hi guys. just picked up my new car this morning. a my99 impreza. standard car bar a scooby sport back box. was never used on the track. after picking the car up i headed over to AVA who have a nice rolling road. wanted to get the car checked out to make sure everything was working. BIG PROBLEM! at 5000rpm and up the car is detonating quite badly. it is running 1 bar of boost which is not dropping of. couldnt run the car past 5000rpm because of the detonating. car was filled up with optimax but had about a 1/4 tank of unleaded in it as well. the guys there were telling me that they had another my99 in that morning that at 5000rpm the boost starting falling of and there was no detonating. this car was also running 1 bar boost. all conditions for the test were the same. hope some of you guys can help me out.
thanks for your time
iain macleod

 

You should use high octane unleaded fuel, not Optimax.

Use a tank or two of fuel, go back there and check if it still dets at 5000. I bet it wont.

 

Claudius Optimax is the highest octane fuel avalable in the UK,
its rated at 98.2 where Super unleaded is rated at 97.

Andy

 

iain, try a couple of tanks with optimax and see if it clears out the old fuel, just a thought. Also does the check engine light flash on when it detonates?

 

If the ECU sees detonation it should retard, add fuel and then drop the duty to zero to drop the boost to about 8 PSI.

Your MAF sensor, an injector or the knock sensor could be faulty for example. I'll log it for you. Whatever, we need to get to the bottom of it before mapping as I said in the email.

Alternatively it could have been modified already and that is causing the problem and not allowing the usual solution - the most you can expect even after modifying is 1 bar at 6000 RPM on the standard turbo, but standard boost is considerably less.

 

thanks for the advice guys. i am mega p1ssed off with the whole situ. just hope its something simple. the car has still got 22 months of the warranty left so i should maybe take it to a garage for them to look at it. a few friends told me not to go for the impreza, they are now saying "told you so". hope i can prove them wrong.
thanks guys
iain

 

Please enlighten us as to why your friends think the Subaru is a bad choice

What sort of cooling fan did AVA use on your car when on the rollers? Front facing or over the IC.

What were the air temps (post IC) the car was seeing?

Did you hear the det?...on open road and rolling road.

Just a couple of ideas......

 

Just need to clarify a few things here

1. Is your car a UK turbo or Jap Import as you havnt stated anywhere?

2. Have you tried doing an ECU reset yet?

3. Under what circumstances were you getting det?

Ta

Tony

 

Optimax is "enhanced 95 RON" and depending on when your petrol station gets it, a lot of it will have evaporated, the octane rating gone down. It also escapes through the filter in the tank.

You do as you please.

All I'm saying is TRY 97 or 98 RON instead of Optimax and see if you get det, I didnt say not to use Optimax if you like it.

 

Cladius is correct in saying that Optimax is a *modified 95 RON* fuel and the rating will go down through time, but 95 and 97 fuel will do the same over a period of time.

As ever, best to get fuel as fresh as possible to minimse any problems you may have, although i wouldn't like to be running my map *on the limit* all the time.

A

 

AlanG

would you agree that it could be possible that Optimax degrades more rapidly and that trying 97 RON and checking for det again might be worth a try?

 

Optimax is based on super unleaded.

 

I've heard of a few folks commenting on fuel degradation over a period of time, Optimax being more susceptible to it compared to pukka 97 RON.

However, as said before, they will all do it to an extent.

I'm no expert on fuels but would be interested to hear from those in the industry for their thoughts on pukka developed 97 RON petrol and modified fuels.

Showing my age a bit now, but i remember, back in the eighties i think, when Shell brought out their super dooper cleaner fuel ( can't remember what they called it) and went t*ts up when certain models of cars burnt valves out.... took it off the market with the bad publicity....go figure for modified fuels.

In Iain's case, the previous suggestions need answering, but also another thing to ask... is the knock sensor working correctly?

If it ain't, then the ECU has no way of responding to any detonation occuring.

Alan

 

hi guys. to answer the questions, well, its a uk car. the cooling for the car while on the rollers was front facing and over the ic. i did here it while it was on the rollers and it was quite bad. have'nt noticed it on the road as i have not taken it near 5000rpm. thought there was a slight det around 2000rpm when i was out last night but not that sure. maybe im just hearing things. a sub mechanic from awd in perth was telling me that the injectors sometimes caused this fault.
would be gratefull for any help you can give me.
iain

 

Optimax reply from Shell :

http://www.scoobynet.co.uk/bbs/threa...hreadID=120509

 

Thanks chrisp

So basically, get your fuel from high turnover stations. Sorted.

A

 

Thanks crisp! u r getting old Alan...

 

I have been getting a few more green flashes than usual on my knocklink lately.I know greens mean **** all but they are out of character and seem to happen on gentle drives at 3500ish rpm.the only things changed on my car which might have caused this are firstly,1000miles ago,because I am not doing any track days just now and also do mostly short journeys,thought it would be a good idea to change oil to castrol magnatec to aid cold protection.secondly I swapped my straight through centre for a silenced one and inserted the centre cat to keep me going until the silenced one arrived.third I have changes to optimax.

I find it hard to believe it's the oil that has broken down after 1000miles(with under 20miles of the odd thrash).I also doubt it is the fact that a cat is back in the system,so I am going to run some super for a few tanks and see what happens.the car seemed to like optimax 2months ago,but now that the local station has had it for a while it might be out of date.

 

If you've decat'ed elsewhere, you'd be surpised at the amount of backpressure the centre introduces - this will translate to higher EGT's and can induce the additional noise you're seeing.

Mind you, I guess the suspect oil you're using wont help - after a particularly aggressive 2 days at the ring last year I knew my oil needed changing because of increased background noise seen on the knocklink....

Richard

 

The Magnatec could have easily broken down in 1,000 miles - change that ASAP! And agree with the mid-cat thing - once you (& the car!) are used to it not being there, it won't like it very much.

 

I thought it was OK to run a UK Turbo on 95RON or 97 and that it was only jap imports that need 97+ RON?

 

EU-import 'classics' have 'fill with super' on the filler, and UK ones say 'unleaded only' (I think - don't have a UK-bought model!).
Super is totally acceptable in Europe, whereas some people - and certainly magazines - here in the UK will heavily mark something down for needing SUL. So Subaru don't write it down.
In short, NUL is fine with the EU models, but your car will love you for feeding it SUL & reward you for it

 

dowser and nom,

I would never dream of going near a track or even a long journey with the magnatec oil,just thought that it would be more road friendly than mobil motorsport or motul for the many short trips I make,looked back it's only been in for 800miles with the odd short thrash probably totalling 20miles.I would not think it was the cat as this is happening on gentle drives usually on part throttle.pushing on and everything is fine with the normal back-ground flashes over 5000rpm.

will change the oil and get rid of the cat asap but I am going to try super for the next few tanks.the current fuel has been in the car for over 2weeks.

 

Nom,

I live in Ireland where SUL is nigh on impossible to get so I use 95RON NUL all the time. I don't thrash the car (apart from giving it the odd blast now and again). I use it for about approx 18 miles a day to go to and from work.

My car is a MY98 Turbo and had an english reg. plate before I registered it in Ireland so therefore I assume it was bought new somewhere in England in 1998, so that would make it a UK model??

Therefore am I looking for trouble by using NUL or will I just have reduced performance?

Having spoken to a few so called "Subaru experts" over here they reckon NUL is fine.

Your thoughts would be appreciated as I don't want to ruin my pride and joy!

Gavin G

 

Nom, to increase confusion ... super means nothing at all over here, you have Super 95 RON and Super 98 RON, sometimes called SuperPlus or other names - depending on brand. Fortunately, all pumps that I know of clearly state the octane number.

So the bottom line is NUL is acceptable (well, according to the filler caps anyway) both here and in the UK.

Gavin, you *should* be OK, and in the best of cases only have less performance. But why not bulk-buy some octane booster ?

 

Gavin

UK cars (old shape) were okay to run on 95RON but to get the benefit when changing to 97RON, an ECU reset was advised to allow the map to re-learn itself for the fuel used.
The fuel filler cap states on the UK cars "super unleaded" but Europe has a different rating I believe to what we perceive as being super unleaded.

I ran my UK car (99) for over 2 years on normal 95 RON unleaded with no problems even though up to that point i ran 1.3 bar boost along with a few mods.

At the time my car could have had more power if it was mapped for super unleaded but because i'm a tight scots git and it was a daily driver, i opted to run it on ordinary unleaded and forsake a few BHP.


Wouldn't run on ordinary unleaded now though....

Alan

 

Alan

The only mods on my car are a K&N Filter and Magnex back box. It's not a case of me being tight, its just that its virtually impossible to get SUL over here! I would buy it if I could.

I know my car would run better on SUL but as long as I know I'm not gonna cause any engine damage then I will keep running on NUL.

Cheers,

Gavin G

 

dont know if this helps but ive read if u get the ecu reset by an official subaru mechanic then fill up with super unleaded or optimax, give it a caning etc, the ecu will remember the octane rating and time ur engin to it. but as far as i know. it shudnt really affect a uk car normal unleaded :/ ........... im new to the game so i may be wrong.

 

The ECU reset isn't neccesary - the car will adjust over time. MY01+ immediately, 99/00 a couple of tanks, not sure before that. Or you can do the reset yourself by disconnecting the battery overnight (and other more complicated but quicker methods ). And no caning is needed - just drive normally!

 

Nodiggidy

No need to go to Subaru for a reset.

Go to www.mrtrally.com and click on "MRT performance" (topright), then click on "ECU's info" (left).
Click on "how to reset your ECU"

Alan