fuels and performance

Dave_Obsession · 22-07-2009, 01:14 PM

Just an observation I've picked up on whilst driving around.....

Whilst my engine is stock (ie runs on regular 91RON unleaded), I have usually been running on BP Ultimate......I guess the videos on their site about the cleaning stuff in the petrol got to me....I want to keep my engine clean inside!!

Anyways, on the 98RON stuff, when accelerating, I can really feel the difference at 2500rpm when the engine just seems to pick up a lot in the higher rev band, right through to 4000rpm (is this when the stock cam seems to die out?).

Just filled it right up last night with the 91RON regular stuff, and the kick at 2500rpm is no longer there, it's more like a constant acceleration with no real noticable improvement at any level......

Does this mean that the car runs better and faster on the 98RON, even if everything is stock??

I don't know all the technical stuff to do with cams, timing and all that stuff......How would some of you more learned guys explain this in laymans terms???

blueoval · 22-07-2009, 01:41 PM

Hey Dave,

I believe that when you put the better fuels in, the engine notices it and the ecu advances the timing a little to compensate for the better grade fuel.

i.e. Higher RON fuel, the more power you'll get, but only up to the limit of your engine mods.

Thats the way I see it, but Im sure someone here will explain it better than me.

Sox · 22-07-2009, 01:53 PM

Quote:

Originally Posted by blueoval

Hey Dave,

I believe that when you put the better fuels in, the engine notices it and the ecu advances the timing a little to compensate for the better grade fuel.

i.e. Higher RON fuel, the more power you'll get, but only up to the limit of your engine mods.

Thats the way I see it, but Im sure someone here will explain it better than me.

That's pretty much what happens in basic terms, yes.
The ECU follows a timing map, however when it registers detonation via the knock sensor it will retard the timing by a certain amount (4deg I believe) until the detonations stops. After a very short time has passed (literally seconds), it will read direct from the map again.

That's also why, as you already mentioned, performance will only increase up to a certain point.
I believe that pont is actually 95 with the AU Falcons.
IME, 98 fuels have no performance advantage over 95 on AU's with mostly standard and even mildly modified engines.
IME 91 has caused very minor detonation and as a consequence slight retardation of timing under heavy load. Particularly in hot weather and when the throttle is snapped open quickly.

It's only once you have a cam and increased compression that 98 is an advantage.

Mr Hardware · 22-07-2009, 03:07 PM

orly sox
95 hey
that's excellent information.

Dave_Obsession · 23-07-2009, 01:02 AM

Thanks Sox, great info there!

will have to run this tank of 91 down to empty, then fill her up with 95 and see what happens!

Am I right about the stock cam running out of guts around the 4000rpm mark?

Sox · 23-07-2009, 08:20 AM

Quote:

Originally Posted by dave93761

Thanks Sox, great info there!

will have to run this tank of 91 down to empty, then fill her up with 95 and see what happens!

Am I right about the stock cam running out of guts around the 4000rpm mark?

I haven't noticed any significant power losses, however as I mentioned I have detected some detonation so obviously some power will be lost.
4000rpm is close to where the inlet manifiold changes from long to short runners, so the timing map is also changing at that point (actually 3800rpm).
I'm not sure if the ignition timing is increased or decreased at the 3800rpm.
If it's increased it stands to reason that you might experience some power loss if the advance is too much for the 91 fuel.

BTW, when this detonation occurs, you should be able to hear a slight rattling noise for a split second (until the ECU has pullled our some timing).
If you don't hear anything, then it's possible nothing is happening at all and you might be imagining it.

mik · 23-07-2009, 09:39 PM

engine compressions have a bareing on the fuel type for each engine. low compression engines tolerate cheaper fuels(lower octane) as a rule, the higher the cylander pressure the more the fuel wants to burn faster and explode in the cylander, uncontrolled burning ,exploding fuels becomes ie pinking (or pinging) sending shockwaves through the rotating mass shortening the life of your engine, pistons ,rods,crank bearings etc hence the need for slower burning fuels (higher octane) for higher compression performance engines.

Dave_Obsession · 24-07-2009, 12:07 AM

So....you're saying my engine will actually last longer as well by using higher octane fuel???

Dave_Obsession · 25-07-2009, 07:38 AM

how does 95RON ethanol fuel fit into this???

Sox · 25-07-2009, 12:30 PM

Quote:

Originally Posted by dave93761

So....you're saying my engine will actually last longer as well by using higher octane fuel???

Well, detonation isn't a good thing, so yes.

Quote:

how does 95RON ethanol fuel fit into this???

Much the same as normal 95, except that it won't go quite as far for the same amount.
But it's a lot cheaper, so the worse economy is offset.

I can't say I'm sure of the long term effects, but I doubt it would be a problem.

BoostedT · 25-07-2009, 09:50 PM

Runs BP Ultimate and only that .. AU's run better on Higher RON Fuel

Dave_Obsession · 06-08-2009, 02:52 AM

**UPDATE**

Last week - ran my tank almost bone dry and filled up on BP 95RON premium unleaded......the 'kick' in acceleration at around 2500rpm was back, everything went nicely......went for a drive out to Yarra Glen over the weekend, felt pretty responsive!

Tonight, got home about 12:30 and wasn't tired, so decided to go for a drive around the suburbs to run my tank dry before going back to filling up with BP Utimate (98RON) to see if there was any noticeable difference.......managed to get pulled over by a cop who reckoned one of my headlights was too bright, so I showed him high beam vs low beam and he couldn't say anything..............ANYWAYS...

There was definately a difference going fron 95 to 98RON petrol, even the shortish drive from the BP servo to home, I pushed the car and the 'kick' that I could feel is even more pronounced with the 98RON fuel.

Have generally been running on it as of late, but definately going to stick to it from now on - will have to give Shell V-Power and the Mobil a go as well, but BP Ultimate is just plain good.

Might also try out the 98RON ethanol fuel you can get from United servos....see what the difference is!!!

blueoval · 06-08-2009, 10:12 AM

this is a good little comparison Dave. Im keen to see what you find.

Generally there isnt a massive difference on an NA untuned car between 95 & 98 fuels. But if you can notice a difference, then that is something.

Running on the more cleaner refined fuels should give you better economy also.

Dave_Obsession · 06-08-2009, 10:25 AM

No worries mate, yeah I'm not saying the difference from 95-98RON was huge, but it was definately there - it felt that little bit more responsive, and the engine just revved out that little bit easier!

Stattic · 06-08-2009, 01:31 PM

v-power is miles better than vortex but id still give bp ultimate the edge