Menu toggle

997 Turbo boost figures

Alex L

Alex L

PCGB Member
Member
Hi guys

I believe the 997 Turbo is supposed to get to 1.2 bar boost pressure with Sport Mode and overboost (1.0bar in Normal Mode). The Drivers Guide does show a pic of 1.2 bar with overboost arrow.

Anyway, recently I found a quiet stip of straight dry road, and had a play with the boost figures. I only ever use 99 octane Shell vPower fuel.

Normal Mode
If I put the car in 6th gear, then I can get 0.9 bar for about 1 sec, then it drops to 0.8 bar and stays there.

Sport Mode
Again, in 6th gear, I can get to 1.1 bar for a split-sec with the overboost arrow showing, then it drops to a constant 1.0 bar.

I am wondering if the reasons a lot of the guys with manual cars that are seeing 1.2 bar is because they have reduced the exhaust back-pressure from switching to an aftermarket exhaust?!
questionicon.gif


Either that or newer Turbos are being tuned-down slightly compared to early factory productions?!

What do you think? I would interested to know what other 997 Turbo owners have seen.
 
Hi Alex

Have to admit I've paid little attention to this gauge to-date. A few thoughts :
- gauge could be displaying averages rather than max values - the word "approx." does also feature in the manual I note.
- was the engine suitably loaded, e.g. were you accelerating on an incline rather than a flat straight, without which you might under-read I suspect.
 
Think I have an answer...

Max boost pressure increases with air temperature (the electronics try to compensate hp loss due to unfavourable environmental conditions...). Thus, in hot weather conditions the boost pressure is higher than in colder climate.
Click to expand...

When I was getting 1.0-1.1 it was only about 5 or 6 degrees C.
 
ORIGINAL: Alex L

Think I have an answer...

Max boost pressure increases with air temperature (the electronics try to compensate hp loss due to unfavourable environmental conditions...). Thus, in hot weather conditions the boost pressure is higher than in colder climate.
Click to expand...

When I was getting 1.0-1.1 it was only about 5 or 6 degrees C.
Click to expand...

Alex,
I always thought this was the other way round, that the boost was higher in colder conditions.Thats why we have intercoolers to cool the charge air temperatures?.I thiunk that because you are saying that in sport mode you are seeing 0.2 bar more constant, than in non sport mode, then you are running ok.Try nailing the car in 6th gear, earlier in the rev range, or under more load, eg uphill, and see if you are seeing 1.2 bar.On the Mitsi Evos in cold weather, we would see fuel cuts, due to higher boost pressures being obtained, by the cold weather.If you are unsettled, give Mike Cooper a ring at DMS, and have a chat, he seems to be an aimiable chap.Let us know how you get on.I finding the wait for my car to be getting slower and slower.Roll on April, regards, SIMON.[:D]
 
No, it does make sense.

As the air is already colder and more dense the engine doesn't need to apply so much compression to the air for the maximum power output to be achieved.

[:D]
 
Both you guys are correct.

Cars with mechanical boost regulation will produce more boost pressure in cold weather.

As for your electronically controlled cars if the electronics allowed more boost pressure in warm weather that could help make up for lost performance. The only problem with this is that this will put even more heat into the intercoolers than the warm climate has already added. My guess is that maybe then the ignition timing would be retarded a little which would then mean less power.
 
How does this work? 1 bar of boost is still 1 bar no matter how hot or cold it is. The wastegate is a dumb device and simply compares the actual boost pressure to either a spring or a secondary boost signal. On a cold day you will produce more power at the same boost levels as the air is more dense, but your boost pressure should still be the same. My boost needle hits the same max boost irrespective of temp but the car is noticably more responsive and quicker in cold weather - but max boost pressure still remains the same.

 
Scott, maybe it only effects people that are in fact overboosting. I have been told that with my setup of parts to run a .2bar lower spring than the actual boost pressure I want to maintain. Lots of people have confirmed this and some have stated that they get a higher boost level in colder weather. I'm pretty confident that with my ebc I won't have any problem getting too much boost. I only have a .5bar spring in my Tial too.
 
stock electronic boost gauge is only an estimation based upon flow going past the MAFs. hook up a true gauge to a pressure source and i bet you'll see 1.2.
 
I guess that figures :)

People say the 930 gauge is not very accurate. I found mine accurate up to .7bar (I didn't go higher due to not having a good turbo and IC).

The 964t gauge can only read up to 0.7bar and no higher...

How does the 993tt one do ? [:D]
 
ORIGINAL: nathan 1981 930 G50

I guess that figures :)

People say the 930 gauge is not very accurate. I found mine accurate up to .7bar (I didn't go higher due to not having a good turbo and IC).

The 964t gauge can only read up to 0.7bar and no higher...

How does the 993tt one do ? [:D]
Click to expand...

Boost gauge reads 0.8 bar max when you accelerate hard.
 
You must log in or register to reply here.

Posts made and opinions expressed are those of the individual forum members

Use of the Forum is subject to the Terms and Conditions

Disclaimer

The opinions expressed on this site are not necessarily those of the Club, who shall have no liability in respect of them or the accuracy of the content. The Club assumes no responsibility for any effects arising from errors or omissions.

Porsche Club Great Britain gives no warranties, guarantees or assurances and makes no representations or recommendations regarding any goods or services advertised on this site. It is the responsibility of visitors to satisfy themselves that goods and/or services supplied by any advertiser are bona fide and in no instance can the Porsche Club Great Britain be held responsible.

When responding to advertisements please ensure that you satisfy yourself of any applicable call charges on numbers not prefixed by usual "landline" STD Codes. Information can be obtained from the operator or the white pages. Before giving out ANY information regarding cars, or any other items for sale, please satisfy yourself that any potential purchaser is bona fide.

Directors of the Board of Porsche Club GB, Club Office Staff, Register Secretaries and Regional Organisers are often requested by Club members to provide information on matters connected with their cars and other matters referred to in the Club Rules. Such information, advice and assistance provided by such persons is given in good faith and is based on the personal experience and knowledge of the individual concerned.

Neither Porsche Club GB, nor any of the aforementioned, shall be under any liability in respect of any such information, advice or assistance given to members. Members are advised to consult qualified specialists for information, advice and assistance on matters connected with their cars at all times.

Porsche
Lockton
Pirelli
Officially approved
Oracle Finance
WEX Esso
Collecting Cars
Archant Dialogue
Back
Top