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What the **** are they exactly.... i was once told, or thought (becuase it made sense) that the VTC spring was used to control our variable cam timing. as it was spring loaded, it kicked in depending on how hard throttle you gave no matter the RPM. so now i want to clerify once and for all... What is the exact purpose of a VTC spring, and what is/how does the VTC system on our car work. Thoughts?
 

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I don't have an answer for you really... but I changed over to the HKS heavy duty VTC springs when I had the motor apart a month ago. My exhaust note is now louder than it was before.

I don't know what else to attribute this to other than the springs since it technically was the only change I made. The former timing belt was nearly new and the new water pump is just another OEM unit.

Oh... I just remembered something... When I was looking through my collection ofparts out in the garage I found the box that had allthe parts that were removed during my original 120K maint. The OEM VTC springs that I bought for the procedure were still in stapled in the plastic bag they came in. The mechanic never changed my springs. That makes me a little mad. No wonder there was a difference. The springs I was running had almost 94K miles on them.



Post Edited (Jan 25, 4:43pm)
 

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It's oil pressure driven -- more pressure in the system (higher engine RPMs) causes CAM gearing to change the intake valve timing. Pretty sure I saw something that said by 10 degrees or so.

Springs are part of the system -- since the oil pressure into the CAMs sprockets overcomes the spring loading and allows the gears to shift. Saggy old springs means they change timing at the wrong(lower) pressure levels.

Hopefully I'm explaining this correctly? Real experts out there, yes?

PS - Someone over on tt.net posted a pix showing new and old springs side by side. Really could see the difference.



Post Edited (Jan 25, 4:42pm)
 

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Actually Mr. jzach you are ...

indeed on the right track. My understanding of the VTC system is this...The VTC system is controlled by the ECU. When the ECU detects conditions that call for advancing the intake cams it sends a signal to the VTC solenoids which in turn shuts off the flow of oil through the intake cam. When this happens the oil pressure flowing into the VTC unit through the front cam journal rotates a helical gear using a set of "pistons". The rotation advances the intake cam up to 5 degrees. The spring in the assembly assists the intake cams to rotate at the correct degree of advance as well as rotate back to their "normal" non advanced status when the VTC solenoids opens the oil return passages.
MaxDoc
 

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aaahhhhhhh {slaps head} - forgot about the VTC solenoids. Now the whole system sounds more logical and linked together...
 

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I may have well understated ...

the degree of advance. After checking the FSM it does show an 18 degree overlap with the exhaust valve at the full advanced position of the intake cam.
MaxDoc
 

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So then, how do the springs help? As far as I can see they just sit inside the intake cam sprocket underneath the cover. What's their purpose?
 

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Cache - were you reading?

"The spring in the assembly assists the intake cams to rotate at the correct degree of advance as well as rotate back to their "normal" non advanced status when the VTC solenoids opens the oil return passages. MaxDoc"
 
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