Shell V power

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Shell V power

Postby iain cooper » Sun Mar 23, 2014 10:25 am

I wonder what your thoughts are on using Shell V power in the MX5 ?

do you think the extra cost per litre is worth it ? and if so what benefits do you perceive ?

Iain
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Re: Shell V power

Postby Macscorcher » Sun Mar 23, 2014 10:43 am

Hello Iain, waiting to get shot down in flames here lol but I use V power all the time in my mk3. I believe I read somewhere that the ecu is self learning so it adjusts to the RON rating of the fuel it's running on. Defo notice a difference in my car when running non v power & then going back to it engine seems to run smoother & happier to rev & responds quicker.

Not sure of the benefits of using it in older mx5s as don't know as much about them. Certainly I also run my Classic Mini on V power but it's been tuned on a rolling road to run on it !

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Re: Shell V power

Postby drumtochty » Sun Mar 23, 2014 11:59 am

There would only be an advantage if the car ecu is setup at the factory to advance the ignition further than it would with normal UK unleaded fuel until the knock sensor stops it advancing.

I'm of the opinion that a good percentage of cars are set for the countries fuel.

On the MK2 I have found no noticeable increase in performance when I have used a few tank fulls of high octane fuel.

I have only used it on one occasion in my Mk3 and found no difference.

In saying that the only way to test it is to have the acceleration measured over say 6 tankfuls of super unleaded by an uninterested third party and compare the pre super unleaded petrol acceleration to the post super unleaded petrol acceleration.

Therefore if someone can post a link to a set of these figures produced without the car owner involved in their collection, I would be interested at that.

Otherwise this is a motherhood and apple pie belief as our US friends would say.

eddie
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Re: Shell V power

Postby sclements » Mon Mar 24, 2014 12:56 am

run shell V power in my Clan as it runs a 11.5-11.8:1 compression ratio and pinks on standard unleaded so yes it does work however can't say if MX5's can taste the difference but with modern engines running knock sensors they will retard the timing if required resulting in less power. If your happy to pay the premium and can feel the difference I'd say go for it but if not stick with regular unleaded whats a couple of bhp between friends :lol: .

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Re: Shell V power

Postby gar374 » Mon Mar 24, 2014 2:07 am

Hi,

The higher the RON number (octane rating) the more resistant the fuel is to pinking or knocking, there is no more power in the fuel as far as I'm aware.
Knocking is when the fuel is ignited in the combustion chamber either prior to the spark plug intends it to happen, or ignites in more than one place in the combustion chamber, so spark plug and somewhere else. In other words, not controlled by the ignition system.

Scott's clan doesn't pink, or knock when using v power and does on normal fuel presumably due to the compression ratio.

Compression causes heat, more compression, more heat, more chance on knocking. This is the principal of diesel engines. They typically run between 14 and 22 to 1 in order for compression ignition to occur.

The advantage of knock resistance is the timing can be advanced more, which in turn will cause more heat.

So, if you run you're mx5 with the timing advanced, then running v-power or tesco 99 may help you. You could happily run 14 degrees BTDC on normal fuel, maybe a bit more before knocking occurs, you could then swap to v-power to stop the knocking. Not the ideal way to tune a car just and example! :-0

As Bob says, his Mini (proper one) is tuned to run on it (I'd guess ignition timing is advance beyond what normal fuel (95RON in the UK) can cope with. For information US "gas" is generally a lower RON about 87 for standard fuel.

Modern cars use an ECU in order to control the timing advance, they stop the advancing when knock is detected. That being the case, more advance can be applied using v-power/tesco 99, therefore more power can be attained. This would be the learning the ECU does.

I used to run my astra VXR on tesco 99 but that was turbocharged. I could feel the difference but it wasn't much tbh. The flat spot in fourth was less pronounced, more miles to a tank and slightly better bottom end torque (below 2k).

Hope that helps.

Cheers
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Re: Shell V power

Postby gm » Mon Mar 24, 2014 2:52 am

I usually fling in a tank of 'posh' on the way to knockhill in my mk1, it probably doesn't make much difference but I need all the help I can get !
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Re: Shell V power

Postby iain cooper » Mon Mar 24, 2014 6:31 pm

thanks for the interesting comments.

We recently had a new Waitrose open with a Shell fuel outlet, and I have had a few tankfuls of V power, but can't detect much difference so far.

I was also thinking that it might keep the fuel system clean, but I suppose that will only be evident long term.

think I'll continue to buy it and monitor the situation.

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