optimax

[modarr]

It would appear that Optimax could release more power from the engine in the NSX.
However, the ECU needs re-setting and then the car caned through the gears to advance the ignition map up to the higher RON that Optimax provides. It then needs to be kept fuelled on Optimax to avoid the ignition map returning to that suitable for a lower RON petrol.

Anyone know a quick ECU re-set?

Mo

[MattS]

Mo,

Where did you glean this from? I thought that most modern cars could detect differences in octane rating, by the way the fuel burns (for protective reasons) and adjust engine performance accordingly.

Matt

[modarr]

I was informed of this by a mutual acquaintance a while back.
It was confirmed bt 5th Gear recently.

Re-setting the ECU is the best way to ensure the ignition mapping responds to the higher octane fuel.

I'm not fully sure but swear by Optimax on trackdays, I take it with me in Jerry cans and generally sniff the stuff too.

[AR]

I've read that Optimax starts as 95RON then gets stuff added to bump up the RON and clean up your engine. Apparently it degrades rather qyuickly back down to 95 RON and thus they no longer label it at a specific RON level. I can't wait for Tesco to introduce the 99 RON near my home.

[ctrlaltdelboy]

I spotted the Tesco 99 whilst filling up with some 95 yesterday and was curious.......

[sportyking]

My s2000 is set up specifically to Optimax, courtesey of a little anonymous box. I found local Tesco 99 Ron not long ago and am on my first full tank but cant say it feels better and may even be worse, particularly in fuel consumption, so back to Optimax me thinks.

[UltraViolet]

I know this will be not most people's views as Optimax and the benefits is one of the great topics of discussion on internet forums and most of those doing the talking believe it gives them more power.

Now lets be radical and assume that media/tv shows don't always get things 100% accurate - why let fact get in the way of a good story?

Also lets move to one side the fact Shell got fined and told it had to remove the claims about Optimax increasing power.

Octane rating matters for how the fuel is burned. If your car needs a high octane rating, it will cause poor detonation and 'knock' if not fed what it needs.

Calories (the energy) is what produces power.

If your engine burns the fuel cleanly, it releases the energy in the fuel. Energy gives the power so what is important if you are talking power is what calorific value is in the fuel.

I am not getting into 'my car feels better' or 'mine uses less fuel' etc - placebos or not - if you like using Optimax, great. If you believe this is a nice easy way to gain extra power - great. I just think worth fetching a little basic science into the discussion as everywhere you look, people seem to think Ron = Power.

[AR]

Aside from Optimax, if a Car's ECU can compensate for higher RON then will it not produce more power?

[UltraViolet]

My understanding is that IF your car can burn 95 ROM fuel efficiently, IF that fuel contains x calorific value, it will gain that amount of energy.

IF however your car cannot burn it efficiently and knocks, it needs the higher octane.

IF the higher octane fuel has the same calorific value, there is no additional power - unless your car was unable to retrieve all the energy previously.

You can have fuels of different octane ratings with the same calorific value, so if your car burns both fully efficiently - same power.

It is even possible to have a fuel with lower octane rating but higher calorific value (Esso Super unleaded is a good example - lower octane than Optimax, higher calorific value, so if you burn both fully efficiently, the Esso fuel would give most power)

It is correct that Optimax deteriorates quickly, but so long as the garage is fairly busy, it should be fine when you buy it.... no good though if your car then sits in the garage with the fuel going off in its tank for a couple of weeks before you use it.

If the higher octane fuels have greater calorific values, then you will benefit. But is isn't anything like as simple as 'which has highest RON' (unless you have detonation problems and are just trying to prevent knocking.)

[MattS]

Interesting stuff indeed... It follows that what we really need to be told about fuel is its calorific/energy - how much energy it releases when ignited. Not the RON, which refers to how compressible the fuel is before it ignites..

Would I be right in thinking that biofuels such as ethanol and methanol, added to petrol increase the fuel's calorific value (and the green credentials) and thus performance? Presumably N2O does much the same thing?

[AR]

OK next week rejetting, remaping and we run Methanol then, LOL.

My NSX seems to run just as well on Tesco's 97 as it does on Optimax. Could be that the Optimax was old.

I was under the impression that higher-octane fuels burned slower than lower-octane fuels.

Cheers

AR

[sportyking]

As already said it is the ability of the vehicle to efficiently burn a specific fuel that is paramount. If a vehicle is designed to run on 95 RON/98/what have you, then that is where it will run most efficiently. One of the things that attracts me to a NSX is that it will run on standard pump fuel with ample power/response and that's what I would give it unless it had been modded (ECU or suchlike).
The S2000 (as an example) engine and ECU is designed to take advantage of higher Octane fuels and you don't gain anything using them, you lose performance by not using them. How else are they going to get 118Bhp per litre and more in the JDM car using 100+ RON. The key is the compression ratio and engine mapping.

Nitrous Oxide contains a much higher percentage of oxygen than air and it is this that allows the car to burn much more fuel and produce more power, the Nitrous is not a fuel source in itself. More akin to Super/turbo charging than increasing octane.

[ctrlaltdelboy]

if anyone is really interested in this topic and has about a week to spare, there's a relevant thread on the GT-R forum which started 3 and a half years ago and has had 359 replies to date.

http://www.gtr.co.uk/forum/upload/showthread.php?t=2480

[modarr]

From my experience supercharging the MX5 I know that the higher the Octane, the more I can advance the ignition timing and gain power. I think this is because by allowing the fuel to be ignited at a slightly higher compression it will create more power akin to skimming the head to raise compression ratio.
With the NSX the power available may be reduced slightly with 95 RON fuel but without driving flat out you would not notice. Optimax ought to allow the optimal ignition timing curve and raise peak bhp, nothing to do with calorific value, but everything to do with the timing of fuel/air ignition as it is being compressed.
I may well be wrong here but maybe one day a power run on a rolling road may be possible.

[ctrlaltdelboy]

you are quite right Mo

the benefit of a higher octane rating is not more power in and of itself, but that it allows a more advanced timing and therefore higher fuel compression at point of ignition to be dialled in to the map than would otherwise be safe (the result of doing this without sufficient octane is detonation)

so yes, using higher octane fuel can enable you to get more power out of your engine provided you tune it to take advantage of the bigger safety net provided by the higher octane fuel.

as has been stated already, some ECU's self-tune to run optimally on the octane level detected, and any ECu that does this will of course do it much better after a reset.

[MattS]

It follows then that resetting the ECU ( ie going back to default settings - which for most cars is 95RON) could well be a waste of time for many - and may even produce retarded performance until the ECU relearns that a higher RON petrol is being used again.

If the ECU's learnt to use 98RON (cos you've been filling it with Optimax etc) and you reset (ie take it back to the manufacturer's 95RON) - it's surely going to retard performance for a time.

If the manufacturer ECU default is set to give optimium performance at 98RON (turbo cars, higher performance cars) and you've been using 95RON petrol, then resetting will give you more performance.However if you've been using Tesco's 99RON and you reset back to 98RON you're going to lose a bit.

I think the reason they reset the ECUs on the Fifth Gear prog was to take the ECU back to the manufacturer's default settings - this would explain why the 'sportier' cars showed an improvement with higher octane fuel/optimax (as they're set to run at 98RON) and the 'normal' cars didn't show any real improvement as their newly reset ECUs can't take advantage of the 98 stuff. They also didn't know what the cars had been run on before - if the sporty ones had been run on 95RON, filling up with 98RON would make no difference initially and a boring article!

But, calorific value is still more important to performance and will allow your engine to get to its max BHP sooner. From reading around it seems that Tesco's 99RON has a lower calorific value than Esso 98 and Optimax which may explain why optimax gives some people better performance.

[Rob_Fenn]

Regardless if Optimax improves performance or not, it is also meant to have additives to help keep the engine clean. Something independants have proven haven't they?

I won't pretend to know much, so don't quote me, but i thought with the better octane fuel, the car then allowed more air in which combined equals a few more bhp? As far as i am aware every new car with a knock sensor is capable of doing this. Equally, they can cope with 91Ron fuel but at the expense or power. For example, a Clio 182 will only produce the quoted max power with 97ron.

I am lucky to get 99ron Tesco fuel just across the road (shame its always packed by mums!) and i have noticed better MPG in my Mini.

-Rob

[swlabhot]

you are quite right Mo

the benefit of a higher octane rating is not more power in and of itself, but that it allows a more advanced timing and therefore higher fuel compression at point of ignition to be dialled in to the map than would otherwise be safe (the result of doing this without sufficient octane is detonation)

so yes, using higher octane fuel can enable you to get more power out of your engine provided you tune it to take advantage of the bigger safety net provided by the higher octane fuel.

as has been stated already, some ECU's self-tune to run optimally on the octane level detected, and any ECu that does this will of course do it much better after a reset.

Exactly! Higher octane does not = power. However it does give your engine the extra safety margin by the more 'efficient burn' higher octane fuels characterises. Consequently this extra 'safety margin' allows you to run a more aggressive timing map which gives you the extra power. Hence your ecu would need to be remapped to take advantage of the higher octane.

I also used to think that Optimax is a fuel of choice for performance cars with all these hype and marketing burning a hole in our brains telling us so, and have been using it since its release. Until recently I had my ITR turbo remapped showing signs of detonation with Optimax and fine with other SUL fuel.... Go figure. I have never touched Optimax ever since. It probably does indeed clean the car as they claim from all the additives they add to it but for performance wise I would not touch it with a barge pole.... Other highly modified turbo vehicles have also experienced same/similar issues with Optimax. Having said that, oem or slightly modified vehicles are highly unlikely to experience detonation on Optimax as oem ecus have huge tolerances and much greater safety margin built-in. Its only when you run an aftermarket ecu and try to squeeze as much HP out of the car as possible that you will see the difference in the quality of fuel. Tesco 99 is what all my cars run now (my butt dyno tells me it fantastic!) as they run like champs :D My next dyno seesion will be able to tell me just how much further we can push on this fuel in comparison to other 97 and above octane fuels that are available to us on our high streets. IF only race gas (110+ octane) is just as cheap and widely available here as it is in the US we would all be running it on our crazy high HP cars!! :twisted:

Steven.

[ctrlaltdelboy]

as a matter of interest, when I had my highly modded Skyline (details here) (http://tinyurl.com/6z3wb) running 1.5bar of boost though an RB25DET motor producing 400BHP, the most monitored gauge on my dash was the knock sensor - clearly I did not relish the kaboom under the bonnet that the real threat of detonation would cause!

now, I tried several different brands of SUL with various different minimum, average and peak levels of knock resulting (with a bottle of OB always on hand to sort out a bad tankful).

the fuel which gave the lowest knock figures of all that I tried was Esso super - much better than Optimax (from a busy forecourt).

I can't say whether the reduction in knock from Esso SUL is down to a genuinely higher octane or just the presence of some knock inhibiting additives, but whichever it is, the result is being able to run an aggresively advanced timing map with minimal risk of detonation = more power.

[Rob_Fenn]

Nice wheels on that Skyline

[sportyking]

I can safely say that after a 220mile 2.5hour test last night I wont be bothering with Tesco 99 anymore. Will give this Esso SUL a try next but Optimax so far gives smoothest running, best performance and mpg, probably more to do with it having this in the tank when it was setup on the dyno.

[modarr]

I have heard that a quick ECU reset is to pull the 7.5A fuse marked "clock" in the fuse box and leave it out for 15 seconds or so.

That's the nugget I needed.

Thanks

As for the ECU being set for 95RON my esteemed neighbour, the 'Great Knower of All Things', assures me that *** cars have ECU's designed for 100RON fuel andthat re-setting the ECU will allow it to start with this map first.

Robfenn,

Where do you get Tesco99, I assume you're near the Bexley area?

Mo

[sportyking]

Robfenn,

Where do you get Tesco99, I assume you're near the Bexley area?


If it's any use the Tesco between Sutton and Cheam does it.

[MattS]

Mo,

I don't believe your neighbour. *** spec cars may well have the ECU set for 100RON as a default, but this 'setting' will be different for the export market that the car's intended for. That's because anything over 95RON is hard to come by in lots of places. Most modern cars will cope will fuel from91-98RON, but I bet the default spec for UK cars is 95RON, unless the handbook says use something else.

My NSX handbook says "your Honda is designed to operate on PUL with a RON of 95 or higher......If unable to get this, use normal unleaded regular petrol (ie 91RON), but you may notice a decrease in power as a result".

To me, this implies that the default is 95RON, but the ECU will learn to use a higher RON if needed. This makes sense from an engine safety perspective.

I guess the only way to find out is if you pull that fuse!

[NSXGB]

Most modern cars will cope will fuel from91-98RON


...a mate of mine has just bought a brand new Golf GTi, it seems to his displeasure that it will ONLY run on SUL of 98 RON. Coughs and splutters like a pig on Regular gas.

Would have been nice if the sales person had brought this to his attention.

[markc]

Matt,

The ECU reset is probably more for use after you've had knock detection occur (real or false thru a faulty knock sensor) and therefore your engine performance limited by excessively retarded ignition.

I suggest it is generally useful to know how to do this so that you can start again from a known baseline if you do have any problems that could be ECU related.

I think Darren's correct, you really need to wade through that thread on the gtr forum if you want to know why it's far from as simple as the RON, MON or even PON Octane rating. :?

Despite some of the comments here Shell Opitmax has a generally good rep as the best premium fuel and uses "safe" additives to gain it's advantage.

For example I remember a similar thread on a Supra forum where another petrochemist (like the guy in the gtr formum thread) advised in great detail why you shouldn't use BP SUL because it used Benzene as one of the additives to delay detonation. Apparently Benzene has disastrous effects on all engine oils so if it manages to get past your piston rings etc and into the oil it will break down the oil and you could end up severely damaging your engine.

All the premium fuels start out as basic 95 RON UL and in fact most (all?) stations share the same basic fuel from the same source, so the stuff going into the tanks at a Tesco station could well be from the same source as a BP, Texaco, Esso or indeed Shell one. The additives for their "special brews" are added on the forecourt.

I have no idea what additives go into Tesco 99RON but it could be Benzene which would not be good! :(

Cheers

Mark

[mcibuk]

Been out of the loop for a while and thought i'd catch up with things - this was the first topic i read and i really wish i hadn't - all very interesting for a while but the amount of discussion to extract a few milliseconds better performance just ain't worth it. :roll:
No offence intended to anyone :)

[markc]

Big article discussing this issue in the new January edition of EVO.

Conclusion is that the 98/99 stuff does indeed make more power and torque and their testers could feel differences in smoothness and drivability.

Read and enjoy...

[Amsoil]

Apparently Benzene has disastrous effects on all engine oils so if it manages to get past your piston rings etc and into the oil it will break down the oil and you could end up severely damaging your engine.



I think you will find that it wont touch the oil I sell, unlike the mineral / semi synthetics most peolpe use