SC GUYS ONLY... UPCOMING PRODUCT.. GAUGING INTEREST.....
08-29-2006, 02:57 AM
#124
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Scion Evolution
Join Date: Oct 2005
Location: Andersen AFB, Guam
Posts: 5,277
Originally Posted by navylife59
Does anyone actually have boost gauge readings at the TB on the TRD setup? I'm barely cracking 5PSI on a 9 PSI pulley.
09-04-2006, 05:19 PM
#131
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Join Date: Dec 2005
Location: Fort Worth, texas
Posts: 55
!
I created a vacuum distribution manifold and replumbed the vacuum lines. I added 3 more shims to my TurboXS RPV-25. It seems to be running smoother, but still no 9PSI. I plan on converting to a BOV once I get my Greddy Ultimate with the MAP sensor installed tomorrow. So long MAF. I am also goign to try to find a smaller belt and see if anything changes.
I have been asking about peps with headers and s-pipes and their PSI/Hg readings specifically for a reason. A while back on some forum there was a discussion about PSI loss after a header install. The initial theory was that back pressure was needed to make boost. It was discounted by many as another problem. I, however, cannot discount the fact that there is some physics to back up that notion. Albeit not an inversly proportional relationship between intake boost and backpressure exhaust as in turbo applications, there is an indirect relationship between these two functions with supercharged applications.
First, let's discuss the turbo application. Turbo boost pressure is directly proportional to exhaust system pressure. The more flow that a system has, the more energy that can be absorbed by the turbine impeller. A restrictive exhaust system creates more backpressure which equates to less energy for the turbine. It is important to note that as the exhaust system backpressure is decreased (more energy) the turbine becomes more efficient (overcoming impeller weight, bearing friction, and centrifugalforces).
S/C differ as in they utilize direct mechanical energy from the engine. Depending on your type and application, the boost pressure is directly proportional to engine speed until the BPV or BOV opens. You get a linear boost curve that is very predictable. WWII fighter planes had 2-stage superchargers that allowed 2 different boost levels for low and high altitude flight. Modern automotive applications do not so as to make the system more reliable and cheaper. Also the engines utilizing this setup were mainly Merlin V-12 engines producing over 2,000 HP. Hmmm, a tC with a Merlin?
Now we need to discuss valve overlap or cam duration. N/A engine benefit greatly from a higher duration camshaft, especially, on high compression engines (higher cylinder pressures). At the point of valve overlap in the cam timing (duration), blow-thru occurs. This blow-thru allows the low pressure exhaust side (assuming a properly designed and tuned exhaust) to evacuate the cylinder bore, thusly, drawing in a larger amount of intake charge. Turbos benefit bacause the wastegate will allow more energy to be scavenged from the exhaust flow to keep the cylinder pressure maintained. This is why turbo applications can benefit from camshafts with higher durations. S/C cannot because the amount of boost is directly proportional to crankshaft rotation. There is not a marketed (it can be done) method to increase the S/C's boost output to maintain the desired cylinder pressure. S/C applications benefit from higher lift camshafts and not duration.
In a nutshell, this is only a hypothesis. I have done no testing or researched such . The thought is simply if an exhaust system were to be tuned to allow a lower pressure to reside at the collector and create more blow-thru at valve overlap (assuming sufficient duration), then there would be a proportionate reduction in cylinder pressure. This must be overcome by increasing the amount of pressure in the intake charge. The turbo can, the S/C cannot unless a smaller pulley is installed.
I am no physics major, but I did sleep with one at a Holiday Inn Express!!!
I have been asking about peps with headers and s-pipes and their PSI/Hg readings specifically for a reason. A while back on some forum there was a discussion about PSI loss after a header install. The initial theory was that back pressure was needed to make boost. It was discounted by many as another problem. I, however, cannot discount the fact that there is some physics to back up that notion. Albeit not an inversly proportional relationship between intake boost and backpressure exhaust as in turbo applications, there is an indirect relationship between these two functions with supercharged applications.
First, let's discuss the turbo application. Turbo boost pressure is directly proportional to exhaust system pressure. The more flow that a system has, the more energy that can be absorbed by the turbine impeller. A restrictive exhaust system creates more backpressure which equates to less energy for the turbine. It is important to note that as the exhaust system backpressure is decreased (more energy) the turbine becomes more efficient (overcoming impeller weight, bearing friction, and centrifugalforces).
S/C differ as in they utilize direct mechanical energy from the engine. Depending on your type and application, the boost pressure is directly proportional to engine speed until the BPV or BOV opens. You get a linear boost curve that is very predictable. WWII fighter planes had 2-stage superchargers that allowed 2 different boost levels for low and high altitude flight. Modern automotive applications do not so as to make the system more reliable and cheaper. Also the engines utilizing this setup were mainly Merlin V-12 engines producing over 2,000 HP. Hmmm, a tC with a Merlin?
Now we need to discuss valve overlap or cam duration. N/A engine benefit greatly from a higher duration camshaft, especially, on high compression engines (higher cylinder pressures). At the point of valve overlap in the cam timing (duration), blow-thru occurs. This blow-thru allows the low pressure exhaust side (assuming a properly designed and tuned exhaust) to evacuate the cylinder bore, thusly, drawing in a larger amount of intake charge. Turbos benefit bacause the wastegate will allow more energy to be scavenged from the exhaust flow to keep the cylinder pressure maintained. This is why turbo applications can benefit from camshafts with higher durations. S/C cannot because the amount of boost is directly proportional to crankshaft rotation. There is not a marketed (it can be done) method to increase the S/C's boost output to maintain the desired cylinder pressure. S/C applications benefit from higher lift camshafts and not duration.
In a nutshell, this is only a hypothesis. I have done no testing or researched such . The thought is simply if an exhaust system were to be tuned to allow a lower pressure to reside at the collector and create more blow-thru at valve overlap (assuming sufficient duration), then there would be a proportionate reduction in cylinder pressure. This must be overcome by increasing the amount of pressure in the intake charge. The turbo can, the S/C cannot unless a smaller pulley is installed.
I am no physics major, but I did sleep with one at a Holiday Inn Express!!!
09-05-2006, 06:29 PM
#133
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Hey guys sorry for the delay in dyno, I broke a supercharger mount and am fighting with the dealer for them to replace it. Hopefully it will be in asap or I will have the current welded.
09-05-2006, 06:47 PM
#134
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Join Date: Aug 2005
Location: Fairfax, VA
Posts: 34
Originally Posted by Garage1217
Hey guys sorry for the delay in dyno, I broke a supercharger mount and am fighting with the dealer for them to replace it. Hopefully it will be in asap or I will have the current welded.
Sorry, I dont mean to thread jack!
09-06-2006, 03:31 AM
#136
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Join Date: Dec 2005
Location: Fort Worth, texas
Posts: 55
Re: !
Originally Posted by ryno379
Originally Posted by navylife59
I am no physics major, but I did sleep with one at a Holiday Inn Express!!!
After reading all that, this is what I came away with.
09-07-2006, 05:06 PM
#138
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Yo guys, Just so you know I am not feeding you guys crap, Here is the bracket I broke welded up finally. Will start putting it back together tommorow. I am just as excited as all of you to hit the dyno!
