Indicated boost - 996TT

[robinm]

My 996TT usually only indicates 0.6 max boost. Very occasionally I see 0.7, but only momentarily.

Is this normal? How accurate is the indicator? I know it is supposed to boost to 0.8

[roshambo]

Much debate over this one.

"On the 911 Turbo, a maximum boost pressure of 0.8 bar is available from as low as 2,700rpm."

Thats from the Porsche website.

Others will tell you 0.6 , 0.7, 0.8 & even 0.9 standard bar are normal.

From my own experience, my TT peaks at 0.8

Ro.

[Barry_J]

roshambo said:

Thats from the Porsche website.

Have you got a link to that please?

[Glenn McMenamin]

Barry_J said:

roshambo said: Thats from the Porsche website. Have you got a link to that please?

This has been discussed a few times i think, and number vary.

On my standard turbo, on a cold evening i got a momentary glimps of 1.0 !!!, this is obviously due to the conditions etc. i normally see 0.7-0.8 though.


G.

[roshambo]

go to www.porsche.co.uk, then pull down the "911" next to News & select 911 Turbo. Then click on "Engine" on the left & then "Turbocharging" & its in the text.

Ro.

[Barry_J]

roshambo said:

click on "Engine" on the left & then "Turbocharging"

Thanks Ro. I get as far as "Engine" (on the right rather than on the left) but don't see "Turbocharging". May be a problem with my browser

[robinm]

My query was not so much what the 996TT max boost should be (I believe the Owners Manual confirms that to be 0.8).

What I am concerned about is the indicated 0.6 that I am getting. Is this because the indicator is inaccurate or do I have pressure loss somewhere - dump valve maybe?

>> Edited by robinm on Monday 22 August 15:36

[nel]

One thing that could limit the boost is if the ECU has detected detonation, high intake temperatures, etc. It goes into damage limitation mode and limits the boost to prevent engine damage. Can result from poor fuel quality too. Other than this the same symptoms could no doubt be caused by mechanical issues with the turbos, their wastegates or the dump valves as you suggest.

On a 993tt the ECU can be reset by disconnecting the battery for 20 seconds or so - it then spends the first few minutes when the engine is restarted verifying its parameters to determine its optimum operation mode. Unfortunately I have no idea whether the same logic applies to a 996tt - SORRY!

[911 habit]

The ECU has different programs or modes. If the system detects a problem it will put you into a ‘safe’ or get you home mode – this limits the boost to 0.5 bar. I believe that there are two other modes, high performance and ecconomic modes. Every time I get my TT back from an OPC it appears to be in ecconomic mode and it takes a good blast or two through the gears to put it back to performance mode, which gives the full boost back.

[roshambo]

I do believe its a "learning" ECU that changes with your driving style.
Pootle about everywhere at 3k revs then the ECU learns this, drive everywhere full on & the ECU adapts again, this could be your "problem" as anything under 0.6bar sounds wrong.

Ro.

[mart1n]

You should definitely be able to get at least 0.8 bar on a standard engine and 1.0 bar on an X50 engine but, as others have said, you probably need good 98 octane fuel like Optimax. Also, the periods of maximum boost can be very short and difficult to see when you are trying to hang on, try a video camera pointing at the dashboard if you have one.

[robinm]

Thanks for all those.

I definitely don't "pootle" very often, but I get what you are saying. I will try a prolonged period of enthusiastic application and see what happens.

I have been using Optimax.

Thanks again to all.

[nel]

For what it's worth the buyers advice for 993TTs was to check the 0.8 barg were achieved during the test drive. The technique was to put the car in 3rd on a suitable piece of tarmac, absolutely floor it and watch the boost gauge. Once the boost arrives then fairly quickly the required 0.8 should be reached.

[I think the choice of 3rd was just to use a gear where the on-boost period would be long enough for a readout without hitting ridiculous speeds!]