Removing Secondary Vacuum System questions.

[Pete]

Here is the answer to emissions 2 chips.

One for emissions,one for performance.

Marc should know what to do.

Pete

[32valvZ]

So what exactly would be a good reason to do this if everything is working properly?

[rudolph schenker]

Originally Posted by 32valvZ

So what exactly would be a good reason to do this if everything is working properly?

[Paul Workman]

Originally Posted by 32valvZ

So what exactly would be a good reason to do this if everything is working properly?

Reliability, simplicity, and more air flow!

After alcohol-sensitive injectors, or injectors in general, it would be my observation that issues with the secondary control system is the second (if not the first) issue related to LT5 reliability - a WAAAAY over engineered solution to a "problem" that might have been overcome (and was on the GEN-II LT5) another way.

For example:

• There are 4 separate signal lines from the ECM controlling 4 separate relays each controlling (yet) a second pair of injectors; 24 connections in all, not counting the relays themselves.**
• There is the vacuum pump that initially charges the system and maintains vacuum as the secondaries are opened and closed (in spirited driving).
• Then there is the check valve and (old) rubber connections, plastic lines, the reservoir, solenoid, and let's not forget that the actuators should to be balanced to work in unison.

In my case, I concluded that
the air flow disruption was a consideration in the quest for HP,
throttle response is improved w/o all the stuff that needs to be actuated, espcially when all injectors are working all the time - no lag,
and since all the vacuum "stuff" could be eliminated and removed along with all the stumbling, and high idle, crap that goes along with something failing in the vacuum secondary system
the KISS principal.

So, except for a NCRS car, my question was why keep all that nonsense and the potential for complicating the troubleshooting aspect of maintaining the LT5?

The one item left to be eliminated (by me) is electrical. It stems from the way chip I have installed operates. The engine now depends on all injectors to be running - each injector sharing the load demand. If for any reason, and there are several, that the ECM should turn off the secondary injectors, some serious leaning would result and one would have to "limp home" until the problem was corrected.

So, the solution would be the equivalent of latching the secondary relays closed all the time or connecting the primary and secondary injectors in parallel - so they work as "one". The jury is still out on this - but I think Marc H agrees it may remove some potential for harm should some or all of the secondary injectors suddenly quit.

All that said, I couldn't find a reason NOT to remove the secondary actuation system. Of the 6 of us sitting at the table last week, I believe only one of us still was using the stock secondary system. The rest had removed all of the hardware, or tie-wrapped them open. As to how we liked running w/o the system, it was unanimous that we did prefer NOT having the secondary system installed.

Looks tell the story: Simple is a good thing!



FWIW,

P.

[tpepmeie]

Originally Posted by Paul Workman

So, the solution would be the equivalent of latching the secondary relays closed all the time or connecting the primary and secondary injectors in parallel - so they work as "one". The jury is still out on this - but I think Marc H agrees it may remove some potential for harm should some or all of the secondary injectors suddenly quit.

Or, disable the program logic which would ever cause the secondary injectors to shut down.

Or, implement a substantially lower rev limit (say 3000 rpm) in the event the secondaries are commanded shut down.

Different ways to skin this cat.

Todd

[DScott600]

When I read about and look at the LT5 it is a marvelous engine. The only thing that really bothered me was the secondary system. It looks like a last minute cobbled together idea and it is way over complicated. In the late nineties I had a 1996 mustang cobra. They had secondary throttle blades too that opened up at 3250 RPM. They were used for low end torque. The system was much simplier, they had plates between the intake and heads that were operated from a control box under the intake. It was a compact design and if you wished to eliminate it you pulled the intake to do so. In 99 Ford changed the design of the heads so that the system was no longer needed and they haven't used it since. My point is the system could have been similar to fords and we would have little to know issues with it. And everyone who has done it says that you notice no torque loss and even Marc says that it was for emissions. The Ford design was for low end torque but even they went away from it when they redesigned the heads to promote better low end torque.

[billybaloneey]

Originally Posted by Paul Workman

Reliability, simplicity, and more air flow!


Looks tell the story: Simple is a good thing!



FWIW,

P.

Paul - I noticed you removed the secondary shafts...according to the picture. How did you get the bearing out...they are staked (the term used in the FSM), or another way to describe it, a punch was used to dimple the IH in three places around the bearing? What did you use to fill in the holes once occupied by the bearing?

[John Boothby]

Order your gaskets from Jerry. He is very good at getting them out. Excellent service. Order the thicker gaskets that he offers and if you need to R/R the plenum again you should be able to reuse them, no sweat. Also, I reused my gaskets once, and they were perfect. Just be sure that they are in good shape and reuse them on the same side, don't flip them. I do not believe you need to use any sealant on them, I didn't. Torque the plenum screws according to the FSM (20 foot pounds) and in proper sequence.

[DScott600]

I should have wrote this sooner but I deleted the secondaries shortly after I started this thread and I am very happy with the results. I purchased a chip from Mark, removed the entire secondary system except for the sensor under the ECM and wire tied and safety wired the secondaries open. I didn't notice any difference at low speed and Marks tune has improved the idle and gave it more power. In the future I plan on getting the injector housings and plenum ported and powder coated and while I have it all apart I will remove the throttle plates. It's so good to not have to worry about a secondary vacuum leak area under the plenum is much nicer looking without the rats nest of hoses. Thank you for all the advice.

[tccrab]

What about us unfortunates who live where the dreaded SMOG Nazis prowl?
Would removing the secondaries affect emissions to the point of failing our bi-annual inspection?
I would love to be able to ditch them, one less thing to go wrong.

TomC
"Crabs"