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Discussion Starter · #1 ·
Hopefully upgrading turbo soon and some drop in cams so don't necessarily need valve springs but at what point could i get valve float?
 

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Uprated valves springs might save the engine sometime if you run higher power and bounce your car off the limiter.i took out 3 valves in my engine due to standard springs and 600bhp.
 

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Discussion Starter · #5 ·
Suppose it is hardly much more if having cams done and gives option of higher lift cams
 

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Use a spring tester on your stock valves when you put it together.
Boost and valve springs don't have any correlation.
It's RPMs that matter.
 

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If staying below 11mm of lift and below 8,200 rpm, and the stock springs are in good condition then you will be fine using them.




Marios
 

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I think this maybe true on later evo' s but evo 4-6 runs weaker springs I'm led to believe.? Don't the 8-9 evo have stronger springs and light valve gear?

If staying below 11mm of lift and below 8,200 rpm, and the stock springs are in good condition then you will be fine using them.

Marios
 

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Boost and valve springs don't have any correlation.
It's RPMs that matter.
So a stock car running 7psi at 7500rpm vs a remapped and forged car running 34psi at 7500rpm both on stock valve springs, the spring pressure doesn't matter? The fact you have increased air pressure behind the intake valve when it is shut by 27psi at the same rpm point makes no difference to valve control? :lol::lol::lol::shake::shake:

I think this maybe true on later evo' s but evo 4-6 runs weaker springs I'm led to believe.? Don't the 8-9 evo have stronger springs and light valve gear?
Earlier to later springs are different correct. Cannot remember which way around it is but one is a straight spring and the other a beehive. They have different seat pressures and rates too.
 

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acting daft since 1969
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but 27 psi is nothing in comparision to pressure of a valve spring

an increase up to 34psi /2.4 bar will see you have to upgrade almost EVERY part of an engines internals ,but a standrd evo running 1.2 bar/17 psi ,will cope with an increase up to 1.8 /26 psi quite easy ,we run standard stuff with 1.8 bar and REAL anti lag with no issue
 

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If you know what the seat load is along with the valve diameter, you can work it out.

Maths and physics
vs
uneducated opinions.
 

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Discussion Starter · #12 ·
Really finding alot of mixed views on this, people saying that boost can and will cause valves to creep slightly open. Interested on some hard data
 

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Transmission Dynamics
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Really finding alot of mixed views on this, people saying that boost can and will cause valves to creep slightly open. Interested on some hard data
Are these brand new standard valve springs or high mileage fatigued ones?

What are the seat and nose pressures of the springs you have?

What cam, lift and ramp angles?

What turbo, boost and max rpm?

You want definitive answers, but don't provide definitive information. :shake:

If you want hard data, why don't you do some testing yourself and find out?
 

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Here's a clue.

When the intake valve opens.......what's the pressure across it?
Answer.......Boost on one side, a bit of cylinder pressure on the other side (it's emptying the exhaust).
If boost blew it open a bit quicker......that would be good?

When the intake valve closes........how much pressure is across it?
Answer.........boost pressure on one side, whatever pressure is in the now nearly full cylinder on the other side.
If boost made it stay open a bit longer then you might get more air into the cylinder?.....that would be good?
Afterall, that's why we fit longer duration cams.

How much pressure is across the valve when it's open?
Answer........very little if it's doing it's job properly.

What a dumb question?
Really?


Never take notice of anything that parts sellers have to say.
 

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Discussion Starter · #15 · (Edited)
Are these brand new standard valve springs or high mileage fatigued ones?

What are the seat and nose pressures of the springs you have?

What cam, lift and ramp angles?

What turbo, boost and max rpm?

You want definitive answers, but don't provide definitive information. :shake:

If you want hard data, why don't you do some testing yourself and find out?
All the threads i was reading were actually evom in usa not sure mileage on their cars but mine is around 70k, im not sure what value the standard seat pressures are, what are they?

Cams wise looking at kelford 264 or tomei 260 procam, turbo 80 series or 71hta not 100 percent but 1.6-1.8 bar stock rpm limit 7.5k.

Didnt realise all these parameters made a difference only was looking at boost and rpm, not something i have ever tested before or have equipment to do im just a self taught diy mechanic (only work on my own cars) so try to learn as i go along.

I see plenty running 1.8 bar on 80 series with drop in cams on stock springs but would be interesting to see if there is even a tiny bit float.

Fwiw at same time i have cams done i would more than likely do springs anyway as i would hate to have issues and need it all opening up again and new springs is always going to be better anyway.
 

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but 27 psi is nothing in comparision to pressure of a valve spring
Depending on your valve height and condition of springs, the stock pressure on the two different type of evo springs range from 50-75lb of seat pressure from what I have measured. This is the pressure the spring exerts on the valve with the valve shut.

When the intake valve opens.......what's the pressure across it?
Answer.......Boost on one side, a bit of cylinder pressure on the other side (it's emptying the exhaust).
If boost blew it open a bit quicker......that would be good?
When the intake valve opens the port pressure will be perhaps 5-10psi less than the boost pressure. By the time the exhaust valve closes the intake valve will still be at partial lift and intake port pressure is climbing rapidly to perhaps around 20psi more than the boost pressure. This will drop under boost pressure by peak lift. Come around to intake valve closing and your port pressure will once again be slightly over your boost pressure but your spring pressure is rapidly dropping with the closing valve. Intake port pressure will more than likely spike over boost pressure before exhaust valve opening and also during the exhaust lift cycle, it does not sit at a constant pressure with the intake valve shut.

The same holds true for the exhaust valve. This is not just an intake issue. The exhaust back pressure may spike to 20psi or more over boost pressure just before the exhaust valve shuts. So in your crucial overlap period where the exhaust valve is trying to shut but back pressure is fighting the weak spring you may have a loss of valve control. Then your intake valve may suffer the same fate on its closing ramp. Loss of contact with the ramp may cause the valve to smash into its seat. This wears the face and more often then not snaps the cheap two piece valves that production engines often run. The valve may also bounce which again is loss of pressures and premature wear or breakage.

If you know what the seat load is along with the valve diameter, you can work it out.

Maths and physics
vs
uneducated opinions.
It is not that simple. The cam profile has a major effect on valve control. The numbers you see printed on the cards or even worse the advertised numbers do not tell the story of what is going on. How often does a "272 cam" actually have an actual area of 225? Pick any of the 272 cams available and they could be very different in profile and actual areas.

Are these brand new standard valve springs or high mileage fatigued ones?

What are the seat and nose pressures of the springs you have?

What cam, lift and ramp angles?

What turbo, boost and max rpm?
Exactly that. There is no two golden rule strategy here. Are the cam profiles asymmetrical or symmetrical? The former may have super fast exhaust closing and super fast intake opening to minimise overlap but keep good area. This though requires even greater spring control than a symmetrical cam with the same area.
How close to coil bound are the springs at peak lift and is that creating a problem at certain frequencies?
The manifold pressure and exhaust manifold pressure values we log and view on dials in the car are hugely damped and do not represent actual millisecond readings. It would be very unwise for anyone to assume that having 15lb more boost pressure was 15lb more behind either valve head constantly. To see the true picture requires real time pressure analysis which you are unlikely ever see on here.

Didnt realise all these parameters made a difference only was looking at boost and rpm, not something i have ever tested before or have equipment to do im just a self taught diy mechanic (only work on my own cars) so try to learn as i go along.

I see plenty running 1.8 bar on 80 series with drop in cams on stock springs but would be interesting to see if there is even a tiny bit float.

Fwiw at same time i have cams done i would more than likely do springs anyway as i would hate to have issues and need it all opening up again and new springs is always going to be better anyway.
Sounds like you want to take the sensible option and just run uprated springs. Just be careful you do not go crazy on spring pressures with old two piece valves or you may suffer an early fatigue failure. Also no point having overkill spring pressure as you waste power opening them.
 

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Discussion Starter · #17 ·
If im having valve springs done and retainers it will be from norris as hes done the rest of the work, on his recommendation ive been looking at tomei procam 260 and he did say it doesnt need springs but for the small cost of having it done its worth it as you dont want to suffer from valve float. If im doing cams springs will be done but if i dont do cams yet but upgrade turbo to either 80 seeies or 71hta it will run at 1.8 and 1.6 bar respectively so thats why i was asking relationship of boost and valve springs before i knew there was other parameters involved
 

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Transmission Dynamics
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Didnt realise all these parameters made a difference only was looking at boost and rpm, not something i have ever tested before or have equipment to do im just a self taught diy mechanic (only work on my own cars) so try to learn as i go along.
All those parameters and more, make a difference.

Even with everything calculated, valve train resonance at certain rpm's can seriously affect how the spring performs. Thus why Mitsubishi changed to a beehive valve spring on later engines.
 

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Transmission Dynamics
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When the intake valve opens.......If boost blew it open a bit quicker......that would be good?

When the intake valve closes.........If boost made it stay open a bit longer then you might get more air into the cylinder?.....that would be good?
Afterall, that's why we fit longer duration cams.
Are you actually saying that increasing boost will make valve duration longer, and that is a good thing? :crackup::crackup::crackup:

Seriously mate, what planet are you on? :shake:
 

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Discussion Starter · #20 ·
Thing is if im upgrading springs im probably tempted to run gsc s2 and with possibly a higher rev range if theres any power being made up top, i normally change gear around 7k and rarely take it close to rev limit 7.5k, so may not be too bothered with power right up to top but gsc s2 seem to make power all the way which is good
 
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