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Re: High boost shudder ! Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Wed, 10 Sep 2003 09:27:29
In Reply to: High boost shudder !, Sam, Tue, 9 Sep 2003 19:30:47 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Fuel cut-off usually doesn't feel like a shudder - it feels like the engine just quits. At full boost, you know fuel shut-off because it can just about throw you into the windshield.
I'd look at spark plugs - make sure they're the right kind, and the RIGHT GAP. The higher the boost level, the harder it is for a spark to jump the gap. If the gap is too big, it won't jump at high boost, and you'll get a misfire that feels a lot like a shudder.
You also mention that the car is boosting well into the red. Unless your boost gauge is wrong, that's probably too high. I assume there may have been some modifications. You also may be getting into detonation (knock) at very high boost. Yes, the APC should address that, but it doesn't work as smoothly at higher boost levels.
I would check your plugs. Make sure they are the exact right NGK's as specified in the manual - no substitutions. Make sure the gap is exactly right - measure it, don't assume it's right from the box. A little tigher won't hurt.
However, if you're running well above 'design' boost levels, you may be exceeding the design ignition capability of the system to produce a good spark.
posted by 192.249....
, Wed, 10 Sep 2003 09:27:29 <-- Viewing This Message
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