Could some tuner enlight me about an issue in 996 turbo's dyno charts? There seems to be a small (or rather large ) dip around 5-6k rpm in both tq and hp curves in (virtually all) dyno charts and I'd like to know what's the reason for this.

 

I'm no expert but it could be a minor clutch slip.

 

I'm thinking it's the Variable Valve Timing, my S4's the same way.

 

Thats what I was thinking as I read that. +1

 

HI,,I believe it varies with different turbo set-ups..Not all have that dip..

 

OK, let's take out some variables from the equation and only discuss OEM turbos. See pics (Which are only examples found from the net, not particulary directed to this tuner.) :

 

So nice to notice again the lack of aswers from those who know -or pretend to know- when there's no place for shameless plug of their own products....

 

Maybe then you should use the SEARCH function then and come up with your own conclusion...

 

I can exclude Variocam issues as a reason for sure!
I nerver noticed such a dip in that rpm region before and it may be related only to k16 turbines?
I do notice a certain dip at K24 turbines between 6k and 7k.

 

Thanks for your comments, mine embedded:

I agree on this.

Above charts are 996 turbo (K16) and 997.1 turbo (2277VGT), so it's not just turbos but something with the engine, maybe tq modelling and/or inginition timing (knock retard?).

That's in higher rpm region than the one I'm interested and may be related to intake/exhaust.

 

Pete, I've heard that its an intake manifold thing but I've seen too many (mine included) without the dip to believe it. I think its a chassis dyno thing.

 

why don't you ask the hard question the tuner who flashed the car. That would make more sense right?
could be the exhaust, tune, both, something inherent in your car, etc etc...

 

...So right..

 

Some big variances in the dyno sheets you posted for sure, hard to find much hard info on variocam function in this engine but I don't think that is why those dyno sheets have the big valley in the powerband. The big spike of initial torque shown on those dyno sheets could be from an initial boost spike where it drops back to safe levels due to fueling or boost limits on the turbos, or maybe the n75 is faulty or there's a boost leak, it's could be any number of reasons. It would be nice to see a full set of logs for those pulls showing boost profile, timing, engine torque, fueling, wastegate control levels etc.

 

And here it is again (and plenty of more similar dyno charts around), it's quite hard to imagine that all these cars have some issues. So what's the clue?



This not so bad one, but the TQ curve acts again around 4-5k.