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.

[Jeffvette]

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]

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]

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!

[petefias]

...need to run a vacuum line to the solenoid so the system "thinks" it's still operational.

Cannot that be programmed out, so it won't throw a code if disconnected?

Why would you want to mess with all those stupid vacum lines, connectors, solenoid, sensor and pump?

The way I see it on the MY95, without the reprogramming, you need at minimum the vacum pump, secondary air inlet solenoid and vacum sensor or you'll get a code during sustained WOT.

Ask me how I know it.

[ShawnZR-1]

Cannot that be programmed out, so it won't throw a code if disconnected?

Why would you want to mess with all those stupid vacum lines, connectors, solenoid, sensor and pump?

The way I see it on the MY95, without the reprogramming, you need at minimum the vacum pump, secondary air inlet solenoid and vacum sensor or you'll get a code during sustained WOT.

Ask me how I know it.

I would think it could be programmed out but it's not in any of the available Tuner* mask files. Maybe Todd would have some insight on this :)

[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?




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

[Pete]

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?


The outbourd hole is a deadend no plug needed,unless you wanna fill it in with something it's only about an 1/8 inch hole.

The breather box does have to come out, unless you don't want your secondary shafts then you can bend the 3 or 4 front ones without taking the breather out.
You will probably remove the breather since most leak then you can silicone it and loctite the screws.

If you decide to do this and keep the secondary solonoid with vacuum pump then i would remove the solonoid from under the plenum
and mount it either close to the differential MAP or vacuum pump with a hard vacuum line they sell at local part stores cheap.
This way if it goes bad, no plenum pulling.

Pete

[lbszr]

The outbourd hole is a deadend no plug needed,unless you wanna fill it in with something it's only about an 1/8 inch hole.

The breather box does have to come out, unless you don't want your secondary shafts then you can bend the 3 or 4 front ones without taking the breather out.
You will probably remove the breather since most leak then you can silicone it and loctite the screws.

If you decide to do this and keep the secondary solonoid with vacuum pump then i would remove the solonoid from under the plenum
and mount it either close to the differential MAP or vacuum pump with a hard vacuum line they sell at local part stores cheap.
This way if it goes bad, no plenum pulling.

Pete

Thanks for info, be pulling soon.

They've been deactivated but secured open, still kicking myself for not removing them last year when the heads were off.

[XfireZ51]

Shawn,

Does yours throw a code with the secondaries out?

[bradslt5]

I am not sure what exactly needs to be done to remove the secondaries . would it be possible to have someone give me a step by step on the removal process.also i am unsure if one must have their prom reprogramed