Octanes and Maps
Discussion
I'm trying to get this straight in my head.
Am I correct in saying that to a certain degree Fuel Octanes and Mappings need to go hand in hand? My 450 Lightweight has a standard mapping and when I owned here originally, I put Shell Super in (97Ron). No problems and she went like stink. When I bought her back 6 years later, I ran with Optimax (98Ron). Seemed to run good and fast. After a couple of months I tried Tesco 99Ron. She seemed to run ok - more pops and bangs, so I stuck with it. For a long time - at least a year, she'd been running a bit rough and hesitant. Slowly it got worst until it developed into a missfire. I went back to Optimax and this made no difference. A trip to my Indie and a faulty coil was diagnosed. Once replaced, she went like stink. Following that tank, I went back to Tesco 99Ron and now she's a little hesitant again. I'm waiting for this tank to empty before going back to optimax for a back-to-back comparison. I thought that sensors in the engine adjusted timing depending on Octane levels? Would the standard mapping restrict the sensors abilities with 99Ron fuel? If I got her remapped with 99Ron fuel, would all be ok?
Am I correct in saying that to a certain degree Fuel Octanes and Mappings need to go hand in hand? My 450 Lightweight has a standard mapping and when I owned here originally, I put Shell Super in (97Ron). No problems and she went like stink. When I bought her back 6 years later, I ran with Optimax (98Ron). Seemed to run good and fast. After a couple of months I tried Tesco 99Ron. She seemed to run ok - more pops and bangs, so I stuck with it. For a long time - at least a year, she'd been running a bit rough and hesitant. Slowly it got worst until it developed into a missfire. I went back to Optimax and this made no difference. A trip to my Indie and a faulty coil was diagnosed. Once replaced, she went like stink. Following that tank, I went back to Tesco 99Ron and now she's a little hesitant again. I'm waiting for this tank to empty before going back to optimax for a back-to-back comparison. I thought that sensors in the engine adjusted timing depending on Octane levels? Would the standard mapping restrict the sensors abilities with 99Ron fuel? If I got her remapped with 99Ron fuel, would all be ok?
I've been wondering about the same thing for a while now. Mine is also 100% standard and not sure about which RON fuel to use for the best. She does sound best on overun when using Optimax though.Also I read recently on another thread that Sainsburys Super is actually BP Ultima as they have a contract with each other, so I've been using that recently with no side effects.
Regards
Simon.
Regards
Simon.
SimonKD said:
I've been wondering about the same thing for a while now. Mine is also 100% standard and not sure about which RON fuel to use for the best. She does sound best on overun when using Optimax though.Also I read recently on another thread that Sainsburys Super is actually BP Ultima as they have a contract with each other, so I've been using that recently with no side effects.
Regards
Simon.
Sainsbury fuel does come from BP but if their super unleaded is Ultima or not, is anyones guess. I would think the Sainsburys super unleaded is a base product of Ultima but without the cleaning agents Ultima contains.???Regards
Simon.
carl_w said:
I only ever ran mine on Optimax or Tescos Super. There was a sticker near the fuel filler that said "USE 98 RON FUEL ONLY" so I reasoned that sticking some 97 RON in wasn't a good idea.
What year is your Cerb?My late 99 Lightweight has a 97Ron sticker. The Dealership (when I bought it from new) told me to always use super unleaded (97Ron at the time) and only use regular 95Ron if I got stuck. Obviously fuels have now moved on with 98 and 99Ron. I was all out to get mine remapped, but when the coil was replaced I thought bloody hell she's awesome... no need for a map (I'm all for trying to keep her reasonably standard too). Now though I'm unsure what to do as Tesco 99Ron is cheaper than Optimax (and a lot closer for me). If she needs a remap to use the 99Ron fuel to full advantage and to ensure no decrease in engine life, then at least I know what I'm aiming (and saving up) for.
So come on guys and girls.... anyone with a definitive answer?
Where's Trackcar when you need him!
The difference between 97 and 98 RON is less than 1%. So if your car is bespokely ({{spelling) mapped with amazing 100% accuracy to run on 98 RON, then you put in 97 RON, then, shock horror, you only will be running at 99% efficiency. Hardly worth bothering really. (But I do stand to be corrected and learn) 
baguaman said:
very good and relevant post!!!
CAN WE HAVE AN EXPERT ANSWER THIS ONE..
Define "expert".CAN WE HAVE AN EXPERT ANSWER THIS ONE..
I understand octane and how it relates to ignition timing if that counts. Wouldn't call myself an expert though because I'd only consider a petro-chemist an expert.
Edited by Mars on Thursday 12th July 11:34
I wrote something about Octane here which may or may not help:
http://www.pistonheads.co.uk/gassing/topic.asp?h=0...
http://www.pistonheads.co.uk/gassing/topic.asp?h=0...
Specifically relating to your original question... mapping and octane... I'll relate an experience at Emerald:
We were mapping a couple of Caterhams. They were both mapped on SUL and the ignition advanced during the mapping process until no more power could be extracted. Then it was retarded until power dropped off. It was "fixed" somewhere between both of those limits.
On mine, the headroom between the "fixed" ignition setting and where pinking would kick in was quite high, which meant I could probably have run the engine on normal UL with the usual caveats that thrashing it or running in high temps (in Europe in the Summer or simply because I was thrashing it around a track) would probably reduce that headroom and make SUL a necessity.
The other Caterham made about 60bhp less than mine (completely different components in the engine) but for some reason did not have such a large ignition headroom as mine. We think the compression ratio was higher owing to a skimmed head. Anyway, ignition was fixed between the two points between where power dropped off and pinking was induced as before, however this meant the fixed ignition setting was much closer to the pinking limit than in mine, which means that the owner would have to run on SUL always or take the much greater risk that normal UL would induce pinking.
Now I don't know how close the Cerb's standard mapping is to the maximum advanced ignition possible, so common sense dictates you run it on SUL at all times. I have an Emerald which means my ignition curve may be slightly different from standard but I'd be surprised if it was significant. I'm happy with Tesco SUL though, and haven't noticed any difference in power or quality of drive with that, BP Ultimate or Shell Optimax. I have tried a few launches with my AC22 strapped to the gearbox tunnel but the differences in my times are more to do with my foot-coordination than anything in the tank.
Remember, a car cannot make *more* power simply by putting a higher octane fuel in. It can only make less than it's supposed to by NOT putting in SUL if it was mapped to take advantage of SUL... and the differences won't show up in terms of lower power - it's more likely that you'll simply notice it running rough.
Popping and banging... well, that is generally the result of a poorly mapped car or a knackered exhaust. The level of octane in the fuel definitely makes a difference to its resistance to self-detination but by the time any unburnt fuel has made its way into the exhaust it seems unlikely that the level of octane in the original brew will contribute towards the amount of popping and banging... although I'm willing to consider its a possibility.
Remember though, the numbers printed at the pump (95, 97 or 98 RON) are all *minimums* and from reading something written on another forum by "an expert" can exceed those values by several percent.
We were mapping a couple of Caterhams. They were both mapped on SUL and the ignition advanced during the mapping process until no more power could be extracted. Then it was retarded until power dropped off. It was "fixed" somewhere between both of those limits.
On mine, the headroom between the "fixed" ignition setting and where pinking would kick in was quite high, which meant I could probably have run the engine on normal UL with the usual caveats that thrashing it or running in high temps (in Europe in the Summer or simply because I was thrashing it around a track) would probably reduce that headroom and make SUL a necessity.
The other Caterham made about 60bhp less than mine (completely different components in the engine) but for some reason did not have such a large ignition headroom as mine. We think the compression ratio was higher owing to a skimmed head. Anyway, ignition was fixed between the two points between where power dropped off and pinking was induced as before, however this meant the fixed ignition setting was much closer to the pinking limit than in mine, which means that the owner would have to run on SUL always or take the much greater risk that normal UL would induce pinking.
Now I don't know how close the Cerb's standard mapping is to the maximum advanced ignition possible, so common sense dictates you run it on SUL at all times. I have an Emerald which means my ignition curve may be slightly different from standard but I'd be surprised if it was significant. I'm happy with Tesco SUL though, and haven't noticed any difference in power or quality of drive with that, BP Ultimate or Shell Optimax. I have tried a few launches with my AC22 strapped to the gearbox tunnel but the differences in my times are more to do with my foot-coordination than anything in the tank.
Remember, a car cannot make *more* power simply by putting a higher octane fuel in. It can only make less than it's supposed to by NOT putting in SUL if it was mapped to take advantage of SUL... and the differences won't show up in terms of lower power - it's more likely that you'll simply notice it running rough.
Popping and banging... well, that is generally the result of a poorly mapped car or a knackered exhaust. The level of octane in the fuel definitely makes a difference to its resistance to self-detination but by the time any unburnt fuel has made its way into the exhaust it seems unlikely that the level of octane in the original brew will contribute towards the amount of popping and banging... although I'm willing to consider its a possibility.
Remember though, the numbers printed at the pump (95, 97 or 98 RON) are all *minimums* and from reading something written on another forum by "an expert" can exceed those values by several percent.
Edited by Mars on Thursday 12th July 11:56
That sort of implies either or both of the following:
1. Ignition is close to the limit
2. There's such a lot of inconsistency in engine performance and builds, that the single map applied to all TVR engines is so generic that TVR decided to play it safe and ask all customers to limit "TVR's" risk by using SUL.
AJP engines don't have a knock sensor, as someone above mentioned, which means if you put 95 in instead of 97/98, your engine will not detect the knocking and retard the ignition automatically, and by NOT doing that, your engine is at increased risk from pistons being eaten.
1. Ignition is close to the limit
2. There's such a lot of inconsistency in engine performance and builds, that the single map applied to all TVR engines is so generic that TVR decided to play it safe and ask all customers to limit "TVR's" risk by using SUL.
AJP engines don't have a knock sensor, as someone above mentioned, which means if you put 95 in instead of 97/98, your engine will not detect the knocking and retard the ignition automatically, and by NOT doing that, your engine is at increased risk from pistons being eaten.
Mars said:
That sort of implies either or both of the following:
1. Ignition is close to the limit
2. There's such a lot of inconsistency in engine performance and builds, that the single map applied to all TVR engines is so generic that TVR decided to play it safe and ask all customers to limit "TVR's" risk by using SUL.
AJP engines don't have a knock sensor, as someone above mentioned, which means if you put 95 in instead of 97/98, your engine will not detect the knocking and retard the ignition automatically, and by NOT doing that, your engine is at increased risk from pistons being eaten.
So in a (large) nut shell, if my Cerb does runs better (smoother and faster) with Optimax 98Ron than Tesco 99Ron, I either stick to 98Ron or I get it re-mapped to suit 99Ron - either way, when on tip-top form with the appropriate fuel, performance wise there isn't anything real to gain. And what I save using Tesco over Optimax will not offset the MBE remap cost (although a remap using either fuels will yeild an enconomical increase in mpgs as less fuel will be wasted on overrun).1. Ignition is close to the limit
2. There's such a lot of inconsistency in engine performance and builds, that the single map applied to all TVR engines is so generic that TVR decided to play it safe and ask all customers to limit "TVR's" risk by using SUL.
AJP engines don't have a knock sensor, as someone above mentioned, which means if you put 95 in instead of 97/98, your engine will not detect the knocking and retard the ignition automatically, and by NOT doing that, your engine is at increased risk from pistons being eaten.
thegreengoblet said:
So in a (large) nut shell, if my Cerb does runs better (smoother and faster) with Optimax 98Ron than Tesco 99Ron, I either stick to 98Ron or I get it re-mapped to suit 99Ron - either way, when on tip-top form with the appropriate fuel, performance wise there isn't anything real to gain. And what I save using Tesco over Optimax will not offset the MBE remap cost (although a remap using either fuels will yeild an enconomical increase in mpgs as less fuel will be wasted on overrun).
No, if you have an ignition curve suitable for 98, then it will be suitable for 99 also. 99 is just *more* resistance to self-detonation than 98, so you could go more advanced with your ignition settings on 99 than 98, however if you're mapped for 98 then 99 is technically *more* than you need.The differences people are claiming between Optimax and *any* other SUL brew is something I really don't understand. It's possible, from conversations I've read on very many forums, that the Optimax brew may contain something that engines like. Conversely it might actually NOT have something that every other brew has... again which engines like.
However, that you can detect a difference on Optimax over Tesco SUL is something that concerns me because *I* cannot with *my* Cerb. In fact I've never noticed any difference between Optimax or any other brew of fuel in the Caterham (previous to the Cerb) either, and I have had my cars well set-up on reputable rollers by reputable operators where I have stood and observed the mapping process myself.
What I'm trying to qualify is that it is my belief that very many people (not necessarily you though) convince themselves that Optimax is better when in fact there is no measurable difference to their car running on any other SUL. Having said that, I cannot totally rule out Optimax's supposed benefits because there are people I know, who understand the science behind all this, that have claimed benefits from Optimax too. However to my recall, no-one yet has proved this benefit from empirical measurements and if I recall correctly, improvements have actually been disproved by one notable RR operator.
I'll try to find out more info about that "test".
With the Caterham, given the headroom available to its ignition curve mentioned above, I could have run it on 95RON and when doing so I *should* have been able to detetect a difference which again *should* have been measureable given that 95RON contains more energy (calories) than 97, 98 or 99 simply by being less diluted by the octane. On the odd occasions where I have had no choice than to use 95 I have detected no difference whatsoever.
In fact, I need never have run my car on SUL given the headroom, except maybe on track or in hot countries (I toured all through Europe and Scandinavia in it) where the headroom gets eaten up by increasing head temperatures. However I used SUL wherever it was available simply as a risk reduction technique. The engine would have cost more to rebuild than the Cerb's 4.5 so it was a very small price to pay... in the same way as using Mobil 1 over any other brand of synth oil was a risk reduction technique.
It's quite interesting stuff but the important thing that my years on forums with the Caterham have taught me is that you should always seek to measure the differences. Many people don't and much cock 'n' bull is spouted as truth. As I mentioned above, I've been messing about with an AC22 in the Cerb. I got very accurate results with it when I was at Santa Pod a few years ago - managing to calibrate it to within 1/10th of the official timing slip however while teaching myself to launch the Cerb for the Fighting Torque competition, I discovered my timings were vastly different on the same day with the same fuel owing to my lack of precision of technique. On other days when I tried with a different brand of fuel in the car, I was at once both faster and slower than previously.
Just to put it into perspective.
Thanks for the detail Mars. Interesting stuff.
I too thought that my car behaved the same when I first changed from Optimax to Tesco just over a year ago (except for the increase in pops and bangs). However I believe she wasn't running spot on even back then (due to the coil breakdown).
There was a study in the news section of PH a while back that basically concluded that Tesco 99 gave the largest bhp increase over SUL with Optimax a good way short of Tesco. I think it was something like 10bhp using an M3 on a rolling road. Following Optimax was BP Ultimate which was the worst of the "performance" fuels with a 1BHP increase over standard SULs.
So I'd concluded that my rough running could be down to the fuels potency and my standard mapping. Obviously this is wrong although there maybe some "magic" going on with Optimax.
I need to empty this tank before I can go back to Optimax to see if it makes any difference - which is harder than it sounds as my wife's going to give birth any moment soon and I'm on constant standy. It'll be no good if she phoned me and I was a million miles away on a hack!
I should be able to report back early next week.
I too thought that my car behaved the same when I first changed from Optimax to Tesco just over a year ago (except for the increase in pops and bangs). However I believe she wasn't running spot on even back then (due to the coil breakdown).
There was a study in the news section of PH a while back that basically concluded that Tesco 99 gave the largest bhp increase over SUL with Optimax a good way short of Tesco. I think it was something like 10bhp using an M3 on a rolling road. Following Optimax was BP Ultimate which was the worst of the "performance" fuels with a 1BHP increase over standard SULs.
So I'd concluded that my rough running could be down to the fuels potency and my standard mapping. Obviously this is wrong although there maybe some "magic" going on with Optimax.
I need to empty this tank before I can go back to Optimax to see if it makes any difference - which is harder than it sounds as my wife's going to give birth any moment soon and I'm on constant standy. It'll be no good if she phoned me and I was a million miles away on a hack!
I should be able to report back early next week.
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