Discussion
I'm sure you've been through this before but I'm new here! I'ts quite a distance to the nearest Shell station for V-Power so I've been using BP Utimate, its ok but was wondering firstly what Tesco's 99 is like, anyone got any comments on this? And secondly if god forbid I have to put inferior fuel in is there an additive that anyone can recommend? Cheers.
I run mine on 95 the manual says its best on 98, but I get hardly any/no knock (logged hours of driving)
The vxr8 307kw seems to run about 2deg more timing than the 297KW LS2 in the monaro (In fact that may be the main power difference, Piers is doing some testing on this)
Im sure your manual will say the same. (ie) No point running more than 98 max anyway. Try a tank of 95 and 98 and see what it feels like.
Apparenly mileage is best on 98. But the price difference probably wipes any advantage of that off.
The vxr8 307kw seems to run about 2deg more timing than the 297KW LS2 in the monaro (In fact that may be the main power difference, Piers is doing some testing on this)
Im sure your manual will say the same. (ie) No point running more than 98 max anyway. Try a tank of 95 and 98 and see what it feels like.
Apparenly mileage is best on 98. But the price difference probably wipes any advantage of that off.
More info on octane use here.
"Octane
High octane means slow burn, and you should always run the minimum octane level you can get away with. Octane is simply a fuel's resistance to detonation, and a higher-octane fuel must be com-pressed more to burn at the same rate as a lower-octane fuel. Likewise, a faster-burning fuel always makes more power up top. "An engine is tuned to fuel, not the other way around," says Darin. "If you pick up power on race gas, it means your engine combo is more suited to that fuel. Sometimes you can find that magic fuel that burns better for your combination, but it's not one size fits all. When they changed our fuel in Pro Stock, everything about our motors--including combustion chamber design, compression ratio, and cam specs--had to be changed."
http://www.chevyhiperformance.com/tech/engines_dri...
"Octane
High octane means slow burn, and you should always run the minimum octane level you can get away with. Octane is simply a fuel's resistance to detonation, and a higher-octane fuel must be com-pressed more to burn at the same rate as a lower-octane fuel. Likewise, a faster-burning fuel always makes more power up top. "An engine is tuned to fuel, not the other way around," says Darin. "If you pick up power on race gas, it means your engine combo is more suited to that fuel. Sometimes you can find that magic fuel that burns better for your combination, but it's not one size fits all. When they changed our fuel in Pro Stock, everything about our motors--including combustion chamber design, compression ratio, and cam specs--had to be changed."
http://www.chevyhiperformance.com/tech/engines_dri...
ringram said:
I run mine on 95 the manual says its best on 98, but I get hardly any/no knock (logged hours of driving)
The vxr8 307kw seems to run about 2deg more timing than the 297KW LS2 in the monaro (In fact that may be the main power difference, Piers is doing some testing on this)
Aiming to flash the timing map and log some runs tomorrow, will report back.The vxr8 307kw seems to run about 2deg more timing than the 297KW LS2 in the monaro (In fact that may be the main power difference, Piers is doing some testing on this)
If the engine has a knock sensor then it'll be able to retard the ignition timing to cope with crap fuel.
To be honest the RON value of fuel is meaningless - this is a percentage value rating based on low rpm and low engine loads. Generally used when trundling on a constant throttle down the motorway for example.
All fuels are rated with another value called MON - this is more useful to the enthusiastic driver or tuner. It's the same scale but a % value rating of the fuel in high rpm / high load conditions. In all cases (as far as I know) it's lower than the Ron value by usually about 10 points (it varies).
A good way to find the best fuel is to adopt the US approach of looking at the average of the RON and MON values (this is why fuel in the US always appears to be really cheap crap when actually it's no different). Optimax is still technically the best even beating some of the "100" ron fuels.
Just as an aside, there's no difference between UK optimax 98/V-Power99 as that in europe. The only difference is that the average elevation is alot higher and the detonation resistance of fuel increases with altitude.
Different octane fuels do not contain any more or less energy or burn quicker / slower. They may have different properties due to the varying refinement processes or benefit from other various additives that prevent carbon build up for example. The maximum amount of energy you can obtain for a given fuel is usually achieved just before pressure builds to a point where autoignition occurs - This is why detonation resistant fuels allow more performance.
The reason almost all manufacturers recommend super unleaded is simply marketing. When releasing stats for engines they (quite sensibly) use the best available fuel in the target market. Then the stats are based on that fuel and engine timing. This is why in the manual it says that using a lower grade will not cause any engine problems but may reduce maximum engine output.
I had a track engine built (without a knock sensor) to run on 100 ron fuel - the one and only time I had to fill up with bog standard 95 didn't cause any issues (it was either that or call the AA). When the engine was rebuilt not long after there were no signs of detonation (fortunately).
In general fuel in the UK is supplied pretty much from the same small group of refineries and unless a particular station has water in the tanks (which I have heard cases of) fuel is of a good quality.
To be honest the RON value of fuel is meaningless - this is a percentage value rating based on low rpm and low engine loads. Generally used when trundling on a constant throttle down the motorway for example.
All fuels are rated with another value called MON - this is more useful to the enthusiastic driver or tuner. It's the same scale but a % value rating of the fuel in high rpm / high load conditions. In all cases (as far as I know) it's lower than the Ron value by usually about 10 points (it varies).
A good way to find the best fuel is to adopt the US approach of looking at the average of the RON and MON values (this is why fuel in the US always appears to be really cheap crap when actually it's no different). Optimax is still technically the best even beating some of the "100" ron fuels.
Just as an aside, there's no difference between UK optimax 98/V-Power99 as that in europe. The only difference is that the average elevation is alot higher and the detonation resistance of fuel increases with altitude.
Different octane fuels do not contain any more or less energy or burn quicker / slower. They may have different properties due to the varying refinement processes or benefit from other various additives that prevent carbon build up for example. The maximum amount of energy you can obtain for a given fuel is usually achieved just before pressure builds to a point where autoignition occurs - This is why detonation resistant fuels allow more performance.
The reason almost all manufacturers recommend super unleaded is simply marketing. When releasing stats for engines they (quite sensibly) use the best available fuel in the target market. Then the stats are based on that fuel and engine timing. This is why in the manual it says that using a lower grade will not cause any engine problems but may reduce maximum engine output.
I had a track engine built (without a knock sensor) to run on 100 ron fuel - the one and only time I had to fill up with bog standard 95 didn't cause any issues (it was either that or call the AA). When the engine was rebuilt not long after there were no signs of detonation (fortunately).
In general fuel in the UK is supplied pretty much from the same small group of refineries and unless a particular station has water in the tanks (which I have heard cases of) fuel is of a good quality.
Mine's a bog standard 6.0VXR. Notwithstanding comments made on here previously, I maintain that, according to the seat of my pants, it runs SIGNIFICANTLY better on Tesco 99 RON.
I was running it on standard 95, and the performance was sufficiently reduced that I was intending to put it on a dyno to see if anything was wrong. First tank of 99 = no need for the dyno. OK, it's not scientific, but I'm convinced, and only run it on 99 now unless I run short and there's none nearby.
As a postscript to the above, I have always been cynical in the past about claims of better performance with, for example, VMax/Optimax, but I'm now a convert to the Tesco stuff.
I was running it on standard 95, and the performance was sufficiently reduced that I was intending to put it on a dyno to see if anything was wrong. First tank of 99 = no need for the dyno. OK, it's not scientific, but I'm convinced, and only run it on 99 now unless I run short and there's none nearby.
As a postscript to the above, I have always been cynical in the past about claims of better performance with, for example, VMax/Optimax, but I'm now a convert to the Tesco stuff.
C8PPO said:
Mine's a bog standard 6.0VXR. Notwithstanding comments made on here previously, I maintain that, according to the seat of my pants, it runs SIGNIFICANTLY better on Tesco 99 RON.
I was running it on standard 95, and the performance was sufficiently reduced that I was intending to put it on a dyno to see if anything was wrong. First tank of 99 = no need for the dyno. OK, it's not scientific, but I'm convinced, and only run it on 99 now unless I run short and there's none nearby.
As a postscript to the above, I have always been cynical in the past about claims of better performance with, for example, VMax/Optimax, but I'm now a convert to the Tesco stuff.
I was running it on standard 95, and the performance was sufficiently reduced that I was intending to put it on a dyno to see if anything was wrong. First tank of 99 = no need for the dyno. OK, it's not scientific, but I'm convinced, and only run it on 99 now unless I run short and there's none nearby.
As a postscript to the above, I have always been cynical in the past about claims of better performance with, for example, VMax/Optimax, but I'm now a convert to the Tesco stuff.
My pants have never noticed any difference so I stick to 95 ron.
What I would be interested to see is a dyno run on 95 and then 99 on a standard Ro.... Any Dyno owners up for it?!
PS i would gladly donate my vehicle as test vehicle for this purpose.....
C8PPO said:
Mine's a bog standard 6.0VXR. Notwithstanding comments made on here previously, I maintain that, according to the seat of my pants, it runs SIGNIFICANTLY better on Tesco 99 RON.
I was running it on standard 95, and the performance was sufficiently reduced that I was intending to put it on a dyno to see if anything was wrong. First tank of 99 = no need for the dyno. OK, it's not scientific, but I'm convinced, and only run it on 99 now unless I run short and there's none nearby.
As a postscript to the above, I have always been cynical in the past about claims of better performance with, for example, VMax/Optimax, but I'm now a convert to the Tesco stuff.
Ive tried both on my SC VXR and the 99 makes a difference. Tried Optimax and didnt notice anything really... Generally I will fill up with whatever is the best they have but if short 95 will do and I only part fill.I was running it on standard 95, and the performance was sufficiently reduced that I was intending to put it on a dyno to see if anything was wrong. First tank of 99 = no need for the dyno. OK, it's not scientific, but I'm convinced, and only run it on 99 now unless I run short and there's none nearby.
As a postscript to the above, I have always been cynical in the past about claims of better performance with, for example, VMax/Optimax, but I'm now a convert to the Tesco stuff.
My engine was a 1.8 K series and once it it was built it was initially dyno'd on 95 ron fuel before final tuning to 100ron. The peak difference was circa 8% with most of the benefit at higher rpm.
However this needs to be viewed with the caveat that the tunning was done completely manually on a bench with a lot of time and effort. Production cars have very well defined parameter ranges/limits for altering the ignition advance and are not going to be as accurate as a specific one off tuning.
I'd be incredibly surprised if anybody notices a car run on 95 or 98 fuel. In real terms the difference is very very small and even the promotional documentation from Shell specifies two identical scooby sti's both starting from a rolling start (at idle) using one gear (so minimal driver influence) giving about 1/2 car length when reaching 60mph. At 60mph 2m is covered in about 0.1 seconds - If people can really tell the difference between runs to that accuracy then they are much better at it than I :-)
The only reasons I use optimax are that
a) It has the best additives and keeps things nice and shiney (have seen a rebuilt engine almost as good as new)
b) It gives the best performance regardless if I can tell the diffrence or not.
However this needs to be viewed with the caveat that the tunning was done completely manually on a bench with a lot of time and effort. Production cars have very well defined parameter ranges/limits for altering the ignition advance and are not going to be as accurate as a specific one off tuning.
I'd be incredibly surprised if anybody notices a car run on 95 or 98 fuel. In real terms the difference is very very small and even the promotional documentation from Shell specifies two identical scooby sti's both starting from a rolling start (at idle) using one gear (so minimal driver influence) giving about 1/2 car length when reaching 60mph. At 60mph 2m is covered in about 0.1 seconds - If people can really tell the difference between runs to that accuracy then they are much better at it than I :-)
The only reasons I use optimax are that
a) It has the best additives and keeps things nice and shiney (have seen a rebuilt engine almost as good as new)
b) It gives the best performance regardless if I can tell the diffrence or not.
wolfracer said:
My pants have never noticed any difference so I stick to 95 ron.
What I would be interested to see is a dyno run on 95 and then 99 on a standard Ro.... Any Dyno owners up for it?!
What I would be interested to see is a dyno run on 95 and then 99 on a standard Ro.... Any Dyno owners up for it?!
Perhaps we should try with and without pants to see if they are responsible for the perceived difference?
stevieturbo said:
The higher the CR, and softer the engine, then definately use the best petrol you can get...
I made my 850 at the hubs, on regular 97 SUL.
I made my 850 at the hubs, on regular 97 SUL.
Forced induction does make things more complicated - most FI engines run a reduced cylinder compression ratio to account for the air charge being under positive pressure rather than pulled in. You can pretty much get this ok with a non intercooled setup as the results are easier to reproduce for accurate mapping. However throw in an intercooler than it becomes incredibly difficult to get a decent map working in all situations as the effect on the air charge is so variable given the different operating conditions.
Gassing Station | HSV & Monaro | Top of Page | What's New | My Stuff