996t boost pressure - leak?
Discussion
I've very recently bought a 996t and overall am very pleased with the purchase. It's a very accomplished car and feels very well put together.
However, there's a couple of things that are nagging at the back of my mind.
Firstly, it's pretty loud. I believe it has the stock exhaust, but from listening to others talk about them, I was expecting it to be much quieter and it's fairly comparable to some sports exhausts I've heard. It has a fairly deep bass rumble when cruising. If it is the stock exhaust, perhaps it's leaking?
Secondly, I'm fairly used to quick cars but it doesn't feel quite as fast as I'd imagined. There is quite a bit of hesitancy before the turbos kick in, and even then it's rapid but not outrageous. It boosts to 0.6 but never any higher. That said, it's probably running on 95 octane fuel. Am I just expecting too much, or do most other standard cars always hit 0.7 or more? Perhaps an inlet leak?
However, there's a couple of things that are nagging at the back of my mind.
Firstly, it's pretty loud. I believe it has the stock exhaust, but from listening to others talk about them, I was expecting it to be much quieter and it's fairly comparable to some sports exhausts I've heard. It has a fairly deep bass rumble when cruising. If it is the stock exhaust, perhaps it's leaking?
Secondly, I'm fairly used to quick cars but it doesn't feel quite as fast as I'd imagined. There is quite a bit of hesitancy before the turbos kick in, and even then it's rapid but not outrageous. It boosts to 0.6 but never any higher. That said, it's probably running on 95 octane fuel. Am I just expecting too much, or do most other standard cars always hit 0.7 or more? Perhaps an inlet leak?
yajeed said:
I've very recently bought a 996t and overall am very pleased with the purchase. It's a very accomplished car and feels very well put together.
However, there's a couple of things that are nagging at the back of my mind.
Firstly, it's pretty loud. I believe it has the stock exhaust, but from listening to others talk about them, I was expecting it to be much quieter and it's fairly comparable to some sports exhausts I've heard. It has a fairly deep bass rumble when cruising. If it is the stock exhaust, perhaps it's leaking?
Secondly, I'm fairly used to quick cars but it doesn't feel quite as fast as I'd imagined. There is quite a bit of hesitancy before the turbos kick in, and even then it's rapid but not outrageous. It boosts to 0.6 but never any higher. That said, it's probably running on 95 octane fuel. Am I just expecting too much, or do most other standard cars always hit 0.7 or more? Perhaps an inlet leak?
Congrats on the purchase. However, there's a couple of things that are nagging at the back of my mind.
Firstly, it's pretty loud. I believe it has the stock exhaust, but from listening to others talk about them, I was expecting it to be much quieter and it's fairly comparable to some sports exhausts I've heard. It has a fairly deep bass rumble when cruising. If it is the stock exhaust, perhaps it's leaking?
Secondly, I'm fairly used to quick cars but it doesn't feel quite as fast as I'd imagined. There is quite a bit of hesitancy before the turbos kick in, and even then it's rapid but not outrageous. It boosts to 0.6 but never any higher. That said, it's probably running on 95 octane fuel. Am I just expecting too much, or do most other standard cars always hit 0.7 or more? Perhaps an inlet leak?
Sounds like there might be an issue with your car, as the acceleration on mine has never felt anything less than brutal in the 2 years I've owned it.
(it's a standard car, and boosts to 0.7 normally).
With regards to boost reading, remember the process in analogue whereas the display is digital, and it may just be that the moment of peak boost of 0.7 happens between the two moments when you get a 0.6 reading. (you won't/can't sustain 0.7 boost for any length of time or you'll be banging the limiter)
I suggest the first step would be to empty the tank and get a few full tankfulls of 97ROM through the system. That'll hopefully improve the situation but I'm not sure it'll account for the lack of perfromance you seem to be talking about.
Good luck.
p.s. with regards the noise, I think the 996 turbo gets maligned as some whisper quiet car; It's still a 3.6 flat 6 engine, and they do sound great at idle/low revs. It's only when you're on hard throttle that a lot of the noise is converted to performance, and therfore doesn't sound as good as an N/A model.
monthefish said:
Congrats on the purchase.
Sounds like there might be an issue with your car, as the acceleration on mine has never felt anything less than brutal in the 2 years I've owned it.
(it's a standard car, and boosts to 0.7 normally).
With regards to boost reading, remember the process in analogue whereas the display is digital, and it may just be that the moment of peak boost of 0.7 happens between the two moments when you get a 0.6 reading. (you won't/can't sustain 0.7 boost for any length of time or you'll be banging the limiter)
I suggest the first step would be to empty the tank and get a few full tankfulls of 97ROM through the system. That'll hopefully improve the situation but I'm not sure it'll account for the lack of perfromance you seem to be talking about.
Good luck.
Thanks for the quick response. It's got reasonably new turbos and has just been serviced, so hopefully if it were anything major, it'd have been spotted by the OPC. Sounds like there might be an issue with your car, as the acceleration on mine has never felt anything less than brutal in the 2 years I've owned it.
(it's a standard car, and boosts to 0.7 normally).
With regards to boost reading, remember the process in analogue whereas the display is digital, and it may just be that the moment of peak boost of 0.7 happens between the two moments when you get a 0.6 reading. (you won't/can't sustain 0.7 boost for any length of time or you'll be banging the limiter)
I suggest the first step would be to empty the tank and get a few full tankfulls of 97ROM through the system. That'll hopefully improve the situation but I'm not sure it'll account for the lack of perfromance you seem to be talking about.
Good luck.
As for lack of performance, i'd say it feels Cerbera fast (and my memory is probably rose tinted) below three figures, so it could just be that I'm not sure how to drive the car properly yet and am judging it unfairly. I'll probably get it checked over by a specialist anyway, just to be doubly sure.
monthefish said:
p.s. with regards the noise, I think the 996 turbo gets maligned as some whisper quiet car; It's still a 3.6 flat 6 engine, and they do sound great at idle/low revs. It's only when you're on hard throttle that a lot of the noise is converted to performance, and therfore doesn't sound as good as an N/A model.
That's pretty much how I'd describe it - a burble at the bottom end of the rev range (which is much more pronounced than the Boxster S it replaced) and a reasonable noise further up the rev range, though much quieter comparatively. At the top end it's quiet enough to hear me swearing and laughing (despite only being rapid performance).
Both of my concerns could just be a result of reading about the cars too much and setting my expectations so very high.
yajeed said:
I've very recently bought a 996t and overall am very pleased with the purchase. It's a very accomplished car and feels very well put together.
However, there's a couple of things that are nagging at the back of my mind.
Firstly, it's pretty loud. I believe it has the stock exhaust, but from listening to others talk about them, I was expecting it to be much quieter and it's fairly comparable to some sports exhausts I've heard. It has a fairly deep bass rumble when cruising. If it is the stock exhaust, perhaps it's leaking?
Secondly, I'm fairly used to quick cars but it doesn't feel quite as fast as I'd imagined. There is quite a bit of hesitancy before the turbos kick in, and even then it's rapid but not outrageous. It boosts to 0.6 but never any higher. That said, it's probably running on 95 octane fuel. Am I just expecting too much, or do most other standard cars always hit 0.7 or more? Perhaps an inlet leak?
My Turbo is plenty loud enough for my tastes.However, there's a couple of things that are nagging at the back of my mind.
Firstly, it's pretty loud. I believe it has the stock exhaust, but from listening to others talk about them, I was expecting it to be much quieter and it's fairly comparable to some sports exhausts I've heard. It has a fairly deep bass rumble when cruising. If it is the stock exhaust, perhaps it's leaking?
Secondly, I'm fairly used to quick cars but it doesn't feel quite as fast as I'd imagined. There is quite a bit of hesitancy before the turbos kick in, and even then it's rapid but not outrageous. It boosts to 0.6 but never any higher. That said, it's probably running on 95 octane fuel. Am I just expecting too much, or do most other standard cars always hit 0.7 or more? Perhaps an inlet leak?
Are you sure the exhaust is stock? Even if it appears stock some owners can poke holes in the mufflers or due other goofy things that make the thing louder without being obvious. And produce questionable performance "gains", as in losses..
The car is quick but of course there are quicker cars.
There are cars that while slower feel quicker. The Turbo runs a 9.4:1 compression ratio which means it suffers some from low end torque from idle to when the turbos kick in. They do not kick in under rather sedate driving. You can turn on the boost gage and observing the boost level while driving and get a feel for when the turbos are working and when they are not.
Anyhow, the car lacks for low end grunt. This can make the car seem slow as the driver shoves the gas pedal to the floor and until the turbos start making boost the car's acceleration can be a bit tame. Mind you once the turbos start to work it is you better have the car pointed where you want it to go cause it is going to get there pretty darn quick.
For the issue of 0.6 bar boost... this may be all the boost that is required for the DME to meet the torque demanded by you the driver through the gas pedal.
Also, in lower gears you may not see higher levels of boost as the lower gears multiply the torque the engine produces.
For max. boost I have to have plenty of room and an empty road and moving along at around 2.5K rpms in 4th gear or higher shove the pedal through the carpet pile and then hang on. Boost climbs and will reach 0.7 bar in hardly any time (and in certain conditions (higher elevations) climb even higher to an observed 0.9 bar). But you have to have quick eyes. Boost drops off as rpms climb.
That is why in higher gears one has a better chance of seeing the boost reach whatever level is reaches and remain there for a while. The engine doesn't gain revs so quickly.
Boost leaks generally result in a much lower max. boost level and often are accompanied by CEL and error codes which point to a fueling problem. Fueling since if the intake leaks the engine is overfueled.
Best to get it checked - but often ther is forum hype which takes a very small difference and magnifies 100x...so depending what car you have come from brutal may or may not be the right description...
Some 0-60s as context (not sure how fast you went and i know this isn't a perfct yardstick)...
996 C2 - 5.8s
E46 m3 - 5.0s
997 C2 - 4.8s
Csl - 4.7s
E92 m3 - 4.5s
996 gt3 - 4.4s
CERBERA - 4.2s
996 TURBO - 4.1s
997 TURBO 3.6s
So th turbo is quick, but not too far off a cerbera - which will naturally feel quicker due to rawness...
Some 0-60s as context (not sure how fast you went and i know this isn't a perfct yardstick)...
996 C2 - 5.8s
E46 m3 - 5.0s
997 C2 - 4.8s
Csl - 4.7s
E92 m3 - 4.5s
996 gt3 - 4.4s
CERBERA - 4.2s
996 TURBO - 4.1s
997 TURBO 3.6s
So th turbo is quick, but not too far off a cerbera - which will naturally feel quicker due to rawness...
Thanks for all the responses.
I'm not totally sure the exhaust is stock, but it certainly looks it. I'll take a closer look. I suppose if its not, and the car has exhaust and chip then .6 could be a significant drop in boost (doesnt explain the lack of errors though).
It's all guesswork though, and probably just me worrying over nothing. I'll fill it with premium unleaded first.
If that doesnt spice it up, I'll go and introduce myself to my local specialist and get it looked at.
I am pretty picky when it comes to engine linearity though - a bike remapper explicitly told me not to cam my bike because I felt a minor dip in delivery that he could subsequently barely see on the dyno. Rockster's description of the engine characteristics are exactly what I felt.
I'm not totally sure the exhaust is stock, but it certainly looks it. I'll take a closer look. I suppose if its not, and the car has exhaust and chip then .6 could be a significant drop in boost (doesnt explain the lack of errors though).
It's all guesswork though, and probably just me worrying over nothing. I'll fill it with premium unleaded first.
If that doesnt spice it up, I'll go and introduce myself to my local specialist and get it looked at.
I am pretty picky when it comes to engine linearity though - a bike remapper explicitly told me not to cam my bike because I felt a minor dip in delivery that he could subsequently barely see on the dyno. Rockster's description of the engine characteristics are exactly what I felt.
Edited by yajeed on Monday 1st April 21:25
Edited by yajeed on Monday 1st April 21:26
The specialist I bought mine through told me that the majority of cars they now see are not putting out the original power, due to a number of common faults, yet the owners are unaware because even if the power is 10% down they are still swift. Happily, faults are fixable and if the car isn't quick enough for you stock the question to ask is how quick do you want it - there are very good specialists who can make it go however fast you want. There is some turbo lag which you can minimize by keeping the car "on cam". The boost meter on the OBC is not perfect I am told. Mine shows 0.9 bar easily when I give it a quick blast, it is a x50 with further upgrades though. With a sports exhaust it is very load when cold, quietens down a fair bit when warm, after 3 months I have got used to the noise which I thought would be a pain on m/way but isn't too bad.
Congrats on buying one, and have fun getting it up to your expectations! What part of the country are you in?
Congrats on buying one, and have fun getting it up to your expectations! What part of the country are you in?
I would say on average 3 out of 4 turbos are not running perfect and that is based on seeing around 3 turbos a week, sometimes more.
You have to remember that these are 10 year old cars in most cases, and the pressure system on these cars is complex.
A standard k16 car will see 0.7/0.8 bar in 4th gear full throttle. A k24 (x50/s) will see 0.8/0.9 bar. What you see, assuming everything is okay, is affected by ambient temps, adaption values (yes there are boost adaption values), octane, intake temps etc.
Octane is the biggest killer in the 996t - you run 95 and it will feel like your pulling a lorry behind you compared to 99.
Adaption values are also important - ever noticed on a motorway how you can gently overtake without registrating boost, or very little. That is because boost response adapts, so you get better mpg etc. Give it a lead foot for several miles and notice how the boost responds quicker.
Just because your car reads 0.8 bar, does not mean it gives you 0.8 bar of performance. You can still have a boost leak - that is a common misconception about these cars. They are boost (load) driven target cars, so provide the load values are reached, it will do so with the minimum amount of boost required.
K.
You have to remember that these are 10 year old cars in most cases, and the pressure system on these cars is complex.
A standard k16 car will see 0.7/0.8 bar in 4th gear full throttle. A k24 (x50/s) will see 0.8/0.9 bar. What you see, assuming everything is okay, is affected by ambient temps, adaption values (yes there are boost adaption values), octane, intake temps etc.
Octane is the biggest killer in the 996t - you run 95 and it will feel like your pulling a lorry behind you compared to 99.
Adaption values are also important - ever noticed on a motorway how you can gently overtake without registrating boost, or very little. That is because boost response adapts, so you get better mpg etc. Give it a lead foot for several miles and notice how the boost responds quicker.
Just because your car reads 0.8 bar, does not mean it gives you 0.8 bar of performance. You can still have a boost leak - that is a common misconception about these cars. They are boost (load) driven target cars, so provide the load values are reached, it will do so with the minimum amount of boost required.
K.
yajeed said:
That sounds promising (the octane rating comment).
A few people have mentioned common problems which result in under performance.
Would any if those apply to a very slight reduction in maximum boost, as I appear to be experiencing?
With cold weather it is normally to see less boost since load targets are hit earlier. In the summer you tend to see another 0.1 bar in order to hit the loads.A few people have mentioned common problems which result in under performance.
Would any if those apply to a very slight reduction in maximum boost, as I appear to be experiencing?
Running 95 will definitely dent the performance of a 996t. I know, I have done the tests. It affects the midrange timing quite a lot. So that is the first thing to do.
The only thing that concerns me is this noise you refer to when you say exhaust. The 996 t standard exhaust is quiet. So you either have
- non standard exhaust
- crack in one manifold - this definitely makes the exhaust louder, or gives that impression.
- boost leak and you are not used to the noise that a boost leak will give.
An OPC does not pressure test the car in any service. You would have to specifically ask for a pressure test to be done. So you cannot assume that everything is okay.
Start with proper fuel, then make sure adaption values are at their peak (drive hard for a while) and then pull from 2000 rpm in 4th - you should see 0.7 for sure. You use 4th because it gives the time for the peak load to be hit, showing max boost.
Ken
metsta said:
Glad you got one in the end mate and hope you get it sorted. My new car has been at JAZ the past 2 weeks so I'm getting ready for a wallet bashing too! The joys of Porsche ownership, get some pics up of your new car!
Thanks, will do once I've got it cleaned. It seems I've probably being worrying over nothing too - the car showed a sustained 0.7 when under load in 4th this morning.
As Ken says, but if the last person has been driving for an extended period with 95 ron fuel it may take quite a long time for the adaption values to recover.
There is a little cheat that the OPC wont tell you ( although if asked they will admit it) Turn on your ignition with the engine off ( stops the alarm going off) and disconnect your batter for a short period.....leave it 10 minutes then reconnect. This resets the adaption values to where it would have left the factory.
You will need to re-train your windows and throttle position. All easy stuff to do.
Once you have reset the adaption values you should notice a good difference. From that point run Shell 99 ron and the car will actually start to adapt even more and in a positive direction.
Remember adaption values go down very quickly but take a long time to get back to where they were. So if you put a top up of 95 back in the tank you could very well reduce you values again.
There is a little cheat that the OPC wont tell you ( although if asked they will admit it) Turn on your ignition with the engine off ( stops the alarm going off) and disconnect your batter for a short period.....leave it 10 minutes then reconnect. This resets the adaption values to where it would have left the factory.
You will need to re-train your windows and throttle position. All easy stuff to do.
Once you have reset the adaption values you should notice a good difference. From that point run Shell 99 ron and the car will actually start to adapt even more and in a positive direction.
Remember adaption values go down very quickly but take a long time to get back to where they were. So if you put a top up of 95 back in the tank you could very well reduce you values again.
Edited by Sunnysidebb on Tuesday 2nd April 15:24
Sunnysidebb said:
As Ken says, but if the last person has been driving for an extended period with 95 ron fuel it may take quite a long time for the adaption values to recover.
There is a little cheat that the OPC wont tell you ( although if asked they will admit it) Turn on your ignition with the engine off ( stops the alarm going off) and disconnect your batter for a short period.....leave it 10 minutes then reconnect. This resets the adaption values to where it would have left the factory.
You will need to re-train your windows and throttle position. All easy stuff to do.
Once you have reset the adaption values you should notice a good difference. From that point run Shell 99 ron and the car will actually start to adapt even more and in a positive direction.
Remember adaption values go down very quickly but take a long time to get back to where they were. So if you put a top up of 95 back in the tank you could very well reduce you values again.
Very interesting.There is a little cheat that the OPC wont tell you ( although if asked they will admit it) Turn on your ignition with the engine off ( stops the alarm going off) and disconnect your batter for a short period.....leave it 10 minutes then reconnect. This resets the adaption values to where it would have left the factory.
You will need to re-train your windows and throttle position. All easy stuff to do.
Once you have reset the adaption values you should notice a good difference. From that point run Shell 99 ron and the car will actually start to adapt even more and in a positive direction.
Remember adaption values go down very quickly but take a long time to get back to where they were. So if you put a top up of 95 back in the tank you could very well reduce you values again.
Edited by Sunnysidebb on Tuesday 2nd April 15:24
How would one go about re train the windows and throttle?
Thanks
Steviesam said:
Sunnysidebb said:
As Ken says, but if the last person has been driving for an extended period with 95 ron fuel it may take quite a long time for the adaption values to recover.
There is a little cheat that the OPC wont tell you ( although if asked they will admit it) Turn on your ignition with the engine off ( stops the alarm going off) and disconnect your batter for a short period.....leave it 10 minutes then reconnect. This resets the adaption values to where it would have left the factory.
You will need to re-train your windows and throttle position. All easy stuff to do.
Once you have reset the adaption values you should notice a good difference. From that point run Shell 99 ron and the car will actually start to adapt even more and in a positive direction.
Remember adaption values go down very quickly but take a long time to get back to where they were. So if you put a top up of 95 back in the tank you could very well reduce you values again.
Very interesting.There is a little cheat that the OPC wont tell you ( although if asked they will admit it) Turn on your ignition with the engine off ( stops the alarm going off) and disconnect your batter for a short period.....leave it 10 minutes then reconnect. This resets the adaption values to where it would have left the factory.
You will need to re-train your windows and throttle position. All easy stuff to do.
Once you have reset the adaption values you should notice a good difference. From that point run Shell 99 ron and the car will actually start to adapt even more and in a positive direction.
Remember adaption values go down very quickly but take a long time to get back to where they were. So if you put a top up of 95 back in the tank you could very well reduce you values again.
Edited by Sunnysidebb on Tuesday 2nd April 15:24
How would one go about re train the windows and throttle?
Thanks
ETA - this might help.
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