When do your turbos spool?
07-28-2015, 11:17 AM
#31
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Thread Starter
Yep, the turbo inlet pipes, GT2 ICs, and exhaust are all you need to make a lot of power with Cobb on pump gas....enough to make your stock clutch slip, so get ready unless you dial it back some 
The turbo inlet pipes were the only hardware change at that time other than the injectors as far as performance goes. At the boost pressures I'm running, there was less taper at high rpm. They are worth it, the factory inlets are junk when it comes to flow.
There are a lot of custom tuners for the Cobb platform. I used ProTuning Freaks and was very happy with their service.
The turbo inlet pipes were the only hardware change at that time other than the injectors as far as performance goes. At the boost pressures I'm running, there was less taper at high rpm. They are worth it, the factory inlets are junk when it comes to flow.
There are a lot of custom tuners for the Cobb platform. I used ProTuning Freaks and was very happy with their service.
Great to hear that the tubes makes a difference down low. That will get me going on the project.
07-28-2015, 11:25 AM
#32
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Thread Starter
This sounds like a variation of something I've not been able to work out with this car. Unless you're on it, you're off boost. You can be completely off boost at 6000rpm if you're just running at some constant speed.
IMHO the folks that claim that there's no noticeable lag are simply not particularly perceptive, or at least insufficiently impatient.
I really don't understand how I would go about getting a really top lap time in a car like this. I suspect I'd just need to anticipate corner exits and get into the throttle a bit early. This is very different from non variable vane turbos where you'd just make sure to be above some engine speed at all times when you want to be ready to go.
IMHO the folks that claim that there's no noticeable lag are simply not particularly perceptive, or at least insufficiently impatient.
I really don't understand how I would go about getting a really top lap time in a car like this. I suspect I'd just need to anticipate corner exits and get into the throttle a bit early. This is very different from non variable vane turbos where you'd just make sure to be above some engine speed at all times when you want to be ready to go.
EXACTLY !!!
In my last car I had a turbo that was 50% larger than stock (53 lb a min v.s. 36 lb a min),.. and at 3,000 rpm just putting down the freeway the turbo was 1/2 spun up. I could hear it,.. and the slightest tip in our out of the throttle would cause the turbo so spin up or down. Even with imperceptible touches of the throttle I could hear that glorious whistle. Mat the loud pedal and 10 psi of boost was on the gauge within 1/2 second,.... 22 psi in less than 1 sec..
With the Porsche,.. the turbos seem to be sleeping on the freeway,.. even above 4,000 rpm. Tip into the gas fairly hard and you still wait a bit. You'd think the turbos were good for 800 hp with the way they spool up. Perhaps they need a slightly smaller hot-side?
It makes you wonder what the benefit of the VTG is if they perform less well than an off the shelf Garrett.
07-28-2015, 01:12 PM
#33
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EXACTLY !!!
In my last car I had a turbo that was 50% larger than stock (53 lb a min v.s. 36 lb a min),.. and at 3,000 rpm just putting down the freeway the turbo was 1/2 spun up. I could hear it,.. and the slightest tip in our out of the throttle would cause the turbo so spin up or down. Even with imperceptible touches of the throttle I could hear that glorious whistle. Mat the loud pedal and 10 psi of boost was on the gauge within 1/2 second,.... 22 psi in less than 1 sec..
With the Porsche,.. the turbos seem to be sleeping on the freeway,.. even above 4,000 rpm. Tip into the gas fairly hard and you still wait a bit. You'd think the turbos were good for 800 hp with the way they spool up. Perhaps they need a slightly smaller hot-side?
It makes you wonder what the benefit of the VTG is if they perform less well than an off the shelf Garrett.
The larger (than necessary) turbo sizing (combined with relatively low CR) means the power doesn't fade away in 35 degree C summer heat on the A8 from Stuttgart to Munich..... It will be interesting to see if this historic strategy is carried forward into the new turbo Carrera 991s, I suspect it wont
07-29-2015, 04:11 AM
#34
It will be interesting to see if this historic strategy is carried forward into the new turbo Carrera 991s, I suspect it wont
I have some memories of trying to go fast on the A3 with a Renault turbo that would loose power after you went all out for a while. With each trip we got better at planning ahead so we'd have power in the spots where there was enough visibility.
Being able to blow away budget setups like this, repeatably, is part of the DNA of a proper german car.
08-27-2015, 11:04 AM
#35
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I hate to say it,.. but I was a bit disappointed when I bought my 07 Turbo with the width of the power-band.
The turbos come on at 3,500,.. and redline is a measly 6,500.
I finally found a spec on the redline,.. and Porsche claims it is actually 6,750 (perhaps the tach needle is just tardy?).
My car came to me with cat-less Tubi exhaust,which should help the spool threshold a bit
The Cobb Accesport flash I have on it now raises the redline to what seems like to 6,900,.. but that still makes for a fairly narrow power-band. Having come from Subarus where the turbo is in by 3,00 or so,.. and the redline is 7,200 - 7,500,.... I find that it's some concentrated effort on my part to keep this car on the boil. And getting it out of the hole without smoking the clutch is a real trick.
THEN I read a Car & Driver review from back in 2006 or 2007 where they talk about no turbo lag from about 2,000 rpm and up. WHAAAA??? Is something wrong with my car?
Any of you have boost by 2,000 rpm?
I have a set of Do88 turbo inlet tubes in a box that I could try.
So where does everyone's turbos come on? And what do you see for redline?
The turbos come on at 3,500,.. and redline is a measly 6,500.
I finally found a spec on the redline,.. and Porsche claims it is actually 6,750 (perhaps the tach needle is just tardy?).
My car came to me with cat-less Tubi exhaust,which should help the spool threshold a bit
The Cobb Accesport flash I have on it now raises the redline to what seems like to 6,900,.. but that still makes for a fairly narrow power-band. Having come from Subarus where the turbo is in by 3,00 or so,.. and the redline is 7,200 - 7,500,.... I find that it's some concentrated effort on my part to keep this car on the boil. And getting it out of the hole without smoking the clutch is a real trick.
THEN I read a Car & Driver review from back in 2006 or 2007 where they talk about no turbo lag from about 2,000 rpm and up. WHAAAA??? Is something wrong with my car?
Any of you have boost by 2,000 rpm?
I have a set of Do88 turbo inlet tubes in a box that I could try.
So where does everyone's turbos come on? And what do you see for redline?
We've protuned quite a few 997.1 turbos over the past year or more on top of the Cobb Accessport platform with great results. A few things we improve in the tune other than power and torque are response and time to boost (reducing lag). Do88 inlet pipes are a great upgrade over the OEM 997.1 Turbo inlet pipes and we recommend them highly to all the guys we're working on tuning with.
Let me know if there are any other questions at all. If you've got any logs off your Cobb AP feel free to shoot them over to me at dzenno@protuningfreaks.com and I'd be happy to review them for you and provide feedback on how the car is running overall.
Dzenno@PTF
08-27-2015, 04:03 PM
#36
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Thread Starter
Hi Duckstu,
We've protuned quite a few 997.1 turbos over the past year or more on top of the Cobb Accessport platform with great results. A few things we improve in the tune other than power and torque are response and time to boost (reducing lag). Do88 inlet pipes are a great upgrade over the OEM 997.1 Turbo inlet pipes and we recommend them highly to all the guys we're working on tuning with.
Let me know if there are any other questions at all. If you've got any logs off your Cobb AP feel free to shoot them over to me at dzenno@protuningfreaks.com and I'd be happy to review them for you and provide feedback on how the car is running overall.
Dzenno@PTF
We've protuned quite a few 997.1 turbos over the past year or more on top of the Cobb Accessport platform with great results. A few things we improve in the tune other than power and torque are response and time to boost (reducing lag). Do88 inlet pipes are a great upgrade over the OEM 997.1 Turbo inlet pipes and we recommend them highly to all the guys we're working on tuning with.
Let me know if there are any other questions at all. If you've got any logs off your Cobb AP feel free to shoot them over to me at dzenno@protuningfreaks.com and I'd be happy to review them for you and provide feedback on how the car is running overall.
Dzenno@PTF
I presumed there were a lot of tricks for improving the spool threshold. We used to do a number of things in the Subaru world,.. such as leaving the intake cam phase fully advanced until the boost pressure started to come up. We would also lean-spool the turbo (leaving the AFR a point or so leaner than the target AFR until such point as the manifold pressure got 1/3 of the way to the boost target. (Lean mix burns hotter,.. which means the exhaust gas is expanded more,.. which means increased exhaust velocity at the turbine volute.)
I'd like to employ all the tricks we can without hurting anything,... and also dial back that over-boost lump between 3,500 and 4,100 when Sport Mode is engaged.
So that the resulting boost pressure would look as bit like the little yellow line that I drew on A4188T81's graph below.
08-27-2015, 04:20 PM
#37
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Yes, as a matter of fact we use cam timing quite a bit on a number of platforms to help spool. On the BMW N54 direct injection platform we literally over the last two days found a way to get a 6266 turbo to spool up on this 3L motor 800rpm faster to 22psi. That's with a 1.0 AR housing in a twin-scroll setup compared to other flash tuning that's out there currently 800rpm is A LOT! In 3rd gear 22psi used to be at 4300rpm and now at 3500rpm, like a different car with a lot more power under the curve and way more fun to drive on the street.
Lean-spooling doesn't always work or not nearly as well as maxing out cam timing. On some motors we can adjust both the exhaust and the intake cams to the point of causing compressor surge even with the smallest of turbine/compressor setups With the 997.1 factory ECU there's some spool to be gained through boost control and vane regulation/duty cycle but unfortunatley not as much with the intake cam.
A4188T81 is one of the guys whose 997.1 I've worked on tuning and we've done quite a bit there, enough to grab some currently standing VTG platform records
Dzenno@PTF
800rpm is A LOT! In 3rd gear 22psi used to be at 4300rpm and now at 3500rpm, like a different car with a lot more power under the curve and way more fun to drive on the street.Lean-spooling doesn't always work or not nearly as well as maxing out cam timing. On some motors we can adjust both the exhaust and the intake cams to the point of causing compressor surge even with the smallest of turbine/compressor setups
With the 997.1 factory ECU there's some spool to be gained through boost control and vane regulation/duty cycle but unfortunatley not as much with the intake cam.A4188T81 is one of the guys whose 997.1 I've worked on tuning and we've done quite a bit there, enough to grab some currently standing VTG platform records
Dzenno@PTF