Did you eliminate your Secondary Throttle Vacuum System?

[MuRCieLaGo]

Just thinking of eliminating my Secondary Throttle Vacuum System. Having some idle issues and I would like to eliminate that leak possibility.

I'm wondering how many of you guys eliminated that system.

[secondchance]

Sure did. Allowed injector housing porting to make the most out of 4" pistons and 3.75" stroke crank. LT5 runs flawlessly and never looked back.
Another benefit - 2ndary runners look clean like the primaries always.

[Dynomite]

Just thinking of eliminating my Secondary Throttle Vacuum System. Having some idle issues and I would like to eliminate that leak possibility.

I'm wondering how many of you guys eliminated that system.

I eliminated secondaries completely on a 91' but kept the secondaries on several 90s' and a 95'. The Secondaries perform great on the 90s' and the 95' once the vacuum system is restored with no vacuum leaks. And....And....once you have eliminated vacuum leaks, the vacuum leaks do not reappear for a very long time :p

I like that Power Key Option albeit I keep it on Full Power. That Full Power Option is very unique to the ZR-1s :thumbsup:

Kevin did a great "How To" write up on rebuilding the Power Key :thumbsup:
See Item #2 CMHSL LED, Full Power Key and Alternator Pulley (http://forums.corvetteforum.com/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp-3.html#post1581564081)

Jerry some time ago had available complete secondary vacuum lines and rubber connectors for the 95' (for around $100 as I recall) but he ran out I guess which is not surprising for such a bargain :)

[PhillipsLT5]

All gone, GREAT!

[efnfast]

I did, but miss them when it is time to tell the story about the key. "That key is for this, but not anymore."

[XfireZ51]

Eliminated the secondary actuation pretty soon after buying the car. Never noticed anything detrimental because if it.

[Paul Workman]

Pulled mine out 8 yrs ago when I ported the top end. Runs great. No regrets!

[WARP TEN]

I did on my '95. Marc did the work as part of a 510 package. One caveat: When they are eliminated, the injectors are set to run at a 50% flow rate so if you turn off the power key (i.e., return to "normal") the car will run too lean as it would shut off the secondary injectors. (I think I explained that correctly but please chime in if I did not.) I removed the key from the car and put a keychain tag on it to remind a future owner of the situation. --Bob

[Paul Workman]

I did on my '95. Marc did the work as part of a 510 package. On caveat: When they are eliminated, the injectors are set to run at a 50% flow rate so if you turn off the power key (i.e., return to "normal") the car will run too lean as it would shut off the secondary injectors. (I think I explained that correctly but please chime in if I did not.) I removed the key from the car and put a keychain tag on it to remind a future owner of the situation. --Bob

Mine and Ami's switches are hard-wired ON. Made that correction after my switch contacts started getting funky. (Already experienced a burned valve - due (I think) to a injector gone bad.)

[tiegsd]

Secondaries work great on my 90. Love the DR Jekyl Mr Hyde character of the car!

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[RussMcB]

One of the first things I did with my ZR-1 was to disable the secondaries, using chip mods by Haibeck. I was happy with the results. Simplified the system and the car ran well.

About a year later DIY Tune (aka Megasquirt) asked if they could use my car to try and finish up their MS3-Pro ECU for the LT-5. I said sure!

When they found out my secondaries were removed, they asked me if I could add them back in. I did, lent them my car, got it back a month later and it ran great. It was noticeably stronger. I'm sure that is because they had the luxury of running many iterations of tune and were able to reach an optimum tune.

They said they found that working secondaries helped the engine run better. I don't remember the details about why they believed that. My memory fails me. Perhaps it was the transition stage (a guess).

My hunch is, the computing power available today (compared to the late 1980's) allows them more control over the injectors and butterflies.

I'm certainly not knocking the removal of secondaries. I'm just sharing this experience to the thread.

[Ccmano]

One of the first things I did with my ZR-1 was to disable the secondaries, using chip mods by Haibeck. I was happy with the results. Simplified the system and the car ran well.

About a year later DIY Tune (aka Megasquirt) asked if they could use my car to try and finish up their MS3-Pro ECU for the LT-5. I said sure!

When they found out my secondaries were removed, they asked me if I could add them back in. I did, lent them my car, got it back a month later and it ran great. It was noticeably stronger. I'm sure that is because they had the luxury of running many iterations of tune and were able to reach an optimum tune.

They said they found that working secondaries helped the engine run better. I don't remember the details about why they believed that. My memory fails me. Perhaps it was the transition stage (a guess).

My hunch is, the computing power available today (compared to the late 1980's) allows them more control over the injectors and butterflies.

I'm certainly not knocking the removal of secondaries. I'm just sharing this experience to the thread.

Did MS ever market this system for the LT5? Is it still in your car?
H
:cheers:

[XfireZ51]

I think your perception of better performance has more to do w a custom tune
than any other factor.

[RussMcB]

Did MS ever market this system for the LT5? Is it still in your car?
H
:cheers:I'm not sure. I haven't seen it mentioned on their web site. You might need to call them. Yes, it's still in my car. Engine runs great.
I think your perception of better performance has more to do w a custom tune than any other factor.No doubt. I'm sure someone like Marc could do the same with enough time. The MS3-Pro is a lot easier and faster than altering the GM ECU, especially if the chip has to be mailed to someone to make a change.

BTW, it's not perception. :-)

[karlaw]

Question: when you eliminate the secondaries does the engine then have less HP ?


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[Dynomite]

Question: when you eliminate the secondaries does the engine then have less HP ?


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With Secondaries Eliminated and dependent on CHIP and Tuning.....you have More HP over a much wider range of engine RPM and Throttle Position.

This Marc Haibeck Link explains when the secondaries are functional as dependent on engine RPM and Throttle Position when in FULL POWER Mode :thumbsup:

Marc Haibeck Discussion on Secondary Operation (http://www.zr1specialist.com/HAT%20Web/articles/running%20on%20the%20secondaries.htm)

It should be noted that the 1990 ZR-1, 1991-1992 ZR-1 and 1993-1995 ZR-1 have different Secondary Operational limits in regard to RPM and Throttle Position. It should also be noted this only applies when the Full Power Switch is on FULL POWER.

[XfireZ51]

I'm not sure. I haven't seen it mentioned on their web site. You might need to call them. Yes, it's still in my car. Engine runs great.
No doubt. I'm sure someone like Marc could do the same with enough time. The MS3-Pro is a lot easier and faster than altering the GM ECU, especially if the chip has to be mailed to someone to make a change.

BTW, it's not perception. :-)

"Definition of perception for English Language Learners. : the way you think about or understand someone or something. : the ability to understand or notice something easily. : the way that you notice or understand something using one of your senses."

So perception can be and is reality. I was not implying that you were "imagining" a better running motor.

I don't think its any more difficult in modifying the tune using the OEM ECM.
There's many more parameters that an OEM needs to address and configure due to emissions, driveabiity, and fuel consumption considerations. Understanding how to use them actually gives you greater control over the tune. Not having used the software for the MS3, I can't comment further on its usability, but I can say that it is not necessary to ship your prom anywhere in order to make changes.
There's technology available, pretty inexpensively, that makes tuning on a remote basis a possibility.

[GOLDCYLON]

I removed them in 2012 and never looked back. One of the butterfly blades broke ingesting the blade and butterfly screw in the top of piston number #2 wedging it open and bending the intake and exhaust valves... I would not of believed that happening or could happen except this was the second time this had happened as last time one of the blades lost the screw on the other side. I suggest if you are in there. Pull em. the secondary system is prone to vacuum failures and leaks and who drives without the car in full power anyway?

The secondary system has two benefits only. Lower emissions and better fuel economy. What you gain is about 1 second response in throttle time, a valley area free of the secondary system with multiple points of failure and the potential of what happened to me in #2014 NOT happening to you. Go boldly.

Debate over.

GC

[Dynomite]

The secondary system has two benefits only. Lower emissions and better fuel economy.

Debate over.
GC

:sign10:

Well...well.....hmmmm....
I like that feature of Full Power with the switch of a key. That is attractive to guys who like the feature of kicking in another set of injectors and doubling the intake porting with the flip of a key. Very Unique and I just like it.

Once you fix vacuum leaks the vacuum leaks do not seem to come back :thumbsup:

Now Debate over :D

Oh.....yes.....I dropped one of those throttle cable bracket screws into the Injector Housing and had to install a new sleeve and a new piston in one cylinder.

[tiegsd]

I removed them in 2012 and never looked back. One of the butterfly blades broke ingesting the blade and butterfly screw in the top of piston number #2 wedging it open and bending the intake and exhaust valves... I would not of believed that happening or could happen except this was the second time this had happened as last time one of the blades lost the screw on the other side. I suggest if you are in there. Pull em. the secondary system is prone to vacuum failures and leaks and who drives without the car in full power anyway?

The secondary system has two benefits only. Lower emissions and better fuel economy. What you gain is about 1 second response in throttle time, a valley area free of the secondary system with multiple points of failure and the potential of what happened to me in #2014 NOT happening to you. Go boldly.

Debate over.

GC
Hmmm, eliminates maintenance issues, removes potential catastrophic failures, and car runs better? Starting to sound like a really good idea.

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[Dynomite]

Hmmm, eliminates maintenance issues Vacuum leaks are a one time fix for almost ALL ZR-1s, removes potential catastrophic failures Extremely rare to lose butterfly blade screws, and car runs better?My ZR-1s with Operational Secondaries run perfectly in ALL Modes including Full Power Starting to sound like a really good idea.For some it is a great idea....for others having the initial features fully operational is a Better Idea :p

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Just Saying ;)

Jerry does have rubber connectors, check valves, vacuum canisters, for the vacuum system which hardened rubber connectors are usually the source of vacuum leaks. Installation of New Secondary Port Vacuum System hoses (https://www.corvetteforum.com/forums/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp-12.html#post1590759176)

[RussMcB]

<snip> I was not implying that you were "imagining" a better running motor.

I don't think its any more difficult in modifying the tune using the OEM ECM.
There's many more parameters that an OEM needs to address and configure due to emissions, driveabiity, and fuel consumption considerations. Understanding how to use them actually gives you greater control over the tune. Not having used the software for the MS3, I can't comment further on its usability, but I can say that it is not necessary to ship your prom anywhere in order to make changes.
There's technology available, pretty inexpensively, that makes tuning on a remote basis a possibility.Good info. Thanks. :cheers:

[jss06c6]

I kept mine on my '91. Spent a lot of time tuning after addition of headers and SW exhaust. Brought the "entry" point when the secondaries open down and dialed in the port throttle open fuel and spark. Nice to feel them open up early! Car runs like it's pants are on fire at WOT..

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[-=Jeff=-]

Did MS ever market this system for the LT5? Is it still in your car?
H
:cheers:

Not officially, but it is available, last email I sent them they were in search of an OEM communication document (probably to add the MPG stuff into the code)

That was June.

I have an old link to this:
http://www.megasquirtpnp.com/docs/mspnp_gP_zr9195.php

When I asked in Sept of 2016 about release ETA and pricing I got this:

I'm afraid we do not have an ETA, but this is likely to be one of our more expensive MSPNPs due to the low volume. It's probably going to be in the $2000-2500 range.

I don't think the motivation is there honestly

[janozr1]

YES i DID.
Im happy now, with haibeck chip
jano,Slovenia

[MuRCieLaGo]

That's it, say no more. I'm removing that system and I will send my chip to Marc Haibeck in the next few days.

I removed them in 2012 and never looked back. One of the butterfly blades broke ingesting the blade and butterfly screw in the top of piston number #2 wedging it open and bending the intake and exhaust valves... I would not of believed that happening or could happen except this was the second time this had happened as last time one of the blades lost the screw on the other side. I suggest if you are in there. Pull em. the secondary system is prone to vacuum failures and leaks and who drives without the car in full power anyway?

The secondary system has two benefits only. Lower emissions and better fuel economy. What you gain is about 1 second response in throttle time, a valley area free of the secondary system with multiple points of failure and the potential of what happened to me in #2014 NOT happening to you. Go boldly.

Debate over.

GC

Wait, I don't understand. Do I have to remove some butterflies from the throttle body or what?

[RussMcB]

Wait, I don't understand. Do I have to remove some butterflies from the throttle body or what?No, you can/must wire the secondary (not TB) butterflies so they are always open.

[GOLDCYLON]

That's it, say no more. I'm removing that system and I will send my chip to Marc Haibeck in the next few days.



Wait, I don't understand. Do I have to remove some butterflies from the throttle body or what?

The heads

[XfireZ51]

No, you can/must wire the secondary (not TB) butterflies so they are always open.

Before eliminating the secondaries completely, I removed the throttle blades from the shafts and zip tied the actuators in full open position. Then put cheater plug into the secondary MAP harness connector. I later eliminated that by modifying the calibration and re-tune of fuel tables.

[MuRCieLaGo]

I thought I only had to remove this?

http://i287.photobucket.com/albums/ll142/dynomite007/LT5/SecondaryVacuumSys.jpg

[RussMcB]

There are a few variations. You can leave the parts in place, but just make them non-functional (so the throttle plates do not close). Or you can remove everything related to the secondaries (including the throttle plates). Or something in between.

[Ccmano]

There are a few variations. You can leave the parts in place, but just make them non-functional (so the throttle plates do not close). Or you can remove everything related to the secondaries (including the throttle plates). Or something in between.

But the throttle plates do have to be either removed or wired open. That is not an option. Easiest is to wire them open. Some unscrew the plates from the shafts and leave the shafts in place. Others remove everything, shafts and all, however this generally requires removal of the heads and resealing of the shaft holes in the heads.
H
:cheers:

[Paul Workman]

But the throttle plates do have to be either removed or wired open. That is not an option. Easiest is to wire them open. Some unscrew the plates from the shafts and leave the shafts in place. Others remove everything, shafts and all, however this generally requires removal of the heads and resealing of the shaft holes in the heads.
H
:cheers:

No removing of the heads necessary. Only the cover of that crankcase gizzy cover in the valley toward the front of the motor.

I highly recommend one FIRST PLUGS THE RUNNERS with a wad of paper toweling to prevent dropping a screw down inside the head. THAT could mean removing having to pull the motor and the head should the valve be open (my luck!) and the screw couldn't be retrieved with a magnet or the like.

Then the shaft and the bearing can be removed together, and (I used) a Dorman freeze plug and JB Weld to seal the hole left by the bearing/shaft.

To extract the shaft and bearing, once the actuator and linkage was removed, I used a 1/2" long (3/4" ID, IIRC) piece of metal conduit tubing placed over the bearing and placed a fender washer over the top (capping the conduit piece) so the threaded end of the shaft protrudes.

The little nut from the actuator linkage arm(s) is then reinstalled and screwed down onto the fender washer. Continue screwing it down against the washer, thus extracting the shaft and the bearing together. Voila!

I'll have to look up the Dorman plug #; a metric size approx 3/4" in dia., but per Pete's recommendation I smeared a little JB Weld on the edges of the Dorman plug. Then placing the Dorman over a 3/8" socket on the end of a short extension, a hammer was used to drive the Dorman into the void left by the bearing and sealing the hole securely.

Put the air box cover back on... Done w/ all that secondary BS (with the addition of Marc's delete chip and removal of the vacuum line to the SPT MAP switch).

[GOLDCYLON]

No removing of the heads necessary. Only the cover of that crankcase gizzy cover in the valley toward the front of the motor.

I highly recommend one FIRST PLUGS THE RUNNERS with a wad of paper toweling to prevent dropping a screw down inside the head. THAT could mean removing having to pull the motor and the head should the valve be open (my luck!) and the screw couldn't be retrieved with a magnet or the like.

Then the shaft and the bearing can be removed together, and (I used) a Dorman freeze plug and JB Weld to seal the hole left by the bearing/shaft.

To extract the shaft and bearing, once the actuator and linkage was removed, I used a 1/2" long (3/4" ID, IIRC) piece of metal conduit tubing placed over the bearing and placed a fender washer over the top (capping the conduit piece) so the threaded end of the shaft protrudes.

The little nut from the actuator linkage arm(s) is then reinstalled and screwed down onto the fender washer. Continue screwing it down against the washer, thus extracting the shaft and the bearing together. Voila!

I'll have to look up the Dorman plug #; a metric size approx 3/4" in dia., but per Pete's recommendation I smeared a little JB Weld on the edges of the Dorman plug. Then placing the Dorman over a 3/8" socket on the end of a short extension, a hammer was used to drive the Dorman into the void left by the bearing and sealing the hole securely.

Put the air box cover back on... Done w/ all that secondary BS (with the addition of Marc's delete chip and removal of the vacuum line to the SPT MAP switch).



Correctamundo

[MuRCieLaGo]

No removing of the heads necessary. Only the cover of that crankcase gizzy cover in the valley toward the front of the motor.

I highly recommend one FIRST PLUGS THE RUNNERS with a wad of paper toweling to prevent dropping a screw down inside the head. THAT could mean removing having to pull the motor and the head should the valve be open (my luck!) and the screw couldn't be retrieved with a magnet or the like.

Then the shaft and the bearing can be removed together, and (I used) a Dorman freeze plug and JB Weld to seal the hole left by the bearing/shaft.

To extract the shaft and bearing, once the actuator and linkage was removed, I used a 1/2" long (3/4" ID, IIRC) piece of metal conduit tubing placed over the bearing and placed a fender washer over the top (capping the conduit piece) so the threaded end of the shaft protrudes.

The little nut from the actuator linkage arm(s) is then reinstalled and screwed down onto the fender washer. Continue screwing it down against the washer, thus extracting the shaft and the bearing together. Voila!

I'll have to look up the Dorman plug #; a metric size approx 3/4" in dia., but per Pete's recommendation I smeared a little JB Weld on the edges of the Dorman plug. Then placing the Dorman over a 3/8" socket on the end of a short extension, a hammer was used to drive the Dorman into the void left by the bearing and sealing the hole securely.

Put the air box cover back on... Done w/ all that secondary BS (with the addition of Marc's delete chip and removal of the vacuum line to the SPT MAP switch).

Okay I'm happy I've read this. I really don't feel like pulling the engine out of the bay yet. I thought it was an easy "one-afternoon" DIY. I don't want to get involved in such an hassle.

I'll just fix it, it doesn't seem to be much complicated.

[A26B]

I should read more before responding🤤

[Ccmano]

No removing of the heads necessary. Only the cover of that crankcase gizzy cover in the valley toward the front of the motor.

I highly recommend one FIRST PLUGS THE RUNNERS with a wad of paper toweling to prevent dropping a screw down inside the head. THAT could mean removing having to pull the motor and the head should the valve be open (my luck!) and the screw couldn't be retrieved with a magnet or the like.

Then the shaft and the bearing can be removed together, and (I used) a Dorman freeze plug and JB Weld to seal the hole left by the bearing/shaft.

To extract the shaft and bearing, once the actuator and linkage was removed, I used a 1/2" long (3/4" ID, IIRC) piece of metal conduit tubing placed over the bearing and placed a fender washer over the top (capping the conduit piece) so the threaded end of the shaft protrudes.

The little nut from the actuator linkage arm(s) is then reinstalled and screwed down onto the fender washer. Continue screwing it down against the washer, thus extracting the shaft and the bearing together. Voila!

I'll have to look up the Dorman plug #; a metric size approx 3/4" in dia., but per Pete's recommendation I smeared a little JB Weld on the edges of the Dorman plug. Then placing the Dorman over a 3/8" socket on the end of a short extension, a hammer was used to drive the Dorman into the void left by the bearing and sealing the hole securely.

Put the air box cover back on... Done w/ all that secondary BS (with the addition of Marc's delete chip and removal of the vacuum line to the SPT MAP switch).

Paul,
Sounds like your next article for HOTB! Can’t wait...:dancing
H

[oricale]

No removing of the heads necessary. Only the cover of that crankcase gizzy cover in the valley toward the front of the motor.

I highly recommend one FIRST PLUGS THE RUNNERS with a wad of paper toweling to prevent dropping a screw down inside the head. THAT could mean removing having to pull the motor and the head should the valve be open (my luck!) and the screw couldn't be retrieved with a magnet or the like.

Then the shaft and the bearing can be removed together, and (I used) a Dorman freeze plug and JB Weld to seal the hole left by the bearing/shaft.

To extract the shaft and bearing, once the actuator and linkage was removed, I used a 1/2" long (3/4" ID, IIRC) piece of metal conduit tubing placed over the bearing and placed a fender washer over the top (capping the conduit piece) so the threaded end of the shaft protrudes.

The little nut from the actuator linkage arm(s) is then reinstalled and screwed down onto the fender washer. Continue screwing it down against the washer, thus extracting the shaft and the bearing together. Voila!

I'll have to look up the Dorman plug #; a metric size approx 3/4" in dia., but per Pete's recommendation I smeared a little JB Weld on the edges of the Dorman plug. Then placing the Dorman over a 3/8" socket on the end of a short extension, a hammer was used to drive the Dorman into the void left by the bearing and sealing the hole securely.

Put the air box cover back on... Done w/ all that secondary BS (with the addition of Marc's delete chip and removal of the vacuum line to the SPT MAP switch).
Dorman #555-108

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[Pete]

Dorman #555-108


Loctite 620 :)

Pete

[rkreigh]

Loctite 620 :)

Pete


so true! the LSV popped one of those little suckers out last year after 20k plus miles of no secondaries


we were running at the track and the huge vacuum leak made for an interesting trip home

[Karl]

Anyone notice lower fuel mileage after removing the secondaries?

[XfireZ51]

Anyone notice lower fuel mileage after removing the secondaries?

Why would fuel mileage change if u have a proper tune?

[Karl]

Why would fuel mileage change if u have a proper tune?

I don't know, that's why I am asking.

I assume all 16 injectors will run all the time versus 8 under normal driving conditions.

[GOLDCYLON]

Anyone notice lower fuel mileage after removing the secondaries?

Everyone

[Ccmano]

Hard to tell, my foots always in it. I guess from that perspective mileage is worse because you want to floor it all the time.
H
:cheers:

[XfireZ51]

I don't know, that's why I am asking.

I assume all 16 injectors will run all the time versus 8 under normal driving conditions.

Secondaries turn on just off idle. Then they share Pulse width w primaries. Therefore no additional fuel should be used. Unless ur like Hans or GC.

[Karl]

Secondaries turn on just off idle. Then they share Pulse width w primaries. Therefore no additional fuel should be used. Unless ur like Hans or GC.


That make sense, thanks for the info.

[Paul Workman]

@ 70 mph in cruise I got 26.4 mpg (as I recall). That was almost identical to what I got before deleting the secondaries.

.

[rkreigh]

I didn't notice any difference in MPG with them removed