Discussed before but not clear: Normal Boost values?
#76
03-03-2013, 07:56 PM
Join Date: Nov 2012
Location: Montreal
Posts: 267
Rep Power: 24 
yes I did, but just went back...there's lots of noise in this thread!!
After reading it again, yes your answer seems to be the right one, sort of got lost with some of the others.
And I think, my boost IS 14 going to 17 just the scale is wrong for the reasons you say!
Thanks
#77
03-03-2013, 08:00 PM
Join Date: Nov 2012
Location: Montreal
Posts: 267
Rep Power: 24 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.
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.
#78
03-03-2013, 08:21 PM
One more time
stock 997.1 w/sports chrono, analog boost gauge displays 0-18
if you have the sports chrono function and displaying 0-14 then your ECU needs to be adjusted by the dealer. take it to the dealer and have it cleared up
#79
03-03-2013, 08:44 PM
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Join Date: May 2010
Location: South Beach, Miami
Age: 42
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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.
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.
It means your boost is increased higher than what it is normally for a given speed and RPM.
Only when your ECU is going for it's maximum boost (which doesn't happen at every given engine RPM/speed) would you see it hit 17 PSI.
Just applying my IT / engineering background here
#80
03-03-2013, 09:09 PM
The arrow only indicates your car has activated overboost mode.
It means your boost is increased higher than what it is normally for a given speed and RPM.
Only when your ECU is going for it's maximum boost (which doesn't happen at every given engine RPM/speed) would you see it hit 17 PSI.
Just applying my IT / engineering background here
It means your boost is increased higher than what it is normally for a given speed and RPM.
Only when your ECU is going for it's maximum boost (which doesn't happen at every given engine RPM/speed) would you see it hit 17 PSI.
Just applying my IT / engineering background here
#81
03-03-2013, 09:15 PM
Get yourself a durametric cable. You will be able to see requested boost and actual boost. Before I flashed my car, I could never peg the dial on the dash. Boost is not just a function of your programmed ecu but also the hardware on your car.
#82
03-03-2013, 09:20 PM
Join Date: Nov 2012
Location: Montreal
Posts: 267
Rep Power: 24 dude, you're kidding right? honestly you've gotten so many direct answers.
One more time
stock 997.1 w/sports chrono, analog boost gauge displays 0-18
if you have the sports chrono function and displaying 0-14 then your ECU needs to be adjusted by the dealer. take it to the dealer and have it cleared up
One more time
stock 997.1 w/sports chrono, analog boost gauge displays 0-18
if you have the sports chrono function and displaying 0-14 then your ECU needs to be adjusted by the dealer. take it to the dealer and have it cleared up
#83
03-03-2013, 09:20 PM
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. ... 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.
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.
so I still have a question which is am I to assume the portion in bold above applies to the mk2 as well and if so, why does my particular car (mk2) seem to show 14psi in both non-sport and sport modes? And why does aa909's car (mk1) show 18psi in both non-sport and sport modes? I assume my car has been programmed that way, in my case by my EVO ECU flash? Just curious as again I'm not being **** about the reading.. just want to know the OBC is working properly.
Last edited by Zero911; 03-03-2013 at 09:23 PM.
#90
03-11-2013, 12:56 PM
I really never push the car hard on throttle or past 4000 rpm until the oil temp is at least 175+ F so I don't know if full over boost is available before the engine is fully warmed up. I'm no expert but probably not a great idea to push it hard before the engine is fully warm anyway