Carl Fausett

Thats a fairly flat A/F graph - I know that difficult to do on a 968 so "Good Job".
13:1 is a bit dangerous, though. Max HP is attained at 12.5:1 and depending on combustion chamber shape, fuel, and other factors we recommend 12:1 for low boost and 11.5:1 for high boost applications.

Lemming

That was done using just an adjustable fuel pressure regulator. And I agree, I don't want to run the FI car at 13 like I did with my NA.

Lemming

Got my ostrich and loaded up tunerpro. Joshua from roguetuning.com sent me a base map and the car started right up. Will need some tweeking but that's ok, looking forward to learning this stuff!

Rogue_Ant

Glad to be able to help

Lemming

Determined which of the many fuel and timing maps were functional under idle and part throttle situations. Could not do WOT mapping. Will either hit the dyno or put the DME in my street 968 to test those. Progress is being made.

Jfrahm

I tested my custom grooved pulley on Sunday. This was a setup with a Volvo dual sided belt and another idler mounted more or less int he middle of the belt 'triangle.' The pulley I made was about 2.25" in diameter and cut to more or less match the grooved belt.

To my surprise I could not get more than 4 or maybe 4.5psi before I saw belt slip, or at least the boost pressure flattening out. This is the same pressure I was getting out of the smaller pulley I was testing before. I was seeing 6psi nudging 7 at redline before, with the stage 2 smooth-side pulley that came on the car.

Next I indent to try the knurled pulley, which showed up while I was working on the double sided belt project. I might try the Stage II pulley again as well to re-establish a baseline.

From there I could go back to a deeper-grooved pulley or try something like a steel pulley that has been shotpeened.

If for some reason I am hitting a wall at 4.5psi I might just decide to use a boost limiting valve set for 4psi or so and run the smaller pulley that gave me nice midrange and not worry about it. I liked the fat midrange from the 2" pulley better than the 6 psi at the top top end I got with the 2.25 pulley.

Any thoughts on belt tension?

-Joel.

Lemming

Joel, I did not have any issue with belt slippage with the new 2.3" knurled pulley when on the dyno (5lbs max boost). I'm off to the track on Wed., will let you know how it holds up.

I agree with getting more boost down low and then bleeding it off. I'm waiting on the larger crank pulley before going this route. One thing that Carl has pointed out to me is that as we drive the SC faster (even with bleeding), we will need to rebuild more often. Also, watch that you are not spinning beyond the max rpm limit of the SC. I've seen two different upper speed maximums (45K and 57K, IIRC). Not sure which one it is, hopefully Carl will chime in.


I also have one of Carl's larger 2.9" pulley that I am going to try to fit on the alternator so that I am not overdriving it.

Lemming

Excellent test and tune at Little Talladega today http://www.tgprace.com/

After running today, I am convinced that I have not been on track before without the belt slipping. Today the car pulled well up to redline (6400) for two solid hours without adjusting the belt. So, even though the car has less power with the larger pulley, it was much more fun to drive.

I am also happy to report that my new ducting has apparently taken care of my overheating issues. No issues at all today, car did not even think of getting hot and I never had to run the fan while on track.

If you look at the track, you will see that the longest straight is less than 1000 ft (from track out to braking point). My top speed today was 110, when I was there last month without the SC, my top speed was 102; got to love that!

Carl Fausett

Excellent! I am getting very good reports from the field on the new supercharger pulley as well. Glad it added reliability for you. Because it cured the belt slip, you probably have more boost up top than before, just less boost down in the mid-range where the smaller pulley could hook up.

Jfrahm

Great news!

So what'd you reckon about belt tension? It would be somewhat subjective without a kricket or something but it should be possible to get a deflection measurement across the top run.

Cheers,
-Joel.

Lemming

I have a cricket, will check tonight!

Lemming

90 lbs according to the cricket, as tested on the belt going from the crank pulley to the underside of the sc pulley. Based on feel, the belt has stretched a bit since it was last tightened.

Added: I just tightened the belt to where I believe it was when installed. Cricket now at 145 lbs.

mattipuh

Rogue Ant, what kind of stock map for 968 do you have? Easy to start working and fine tune? I might be intrested for next year if I plan to do some engine mods..

Rogue_Ant

mattipuh,
As soon as we finish identifying which maps are used, then I will release a DIY Tuning, just as I have done for the 944 series.
Definitely easy to start working with a tuning, you can check out the 944 DIY thread here:

944 Turbo DIY Tuning

Lemming

I should have time this weekend to determine the WOT maps using my daily driver. Got busy this week with work and a track day!