96 octane, 1/4 tank later...
Burning Brakes
Joined: Sep 2008
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From: Northeast
Pete really needs to drive a car with the intake and exhaust mods, a tune, and some decent gas. They truly transform the car. But it may end up being less about breathing than it is the stock ECU holding the car back. As I said earlier in this thread, the guys that custom tuned my car mentioned how sensitive the ECU was compared to other Porsches they've worked on.
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From: ^ The Bay Bridge
There's little question the car would benefit from a TB, headers, and retune. Time in the Sharkwerks GT4 with headers and a retune plus LWF and different gears confirmed as much, and I'd consider making 2-3 of those upgrades outside of warranty. The car was certainly more awake and alert, though not yet in possession of an engine to match its chassis—or bigger GT brothers.
Question for me is whether a new car sold in CA should be so clearly and negatively impacted by CA fuel. I can't think of another factory Porsche I've tested that is so obviously unable to deal with 91.
Question for me is whether a new car sold in CA should be so clearly and negatively impacted by CA fuel. I can't think of another factory Porsche I've tested that is so obviously unable to deal with 91.
Burning Brakes
Joined: Mar 2016
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From: 33.6189° N, 117.9289° W
This one is just down the street from me...Graham's Newport Hills Union 76, 2690 San Miguel Rd., Newport Beach CA.
I was always under the impression that racing fuel is pointless in a street car unless it's been tuned specifically for it. Doesn't the ECU adjust for the fuel?
I was always under the impression that racing fuel is pointless in a street car unless it's been tuned specifically for it. Doesn't the ECU adjust for the fuel?
Race Director
Joined: Apr 2010
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From: Ny
IMO,the difference between 91 and 93 is insignificant. The owner's manual of any Porsche,Turbo included,states that you can even use regular fuel in case of emergency. The computer will just pull timing and the car will be slower,but no damage will occur.
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From: ^ The Bay Bridge
The problem here isn't using the odd tank of 87 or 89 with no damage. The problem is reduced performance and sub-par driveability on the premium fuel we get in CA, one of Porsche's largest markets. No Porsche that I have driven in Europe or other NA locations has felt so clearly compromised on CA 91. My GT4 seems to have a noticeably different (and far less enjoyable) powerband on 91 than it does on a mix of 91/96 (which is a pain to get). The same goes for a friend's GT4, and for the red PCNA GT4 press car. The 3.4-liter Cayman GTS we tested for Panorama at the same time on the same 91 pump gas from 3-4 gas stations pulled evenly from 3000 rpm to redline every time, with none of the valleys and soft spots under 5000 rpm. That 3.4 was arguably more enjoyable than the 3.8 in use—and didn't much (if any) slower over the same roads.
Main point of this thread is to confirm my perceptions, and see if others are noticing the same in CA—particularly if they've owned or spent time in a 991-1 Carrera S. I'm beginning to wonder if Porsche spent the time it needed to on the GT4's ECU mapping for CA gas. The car was developed very quickly, and I am trying to remember if I saw spy shots of GT4s on CA roads? I recall that some 981 Spyder prototypes did come through...
Burning Brakes
Joined: Sep 2008
Posts: 910
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From: Northeast
Indeed, neanicu. The difference between 91 and 93 hasn't been pronounced in other Porsches I've driven. But it sure is in the GT4.
The problem here isn't using the odd tank of 87 or 89 with no damage. The problem is reduced performance and sub-par driveability on the premium fuel we get in CA, one of Porsche's largest markets. No Porsche that I have driven in Europe or other NA locations has felt so clearly compromised on CA 91. My GT4 seems to have a noticeably different (and far less enjoyable) powerband on 91 than it does on a mix of 91/96 (which is a pain to get). The same goes for a friend's GT4, and for the red PCNA GT4 press car. The 3.4-liter Cayman GTS we tested for Panorama at the same time on the same 91 pump gas from 3-4 gas stations pulled evenly from 3000 rpm to redline every time, with none of the valleys and soft spots under 5000 rpm. That 3.4 was arguably more enjoyable than the 3.8 in use—and didn't much (if any) slower over the same roads.
Main point of this thread is to confirm my perceptions, and see if others are noticing the same in CA—particularly if they've owned or spent time in a 991-1 Carrera S. I'm beginning to wonder if Porsche spent the time it needed to on the GT4's ECU mapping for CA gas. The car was developed very quickly, and I am trying to remember if I saw spy shots of GT4s on CA roads? I recall that some 981 Spyder prototypes did come through...
The problem here isn't using the odd tank of 87 or 89 with no damage. The problem is reduced performance and sub-par driveability on the premium fuel we get in CA, one of Porsche's largest markets. No Porsche that I have driven in Europe or other NA locations has felt so clearly compromised on CA 91. My GT4 seems to have a noticeably different (and far less enjoyable) powerband on 91 than it does on a mix of 91/96 (which is a pain to get). The same goes for a friend's GT4, and for the red PCNA GT4 press car. The 3.4-liter Cayman GTS we tested for Panorama at the same time on the same 91 pump gas from 3-4 gas stations pulled evenly from 3000 rpm to redline every time, with none of the valleys and soft spots under 5000 rpm. That 3.4 was arguably more enjoyable than the 3.8 in use—and didn't much (if any) slower over the same roads.
Main point of this thread is to confirm my perceptions, and see if others are noticing the same in CA—particularly if they've owned or spent time in a 991-1 Carrera S. I'm beginning to wonder if Porsche spent the time it needed to on the GT4's ECU mapping for CA gas. The car was developed very quickly, and I am trying to remember if I saw spy shots of GT4s on CA roads? I recall that some 981 Spyder prototypes did come through...
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From: ^ The Bay Bridge
Pete, do you have a relationship with a tuner who would be willing to put your car on a dyno to see how the parameters could be changed to improve performance with 91 octane fuel and without any other mods? It might be a good way to see what PAG left on the table solely in the software. And it would help confirm your theory.
Hardest thing about this is finding the time in the next month or so. Not a high priority, but I am curious.
Race Director
Joined: Sep 2006
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From: Bentonville, AR
My 006 Turbo lives on 91 fuel here in CA but on a road trip a few years ago I got to try 93 and the difference was quite dramatic.
And one can't or shouldn't run "regular" in place of the minimum octane of IIRC 90. While the DME can retard timing among other negatives this raises exhaust gas temperature which can harm valves, sensors, even converters.
There is the question of if the DME can even pull timing enough, that Porsche has some limit either an arbitrary limit or one that is because any more timing pull is useless.
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From: ^ The Bay Bridge
Uh, no.
My 006 Turbo lives on 91 fuel here in CA but on a road trip a few years ago I got to try 93 and the difference was quite dramatic.
And one can't or shouldn't run "regular" in place of the minimum octane of IIRC 90. While the DME can retard timing among other negatives this raises exhaust gas temperature which can harm valves, sensors, even converters.
There is the question of if the DME can even pull timing enough, that Porsche has some limit either an arbitrary limit or one that is because any more timing pull is useless.
My 006 Turbo lives on 91 fuel here in CA but on a road trip a few years ago I got to try 93 and the difference was quite dramatic.
And one can't or shouldn't run "regular" in place of the minimum octane of IIRC 90. While the DME can retard timing among other negatives this raises exhaust gas temperature which can harm valves, sensors, even converters.
There is the question of if the DME can even pull timing enough, that Porsche has some limit either an arbitrary limit or one that is because any more timing pull is useless.
On NA engines, a couple of points shouldn't make the kind of difference I'm experiencing, or at least perceiving.
Race Director
Joined: Apr 2010
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From: Ny
Originally Posted by Macster
Uh, no.
My 006 Turbo lives on 91 fuel here in CA but on a road trip a few years ago I got to try 93 and the difference was quite dramatic.
And one can't or shouldn't run "regular" in place of the minimum octane of IIRC 90. While the DME can retard timing among other negatives this raises exhaust gas temperature which can harm valves, sensors, even converters.
There is the question of if the DME can even pull timing enough, that Porsche has some limit either an arbitrary limit or one that is because any more timing pull is useless.
My 006 Turbo lives on 91 fuel here in CA but on a road trip a few years ago I got to try 93 and the difference was quite dramatic.
And one can't or shouldn't run "regular" in place of the minimum octane of IIRC 90. While the DME can retard timing among other negatives this raises exhaust gas temperature which can harm valves, sensors, even converters.
There is the question of if the DME can even pull timing enough, that Porsche has some limit either an arbitrary limit or one that is because any more timing pull is useless.
I remain to the conclusion the difference between 91 and 93 is not " dramatic ". But perhaps the car can benefit from a different tune...
As a matter of fact,I might just try this experiment : I know how my car runs on 93 and perhaps next time I'll put what we call on the East Coast " mid-grade ",which is 91. I can then report.
Three Wheelin'
Joined: Oct 2003
Posts: 1,489
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I used to race a 996tt, and the system does adjust for octane within a
range, by adjusting timing and boost *with a corresponding change in
power output*. I did have separate maps for a wider range, with one
in the street 87-94 range, and another centered around 100-octane,
which gave my car a huge boost in power, and allowed me to run 1.4-1.5
bar boost.
When the Cayenne turbos came out, the local Porsche salesfolks were
going to the trouble of getting 100-octane unleaded in cans, or from a
15-mile-away local manufacturer, to ensure their demo Cayenne turbos
turned the test-drive volume to eleven. Seat-of-the-pants difference.
range, by adjusting timing and boost *with a corresponding change in
power output*. I did have separate maps for a wider range, with one
in the street 87-94 range, and another centered around 100-octane,
which gave my car a huge boost in power, and allowed me to run 1.4-1.5
bar boost.
When the Cayenne turbos came out, the local Porsche salesfolks were
going to the trouble of getting 100-octane unleaded in cans, or from a
15-mile-away local manufacturer, to ensure their demo Cayenne turbos
turned the test-drive volume to eleven. Seat-of-the-pants difference.
Race Director
Joined: Sep 2006
Posts: 19,035
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From: Bentonville, AR
Modern turbo cars can really put higher octane fuel to good use. My old WRX sure could...the added drivability alone made the trip to Sears Point for gas well worth it.
On NA engines, a couple of points shouldn't make the kind of difference I'm experiencing, or at least perceiving.
On NA engines, a couple of points shouldn't make the kind of difference I'm experiencing, or at least perceiving.
My info is Porsche runs its gasoline engines: Turbo as well as N/A engines; at very close to detonation. Getting that spark triggered as early as it can be really makes a difference in deriving the most from the energy produced by the fuel combustion.
Just a few points less octane which has the DME retarding the timing can make a big difference.
It is unlikely you will find Porsche left anything on the table regarding getting the most out of the engine when fed 91 octane gasoline. It is to Porsche's benefit to this not being the case. Really the DME stays just shy of detonation and this is regardless whether one is running 93 or 91 octane fuel.
What you are experiencing is the result of feeding a high compression engine gasoline with less than 93 octane.
Based on what has been posted it appears that the proper grade of octane is a particularly critical ingredient in the case of the GT4 and using 91 -- which is unfortunately all that is (readily) available in CA -- is going to result in some of the GT4's performance going missing.
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From: SF Bay Area, CA
It's on my mind. Actually have friends with a dyno, and am thinking about finding a way to dyno the car on a low tank on 91 after driving the car up there, and then adding a mix of 91/100 approximating 93, driving the car for 20 miles, and strapping it back onto the dyno.
Hardest thing about this is finding the time in the next month or so. Not a high priority, but I am curious.
Hardest thing about this is finding the time in the next month or so. Not a high priority, but I am curious.
Banned
Joined: Feb 2011
Posts: 4,078
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From: colorado canyons
Sunoco Race Fuel Finder, I have been using it for the 993 in Colorado at times....maybe I need to put some in the Spyder to see if there is a difference.
http://www.sunocoracefuels.com
http://www.sunocoracefuels.com
