VG30 valve spring info

[G-E]

Re: Hi-RPM...

BlueThunderZX wrote: My goals is to have reasonable power in 7500-8000RPM. Can you give more info about the 110lb Schneider valve springs??? Is there any "dual-spring" kit for the VG30E(T)?? Thanks

ultra-lightweight pistons will help get you there

[FlawleZ]

Re: Hi-RPM...

[quote]G-E wrote:

My goals is to have reasonable power in 7500-8000RPM. Can you give more info about the 110lb Schneider valve springs??? Is there any "dual-spring" kit for the VG30E(T)?? Thanks
ultra-lightweight pistons will help get you there

As well as anything else that is a part of the rotating assembly. A lightweight crank would be essential in creating the foundation to a lighter, more free reving VG30.

[Jason84NA2T]

j30_vg33et wrote: I talked with Clark about the springs before buying them, and his feeling was the seat pressure was sufficient for 7000rpm using the S2 profile. By running the single spring rather than inner/outers, valvetrain mass goes down, with a corresponding increase in the springs natural frequency (single spring with higher rate). Where the stock springs get into a float resonance by 7k, the single spring is still able to control the valve.
And that's why it's desirable to use double springs, so you don't hit an RPM where the valve springs resonate and then float... The valvetrain mass reduction is minimal because of the motion ratio of the mass of the spring itself. Only maybe 1/4 of the springs' (already fairly small) mass is moving at the same rate as the valve itself.

j30_vg33et wrote: Lastly, running excessive spring pressure only costs power. You want to have just enough to keep the valve against the cam lobe + some extra for longetivity.
It does not cost power, it costs durability. All the PE in a spring is stored and released in a controlled fashon (without slop in the valvetrain) then the only thing that increases is the pressure on the oil film between the lifter-rocker and rocker-valve tip.

j30_vg33et wrote: Why do they require shims?

Actually it's mostly to obtain the correct seat and open pressures from a spring of a given rate. You can shim them more and get more seat pressure if you don't get coil bind.

j30_vg33et wrote: Blowing the valves open?
pi()*(0.827")^2 = 2.15 in2 -> 2.15in2*20lb/in2 = 43 lb against back of the intake valve face. Probably not going to blow open.

43lb when the valve is trying to close fully at high speed. I guess "blowing open" is probably not the best choice of words to describe this occurrence (which by the way is indeed an issue on many engines). It's moreso where they are "held open" or prevented from closing completely at the correct time based on the cam profile.

j30_vg33et wrote: What would be bad is if the exhaust valves were EGRing during the intake stroke. But really, that would be more of a turbo problem (backpressure) than a valve spring thing, IMhO.

There's really nothing you can do about that pressure ratio issue with a setup that is already in place. You're always going to get some reversion, and despite what you can do to minimize it by decreasing the pressure ratio (larger turbine/housing, ported exhaust side, headers) or shortening the amount of time the valve stays open (cam duration), you will always have it on a turbocharged engine. A turbine won't suddenly choke off and cause power to drop at high RPM. The pressure ratio will steadily rise until you lose enough torque to drop power off. You can see that plainly in my dyno graph comparison between 418rwhp and 453rwhp; the little turbine is obviously choking over 20PSI.

The real question is why the sudden dropoff in power over 6700RPM (and the dropoff decreasing in RPM as boost increases). It literally falls almost straight down on the graph at high boost, while it carries it right over 7K at low boost. The real-world test for my engine will be to change out the valve springs and see if I still have the issue. Then again, who knows; it might even be from harmonic effect on the single spring (but to me that makes little sense as the output harmonics should not change much between low/high boost).

[j30_vg33et]

[quote]Jason84NA2T wrote: [quote=j30_vg33et]I talked with Clark about the springs before buying them, and his feeling was the seat pressure was sufficient for 7000rpm using the S2 profile. By running the single spring rather than inner/outers, valvetrain mass goes down, with a corresponding increase in the springs natural frequency (single spring with higher rate). Where the stock springs get into a float resonance by 7k, the single spring is still able to control the valve.
And that's why it's desirable to use double springs, so you don't hit an RPM where the valve springs resonate and then float... The valvetrain mass reduction is minimal because of the motion ratio of the mass of the spring itself. Only maybe 1/4 of the springs' (already fairly small) mass is moving at the same rate as the valve itself.
But what's happening here is that you have two soft springs that are likely to resonate, both at lower frequencies (rpm) that the single stiffer one. You probably get some damping from the two rubbing against each other, but it's still damping motion that you don't want.

Jason84NA2T wrote:

What would be bad is if the exhaust valves were EGRing during the intake stroke. But really, that would be more of a turbo problem (backpressure) than a valve spring thing, IMhO.

...A turbine won't suddenly choke off and cause power to drop at high RPM. The pressure ratio will steadily rise until you lose enough torque to drop power off. You can see that plainly in my dyno graph comparison between 418rwhp and 453rwhp; the little turbine is obviously choking over 20PSI.

The real question is why the sudden

dropoff in power over 6700RPM (and the dropoff decreasing in RPM as boost increases). It literally falls almost straight down on the graph at high boost, while it carries it right over 7K at low boost. The real-world test for my engine will be to change out the valve springs and see if I still have the issue. Then again, who knows; it might even be from harmonic effect on the single spring (but to me that makes little sense as the output harmonics should not change much between low/high boost).

You're right, that'll be a great test. And I agree, valve train harmonics don't sound like the issue as a few pounds of boost aren't likely to have any appreciable effect. RPM is the real driver of the valvetrain stuff.

I disagree however on the backpressure point. What you describe infact sounds like a MassFlow related issue, low boost/high rpm vs. high boost/low rpm. At a point it's the same thing as far as the turbo is concerned. Further, I've seen cases where adding 5psi of boost made no additional power on a turbo restriced application. Depending on the combo, you will litterally run into a "wall" at some point as both the compressor and tubine efficiency's fall off the maps. You're making good power on that s3 turbine. But I bet if you put the GT on you'll make more power, earlier, and later, at the same boost. Plus just plane more with more too.

Time will tell, eh? BTW, how's the MAF install going?

[SATAN]

[quote]j30_vg33et wrote: [quote=Jason84NA2T][quote=j30_vg33et:99507]I talked with Clark about the springs before buying them, and his feeling was the seat pressure was sufficient for 7000rpm using the S2 profile. By running the single spring rather than inner/outers, valvetrain mass goes down, with a corresponding increase in the springs natural frequency (single spring with higher rate). Where the stock springs get into a float resonance by 7k, the single spring is still able to control the valve.
And that's why it's desirable to use double springs, so you don't hit an RPM where the valve springs resonate and then float... The valvetrain mass reduction is minimal because of the motion ratio of the mass of the spring itself. Only maybe 1/4 of the springs' (already fairly small) mass is moving at the same rate as the valve itself.
But what's happening here is that you have two soft springs that are likely to resonate, both at lower frequencies (rpm) that the single stiffer one. You probably get some damping from the two rubbing against each other, but it's still damping motion that you don't want.

Jason84NA2T wrote:

What would be bad is if the exhaust valves were EGRing during the intake stroke. But really, that would be more of a turbo problem (backpressure) than a valve spring thing, IMhO.

...A turbine won't suddenly choke off and cause power to drop at high RPM. The pressure ratio will steadily rise until you lose enough torque to drop power off. You can see that plainly in my dyno graph comparison between 418rwhp and 453rwhp; the little turbine is obviously choking over 20PSI.

The real question is why the sudden

dropoff in power over 6700RPM (and the dropoff decreasing in RPM as boost increases). It literally falls almost straight down on the graph at high boost, while it carries it right over 7K at low boost. The real-world test for my engine will be to change out the valve springs and see if I still have the issue. Then again, who knows; it might even be from harmonic effect on the single spring (but to me that makes little sense as the output harmonics should not change much between low/high boost).

You're right, that'll be a great test. And I agree, valve train harmonics don't sound like the issue as a few pounds of boost aren't likely to have any appreciable effect. RPM is the real driver of the valvetrain stuff.

I disagree however on the backpressure point. What you describe infact sounds like a MassFlow related issue, low boost/high rpm vs. high boost/low rpm. At a point it's the same thing as far as the turbo is concerned. Further, I've seen cases where adding 5psi of boost made no additional power on a turbo restriced application. Depending on the combo, you will litterally run into a "wall" at some point as both the compressor and tubine efficiency's fall off the maps. You're making good power on that s3 turbine. But I bet if you put the GT on you'll make more power, earlier, and later, at the same boost. Plus just plane more with more too.

Time will tell, eh? BTW, how's the MAF install going?[/quote:99507]

I kindof agree. the higher the engine revs the more backpressure you are creating, and therefor the more reversion. I dont have to explain it to you but that extra boost has nowhere to go at higher rpms. Stage 3 is pretty small to be pushing 450hp through.