Hi i did a Top speed run at the weekend (yes to all the law inforcement people it was on a runway).

As i got over 155mph my CHECK ENGINE light came on.

A then started to abort my run but as soon as i got down to about 40mph the light went off so i decided to try again.

Same thing happened again and aborted a second time and again round 40mph the light went off.

Does anyone know of what this might be. I have checked the engine but can't see anything obvious.

I was told it could be my air fuel mixture not being set correctly at that speed but then i thought that speed wouldn't have a part in that as it would be to do with the revs at the time.

Help please

Thanks
Dave

 

get the error codes checked as they would have been stored

Scoobypedia | Trusted knowledge for everything Subaru | Knowledge / ECU (for both classic and new age cars)

 

awaiting new thread, "my engine went bang"

 

very possibly as impreza's arent built for a reliable top speed.

 

Imprezas do not like sustained top speed runs, apparently the airflow can go over the scoop at these speeds.

My big ends went after doing this myself so be careful.

 

High speed runs are a NO NO.

Rgds Red.

 

I had a phonecall from my mate on Sunday who had attempted a brief(ish) top speed run in his '95 STi the day before. The engine made a strange sound, complete loss of power, and anything over 2000rpm produced a banging/scraping sound.

Oil starvation to the big-end bearings, or just too much load for the engine to handle?

 

Surely if japs have a 112mph speed limit they don't really bother doing much R & D on cars beyond this speed (even though they manufacture for other markets)
If that is the case then I am not sure if the scoop's ability to flow air has really been tested at high and sustained high speeds.
Is there any truth in this

 

I reckon blasts in imprezas are much more fun than winding it up to 130mph etc.

0-70 is more fun imo.

 

Probably crappy aerodynamics of the classics bonnet causing the air to be deflected over the scoop at, ACTs increase, det sets in and goodbye big ends!

Oh, and he was ragging a 13 year old car - probably didn't help!

If you plan on doing high speed runs on a classic get a FMIC, which will keep ACT temps down, Oil cooler may also be a good idea!

But even then you need to remember these are sprint cars not autobahn blitzers!

Ns04

 

He's had a FMIC for some time, and has recently fitted an oil cooler in place of the original intercooler, but you're totally right about ragging a 13 year old car...

 

So best to avoid topspeed runs in it then. Didn't rag the car upt to that speed just took it easy upto 70 then left in 5th and let it do the rest.... Not really after a high speed just wanted to test see if the limiter had been removed properly. just woundering on that engine light.. doesn't come on at anyother time.

Thanks for the advice guys. keep up the good work.

Dave

 

To be fair to the OP: he's only maxing it on a runway so can't be at that kind of speed for more than a few seconds before he has to back off. It's not like a sustained run on a 50 mile stretch of unrestricted German Autobahn is it (if the fuel tank would last that long!)?

Maybe he's got a primitive early version of one of those 155mph speed limiters like the Germans put in big Mercs and Beemers!

 

what car was it

 

CEL might have come on due to overboosting?

 

1997 STI Import

 

Sorry but what is a CEL?

 

and u got 155 out of it i been upto 145 then backed off believe scoop stops working after 100

 

It was still pulling strong at 155. might have to look at a front mount intercooler if the scoop design isn't good for a high speed run.

 

CEL = Check Engine Light

 

wats a sti top speed then

 

Not to sure.. Think WRX and STI's have a top speed of 155mph. unless they have been played with then could be anything. The new impreze (as ugly as i think it might be) will top out round 155 mark. Not sure on the Classics though.

 

I've seen 155mph on my classic uk Impreza Turbo a couple of times. It didn't take long to get there but it wouldn't budge past 155mph so 160mph is out the question for mine. It's only got 260bhp too - less than an sti.
I soon slowed down afterwards though as I know that the top mounted intercoolers don't do a good job above 110mph

 

ive got FMIC and oil cooler built up 2ltr engine and i also get det spikes dont know y though?perhaps some one can shed som ideas my knock was showing 86 on the apexi.put my foot down again it was fine?

 

Mines the same. gets there very quickly... will go over 155 no trouble just don't want anything going bang with this check engine light on.

Didn't know that the scoops didn't work over 110.... why is this? Is it just a design fault or is it something the subaru built into there cars?
If i was to fit a version 8 scoop would this over come the problem as mine is much smaller than that.

 

86 knock most ive seen is about 58 with dodgy fuel bought at donnington and that was with a liberal dose of nf. i was told to start worrying at 60.. so i would imagine your close to going pop at 86.. one thing i have noticed is that mine doesnt like being booted in 4/5th gears from low speeds thats when mine goes into the high 20's.
It will stay around 12/15 when going through the gears up t0 about 6500 rpm and since thats where my max torque is i dont see the point in ragging it up to the rev limiter which is set at 8250. which by the way is when the check engine light will flash. and mines a built type r also with an apexi.. top speed depends on gear ratios mine is 156mph as are all the type r's i believe.. my o4 wrx went off the clock 160mph and was still pulling the bloke in the 911 turbo couldnt believe i was still there flashing him to move over. and yes it was in germany..

 

I dont see any reason for detonation with a front mount and with a proper map. Unless something in your fuel system is not working properly you shouldnt get any det.

 

The Impreza wasn't subject to very good aerodynamic tests when it was developed so apparently around 110mph the air passes straight over the top of the scoop, which means the intercooler doesn't get much air. The engine then obviosuly isn't getting the cooling it needs and can therefore lead to engine failure eventually.

There are 2 ways around this problem if you frequently do high speeds. You'd need either a STI8 intercooler (the best intercooler made by Subaru for the Impreza) with larger scoop and undertray - not a straight fit but can be done. Either that or a good quality front mounted intercooler - this will require chopping about of the front of the car though.

 

I always thought part of the top speed problem was that a lot of the development work was done with rallying in mind ( the Impreza being the next step up from the Legacy for Subaru ) as the road car has to share a lot of the rally car design for homologation rules ?

In rallying, long high speed runs are rare, its more important to have low down torque, fast acceleration and good handling and balance, which funnily enough just about describes the Impreza.

The bonnet scoop is probably a compromise though as due to the shape of the car it will only be effective up to a certain speed - only solution would be to make the scoop a lot taller, which would be harder to see past.

 

--------------------------------------------------------------------------------
#26 (permalink)
Quote:
Originally Posted by mus 1st class sti type r
ive got FMIC and oil cooler built up 2ltr engine and i also get det spikes dont know y though?perhaps some one can shed som ideas my knock was showing 86 on the apexi.put my foot down again it was fine?

86 knock most ive seen is about 58 with dodgy fuel bought at donnington and that was with a liberal dose of nf. i was told to start worrying at 60.. so i would imagine your close to going pop at 86.. one thing i have noticed is that mine doesnt like being booted in 4/5th gears from low speeds thats when mine goes into the high 20's.
It will stay around 12/15 when going through the gears up t0 about 6500 rpm and since thats where my max torque is i dont see the point in ragging it up to the rev limiter which is set at 8250. which by the way is when the check engine light will flash. and mines a built type r also with an apexi.. top speed depends on gear ratios mine is 156mph as are all the type r's i believe.. my o4 wrx went off the clock 160mph and was still pulling the bloke in the 911 turbo couldnt believe i was still there flashing him to move over. and yes it was in germany..

--------------------------------------------------------------------------------

i know sometimes you will get ghost det from changing gears, my rev limiter is set to 7600 and i barley need to take it that far to be honest.ive booked my car in to slow boy to get it looked at im droping it off this sunday to get peace of mind.