Installed CMDP
4th Gear Member
Joined: Dec 2007
Posts: 1,599
From:
Theoretically, the biggest loss is at partial throttle, which won't show up on a dyno plot, it will just show up as decreased fuel economy.
As far as exhaust mods losing torque, it is not back pressure that increases torque. The intake and exhaust have pressure waves that can be in or out of phase in order to help or hurt fill the combustion chamber. Shorter primary tubes in the exhaust help scavenge the exhaust at lower frequencies (lower rpms = torque). The longer primary tubes such as long tube headers provide the best scavenging at higher rpms, not due to reduced restriction, but due to the time it takes for the pressure waves to hit the collector and bounce back. Intake mods are the same. I have never heard of anyone losing torque after porting heads to reduce restriction, but the gains are seen best at higher rpms due to the restriction's increased effects at high mass flow rates.
The butterfly valves in the charge motion plates are only restrictions when they are fully opened. When they are operating at partially closed angles, they are increasing the efficiency by mixing the air and fuel.
As far as exhaust mods losing torque, it is not back pressure that increases torque. The intake and exhaust have pressure waves that can be in or out of phase in order to help or hurt fill the combustion chamber. Shorter primary tubes in the exhaust help scavenge the exhaust at lower frequencies (lower rpms = torque). The longer primary tubes such as long tube headers provide the best scavenging at higher rpms, not due to reduced restriction, but due to the time it takes for the pressure waves to hit the collector and bounce back. Intake mods are the same. I have never heard of anyone losing torque after porting heads to reduce restriction, but the gains are seen best at higher rpms due to the restriction's increased effects at high mass flow rates.
The butterfly valves in the charge motion plates are only restrictions when they are fully opened. When they are operating at partially closed angles, they are increasing the efficiency by mixing the air and fuel.
Thread Starter
6th Gear Member
Joined: Nov 2007
Posts: 6,193
From: Montaner
Gentlemen I do appreciate the info here. There isn't much I can do about this for now. I may try to get the car on the dyno in a couple months. Maybe we can do something about it then.
I took the car out last night and tried stabbing it in first from a 3k roll. At the top of first it starts breaking traction and when I go into second it's spinning. After a second or two it does hook up and keep accelerating. This is pretty much how it was before I put the plates in so I doubt I lost anything where it matters for a race.
I can only speak for my car and my experience. But the best mods so far have been the 4.10 gears, lightweight 18s, and the driveshaft. The pulleys I barely felt but I expected to not gain much there.
The intake/tune and these delete plates have all been disappointing to me in one way or another. Coincidence that these are the two that require tunes? I'm really starting to suspect my car dislikes brenspeed's email tunes.
I took the car out last night and tried stabbing it in first from a 3k roll. At the top of first it starts breaking traction and when I go into second it's spinning. After a second or two it does hook up and keep accelerating. This is pretty much how it was before I put the plates in so I doubt I lost anything where it matters for a race.
I can only speak for my car and my experience. But the best mods so far have been the 4.10 gears, lightweight 18s, and the driveshaft. The pulleys I barely felt but I expected to not gain much there.
The intake/tune and these delete plates have all been disappointing to me in one way or another. Coincidence that these are the two that require tunes? I'm really starting to suspect my car dislikes brenspeed's email tunes.
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tj@steeda
Steeda Autosports
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Sep 10, 2015 08:39 PM
