VALVE SPRING QUESTION

[Type 4 Unleashed]

Hi folks

What kinda spring pressures are needed for a Turbo ? Seat pressure & over the nose.

Cam .500" valve lift.

Boost, max 15psi


Thanks

[seabeebuggy]

Hell I just uses single high rev springs. hit 25lbs the other day. 15 lbs of boost will not budge the valve spring.

[marcotheturbosteamengine]

if the motor was N/A what springs would you use,concidering the rpm it would turn?
once figered out , take your desired max boost and X 2, then add to your seat presure
eg. boost 15lb X2 = 30lb
seat N/A 150lb + 30lb= 180lb seat presure turboed!
good luck
marco mansi.......

[Wally]

Hehe, nice post Richard

Thanks Marco!
Where are you located these days? and: how are you and how is the grey bug with the 18" Classic II's ?

[Piledriver]

Marco previously recommended the SCAT duals to me for one of my projects, but the typical Manton dual springs CB and Jake sell have about the same specs.

IIRC one of Marcos motors didn't have enough spring, and the effective "redline" was boost variable, something like floating at ~5K at 15 PSI? (designed for >8K @30PSI)

[Type 4 Unleashed]

Thanks Marco

I kinda figured it would be something like that. I have read up on Turbo installs, there have been references to more seat pressure, to help valve bounce, but nothing about keeping the valves from floating, or nothing really concrete.

[70dragbug]

Marco, thanks for the answer! I remember reading your post on your wbx valve floating at 5900rpm due to the springs being too weak.I will be running a 50mm intake valve - so I figured that the surface of the valve plays an important role.15 psi on a 44mm valve isn´t as much pressure(force) as 15 psi on a 50mm valve - even if there were no weight difference between the two valves.More than likely I will have Titanium valves.

[jonas_linder]

Actually, the force, in newton, from there air is

F = P * A

Where:
F is the force in N (newton)
P is the pressure in pascal (100kpa = 100 000 kilopasscal = 1 bar of
boost)
A is the area in m2

The force in kg is approx F/10

1 bar is 14.7psi

15 psi of boost is 100*15/14.7=102kpascal
The area of a circledisc is A = pi*r^2
Where pi is approx. 3.14
and r is the radius

Let's calculate one example

Let's say you need 120lbs on a 40mm valve to rev 6500 rpm as an N/A
engine, than you need the equal amount of pressure under full boost!

So for 1 bar of boost(14.7psi) and 40mm valve the force by the boost is
F = 100 000*3.14*0,02^2 = 126N = 12.8kg = 28lbs!!!!!

With a 50mm valve
F = 100 000*3.14*0.025^2 = 196N = 20kg = 44lbs!!

1 pound = 0.45359237 kilograms
120 pounds = 54.4310844 kilograms

For you that don't use a logic measuringsystem:

1 psi = 1 pound per square inch
40mm valve = 1.574" valve (40mm)

Pressure from 14.7psi boost(in lbs) is

F = 14.7*3.14*0.7874^2 = 28lbs!!

(0.787 is the radius of the valve)

With 2 bar of boost the decrease in seatpressure is twice that.. 56lbs.. if you start with 120lbs of seat pressure it ain't much left!

This is just a raw calculation.. the whole valve don't "see" this pressure (valve steam, valve seating area, etc)

/Jonas

ps. the weigth has nothing to do with the decrease in seat pressure done by the boost! ds.

[Turboval]

Actually, the force, in newton, from there air is

F = P * A

Where:
F is the force in N (newton)
P is the pressure in pascal (100kpa = 100 000 kilopasscal = 1 bar of
boost)
A is the area in m2

The force in kg is approx F/10

1 bar is 14.7psi

15 psi of boost is 100*15/14.7=102kpascal
The area of a circledisc is A = pi*r^2
Where pi is approx. 3.14
and r is the radius

Let's calculate one example

Let's say you need 120lbs on a 40mm valve to rev 6500 rpm as an N/A
engine, than you need the equal amount of pressure under full boost!

So for 1 bar of boost(14.7psi) and 40mm valve the force by the boost is
F = 100 000*3.14*0,02^2 = 126N = 12.8kg = 28lbs!!!!!

With a 50mm valve
F = 100 000*3.14*0.025^2 = 196N = 20kg = 44lbs!!

1 pound = 0.45359237 kilograms
120 pounds = 54.4310844 kilograms

For you that don't use a logic measuringsystem:

1 psi = 1 pound per square inch
40mm valve = 1.574" valve (40mm)

Pressure from 14.7psi boost(in lbs) is

F = 14.7*3.14*0.7874^2 = 28lbs!!

(0.787 is the radius of the valve)

With 2 bar of boost the decrease in seatpressure is twice that.. 56lbs.. if you start with 120lbs of seat pressure it ain't much left!

This is just a raw calculation.. the whole valve don't "see" this pressure (valve steam, valve seating area, etc)

/Jonas

ps. the weigth has nothing to do with the decrease in seat pressure done by the boost! ds.

A goldstar for Jonas

[marcotheturbosteamengine]

Actually, the force, in newton, from there air is

F = P * A

Where:
F is the force in N (newton)
P is the pressure in pascal (100kpa = 100 000 kilopasscal = 1 bar of
boost)
A is the area in m2

The force in kg is approx F/10

1 bar is 14.7psi

15 psi of boost is 100*15/14.7=102kpascal
The area of a circledisc is A = pi*r^2
Where pi is approx. 3.14
and r is the radius

Let's calculate one example

Let's say you need 120lbs on a 40mm valve to rev 6500 rpm as an N/A
engine, than you need the equal amount of pressure under full boost!

So for 1 bar of boost(14.7psi) and 40mm valve the force by the boost is
F = 100 000*3.14*0,02^2 = 126N = 12.8kg = 28lbs!!!!!

With a 50mm valve
F = 100 000*3.14*0.025^2 = 196N = 20kg = 44lbs!!

1 pound = 0.45359237 kilograms
120 pounds = 54.4310844 kilograms

For you that don't use a logic measuringsystem:

1 psi = 1 pound per square inch
40mm valve = 1.574" valve (40mm)

Pressure from 14.7psi boost(in lbs) is

F = 14.7*3.14*0.7874^2 = 28lbs!!

(0.787 is the radius of the valve)

With 2 bar of boost the decrease in seatpressure is twice that.. 56lbs.. if you start with 120lbs of seat pressure it ain't much left!

This is just a raw calculation.. the whole valve don't "see" this pressure (valve steam, valve seating area, etc)

/Jonas

ps. the weigth has nothing to do with the decrease in seat pressure done by the boost! ds.

THANKS Jonas!

as i said:
if the motor was N/A what springs would you use,concidering the rpm it would turn?
once figered out , take your desired max boost and X 2, then add to your seat presure
eg. boost 15lb X2 = 30lb
seat N/A 150lb + 30lb= 180lb seat presure turboed!

the quick way to work it out

[turbo_bob]

What kinda spring pressures are need for a Turbo ? Seat pressure & over the nose.
Cam .500" valve lift.
Boost, max 15psi

I have .513 lift at the valve, 40 X 37 SS valves, dual VW springs shimed up .067 to colibind. The spring pressure is around 300 psi at full lift. I use up to 24 PSI boost.

[70dragbug]

Ok Thanks guys - those are figures I can work with.

[jonas_linder]

this isn't exactly correct, please take this as a very rough estimate (big overshot)