My last track day included me doing a rush to the local garage with an empty jerry can to get some more fuel. I normally use 95 Ron (normal?) but this
time grabbed some higher stuff, 98?
It did feel a little faster, I think. Mainly at the higher end, it just sounded a little more eager but either way has got me thinking.
On my next track day I will be going all high octane, some garages do 99 or more "super dooper" stuff. What is sensible to run? Can I put
high in and octane boost and have 110RON or something stupid? That would be approx 15% more bang, right?!?
Engine is 1.6 20V 4age with Omex 710 including Lamber sensor so I would like to think the ECU will adjust something to take advantage of the extra
saucy juice.
Thoughts?
to really take advantage you would have to up the CR.
The only parameter that an ECU can adjust to take advantage of higher octane fuel is ignition timing, and then only if the engine is detonation
limited. To do this it would need a knock sensor.
An oxygen sensor simply helps to maintain the correct air/fuel ratio, and this shouldn't be impacted by octane to any significant degree.
In short, if you don't have a detonation problem running on 95, it's unlikely that bunging 99 in is going to help much. It will lighten
your wallet giving a small increase in power/weight though 
[Edited on 13/5/13 by MikeRJ]
It will only really benefit you when you go forced induction, I like optimax anyway as it keeps the engine nice and clean and I feel my TIn top is
smoother with it although the book says 95 Ron is fine.
My little car has to have optimax as I stuck the turbo on a stock engine.
i have always used optimax on any of my race cars as i think they run better.
If you decided to run a higher octane fuel ALL the time it would be worth getting the car mapped on that fuel to take advantage of the higher octane
rating.
Otherwise just use what the car was mapped on, Although having said that mine was mapped on standard un-leaded but when i did drop the occasional
optimax in it it did feel a bit 'cleaner' on the throttle.
Cleaner reving is a good description.
I dnot know if I have a knock sensor or if the omex knows what to do with it.
Cheers for the lamber sensor education. I did know ir was air/fuel, just being silly . . .
Worth noting that the higher the octane the harder it is to light off and the lower the burn rate so without sufficent compression ratio and
appropriate combustion chamber shape you will find that it actually makes less power!
NA engines are actually very octane sensitive as it's all about getting the optimum amount of gas generation done in the cycle time available.
Some trick fuels are oxygenated so you will see gains here but generally speaking pump fuel is pump fuel and burn rates are similar. Going 95 to 98 on
a good 4V chamber engine with a nice amount of compression will generally move MBT by 1.5 - 2 degrees which can be worth useful power.
Your Omex has no ability to adjust for Octane rating and if your lambda is narrowband then it won't be using this past very low throttle.
With regards octane boosters etc. anything you buy in Halfords is pointless. You want Toluene or a very similar aromatic hydrocarbon really, this will
allow you to brew fuels to suit your application (as we do with the F1 Turbos) but be careful it's nasty stuff and if it gets to the point where
you're running pre heaters in the fuel tanks to get the burn rate up you've probably gone too far
higher octane fuel basically allows the compression to be higher before the fuel self combusts (without the use of the spark plug) if you have a
really high compression engine and use 95 fuel then it will self combust under the pressure and start putting rods through the block and cracking
liners.
higher octane fuel also 'explodes' quicker when ignited, which will allow quicker revving (better acceleration).
i work for a race team and we use high octane fuels in some of our cars.
if i was you i would your car on 99 octane (tesco Momentum) and octane boost it to between 102 and 105 when on track and the rest of the time (road
use) just run it on 99 octane.
octane boosters are okay but boosting your octane level with it to 105 for example isn't the same as using 105 octane fuel. 105 octane fuel has
been special developed.
hope this helps
Other than the cleaning agents in the "better fuels" the only benefit of them is if the engine is mapped for them.
RON has nothing to do with the calorific content of the fuel, as mentioned above, its only an indication of its resistance to knock.
I had a similar argument with a guy at work, he thinks 98 RON fuel must give more power than using 95 RON.
quote:
Originally posted by Dooey99
higher octane fuel also 'explodes' quicker when ignited, which will allow quicker revving (better acceleration).
The blacktop has a ratio of 11:1 anyway and being Jap import only may be designed to run on 99+.
Interesting reading and conflicting advice at times. Especially on something quite basic. By basic I mean a decision we all take when filling our cars
up.
You need to be around 12.2+:1 to really see any real benefit on 100+ octane with the rod ratio, bore size and cam profile you are running (assuming
standard cams?). JDM "Plus" fuel was 100 octane with a high aromatic hydrocarbon content due mainly to their persuasion for boost (lots of
boost) The 4AGE is actually a really nice engine though, the earlier 16V were for all intense and purpose a mass production optimised BDA, as such
the combustion chamber is nice and small so flame front propogation speed becomes less of an issue.
The bottom line here is that without optimising the engine calibration to the fuel you are using AND ensuring that the fuel used is appropriate in
terms of burn rate for the chamber size and operating regime you're unlikely to see any real difference in the load on the piston crown i.e power
produced. If you aren't able to quantify your ignition timing is essentially at MBT for most operating loads (obviously outside of any KLSA
areas) on your current calibration then you're better off investing time in optimising this for lowest common denominator fuel and working from
there first..... and that's before you start to question what the crank accuracy actually is on an 20 year old ECU design at 8000RPM and as such
if you can actually achieve consistent MBT timing in the first place.
It's not rocket science but it's still combustion in a pipe and there's quite a lot to that For the most part if you stick 98 octane
Super/Fancy branded unleaded in a road car on a stock ECU or MBT/below MBT calibrated aftermarket ECU it's going to be so far clear of the knock
threshold it definitely won't fail from det... which is nice to know.
I consistently get better mpg using 97 octane fuel than 95 octane, typically 1.5- 2mpg in my 3.0L V6 Peugeot
[Edited on 14/5/13 by spiderman]
[Edited on 14/5/13 by spiderman]
quote:
Originally posted by Dooey99
higher octane fuel basically allows the compression to be higher before the fuel self combusts (without the use of the spark plug) if you have a really high compression engine and use 95 fuel then it will self combust under the pressure and start putting rods through the block and cracking liners.