Most of the time i tend to stick to about 60mph on motorway. (fuel costing me half my insides) on back roads may go quicker but never over 100mph.. so i shouldn't need to worry about the scoop just yet (thats until i start getting more power and racing the thing . but till then shall just keep below 110 for know.

 

Lewak : Read the fault codes stored in your ECU. This will give you an idea of what is wrong. You can then reset the ECU and see if the fault codes are repeated. You can then take appropriate rectification measures.
I suggest you do not do this at an indicated 155 mph which on a standard STi 3 is likely to be a little under 145 mph.

Classic Subarus generally do not fair well in prolonged high speed running and unless you can monitor, oil temperature, EGT and air charge temperatures, you are venturing into the unknown.
It also helps if you can monitor DET and quick reactions to abnormal knock indications/counts are vital to preservr the engine.

Mustaffa : 86 is a high knock count and is probably a mapping or fuel supply related issue that has to be rectified before it causes serious damage. Hpoefully you have got away with it on this occassion.

 

found out it was a faulty fuel pressure Reg, its been leaking fuel dribs and drabs from the return pipe must got disconected somhow which made it run leaner therfore the knock goes up.thank u harvey

 

Mine does exactly the same 1995 WRX ive have tried a high speed run twice each time the ECL light comes on, I have had the ECU code checked and the main thing was the Air flow sensor, im glad you have put this thread on and its not only my car, must be a common fault.

 

After a lot of looking around and getting my mate to put my car into a air tunel.. he said anything over 115mph and the air doesn't go through the scoop....

what a mad design floor

 

Flaw

I've, honestly, never felt the need to see what indicated speed my car can achieve.

Cav GSI I had before the Scooby, had that off the clock though. Private runway of course.

 

The air goes over the scoop at 110mph ok. How does this damage the engine if you go over 110mph? The air sucked into the scoop is used to cool the air going into the engine. If the air isn't cooled then you get less performance, so the ecu puts less fuel in. Less load on the engine, but the engine it's self in under a higher load due to the strain and high temp, nothing at all to do with the top mount intercooler. The cooler the air the more oxygen it has in it hence better performance. The scoop is not there to cool the engine. If anything it makes the engine run hotter!

 

The top mount scoop is a design flaw. The best option is to have the intercooler at the front of the car. But the scooby scoop is what makes it a scoob.

 

That is understandable but it is required to cool the intake charge for the turbo so in turn can damage the engine. This maybe why the ecl comes on at high speeds.

 

never had problem with top speed in any of my impreza's, and belive me I'm an autobahn champion but my car is an eu sti, or the old was a bug wrx. Both been driven at 150-160 mph for extensive periods/miles without any problem/damage. I'd check the error codes.

 

As temperature rises the threshold for det gets lower - high speed runs will make engine temps rise very quickly just due to all thne reciprocating parts whirling around never mind the increased temperature from all the combustion. Scooby engines rely on a bit of overfuelling to cool them as well, so once the airflow stops cooling the intercooler temps rise rapidly for various reasons all of which will kill your engine sooner rather than later