SJP0tato

iTrader: (7)

In theory, assuming a very low friction environment (which the cam/spring area should be, since it's bathed in oil), shouldn't the hp loss be negligible between light and heavy springs?

Sure it's harder to open a valve with a heavier spring costing hp, but the spring rebounds after opening with more force as well. It'd like comparing the overall work lifting a 10lbs weight 5 feet then letting it drop, vs lifting a 100lbs weight 5 feet then letting it drop (say you're running a turbine or something). In the end the total amount of energy gained/lost from the system in a frictionless environment should be 0 in both cases.

I'm sure there's some additional frictional losses compared to stock, but I bet it's not enough to worry about when debating installing better springs.

BogusSVO

iTrader: (1)

I will look into these springs, what life span have you been getting out of these springs?


The main point will be when the intake valve has reached full lift and is now closing, the spring has to pull the valve closed, through the mass of air flowing into the cylinder, also the intake valve must remain closed during the power stroke and not "blow" open. Now if the intake "blows" open on the exhaust stroke, the exhaust gases will diluite the next intake charge.

Valve float happens when the valve "ramps" of the nose of the cam and slams back onto the back ramp of the cam.

A burnt valve can happen for a few reasons, one of the main ones is not enough contact between the valve face and the valve seat. Not enough heat is transfered from the valve and it burns.

Another common one is the valve or seat distort in shape causing a small opening between the two, then you get the torch effect.

In case of the BP, it will make more friction due to the design of the valve train, sliding the cam lobe over the bucket.

But it is a common design, Mazda, Nissian, Toyota, Ford and Jaguar all have heads that use it.

Common sense, logic and experiance all come into play, Instead of finding a spring that installs at 80lbs, I could find one that installs at 150lbs.

But there is no need for a 150lbs set up,at this time, I have not heard anyone here running 50+ psi of boost and spinning 12,000 RPM

Landrew

iTrader: (2)

Hoping to do some headwork in March/April. Any thing more to say on alternative springs from Crower and Sealed Power? I'd love to get a decent set of slightly stiffer springs for under $175.

hrk

iTrader: (6)

I bought a set from Summit and compared them to the stock 2001 springs. They seem to be similar height and diameter, the material is considerably thicker and they felt much stiffer than stock ones. I had my engine machinist to check the stiffness on his load cell unit with dial gauge height measurement. The load cell was calibrated before testing to his calibration spring.

From Summit info:
Universal:Yes

Installed Height (in):1.570 in.

Seat Pressure at Installed Height (lbs):66 lbs.

Open Height (in):1.180 in.

Open Pressure (lbs):175 lbs.

What was measured:
At installed height of 1.550", the seat pressure was 84 lbs.
At 0.350 compression from installed height (1.200") the seat pressure was 180 lbs

The original stock spring was measured to have seat pressure of 46 lbs at 1.550 height and 118 lbs at compressed 0.350.

The stock valve spring has yellow paint mark on it.

Right now I am waiting to confirm the installed valve height for +1 Supertech valves and then deciding which springs to use.

Landrew

iTrader: (2)

Anyone run the Eibach singles? $180 from Summit. They claim 66 lbs @ 39 mm / 200 lbs @ 27 mm. Lift 12 mm / Bind 24.2 mm. Looks like a middle option in price and pressure from OEM. Would like to hear some comments.

http://performance-suspension.eibach...vs-catalog.pdf

k24madness

iTrader: (6)

So if a spring uses a thicker shim seat (read ST) does that mean spring pressure at full lift is higher than one with a thinner shim (assuming same installed pressure)?

hrk

iTrader: (6)

No, the difference between seat pressure and full lift pressure depends on spring k-value, which is used for determining "stiffness" of spring.
As long as the spring operates within I design operating lengths the spring force is linear depending on the distance it travels. Google hookes law.

To keep the valvespring in this operating mode the length should be kept such that there is no binding of coils at full lift and installed height being longer than free height of the spring. Having couple of mm safety in these lengths would be advisable.

Raisin

iTrader: (2)

Bump from the dead, thought I'd add my findings here:

@ 1.181″ 165lbs
@ 1.200″ 180lbs

Coil bind at 26mm.

I actually ended up returning my set of Sealed Power VS-855 to Summit Racing. I noticed that the surface finish of these valves are very coarse and rough, there is definitely a case of "you get what you pay for here".





You can definitely see the coarse grain structure here:



Not all spring steel is the same, I ended up using a set of Mazdaspeed duals even though there is an exponential cost difference.

thefoos

I didn't see this really addressed here, so I'll take a swing at it.

I prefer simple calcs, and you can look at this very simply from a NA vs boosted situation. It's harder to consider changes in rpm, but that can be done as well, but there are velocity/acceleration/mass considerations to make.

Anyway, if you know your valve head area, you can simply consider this a pressure force calculation.

Assuming vacuum as an NA was 15 inHg (7.4 psi vac) and then you go turbo and boost to 15 psig. For sake of argument, lets assume the valve head area is 1 sq in (I don't know the valve size, forgive me, I'm new to miatas).

The calc would be this simple: (7.4+15) * 1 = 22.4 lbs

So in this case, to balance everything out, all else being equal, you'd want to add 20-25 lbs to your spring load.

This of course is ignoring all sorts of other potential effects and impacts, and over simplifying. But it beats guessing.

This would be for the intake side. You'd also want to consider that exhaust pressure between the head and turbine could be double that of the intake manifold pressure. In really small turbos, it could be triple.

Raisin

iTrader: (2)

An interesting article I stumbled across tonight: Beehive Springs Sound Great, But Will They Work For You? - EngineLabs

Although the article really is discussing the benefits of using a beehive design spring, I think there is some information to take away.

One being that seat pressure is being minimized as much as possible with a beehive spring, lowering the amount of stress that the valvetrain sees. The shape of the beehive spring is supposed to help with valve acceleration compared to a conventional style spring based on the shape of the coils near the top.

This could be related to the discussion of single spring vs. dual springs in our Miata heads, with the common dual setup offered by Supertech. I read a lot of discussion on the easy choice being the Supertech duals, but no real math behind it; just the fact that it worked well for the last guy therefore was good stuff.

Resonance in the valvetrain is also briefly discussed. They make a mention of the ovate wire used for spring steel material to counteract the resonance encountered with high rpm frequencies. What was more interesting though was that they mention choosing an installed height as close to coilbind as possible. I think general rule of thumb for installed height is determining the amount of lift, give or take a few mm so long as the spring does not bind at this height installed. This means that a shorter spring which has been shimmed to the appropriate height can resonate less than one which has not been installed close to coilbind.

karlou426hemi

+1 here on the zvs855 from summit. revving to 9000 and after two years of drag racing everything still going strong....

Rallas

iTrader: (9)

Can you install stiffer valve springs on the 94-97 HLA heads? I have things torn apart and it wouldn't be that much more work to get in there and upgrade the springs.

kmvguy

Any update on these BC springs?
Seems like summit is not selling zvs855 anymore, are there any good alternative?

BlackBandit

iTrader: (2)

Good read.

I was wondering if the Eibach EVS Valve Spring Set with 75lbs was over kill with dual springs and Titanium retainers?

Even though the supertech is what is highly recommended on this site for rebuilds and they are significantly cheaper from my search 55 dollar difference.

I will be using a fluctuating psi for different purpose in the boost application for street, autocross, and track. I am going to use upwards of 8 to 12 for autocross and +20psi track.

karlou426hemi

zvs855. 32psi 9000rpm last year for a full drg season no problems at all

slmhofy

iTrader: (5)

What car are you referring to? I'd like to check it out if you've got anything on written about it on here.

slmhofy

iTrader: (5)

I've had the BC springs on my head for just about a year and a half. They've ran great so far. 270WHP street car forged pistons/rods and buzzing it to 7500.

I haven't spoke to Bogus for a long time though, so I don't know the status on the springs. And I don't know the part number.

kmvguy

What is the difference between zvs855 and vs855?
Where would I be able buy these springs?

karlou426hemi

sorry. nothing here about the car. it was in a protege 97

i scrapped the car this summer
was tired of broking the transmission

car was trapping around 135-140 mph

slmhofy

iTrader: (5)

Holy crap!

Not sure of the difference if there is one. And not sure where to buy. I think I got mine from Summit a few months ago.