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Boost drops off high rpm

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Old 02-06-2010 | 01:53 PM
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Default Boost drops off high rpm

Well got my S/C ride out for the first time. Is the boost level supposed to peak then drop off as the revs increase? I start to see boost down around 2000 - 2500 rpm, peaks at about 6 psi at around 4000 - 4500 and then drops off to 2 - 3 psi at redline. Is this normal? Is is a Vortech V2 with a 3.12 pulley. I am thinking in theory at that point the engine is sucking in air faster then the S/C can supply it.
Old 02-06-2010 | 02:02 PM
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Have you verified that there is no belt slipage?

Ken
Old 02-06-2010 | 03:16 PM
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I don't hear any squealing or anything and the belt is pretty tight, but it is new with only a couple of hours run time. I also have tons of belt wrap on both the S/C and crank pulleys. I will see how much tighter I can get it.

Old 02-06-2010 | 03:35 PM
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Is this a centrigual supercharger ?
Old 02-06-2010 | 05:14 PM
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Yes it is centrifugual. The belt was a bit loose, I will let you know how the next test drive goes.
Old 02-06-2010 | 05:28 PM
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I had the same problem when I first put on the sc. The belts need to be very tight, more then
I felt comfortable at first...
Old 02-06-2010 | 05:31 PM
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Be careful and don't over tighten the belt. I did that on my 1st belt and the belt shredded within the first 100 miles or so.

Check your blow off valve. Make sure it is closing as vacumm is decreased and/or positive pressure is applied. I had a bad valve and it didn't close which caused lower boost numbers at high RPM.
Old 02-06-2010 | 06:23 PM
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As said above, the belt needs to be a heck of a lot tighter than any other acessory belt. Almost as tight as a guitar string. You shoud be able to tell if the belt is slipping, by looking at the painted part number on the back. It takes a while before it wears off, but if the belt is slipping, you'll se the signs pretty much right away.
Old 02-06-2010 | 10:28 PM
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Originally Posted by Imo000
As said above, the belt needs to be a heck of a lot tighter than any other acessory belt. Almost as tight as a guitar string. You shoud be able to tell if the belt is slipping, by looking at the painted part number on the back. It takes a while before it wears off, but if the belt is slipping, you'll se the signs pretty much right away.
Yes, I too run my SC belt much, much tighter that the other belts. And to explain a little further, when my blow off valve malfunctioned I kept cranking down on the tensioner for the SC belt thinking I was not producing boost because the belt was slipping.

Another item to check is making sure there is nothing blocking or restricting air flow into the blower.
Old 02-06-2010 | 10:56 PM
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Just an observation, and I'll be the first to admit I'm not familiar with the install, but it appears that you are running the tensioner on the tensioned (crank pulling) side of the belt. I would think that it would be ideal to have the tetioner on the detensioned side. space constraints and belt routing may dictate tensioner location and this may be your only option but I think it will be less likely to slip if you can reroute the belt so the tensioned side has the streight run and the tensioner rides on the slack side of the belt.
Old 02-06-2010 | 11:19 PM
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Originally Posted by 76FJ55
Just an observation, and I'll be the first to admit I'm not familiar with the install, but it appears that you are running the tensioner on the tensioned (crank pulling) side of the belt. I would think that it would be ideal to have the tetioner on the detensioned side. space constraints and belt routing may dictate tensioner location and this may be your only option but I think it will be less likely to slip if you can reroute the belt so the tensioned side has the streight run and the tensioner rides on the slack side of the belt.
I think you are right but the kit came like that. But Ted made some neat modfications to eliminate the need to run the PS pump on the SC belt (as per the orginal kit) and got way more wrap around the SC and the crank pulley. but he can explain it better than I can.
Old 02-07-2010 | 02:24 AM
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Yes, the tensioner original design is on that side however it is reversible. I may experiment putting it on the other side and see if I can make it work. I have more space constraints on the other side though.




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