Random 2nd Gear Boost
20 May 2010, 12:46 PM
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Random 2nd Gear Boost
I seem to have a strange issue with my Impreza that only happens every so often, most of the time it's fine and runs like a dream
however, sometimes when I put my foot down in 2nd I will only get ~0.5 bar of boost, which is actuator pressure and it's like the solenoid is not opening to increase the boost as normal 
now this only happens every now & again randomly, it will only do it once (if you lift off and try again it's ok) and it's only ever in 2nd gear 
it did it with the standard ECU fitted and it still does it with the Prodrive ECU fitted, the car is an MY99 UK Turbo by the way
now I think it's unlikely to be the solenoid as it wouldn't just be confined to 2nd gear and would also do it more often in my opinion, but you never know
I've already had the original solenoid off, cleaned & checked it and seems to be fine, but I am going to try another one just to make sure
could it be something like the map sensor reading wrong and not letting the ECU open the solenoid?
I'm hoping Splitpin will be along soon to solve this mystery, LOL 
20 May 2010, 12:50 PM
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Hi Rich 
The later subaru's (I know the MY00 turbo's had this) have a built in roadside emissions test function, where if your in second gear for more than xx seconds it puts it into this mode, basically reducing the emissions so they pass, but also knocking back the boost, works fine in 3rd though if you change up??
Tony
The later subaru's (I know the MY00 turbo's had this) have a built in roadside emissions test function, where if your in second gear for more than xx seconds it puts it into this mode, basically reducing the emissions so they pass, but also knocking back the boost, works fine in 3rd though if you change up??
Tony
20 May 2010, 12:53 PM
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Given the symptoms, the solving has already been ably dealt with by Mr Burns. 
If you want to rule out your query re. MAP sensor (etc) then log it and see what's happening, but in the absence of any further info, and given that you say lifting the throttle and going back on immediately clears it, Tony is probably on the money.
If you want to rule out your query re. MAP sensor (etc) then log it and see what's happening, but in the absence of any further info, and given that you say lifting the throttle and going back on immediately clears it, Tony is probably on the money.
Last edited by Splitpin; 20 May 2010 at 12:55 PM.
20 May 2010, 12:59 PM
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interesting...
it does only seem to do it if I'm in 2nd driving along and then plant the throttle, which ties in with what Tony is saying
any way to get rid of this?
it does only seem to do it if I'm in 2nd driving along and then plant the throttle, which ties in with what Tony is saying
any way to get rid of this?
20 May 2010, 01:20 PM
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I won't be going down the remap route for the forseeable future as I'm happy with the car as it is with the Prodrive ECU, so I'll just have to live with it I suppose
plus now I know about it, I can avoid holding it in 2nd for too long so it doesn't do it
thanks for the help folks
plus now I know about it, I can avoid holding it in 2nd for too long so it doesn't do it
thanks for the help folks
20 May 2010, 01:44 PM
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out of interest...
does anyone know how many seconds it is?
is that just when in that gear or do you have to be off boost or below a certain boost as well?
just trying to determine under what conditions it does it, then I can avoid it happening
does anyone know how many seconds it is?
is that just when in that gear or do you have to be off boost or below a certain boost as well?
just trying to determine under what conditions it does it, then I can avoid it happening
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20 May 2010, 02:26 PM
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Years since I looked at it and I don't have the relevant info to hand (or in head), but from what I recall there are about four different parameters that have to all line up to trigger it. Road speed between a and b, rpm between c and d, throttle opening angle between e and f, boost pressure (or maybe solenoid duty) below g, and all of the above true for for h seconds otherwise the timer resets and starts from zero again, you get the idea. The whole point of it is that it's supposedly difficult enough to trigger so that the test driver will be able to do it deliberately but end users won't notice it. Unfortunately, as you've probably found out, sitting behind traffic in second while waiting to overtake is a perfect way to do so.
Timer value (i.e. h) is in the region of 6 seconds if I remember right, but that'll be based on the JDM STi ECUs, I would presume the PPP one is the same but couldn't swear to it.
Timer value (i.e. h) is in the region of 6 seconds if I remember right, but that'll be based on the JDM STi ECUs, I would presume the PPP one is the same but couldn't swear to it.
20 May 2010, 05:29 PM
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yeah, that's the sort of scenario, in 2nd waiting to accelerate, then go to do it and get less power than you expected
thanks for the info though
thanks for the info though
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