The SUL report
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From: Bradford
Well, as I said I would in a recent thread I switched back to SUL to see if it made any difference to my car! Er, yes 
For those that don't know, my car is an MY99 with a full scoobysport decat, a TEK2.5 remap, an STIV intercooler and a dawes to control the boost set at 1.25bar.
I'm sitting on the fence with regards to smoothness as both fuels seem to be the same. However, there does seem to be a difference in performance
When I floor it with SUL the car seems to be more willing to get up and go. When the boost comes in everything feels pretty much as per Optimax but then......we hit what I call the 'John Banks zone'! This is the part in the rev range where the TDO4 is starting to run out of puff but the TEK2.5 seems to have made the most difference. With optimax there was an obvious (and very brief) flat spot where the turbo ran out and the JB zone took over. This is now more pronouced and the car pulls fecking hard up to near the redline. It's charging a lot more between corners and I find I'm having to reel her in with the brakes far earlier
Defo going to stick with SUL I think as the car is far more enjoyable to drive. Economy does seem to be down a little
so there is a penalty to pay and I'd probably use octaine booster at crail/track/road thrash just to be extra sure, re: det. I'd highly recommend all TEK'ers to give SUL a try and see what they think
For those that don't know, my car is an MY99 with a full scoobysport decat, a TEK2.5 remap, an STIV intercooler and a dawes to control the boost set at 1.25bar.
I'm sitting on the fence with regards to smoothness as both fuels seem to be the same. However, there does seem to be a difference in performance
When I floor it with SUL the car seems to be more willing to get up and go. When the boost comes in everything feels pretty much as per Optimax but then......we hit what I call the 'John Banks zone'! This is the part in the rev range where the TDO4 is starting to run out of puff but the TEK2.5 seems to have made the most difference. With optimax there was an obvious (and very brief) flat spot where the turbo ran out and the JB zone took over. This is now more pronouced and the car pulls fecking hard up to near the redline. It's charging a lot more between corners and I find I'm having to reel her in with the brakes far earlier Defo going to stick with SUL I think as the car is far more enjoyable to drive. Economy does seem to be down a little
so there is a penalty to pay and I'd probably use octaine booster at crail/track/road thrash just to be extra sure, re: det. I'd highly recommend all TEK'ers to give SUL a try and see what they think
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From: Scotland
Told you so 
AJ........ I'll tell you why he's be's been smiling more, and believe you me, it's got nothing to do with either SUL or you
Cos after all his mods he finally whipped my *** (not in the physical sense ) and it was somewhat conclusive, to say the least 
Still, my visit to Falkland next week should level the playing field a bit
AJ........ I'll tell you why he's be's been smiling more, and believe you me, it's got nothing to do with either SUL or you
Cos after all his mods he finally whipped my *** (not in the physical sense
) and it was somewhat conclusive, to say the least Still, my visit to Falkland next week should level the playing field a bit
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From: Bradford
Well there was the point in the evening when I had 7k rpm charging through a fully engaged clutch and was going nowhere The horror, the smell Concluded that you really don't need many revs to launch my car and not bog down.......still reeled him in though
You'll not last 2 minutes with a new downpipe before you go tunnel hunting
I can just see you now: Here's my credit car - make it faster than a P1
[Edited by Saxo Boy - 12/13/2002 2:07:20 PM]
The horror, the smell Concluded that you really don't need many revs to launch my car and not bog down.......still reeled him in though You'll not last 2 minutes with a new downpipe before you go tunnel hunting
I can just see you now: Here's my credit car - make it faster than a P1
[Edited by Saxo Boy - 12/13/2002 2:07:20 PM]
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From: Bradford
For local information (hope this isn't seen as advertising, its not!) but the garage I use is the Esso at the foot of hillend and it seems to have very consistent SUL! I ran the SaxoSuperCar on it so nuff said 
Someone recently mentioned water in forecourt fuel and suggested high turnover garages wouldn't have so much, maybe this is a contributing factor as that garage is always busy.
Someone recently mentioned water in forecourt fuel and suggested high turnover garages wouldn't have so much, maybe this is a contributing factor as that garage is always busy.
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From: Bradford
Speedking, I'm planning to mix and match to see if I can get an 'ideal ratio' of tanks of optimax to SUL.
The VTS was standard and I presumed it could take advantage of SUL/Optimax. It defo got better fuel economy with those fuels over 95 RON, was smoother and I'd argue fractionally more pokey.
The VTS was standard and I presumed it could take advantage of SUL/Optimax. It defo got better fuel economy with those fuels over 95 RON, was smoother and I'd argue fractionally more pokey.
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From: Bradford
Does this mean I get to go out and play all by myself then ??
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Update: I can confirm that the car seems to be less smooth now It just feels a little rough around the edges on the SUL but at least its faster The SUL is a bit like coffee with milk instead of cream....it's got the kick of the caffine but lacks that final touch of class I suspect, based on recent reports for Sipie, that octaine booster would smooth it out and would be the best combo for my car but she's a high miler and I'm not too sure about the idea of adding another £3 to the cost of a tank-full.
It just feels a little rough around the edges on the SUL but at least its faster The SUL is a bit like coffee with milk instead of cream....it's got the kick of the caffine but lacks that final touch of class I suspect, based on recent reports for Sipie, that octaine booster would smooth it out and would be the best combo for my car but she's a high miler and I'm not too sure about the idea of adding another £3 to the cost of a tank-full.
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SB,
It's all about calorific value vs anti knock (or octane rating)
Some normal unleadeads have a higher calroific value than Optimax and so will produce more power however they have a lower octane rating and so will be more prone to detonation.
Think of it this way.
Normal unleaded with a higher CV allows a maximum of 280bhp, for example, compared to Optimax which allows a maximum of 260bhp.
Now due to detonation, you can only produce 240bhp from normal unleaded but can produce 250bhp from Optimax because of the higher octane rating. However in the mid range (where det is not as common) you can get more power out of the higher CV SUL.
Therefore your car pulls better from lower down with a high CV fuel giving extra power but you *may* lose out at the top end due to 'knock' detection chopping the ignition but you won't notice this as much because it has been 'masked' by the extra mid range punch.
The ECU 'learns' the amount of ignition retard needed and so holds the timing back after a few tankfuls (which is what you're experiencing now). You then you switch back to Optimax and the ECU can advance the ignition more because of the lack of det and so the car feels stronger at the top end when going back to Optimax.
The ECU relearns the Optimax settings and you then switch back to SUL and start the cycle all over again......
Just my 2p worth
Andy
It's all about calorific value vs anti knock (or octane rating)
Some normal unleadeads have a higher calroific value than Optimax and so will produce more power however they have a lower octane rating and so will be more prone to detonation.
Think of it this way.
Normal unleaded with a higher CV allows a maximum of 280bhp, for example, compared to Optimax which allows a maximum of 260bhp.
Now due to detonation, you can only produce 240bhp from normal unleaded but can produce 250bhp from Optimax because of the higher octane rating. However in the mid range (where det is not as common) you can get more power out of the higher CV SUL.
Therefore your car pulls better from lower down with a high CV fuel giving extra power but you *may* lose out at the top end due to 'knock' detection chopping the ignition but you won't notice this as much because it has been 'masked' by the extra mid range punch.
The ECU 'learns' the amount of ignition retard needed and so holds the timing back after a few tankfuls (which is what you're experiencing now). You then you switch back to Optimax and the ECU can advance the ignition more because of the lack of det and so the car feels stronger at the top end when going back to Optimax.
The ECU relearns the Optimax settings and you then switch back to SUL and start the cycle all over again......
Just my 2p worth
Andy