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tpepmeie · 03-12-2008

Dom,
What benefit are you trying to achieve by removing the butterflies? At part throttle, and perhaps full throttle below 3500 rpm, there will be a torque loss. At least up to the 500hp/350 level. I experimented thoroughly a couple of years ago, by datalogging, and clearly saw higher MAP values at cruise with the PTs Open. This is indicative of a loss of torque output.

Others have proven that on a big inch, or even heavily modded out 350, that a full throttle dyno run doesn't necessarily show a torque loss w/ no PTs in place. While I believe that, I have wondered at what RPM the dyno runs started. My observations are that the cross-over point is near 3000-3500 RPM. I suspect that larger displacements will lower than cross-over point.

On all but the most extreme calibrations I do, I have set the Port throttle opening point slightly later than the factory setting. There is a noticeable gain in Part Throttle torque, and have not had anyone complain.

Todd

03-12-2008	#18
tpepmeie Join Date: Aug 2005 Location: Fishers, IN Posts: 792	Re: secondary removal how do you go...... Dom, What benefit are you trying to achieve by removing the butterflies? At part throttle, and perhaps full throttle below 3500 rpm, there will be a torque loss. At least up to the 500hp/350 level. I experimented thoroughly a couple of years ago, by datalogging, and clearly saw higher MAP values at cruise with the PTs Open. This is indicative of a loss of torque output. Others have proven that on a big inch, or even heavily modded out 350, that a full throttle dyno run doesn't necessarily show a torque loss w/ no PTs in place. While I believe that, I have wondered at what RPM the dyno runs started. My observations are that the cross-over point is near 3000-3500 RPM. I suspect that larger displacements will lower than cross-over point. On all but the most extreme calibrations I do, I have set the Port throttle opening point slightly later than the factory setting. There is a noticeable gain in Part Throttle torque, and have not had anyone complain. Todd