MY97 butting boost. Any ideas how to fix?
28 June 2006, 03:12 PM
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MY97 cutting boost. Any ideas how to fix?
I have had my 97' Subaru uk turbo for about two months now and am very much enjoying it, but it has a bit of a problem with cutting all boost/ignition under load occasionally. I am very keen to fix this asap as recently I had to abort an overtaking manover due to having had all my power taken away, which was not very much fun to say the least!!
It is most likely to happen under load, especially say, if the turbo is building up boost from low rpm (2500) in a higher gear.
It also seems to whistle quite a bit in the higher gears sometimes (4th & 5th) which seems to be a little strange, even for a turbocharged car.
I have had a look at the FAQ and think it is pretty likely to be this....
Question is - how do I go about sorting it?
Where is this T shaped supply hose I am supposed to pull off and give the brake cleaner treatment?
Also, the faq mentions getting 97' cars upgraded. How do I do this?
Would fitting an aftermarket blow off valve/dump valve improve things? (not keen on a "chav" type sound - as discrete as possible would be nice!)
The one complaint I have about driving my Subaru is that is seems to be quite laggy and can be a bit slow on the boost coming out of tighter corners in comparison to other subarus - would an aftermarket blow off improve this?
Sorry about the 20 questions but this is my first turbocharged car and have only really messed around with n/a motors so far!!
Thanks in advance for any response.
Cheers
It is most likely to happen under load, especially say, if the turbo is building up boost from low rpm (2500) in a higher gear.
It also seems to whistle quite a bit in the higher gears sometimes (4th & 5th) which seems to be a little strange, even for a turbocharged car.
I have had a look at the FAQ and think it is pretty likely to be this....
3.1 Dump Valves (aka Blow off Valves and By-pass Valves)
There seems to be a recognised problem with the 1997 specification car's dump valve. This does not shut properly under boost and thus vibrates giving the sound similar to someone blowing across the top of an open bottle. It has also been likened to a steam train whistle or ship fog horn in extreme circumstances!. Meanwhile the 1998 model seems to have a totally revamped and larger blow off system, but I have had reports that the problem sometimes still occurs.
3.2 Waste gate solenoid
The 1997 specification lowered the turbo boost pressure from 1.0 bar to 0.9 bar. The engine breather system vents into the air intake and it is possible for the oil and condensing, burnt oil vapours build up in this valve. This valve is a safety device for detecting overboost and will cause fuel and ignition to be cut if it senses that 1.2bar (97/98 models) has been reached. If it is bunged up, it isn't sensing correctly and will shut down the engine under high boost conditions. The solution advised by Subaru France was not to fill the oil up to maximum but to leave it at half filled only.
If your wastegate solenoid does pack up, the fix is to pull the T shaped supply hose off and fill it with brake cleaner from an aerosol. Then go for a blast before the cleaner evaporates. Tippex thinners also do the job. '98 models have a revised part, which is three port sensing and there have been no reported failures. You can get '97 cars upgraded.
Apparently the fault often occurs just after a service when the oil level may be slightly too high. The 1998 specification engine apparently has revised sensing locations, to over come the above problems but there have been some reports of failure on early '98s.
Sometimes this fault is incorrectly termed as "over boosting". The sensor is designed to detect an over boost situation and is usually so sensitive in normal operation that 1.19bar = ok and 1.20bar = fuel cut routine due to over boost. When it becomes contaminated by oil, this is lost and the sensor can cut in at much lower boost values, cutting in the routine under normal hard acceleration. The effect of this routine is quite disconcerting as all engine power is suddenly lost with some drivers reporting it feeling as if they have just driven into a brick wall!
There seems to be a recognised problem with the 1997 specification car's dump valve. This does not shut properly under boost and thus vibrates giving the sound similar to someone blowing across the top of an open bottle. It has also been likened to a steam train whistle or ship fog horn in extreme circumstances!. Meanwhile the 1998 model seems to have a totally revamped and larger blow off system, but I have had reports that the problem sometimes still occurs.
3.2 Waste gate solenoid
The 1997 specification lowered the turbo boost pressure from 1.0 bar to 0.9 bar. The engine breather system vents into the air intake and it is possible for the oil and condensing, burnt oil vapours build up in this valve. This valve is a safety device for detecting overboost and will cause fuel and ignition to be cut if it senses that 1.2bar (97/98 models) has been reached. If it is bunged up, it isn't sensing correctly and will shut down the engine under high boost conditions. The solution advised by Subaru France was not to fill the oil up to maximum but to leave it at half filled only.
If your wastegate solenoid does pack up, the fix is to pull the T shaped supply hose off and fill it with brake cleaner from an aerosol. Then go for a blast before the cleaner evaporates. Tippex thinners also do the job. '98 models have a revised part, which is three port sensing and there have been no reported failures. You can get '97 cars upgraded.
Apparently the fault often occurs just after a service when the oil level may be slightly too high. The 1998 specification engine apparently has revised sensing locations, to over come the above problems but there have been some reports of failure on early '98s.
Sometimes this fault is incorrectly termed as "over boosting". The sensor is designed to detect an over boost situation and is usually so sensitive in normal operation that 1.19bar = ok and 1.20bar = fuel cut routine due to over boost. When it becomes contaminated by oil, this is lost and the sensor can cut in at much lower boost values, cutting in the routine under normal hard acceleration. The effect of this routine is quite disconcerting as all engine power is suddenly lost with some drivers reporting it feeling as if they have just driven into a brick wall!
Question is - how do I go about sorting it?
Where is this T shaped supply hose I am supposed to pull off and give the brake cleaner treatment?
Also, the faq mentions getting 97' cars upgraded. How do I do this?
Would fitting an aftermarket blow off valve/dump valve improve things? (not keen on a "chav" type sound - as discrete as possible would be nice!)
The one complaint I have about driving my Subaru is that is seems to be quite laggy and can be a bit slow on the boost coming out of tighter corners in comparison to other subarus - would an aftermarket blow off improve this?
Sorry about the 20 questions but this is my first turbocharged car and have only really messed around with n/a motors so far!!
Thanks in advance for any response.
Cheers
Last edited by AlastairMowat; 28 June 2006 at 04:21 PM. Reason: Title spelling, and still cant change the bloody sp!!!
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