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Joined: Oct 2000
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These are the plain facts as witnessed by me and my gauge. Ok, Jim, I agree I can't argue with a gauge. Anyone have any theories here? A supercharger will have its flow rate fixed by it impeller speed, ie by engine speed. So, new or old exhaust, flow rate (cfm) will be constant for a given engine speed. How could intake manifold pressure increase under constant flow rate conditions? -Kurt
-Kurt
"I'm a little sceptical of that internet thing. After all, what's it got besides information?"
-DB, 1/97
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Joined: Jun 2000
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Originally posted by Munson:
Ok, Jim, I agree I can't argue with a gauge.
Anyone have any theories here? A supercharger will have its flow rate fixed by it impeller speed, ie by engine speed. So, new or old exhaust, flow rate (cfm) will be constant for a given engine speed.
How could intake manifold pressure increase under constant flow rate conditions?
-Kurt CFM is not constant because you changed the flow out of the motor by changing the exhaust restriction. This changes the efficiency of the entire system. The higher boost of the new system comes from more restriction, but would also change the scale on the SC/engine efficiency. The more open Magnaflow system he removed must have been out of his efficiency range if he truly is making more power now because the boost went up, not down. Only if you're maxing out the SC flow rating are you going to see a constant anything at any RPM. Even still, you change one part of the system to flow more or less and the air flow will change one way or the other because you changed the efficiency...
Brad Noon '99 SE MTX 3 point oh my God H.O. 179HP/178TQ BNMotorsports Floormats, powder coating, TB optimizing, Gutted cats, etc BNMotorsports is now the preferred distributor of Contour/SVT/Mystique Indiglo style gauges!!!bnmotorsports@msn.com
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Joined: Jun 2000
Posts: 3,248
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The more open Magnaflow system he removed must have been out of his efficiency range if he truly is making more power now because the boost went up, not down. Why do you assume the Magnaflow is more open. Seems more plausable that it wasn't..
1999 Amazon Green SVT Contour (#554/2760)
Stock SVT Duratec V6 with:
Intake- K&N filter/75mm MAF meter
Exhaust- MSDS Y-pipe/Bassani catback
Durability-Ford "dual mode" damper, Mobil 1/K&N oil filter
179.2 FWHP at 6900 RPM
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Joined: Dec 2001
Posts: 125
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Joined: Dec 2001
Posts: 125 |
In learning a little more. I think bnoon is close to accurate. The Magnaflows were louder, so probably less restrictive. My Bassani has the silencers in the tail pipes, so is considerably quieter. I learned that, in fact, the SC needs the back pressure to make boost. So, if the exhaust was breathing better, than I could see a loss of boost.
I am learning more all the time.
98.5 SVT, Vortech SC, Bassani, Quaiffe, Clutchmasters Stg. 3, BAT Sport Springs/Konis, 17" Momo Arrows, Sparco Brace,BAT 22mm Sway Bar, PIAA fogs & headlights.
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Joined: Jun 2000
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Originally posted by Dan Nixon:
Why do you assume the Magnaflow is more open. Seems more plausable that it wasn't.. Because the boost went up with the new exhaust as the only change. Boost is directly related to the air flow restrictions of the intake, heads, valves, exhaust, etc. Change one to flow more CFM, boost goes down if the flow is above the max speed of the Vortech on the current pulley. What he could have done to see more boost, had he liked the exhaust, was to put on a smaller pulley to bring boost back up and actually get more power at the same boost levels. With all of Buckshot's mods, he dropped one pulley size to get back to 9psi when the blow off valve is rated for 10. He had a smaller one yet in the back of the car to put on IIRC to get it up to 10 a little sooner in the RPM range to make useable boost on the larger motor.
Brad Noon '99 SE MTX 3 point oh my God H.O. 179HP/178TQ BNMotorsports Floormats, powder coating, TB optimizing, Gutted cats, etc BNMotorsports is now the preferred distributor of Contour/SVT/Mystique Indiglo style gauges!!!bnmotorsports@msn.com
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Joined: May 2000
Posts: 1,355
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Originally posted by Terry Haines:
3" 'front to back' as the Sierra Cosworth twin-cam,single pipe ,no 'quasi-duals' waste of time ,money and weight!!..My 2 cents!!! OOhhhhh Sierra Cosworth...now there's a car that I wish was over here! Sorry, wrong subject.
Simon W. Las Vegas.
96 SE V6 MTX Tereador Red (1st Blown Engine, better be the last!)
1999 SVT Engine
SVT Exhaust w/custom DTM Tips and optimized Y-pipe and no Res (thanks to Po-Jay!). LSD Quaife(thanks to Terry!), SCA CAI w/KKM, Grizzly clutch, FMS 9mm wires, Airknights custom short shifter.
"You can only get more rice at one time by ordering Chinese" - Davo7SVT
"it's only nuts and bolts" - Terry Haines
"Drive it like you stole it" - Me!
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Joined: Jun 2000
Posts: 3,248
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Posts: 3,248 |
Change one to flow more CFM, boost goes down if the flow is above the max speed of the Vortech on the current pulley. Ahhh, me learn too! 
1999 Amazon Green SVT Contour (#554/2760)
Stock SVT Duratec V6 with:
Intake- K&N filter/75mm MAF meter
Exhaust- MSDS Y-pipe/Bassani catback
Durability-Ford "dual mode" damper, Mobil 1/K&N oil filter
179.2 FWHP at 6900 RPM
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