Posted: 3/16/2012 10:38:31 AM EDT
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It seems there's ALOT more knowledgeable people here then the guys at SVT foums.
Installed my 2.4l KB in my 03 cobra and reflashed the car with a SCT tuner. I went to start the cobra for the first time after checking and rechecking all the hoses and lines. Started it and it instantly jumped to about 5k and I immediately shut the car off. Went a double checked everything and it was all good. Checked the throttle cable and throttle body and there is some play in the line. Tried starting it agian and same thing. And shut her off. Seems like it wants to idle around 4500 rpm. Only thing i can find on the net is people saying its the OEM throttle body causing this issue. I cant see how it would. Mods are: Kb 2.4l Oem throttle body Steeds intake 60lb injectors Diablo mafia SCT X3 Boost a pump 40amp Those are the only related motor mods. |
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This Bell SC is always turning, right? Meaning no electric clutch. When you don't need boost, there is a bypass which recirculates flow so the MAF is low. When you need boost, this bypass closes, causing pressure downstream of the supercharger to build. This device isn't opening. Meaning it is building boost. Since these KB SCs are positive displacement, you are essentially running at the sonic limit for the throttle body. |
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Supercharger bypass isn't working. This causes the supercharger to boost through the throttle body. I checked the Bypass function when it was out and it seems like it was working. Im deffinitly not ruling it out. i DID connect the valve at the top to my boost line. not sure if that would cause an issue. valve im talking about at the top did it like this lol 
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Quoted: Quoted: Supercharger bypass isn't working. This causes the supercharger to boost through the throttle body. I checked the Bypass function when it was out and it seems like it was working. Im deffinitly not ruling it out. i DID connect the valve at the top to my boost line. not sure if that would cause an issue. valve im talking about at the top http://t2.gstatic.com/images?q=tbn:ANd9GcSEBrKXTkPPfdrDr8cs5kQbZDOjM5_TnGG4AWVzxZrSfP-uyKQVk-UdGDXy did it like this lol http://i223.photobucket.com/albums/dd205/Quicktime_GT/DIAGRAM.png So is the valve OPEN when the throttle body butterfly valve is closed in the idle position? Because it should be. This way, idle and part-throttle is running with normal engine vacuum, 10-17 inches of mercury. This pressure is the same as the vacuum to the fuel pressure regulator. I believe the SC bypass valve is connected to PORT vacuum, not MANIFOLD. Port comes from the throttle body and represents the velocity of the intake through the throttle body, analogous to mass flow rate. |
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Ask Kenne Bell  Quoted:
ETA: Reread your post, looks like you are on point... Called Kenne bell and they said OEM throttle body should work no issues. Not ruling it iout either but this is the only simmilar issues that im having but i dont know if it got resolved or not. http://www.modularfords.com/f17/kenne-bell-install-question-4k-idle-49356/ |
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So is the valve OPEN when the throttle body butterfly valve is closed in the idle position? Because it should be. This way, idle and part-throttle is running with normal engine vacuum, 10-17 inches of mercury. This pressure is the same as the vacuum to the fuel pressure regulator. I believe the SC bypass valve is connected to PORT vacuum, not MANIFOLD. Port comes from the throttle body and represents the velocity of the intake through the throttle body, analogous to mass flow rate. I cant really check for open or close position when its at ilde cause its idling at almost 5K. But when i do press on the bypass arm it works and makes a suction sound and when i let go it goes back to its origonal position. |
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Quoted: Quoted: So is the valve OPEN when the throttle body butterfly valve is closed in the idle position? Because it should be. This way, idle and part-throttle is running with normal engine vacuum, 10-17 inches of mercury. This pressure is the same as the vacuum to the fuel pressure regulator. I believe the SC bypass valve is connected to PORT vacuum, not MANIFOLD. Port comes from the throttle body and represents the velocity of the intake through the throttle body, analogous to mass flow rate. I cant really check for open or close position when its at ilde cause its idling at almost 5K. But when i do press on the bypass arm it works and makes a suction sound and when i let go it goes back to its origonal position. With the engine off, is the valve open or closed? What is the vacuum/pressure to the valve with the engine running? |
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So is the valve OPEN when the throttle body butterfly valve is closed in the idle position? Because it should be. This way, idle and part-throttle is running with normal engine vacuum, 10-17 inches of mercury. This pressure is the same as the vacuum to the fuel pressure regulator. I believe the SC bypass valve is connected to PORT vacuum, not MANIFOLD. Port comes from the throttle body and represents the velocity of the intake through the throttle body, analogous to mass flow rate. I cant really check for open or close position when its at ilde cause its idling at almost 5K. But when i do press on the bypass arm it works and makes a suction sound and when i let go it goes back to its origonal position. With the engine off, is the valve open or closed? What is the vacuum/pressure to the valve with the engine running? Boost gauge reading 20 VAC. Should it be reading boost if its at 4500-5K RPM? ?? |
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Quoted: Quoted: Quoted: Quoted: So is the valve OPEN when the throttle body butterfly valve is closed in the idle position? Because it should be. This way, idle and part-throttle is running with normal engine vacuum, 10-17 inches of mercury. This pressure is the same as the vacuum to the fuel pressure regulator. I believe the SC bypass valve is connected to PORT vacuum, not MANIFOLD. Port comes from the throttle body and represents the velocity of the intake through the throttle body, analogous to mass flow rate. I cant really check for open or close position when its at ilde cause its idling at almost 5K. But when i do press on the bypass arm it works and makes a suction sound and when i let go it goes back to its origonal position. With the engine off, is the valve open or closed? What is the vacuum/pressure to the valve with the engine running? Boost gauge reading 20 VAC. Should it be reading boost if its at 4500-5K RPM? ?? No, there isn't a load on the engine. You need to determine if the supercharger bypass is closed without throttle application. If it is open, there is the problem. The equilibrium of the engine speed, at any range, is determined by the mass flow and load. All it takes to get 4500 RPM without a load is a tiny increase in mass flow rate. When you blip the throttle in neutral, the increase in engine speed is slowed by the inertia of the engine+flywheel+accessory drives. But if you slowly accelerate the engine in neutral, manifold pressure (vacuum, in most cases) will stay the same. In your case, checking the idle air control valve is another must. |
