on what rpm does the exhaust valve opens on 2013 800 cfi pro rmk?
rpm exaust valve opening?
- Thread starter thewayout84
- Start date
G
geo
Well-known member
From what I understand the rpm point is variable, to a point, depending on atm pressure or elevation (same thing to the computer).
May be wrong but my sled seems to open at home (1300 feet) about 7478 ish lol when warm and feels like it is closer to 7777 ish lol at 6000 feet.
I felt this was a bit too late and a reason for some of the quick heat build up in the motor and maybe a bit of a power robber (but easy to tune at the factory for the EPA and warranty dept.). So I installed some softer springs (thanx TRS) and it seemed to help for both things and made my midshift loading work better.
One thing to check. At about 800 or 900 miles I felt the engine was losing some snap (oh oh! lol). After checking things over at home I found the 90 degree nipple in the engine side of the solenoid had lost it's seal. It can't rotate loose because of the hose attached but the thread sealant was gone and the basically I had open vents from the valves (not good on my 13 and it's fuel and timing map).
I carefully cut the hose off (mine was stuck good lol) and re sealed with High temp Loctite instead of plumbing dope and all was good again.
May be wrong but my sled seems to open at home (1300 feet) about 7478 ish lol when warm and feels like it is closer to 7777 ish lol at 6000 feet.
I felt this was a bit too late and a reason for some of the quick heat build up in the motor and maybe a bit of a power robber (but easy to tune at the factory for the EPA and warranty dept.). So I installed some softer springs (thanx TRS) and it seemed to help for both things and made my midshift loading work better.
One thing to check. At about 800 or 900 miles I felt the engine was losing some snap (oh oh! lol). After checking things over at home I found the 90 degree nipple in the engine side of the solenoid had lost it's seal. It can't rotate loose because of the hose attached but the thread sealant was gone and the basically I had open vents from the valves (not good on my 13 and it's fuel and timing map).
I carefully cut the hose off (mine was stuck good lol) and re sealed with High temp Loctite instead of plumbing dope and all was good again.
It actually doesn't lower the opening RPM, it allows the ex. valve to open when the ECU activates the ex. valve solenoid.
The stock spring hinders opening at altitude. With the loss of compression at altitude the stock spring pushes the opening to a higher RPM (7800-7900)even though the solenoid is activated. With the stock spring you will also witness ex. valve flutter as the ex. valve opens, culprit here is the loss of compression once the ex. valve opens. State of tune of your engine has an effect here also. Many times clutching is blamed for poor runability but in actuality it is the ex. valve. On the hill in a hard pull, when the RPM drops below 7800 RPM the valve will fall out and will not recover until you chop the throttle and get back into it.
With the Dragons we ran a blue or a blue/white spring to elevate this issue. The PRO doesn't like that choice of spring. The green/ white does the trick.
We change clutch weights and lean our fueling for elevation. What about ex. valve springs??? Just another tuning tool in the box.
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It is amazing how many dealers don't even care/know about different exhaust valve springs. They just think everything is perfect from the factory for every elevation and person.
In fact, its amazing how terrible dealers are in all aspects, plain and simple. At least around here.
In fact, its amazing how terrible dealers are in all aspects, plain and simple. At least around here.
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as others have stated, the rpm they open at is based off pressure. It will depend on what springs you currently have in there.
My dealer was very helpful/knowledgeable about this (as was I prior to) in choosing some different springs for my elevation and set up
what are you trying to accomplish?
My dealer was very helpful/knowledgeable about this (as was I prior to) in choosing some different springs for my elevation and set up
what are you trying to accomplish?
Haven't had the opportunity to ride them below 6000'. But above that they are a definite improvement.
Orange, stock spring in all CFI2's from short tracks to long tracks.
4Z, Thanks for the PM, I have the same problem with my sausage fingers.
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great info thanks
let it snow
let it snow
G
geo
Well-known member
Rpm is dictated by the solenoid. As TRS said above if they stay open or flutter is dictated by combustion pressure against the spring.
Lower elevation means higher combustion pressure and the orange are fine. Higher elevation less pressure and the ex valves become more stable with less spring pressure.
If you like to over rev (8300 to 8400) you probably would not notice a spring change. If you clutch for more torque to HP balance (7950 to 8050) you would notice the spring change.
Lower elevation means higher combustion pressure and the orange are fine. Higher elevation less pressure and the ex valves become more stable with less spring pressure.
If you like to over rev (8300 to 8400) you probably would not notice a spring change. If you clutch for more torque to HP balance (7950 to 8050) you would notice the spring change.
I'm riding 6700-10k, stock motor running 8250 rpms.
So if I understand, the rpm at which they open is not impacted because that is controlled by the solenoid, but the lighter "weight" spring helps with more consistent operation at elevation due to lower cylinder pressures. Right?
So if I understand, the rpm at which they open is not impacted because that is controlled by the solenoid, but the lighter "weight" spring helps with more consistent operation at elevation due to lower cylinder pressures. Right?
Correct
Freak495 Good info. I ride 6k plus all the time, i clutch for 8150-8250 and have 7-8# of boost would i benifit from switching springs? or is it different for boosted sleds?
On my boosted sled I run the stock spring
exhaust springs
what are your thoughts on changing them on a stocker with 170 pisg ( has head and fix kit so not really stock) cranking comp at 3400 ft? I ride mostly 5000-8000
thanks
what are your thoughts on changing them on a stocker with 170 pisg ( has head and fix kit so not really stock) cranking comp at 3400 ft? I ride mostly 5000-8000
thanks
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