belt slipping and loosing boost - Ford Mustang Forums : Mustang Forum
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post #1 of 3 Old 04-20-2011, 07:54 PM Thread Starter
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belt slipping and loosing boost

ever since i put on a pulley and had it dyno tuned at Brenspeed I've had a problem that if i get on it that once in a while the belt feels like its slipping and i see the boost gauge drop and hop loosing lots of horsepower.

I'm only pushing 537 to the rear wheels and I don't have much done. vmp pulley, metco idler, JLT intake, and whipple throttle body are all that are done performance wise.

its slowly gotten worse to. I dynoed it in November right before i stored it for winter and it only happened once on the drive home. now that i took it out finally a few weeks ago its getting worse.

does anyone have any ideas as to what it might be? it might not be the belt slipping but it sure feels like it I donno. does anyone know what this probably is? could it be a bad belt or possibly the tensioner going bad slowly? i thought about a heavy duty tensioner and new belt but don't want to spend 300 or so if its not the problem. I'm stumped any help would be greatly appreciated.

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post #2 of 3 Old 04-20-2011, 09:14 PM
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I prefer the VMP 90 mm stealth idler to the other styles. I'm up in the mid 600's and no issues with belt slip.

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post #3 of 3 Old 04-21-2011, 11:58 AM
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My guess is that you need to put an idler pulley of some kind on there. The problem with using a smaller pulley is you get less surface area contact when the belt is routed in the factory route path. An idler pulley will wrap the belt around the smaller pulley a little better for more contact.

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