Tip for 2.0 owners suffering performance flatspots - qxman {p}
In November I noticed that my 2007 Impreza 2.0r (160ps model) was flat spotting a bit when accelerating from below 2000rpm. I took it to the dealer and they said that there were no fault codes, nothing wrong with the car, and so they just 'reset the ECU' and gave it back to me 10mins later. Strangely enough it seemed to drive better and I thought no more about it.
Over Christmas and New Year I noticed it flat spotting again and so called the dealer. Fortunately they had an engineer from Subaru UK visiting and they told me to take the car straight down to them so he could take a look at it.
He told me that there is a 'remap' available from Subaru for these cars to improve performance and responsiveness. He downloaded the new software into the ECU (took about 30mins). The flat spotting has completely gone and low speed torque and acceleration from below 2500rpm is much improved. Well worth the trouble of going to your dealer if you have one of these cars.
I imagine this would apply to all 2.0 160ps engines (as used in the Impreza, Legacy, Forester since late 2005 I think).
He also mentioned that being high compression engines (11:1) there is a power benefit from running higher octane petrol if you wish, the engine management is designed to take advantage of it.

Edited by Pugugly {P} on 08/01/2008 at 15:14

Tip for 2.0 owners suffering performance flatspots - Happy Blue!
Although running the 3.0 6-cyl Outback I too have noticed (for the first time) a significant difference in performance using high octane fuel (especially V-Power). When the price went over £1per litre I switched 95 Octane fuel. The car seemed fine, but not quite as sparky, and when I have run a couple of tanks of V-power through again, the responsiveness is improved. Not great difference to absolute speed or economy, just a sense of being quicker off the mark.
Tip for 2.0 owners suffering performance flatspots - Ruperts Trooper
Many modern cars have knock control sensors and ECU maps that adjust for fuel anywhere between 91 and 99 RON.
Tip for 2.0 owners suffering performance flatspots - Aprilia
Subaru's do tend to 'run off the knock sensor' more than most engines. The engine used in 2005-on 2.0 cars is the EJ204AVCS with 11.1:1 compression ratio. It will certainly not run well on 91 RON and just about runs OK on 95RON, but 97+RON would be preferable. In Japan the same engine (with different mapping) runs at 200bhp on high octane fuel.

The remap mentioned in the OP is colloquially known to Subaru UK as a 'hesitation remap' I believe. The factory mapping is rather conservative (they don't want knock-related engine damage during warranty) and so is set for a low knock threshold to take account of running on poor quality fuels that are encountered in many export regions. The result is that cars can feel like they are running with retarded ignition (because they are!) and this can give hesitancy in second and third gear acceleration and rather a 'flat' feel to throttle response.

The remap increases the knock threshold and changes the time constants for retard when knock has been detected. The upshot is that the engine learns a more advanced ignition setting and any part-throttle hesitancy goes away to give crisper acceleration.

Remapping can be done at your dealer via the EOBD port under the steering column (i.e. its a plug-and-play job with no dismantling required). Takes about 20 minutes to re-write the ECU.

I suspect that most dealers won't do this for you unless you complain.......
Tip for 2.0 owners suffering performance flatspots - jc2
Japan has no equivalent of the "Trade Description Act" on vehicles and some of the figures quoted in Japan are to say the least "imaginative".
Tip for 2.0 owners suffering performance flatspots - Aprilia
Japan has no equivalent of the "Trade Description Act" on vehicles and some of the
figures quoted in Japan are to say the least "imaginative".


Like most advanced economies, Japan has a whole raft of consumer protection legislation, including legislation protecting against fraudulent claims. Whilst some tuners may quote suspect figures (as they do the world over) I think its safe to say that the major Japanese car makers quote genuine figures.

Horsepower measurements by ALL car manufacturers follow standardised test methods according to either the SAE, DIN or JIS (Japanese), depending on the country. These standards define test parameters, ambient conditions, etc. Subaru nowadays typically quote to the DIN standard and the 200bhp mentioned for the JDM EJ204 is genuine. These engines have been privately imported to Australia and the US and do indeed give 200bhp. Its by no means an unrealistic output for a high-compression 2.0 engine with variable valve timing running on high octane fuel.
Tip for 2.0 owners suffering performance flatspots - OldSock
running on poor quality fuels that are encountered in many export regions.......


That'll be the UK, then :-)
Tip for 2.0 owners suffering performance flatspots - Aprilia
>> running on poor quality fuels that are encountered in many export regions.......
That'll be the UK then :-)

No. Despite the common belief in BR that the UK is the worst country in the world, our fuel is actually of a good standard. Subaru are popular in Aus and the Middle East and they do have problems with fuel quality there, especially in the more remote regions. Detonation (knocking) is also more of a problem when the charge temp is high (i.e. high ambient), so you can understand that they are conservative when it comes to engine mapping.
Tip for 2.0 owners suffering performance flatspots - willyb
Is there a remap available for the earlier 136hp(ish) version of the 2.0 litre as in the 2004 MY Legacy? Any performance gain would be welcome.
Tip for 2.0 owners suffering performance flatspots - Collos25
"No. Despite the common belief in BR that the UK is the worst country in the world, our fuel is actually of a good standard"

Why does my mpg drop when I come to the United Kingdom.
Tip for 2.0 owners suffering performance flatspots - nick
Heavier traffic?
Tip for 2.0 owners suffering performance flatspots - Collos25
I think there is a little more traffic in Germany.If you have ever driven in a City like Dresden then you would learn what traffic is.
Tip for 2.0 owners suffering performance flatspots - nick
It's those foreign kilometers that make the difference. :-)
Tip for 2.0 owners suffering performance flatspots - Aprilia
Is there a remap available for the earlier 136hp(ish) version of the 2.0 litre as
in the 2004 MY Legacy? Any performance gain would be welcome.

Nothing as far as I know. The older, simpler, 2.0 engine is quite a different beast. SOHC, lower compression and no AVCS.
Tip for 2.0 owners suffering performance flatspots - leftfield lenny

Whilst going back home from London last week, approaching the blackwall tunnel my 2.0R Impreza suddenly displayed this fault. More often than not 7/10 times it now manifests this fault. My car is the 2006 56 reg model. Although it has Subaru service history up to 60,000 miles (it has now done over 81,000 miles) no one has took it near to the main agents apart from I for a oil change and non relevent fault diognosis on a couple of occasions. I would have thought that during its service in the first five years a software patch would have been uploaded as per the service schedule. I may just speak to the service manager before I part with my hard earned cash on trying to cure this.

Tip for 2.0 owners suffering performance flatspots - hillman

Aprilia.

Do you know if Subaru have a patch to fix the irritating fault code that has appeared on my Outback '56 reg. 2.5 litre since new ? The green logo for Cruise control flashes and the amber engine alarm light up steady. That happens at irregular times, could be weeks, could be months apart. The alarm begins when I start the engine and continues until the engine is stopped. It does that on three journeys (could be the same day, could carry over to the next) and then not again for another period. I took the car in to the dealer many times and left it one at least three occasions. They were baffled. Finally a new technician said that it was a transient signal that occured on startup and then disappeared.

Tip for 2.0 owners suffering performance flatspots - leftfield lenny

I happened to be in my local Subaru dealer this week asking about a software update for my car to possibly cure this flatspot problem when my eye caught a high performance airflow filter that they had in the cabinet. I enquired about it because A. I normally fit one to my Subaru's anyway and B. On looking my car over after this all began with my brother, we found that the air filter that was on the car was the filfiest item I'd ever seen in my life, honestly! This filter couldn't have been changed since 2010. The technical engineer happened to be at the desk and informed me that most likely that dirty filter was the cause of all of my problems. I purchased and fitted the filter and I've not had a problem since, and the car hurtles through the rev range. I'm also now hoping to see a significant improvement in my fuel consumption as well. That cure for me may not work or be the cause for all, but in my case it did fix my problem.

Tip for 2.0 owners suffering performance flatspots - unthrottled

my eye caught a high performance airflow filter that they had in the cabinet

Which is precisely why it was so prominantly dispayed! How could a dirty air filter cause a flatspot?

Tip for 2.0 owners suffering performance flatspots - hillman

"How could a dirty air filter cause a flatspot?"

When I was working in the mining industry in Zambia I heard of a car that really struggled to run and cut out when the driver tried to accelerate. The enthusiasts - and there were many - had spent ages trying to fix the problem but to no avail. Then one man recognised that the air filter was one that had been 'borrowed' from the Mine. It was was a high efficiency type, originally intended for a diesel engine working in the open pit - a very dusty environment. When it was new and clean then a petrol engine would run quite happily with it, but after a while the dusty atmosphere blocked the filter enough to strangle the air flow, thus severely inhibiting the engine. The solution was to go into the local motor car spare parts shop and buy the correct maker's filter - problem solved.

Tip for 2.0 owners suffering performance flatspots - unthrottled

Yes, but that problem manifests itself any time you try to increase airflow through the choked filter. It's not going to only occur at a specific speed and then disappear at higher speeds! A flatspot is specific to a certain engine speed.

Tip for 2.0 owners suffering performance flatspots - leftfield lenny

I can't qoute to you exactly what the head tecnician at the dealers told me. He did explain to me why it happens at that particular revs in top gear. something to do with the variable valve set up (starting to gasp for air intake) if I remember correctly. Anyway, it cured my problem. As I said earlier, it may not be the cure for everbody's Subaru.

Tip for 2.0 owners suffering performance flatspots - Avant

Just to add that we haven't seen Aprilia since 2008. He was a sad loss as he was very knowledgeable about engineering. Fortunately we do still have some people on here with those skills, to whom as ever many thanks.

Tip for 2.0 owners suffering performance flatspots - Sprice

Indeed, Dr. Aprilia was a very valued member during the 'old BR' days and seemed especially knowledgable about Japanese brands IIRC.

Tip for 2.0 owners suffering performance flatspots - JosephNZ

Hi all,

Just though I'd chip in my 2 cents.

I have a 2004 Subaru Legacy 2.0R (enigine is a JDM EJ204 - 190HP model) that developed a similar problem. Horrible power down low and would then surge (sort of felt like a turbo - no power then power).

Turned out to be the air flow sensor, it was giving error codes so the Subaru people gave it a clean and so far so good. It drives like a completely diffirent car. Power everywhere :D

Something to consider if you are having similar issues.

Cheers,

Joe

Tip for 2.0 owners suffering performance flatspots - RicardoB

Slightly off message I guess, but I've noticed the main problem with Subarus, certainly near me, are the ones that seem to have rotten exhaust silencers and seem to be driven by ASBO seeking dealers/too old to be boy racers.

Shame really, because the original engineering designs would have deserved and expected a more sensible type of driver.

Bit like born again bikers really. Pain in the ear drums for everyone except them.

Tip for 2.0 owners suffering performance flatspots - RT

There are two types of Subaru owners - you're referring to the wrong sort and I can't disagree with you.

When the volume is at the acceptable level, there's something captivating about the off-beats of a Subaru exhaust.

Tip for 2.0 owners suffering performance flatspots - corax

When the volume is at the acceptable level, there's something captivating about the off-beats of a Subaru exhaust.

I agree. I can't stand the sound if the exhaust is an aftermarket job with no silencers - unrefined and chavvish. But a standard exhaust is nice and subtle and just lets enough of the noise through to be a pleasure.

There is a lad, a tractor driver who works at a farm near to me. He owns a normally aspirated Subaru Impreza with a large bore exhaust. He's not a boy racer. The gearchanges are slow and deliberate with a light touch on the accelerator, but it sounds just horrible - like someone with a deep voice gargling up the road.

Tip for 2.0 owners suffering performance flatspots - leftfield lenny

JosephNZ, on other forums regarding hesitant Subaru's there certainly has been cases of the problem being traced back to the air flow sensor. I suppose the most important thing is to get the car looked at by a dealer. A competant one at that, if some of what I've read is to be believed. So we have at least two possible causes of this problem. Oddly, the common link so far is to do with the engine's management with air .

Tip for 2.0 owners suffering performance flatspots - leftfield lenny

Following on from the initial thread being posted I've also discovered that the notorious flat spot can be replicated easily because my car is fuel sensitive. It dislikes UK supermarket fuel (the minimum octane rating?)

I am at present running it on high quality unleaded 95 ron which is obviously more expensive than the supermarkets own fuel. But on another Subaru forum I've read good things about Tesco's milleniun 99 ron octane unleaded, so I may give that a go. All very strange to me, because I thought that all fuel was purchased from the Rotterdam market. Maybe individual fuel companies add (if they want to) their own unique potions to distinguish their products from each other, hence the performance difference.

Edited by leftfield lenny on 08/05/2014 at 21:06

Tip for 2.0 owners suffering performance flatspots - Sofa Spud

QUOTE:....""When the volume is at the acceptable level, there's something captivating about the off-beats of aSubaru exhaust""

And countless boy racers found they could impersonate the Imprezza sound in their Astras and Saxos by disconnecting one plug lead! Presumably these were the same people who a few years earlier liked to make pretend gear changes on their CVT mopeds!

Tip for 2.0 owners suffering performance flatspots - misar

Following on from the initial thread being posted I've also discovered that the notorious flat spot can be replicated easily because my car is fuel sensitive. It dislikes UK supermarket fuel (the minimum octane rating?)

I am at present running it on high quality unleaded 95 ron which is obviously more expensive than the supermarkets own fuel. But on another Subaru forum I've read good things about Tesco's milleniun 99 ron octane unleaded, so I may give that a go. All very strange to me, because I thought that all fuel was purchased from the Rotterdam market. Maybe individual fuel companies add (if they want to) their own unique potions to distinguish their products from each other, hence the performance difference.

My own experience over 50 years is that with some cars you may get improved running with a specific fuel brand but it is totally wrong to equate cost and quality.

On the second point, every automotive fuel sold in the UK has an additive package which does indeed vary with brand. Of course, every supplier would claim theirs is better but they would wouldn't they?

Have a look at this review/test:

www.carpages.co.uk/motoring-news/fuel-performance-...p

Its a few years old but I doubt much has changed.

Edited by misar on 09/05/2014 at 22:12

Tip for 2.0 owners suffering performance flatspots - hillman

Yes, misar. Which? magazine ran an article on fuel types in September 2008 after extensive testing and reached the conclusion...

There’s no conclusive evidence to show that super fuels are better for your car in the long run - so in a time of high oil prices, why would you choose to pay more?' Which? Car editor Richard Headland said: 'For many cars it’s a waste of money paying over the odds for so-called 'super fuels'.

Tip for 2.0 owners suffering performance flatspots - joc

Anorak alert. In my 2006 2.0R Sport over the last 16,100 miles: it's done 11,789 miles on tesco momentum 99ron at an average of 34.59mpg; it's done 4,363 miles on 95 ron at an average of 32.48mpg. Put another way, on my data, it is about 6.5% more economical on fuel around 3.5% more expensive (and it seems to run better too). That equates to a saving of around £54 for every 10,000 miles covered.

Edited by joc on 13/05/2014 at 23:39

Tip for 2.0 owners suffering performance flatspots - madf

When your tests were carried out, were they in the same season? Eg all winter or all summer?. As fuel consumption rises when it gets colder, and it's now spring, your tests as posted suggest much of your better mpg occurred ins spring and your lower mpg in winter.

If so, your tests are meaningless.

Tip for 2.0 owners suffering performance flatspots - joc

Agree with you! Absolutely aware of cold weather effects and I wholly accept these are not at all scientific, they're just my data. I have bought less 95 during summer, not by design... Cutting the data: November to February, 32.5 on 95 and 33.5 on 99. For March to October, 32.5 and 35.15 respectively. Heavy caveats, smaller datasets, no guarantee of driving consistency etc etc. So although not entirely scientific, there is some bias in the data over 16k miles. But I'd agree with the general scepticism of whether the bias is genuinely significant enough. maybe 30 or 50k miles is need to smooth out the data further.

Tip for 2.0 owners suffering performance flatspots - leftfield lenny

Sorry Misar, I should have made my statement clear. Replace high quality unleaded for branded image petrol - stuff it, let's not beat about the bush here, I use shell or texaco petrol instead of the usual supermarket ones. I also use applegreen's (they're Irish with quite a few chains in the UK) 98 octane petrol. My scooby doesn't like applegreen's 95 ron unleaded. Neither does my brothers 2009 Mazda 6 2.0 petrol. In fact that's just as sensitive to petrol as my Subaru!

As for fuel economy, I must just be heavy footed therefore recently, I tend to leave the aircon on auto.

 

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