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So the Gt2RS now has now new intercoolers, BRV, a couple of hoses and new clamps replaced under warranty and did some new runs, 400 USD in speed fines later, got new durametric logs. Boost is picking up faster, but still deceiving performance when compared to magazine stuff..
So I have to think that a mix of warm temps (30C ambient) and crappy fuel as TTurbine well pointed out are limiting my max. power to 578HP vs. factory published 620HP, with a maximum registered of 582HP at 6600RPM on another run. Maximum boost is reached in the high 5K RPMS. I could do better by starting with some boost, but this is literally slamming the throttle starting at 0 boost. What is also obvious is that even very accurate well loaded engine dynos are optimistic when it comes to real life timing of torque delivery.
Here are some more logs that can stay here as reference to others of what stock Porsche tuning looks like on an RS.
Interesting app BTW WHiteknight
Jean, very interesting stuff, thanks very much for sharing the data. Do you or anyone else know a way of determining how much horsepower is lost with different types of fuel (various octanes or other factors)? I'm in CA so 1) the highest octane one can readily pump is 91 and 2) temperatures are often 80 degree + (26-27 degrees to you) so if your horsepower is in the 585 range then I can only imagine how bad that would be out here.
TB, can I assume that Mr. RS tuned the car for you based on gas that you will most often use? How well does the car adapt to different fuels? Thanks very much in advance guys. Cheers.
TB, can I assume that Mr. RS tuned the car for you based on gas that you will most often use? How well does the car adapt to different fuels? Thanks very much in advance guys. Cheers.
I am told the 997 ECU set up is VERY sensitive to fuel quality and RS did engine dyno tests with different fuels and lower octanes lost power, I can't remember the figures but 50hp is in my head....
RS use 98RON for all engine dyno tuning and testing but recommend the German Shell loopy juice V Power Racing which is 102 RON !!.
I use our UK Shell V Power which is rated at 99 RON, I once had to use another brand (claimed 97 RON) for a tank at an airstrip even and am pretty sure it made me go slower.... all anecdotal I'm afraid
Do you or anyone else know a way of determining how much horsepower is lost with different types of fuel (various octanes or other factors)?
Enduro911,
It is impossible to have exact numbers as it depends on several parameters, however from some data I gathered, a 3-5 octane increase will improve your BMEP by up to 2 bar on a turbocharged engine. Maximum torque and BMEP are directly related. An excerpt from an SAE paper on effect of fuel on torque..
"An important influence of RON at iso sensitivity was observed. Because of the extreme conditions met on turbocharged gasoline engine, the impact of RON is exacerbated on such engine and illustrates the great benefits of an increase RON fuel"
As an example, a 997TT has a BMEP of ~254 non-adjusted for boost and maximum torque of 457lbs/ft. A BMEP decrease of 2 bar from a 5 octane decrease takes your BMEP to 225. Maximum theoretical torque is therefore decreased from 457 to 404 lbs.ft. That's a decrease of torque of ~13%.
This seems pretty much in line with the following research below:
The 50HP that TB993TT mentioned is not too far off.
So 12 Years after I started this thread and 70K odd miles later I sent my GT2 back to my engine builders in Germany for a refresh, 8 years of UK salty winters had taken a toll on the exhaust and turbos so all new parts were installed, the engine was checked and everything was in the green, a new high flowing DO88 Y pipe was dialled in on the engine dyno, various issues involving fuel pumps and the need for dry quiet conditions for 200mph Autobahn testing meant the car took an extended holiday.
I finally picked up and with 850PS/944NM had a fairly eye opening drive home using as many derestricted Autobahns as I could find, the car is super responsive and about as accelerative as is safe for road use it almost pulls a wheelie in third gear under full torque what a memorable journey, pic for attention, the Germans have the advantage of some tasty fuel 102 RON and charge as much as 2.64 Euro a litre but the motor certainly seemed to like it.
05-05-2016, 11:00 PM
