[Syty] Overboost

[Bill Calcagno]

If it didn't overboost before the exhaust was changed, and it  
overboosts now that the cat has been removed, the most likely cause  
is the missing cat.  The cat creates a certain amount of backpressure  
that the turbo most overcome while making boost -- without that  
backpressure to slow it down, the turbo will make more boost more  
easily (and probably, too much boost).

If the boost controller hose/tubing was the problem, it would have  
been overboosting before the exhaust work (unless, for some reason,  
you disturbed the hose/tubing while working on something else).   
However, because the hose/tubing is also a common problem, it is  
always worth checking.

If the missing cat is the cause (and I suspect it is), there are two  
ways to address the problem:  First, you can always re-install a cat  
(which is required to be street-legal, but a lot of areas don't  
check).  Second, you can reduce the preload on the wastegate  
actuator, by unscrewing the rod end a couple of turns to lengthen the  
rod -- this is much easier (and cheaper) than re-installing the cat,  
but can increase turbo lag.

		Good Luck,
		Bill

P.S.  You could also install an aftermarket boost controller, but  
that can be expensive and somewhat risky if not adjusted/tuned  
correctly.

On Aug 1, 2007, at 9:53 AM, Marion Cole wrote:

> The most usual suspect is the overboost controller and more  
> specifically, the plastic tube that runs from the turbo body to the  
> controller relay mounted on the toop of the turbo. It is broken  
> fairly easily. Can be replaced with a reinforced rubber hose (such  
> as fuel line hose) but be sure to run a wide circle radius so it  
> does not kink. They probably broke the plastic tube while doing  
> their work (I speak from my own experience J ).
>
>
>
> From: syty-bounces at syty.org [mailto:syty-bounces at syty.org] On  
> Behalf Of Lowell Raison
> Sent: Wednesday, August 01, 2007 7:08 AM
> To: syty at syty.org
> Subject: [Syty] Overboost
>
>
>
> Did a tune up, including replacing the 02 sensor, and replaced the  
> exhaust on the 93 Ty we just bought. Runs great except that at WOT  
> it starts to run strong and then shuts down. It is showing a code  
> 31 Overboost.
>
>
>
> When the shop replaced the exhaust they eliminated the CAT. Is this  
> causing the overboost?
>
>
>
> If so, what is the best solution? Reinstall a CAT?
>
>
>
> Lowell
>
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