96 octane, 1/4 tank later...
10-01-2016, 08:20 PM
#31
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https://www.amazon.com/Royal-Purple-...octane+booster
torco good too
not surprised at pete's findings - was my first reaction taking delivery of my gt4(s)... whoa, this engine just doesn't pull like the other 3.8 9a1's i have driven... wtf
it is now known that aftermkt ecu tune on gt4 makes much bigger difference than other pag na cars as factory purposefully tamped this one down so much -- mr andy p can't let us have TOO much fun for $100k right????
torco good too
not surprised at pete's findings - was my first reaction taking delivery of my gt4(s)... whoa, this engine just doesn't pull like the other 3.8 9a1's i have driven... wtf
it is now known that aftermkt ecu tune on gt4 makes much bigger difference than other pag na cars as factory purposefully tamped this one down so much -- mr andy p can't let us have TOO much fun for $100k right????
10-01-2016, 09:37 PM
#32
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Originally Posted by stout
I don't know about you, but I've been a bit disappointed in my GT4's flat six since taking delivery.
The 3.8 in my car felt soft under 5000 rpm, with weird peaks and troughs down low and in the midrange, and then choppy delivery up top. Same for a press car, and same for another friend's car. Nor did any of them feel particularly fast. My butt dyno suggested less than 385 horses were on duty, though this was less frustrating than the on-again/off-again powerband. (And to think some folks complain about turbocharging—the 991-2s I tried on CA gas were just fine and WAY more linear through the power band. As were several 991-1s.)
It was enough to make me wonder how long I'd keep the car—or if I would have to mod the thing, warranty be damned.
I've been wondering if it was a CA fuel thing, because it felt like the ECU was pulling the timing back, but I only recently stopped by to get some 96-octane gas. The difference wasn't immediately apparent. A quarter-tank later, it's night and day. It's no longer soft in the low end and mid-range—the car feels like it has picked up BIG power down there, and feels faster up top, too. A lot faster. Now my car feels like the press cars in Portugal did. It feels like it has a different engine. If you'd told me it was a $1,500 reflash, I might be interested in plunking down, because it's smooth and predictable everywhere. Instead, it was ten gallons at $8/gallon instead of $3.50/gallon.
I'm going to run through this tank and see if it helps the ECU smooth things out even on 91, but I fear more $8 gas may be in my future.
YMMV...
The 3.8 in my car felt soft under 5000 rpm, with weird peaks and troughs down low and in the midrange, and then choppy delivery up top. Same for a press car, and same for another friend's car. Nor did any of them feel particularly fast. My butt dyno suggested less than 385 horses were on duty, though this was less frustrating than the on-again/off-again powerband. (And to think some folks complain about turbocharging—the 991-2s I tried on CA gas were just fine and WAY more linear through the power band. As were several 991-1s.)
It was enough to make me wonder how long I'd keep the car—or if I would have to mod the thing, warranty be damned.
I've been wondering if it was a CA fuel thing, because it felt like the ECU was pulling the timing back, but I only recently stopped by to get some 96-octane gas. The difference wasn't immediately apparent. A quarter-tank later, it's night and day. It's no longer soft in the low end and mid-range—the car feels like it has picked up BIG power down there, and feels faster up top, too. A lot faster. Now my car feels like the press cars in Portugal did. It feels like it has a different engine. If you'd told me it was a $1,500 reflash, I might be interested in plunking down, because it's smooth and predictable everywhere. Instead, it was ten gallons at $8/gallon instead of $3.50/gallon.
I'm going to run through this tank and see if it helps the ECU smooth things out even on 91, but I fear more $8 gas may be in my future.
YMMV...
10-02-2016, 12:49 AM
#33
Advanced
The A91 in the GT4 will run just fine on 100. Higher octane rating doesn't mean "trickier", it just means that the fuel spontaneously combusts at higher pressure (i.e. compression in the engine's cylinder.) AKI mean Anti-Knock Index, where "knocking" is premature combustion of gas in the cylinder (i.e. before the piston reaches its top extreme, meaning there's a lot less power being produces as it's clearly less efficient.)
Generally, the higher the compression ratio in an engine, the higher octane you'll need to extract optimum performance. I'm guessing that 100 AKI is going to yield the same results as 96 AKI in the GT4 since the compression ratio is not that high (unlike, say a 458 Speciale.)
Generally, the higher the compression ratio in an engine, the higher octane you'll need to extract optimum performance. I'm guessing that 100 AKI is going to yield the same results as 96 AKI in the GT4 since the compression ratio is not that high (unlike, say a 458 Speciale.)
10-02-2016, 12:53 AM
#34
We only have 91 here in CO, but at altitude pre detonation is not as big of an issue.. And until recently I had an ethanol free shell station I would go to. I have heard that in the winter the mix changes to more ethanol I think...
10-02-2016, 05:39 PM
#36
Three Wheelin'
10-02-2016, 06:08 PM
#37
Advanced
10-02-2016, 06:36 PM
#38
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From Porsche Service Information 2016 Technik Introduction, Cayman GT4, (#PNA CMN GT4 16), section 2.3.1 "Fuel supply, low-pressure side", © 2015 Porsche Cars North America, Inc.
Since this is published by Porsche North America, I'm making the assumption that octane numbers are in AKI (and not in RON.) So yeah, target 93-94 and we should theoretically get maximum performance and life-length from the stock engine.
The engine has been designed to provide optimum performance and fuel consumption
if premium unleaded fuel 93 octane is used. The engine is suitable for operation with fuel containing up to 10% ethanol. If unleaded fuels 90 octane are used, the engine’s knock control automatically adapts the ignition timing.
The use of fuels with octane numbers of less than 90 octane could reduce engine power and increase fuel consumption. The vehicle must not be driven at full throttle in this case.
if premium unleaded fuel 93 octane is used. The engine is suitable for operation with fuel containing up to 10% ethanol. If unleaded fuels 90 octane are used, the engine’s knock control automatically adapts the ignition timing.
The use of fuels with octane numbers of less than 90 octane could reduce engine power and increase fuel consumption. The vehicle must not be driven at full throttle in this case.
10-02-2016, 06:58 PM
#39
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Having lived on the East Coast and Midwest with easy access to 93 I can say that the difference between 91 and 93 is not significant as far as my but dyno is concerned and I haven't noticed any major change in the engines drivability. But I recently also filled a half tank with 95 octane (tank was empty) and I too noticed a difference after about 10 miles of driving. The difference was immediately evident in the lower and mid range RPM's with much improved throttle response and without question more power throughout the power band. I also noticed the engine ran smoother and the exhaust note was deeper/louder. The best description I can give it is the feeling you get after having a strong cup of coffee after a late night out, the cobwebs were lifted if you will.
At $8/Gallon it's not exactly affordable for the amount of driving I have been doing and not readily accessible since this place was about 40 minutes away but when I'm in that area again I will be refueling with it.
I know it's not apples to apples since you all are running the 3.8 but I do believe that many of the modern day Porsche's could benefit from higher octane gas.
No MSG's to boot!
At $8/Gallon it's not exactly affordable for the amount of driving I have been doing and not readily accessible since this place was about 40 minutes away but when I'm in that area again I will be refueling with it.
I know it's not apples to apples since you all are running the 3.8 but I do believe that many of the modern day Porsche's could benefit from higher octane gas.
No MSG's to boot!
Last edited by Marine Blue; 10-02-2016 at 08:10 PM.
10-02-2016, 07:27 PM
#40
Originally Posted by sunnyr
1 part 100 to 2 part 91 will put you at 94, which should be good (if 93 is what the car needs). AFAIK, nothing wrong in going higher besides cost.
10-03-2016, 08:25 AM
#41
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Good fuel definitely helps, although much more so if you tune for it to take full advantage. Perks of the Cobb Accessport is that you can have a custom maps made for any fuel you decide to run, and switch between the maps quite easily. We can also tune for race fuel for those that would like to run it.That being said, the majority of the GT4's performance flaws are concentrated in the restrictive hardware/software on the car. Even the best performing 93 octane GT4 we've had come through was about 50whp/60wtq down on it's true potential. Here is one of the graphs we have for reference, and some videos of the GT450s on track.
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Porsche Performance Specialist
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215-618-9796
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10-03-2016, 10:59 AM
#43
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The dynograph is from our full GT450 Package, the details of which can be found at the following link.
http://www.fabspeed.com/porsche-caym...mance-package/
To answer your question though, the GT450 Package is our Race Headers, Valvetronic Exhaust System, IPD Plenum/TB Package, BMC Filters, and Cobb Accessport with Protune.
http://www.fabspeed.com/porsche-caym...mance-package/
To answer your question though, the GT450 Package is our Race Headers, Valvetronic Exhaust System, IPD Plenum/TB Package, BMC Filters, and Cobb Accessport with Protune.
