Switching fuels

[djb160]

Ummm...Try not to yell at me just coz Im a dunce but. I've been running my car on 91 up untill today when I told my brother this and he gave me a funny look. So I did some searching on here and have come to some simple conclusions.

1. I probably shouldn't be using 91, either 95 or 98.
2. I need to reset my ECU by unhooking my battery for say 10 mins. What are the implications of this, I'm mostly worried about my tip.
3. Is there an overwhelming reason to use 98 instead of 95. My car is stock except for replacemnt panel filter. I gathered that 98's more for those who run higher boost.
4. Would it be better to near empty the tank and completely fill it or fill it only some and near empty it a few times.
5. Would 91 explain my really pooey MPG?/duh

[Kieran]

1. I probably shouldn't be using 91, either 95 or 98.


Yes. These cars were originally designed for 100RON fuel, so the closer to that, the better.


2. I need to reset my ECU by unhooking my battery for say 10 mins. What are the implications of this, I'm mostly worried about my tip.

Both your engine ECU and your gearbox ECU will default to a standard map, and it'll take about 300kms for them to 'learn' all the characteristics of your gearbox and engine - during this time your car may idle slightly rough and your gearchanges may be a tad harsh whilst your ECUs adjust. It's not harmful.



3. Is there an overwhelming reason to use 98 instead of 95. My car is stock except for replacemnt panel filter. I gathered that 98's more for those who run higher boost.

The reason why you need to run as high octane as poss is to ward off detonation. Now, the VR-4's ECU can compensate for poor fuel, and it does this by 'fuel dumping'... That is to say, it runs mega-rich on boost to suppress detonation (petrol is a suprisingly effective heat soak!), and it can also retard the ignition timing. Neither of these failsafes are good for fuel economy or power.


4. Would it be better to near empty the tank and completely fill it or fill it only some and near empty it a few times.

Your choice. If it were me, I'd get the low octane stuff out ASAP... so your second choice is perhaps the best.



5. Would 91 explain my really pooey MPG?/duh

Indeed it probably would, depending on your MPG... What are you getting?

[Subaru ETA]

when i ran my str on 91 coz i was in a hick town on the east cape and thats all they had i got about 100ks less to the tank plus i had pussy hondas overtaking me!

as kieran said, these cars are designed for 100RON fuel. in japan thats normal.

so yeah its all been said.... 91 is the DEVIL!

[djb160]

So is it trueish about 98 being more for tuned cars? Assuming I can even find someone who has it? My brothers SiR-T cant take me but I was only slowly pulling away, should I have smoked him? Chch-Motueka is about 450km and I couldn't quite make it without putting an extra $20.

[Rossco Type-S]

So is it trueish about 98 being more for tuned cars? Assuming I can even find someone who has it? My brothers SiR-T cant take me but I was only slowly pulling away, should I have smoked him? Chch-Motueka is about 450km and I couldn't quite make it without putting an extra $20.

No 98 isn't for tuned cars, its for cars designed to run on it. In the case of japanese cars this is most larger and performace cars.

Open road you should have easily got 450Km without refuelling. Fuel gauges are deceptive though you might have had quite a bit left.

From a standing start you should absolutely smash a SiR-T.

[djb160]

My next question is when would be best to reset my ECU?

[Rossco Type-S]

My next question is when would be best to reset my ECU?

Once you have put a few tanks of 95/98 through it and all the 91 is out of the system.

[djb160]

Thought so. Thank you everyone.

[SirVr4]

funny hearing all this cause i run my car on 91 when i give it you can feel its a lil bit slug but still gives me the economy around 420 and thats with a quater left in the tank i've never taking my car lower than that not even sure how low the needle goes before the light comes on lol

[SirVr4]

in saying that after reading all this i 2 am going to change to 95 or 98

[djb160]

Go for gull 98, that way you can get 10 cents off it from countdown etc. They only seem to operate in auckland so I still have to pay $1.5X from BP.

[djb160]

Do I have to watch out for electricution(sp) when taking off the terminals.

[Rossco Type-S]

Do I have to watch out for electricution(sp) when taking off the terminals.

Not really enough voltage to do damage. The high ampage would give a kick. In any event don't touch both terminals at the same time.

When disconecting the battery for a ECU reset you only disconect one terminal. And I always forget which one. Someone else help.

[bradc]

I always take off the positive one

[Subaru ETA]

you are supposed to take the negative terminal. when you take a battery out you take negative off then the pos. then reconnect with pos then neg. it protects the ecu etc

[djb160]

Awesome thanks eta