Speedtoys

Instant adaptation is fast. That feeds the slower long term. Should be fine.

victor25

OK... as promised, I finally got to a different dyno with the 80mm pulley installed and everything stock on the car except RMB. I loaded the base maps and did some pulls.
After the first pull, I reset the O2 adaptation which flattened out the fuel ratio some on a second pull. Which is what you see. HP was 382, TQ was 365, and boost was 5.3. The only thing that looks odd is the rpms. He said I was shutting off at 5800, but my tach said 6200.

Then we did some tuning runs and I adjusted the WOT map and made the fuel ratio line nice flat and pretty, but I forgot to have him print the last one. I will try to get him so send it too me, but the hp and torque numbers really didn't change much, I believe it was 386hp and 370tq.

Sorry abut the picture quality from my cell. I will edit it later with a better pic.

AO

Ok... So, you gained roughly 100hp at the wheels with 5.3psi. That's 18.8 HP/psi which is pretty much what people have been saying you should expect. I use 18/psi for me.

The RPM is either off on the dyno (not too likely) or your tach is off (likely). Did you log it with the STer? What did it say? If you do have another 500-600 rpm, there might be another pound of boost there allowing you to hit 400whp.

victor25

I asked the guy running the dyno about that, and he said that he was taking his readings directly off the plug wire. So he was pretty sure he was correct. My tach may be a little off, but sharktuner data log said I was above 5800. But whatever that's not a biggie. The point was to get readings on a stock 928 s4 with a stage 1 Rotrex supercharger kit from another dyno.

Ya know I was never arguing with anyone about what the power expectations would be. And I believe that it pretty much landed about where everyone expected, including me. The claim was that the Rotrex in a stage 1 kit on the Porsche 928 s4 would reach or surpass 450hp at the crank with 6psi of boost. Of course we have no way of reading this power while the engine is in the car, so we get it from the wheels. Hopefully we can all agree that 450chp x .85 is 382whp. That's a 15% loss. That being said, and the fact that the car dyno'd 382 with under 6psi, well I hope everyone is happy now, and that the data has been provided enough info for me to stand by the claims.
We did come up a little short on the boost expectations with only 5.3 and 5.4. I'm sure it makes a difference where you take your boost readings from. The dyno guy was getting his vacuum/boost readings from the brake line connected to the intake manifold, which I believe is the correct location. If I was to take the readings closer the Rotrex, it may have been 6. I really don't want to put a 75mm pulley in the stage 1 kits, because then boost would climb above the 6's.

I'm actually quite surprised that there weren't more posts last night. Guess everyone's satisfied with what they saw / read.

Lizard928

Excellent news Victor, and bang on results.

Jon B.

That's a stout gain any way you look at it. Thanks for sharing your results Victor.

SeanR

I'm happy with what you posted and the results. Tells me a whole lot more about what these cars can do with some exhaust work (X-pipe/headers ect) and intake work. Add in some extra tuning on top of this and we are going to be able to put out some really good numbers.

rgs944

I think the performance gained in the stage 1 kit is a great improvement in any street car. I was going for reliable and usable modern street power when I went with this kit. It has delivered eveything I expected. The wide open stuff is nice but I enjoy the car at 1/4 and 1/2 throttle as much as anything. Afterall, that is what you are using 98% of the time anyway.

S4ordie

Nice results.

a little Supercharger music

rgs944

Victor, Do you think I would gain anything significant on the low end by gong to the smaller pulley?

SeanR

Took mine out for a bit of a run this morning in the really cool air we had (40) and damn this thing pulls. The tire started to spin an *** load when it shifted to 2nd gear. I say tire because I lack the LSD in mine. I guess my tuning the day before made a bit of a difference also.

victor25

Oh for sure!! But you would either need to intercool the boost, or we would have to restrict your intake air flow to keep the boost down on the higher rpm's.

I know for a fact that with the 70mm the boost is great down low. The pulley is not hard to change, but your belt may not be long enough for the 70 and you would prob have to get one an inch shorter, but it's all easy.

Is your air pump still on your car Rob? If I remember correctly you are not using it, but I don't remember if it was there. If it is you could install the water/air intercooler and just use the air pump output to chill it.

SeanR

Victor, what's the current length on the belt that came with the kit. I want to drop down 1/2 to 1 inch in length so I get a bit more tension on the belt.

victor25

It should be a 62.5. If you are running a 75mm, then yeah I'd go with a 62
part # 5060620

SeanR

Thank you, I'm at full tension and it's still a tad bit loose. I can feel it a small bit of slipping at 5800rpm.