refresh951

Each tooth = 8 degrees

refresh951

Duke,

Thanks so much for posting this. Amazing that 1 degree would cause such a change. The curve shapes are very interesting. This is why I put in an adjustable cam gear. My last dyno looks a lot like the red curve. I am actually going to pull 1-2 degrees on the 3L stroker motor and try to flatten things out a little on top.

Rogue_Ant

Yep. So, a lot of the cam-timing changes I tested on my 944NA. This removes any variables that a turbo usually carries (such as boost pressure, IC heatsoak, ect).

Here is advanced cam, vs retarded, vs stock degree - back to back testing:

refresh951

Joshua,

Great info. Thanks so much for sharing. What was the amount of advance/retard? Four degrees?

Rogue_Ant

Yeah, the retard was 4°, the advance was 4-5°.

Reimu

I like how this dyno almost perfectly represents the expected results when playing with cam timing. I wish we could see how it treats the onset of boost.

Rogue_Ant

After testing timing changes on the NA, I went and advanced the cam on my 951 by 3-4°. I'm sure I could quantify the difference with a datalog, but immediately noticeable change was improved low-end (as expected), and boost does come on sooner.

eman930

I agree, I advanced my 86 944 turbo camshaft 4 degrees, and have a 09R camshaft installed (late NA) Low to mid range power is improved, Boost spools quicker, and I noticed no top end power drop, This is all seat of pants dyno testing.

dmcampbell

I have had my 4 degree cam key (from Josh) in for several months and really notice the low end torque, particularly when pulling away from a stop with a/c on. I also did a track day back in May and could definitely feel the added torque/earlier spool on track out. I like it. Mike

Dougs951S

Nevermind

dude54758

So you throw the key in and bump the drive sprocket over to the tdc mark then?

Thom

Of the folks who played with cam timing, did you adjust your ignition timing profile?

Van

Yes.


You did the math yourself - one tooth on the cam gear is 4.5 degrees of crank angle.


This is wrong. Each tooth is 9 degrees of cam angle.

eman930

Ive done nothing to my ignitiong timing other than add a MSD blaster coil

gregeast

I installed an offset cam key from Rogue in my 951 this morning. As predicted, the powerband shifted very nicely down in the rev range and honestly, it still has plenty of poop at 6.5k. Plenty. Noticeably stronger pulling away from a stop light, I'm at positive boost by just over 2k. Much better with the air conditioner running as well.

I don't have a lot of seat time with it yet but definitely a nice improvement for a street car.