
22 191.1
22.5 188.5
23 185.9
23.5 183.2
24 180.6
24.5 177.9
25 175.2
25.5 172.5
26 169.8
26.5 167
27 164.3
27.5 161.5
Millimeters Degrees
28 158.6
28.5 155.8
32 134.7
32.5 131.4
33 128.2
33.5 124.8
34 121.4
34.5 117.9
35 114.3
35.5 110.5
36 106.7
36.5 102.8
(Courtesy of Puchforum.net)

Other Tools

There are also tools you can use, like Jaap's Puch Calculator. Quick translation of the program:

  • Spoel-/uitlaattiming = Transfer-/Exhaust timing
Timing (In degrees)
Port height (in mm)
Deck height (in mm)
Stroke (43mm standard)
Con. rod length (90mm standard)
  • Inlaattiming = intake timing
Timing (in degrees)
Intake height (in mm)
Piston length (At the longest point, in mm)
Deck height (in mm)
Stroke (43mm standard)
Con. rod length (90mm standard)
  • Poortbreedte = Port width
True width (in mm)
Port map width (in mm)
Bore (in mm)
  • Snelheid, toeren = Speed, RPM
Speed (In KM/H)
RPM
Front sprocket (In number of teeth)
Rear sprocket (in number of teeth)
Internal gearing (Leave it the way it is for Puch)
Tire radius (in meters -- the length that the tire rolls for one revolution, if you catch my drift)
  • Informatie = Information
Place the radio button at the variable that's unknown. (The variable you want to calculate)

For Automatics

For an automatic, usable timings are:

  • Exhaust timing:
    • 150-160: Low exhaust timing. Torque, not high revs.
    • 160-170: Very usable timing. Good torque and some power in the mid to high range.
    • 170-180: High exhaust timing. Very limited use. Almost no torque with a narrow power band at high revs.
  • For the intake timing, calculate the blowdown.
    • Blowdown of 25: Low blowdown. Wide power band with little peak. Rides well for everyday use.
    • Blowdown of 30: Pretty narrow power band. Low power at low revs, higher power at high revs. You need a well tuned clutch to be able to ride with a blowdown as high as this, or it will stall out.
    • Blowdown of 35+: Way too high for an automatic. This is only ridable on a well tuned variomatic or shifter engine.

As a rule of thumb, a blowdown higher then 28 isn't for everyday use on an automatic. Don't go higher than 28 if you don't know what you're doing ;)

Good luck and have fun.

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