Question (probably a repeat...)

DriftingThunder

Registered User
I was going to do a search but had no idea what to put in for search keywords so bear with me please. :p

Alrighty, I was told that by capping off this line I could pick up maybe just a couple ponies and see quicker boost response:
1.jpg


Well, I did it and I didn't notice a power difference, though I didn't expect to as small as it would be, but I also didn't see quicker boost response because I have a 10% pulley and my belt slips when I get on the throttle. So my experience with this is inconclusive thus far. With the 10% I am making at least 16 psi and with that kind of boost pressure I eventually blew off my line cap so I put the full line back on. Scott Long blew his off while equipped with a 10% on his silver auto SC also.

So I was curious, just what exactly does capping that line off do? Does it really add maybe one or two ponies while quickening boost response?

:confused:
Thanks in advance!
 
All you will do is.........

Put the line back on.....The line is there to prevent cavatation of the rotors and balance the pressures between the inlet and return plenums. The bypass valve does the same thing, and under no-boost conditions, it allows the car to have somewhere to go.

You can damage the blower with that line off. Re-install it and have fun with the car.

P.S. Are you running exhaust mods for that 10% pulley you have. If not, borrowed time!!!!



Don
 
I tried capping mine off a couple years ago and all it did was make the bypass valve super sensitive. Barely touch the gas pedal and the bypass would close and the supercharger would whine. It got pretty annoying after a couple days.

The car wasn't any faster, so I put the hose back on.

David
 
I already did put the line back on, I only had it capped for a couple of days then it popped off so I put the line back on. In theory it is a boost leak but I understand the necessitation now. Is necessitation a word? :)

I am running all 2 1/4" aftermarket exhaust except for manifolds. Stock manifolds, SCP downtubes, x-pipe style exhaust and Dynomax mufflers. I think it sounds really nice by the way but it's way too quiet for me. Needs headers?

Either way I'm putting a stock '89-'93 SC blower pulley on soon.
 
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I have had mine like that for 2 years now, and I didn't really notice any power difference but it seemed like it'd jump up to 10 psi as soon as I barely got on it enough to close the bypass valve.

Now the other day I put a different blower on my car. It had no pulley and I just happened to have a 10% overdrive laying around, so I used that pulley. I get down to the hangout and Andy told me that his blew off the vacuum cap. I pop my hood and sure enough mine did too. It never did that with the stock pulley. I chucked the hose. What is the diameter of the hose that will fit? I'll just go buy 6" of hose and reconnect it myself w/ two small clamps.
 
DriftingThunder said:
I already did put the line back on, I only had it capped for a couple of days then it popped off so I put the line back on. In theory it is a boost leak but I understand the necessitation now. Is necessitation a word? :)

I am running all 2 1/4" aftermarket exhaust except for manifolds. Stock manifolds, SCP downtubes, x-pipe style exhaust and Dynomax mufflers. I think it sounds really nice by the way but it's way too quiet for me. Needs headers?

Either way I'm putting a stock '89-'93 SC blower pulley on soon.

Instead of changing the supercharger pulley, change the jackshaft pulley to a 5% overdrive. That way the diamater of the pulleys are not reduced and there will be much less belt slippage.

David
 
We think even with his open exhaust and double IC that his car is pulling timing. It is a 94 blower w/ 10%, raised top, double IC w/ fan, true dual exhaust. It just doesn't pull very hard after like 3000 rpms. Maybe its because it still has stock 2.73 gears? But I think his computer is pulling timing. He now has a 89 pulley to put on it so maybe we will notice it making a difference up high? Might lose a little bit of low end torque, but thats nothing that the gear swap won't fix.
 
Scott Long said:
Now the other day I put a different blower on my car. It had no pulley and I just happened to have a 10% overdrive laying around, so I used that pulley. I get down to the hangout and Andy told me that his blew off the vacuum cap. I pop my hood and sure enough mine did too. It never did that with the stock pulley. I chucked the hose. What is the diameter of the hose that will fit? I'll just go buy 6" of hose and reconnect it myself w/ two small clamps.
Scott, the line is a different size at each end so it might actually be a smidge hard to get one unless you get the OEM piece. So you didn't notice you blew off your cap? I was GTechin my car when it happened so my power just degraded massively as I developed a huge boost leak when it came off. It sucks too cuz that was a nice run up to that point. Scared the bajeezes out of me because when mine flew off it made a loud popping noise so I thought I might've blown up the head gaskets in an explosive manner or something (I'm still a n00b).

I had read about getting jackshaft pulleys and whatnot but I was gonna just leave the belt in a slipping state because it's so much easier on the car. I was looking at the belt size and I'm pretty certain it's the stock 94/95 belt on a 10% pulley. It seems very snug when I checked it but it slips, and I wanna keep it that way for as long as I have the 10% on there.

EDIT: Oh yeah, Scott, what is the peak boost pressure on your SC with the 10%?
 
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Stock '89 SC pulley

Andy, did you put that '89 pulley on your SC? If so, did you notice any difference?

68COUGAR
 
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