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Stock cam may be OK...

Stock spring is not. Think about it. 800hp means 30 to 35psi of boost. All this boost is trying to push the intake valve open against the stock spring.
The valve is bigger (more area for boost to press on) than the spring. This is like taking 50lbs out of spring pressure. Would You run 20 psi seat spring on Your motor? It will float at when the boost kicks in. Valve will contact piston... boom!!!

Not to mention thermal problems.

It just was not designed for boost....

Anton


Anyone running stock valvesprimgs and cams to 800+?
 

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OK so 30 psi pushing on the back of the valve with a 3/4" surface area we will say. Now did u think of cylinder pressure pushing on the face of the valve? Compression test 210ish psi. Now add boost. And face of the valve has a larger surface area than the back.
 

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35mm diameter for round numbers... is 53 pounds of extra force on the valve at 35psi.

It is the top of exhaust stroke that you need to worry about. The cylinder is scavenged and close to the valves.

Extra turbo heat will heat the spring and they will loose tension, also. Hence, expensive springs.

The 4Piston PSI springs are worth every penny at $900 per set. All Indy teams and NASCAR teams run them. In NASCAR with big valves and running between 7800 and 9200RPM, the teams would block oil drain back from the heads, so the springs run completely submerged in oil for cooling. :)

Anton


OK so 30 psi pushing on the back of the valve with a 3/4" surface area we will say. Now did u think of cylinder pressure pushing on the face of the valve? Compression test 210ish psi. Now add boost. And face of the valve has a larger surface area than the back.
 

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35mm diameter for round numbers... is 53 pounds of extra force on the valve at 35psi.

It is the top of exhaust stroke that you need to worry about. The cylinder is scavenged and close to the valves.

Extra turbo heat will heat the spring and they will loose tension, also. Hence, expensive springs.

The 4Piston PSI springs are worth every penny at $900 per set. All Indy teams and NASCAR teams run them. In NASCAR with big valves and running between 7800 and 9200RPM, the teams would block oil drain back from the heads, so the springs run completely submerged in oil for cooling. :)

Anton
I agree with exhaust valve spring being the problem. But purely because the exhaust manifold pressure can be up to 2x the boost pressure.
 

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Usually intake is the problem, if the spring pressure is too low or the RPM is too high. Boost will make the valves float early in any motor. The question is how early...and which valve will go first.... Exhaust valves are smaller... they tend to close as the piston moves up, by which time the scavenge effect would have dropped the exhaust pressure....

It is a common mis-conception that exhaust manifold pressure can be 2x intake. At 35psi with proper turbine selection, there should be a very nice positive pressure gradient over the engine... then there are exhaust and intake pulses i.e. dynamic effects.

Go to Borg-Warner turbo calculator. You can plug in all kinds of number s and match compressors and turbines. it will show the difference between intake and exhaust.

It is true that at low boost levels exhaust pressure will be higher than intake. This is true for N/A motor, then you add a turbine (restriction) and more air to it and it will have higher exhaust pressure.

You don not have to believe me. Use the BW calculator. Read all the turbo books. There are both calculated results and real motor studies in them. Everyone uses heavier spring for supercharging (turbo and super).

Anton


I agree with exhaust valve spring being the problem. But purely because the exhaust manifold pressure can be up to 2x the boost pressure.
 

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K20A2/Z1 stock block
Stock port head/cams with supertech springs/retainers
GT3071R T3 .82ar
Prayoonto centerfeed/Ktuned 90mm
Speedfactory/all-in dual backdoor intercooler/tucked rad/ac condenser combo.
Lean sheepy manifold, T3, 60mm gate.
EP3/DC5 5spd with LSD.

Just a fun street car. If money allows, 4piston 156 head and prayoonto stage 2/cartel 2.2
 

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93 eg
K20a stock block with bc stage 2 cams
Full bc valve train
Excessive intake with 90mm skunk2 tb
2000cc injectors running ethanol e98
Rotrex 38-71 supercharger
461whp @ 14 psi
 

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Hey Guys sorry to bring this back im planning on boosting my stock k20r motor off an 04 dc5r. heres my kit

Blackworks sidewinder manifold t4
Borg Warner sxe369
44mm Tial MVR wastegate
Tial BOV
CX racing intercooler
Comp Clutch Stage 2
Buddy Club spec 2 (basically a fancy straight pipe lmao)
ID 1050x 1000cc injectors
Hybrid racing fuel rail w/ return
AEM 320lph pump e85/meth compatible with custom lines

My goal is around 400whp reliable daily. Do i need to run e85/water meth cuz of the higher compression?

I am also running the stock type r manifold
 

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Hey, i've got a simple set-up
Stock:-K20z3 w/ A2 oil pump

-PTE 6262
-Dual Precision 46mm
-Sidewinder manifold
-CC stage 4 six puck
-Bosch 2200cc
-Walbro 450
-Tial BOV
-Mac 4port(boost by gear)
-Omni 4bar
-full 3' piping
531whp/[email protected]
 

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Motor: K20a2
Power: 400whp @12psi on pump gas
Turbo: GT3582r
Manifold: FullRace
Waste-gate Size: 60mm
BOV: Tial Q
Injector Manufacturer and Size: RC 750
Piping(including dowpipe and exhaust):3” down pipe to Apexi N1
Car would of made more, but maxed out fuel injectors dude to return less fuel system. Did make 424whp but duty cycle was near 100%
 
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