MY99Impreza

(Taken from http://bbs.scoobynet.co.uk/showthread.php?t=480466)

Sprint cars only... Interesting.

I'm going on a bit of a driving holiday next week in France and through Germany and I'm bringing my scoob!!! Lets just say I'm tempted to see what the car will do flat out. What better opportunity to try this out without breaking the law than to give it a blast on a stretch of speedlimit-less Autobahn?

But after reading this thread, I'm not so sure... How long would you hold the car at high speeds, to avoid engine troubles? Are we talking 30secs max?

Also, (perhaps more importantly) apart from checking tyre pressures etc is there anything else you'd recommend checking before travelling at high speeds??

(talking a standard, 99UK turbo here, no mods, gauges or knocklinks)

ALi-B

iTrader: (1)

Well in general, ANY engine on ANY car is more likely to blow up if held at maximum load for long periods (i.e flat out).

The problem with scoobs is they do not have the same safety margin interms of reliability as say, a 1.1 Corsa It's all relative - more BHP per litre, less durable - especially in extreme operating conditions.

Many factors are involved in this with a combination of them being the demise of many scoobs:-
Oil temps vs oil types (i.e high temps from flat out running, needs oils capeable of withstanding it (or more frequent oil changes).
Mods without any re-mapping. Or bad fuel map. Or bad mods. Or Jap imports not mapped for UK fuels.
Sensor failures (or partial failures)...namely the notrious MAF sensor.
And finally, the inability for the driver to feel, hear any signs that the engine is not healthy.

Also if there is an inherent problem with the engine (eg:- excessive bearing clearances or wear, from abuse, oil starvation, or wear and tear). It'll always come to light after you've planted your foot down that long open straight

Finally there is an issue with the intercooler not working effectively at high speeds due to the aerodynamics of the scoop/front of car, which has the potential to cuase problems....especially when combined with any of the above issues.

ryn004

i took mine flat out not knowing that I would (ie no preparation nothing) and I kept it about 140mph for about a minute, I was in Italy and speeding is not legal. I have a MY97 WRX. Mods - magnecor leads, earthing kit, and sti air panel.

ScoobyDoo555

There was a post a few years ago about someone who'd done this - stopped to fill up, got back on the road, and the engine shredded itself

One of the first major engine blows - IIRC the cause was excessive durations at max speed, combined with not cooling down properly etc.......

Some of the older members will remember it (IIRC it was a blue Scooby P1 or 22B). Pictures of their engine parts strewn all over a garage whist theywere on holiday - cost em a fortune to get home.

Apologies it's not more detail, but my memory ain't so good these days

Dan

scoobfan

That's done it, it will let go any time now !

Rob

p1mark

Purely from personal experience........

dont do it.......

over a period of about 10 miles, i was having a play with a mate (on a closed foreign road of course ), me in my P1, him in his spec C. We basically drove flat out all the way only slowing for roundabouts etc so at certain points we were off the clock for 20 secs or so. Car was up until then 100% reliable and mapped by one of the most respected mappers around.

noticed oil temp at 115 deg, backed off, Knocklink went all christmas tree on me, clatter clatter clatter, big end gone.

I was a ****, anyone who does it is a ****. You have been warned

jimby

i have a friend at prodrive
they build dozens of groupN imprezas
they take standard STIs from the factory and do the bare minimun of work to them

the cars are then thrashed and thrashed and thrashed again 1,000 times more than they would ever be on the road and they dont fall apart.

also a friend at the nissan factory is on the engine side of things where they take each engine and run it at 10% more than max revs for 24 hours, then they do it at 20% and then 30% more than the max stated revs. the engines dont blow up.

scoobfan

As has been said they are not high speed cruisers but
sprint cars, you have been warned.

If you want a high speed cruiser buy an M3 !

Rob

jimby

did you get to find out when the engine was stripped what had caused a big end failure?

Harvez

Ive taking the impreza to the top a few times now and had no problems, bit worried now after a friend racing a bently in a skyline, his fuel regulator packed in and detonated 4 pistons !! Not something id like to happen to me

flynnstudio

This surely can't be true...they are rated to 144mph - why would they build the top gear ratio so high if they weren't reliably capable of these kinds of speeds.

I find it impossible to believe they are so fragile...I would regularly run my stock 22 year porsche to 140mph (on private roads naturally) and on one occasion had it at 164mph for a good 3-4 mins and never had the slightest problem (and this was on a gentle uphill incline)...

Someone tell me please the engines in these cars are not this weak...

p1mark

There was no signs of det in the combustion area and i had no KL activity during the run, so it was not down to det shock down the rods IMO.

So you have to put it down to something oil (press/temp) or material/design related IMO.

Lets face it though, the real reason is cos i was a tool.

wide

Just out of interest in this debate many of us have owned cars with piddly little 1.0l engines like my old vw polos and were held at full throttle at 90/95 for hours, why didnt they go bang.
I just get the feeling some of this is cars that have been too finely tuned and bad luck

mg driver

i dont think you will have any problems in a standard car ,in factory spec they should run at the quoted top speed no problems.

wrxtankie

I used to cruise my 02 WRX at 130 with jaunts up to 150 with no probs. I did this a fair few times on my trips back to theUK from N Germany.


Changed oil every 4.5k filter every 10k or second oil change, warmed it up cooled it down etc.

Then some bitch drove into me head on and wrecked it

RedScoob

I think that people underestimate the durability of the Impreza flat-four. Most of the "horror" stories I've heard have been about only one or two STi variants largely running lean due to unsuitable fuel.
There is no way on this earth that I'm going to baby my engine, I bought it as a high performance saloon, so driving it like a granny would be a bit foolish (IMO). Preventative maintenance is the key with all highly tuned engines, if you don't look after it between driving, then of course it's going to go "pop".

ALi-B

iTrader: (1)

I had a 1.3 B- reg POLO it often saw speeds above what the speedo could read and that was with a 4speed gearbox. Had a 1.3 Sunny too, which got the same treatment...although that did suffer minor valve gear problems (caused by the lack of several bolt retainers on the rocker shaft by what ever bodgit mechanic did the head gasket, combined with a thrashing - causing them to work loose ).
Not to mention the works Corsas, it's Clios, Saxos and the vans. Only the one clio blew an engine in the midst of Scotland...but that was due it being ran out of oil. Being heavyweight and massively understressed engines, with a very low BHP per litre, they usually go on forever, provided they are well maintained and built to good tolerances.


As I said..it's relative. There are basic physics that just cannot be deified (both mechanical, metallurgical and thermodynamic).

Look at what is happening in these two engines:

A 2.0l turbo Subaru with 4 pistons going flat out, producing well over 50bhp each onto a loaded area of bearing surface not much more than 10cm².
A Corsa 1.2 engine producing 70bhp flat out only has to unload 17.5bhp per piston onto roughly the same bearing area.

So the presence of an adequate oil film and avoiding shock loads (from detonation) is absolutely critical on the previous due to the increased loads. (more on this point later).

Also, there are the heat issues of 50bhp worth of explosion in each combustion chamber. Which translates to hotter temps and greater importance of combustion control (both mixture, boost and ignition ). Accompained by the usage of lighter alloy metals with lower thermal stability and lower melting points, means combustion control is much more critical.

Now bear in mind an engine on the whole uses oil for cooling the moving components (coolant just cools the cylinder head, upper cylinder liners and turbo bearing housing ). If the oil gets too hot and breaks down from it not being changed regulary enough for the intended usage conditions (such as 6month changes when someone does regular track days)....Remember what I mentioned about how critical the presence of an oil film is on a bearing surface having to live high loadings - if the oil loses its lubrication abilities, guess what happens.

What do Subarus engine often suffer from? Melted pistons and bigend bearing failure.

They aren't fragile engines. If operated in in normal road conditions on the UK's roads it very rarely has to use all of its 200+bhp worth of power for any period of time. Hhow long do you usually stay flat out at 4500+rpm? Not very often for most people. So it never produces all of it 200+bhp for any length of time, which is why there are many very old Subarus, both Legacys and Imprezas still on the road with well over 100Kmiles and never seen an engine rebuild.

If you abuse it....eventually, you'll lose it

bob r

iTrader: (46)

after reading various opinions, some of them very alarming dont think a top speed test is a good idea unless you are prepared to shell out your hardearned if it all goes wrong, but then again i can be a bit too sensible sometimes

Iwan

If you have an oil temperature guage you'll quickly learn what a difference sustained high speeds makes to oil temperatures. The impreza was designed as a sprint car as has been stated many times, as such it has no need for an oil cooler so there isn't one fitted. At a 70mph cruise my oil temp is approx 85degC, if I up the speed to say 100mph (on a track obviously) the oil temp quickly rises to over 100degC - you can guess what happens if you go higher. Without an oil cooler the oil gets too hot, and gets closer to the point where it can't keep metal parts from touching each other.

Bearing in mind a P1/STI5 will hold an indicated 160mph if you keep your foot planted, I wouldn't want to imagine what the oil system is doing within a few seconds of this sort of treatment.

If I wanted to do sustained high speed runs then I'd fit an aftermarket oil cooler. Since I don't, I just fill the engine with good quality fully synthetic racing oil - and keep a close eye on the oil temp guage. Anything more than 100degC and I back off and take it easy.

flynnstudio

mmmh - this thread hasn't made me feel any better but I'm certainly not going to worry about it...The boxer engine was one of it's main draws for me...
However, looking at the bhp/torque curve of my new car then at 4000rpm in 5th I'd be pushing the engine to just over 200bhp...that in my book going to equate to 85/90mph - quite easily achievable even on uk motorways for extended periods of time ( not that I would do this of course - naturally) - so given that : it would seem that I have (reluctantly I might add) discovered the first essential mod on my new car - an oil pressure and oil temp guage...I suppose this is why the 911 has a dry sump - its maintaining full oil pressure at all speeds and especially whilst cornering...

On the subject of flat four boxer engines and barrel linings - does anyone know if the imprezza barells have any kind of coating ?- The 911 boxer flat six had nikasil lined barrels which were extremely thin - the nikasil coating literally microns. They barrels were finned and bolted onto the block - in accordance to what has been said here it was only the extremely efficient and high pressure oil cooling inside the cylinders that keeps it effective - the 911 actually having a front mounted oil cooler to facilitate this- needless to say they never had cooling issues so I can see that the boxer design is not fundamentally the issue -
Regardless, I would also have expected the materials made to manufacture the imprezza engine were substantially better than those used on a corsa - otherwise what are you actually paying for ?
Unfortunately I am quite new to the imprezza so I have not yet acquirred the nessecary technical knowledge to be know what is fact and what is feeling about this motor yet.
I agree that it is often VERY difficult to RELIABLY increase horsepower over the manufacturers original designs - these guys spend millions manufacturing tolerance and planning mean time to failure specifically to avoid financial ruiin when they release a new car...the fact that they stand by the prodrive pack clearly shows they are confident that the block can handle 300bhp...

Out of curiosity does anyone do an grill mounted oil cooler or a dry sump conversion for the imprezza ?

Suresh

Provided your car is properly mapped for the fuel you are using, you'll be ok with a short, sustained vmax run (2 mins or so). I used to cruise down to Switzerland in a tek3 classic (conservatively mapped for 250bhp on SUL) fairly reguarly and I would hold the car at an indicated 125 - 135 for fairly long periods on the A81 especialy - only slowing for other traffic - and it never went pop. You could see the fuel gauge moving though!

Suresh

Jdub

Havent read through other posts in this thread, a word of warning, I lived in Germany for 4 years 2 of which I had a Pulsar, there are now only a couple of unlimited Autobahns, and even on these over a certain speed your insurance can become void. Also be carefull as the likes of AMG Mercs have a habit of just pulling out on you, not fun at 130+! also be carefull not to speed on normal roads as they have speed cameras in wheely bins etc..

Other than that have a great trip.

flynnstudio

I've just found the second mod...

http://mastrowrx.com/index.asp?PageA...ROD&ProdID=294

Better still...http://www.powerengineering.co.uk/ac...tm#TAoilcooler

Strange that prodrive don't do one - seems like a no-brainer..

Shame subaru would probablyhave a warranty fit about it. I intend to find out..

seems surprising that air filters and dump valves are considered over what seems like me to be THE most CRITICAL 1st upgrade on this car...even if it means you extend the life of your engine by 20K it's got to be worth it...

I'm not one for doing lots of high speed runs but it certainly has been a revealing and informative thread...

rexabusa

is the oil not water cooled when it passes through oil fiter , whats the water flowing through the pipes above oil filter for?
if water is helping to cool oil, you could remove thermostat to keep water really cool. i am running my car with no thmst and the gauge barely rises above quarter at ANY speeds.
or am i talking gumph again?

zerosports do a cooler temp thermostat

scoobysmiff

iTrader: (2)

i live in Germany now and i quite often get my standard MY99 upto an indicated top speed of 150 and reguarly drive at high speed 120+ for prolonged periods, i have a fairly new engine of about 12K, i reguarly change the oil for some quality synthetic stuff and i have not had a problem at all, i guess its just down to luck or the car in particular?

p1mark

The oil is cooled by boiling hot water via the modine so not a lot of use realy. Ignore the water temp gauge, its a joke, as Iwan says above you see whats happening with an oil temp gauge. My water temp gauge never goes above 1/3 up either and was still low when i had 115 deg oil temp.

My car is obviously going to produce more heat than some of the lower powered cars people are talking about above, but i still would never risk it an a 220bhp version.

This thread was not about high speed cruising - i have held mine at 120mph+ for an hour or so no problem (autobahn of course) - The original poster asked about a flat out trial and these are best avoided IMO.

Martin2005

Did anyone see 5th Gear a couple of weeks ago when they were reviewing the Focus ST. They showed the engine being tested and quoted that it was run at full power for 2 MONTHS (it was glowing red hot in places). That equates to over 200,000 miles at full power (150mph), with no oil changes. Just goes to show that the modern car engines are astonishingly reliable.

Kuro

Exactly, if you want sustained pace, buy a GT type of car like a 350Z or something. Scoobs are great machines but a jack of all trades they are not.

MY99Impreza

I remember reading somewhere recently that a P1 will pull to red line in 5th gear, so I suppose in any car geared like this - its the sustained high engine speed thats doing the damage.

But, I'm guessing in my "out of the box" UK scoob, probably wont pull close enough to the red line in top gear to do damage, well for a short flat out burst anyway.

In saying that... another way of looking at it is, how long would you hold your car in 2nd gear at 6500 rpm? The difference is in top gear at this rpm you cant hear the engine screaming its nuts off cos of the noise of the wind, road, wife screaming in the passenger seat etc...

Anyway, like most of you have said, its a bit of a gamble. If not with the engine, then a lane changing AMG merc!

flynnstudio

This is of course very true and good advice - and somewhat comforting. I think the oil temp & Pressure guage first off - review the temps and if running into high temps then consider the fitment of an oil cooler.

That info about the Ford is amazing. I would never have suspected it of being so tough...