Thread: 20VE vs N1 vs 20V spring pressures

Robert, direct quotation from FSM:

20VE open pressure:
449..492,5 N == 101..110 lbs - at 25,44 mm spring height

N1 open pressure:
458..486 N == 103..109 lbs - at 24,4 mm spring height

My numbers are average form min to max and they are PER INCH both.

Yes, but you forgot about the inner springs. You need to add 166-188 N for 20VE and 168-178 N for the N1.



Only true for the intake valves. The exhaust valves are the same for both 20VE/16VE and N1.

Intake Valve Stem Diameter:
20VE/16VE=5.965 -5.98 mm
N1= 4.55-4.65 mm

Intake Valve Diameter:
20VE/16VE= 34-34.3 mm
N1= 33.6-33.9 mm



N1 intake valve is shorter by .1mm.

Exhaust valves are the same for all the 20VE/16VE/N1.

No, the base of the N1 Valve stem is narrower. Its narrow because of the gradiation cut to the base of the intake valve. Less seat pressure means less chance of the valve stem fracturing.

Seat pressure affects only the final closing of the spring on the very last portion of the cam rotation - ie: end cycle of the lobe. Increased friction comes from pressure at half inch measurements - and varies with the material or compound of the steel used in the valve spring. Loosing horespower will only come from lift pressure.

Outofsight has posted info and spec on the valve shape and size straight from the workshop manual to show the base of the N1 valve stem is narrower than a regular 16VE stem.

Having a lower spring pressure when open also reduces ovaling of the valve stem and excess valve guide wear.

Also for reference sake has anyone got details of ID/OD of the springs, and installed vs uncompressed height of the springs?

Robert, thanks for tip. Damn my Japanese is really bad! ha-ha
The inner springs data in FSM is at another spring height. Does it mean inner spring sits 5mm deeper because of retainer relief?

Ok, than we got next numbers:

20VE/16VE
Valve closed (seat pressure): 64 lbs
Valve open at 12mm (open pressure): 145 lbs

N1
Valve closed (seat pressure): 45 lbs
Valve open at 12mm (open pressure): 150 lbs

20V values are the same.. Because they have just one spring.
Valve closed (seat pressure): 47 lbs
Valve open at 12mm (open pressure): 158 lbs

So 20V springs are stiffest at valve open and softest at seat... hmmm

No, the inner spring sits higher. It's a shorter spring than the outer spring.

20VE/16VE
Inner Spring free/uncompressed length: 42.02 mm
Outer: 48.49 mm

Installed Length
Inner: 32 mm
Outer: 37 mm

Max Open Length
Inner:20.44 mm
Outer: 25 mm

N1 Springs
Free/Uncompressed Length
Inner: 38.76 mm
Outer: 44.50 mm

Installed Length
Inner: 32 mm
Outer: 37 mm

Max Open Length
Inner: 19.64 mm
Outer: 24.64 mm


20VE/16VE Spring OD/ID
Outer Spring: 1.145" OD, .830" ID
Inner Spring: .797" OD, .615" ID

Interesting idea.. If I can put 20VE inner springs inside 20V outer springs, it will come to 64lbs seat pressure and 199lbs open pressure. Cheap upgrade for me?

Some photos...

your figures might be slightly off as the inner spring might be more preloaded at seat pressure when combined with the 20v spring over the 20ve outer.

However it might work. First thing i would check is the compressed height of the 20ve inner and 20v outer. Looking at the pics it doesn't look like you will run into any trouble at all, never hurts to double check though. I assume you have placed the 20ve inner inside the 20v outer and it fits with the retainer in place? Looking at the pics it looks like it will.

You might find the rate of Pressure will increase dramatically using the 16/20VE innner spring combined with the 20v outer spring.

The pressure difference from .5" to 1" on both combinations will probably ramp up quite more with your idea. This could be a good thing for high high RPM work.

Great idea - i will price the 20v springs in the morning. Might be a worthwhile cheap upgrade!!