What fuel to use?
Discussion
Hi all,
Being a bit of a tight bas't I've always used regular unleaded in my cars. For the last year I've owned a Scirocco R (2015 latest shape etc) and having had it stage one tuned - so it's probably kicking out 310bhp and 300lbs/ft torque give or take - and it's mighty quick for sure - like super f'g quick - fantastic car - absolutely love it.
BUT.
I've never been that happy with the low-down torque from it - even after having it stage one tuned. Like below 2000 rpm it's positively dull. Talking to the guy who tuned the car the other day and relating to him that my GF has a basic Audi TT and that thing feels WAY better under 2000rpm (and yet it's got less bhp and less torque) he said yes but that engine has a smaller turbo so it spools up quicker - less turbo lag.
Ah ha I said so how can we fix my car then and he said well we could put another turbo on it - make it a twin turbo but then he said that would cost a f'g fortune so before messing with the ECU again (which is another way we could go) he said what fuel do you use and I said regular unleaded he said try super-unleaded for a couple of tanks.
So earlier today I loaded up with super unleaded (145p/l which I thought wasn't too bad) - and my f'g word I think it's MILES better. Like just WAY f'g better. Particularly below 2000rpm.
How come?
What is it about modern turbo engines that make using super-unleaded such a good idea?
Any mechanics here who know the science behind this?
Let me know if you know - or if you know where to look - because I'd really like to know the reason how come changing the fuel has made SUCH a difference.
Or anybody else out there who has experienced changing fuels and the impact it had on the performance of their car - I'd be interested in those stories too.
Thanks.
James.
Being a bit of a tight bas't I've always used regular unleaded in my cars. For the last year I've owned a Scirocco R (2015 latest shape etc) and having had it stage one tuned - so it's probably kicking out 310bhp and 300lbs/ft torque give or take - and it's mighty quick for sure - like super f'g quick - fantastic car - absolutely love it.
BUT.
I've never been that happy with the low-down torque from it - even after having it stage one tuned. Like below 2000 rpm it's positively dull. Talking to the guy who tuned the car the other day and relating to him that my GF has a basic Audi TT and that thing feels WAY better under 2000rpm (and yet it's got less bhp and less torque) he said yes but that engine has a smaller turbo so it spools up quicker - less turbo lag.
Ah ha I said so how can we fix my car then and he said well we could put another turbo on it - make it a twin turbo but then he said that would cost a f'g fortune so before messing with the ECU again (which is another way we could go) he said what fuel do you use and I said regular unleaded he said try super-unleaded for a couple of tanks.
So earlier today I loaded up with super unleaded (145p/l which I thought wasn't too bad) - and my f'g word I think it's MILES better. Like just WAY f'g better. Particularly below 2000rpm.
How come?
What is it about modern turbo engines that make using super-unleaded such a good idea?
Any mechanics here who know the science behind this?
Let me know if you know - or if you know where to look - because I'd really like to know the reason how come changing the fuel has made SUCH a difference.
Or anybody else out there who has experienced changing fuels and the impact it had on the performance of their car - I'd be interested in those stories too.
Thanks.
James.
Higher octane = higher compression = more torque
Particularly effective in forced induction cars like yours.
Given yours is tuned, unless you know it's been tuned for 95 you should also run 97,98 or pref 99 to protect your engine from knock.
I only ever use 99. It's been proven over and over again that engines run more efficiently, so you offset the cost with the increase in MPG yet get between 5-10 % more torque on forced induction.
Particularly effective in forced induction cars like yours.
Given yours is tuned, unless you know it's been tuned for 95 you should also run 97,98 or pref 99 to protect your engine from knock.
I only ever use 99. It's been proven over and over again that engines run more efficiently, so you offset the cost with the increase in MPG yet get between 5-10 % more torque on forced induction.
Harrison-91xcg said:
Higher octane = higher compression = more torque
Particularly effective in forced induction cars like yours.
Given yours is tuned, unless you know it's been tuned for 95 you should also run 97,98 or pref 99 to protect your engine from knock.
I only ever use 99. It's been proven over and over again that engines run more efficiently, so you offset the cost with the increase in MPG yet get between 5-10 % more torque on forced induction.
How does higher octane = higher compression?Particularly effective in forced induction cars like yours.
Given yours is tuned, unless you know it's been tuned for 95 you should also run 97,98 or pref 99 to protect your engine from knock.
I only ever use 99. It's been proven over and over again that engines run more efficiently, so you offset the cost with the increase in MPG yet get between 5-10 % more torque on forced induction.
Harrison-91xcg said:
Higher octane = higher compression = more torque
Particularly effective in forced induction cars like yours.
Given yours is tuned, unless you know it's been tuned for 95 you should also run 97,98 or pref 99 to protect your engine from knock.
I only ever use 99. It's been proven over and over again that engines run more efficiently, so you offset the cost with the increase in MPG yet get between 5-10 % more torque on forced induction.
Interesting thanks.Particularly effective in forced induction cars like yours.
Given yours is tuned, unless you know it's been tuned for 95 you should also run 97,98 or pref 99 to protect your engine from knock.
I only ever use 99. It's been proven over and over again that engines run more efficiently, so you offset the cost with the increase in MPG yet get between 5-10 % more torque on forced induction.
thebraketester said:
It could be because the R uses the k04 turbo vs the other TT you mention which probably is k03 based
Bigger turbo = more lag. And sadly there is no real way around without it becoming expensive.
That seems to be the case. Though I am experiencing quite a bit more low-down torque just by putting super-unleaded in there.Bigger turbo = more lag. And sadly there is no real way around without it becoming expensive.
I'm also feeling that the gearbox is willing to change down quicker when I put my foot down - or am I imaging that? How would changing the fuel change how quickly it decides to change down a gear? But it does feel a bit like that. Like before it would just drag and then change down whereas now it seems to think ah f
k it let's change down right fking now.jamesgareth said:
thebraketester said:
It could be because the R uses the k04 turbo vs the other TT you mention which probably is k03 based
Bigger turbo = more lag. And sadly there is no real way around without it becoming expensive.
That seems to be the case. Though I am experiencing quite a bit more low-down torque just by putting super-unleaded in there.Bigger turbo = more lag. And sadly there is no real way around without it becoming expensive.
I'm also feeling that the gearbox is willing to change down quicker when I put my foot down - or am I imaging that? How would changing the fuel change how quickly it decides to change down a gear? But it does feel a bit like that. Like before it would just drag and then change down whereas now it seems to think ah f
k it let's change down right fking now.Scrump said:
Harrison-91xcg said:
Higher octane = higher compression = more torque
Particularly effective in forced induction cars like yours.
Given yours is tuned, unless you know it's been tuned for 95 you should also run 97,98 or pref 99 to protect your engine from knock.
I only ever use 99. It's been proven over and over again that engines run more efficiently, so you offset the cost with the increase in MPG yet get between 5-10 % more torque on forced induction.
How does higher octane = higher compression?Particularly effective in forced induction cars like yours.
Given yours is tuned, unless you know it's been tuned for 95 you should also run 97,98 or pref 99 to protect your engine from knock.
I only ever use 99. It's been proven over and over again that engines run more efficiently, so you offset the cost with the increase in MPG yet get between 5-10 % more torque on forced induction.
littleredrooster said:
Scrump said:
Harrison-91xcg said:
Higher octane = higher compression = more torque
Particularly effective in forced induction cars like yours.
Given yours is tuned, unless you know it's been tuned for 95 you should also run 97,98 or pref 99 to protect your engine from knock.
I only ever use 99. It's been proven over and over again that engines run more efficiently, so you offset the cost with the increase in MPG yet get between 5-10 % more torque on forced induction.
How does higher octane = higher compression?Particularly effective in forced induction cars like yours.
Given yours is tuned, unless you know it's been tuned for 95 you should also run 97,98 or pref 99 to protect your engine from knock.
I only ever use 99. It's been proven over and over again that engines run more efficiently, so you offset the cost with the increase in MPG yet get between 5-10 % more torque on forced induction.
It doesn't.
As others have said, if it was mapped on 99, then it will perform at its best on 99, although your statement of WAY better I find rather surprising.
I have had track day cars tuned on 99 which I would only use on a track day, but have had no issues & no noticeable difference when run on 95 whilst just on daily duty, even cars like an R53 which is known to be very sensitive to RON when tuned.
I have had track day cars tuned on 99 which I would only use on a track day, but have had no issues & no noticeable difference when run on 95 whilst just on daily duty, even cars like an R53 which is known to be very sensitive to RON when tuned.
E-bmw said:
littleredrooster said:
Scrump said:
Harrison-91xcg said:
Higher octane = higher compression = more torque
Particularly effective in forced induction cars like yours.
Given yours is tuned, unless you know it's been tuned for 95 you should also run 97,98 or pref 99 to protect your engine from knock.
I only ever use 99. It's been proven over and over again that engines run more efficiently, so you offset the cost with the increase in MPG yet get between 5-10 % more torque on forced induction.
How does higher octane = higher compression?Particularly effective in forced induction cars like yours.
Given yours is tuned, unless you know it's been tuned for 95 you should also run 97,98 or pref 99 to protect your engine from knock.
I only ever use 99. It's been proven over and over again that engines run more efficiently, so you offset the cost with the increase in MPG yet get between 5-10 % more torque on forced induction.
It doesn't.
Scrump said:
How does higher octane = higher compression?
It doesn't cause higher compression, but it is less inclined to detonation which means the limits of cylinder pressure + fueling + ignition timing are further away. In other words you can use a higher compression ratio and/or more boost and/or more aggressive tune without being detonation limited.A lot of misinformation here.
Turbocharged engines create higher cylinder pressure. With higher cylinder pressure comes higher temperature. Petrol has an auto ignition point, and this is the limiting factor. The fuel will auto ignite before the flame front from the spark has reached it in the cylinder. This causes detonation (knock) which 1. Can severely damage the engine and 2) trigger the knock sensor (if fitted), which will retard the spark timing and reduce torque.
The fuel's ability to withstand auto ignition is directly related to the Octane rating. Higher octane means greater resistance to auto ignition.
A greater resistance to auto ignition allows more advanced spark timing, higher boost pressures and ultimately more torque.
Turbocharged engines create higher cylinder pressure. With higher cylinder pressure comes higher temperature. Petrol has an auto ignition point, and this is the limiting factor. The fuel will auto ignite before the flame front from the spark has reached it in the cylinder. This causes detonation (knock) which 1. Can severely damage the engine and 2) trigger the knock sensor (if fitted), which will retard the spark timing and reduce torque.
The fuel's ability to withstand auto ignition is directly related to the Octane rating. Higher octane means greater resistance to auto ignition.
A greater resistance to auto ignition allows more advanced spark timing, higher boost pressures and ultimately more torque.
Doesn't the fuel cap have a sticker on the inside saying the recommended fuel is min 97ron....
When you had the car remapped was it running on 95ron at the time?
With 97+/super unleaded a Stage 1 Scirocco should be around 300-315hp/300lbft
Has the dsg gearbox also been played with whilst the engine map was done?
When you had the car remapped was it running on 95ron at the time?
With 97+/super unleaded a Stage 1 Scirocco should be around 300-315hp/300lbft
Has the dsg gearbox also been played with whilst the engine map was done?
thebraketester said:
Placebo. Almost certainly.
Maybe not. If the engine starts producing power more quikcly - now that it's on super-unleaded - then the gearbox will detect that and as the load increases - increases faster than it used to - it will boot down quicker. Anyhow. I ain't no mechanic but that makes sense to my brain.GreenV8S said:
It doesn't cause higher compression, but it is less inclined to detonation which means the limits of cylinder pressure + fueling + ignition timing are further away. In other words you can use a higher compression ratio and/or more boost and/or more aggressive tune without being detonation limited.
The man sounds like he knows what he's talking about.....Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff