octane booster

[Jmk]

boosted by 4 points with each bottle i will be useing V power classic impreza turbo i dont think the car has any cats in place at the moment is it safe to use with every tankfull ?

[youngsyr]

Jmk said:

boosted by 4 points with each bottle i will be useing V power classic impreza turbo i dont think the car has any cats in place at the moment is it safe to use with every tankfull ?

4 octane points is 0.4 of an octane number, so it will increase a 97 RON fuel to 97.4 RON - pretty pointless really.

If it boosted a fuel 4 octane numbers then that would be worth using.

[NorthDownsScooby]

Jmk said:

boosted by 4 points with each bottle i will be useing V power classic impreza turbo i dont think the car has any cats in place at the moment is it safe to use with every tankfull ?

What's the car mapped for at the mo...?

On Millers it will say on the bottle what is safe. From memory they say not to increase by more than 2RON as this could damge a cat if you have them.

Also, add the booster to the tank BEFORE filling up so that it mixes properly. Otherwise you could blast fuel through the engine of a mix that's too potent and risk damage.

Last time I ran through a pack of 10 (2RON) Millers without a remap (thought I'd see what happened) my fuel economy went down 1 or 2 mpg on average. Went up again straight after finishing. Weird.

[youngsyr]

NorthDownsScooby said:

Jmk said:

boosted by 4 points with each bottle i will be useing V power classic impreza turbo i dont think the car has any cats in place at the moment is it safe to use with every tankfull ?

What's the car mapped for at the mo...?

On Millers it will say on the bottle what is safe. From memory they say not to increase by more than 2RON as this could damge a cat if you have them.

Also, add the booster to the tank BEFORE filling up so that it mixes properly. Otherwise you could blast fuel through the engine of a mix that's too potent and risk damage.

Last time I ran through a pack of 10 (2RON) Millers without a remap (thought I'd see what happened) my fuel economy went down 1 or 2 mpg on average. Went up again straight after finishing. Weird.

It's not weird at all, octane boosters reduce a fuel's propensity to knock, a side-effect of this can be reduced calorific value, i.e. the fuel can stand higher temps before igniting, but it doesn't have as much bang when it does ignite.

You therefore need to remap the car to take advantage of the higher RON fuel or you will only see a decrease in performance and/or economy.

You experience this with high ethanol fuels - ethanol burns cooler than gasoline and has a much higher octane value (around 116 RON, I believe), so you can up the boost and run more advanced timing thus giving you more power.

However, if you just use a high ethanol fuel without adjusting the mapping, you will probably lose power and economy because ethanol has a lower calorific value than gasoline.

[NorthDownsScooby]

youngsyr said:

It's not weird at all, octane boosters reduce a fuel's propensity to knock, a side-effect of this can be reduced calorific value, i.e. the fuel can stand higher temps before igniting, but it doesn't have as much bang when it does ignite.

You therefore need to remap the car to take advantage of the higher RON fuel or you will only see a decrease in performance and/or economy.

You experience this with high ethanol fuels - ethanol burns cooler than gasoline and has a much higher octane value (around 116 RON, I believe), so you can up the boost and run more advanced timing thus giving you more power.

However, if you just use a high ethanol fuel without adjusting the mapping, you will probably lose power and economy because ethanol has a lower calorific value than gasoline.

Never thought of it like that !

I naturally assumed that reducing the propensity to knock would allow the ECU to relax and advance the timing a bit more, developing more power...and thus if I was driving at the same rate the engine would not need to work as hard leading to a MPG increase.
As it happens I was only trying the Millers for a bit of safety, rather than performance enhancing so was surprised when the reverse of what I was expecting ocurred.

[youngsyr]

NorthDownsScooby said:

youngsyr said:

It's not weird at all, octane boosters reduce a fuel's propensity to knock, a side-effect of this can be reduced calorific value, i.e. the fuel can stand higher temps before igniting, but it doesn't have as much bang when it does ignite.

You therefore need to remap the car to take advantage of the higher RON fuel or you will only see a decrease in performance and/or economy.

You experience this with high ethanol fuels - ethanol burns cooler than gasoline and has a much higher octane value (around 116 RON, I believe), so you can up the boost and run more advanced timing thus giving you more power.

However, if you just use a high ethanol fuel without adjusting the mapping, you will probably lose power and economy because ethanol has a lower calorific value than gasoline.

Never thought of it like that !

I naturally assumed that reducing the propensity to knock would allow the ECU to relax and advance the timing a bit more, developing more power...and thus if I was driving at the same rate the engine would not need to work as hard leading to a MPG increase.
As it happens I was only trying the Millers for a bit of safety, rather than performance enhancing so was surprised when the reverse of what I was expecting ocurred.

Very few ECUs will advance the timing beyond the standard settings, but most modern cars will retard the timing from standard settings if the car detects knock.

That is why so few people see a benefit from running super unleaded. The gains are there if you remap for it, especially if you've got a turbo fitted, but without the remap you're more unlikely to see any gains.

[GravelBen]

youngsyr said:

That is why so few people see a benefit from running super unleaded. The gains are there if you remap for it, especially if you've got a turbo fitted, but without the remap you're more unlikely to see any gains.

I'm unfamiliar with names of fuel grades in your country, but if by super unleaded you mean 98/99 RON as opposed to 95 (or even 91) then most owners of Jap turbo cars see gains (in fuel economy, smoothness and power) from it as its what the cars were originally designed for.

[youngsyr]

GravelBen said:

youngsyr said:

That is why so few people see a benefit from running super unleaded. The gains are there if you remap for it, especially if you've got a turbo fitted, but without the remap you're more unlikely to see any gains.

I'm unfamiliar with names of fuel grades in your country, but if by super unleaded you mean 98/99 RON as opposed to 95 (or even 91) then most owners of Jap turbo cars see gains (in fuel economy, smoothness and power) from it as its what the cars were originally designed for.

There's no such thing as 91 RON in the UK, we have 95, 97 or 99 RON, which roughly equate to 89, 91 and 93 AKI/MON.

Jap turbo cars make up a very small amount of UK cars and are an even smaller proportion when you take into account the fact that the various turbo-charged Suburus, Toyotas and Nissans (and even one version of the Evo) were released in an official UK form, so had maps for our fuel.