05 To 07 Manual Statement

[mshowells]

Hi all, 07 hawkeye manual states that the wrx can run on 95 octane and its only the STi which has to have high octane, is this a wise move as i have put 99 octane in her since purchase 4 weeks ago now, just thinking is it ok to use the normal unleaded or will it damage my new toy, i dont thrash the car {much} so its not driven hard ALL the time. Many thanks for any help if possible

[tomwrx08]

my hawkeye wrx says the same and the first time i ran it on normal unleaded

it was fine to be honest but next tank was vpower and noticed it seemed to perform better,

[st3ph3n]

I think the old 2 litre (05 and before) said 97 min, but I'm not quite sure.

[scouk]

My 01 UK Bug WRX says 97 on the filler cap..

[Alastair]

I was advised before buying my 07sti buy an unnamed subaru garage I could use unleaded 95 in an sti, but on arriving at the first garage after buying I opened the filler cap and it states min 97ron. So v power only for me..

[rig-pig]

all the scoobs before the hawkeye state you must use super as a min

[Chris180883]

Stick with the good stuff

[brianm]

I believe by law all petrol cars sold in the UK must be able to run on 95ron fuel. SO you wont damage it on 95; try a couple tanks of both and see if you see a difference in feel, pick up and economy then decide.

[mystery machine]

A Hawkeye WRX will run on reg 95 RON as per the manual - did so with mine for a while before switching to V-Power, which I stuck with because of the noticeable improvement in performance/smoothness.

[mystery machine]

P.S. Welcome to the forum!

[geosub]

For a extra few pence a litre stick with the good stuff. Better safe than sorry mate

[andrew_forrest]

I monitor exactly what happens inside the ECU when these cars are run on lower octane fuel.

Combustion knock is detected, the ECU retards the ignition timing and adds fuel to slow down the rate of combustion, this reduces power and increases fuel consumption. These revised low octane settings are then stored in memory tables within the ECU, these tables have separate cells depending on load and RPM. As the combustion takes place later in the cycle, this also has the side effect of increasing the exhaust gas temperature which is not good for the turbo.

If you drive at full load for extended periods then the ECU may also reduce the boost pressure, depending on how hot things become, this obviously loses even more power.

When you refill with Vpower or similar, the ECU very gradually re advances the ignition timing, optimises the fuel and allows full boost. The memory tables are then repopulated with the high octane settings again.

Contrary to popular belief, resetting the ECU will not restore high octane settings, it defaults to low octane initially and learns upwards(for engine safety)

If you get caught out and have to run 95 octane then my advice is to keep in the low load/low rpm areas, that way the memory tables at high boost will not be 'spoiled' and then as soon as you put decent fuel back in, full performance will be available straight away.

In a nutshell, yes they will run on 95 RON but are so much more efficient on 99 RON that it probably pays for itself.

Andy

Edited September 9, 2010 by Andy.F

[russ b]

I monitor exactly what happens inside the ECU when these cars are run on lower octane fuel.

Combustion knock is detected, the ECU retards the ignition timing and adds fuel to slow down the rate of combustion, this reduces power and increases fuel consumption. These revised low octane settings are then stored in memory tables within the ECU, these tables have separate cells depending on load and RPM. As the combustion takes place later in the cycle, this also has the side effect of increasing the exhaust gas temperature which is not good for the turbo.

If you drive at full load for extended periods then the ECU may also reduce the boost pressure, depending on how hot things become, this obviously loses even more power.

When you refill with Vpower or similar, the ECU very gradually re advances the ignition timing, optimises the fuel and allows full boost. The memory tables are then repopulated with the high octane settings again.

Contrary to popular belief, resetting the ECU will not restore high octane settings, it defaults to low octane initially and learns upwards(for engine safety)

If you get caught out and have to run 95 octane then my advice is to keep in the low load/low rpm areas, that way the memory tables at high boost will not be 'spoiled' and then as soon as you put decent fuel back in, full performance will be available straight away.

In a nutshell, yes they will run on 95 RON but are so much more efficient on 99 RON that it probably pays for itself.

Andy

Is the above the case with a standard (other than prodrive b/box) MY06 2.5 WRX? It says 95 only on the fuel filler door & thats all Ive run it on for the last 4 years & 33K miles.

[mystery machine]

I monitor exactly what happens inside the ECU when these cars are run on lower octane fuel.

Combustion knock is detected, the ECU retards the ignition timing and adds fuel to slow down the rate of combustion, this reduces power and increases fuel consumption. These revised low octane settings are then stored in memory tables within the ECU, these tables have separate cells depending on load and RPM. As the combustion takes place later in the cycle, this also has the side effect of increasing the exhaust gas temperature which is not good for the turbo.

If you drive at full load for extended periods then the ECU may also reduce the boost pressure, depending on how hot things become, this obviously loses even more power.

When you refill with Vpower or similar, the ECU very gradually re advances the ignition timing, optimises the fuel and allows full boost. The memory tables are then repopulated with the high octane settings again.

Contrary to popular belief, resetting the ECU will not restore high octane settings, it defaults to low octane initially and learns upwards(for engine safety)

If you get caught out and have to run 95 octane then my advice is to keep in the low load/low rpm areas, that way the memory tables at high boost will not be 'spoiled' and then as soon as you put decent fuel back in, full performance will be available straight away.

In a nutshell, yes they will run on 95 RON but are so much more efficient on 99 RON that it probably pays for itself.

Andy

Interesting post

Not meaning to hijack the guy's thread, but seeing as we're talking ECUs...

Andy - when you remap an ECU, do you have enough control that you can 'reshape' the engine's torque curve?

i.e. this graph shows traces for a standard Hawk STI (dotted red line) and a PPP Hawk STI (solid red line):

Would you be able to program the ECU to give a torque curve that approximated the green line? (assuming the exhaust had been derestricted and the fuel pump had been uprated). Or are you constrained by the mechanical response of the turbo, etc?

I'd be very interested to know because, while the above green-line curve offers nothing like the peak torque of the PPP (or similar remappings), it would yield similar peak power and a IMO a more useable response for my driving style, which is more about accelerating smoothly out of bends than ultimate straight-line acceleration.

Perhaps I'm being naive and idealistic, but I might as well ask...

Thanks.

Edited September 9, 2010 by Mystery Machine

[andrew_forrest]

Russ, I rarely see a completely standard car so without checking your car, I cant say for sure. It would be easy enough for you to time it from say 3000-6000 rpm in 3rd gear with 95 and then 99 octane. If performance is the same then the ECU is probably happy with the 95 in your car.

I can make the torque curve any shape you want, the limitations are only mechanical ie how quickly the turbo will spool and the maximum safe boost level. There are fewer limitations regards lower torque, the wastegate spring tension will however dictate minimum boost.

I have control over the boost target and wastegate duty in 3 x 64 point maps which have throttle position and RPM axis. I can also change the axis values so for example I can have boost/torque progressive with throttle position and/or rpm.

Basically the answer is yes, I can tailor the torque however you would like it. I have road-dyno data for std Sti, PPP and for many stages of modification (on your model/year) so it would be possible to overlay your new torque with any of those to verify the output throughout the rpm range.

cheers

Andy

[mystery machine]

That sounds great!

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