How does a JRSC regulate boost?
10-03-2003, 08:09 PM
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How does a JRSC regulate boost?
I read everything on their website and I'm still wondering how it stops at a certain boost level? It seems it would keep rising while the engine rpm's go up, how is it regulated?
10-03-2003, 08:17 PM
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Re: How does a JRSC regulate boost? (sporkcrx)
I want to type it out in my own words for you, but I do not have the time right now. So here it is copied and pasted:
Turbos use a wastegate to bleed off the exhaust gasses driving the turbo when the desired boost level is reached. What this means is that turbos run a fixed boost level, at least in theory. In a perfect world, a turbo system with the wastegate set at 6 psi would make 6 psi of boost under all wide-open-throttle conditions. A supercharger, by contrast, runs a fixed speed relative to the engine. If a supercharger is geared to pump 1.5 times more air than the car breathes naturally aspirated, the boost will be different at different rpm. In the parts of the rev range where the engine doesn't breathe well, the supercharger's insistence on pumping air will cause air to pile up in the manifold, increasing more pressure. In areas where the engine does breathe well, there will be less of a back-up, and less boost. The end result is that turbochargers tend to simply magnify the stock powerband of the engine they are attached to, while superchargers are more likely to totally change the powerband to reflect the characteristics of the supercharger.
Hopefully that will help you... Oh ya, to change the amount of boost on a s/c you simply add a heavier pound pulley.
Turbos use a wastegate to bleed off the exhaust gasses driving the turbo when the desired boost level is reached. What this means is that turbos run a fixed boost level, at least in theory. In a perfect world, a turbo system with the wastegate set at 6 psi would make 6 psi of boost under all wide-open-throttle conditions. A supercharger, by contrast, runs a fixed speed relative to the engine. If a supercharger is geared to pump 1.5 times more air than the car breathes naturally aspirated, the boost will be different at different rpm. In the parts of the rev range where the engine doesn't breathe well, the supercharger's insistence on pumping air will cause air to pile up in the manifold, increasing more pressure. In areas where the engine does breathe well, there will be less of a back-up, and less boost. The end result is that turbochargers tend to simply magnify the stock powerband of the engine they are attached to, while superchargers are more likely to totally change the powerband to reflect the characteristics of the supercharger.
Hopefully that will help you... Oh ya, to change the amount of boost on a s/c you simply add a heavier pound pulley.
10-03-2003, 09:15 PM
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Re: How does a JRSC regulate boost? (GudeH23a)
Ahhhh I see. That explains why my buddies prelude hit vtec, the boost would drop. So the charger really is spinning faster and faster with the engine, but as the breathing becomes better the less pressure is held in the manifold. It's the weight of the pulley that raises the boost? I thought it was a smaller diameter one?
10-03-2003, 09:19 PM
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Re: How does a JRSC regulate boost? (sporkcrx)
These seems backwards to me... at least what I've seen from dyno plots, maybe it's just the spool lag:
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote »</TD></TR><TR><TD CLASS="quote">The end result is that turbochargers tend to simply magnify the stock powerband of the engine they are attached to, while superchargers are more likely to totally change the powerband to reflect the characteristics of the supercharger. </TD></TR></TABLE>
-PHiZ
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote »</TD></TR><TR><TD CLASS="quote">The end result is that turbochargers tend to simply magnify the stock powerband of the engine they are attached to, while superchargers are more likely to totally change the powerband to reflect the characteristics of the supercharger. </TD></TR></TABLE>
-PHiZ
10-03-2003, 09:23 PM
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Re: How does a JRSC regulate boost? (MachAF)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by MachAF »</TD></TR><TR><TD CLASS="quote">Its diameter. not weight</TD></TR></TABLE>
Sorry about that, when i said heavier pound i meant 8psi pulley vs 11psi pulley. Thank you for making that clearer though, the diameter's of the pulley do change when going up in boost pressure.
Sorry about that, when i said heavier pound i meant 8psi pulley vs 11psi pulley. Thank you for making that clearer though, the diameter's of the pulley do change when going up in boost pressure.
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10-03-2003, 10:17 PM
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Re: (guido-kp)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by guido-kp »</TD></TR><TR><TD CLASS="quote">while we are asking, whats the lil black canister that looks like a wastegate actuator on the jrsc? i dunno how to describe it better...</TD></TR></TABLE>
That's the bypass valve. It is vacuum actuated and allows for part throttle, off boost operation.
That's the bypass valve. It is vacuum actuated and allows for part throttle, off boost operation.
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