So what you're saying is, EVOMS changes the car's original way of showing PSI 1-9-18 bar to a 1-14 bar?

 

Well what I was told was that there was something done as part of the flash that is causing my car to display 0-7-14 PSI on the on board computer display and that this is done by a lot of the flashes, on purpose. Again, hoping that one of the tuners clarifies because I know I will totally fail trying to do so

 

I started this thread asking for NORMAL boost values. i.e. NO TUNE, so very little of what was said in this thread is relevant to the initial question!!

I will ask this again: What is the normal boost value of a 997 turbo without tune? Stock?
What is the bar graph scale without tune? Stock?

It's incredible how many threads are around about this, and still there is no DEFINITIVE answer. Everyone replies 14 psi, but now it seems they all have scales going from 0-18 NOT 0-14. And guess what? Maybe they all have tunes as well!!!

So are all the cars with 0-18 psi scales tuned???
Are the ones with 0-14 psi scales stock without tunes, and the NORMAL boost is really around 10???

 

If flashes change the way psi is shown then does that differ from car to car? I wonder only because my friend and I both have same APR Flash and still show different psi levels. His a 2009, mine a 2007. Both sport chrono.

 

This was answered a few times in this thread, but I guess I can see how it can be confusing.

Let me try again
2007 997.1 Turbo 100% Stock
Boost gauge 1: (single digital display) MAX 17 psi with up arrow during over boost

Boost gauge 2: (analog boost gauge) shows a range of 0-18 (0-9-18) whether in sports mode or normal mode. meaning this gauge NEVER displays 0-14

I regularly see 17+ psi with the up arrow when I pull under full throttle in 2nd through 6th gear. Simple test, run from 70-90 in either 4th or 5th gear and you should see 17 psi in sports mode

I hope this was clear and helpful
-Art

PS
I think the comments about the gauge changing after a tune are helpful since it clearly indicates that if the ECU is fiddled with either by the dealer or tuner it can screw up the range. In my case, the softronic tune did not change the gauge

 

Hopefully they can come in and explain! I'd like to know the reason as to why they would need or prefer to change the boost gauge to 0-14...

 

agreed, intuitively it doesn't make much sense.

 

Sorry you are not getting your answer. My 08 997 with Sports Chrono does have a display to 18. It is bone stock.
The highest my boost has gone is 14.....

 

Apologies for thread jack.. I missed your comment about no tune.

Given the fact that we have a wide range of cars commented on inside this thread and no clear differentiator (the obvious one would have been mk1 vs mk2) it seems that something in the ECU is able to control whether the display shows 0-9-18 vs 0-7-14.

In my case, it seems a tune is involved. But to what degree, can't say until one of the tuners hops in. Although you are not interested in the tune case, note that an explanation from a tuner could shed light into how this display change may happen and could also expose perhaps why it's happening on your stock car.

FWIW, the only references I find in the manual (mk2 manual) are:

1.) pg 158: The maximum boost pressure is approx. 14.5psi (1bar).

2.) pg 65: Overboost briefly increases the engine boost pressure by approx 3psi (0.2bar).

3.) pg 65: Quickly flooring the accelerator pedal activates the overboost function in the engine unit. An arrow appears next to the boost pressure display.

4.) pg 65: There's a graphic on this page which shows 14psi with a little arrow next to it.

The manual doesn't really answer your question which is: On a stock car is the max really 14.5psi hence without overboost does it top out at 11.5psi? Or is 14.5psi the maximum boost pressure before overboost and overboost can send it to 17.5psi?

But note that aa909's comment about his mk1 car in stock form (pre-software tune) showing 0-9-18 on the analog gauge and numeric showing 17+psi during overboost, seems to answer the question.

 

I don't believe it's changing the display... but the display could be changing as a side effect of something else, perhaps something being done to the sensor values as part of the tune. I'm holding my tongue here because again, there's room for a lot of grief from me trashing the explanation so I'm hoping someone else can provide a correct detailed answer.

 

Ok, as far as I know, my car is bone stock. The gauge goes from 0-14.

 

I gave you a fairly definitive answer

OEM with sport chrono should show 0-18 PSi and will register 17 PSI on the street.

Without sport chrono engaged (e.g. sport mode off), the most I believe I've seen is 14 PSI.

If you have OEM with sport chrono and you see 0-14 PSI on your gauge, your ECU needs to be updated and unless you have done any aftermarket tunes (I have no idea if they reset your gauge to 14 PSI max) your dealer should fix it. Takes like 60 seconds with PIWIS. In the software world this would be called a "bug" and is not normal.

In lower gears it is difficult to see you're at maximum boost. A 5th gear pull at 70mph reliably showed 17 PSI for me every time. Trying to pull in lower gears it wasn't easy to eyeball my boost going to 17.

The only question I personally cannot answer with absolute proof is what a completely stock 997.1 without sport chrono shows. I believe it should be 0-14 PSI and max out at 14 PSI under full load.

 

Ok, so a bone stock 997.1 or .2 should show a 0-18 psi bar graph.
Mine doesn't. So I have to find out why.

Irrespective of the scale, both show about 1/2 the way between the middle value and the end value. i.e. if you have a 0-14 bar graph you display around 10, and if you have a 0-18 around 14.
So, the actual position of the bar on the two seem to be the same but the scales are different.

I do know that the boost values are calculated by the ECU and not the display. The data is then sent to the display. However, I also know that the display of the boost gauge is controlled by the instrument cluster, based of threads about the durametric. Whether there is a setting for scale I do not know but I suspect there is and it will be set according to whether you have the Sport Chrono or not. Therefore I think, there is a programming error in my instrument cluster setting the scale at 0-14 instead of 0-18, seeing that many others have bone stock 997's and they show 0-18.

This answers a lot of mysteries and if we can solve this, we can save a lot of people money when they go to find out why there boost values are lower than everyone says they should be!! It may be something as simple as the scale being wrong due to a programming issue.

I am sure some of the tuners can answer this. After all, if they can change it....

 

Hopefully I can shed some light on the boost discrepancies that each model year cars have. For the 997.1 turbo and the 997.2 turbo, the boost gauge displays a "programmed value" and does not correlate to the actual manifold pressure. Porsche started this "programmed" boost gauge after having many customer service questions on the 996TT which showed "actual boost" (not programed).

The 996TT was reading the actual and accurate boost pressure in the Y-pipe before the throttle body. The problem was that when the throttle body closed rapidly, the boost gauge would show an arbitrarily high boost reading on the gauge due to the high pressure in the Y-pipe before the boost was recirculated by the diverter valves. Some customers would complain on stock vehicles that they were seeing 1.6 bar of boost when they were modulating in and out of boost.

When the 997.1TT was released in 2007, this was the end of a real boost gauge that showed an accurate reading It is programed to show 14psi (1.0 bar) in non sport mode and 18psi (1.22 bar) in sport mode. Although the car may or may bot be making this boost level, this is what the gauge will read. In some of our software calibrations, we will run 20-23 PSI of boost in both sport and non sport mode and the OEM boost gauge will only display 14psi (1.0 bar) in non sport mode and 18psi (1.22 bar) in sport mode.

For the 997.2TT, this is again a programmed boost gauge. It has very little to do with the actual boost pressure in the manifold. Since the 997.2TT has a TQ based ECU, boost pressure is only related to the programmed TQ value. If you were to put an external boost gauge on a 997.2TT, stock or modified, you would be surprised how the boost curve actually looks compared to what the OEM boost gauge is displaying. Typically, the boost will spike up at 14 psi, drop to 10 psi in the mid range, then slowly climb up to about 12 psi by redline.

Bottom line, the only way to accurately monitor and see the actual boost on the 997.1TT and 997.2TT is to install an external manifold pressure boost gauge. I hope this helps with some of the questions.

 

Wait a minute! (I love this thread BTW, I've been perplexed as well). I have gone into overboost a number of times and have also found that the boost arrow appears on the bar chart and on the digital psi reading. "If you go over that" - suggests that overboost is going over 14 or 17 psi. I've been in overboost and seen readings well below the max, i.e. arrow is on the right, but the boost reading is below the max. In running boost, I've also found that the power seems to spool up faster than the guage does. I wonder if the psi reading is somewhat delayed and inaccurate.

I have a '08 and my readout bar goes to 9 then 18 - all the time. You will only see the overboost arrow with the Sport button on - exactly how it works on my car.