Look at the HP vs. RPM graph

[www.planet-9.com]

A guy on P9 with a 981 S was in the process of doing mods to the intake to get more HP and was disappointed in the results. After going through the data, it appeared the throttle was not opening fully @ high RPMs --and actually closing some--relative to lower engine speeds. 4K looks to be the point where the max throttle opening starts to diminish.

I have to say, this mirrored what I saw in the track video recorded @ VIR ; I recorded the data from the OBD reader,stored it in my phone and then merged it with RaceRender. When accelerating in slow speed turns, I got an indicated full throttle, but when going down the front and back straight it looked like I was only giving it 1/2 throttle; I think Grant gave me some "stuff" about that.
I couldn't believe I wouldn't have my foot fully in it on the straight--but there it was, so I thought maybe the data or display was screwed somehow.
If this thread is correct, it may have been the real deal.

Also, if you're thinking about investing a lot of $ in aftermarket mods for your 981, you will find the thread an interesting read.

Thoughts?

Edited 1 time(s). Last edit at 12/23/2013 01:25PM by MikenOH. (view changes)

When G-Man and Michelle (Mrs. G-Man) in their 981S, and I (in my 2005 987 non-S) got together in Sept, there were some spirited 0-XX runs, with G-Man in front. I was pleasantly surprised that, although my car lagged, it wasn't by much.

Later, I asked G-Man if he had used full throttle, to which he replied he hadn't. Turns out his response may have been more accurate than even he realized...

So, if your information is correct, does that mean the 981 has some hidden h.p.'s waiting to be unleashed by a bit of ECU tweaking?

If you read that thread, there is a lot of speculation about how much "free" HP there might be out there, but we'll just have to see if this materializes.

This theory does seem to make sense in how Porsche might differentiate HP in various models--981BS vs. 981 CS, 991 vs. 981s, with
HP ratings based on ECU settings, rather than building engines with different intake/exhaust hardware.

If there were a change in the throttle opening at around 4000 RPM, I would expect to see a kink in the curve, a slope change. The curve published in the sales brochure looks fairly smooth.

It is a bit strange as the 2012 987 Boxster Black edition and the 2011/12 987 Spyders both have 320 HP...which is good, however why would Porsche purposefully set the bar lower at 315 when we (all very intelligent) follow the HP rated ad nauseum?

MIKELLIG

.... Between a properly tuned car an an out-of-tune one.
What many people don't want to believe is that you can do as many changes to the engine's hardware as you want but until you properly tune the car's ECU to those changes you will not get any power increments. You will probably get power and torque loss.
With the old cars (up to the '99 Boxster) your right foot actually controlled the throttle body' butterfly valve.
But with the advent of e-Gas, the butterfly is controlled by the ECU.
You can put a bigger TB but the ECU will try to bring everything back to spec by not allowing it to open completely.
We're not in Kansas anymore. Welcome to the age of computer-controlled everything.
That's why I love my ''98. It actually has a cable connecting my right foot to the TB.
Happy Boxstering
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

---

Racecar spelled backwards is Racecar

"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"

"If you wait, all that happens is that you get older"... Mario Andretti

"Being second is to be the first of the ones who lose" ... Ayrton Senna

from all the hardware and he blames Porsche by somehow dialing back on the throttle to limit hp/toque.

IOW, the stock intake manifold is probably optimally designed/sized -- size is important as it doesn't want to be too big to avoid the creation of standing waves that *reduce* air flow through the intake -- and well suited to the other stocks items while the bigger intake manifold and the assortment of aftermarket items the person in the thread the link pointed to combined with the intake do not work together (and probably don't work all that well separately either) and the result is less than expected and of course is blamed on Porsche.

Typical.

its power claims without running into this behavior (if the behavior is real I have not seen any data).

On the intake manifold maker's web site I see no mention of any additional tune or DME mod's mentioned to extract this extra horsepower so the assumption is the intake mod alone was all that was necessary.

If the throttle back off is real it could be explained by engine load which is derived from among other things air flow and it could be the derived/calculated engine load went off scale and as a safety factor the throttle was backed off. Had the engine load not dropped this could have been interpreted as a failure of the e-Gas system and the engine could have been disabled. At any rate, I do not believe there is anything sinister at work here, that Porsche has elected to use throttle opening to limit HP until its marketing mavens deem more HP necessary.

It reads more like the result is less than the sum of the parts/mods coupled with the lack of full understanding the true extent of the complexity and interdependencies that exist in modern engine control systems and of course the blame is placed exactly where it does not belong.

The number of tunes, exhausts, etc that do not meet their stated claims is huge. Many exhausts in particular, when put to the Dyno test, decrease torque at most or even all frequencies. But they sound good, or at last louder.

Unless one has a turbo -- in which case you can simply add more boost and maybe dump in a little extra fuel to keep things cooler, the options for producing more power are limited: generally it comes down to eliminating the manufacturer's margin for error. Can we run a bit more advance? In an ideal world, maybe. But what if it per-detonates? Can we add a bit of fuel and hope for the best at WOT? Sure, but you will certainly run a bit richer, deliver more damage to the cat. Can we change valve lift or timing? No. Raise the redline? Yikes!

Most tunes of normally aspirated cars sound like either playing with fire or FM to me.

Turbo cars are a whole different kettle of fish, especially if you are willing to seek out high octane fuel.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

... you can add a bunch of power to a normally aspirated car too, not just to forced-air induction systems such as turbos or superchargers, but it's a bit more difficult.
The ONLY way to make more HP in an internal combustion engine is to pump more air through it.
More air also means that the corresponding extra part of fuel needs to be added to the air at a ratio of 14.7:1, and this is the responsibility of the ECU after it samples the exhaust gasses by reading the O2 sensors' data.
But, you can't get more air through it unless you make things more efficient and balanced.
A less restrictive air filter by itself ain't gonna do it!
You have to find where the bottle neck is. In these cars it's generally the throttle body and intake plenums.
But simply putting in a bigger TB ain't gonna do it either.
You'd have to also free up some back pressure via mods in the exhaust (header/cats/muffler).
And there's also the matter of the intake/exhaust valves. There comes a time when they're maxed out so unless they're made bigger, it ain't gonna do it.
Finally, after all the physical mods are done, the ECU has to be told that these new parts are in the car and it has to be programmed correctly so that they all work in unison allowing for that magical mixture of 14.7:1 because it it doesn't happen, it ain't gonna do it either.
Happy Boxstering,
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

---

Racecar spelled backwards is Racecar

"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"

"If you wait, all that happens is that you get older"... Mario Andretti

"Being second is to be the first of the ones who lose" ... Ayrton Senna

Good posts--reminds me on an inquiry I made when I was looking to see if there was any HP available--without spend megabucks--for the 2.7L 987.1 car.
IIRC, the stock air filter on the 2.7l was the same used on the 3.2l--so a higher flow filter didn't seem to make sense to gain HP; likewise with the muffler--the stock 2.7l system was also used on the 3.2l so that didn't seem to be the bottle neck either. I know the headers & valves were different sizes so a set of headers might have added HP but the additional HP/$ ratio might have been very low. IIRC, the TB on the 2.7l and the 3.2l 987 motors were the same but changed when the 3.4l motor was introduced.

..and to a lesser degree to exhausts on their own.

Yes, if you mechanically re-engineer the entire air pump you can make gains. Few people do things so systematically or expensively.

In fact most improvements come down to complete systems engineering - ditto for suspension.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com

..to look into tchno-torque and what you suggest to do to complement it....

At least you've tested and explained the weak link that you address.

But chips for NA? Nah.

Grant

Grant

gee-lenahan-at-gee-mail-dot-com