Deleting secondary throttle plates?

[Paul Workman]

Still climbing the leaning curve here...

Just learning more about our LT5s, I see that in some cases the secondary throttle plates are removed for improved performance (presumably). I found this interesting, as at first blush there seem to be several possible locations for trouble to develop - what with having 4 discrete signals required from the ECM to the respective injector (pair) relay to allow the secondary injectors to work (in pairs), the mechanical issues inherent with the secondary throttle plates and the acuation thereof, etc, etc.

The obvious advantage would be the "kiss principle", I recon, but I would appreciate some enlightenment on this particular procedure, and how it is accomplished e.g. are all injectors running "full time"? What does this do to the torque curve by comparision, etc, etc?

In other words...What is the problem and how well does this procedure address it?

P.

[bradslt5]

I would love to do this also. from what i hear you lose just a little low end but that is all i know . i would sure like to learn how to do this i get so tired of messingf with and spending money on this set up the way it is . i wouldnt mind the little trade off in low end for the simple operation of no secondaries .

[petefias]

You need a new chip that runs all 16 injectors. Any good tuner could do that for you. Give Marc Haibeck a call. He could do a 415 for you to help out on the low end.

You may give up a little on the low end on a stock motor, but you won't have to deal with all the vacum lines, actuators, trouble codes.

Well it's easy, but it's not. You can do a couple of things.

1) Remove the scondary butterflies entirely and you will have to fill the holes where the shafts go. But you can open up the ports a bit more as a result.

2) Zip tie the secondary system open and leave the butterflies in.

Then you need to go in and turn all 16 injectors on, but you still need to run a vacuum line to the solenoid so the system "thinks" it's still operational. Plus a few other small tuning tricks.

Rob and I were going to do a write up on it, but he grenaded his rear end. So it got pushed a little down the line.

[GOLDCYLON]

Is there really that much HP gained on a base 350? I would not think so?

[We Gone]

See if you can get ShawnZR1 over on CF to post his views... he took his out a while back.. 350 P&P with headers..

[kenthompson]

Originally Posted by Jeffvette

2) Zip tie the secondary system open and leave the butterflies in.

Then you need to go in and turn all 16 injectors on, but you still need to run a vacuum line to the solenoid so the system "thinks" it's still operational. Plus a few other small tuning tricks.

Jeff, why do you need to turn them on, would they not still be active if the switch is on, RPM is met, TPS is far enough, etc, etc? I don't remember a switch or a position sensor on the secondary system. I agree that the solinoid must remain active for the system to work reasonably well.

KT

[Pete]

My testing resulted in 5 RWHP gain and cleaned up nicely under the plenum.
Use Dorman freez plugs #555-108.

You won't feel the difference,espacially with stock small ports.
I felt no differance and my ports are huge for a 350ci,come drive it yourself.

On a totally stock chip our secondaries will open as low as 1500 rpm at WOT.

Yank them.
Benefits: FREE HP
Drawbacks: Nothing you will notice.

Pete

[ShawnZR-1]

Originally Posted by Pete

My testing resulted in 5 RWHP gain and cleaned up nicely under the plenum.
Use Dorman freez plugs #555-108.

You won't feel the difference,espacially with stock small ports.
I felt no differance and my ports are huge for a 350ci,come drive it yourself.

On a totally stock chip our secondaries will open as low as 1500 rpm at WOT.

Yank them.
Benefits: FREE HP
Drawbacks: Nothing you will notice.

Pete

For the most part, I agree. All other things being the same, you probably won't feel a difference one way or the other. I can't really say I've lost low end torque. I can still pull in 6th gear from 55 on up.

IMO, the biggest advantage is losing all of the moving parts and vacuum lines under there! Fewer things that could go wrong is a good thing in my book!

[lbszr]

Is the outboard end of the throttle shaft hole a deadend or does it need plugged as well as the inboard end?

And can they be removed without removing the breather box?

Originally Posted by Pete

My testing resulted in 5 RWHP gain and cleaned up nicely under the plenum.
Use Dorman freez plugs #555-108.

You won't feel the difference,espacially with stock small ports.
I felt no differance and my ports are huge for a 350ci,come drive it yourself.

On a totally stock chip our secondaries will open as low as 1500 rpm at WOT.

Yank them.
Benefits: FREE HP
Drawbacks: Nothing you will notice.

Pete