secondary removal how do you go......

[Pete]

Originally Posted by karterdon

BAck to one of your original questions - accel Injectors??
I got mine from - Atlantic Speed 1/803/548-6990 ask for Scott. Ask if he gives a discount for ZR1 memebrs or Corvette Forum members - He will then give you a discount - I paid $498 for 16 of them.

Part # acc150121

D.Y. 91-#267

That's a good price.

Pete

[bradslt5]

wow, thanx for the info, thats why i love it here ,a bunch of guys sharing and caring enough to help

[XfireZ51]

While we're on the topic of secondary PT removal, Lgaff and myself discussed the idea of just removing the throttle plates and leaving the rest of the linkage in. ECM still thinks secondaries are in. Everything works except no throttle blades in the way. And since we haven't determined yet how to bypass a MALF for SCDY PT, this seemed like a reasonable way to go. Any comments?

[XfireZ51]

Originally Posted by XfireZ51

While we're on the topic of secondary PT removal, Lgaff and myself discussed the idea of just removing the throttle plates and leaving the rest of the linkage in. ECM still thinks secondaries are in. Everything works except no throttle blades in the way. And since we haven't determined yet how to bypass a MALF for SCDY PT, this seemed like a reasonable way to go. Any comments?

Anything further on "reprogramming the chip" if secondaries aren't used? What happens to use of PT Throttle Open VE and SA tables if the parameters for using secondaries is set high in order to avoid setting a code?
Any comments on simply removing the butterflies and leaving everything else intact?

[Maxlean]

Originally Posted by XfireZ51

Anything further on "reprogramming the chip" if secondaries aren't used? What happens to use of PT Throttle Open VE and SA tables if the parameters for using secondaries is set high in order to avoid setting a code?
Any comments on simply removing the butterflies and leaving everything else intact?

That's what we did. Kept the solenoid, pump, and diff map but took out the butterflys and shafts. Then in the prom, I duplicated the pt open sa and ve tables to the closed pt sa and ve tables. Works like a charm. The ecm thinks it's switching the secondaries, and using the different tables, but in reality is just using the pt open tables at all times. BTW, just setting the pt open point to be some really low value (as our chip was delivered) is not a good idea as since the ecm thinks it's in pt open mode it only uses 3 of the 19 ft cells. This can have a real impact on driveabilty (especially if your ve tables aren't perfect). Doing it the way I suggest allows the ecm to use all ft cells under normal driving as it thinks the pt's are closed.
Scott

[tpepmeie]

Originally Posted by Maxlean

BTW, just setting the pt open point to be some really low value (as our chip was delivered) is not a good idea as since the ecm thinks it's in pt open mode it only uses 3 of the 19 ft cells.Scott

There is nothing in the program to limit block learn cells when the port throttles are open. Whether PT open or not should have not effect on the block learn function.

Open port throttles does not mean power enrichment is active.

Todd

[XfireZ51]

Max,

So you've left the PT settings alone and duplicated the VE and SA tables?
I was thinking of taking the butterflies off the shafts but leaving the shafts in. Any comments on how detrimental that would be to maximizing performance?

[tpepmeie]

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

[XfireZ51]

Originally Posted by tpepmeie

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

Todd,

I really appreciate that perspective. As you've noted, there are several members that recommend removing the secondaries. Marc Haibeck indicated his experience on this issue is the same as yours. No measurable difference. Clearly, if you've noted higher MAP readings at PT with secondaries removed, having secondaries "in" must help in PT response.
I was looking for a way of retaining the secondary mechanism while "gaining" flow and avoiding the MALF issue. Based on what you've described, I'll leave them alone at this point. The plans for my motor don't call for anything very radical. A very streetable 12sec. car is my goal.
We'll see how it goes once I put on my ported top end in the next few weeks.

[LGAFF]

I am no expert, and I would agree a person would expect torque loss w/removal of the secondaries.....that said, the snakerskinner program removed and siamesed the runners, and ended up with more torque, making launching at anything over 1800rpm impossible. The car had exhaust mods, and advanced cams, but was a stock 350.

Anyone know who was involved in that program? The only name I have is Scott Leon who was the GM rep who oversaw testing. Would be interesting to know what they did and why, with secondaries.


LGAFF
92 ZR1
#234