neveryoumind

Is there any point in me running Optimax ?(my99, 60k)
I did the PE rolling road a month or so ago, and their computer showed that there was no ignition retardation by the ecu. So will I benefit from a higher RON? AIUI the calorific value of all RONs of petrol is the same, so what is the benefit?

JohnD

iTrader: (5)

That needs a bit of explanation? In BASIC terms the ignition advances as the revs rise and retards again as they drop! You cannot have one advance setting for all speeds/loads! Did P.E. explain exactly what they meant? The benefit is that the higher octane rating advances the knock point, so the ECU can allow more ignition advance and thus more power (up to a point, that is!) I would think that engines using an ECU with a set "map" (i.e. not self learning) would show little benefit.
JohnD


[This message has been edited by JohnD (edited 22 September 2001).]

chrisp

I always ran my UK on SUL and now I run my import on optimax. I am not a chemical engineer so I have no proof. My UK ran smooth and gave an ok(ish) 23mpg.

You probably wont notice a hige difference in an UK unless you have a PPP. I was told by my friendly neighbourhood subaru garage to always run it on SUL as it better for it. A lot has been said in the past about UKs and SUL and the result seems to be smoother running and increased mpg with higher octane fuel.

Its only about 4p litre more where I live, its not a huge amount £2 a tank full extra and you may get that back if it does a few extra mpg.

[This message has been edited by chrisp (edited 22 September 2001).]

nickwrx

i filled up with optimax on my 95 wrx and on the second tankful i did a ecu reset and it now pulls alot harder and the idle is smoother .
Go get some !

nick.

neveryoumind

Cheers JohnD, I knew that ignition was a dynamic thing, I just wasn't what the software was showing. Looks like PE's software was showing just whether the knock sensor was kicking anything in. He didn't explain it as there wasn't anything wrong.
I run on SUL anyway, and a pop over to ispypetrol.co.uk shows it's the cheapest SUL round here anyway

Time to give it a whirl.


Cheers all again

mark

JohnD

iTrader: (5)

Now I understand! Makes sense now.
Cheers Mark
JohnD

PS I assume yours is a UK car? If so, have you had any probs. over the 60k? I also have a 99my UK but with only 16k (owned from new) Cheers

[This message has been edited by JohnD (edited 23 September 2001).]

Scooby_Killer

Optimax, is better than super plus unleaded and also has a higher octane rating which is 98ron!! The Ecu will not make the engine retared with good fuel, only when the engine gets hot!!

neveryoumind

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:<HR>Originally posted by JohnD:
<B>Now I understand! Makes sense now.
Cheers Mark
JohnD

PS I assume yours is a UK car? If so, have you had any probs. over the 60k? I also have a 99my UK but with only 16k (owned from new) Cheers

[/quote]

Yes it is a MY99 UK (Jan), and I'm the second owner after I bought it in May at 57K (ouch, never found out about 60K service bill until after I bought it)
I spoke to the garage that serviced it over the phone, and they said that it had done a few track days, and the only major thing done was a replacement turbo at 50K (under warranty).
The only problem I have are brakes that bind for a few seconds after I've been driving enthusiastically, and they also judder (but not fade) when they get hot. It's not that bad, but I'm going to get it looked at next service - I mentioned it last time and they fitted new rear pads.
But there's no problem with engine, gearbox, rust etc etc etc

Mark

Pete_UK99

Does anyone know how long the ECU takes to adjust to higher grade fuel? Do you have to go through a whole tank full or does it adjust over a few miles driving?

neveryoumind

According to other posts Yesterdy it takes 30 miles ish on a 99, as there's a faster learning ECU on MY99-00 compared to previous years.

Jacko

Cutting out all of the waffle above and to answer your question...YES YOU WILL SEE A BENEFIT!
Most modern day cars now run with varible knock calibrations/maps (albeit a predetermined window of opportunity) that retard and advance ignition according to what octane rated fuel you have just put in. This allows the vehicle to be sold across many other countries which use different RON rated fuels, with little or no calibration changes required by the manufacturer.
The more advance you can add the closer to MBT you can get. Unless you are thinking of running aircraft fuel or some hurrendous modifications, scoobs will always be knock limited due to an increase in power = higher temps = knock. However one can reduce temps by either of the following: higher octane rated fuel, more dense charge, better intercooling, waterspray, water injection, change the combustion chambers physical shape/charateristics etc, etc.
Jacko.

[This message has been edited by Jacko (edited 25 September 2001).]

[This message has been edited by Jacko (edited 25 September 2001).]