Overboost, 854 T-5R 1995

Post by **MadeInJapan** » 27 Dec 2007, 16:24

First time I've heard of "over-boost" on these cars. Who makes it and how does it exactly work? Without this info, it would be hard to help.

Post by **MadeInJapan** » 27 Dec 2007, 17:49

You're just talking about the turbo coming on. I had actually never read that. So you're saying that the turbo doesn't come on like it should? Check your turbo hoses. I would be willing to bet that one has slipped off or one has a tear in it. Good luck!

Necromancer · Post by **Necromancer** » 27 Dec 2007, 18:27

The overboost is controlled by the computer which has different programming than a standard T-5.
I would think that the computer would manage the bypass valve in the same manor as a T-5 but allow the extra 30 seconds of boost on a T-5R.

Post by **MadeInJapan** » 27 Dec 2007, 18:56

Very interesting...it's good to learn something new everyday.

Necromancer · Post by **Necromancer** » 28 Dec 2007, 06:43

I did a little research on this before thinking I could turn my T-5 into a
T-5R

What I found wasn't conclusive so I'm still not sure that you don't have an extra hose running to the turbo that I do not have.

As far as I can remember, I have three small vacum lines that run from the area of the air cleaner box to the turbo.
Perhaps you have a fourth and it fell off or has a leak?
I also know that it's criticle (at least for performance) that these lines are connected up correctly. Perhaps you had someone service the car recently and misplaced these lines?
Do a search as I remember there being a diagram on this site on how they should be connected.

Necromancer · Post by **Necromancer** » 30 Dec 2007, 19:28

The only other thing that I can suggest is to 'shut down the system', i.e. remove the negative battery cable for a few hours.
This should reset the computer(s) and might be worth a shot.
Make sure that you have your radio code as you will need it once you reconnect the battery.