Shell Nitro thoughts
- Thread starter Dave928
- Start date
924nutter
PCGB Member
There are so many variables regarding inlet air temperature to make any meaningfull comparisons misleading unless outside air temp is taken into account. Warmer inlet air will exacerbate any tendency to pink. I dont know which would be worse for pinking, the 10.3: 1 of normally aspirateds or the forced induction engine. Knock sensors work by detecting the vibration that occurs before harmful pinking sets in and retarding the ignition slightly to a safe setting and way before any human sense can detect it and react. The higher the octane rating the more knock resistance it has, so in effect, run a 944 on 99 ron and the knock sensor will probably not be doing anything, even on a hot day. The lower grade of fuel you use the more the ignition will be retarded, resulting in a loss of power. Whether anyone would be abe to notice a change from 98 to 99, I don't know. If you do then you do and I am not suggesting a placebo effect. I stopped for fuel on the way home from the Bedford track day andf happened upon a garage selling Shell's latest offering and stuck a tank full in the 911 which had previously been filled up with BP Ultimate. Can't say I have had better economy or more grunt as I haven't used that tank up. Next year if I can pull 150 at the end of the straight instead of 147 then we can put the extra 3 mph down to Shell. Gonna be a long wait.
Ex Skyline
New member
If your car's have not been set up (tuned) for higher octane fuel's then, you're wasting your dosh. Simple as that.
944 man
Active member
Empirical evidence suggests that even later 944s which will or must run on unleaded fuel will run better and return better MPG figures using SUL.
It is true of course, that 944 DMEs do not have the ability to learn nor to advance (or retard) ignition advance, but there is still a tangiable benefit.
It is true of course, that 944 DMEs do not have the ability to learn nor to advance (or retard) ignition advance, but there is still a tangiable benefit.
. At the last RR the AFR seemed to be OK though 
Just reread my last post. Should have emphasised 1 - I used to use Sainsbuys 98 or 99 and 2 - I have been using Vpower for the past 3 years and the nitro made a very noticeable difference
Porsche made a corporate decision in approx 1981 to make all their cars run on standard unleaded.
Which meant that when the 944 was revised for the 1985 model year, the compression ratio was dropped slightly although the quoted power remained the same, (I suspect the ECU was changed slightly).
It was only the most sporting models that required Super after this, although the modern ECUs adapt for whatevers in the tank.
Which meant that when the 944 was revised for the 1985 model year, the compression ratio was dropped slightly although the quoted power remained the same, (I suspect the ECU was changed slightly).
It was only the most sporting models that required Super after this, although the modern ECUs adapt for whatevers in the tank.
924nutter
PCGB Member
Actually I can answer my own question having looked it up under How do Porsche Knock sensors work. I was directed to a Porsche Parts site where the people have kindly offered an explanation of how a knock sensor works. My basic concept is indeed correct, and infact a knock sensor is in effect a very sensitive microphone, sited in a suitable place on the engine, where it listens for the vibrations caused by pinking and sends a signal to the ecu to tell it pinking is occuring, the ECU is programmed to retard the ingnition, likely in two degree increments untill the vibrations cease. This allows the engines to be run at the very edge of performance without running the risk of piston holing and extends engine life. Come to think of it the Porcshe DME can advance and retard the igntion, it is just that it is programmed into the 3D map. The dme monitors several parameters, e.g. throttle position, load, engine rpm, boost if you have it, etc. The DME then picks the optimum ignition setting to suit these monitored conditions.
944 man
Active member
Off the top of my head John, the KLR ECU monitors det on the 944 and there is a sensor (two I think?) on the S & S2 which have a more advanced DME than the eight valve cars.
My point though, was that the ECUs arent able to learn in any respect, in the way that newer cars can. The dont retard until you reset them or test and advance.
My point though, was that the ECUs arent able to learn in any respect, in the way that newer cars can. The dont retard until you reset them or test and advance.
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