What do you run yours on?
Discussion
I'm intrigued, who runs there's on super dooper unleaded and who's on standard? And most importantly, hand on heart does it run better on the premium stuff or is it just physiological?
I've had a tank of each and in my mind premium felt a little pokier, and idled better, but I'm still ironing out the creases on mine so it's unfair to draw a comparison just yet.
I've had a tank of each and in my mind premium felt a little pokier, and idled better, but I'm still ironing out the creases on mine so it's unfair to draw a comparison just yet.
When I had a Chimaera 500 in 2001 / 2002, it definitely pinked on normal unleaded. (Shell Optimax had just come out, now called V-Power, and it loved it)
But the 4.0 litre I have now, I can't sense any difference at all. That said, I've only tried the local supermarket super unleaded so perhaps some V-Power is worth a try.
But the 4.0 litre I have now, I can't sense any difference at all. That said, I've only tried the local supermarket super unleaded so perhaps some V-Power is worth a try.
The Clio 172 Cup gets run on cheap fuel. The only way you'll see any real advantage from running a fuel with an octane rating higher than 95Ron is to run more ignition advance.
The TVR Chimaera has a distributor that you set to run with about 10 degrees of advance at idle and 28 (5.0 litre) or up to 32 degrees (4.0 litre) at 3,750 RPM.
By 4,000 RPM the distributor is all done, it simply doesn't give you any more mechanical advance, so that's 10 - 32 degrees or 22 degrees of of mechanical advance over the 900 - 4,000 RPM window.
To get any genuine benefit from 98/99Ron petrol you really need to add another 8 degrees of advance at 4,000 RPM, but because the advance curve in the distributor is fixed the only way to achieve this is to set the timing at 18 degrees at idle so by the time you reach 4,000 RPM you're seeing the required 40 degrees of advance.
Setting your timing at 18 degrees at idle would make the engine hunt horribly.
So you see while the placebo effect is strong the science behind running the expensive higher octane fuels just doesn't stack up.
The only way you'll see any genuine & measurable benefit from the higher octane fuels and keep a nice idle is to fit an engine management system that allows you to build a dynamic three dimensional advance curve and then map it accordingly.
For example I run LPG which at 110Ron offers by far the highest octane rating available at the forecourt by far, using the Canems mappable engine management system I can still enjoy a smooth 10 degrees idle but well over 50 degrees of advance at 4,000 RPM.
Without this ability to run a lot more advance I'd be back in the dark ages of LPG when you lost power over petrol, but things have moved on so pleasingly the Canems system actually allows me to make more power on gas than petrol.
My above example is extreme but the science is exactly the same for different petrol octane ratings, put quite simply using the expensive higher octane fuels in a Chimaera that's still running the distributor is a complete waste of time.
Placebo or no placebo, you can't argue with science!
My advice to the OP is to save your money & fill with the cheapest 95Ron you can lay your hands on, the old Rover V8 loves the stuff
The TVR Chimaera has a distributor that you set to run with about 10 degrees of advance at idle and 28 (5.0 litre) or up to 32 degrees (4.0 litre) at 3,750 RPM.
By 4,000 RPM the distributor is all done, it simply doesn't give you any more mechanical advance, so that's 10 - 32 degrees or 22 degrees of of mechanical advance over the 900 - 4,000 RPM window.
To get any genuine benefit from 98/99Ron petrol you really need to add another 8 degrees of advance at 4,000 RPM, but because the advance curve in the distributor is fixed the only way to achieve this is to set the timing at 18 degrees at idle so by the time you reach 4,000 RPM you're seeing the required 40 degrees of advance.
Setting your timing at 18 degrees at idle would make the engine hunt horribly.
So you see while the placebo effect is strong the science behind running the expensive higher octane fuels just doesn't stack up.
The only way you'll see any genuine & measurable benefit from the higher octane fuels and keep a nice idle is to fit an engine management system that allows you to build a dynamic three dimensional advance curve and then map it accordingly.
For example I run LPG which at 110Ron offers by far the highest octane rating available at the forecourt by far, using the Canems mappable engine management system I can still enjoy a smooth 10 degrees idle but well over 50 degrees of advance at 4,000 RPM.
Without this ability to run a lot more advance I'd be back in the dark ages of LPG when you lost power over petrol, but things have moved on so pleasingly the Canems system actually allows me to make more power on gas than petrol.
My above example is extreme but the science is exactly the same for different petrol octane ratings, put quite simply using the expensive higher octane fuels in a Chimaera that's still running the distributor is a complete waste of time.
Placebo or no placebo, you can't argue with science!
My advice to the OP is to save your money & fill with the cheapest 95Ron you can lay your hands on, the old Rover V8 loves the stuff
No scientific explanation coming from this direction... But yes I use the good stuff,Shell V power.
When I bought the car almost 12 months ago the dealer I bought from recommended that I put the good stuff in every 2-3 tanks,so this is what I did.
Since having a service at Power and asking this very question he did't think that advice was such a good idea and his thoughts were to use the good stuff.
So the last six full fill ups have been with Shell V power... Have I noticed any difference?
The answer to that is a difficult one,but it's running really well no pinking no shunting will sit at 35-40 in 5th gear and pulls very nice in that gear so as it's running so well I've convinced myself to keep using it.
Noticed no gains in fuel consumption as I use Fuelly.com to monitor it,in fact my highest to date of 27.5 was using standard unleaded(Pretty much all Motorway).
On my last tank full I have also put in some REDEX after reading so much about it and decided to give it a go.
Scientific advice is hard to argue about,but I feel my car is running very well so I will continue to use.
When I bought the car almost 12 months ago the dealer I bought from recommended that I put the good stuff in every 2-3 tanks,so this is what I did.
Since having a service at Power and asking this very question he did't think that advice was such a good idea and his thoughts were to use the good stuff.
So the last six full fill ups have been with Shell V power... Have I noticed any difference?
The answer to that is a difficult one,but it's running really well no pinking no shunting will sit at 35-40 in 5th gear and pulls very nice in that gear so as it's running so well I've convinced myself to keep using it.
Noticed no gains in fuel consumption as I use Fuelly.com to monitor it,in fact my highest to date of 27.5 was using standard unleaded(Pretty much all Motorway).
On my last tank full I have also put in some REDEX after reading so much about it and decided to give it a go.
Scientific advice is hard to argue about,but I feel my car is running very well so I will continue to use.
Mine runs on V-Power (new V8D SII 4.6)
Mapped from the factory for Super, hence the sticker under the cap so who am I to argue?
What I would say is that I used to run on Tesco 99 as it's more convenient for me than V-Power, however the car has a lot more shunting and is (more of) a pig to drive in traffic on the Tesco stuff so I stick to the V-Power now. It's much happier all round.
Mapped from the factory for Super, hence the sticker under the cap so who am I to argue?
What I would say is that I used to run on Tesco 99 as it's more convenient for me than V-Power, however the car has a lot more shunting and is (more of) a pig to drive in traffic on the Tesco stuff so I stick to the V-Power now. It's much happier all round.
keith2.2 said:
Mapped from the factory for Super
It's a distributor for heavens sake, TVR didn't even change the bob weights and springs, it's exactly as went on a Range Rover.If you're still running the distributor all this 99/98Ron business is just an expensive placebo, but I can see if you've bought into an expensive placebo it's only natural you'll do your best to defend it's merits even if all the science is stacked against you.
The sticker that TVR applied is just there to make you feel like you've bought a serious performance car.
I'd love to see a back to back 95Ron vs 99Ron rolling road comparison, same distributor equipped car, same rollers, same ignition advance, same day ect.
I guarantee you'll see no more power!
My Chimaera 450 is very particular about fuel. It really doesn't like 95 octane and feels and sounds like it's got a few cylinders missing. Likewise in Southern Germany, where v-power is 100 octane, there is a definite smell of unburnt fuel; lots more pops and bangs though!!!
So v-power all the time for my P&J.
So v-power all the time for my P&J.
95 Ron for my 4.5, 2001 Chim - usually from BP & Shell, had no issues thankfully. I dont use 'own brand supermarket' fuel as i thought it had a higher % of biofuel (5-10%?)which made it less efficient?
Doesnt the higher octane fuel (from BP/Shell/Texaco)have additives though which help clean the engine? I remember a 'Sprint' article about it years ago, & it praised BP/Shell/Texaco's fuel for this. Supermarket fuel doesnt usually have these.
Doesnt the higher octane fuel (from BP/Shell/Texaco)have additives though which help clean the engine? I remember a 'Sprint' article about it years ago, & it praised BP/Shell/Texaco's fuel for this. Supermarket fuel doesnt usually have these.
In the old days we had 4 star which was higher octane and probably had more lead content . Why was we advised in those days to use 4 star in anything prestige and sporty ? In those days all we had were distributors . 
2 star was a no no, only to be used in lower compression vehicles like vans .
2 star was a no no, only to be used in lower compression vehicles like vans .
Edited by SILICONEKID345HP on Friday 6th June 22:28
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