CARV

Thanks PV, you're welcome. I'm not thinking it's an ECU delay issue.

Can you confirm that you experience it at full throttle only or at other times too?

Gary, thanks, yeah I think there is the 4800-5000 or maybe 5600 rpm WOT spot and the partial throttle 3000+rpm spot. Both important to figure out though!

CARV

1999, yeah Evo's dynos are very interesting. As an engineer, those curves are the things that drive you nuts yet are what you get the most satisfaction out of solving.

There are many variables that could be causing that torque issue at 4800rpm on the S and 5600rpm on the non-S.

What is really interesting to me is that the Evo V-Flow intake on the non-S seemes to have tuned it out, yet didn't help it on the S.

A combination of contacting Porsche with dissatisfaction along with the tuners such as GIAC, PSI etc. and finding out what they changed and didn't change might shed some light on the subject.

At this point it could be as easy as some part being faulty to having to go back into the ECU and adjust A/F, timing and variocam maps to get it right.

In the end, it might not be the software that gives the biggest peak torque/ power increase, but gives the best shaped curve with the most area underneath. That should be the goal of the tuners. We just have to figure out where this flat spot is coming from.

It is so obvious on Evo's plots that I can't imagine this hasn't already been addressed at both Porsche and the tuners shops.

edited: for V-flow intake being responsible for the improvement on the non-S

1999Porsche911

The drop at 5600 may be the resonance flap popping open. You might try playing with it. Try leaving it open all the time and closed all the time to see if there is a change. You can put a tee on the vacuum line and connect a vacuum gauge and see exactly when the valve opens and closes.

CARV

Ya, I need a car first.........LOL

If I were Evo/GIAC/PSI etc., I would be having pizza delivered to my new home at the dyno until this thing was solved. I don't think it has to be that abrupt or of that magnitude.

The resonance valve is a good idea and possibility. I find it interesting that Evo's V-flow intake seemed to have solved it on the non-S while the S with the V-flow still has the issue.
This can be improved imho, the tuner group/Porsche just has to hear from people to get motivated to do it unfortunately.

I'm going to search for some more S vs. non-S dynos to see what others have done.

CARV

Well, after reviewing the dyno data from multiple sources, it looks like the 997 has the 5600rpm flat spot and the S has the 4800rpm flat spot on all the graphs.
The non-S car's flat spot is milder than the flat spot on the S, although, the torque gain prior to the flat spot is much greater on the S.

I've emailed GIAC, Evo, PSI, AWE, Powerchip and Superchips to see if they've addressed it.
Any differences in the induction system of the S may play a large part in this. Multiple different exhausts and cold air kits along with software haven't seemed to affect the characteristic.
I wouldn't be surprised to see different variocam parameters contributing to this also.

Will post when more info comes back.

1999Porsche911

EVO has already fixed it. Look at their website under 997 - programs.

CARV

Like I said above, they fixed the non-S, but the S still has the issue even with their V-flow intake which solved it on the non-S

Go back and look at the S graph........that's not fixed and is what I'm talking about.

PV

Both, but more pronounced a partial throttle, and in particular when taking the foot off slowly.

Can you show which flat spot you ae talking about?

1999Porsche911

I would bet alot of that might be the egas signal. Seen plenty of problems with egas surging on pedal let up. I like my cable.

CARV

Here are the charts of the WOT Evo dyno runs. I marked what I would be shooting for as a tuner in remapping the A/F, timing, variocam and resonator.
Note that I left "some" of the curvature in there. The reason is that part of that curvature is probably due to the inherent volumetric efficiency of this specific engine ie. cams, porting, valves, comb. chamber, manifolding etc.

CARV

And the HP curve.....keep in mind I didn't crunch the numbers, these are just the shapes you'd be shooting for. All WOT of course. With my curves, although there is a very slight slope change at approx. 5000rpm, it is so gradual and mild that you wouldn't feel it.

CARV

PV do you have an S or non? They really each have their own characteristics.

It is common for a manufacturer to add timing in the area of light to mid load and throttle around a cruising rpm such as 2500-3000rpm to improve fuel mileage.
When you come out of that range either in throttle or rpm, the timing could be decreasing giving you the feeling of a flat spot,
or a momentary increase in responsiveness to decreasing throttle when passing into and out of that range could be involved.
I've seen this on many modern ECU controlled engines.

If you look at the above graphs of the Evo mods, they did reduce the WOT flat spot at around 3000rpm, but didn't help the one at 4800rpm.

Their non-S graphs look very well tuned and would take care of the WOT flat spot on a non-S car if they're accurate. The partial throttle issues may or may not be resolved though.
A test drive would help prove that out, but since it's an intermittant map area people are passing through, it may be difficult to determine without some time with the mods.

Imho, the first thing to do is to call the service dept. and see if there are any bulletins out for these response issues.
Since it's hard to say if your particular case is simply the engine's response characteristics (likely) or something that needs to be looked at, check with the dealer first.
If all of that checks out, you can start looking for mod options if the response anomalies still bother you.

PV

CARV: thanks for the complete analyzes. Well done. I'm driving the non-S.

If I would describe my experience, I would tend to go for your story about the motor characteristics. It looks like they have some (look it is a very small detail we are talking about, but sometimes noticable and therefor I reacted on the thread) delay built in the intermediate range. I see some dips and bumps in WOT curve, but didn't expect to feel that at less than full throttle.

Looking forward to see more data. Anything on the cylinder filling, valve and air intakes. Whatever, I like to look at those things and read the theories and test results. Personally, I think it is a pitty that Porsche is not publishing more of what they do and measure. I know it has to do with competition and art and so on, but still. A nice video of windtunnel experiments or so.

OCBen

Good work CARV!

CARV

Thanks guys. PV, have you gone to the P website and watched the video in the 911 section called "precision" ?
It's pretty good although they don't get into specifics of what they did during the design and testing.
I too would love a "911 uncovered" video of specific tests and analysis from Porsche.

As more info comes in from the different areas, I'll post it for discussion.
One of the reasons I'm buying a 997 is the thoroughness with which Porsche optimized this car.
But in a funny way, it is also satisfying to have a couple of things to optimize and improve yourself in your own P-car imho.