Secondary Remove guide?

[Funracer]

Plenum and IHs out for porting. I want to remove or wire open the
secondaries while everything is opened up.

I DO want to remove all the secondary system vacume components under
the plenum. Tired of looking at all the spaghetti. Any step by step guides posted with pics?

Lots of posts that say "Rip em out" but Im looking for something more
specific. What to remove, what open holes to plug, what wires to unplug or leave in, etc, etc. I do want to maintain the cruise control.

With help maybe I can get it right the first time.

Thanks:handshak:

[Dynomite]

I DO want to remove all the secondary system vacume components under
the plenum. Any step by step guides posted with pics?

What to remove, what open holes to plug, what wires to unplug or leave in, etc, etc. I do want to maintain the cruise control.

With help maybe I can get it right the first time.

Thanks:handshak:

This will get you started ;)

I would NOT use wire to hold the secondaries open......but then again......
if you are not sure you want to eliminate the secondaries.....maybe a temporary fix using wire would be your best option. :)

Using wire to fix the secondaries open is a lot simpler for sure especially if the engine is in the car.

See Technical Index (http://forums.corvetteforum.com/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp.html#post1580070549)

LT5 Eliminated Systems (http://forums.corvetteforum.com/c4-zr-1-discussion/2942569-tech-info-lt5-eliminated-systems.html)

Vacuum Systems (Secondary and Cruize/HVAC) (http://forums.corvetteforum.com/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp-2.html#post1581460752)

[Funracer]

This will get you started ;)

See Technical Index (http://forums.corvetteforum.com/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp.html#post1580070549)

LT5 Eliminated Systems (http://forums.corvetteforum.com/c4-zr-1-discussion/2942569-tech-info-lt5-eliminated-systems.html)

Vacuum Systems (Secondary and Cruize) (http://forums.corvetteforum.com/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp-2.html#post1581460752)

So everything in the first two photos is removed and everything
in the second two photos (cruise) remains?

[Dynomite]

So everything in the first two photos is removed and everything
in the second two photos (cruise) remains?

You can keep or eliminate the Evap Purge vacuum lines also. I kept the Evap Purge in place as I installed a new charcoal cannister back by fuel tank. If you eliminated Evap Purge you would have to cap off the Evap Purge Vacuum source under Plenum.

http://i287.photobucket.com/albums/ll142/dynomite007/C%20Engine%20LT5/926c5317-098a-46fc-ac3d-76edbdeff335.jpg

Cruize Control and HVAC Vacuum System ..............................EVAP Purge Vacuum System with Solenoid
http://i287.photobucket.com/albums/ll142/dynomite007/C%20Engine%20LT5/533eb78e-df33-4c26-b797-bf5252a35535.jpghttp://i287.photobucket.com/albums/ll142/dynomite007/C%20Engine%20LT5/043c368f-b6f9-4a47-bbb3-a23761fafa4e.jpg

Marc and Pete suggested to eliminate the EVAP Purge circuit completely and capping off that vacuum source under front of plenum. I just replaced my charcoal canister and Marc says he does not address that removal in the chip as it has no effect. I left that associated vacuum and electrical connection including the Evap Purge solenoid in place under the plenum.

[Funracer]

You can keep or eliminate the Evap Purge vacuum lines also. I kept the Evap Purge in place as I installed a new charcoal cannister back by fuel tank. If you eliminated Evap Purge you would have to cap off the Evap Purge Vacuum source under Plenum.

http://i287.photobucket.com/albums/ll142/dynomite007/C%20Engine%20LT5/926c5317-098a-46fc-ac3d-76edbdeff335.jpg

Did you keep it for emissions testing purposes? No testing in Florida
so I will pull it.

[Dynomite]

Did you keep it for emissions testing purposes? No testing in Florida
so I will pull it.

No.....I register vehicles in SD....so no emissions testing there either. Like I say...I kept it because it is a simple circuit and I just replaced charcoal canister.....and probably keeps the gas fumes down when I gas up :D

Besides...I did not want to eliminate everything at once for fear that some would say I no longer have an LT5 :sign10:

[Funracer]

No.....I register vehicles in SD....so no emissions testing there either. Like I say...I kept it because it is a simple circuit and I just replaced charcoal canister.....and probably keeps the gas fumes down when I gas up :D

Besides...I did not want to eliminate everything at once for fear that some would say I no longer have an LT5 :sign10:

Seems too easy and not many things on the LT5 are easy. I will tackle this
Friday or Saturday and prob be back with more questions.

Thanks;)

[Dynomite]

Seems too easy and not many things on the LT5 are easy. I will tackle this
Friday or Saturday and prob be back with more questions.

Thanks;)

I modified the heads (Install Dorman freeze plugs 555-108) pulling secondaries with engine out of car (Heads removed). Maybe Paul or others have pulled secondaries without removing Heads....which seems can be done just do not drop anything into cylinder through an open valve :handshak:

I would NOT use wire to hold the secondaries open......but then again......
if you are not sure you want to eliminate the secondaries.....maybe a temporary fix using wire would be your best option. :)

Using wire to fix the secondaries open is a lot simpler for sure especially if the engine is in the car.

When you pull the plenum (I guess you are already past that stage) do not forget to draw down the coolant level a bit so you do not get coolant in the cylinders. See item #4 LT5 Eliminated Systems (http://forums.corvetteforum.com/c4-zr-1-discussion/2942569-tech-info-lt5-eliminated-systems.html)

I think you have to modify your chip in the ECM to accomodate the fact you eliminated the vacuum system and secondaries. The custom chip would change the fueling for the secondary injectors for example Marc Haibeck Custom Fueling (http://www.zr1specialist.com/HAT%20Web/products/custom%20calibration.htm)

http://i287.photobucket.com/albums/ll142/dynomite007/B%20Engine%20LT5/SUnderPlenum_zps2786b9dd.jpghttp://i287.photobucket.com/albums/ll142/dynomite007/A%20Engine%20LT5/SecondariesEliminated90HeadsS_zps00ee9dfe.jpg
http://i287.photobucket.com/albums/ll142/dynomite007/C%20Engine%20LT5/d1e57ebc-c9f8-4b4d-a042-174e56f160a0.jpg

[Paul Workman]

This topic strikes me as an item for the HOTB Newletter... Hmmmm...

Nice pix, there Cliff!!

Well, just to add a few particulars for a "heads in place" procedure: (and I'll get to writing that article later))

Of course you'll need a chip (from Marc or whomever). In addition to secondary delete feature, he can also include in the program (as a minor expense) a -

-decelleration fuel moderation that will suppress "popping" in the headers, should you have them.

-program adjustment to turn both fans on at (I wanna say) 205ºF and turn them both off again at ≈ 200ºF. Not only does it keep it running cooler on a hot day, but stabilizes the temperature within a relatively narrow window. I suppose there are some unseen advantages in that as well??

-provide fueling changes to accomodate top end porting (for example) to carry over until the tune can be tweaked on the dyno.

You may need a plenum gaskets, an injector housing gasket set, and you'll need a breather box gasket (that squarish box in the bottom - front of the valley with the two (approx) 1-3/4" hoses coming out of it, that run to the injector housings.)

Removing the secondary harness including the reservoir, check valves, and vacuum actuators is all pretty straight forward. (If one has the mechanical skills enough to get the plenum and IHs off, then the rest is equally easy!) Only remove that which associated with the driver's side plenum vacuum pipe (middle of the plenum, between the runners) and the vacuum pump. (The passenger side plenum vacuum tube runs the cruise control and the HVAC systems.)

Here's a schematic of the vacuum harness under the plenum. Location of a couple components vary - e.g., the secondary vacuum sensor switch. However, the "pink" highlight is the secondary circuit which is essentially the same.

http://i185.photobucket.com/albums/x220/6PPC_bucket/tech%20files/plenumvacuumcircuitsLT5Large.jpg

Secondaries removed...

http://i185.photobucket.com/albums/x220/6PPC_bucket/tech%20files/ZR-1009.jpg

As for removing the Secondary Port Throttle (SPT) plates, NOW is the time for a little paranoia!;) You do not want to let a screw get away and drop into the runner or there's a chance you may have to pull the head to get it back!

You'll have to remove the breather box cover in order to remove the SPT shafts near the front of the motor to keep from possibly ruining the shaft as you extract it.

Once the SPT plates are removed, you remove the shaft and the bearing. Start by removing the little actuator arm from the shaft, but keep the little nut handy.

You'll need to fashion a little tool (or I'll send you mine) to pull the shaft and bearing out. The bearing comes out with the shaft, so what works really well is a piece of a pipe nipple, about 3/4" inch (2 cm) long with an inside diameter of just over 5/8" (1.7 cm).

This goes over the end of the threaded end of the shaft, centered around the bearing, resting on the boss but clear of the bearing.

A fender washer with a small hole covers the top of the pipe nipple. After greasing up the threads and the top of the washer, the little nut from the little shaft arm (now removed) is screwed down against the washer.

While keeping the shaft from turning with pliers, continue to screw the nut down against the washer which will draw the shaft and the bearing out together.

To seal the bearing recess, a Dorman 555-108 freeze plug (or the like) with a smear of JB Weld on it is tapped into place.

The secondary differential pressure switch (is under the ECM on a '90, but sometime later was moved to under the plenum) is left in place, except the vacuum hose is removed to leave the open end of the switch exposed to the atmosphere.

IMPORTANT: The Full Power switch on a 90 must ALWAYS be left in the FULL POWER position. The piont is, the calibration splits the fueling dwell time between both primary and secondary injectors. If for any reason the secondaries are switched off, fueling is cut in half resulting in a very lean condition. (However, that said, the major contributor to the secondaries being turned off, other than the switch on a 90, is loss of vacuum in the secondary circuit. Well, that ain't gonna happen anymore!):)

Note: After 1990, the FULL POWER condition is handled in the deleted secondaries programming. On my 90 I soldered a wire between the terminals of the FULL POWER switch against either the switch somehow being turned off, or faulty contacts issue within the switch itself (not at all that uncommon).

Note: At idle, only the primary injectors are running. But, just off idle, the secondaries are switched on and the fuel metering is shared between the two injectors beyond that.

Note: Ted Demps said his mpg went down a couple miles. My experience is different. Mpg remainded essentially the same in spite of also completing the "500" package. (I measured mpg manually before and after with cruise control on at 70 yeilded 26.x in both cases. Color me :dancing!!

Once the plenum & IHs were off, it took under a 4 hours (no hurry) to pull and seal the SPT stuff.

In my case there hasn't been a single downside to their removal that I'm aware of. It has been ALL GOOD. In addition to freedom from vacuum leak/vacuum pump issues, throttle response is improved, secondary valve remains clean(er), and perhaps there is some improvement in performance resulting from removing the plates and rods from the critical center of the air column. And, in my case net mpg remained unchanged.

The one item I can't comment on is emmissions compliance. OBD-I cars are exempt from emmissions tests in IL. So, I've never tested it before or after to know what (if any) impact removing secondaries has had in that aspect. Perhaps someone that is required to meet emmissions can comment further in this regard.

Just as an asside...

I don't argue with anyone wishing to keep everything "as is". In fact, I dispise doing anything that is cobbled up, especially if it reduces reliability or driveability and generally too if it can't be reversed if I change my mind. This procedure is none of that.

In the end, the "FBI 500" package, including the removal of the STPs, is a remarkable modification! Mine resulted in significant power increase without compromising mid range torque (actually increases it some!) overall reliablily, the integrity of the motor, mpg, idle quality, or (street manners) drivability (noiser exhaust excepted). That is some trick for 5.7L V8 without VVT or the like. Long live the ZR-1 & LT5!!

[Dynomite]

This topic strikes me as an item for the HOTB Newletter... Hmmmm...

Nice pix, there Cliff!! Thanks Paul.....you are welcome to use any and all pics in your posts or HOTB I have posted :handshak:

Well, just to add a few particulars for a "heads in place" procedure: (and I'll get to writing that article later))

Of course you'll need a chip (from Marc or whomever). In addition to secondary delete feature, he can also include in the program (as a minor expense) a -
-decelleration fuel moderation that will suppress "popping" in the headers, should you have them.

-program adjustment to turn both fans on at (I wanna say) 205ºF and turn them both off again at ≈ 200ºF. Not only does it keep it running cooler on a hot day, but stabilizes the temperature within a relatively narrow window. I suppose there are some unseen advantages in that as well??

-provide fueling changes to accomodate top end porting (for example) to carry over until the tune can be tweaked on the dyno.


Secondaries removed...

http://i185.photobucket.com/albums/x220/6PPC_bucket/tech%20files/ZR-1009.jpg

In my case there hasn't been a single downside to their removal that I'm aware of. It has been ALL GOOD. In addition to freedom from vacuum leak/vacuum pump issues, throttle response is improved, secondary valve remains clean(er), and perhaps there is some improvement in performance resulting from removing the plates and rods from the critical center of the air column. And, in my case net mpg remained unchanged.

The one item I can't comment on is emmissions compliance. OBD-I cars are exempt from emmissions tests in IL. So, I've never tested it before or after to know what (if any) impact removing secondaries has had in that aspect. Perhaps someone that is required to meet emmissions can comment further in this regard.

Just as an asside...

In the end, the "FBI 500" package, including the removal of the STPs, is a remarkable modification! Mine resulted in significant power increase without compromising mid range torque (actually increases it some!) overall reliablily, the integrity of the motor, mpg, idle quality, or (street manners) drivability (noiser exhaust excepted). That is some trick for 5.7L V8 without VVT or the like. Long live the ZR-1 & LT5!!

Great Technical Stuff there Paul........I Knew you would get the details for Heads Not Removed and for that matter same proceedure for Heads Removed (Except for Crankcase Ventilation Cover removal) :thumbsup:

As an aside....I went and modified some posts on that Cruize Control Vacuum line on passenger side which as you state shares vacuum with HVAC system interior :handshak:

Thanks Paul
And Yes.....cannot stress enough....do NOT drop anything in Head Valve area when extracting the secondaries :cheers:

Marc set Power Always On in the Chip for my 91' and as you say....I guess you cannot do that in the 90' :)

[Funracer]

Thanks to all for the help on this thread. I accomplished the deed
on Saturday and followed the pics and advise above closely. Removed
all the secondary vacume lines and associated hardware as well as the
the evap purge lines. Left the vacume pump under the right side headlight
in place and just unhooked the vacume line and disconnected the electrics.

http://i22.photobucket.com/albums/b341/yellowLT1/ZR1/IMAG0757_zpsed5d938b.jpg

Still deciding whether to wire open the secondaries or remove them. More
on that later.

Thanks

[5ABI VT]

Funracer what year is your z?

[Paul Workman]

Thanks to all for the help on this thread. I accomplished the deed
on Saturday and followed the pics and advise above closely. Removed
all the secondary vacume lines and associated hardware as well as the
the evap purge lines. Left the vacume pump under the right side headlight
in place and just unhooked the vacume line and disconnected the electrics.

http://i22.photobucket.com/albums/b341/yellowLT1/ZR1/IMAG0757_zpsed5d938b.jpg

Still deciding whether to wire open the secondaries or remove them. More
on that later.

Thanks

I'm assuming your calibration was changed for NO SECONDARIES, yes?

90s require a hard electrical connection (switch) to be left in FULL POWER mode. However, if the contacts get corroded or oxidized, the connection could become "sketchy" or even open. That is a BAD thing in a 90 secondary deleted motor.

I would suggest hard-wiring (soldering a shunt between the wires), effectively taking the switch out of the circuit. That way no gremlins can turn off the switch: gremlins imaginary or real (called kids).[-X

Just sayin...

[dcarroll95]

Another valid reason to remove the secondary valves is the secondary intake valve gets massive carbon build-up from not running all the time. I'm in the middle of removing the butterflies and can see the intake valve and my car with just 19k miles has major carbon build-up on the intake valves. I'm going to try to clean it up before I put it all back together.

I hemmed and hawed about ditching the secondaries as I hate to make a low mileage car non-OEM but I feel I can justify it to a future buyer based on this. There's a great article on secondary intake valve carbon build-up on Marc Haibeck's web page:
http://zr1specialist.com/HAT%20Web/facts%20and%20failures/valve%20deposits.htm

He doesn't specifically state that a solution is to remove the secondaries but doing so will ensure fuel is flowing over the secondary intake valve and keep it just as clean as the primary intake. It's pretty astounding looking at the build-up on the secondary intake valves on my car vs the primaries.

[dcarroll95]

Also, can I test run the car with the valves open before I chip it or is that a huge No No = engine lean and blow up? Hopefully someone responds before I get it back together. Kind of want to drive it 1-2 miles before I send the chip off, but won't do it unless I hear affirmative.

[Paul Workman]

Yes, you can, but why bother??

Total air flow into the motor is controlled by the throttle body, and not by the SPTs. Normal fueling will be supplied by the primary injector only up until the rpm and throttle position triggers the ECM to command the SPTs open. Then the necessary fueling amount is split/shared between the primary and secondary injectors.

You might (maybe?) be able to notice a slight decrease in torque after the secondaries are tied open, compared to stock operation. But, as soon as (power demand) opens the secondaries anyway, tied open or not would not matter, far as performance goes.

IMO, deleting the secondaries is a "no brainer". Less "stuff" to ever break down later, and BOTH intake valves get washed (and thus) clean in normal driving.

NOTE: And, for what its worth, the second gen LT5 did away with the whole primary-secondary arrangement anyway. I and others consider this as validation for removing them in the first place. The LT5 is starving for air; proven by the gobs of performance increase w/o the significant loss of low end torque seen after intake porting of many 2-valve motors.

.

[rkreigh]

a few tips


stuff some paper towels down the ports


do indeed take the linkages and flappers out, while the don't hurt flow much, they are worth some $ and "in the way"


DO look at porting and opening up the secondary ports, without the flappers you can go bigger now which is one of the real benefits.


make sure you use the new chip as all injectors will need to run at all times except idle where it steps down to 1 injector at tps 1%


try to do the head porting to really take advantage of this mod. Otherwise it's nice, but not that much gain.



unlock the gain with 4.10 gears as you will "pull through" the small area in the power curve under 2000 rpm where the flappers pick up some low end torq


with the gears you are almost "never there" and will get up over 2500 where the no flapper mod really starts to gain over having them closed.


this engine has a "myth" of being down on low end torq and this doesn't help down low but honestly I only notice the good and I've been flapperless for many years now. DO IT!!!