Chunkerz

Will installing the 4 degree offset key affect the accuracy of the TDC mark on my camshaft sprocket? Since the cam gear is moved slightly to the right, it seems to me that the mark on the cam gear may not line up with the mark on the sprocket housing when the crank is set at TDC. Am I completely wrong?

Reimu

Yes, thats the idea of how it works. Its a function, not a defect.

You align it to the marks as you always have but the actual camshaft is degreed a few teeth forward or back depending on what you're after.

V2Rocket

should move it off the TDC mark about half a tooth. one tooth ~9*, so a 4* offset is half that.

Crackership

+1

Chunkerz

Makes sense. Thanks!

Rogue_Ant

NO.

Gents, you are changing the camshaft phase not the cam gear.
Install the offset key, put back the timing belt and time the motor as normal. I.E. the crank & cam timing marks line-up.

Rogue_Ant

One more clarification, to advance the cam, you want the end-result to be that the camshaft is rotated clockwise compared to the cam gear.

m73m95

I'm going to install my cam key at some point this week. I'll take pics to illustrate.

Rogue_Ant

Awesome! That will definitely help eliminate any confusion...

blown 944

A simple way to look at it is to visualize everything static in its place and lined up. Then imagine that you can take your fingers and turn the cam (the center, not the gear) clockwise slightly.

m73m95

Here we go...

1st, I have to apologize. I didn't get all of the pics I wanted. All I have for a camera is my phone, and all but 3 pics were so out of focus, they were impossible to see. I'll try to make do with what I have though.

OK, here is the stock gear and key.



Here, same pic, but I have drawn the red lines to illustrate the stock location of the cam and gear alignment, and the gear alignment with the cam housing. The red line will always represent the stock location of the cam/gear/housing alignment.



Here is the offset key installed. As you can see, the portion of the key that goes inside the groove of the cam is "further ahead" of the portion of the key that is outside the cam groove.



As shown here, the red line still represents the "stock" locations. So the outer part of the key (in the gear) is lined up with the stock location with the alignment mark on the housing. The only thing that has moved is the camshaft. It is now further ahead in the rotation... thus advancing the cam 4°.



Here is a fantastic drawing of the end result. Hopefully it make sense. The gear will always align with the housing. So when you do timing belts, nothing changes with the procedure. The only thing that has moved is the cam.

SpeedyC2

This is very clear to me - thank you!

Chunkerz

Wow those pictures helped a lot! Thank you! I can't wait to do my timing belt so I can install my key

m73m95

So, now that I've had a few days driving with the cam advanced, I'll do a bit of a review.

For the cost of the key and time involved in installation, I really feel like this one of those "Must do" mods, like the throttle cam and a performance chip. The installation took about an hour, and was straight forward using the guide for cam seal replacement on Clarks Garage (Same steps to get to the seal, as to get to the key). If you've got a timing belt due, there is no reason not to pull the gear off and install the 4° key. The only issues I had with installation, as the key needed to be filed down a bit to fit in the cam groove. The key is also a little bit short. There is a slot on the retainer "nut" that must also line up with the cam key, but its difficult to get matched up exactly because there is very little key that shows past the cam gear (difficult to explain, but my pics above show it). These are minor issues and just add a little bit to the install time. Not a big deal.

When driving, torque comes on much sooner. Right off idle, its noticeable. Driving around town is just "easier". Less throttle pulling away from lights, and faster acceleration. On the highway, performance is equally as good. I have higher vacuum when cruising at 65 than I did when cruising before the key change, which means I have to use less throttle to keep the same speed (Which I assume will mean better fuel mileage). Vacuum is affected by a lot of different factors, but on my usual "test" roads, I could tell I was using less throttle to keep the same speed. At full throttle, acceleration is..well...there! Right from idle. It was rainy here today, in Vegas, and it was very easy to drift around corners On the highway, passing is much easier. Still have to drop down to 4th, but I could mash the gas and get around a slower cars easier and could pull out with oncoming traffic closer than the horizon....

One thing I noticed is the power also "seems" to drop off much sooner than without the key...around 5500-5800rpm. Which is the 'downside" to advancing the cam. Basically, the cam key just moves the power band to lower rpm. So you gain down low, but lose the high end sooner..... However, this is where the butt dyno lies. The power gained with the cam key is enough that, even though the power feels like it drops off early, the engine is still making more power than before adding the key. Meaning, you're still accelerating faster than you would at the same rpm without the cam key. So in reality, even though it "feels" like the power is dropping off...its actually not Win win!

Here is proof of that! Josh @ Roguetuning ran his car through the dyno with his NA Tune, with and without the cam key. As you can see the HP and torque lines don't cross until ~6,000 rpm. So the car is still making more power than without the cam key, up until a few hundred rpm from red line.



Like I said, so far I am very happy with the key. Its one of those things where you wonder why Porsche didn't do it from the factory.

I'll update the post to talk about my increase (or decrease) is fuel mileage, as soon as I burn off this tank (And maybe the next one, since its difficult to keep my foot out of it right now lol).

fred27

Thanks for clear pictures, explantion and sharing your impressions. It woulsd be interesting to see what advancing the cam would do to lap times on the track.