ACEparts_com

Here's my Dyno results for a 38K mile 993TT with Techart sports exahust (just boxes).
I would like to know of the 'dip' in boost is due to running in a dyno cell (maybe motronic limiting boost a little too much?).

I'm very pleased with torgue figure of 435lb ft.
FYI, on the same day a 996 tip turbo recorded 324 at wheels also.

Thoughts and comments greatly appreciated.
Alan

TB993tt

ACE
Thanks for sharing - the boost dipping is a feature of the motronic, once it has "tested" where the knock limits are (also influenced by the program parameters) at 4500rpm where it manages 0.84 bar, it backs off the boost before increasing again at peak power, 0.8 bar at 5750. If they had carried on WOT then it should have risen again as it approached the limiter at 6800rpm. 0.8 bar at peak power is higher than stock would typically allow, are you running modified software ?
I would take the actual power figure they come up with with a pinch of salt since there will be inadequate air flow to produce an engine dyno comparable figure.
Look at your power curve, over 375hp from 4500rpm this is why these cars are so damn fast compared to other "400hp" cars

ACEparts_com

TB, I was hoping you would spot this post.
It is my understanding that the ECU is standard (the boost graph looked almost identical to another 993 tested on the day).

The Dyno opperator said they have no way of simulating 100mph of airflow over the IC so to expect this sort of dip. The only down side of having so much power so low down is that you kind of want it to continue upwards at the same rate and never level off!

I would like a little advice on a first step to a little more top end power if anyone has any ideas?

Another point regarding the dyno that I noticed was that engine RPM is calibrated off of the rev counter in the car and measured at the wheels! There is no direct connection between Dyno and RPM!

Geoffrey

The motronic software is limiting boost at the peak torque area (5000rpm) to protect against knock, then increases the boost as it moves past peak torque. If you look at the torque curve it peaks at 4400rpm and starts to move lower as the boost is lowered. If the boost was held constant, peak torque would be somewhere near 5500-5700 which is right where the motronic limitis it. This is done because detonation will most likely occur near peak cylinder pressure/peak torque and the single plug, hemi head with a large bore makes it prone to detonation.

The boost falling off after 6000rpm is because the k16 compressor wheel is at its limit. The dip in boost at 4000 is unusual, I usually see the boost come on to about .9bar then dropping to .6-.7bar in the 5000rpm area and then back up again. It may be a function of the dyno you ran on, it may be a function of the more free exhaust you are running and the 993tt boost control vavle not reacting properly.

TB993tt

With due respect to the fact that Geoffrey has doubtlessly seen more of these cars on dynos than I, I don't agree that the boost falls off over 6000rpm 'cos of the K16 being at its limit - my experience is that a stock configurated car will increase boost towards the limiter at 6300-6700rpm.
Paul Frere states the following in his "bible": "maximum boost pressure is 0.94 bar at 3500rpm. It drops to 0.6bar at 5200rpm and rises again to 0.75bar at the 6500rpm red line."
The boost falling off in the dyno run above looks like the operator cut short the run after 6250rpm ?

ACEparts_com

Actually I think he stopped short of the rev limit to stop it bouncing around on the rollers.
The 996 turbos try and get out when they hit the limiter!

Any ideas for a first mod?

Any idea why the torque is so high @435lb ft?

TB993tt

ACE
If you are close to G Force, I would ask them, they have massive experience in our cars. I would save your money and go for their 500hp/542lb/ft version:
http://www.g-force-motorsport.co.uk/article2page7.html
At £9000 this is fantastic value. I wouldn't want the sintered clutch, I can tell you how to harness the 542lb/ft AND have a daily driver
Re the "high" torque figure, I would say dyno tolerance (when compared to the Porsche engine dyno quoted figure)

Jean

Wow, very interesting analysis guys!..

ACE you might want to check Manthey Motors , the street tuning division of Manthey Racing as well, they have a new 510 hp kit. Based on their reputation, it should be a good product.
jan.erren@manthey-motors.de

Jean

hatchy

How did they get the boost reading? Where did they tap a vacuum line? Interesting that the boost drops off, but the power does not.

fc-racer

One thing I don't get is how all the journalists that tested the 993 Turbo missed this flat spot in the powerband. We've all felt it when we accelerate hard in 3rd or 4th gear from low rpm. The torque comes on strong around 2500rpm, keeps pulling until around 4500rpm, then seems to level off, then there is another surge around 6000rpm that pulls you right to redline.

It's so obvious that even a first time driver in my car picked it up right away. In the dyno chart above, it's also very evident. So the question I ask, how come we've never read about this in any review before? It's quite common for journalists to talk about torque curve flat spots or peaks, etc.

I wonder if disconnecting the battery would eliminate the flat spot temporarily until the ECU learns the fuel quality? Steve or the others, does the factory DME have the capability to learn or is it only responsive to the knock sensor and other sensors in real-time?

TB993tt

I have transferred data onto excel charts from one of the runs my engine did on the engine dyno, the first one is boost and the second power. Note how the seemingly erratic boost curve produces a wide smooth power curve, this is one of the reasons why I always bang on about Motronic versus fixed boost via boost controllers.


One thing I found interesting was that at the low end, ACE's stock KKK16 turbos were producing 0.2bar at 2500rpm whilst my murch larger RS K24 specials were already at around 0.3bar by 2500rpm, by 3500rpm, ACE's have managed 0.8 bar whilst mine are up to 0.98bar - lag with K24s ?- not with the right programming

Felix

I stumbled across this graph in a Porsche Service technik book. It would appear to show that Alan's boost curve isn't very far from the factory's expectation.

ACEparts_com

Thanks for that. It looks like Motronic has control!

TB993tt

BrianPA

You have 390 horsepower at the wheels and your ONLY mod is exhuast?
The torque figure seems even more absurd for a totally stock car. Are you sure your car isn't chipped?