DJ140

Just driven 400 miles today and my 03MY is running really well. I agree that some days it does feel slow, but it can't be just weather related as it was 35C in Cambridge and no problems.

I always use Optimax too, so there should be little variation in fuel quality. Tried SUL once and the MPG went down dramatically, think it was BP stuff.

Also only saw 1 Impreza all day, is this a record?!

Dan

[Edited by DJ140 - 8/6/2003 4:26:32 PM]

Silverback@work

OK,

Might be subjective and I was always convinced that running the Scoob in hot weather meant an inevitable drop in performance (and the A/C on takes even more away) but...

In the last few days my MY03WRX has felt in 'fine' health and am now wondering if 'hot' weather alone is not the only factor affecting performance (humidity?).

Sometimes though the car does feel like it's running on a 'bad' batch of fuel (if there is such a thing)...but I always fill up with Optimax, normally from the same place.

Any other experiences?

chrisp

My scoob the other weekend (when it was hot) was not getting full boost (about 0.2bar down) and not pulling like normally did and turbo coming in 500-1000rpm later. Cant be the fuel as a couple of days later when it went colder everything was back to normal. This was driving in mid day heat and oil temps hitting 110-115c at 65-70mph on the motorway.

IN THE STICKS

my MY99 turbo just seems to make it up as it goes along , one day it will fly , the next with the same weather it feels like I'm towing a caravan (can only imagine what thats like , because I wouldn't be seen dead towing one !)

Dave

STWEST

Would have to agree, owned 5dr MY98 turbo, for 2 months now, it is running much better in the really hot weather, just seems to pick up cleaner, am running UL and was considering upgrading to Optimax, not so sure if its worth it now.

Cheers

WrX 03

I've had murder with this thing and Subaru, but admittendly this latest spout of hot weather hasn't seemed to effect it, well not as bad as previous. The cars just done 3500miles and feels like its loosening up as well as using nothing else than optimax. Subaru's always said it was the warm weather, but I,ve kept a diary (for arguments purposes) on daily temprature, humidity and atmos pressure. The only thing that corresponds with power loss seems to be humidity!! So even when its raining the high humidity of upto 90% has effected it. Optimax has definately made a difference though. Dont know how many miles your motors have done yet, my advice is grin and bear it if its still low. I'm not half as disgruntled as I was, I was almost ready to drive the fecking thing back thriugh the showroom window, not that bad now.

Good Luck

WrX 03

STWEST

Definately get on the optimax, didn't want to admit it but most of my problems were when running on regular UL. I know optimax is a little more expensive, but apparantly you'll benefit in the better mpg. Can't vouch for that cos I've never bothered to work it out.

STWEST

WrX 03

Thanks for the info, think I will give it a try next time I fuel up.

Cheers

WrX 03

You'll need 2/3 tanks to get best results, but you'll notice still notice after the first ;-). Have to do that cos don't know how to do these face things yet!!

Silverback@work

My MY03WRX has covered about 11,300 miles now.

Has always been filled up with Optimax (other than once when I had to put regular unleaded in - boy was that a shock). Makes a very noticeable difference, although haven't given super a go (Optimax is cheaper in general).

I'm convinced either (a) there is a big variation in Optimax fuel quality or (b) there is something atmospheric (normally occuring when weather is hot, but not always - the last few HOT days have been OK in terms of performance) meaning that I don't get comparative peformance with my car day to day.

Mind you, I guess this is all a bit subjective. Perhaps I should keep a diary of 'good' and 'bad' days and visit power engineering for real world figure comparisons. Anyone know how much it is to get some dyno readings at places like this?

Interested on the comment re: humidity

STWEST

WrX 03

OK, do you recommend waiting till I am almost empty for the first fill up or not, reason is I am away at the weekend and will top up before I go needing about 1/3rd of a tank to fill up, have checked and there are no Shell garages near my destination.

Cheers

Silverback@work

ST - I would go as low as you can b4 filling up fully with Optimax - otherwise your fuel will just be diluted part unleaded/part optimax.

Should take about 1/2 tank or so to get up to full pace (if not a bit more)

MadMark

My 03 definitely feels much slower in this heat (particularly at high revs)and it has never had anything other than Optimax in it over the last 7,500 miles!

Graz

I thought the maps in the 03WRX were now optimised for Super/Optimax. Normal unleaded should therefore be avoided wherever possible.

I have a MY00 and for the sake of a few £ per tank of super it makes a world of difference, plus you get the added safety margin that high octane fuel is less likely to detonate and destroy your engine.

Henrik

iTrader: (5)

On our first day we drove 350 miles and didn't see one Impreza The next day while doing 10 miles in town we saw five tho (one of which waved)

st

Yesterday in Manchester (quite hot) MY03 WRX felt sluggish. This morning, overcast, cooler. V Fast
Can't explain it but it must be the weather.

ARM-Scooby

I thought that humidity was the factor anyway. As humidity increases so does the temperature of the air particles, and their size increases. Therefore in one cubic centimetre there will be less air particles and the engine will not work correctly. When it is cold and less dense, there is more air per cm²
The fuel does help a lot too!!


WRX 03 go to http://www.click-smilies.com/ select the smile that you want, then copy the http link it gives you at the bottom and then paste that link on here!

WrX 03

Cheers ARM

Just another note on the power thing, I opened something similar a couple of weeks ago, and I was told its something to do with the temprature correction to protect the engine (been a bit over cautious if you ask me!). Keep on to the dealer tho if its under warranty, they didn't tell you it'd be poo when its hot when they sold it to you did they!! Trade discriptions and all that. Good marketing for VW Golf GTTDi "will beat an impreza on a hot day!!!

chrisp

Yep but for the other 359 days of the year you should be okay .

WrX 03

lol@crisp , you don't work for subaru do you? Don't want them coming back with answers like that!

Neilo

I have also experienced a drop off in performance when it gets hot, and im trying to put my finger on it too......i just took it to the garage and on the way there it felt sluggish, accelerating like a normally aspirated car....no kick like were used too...i got the service engineer to take it for a drive with me in it, and we couldnt recreate the problem! sods blo*dy law.

Then on the way home it was fine......i have to say that its a MY03 and i "usually" run it on 95 ron, not optimax but do use optimax every 3rd or 4th fill.....should i not bother??

I also have a big problem with the gearbox which the mechanic confirmed.....looks like a new box after just 6000 miles.....joy!

X SOOOBY

just wait until winter gets here then you will know what hot weather can do to the performance of your scoob an extra 30-40 bhp drop

Bubba po

Humidity does not affect the temperature of the air, or the size of 'particles in it.'

Humidity is the measure of molecules of evaporated water in a given quantity of air expressed as a percentage volume.

Air is a mixture of many kinds of particles; the only really important one to us and our scoobs is oxygen. This reacts with our petrol in the process of combustion, which drives the pistons.

In a given volume of air, roughly 20% is oxygen. The rest is crap we don't need, such as water molecules. It follows that the more water molecules there are in a cc of air, the less oxygen there is to react with our petrol.

Humidity does not affect temperature, rather it is the other way round. Hot weather in wet countries like ours tends to increase the humidity. This, in theory, could affect performance for the reasons mentioned. I'm not sure if the effect would be noticable.

Temperature, however, should theoretically affect performance noticably for a different reason. Arm-scooby is on the right lines when he says that in cold weather the air is denser and there are more particles of 'air' per cc, except that he means oxygen. The volume of a gas, or a mixture of gases, depends on the temperature and the pressure. Assuming the pressure stays the same, an increase in temperature results in an increase in volume. This is because the energy supplied to the system in the form of heat gives the molecules more energy to whizz around, to collide with each other and to cause the gas to take up more space. This is the reason we turbo owners have intercoolers. They are there to cool the temperature of the air being forced into the cylinders by the turbocharger, making the volume smaller, so you can get more oxygen in. The cooling effect must be noticable or it wouldn't be worth adding the extra weight of the intercooling system.

Sorry about the 'plonking' tone of this reply, But its quite difficult to explain ideas like this without being precise about what you write. I hope this has been informative!

[Edited by Bubba po - 8/12/2003 1:53:22 PM]

Re-Bitten Hero

You beat me to it Bubba

Mine (MY00) varies by as much as 3psi between winter (-15C ) and summer (+37C )

Richard

WrX 03

Neilo, get it on optimax full time! Mine felt like poo when it ran on reg UL. Makes a hell of a difference!!

[Edited by WrX 03 - 8/12/2003 9:53:32 AM]