...did you put it in the right way around (advance vs retard timing)?

if set to retard it would have no power at all and run poorly.

 

 

 

https://928motorsports.com/parts/off...aft_keyset.php

 

Spencer, As I have stated in both of my previous posts, everything was installed, and checked out correctly. The 4 degree key that I bought had not only installation instructions but also a picture showing the correct installation position that any one over the age of 8 should be able to follow. It just didn't work correctly in my car. I've been an mechanic since 1970 and understand the difference between advancing and retarding the ignition timing.

 

...cam timing

weird it didnt work for you

 

At what....?

Catching dust...?

Probably,

CFM is increased though and ultimately, that's the target, unless of course the installer places a cone type pulling in under hood air, then yeah, it'd be a downgrade...

T

 

Or change it out completely for another grind.

But what do I know.....?



T

 

Thanks for the link! I get it now. Does seem awfully similar to installing the belt one-tooth off.. which I did once on a '90s Golf.. it hesitated a bit.. not sure if the off-tooth retarded or advanced....

 

Perhaps that's why they refused: the experienced mechanic probably has had enough trouble removing the original key not to bother with the headache lol

Say.. if you do get this installed... I'd love to hear your impressions

 

$20 for a key vs $250-$600 (depending who you ask) for a hot cam is an easy choice for a street car, most of the time.
944 stock unopened oil system wont live much past 6000rpm-ish so limited room for high-end power there without tweaking it like you might.
might as well make the most of 1000-5500 range, 4 degrees advance makes a HUGE difference there.

almost...1 tooth is 9 degrees so this is about half a tooth

 

Spencer, I think you have the offset key and VEMS. Did you do the both (maybe NA Tune) at the same time? If not which did you do first and what was the comparable performance increment of each?

 

Here's the best thread on the 4* cam off-set key, imho:
https://rennlist.com/forums/924-931-...t-cam-key.html

 

Disagree on the on the rpm limit of the oil system, but yes, point taken re stock unopened engine vs plotting changes to improve oiling that require internal mods, some of which are of not a great expense.

I'd like to see dyno proof of a "huge" difference though. Not debating a difference in power characteristics, just the quantitative effect, i.e., quantity vs quality.
Being that you are moving both lobe sets in conjunction, about the only thing you could see @4 deg is a dynamic compression increase/decrease of 0.2:1 CR caused by the effective swept area that the piston is actually compressing fuel/air from the time intake valve closes. Because the exhaust cam lobes are part of the singular camshaft, you affect cylinder scavenging also.

Increased compression has an effect on torque, that's what you are feeling.
Plug in +0.2 :1 static compression ratio change in an engine power/torque calculator, with the correct rod length, stroke, etc and I think you will find that increase is negligible.

Is it worth $20....?
I guess.
If you are willing to sacrifice an equal loss of horsepower in the upper rpms.

That said, offset camshaft keys are not legal in PCA sanctioned Spec racing but I'd buy a gross of them and hand them out free to competitors if they promised to increase their low end torque....

And yes, I get it, not everybody interested in the 3500-7000 power band, not interested in racing, low end torque makes street driving "more fun", etc.
I know for me, 5 more ft/lbs of torque at 3000 rpms makes my trips to WalWart all the more enjoyable...., by a factor of 200%.


T

 

Let me get this straight: Porsche decided on cam timing that makes the car feel sluggish on the "round the block" test drive but performs well going around the track in third gear?

Or did they do this on purpose to, as rumour has it, ensure the 944s didn't outshine the 911s?

Given that most purchases were for regular street driving (I'd bet on that), this doesn't sound like a wise decision. Or is the stock cam timing an emissions compromise? There's got to be a good reason a manufacturer purposely times the engine to behave poorly at most driving rpms vs track racing. I don't get it.

Maybe there's a long-term issue we're missing that can result from this mod?

In any case, there's a 2deg and 4deg available. Why both options? Is the 2deg working better on some engines? Or is it less risky for some reason?