Secondaries? Pros and cons?

[KILLSHOTS]

Hey guys,

As I understand it, the main argument for KEEPING the secondaries is originality, whereas the main argument for REMOVING them is simplicity. Is that really it? Is there anything I'm missing here? Some other compelling reasons that I should consider one option over the other?

I'm not trying to start a poll of who has removed them and who has kept them, and I'm not really looking for opinions, e.g. "I removed mine and like it, so you should, too!" Rather, I'm just trying to fully understand the pros and cons of both options before moving forward. FWIW, my car is not heavily modified but it's certainly no NCRS candidate, either, so that's not a consideration for me.

Thanks for your input!

[Blue Flame Restorations]

For me, removing them was a no brainer. Less moving parts and less chance for a vac leak.

[KILLSHOTS]

For me, removing them was a no brainer. Less moving parts and less chance for a vac leak.
Yeah, that's sort of how I see it too, Brett. But is there any advantage to keeping them, aside from just retaining the car's original complexity?

[USAZR1]

For me, removing them was a no brainer. Less moving parts and less chance for a vac leak.


And those less moving parts that can fall into the intake tract,causing major damage.

First time our LT5's plenum comes off,the secondaries will be history on our car.

[GOLDCYLON]

There are no cons

[Fully Vetted]

The only con is it's not original and that's only a con if you want to keep it original. If that doesn't matter to you there is no reason to keep them.

[Karl]

Do all 16 injectors run all the time with the secondaries removed? Or am I way off and the 16 injectors run all the time regardless?

[KILLSHOTS]

So far, this is pretty much the feedback I was expecting.

Please forgive my ignorance on the specifics of the system, but am I correct in assuming that removing them will disable the "valet key" function of my car? Remember, mine is a 1990 and the switch on my car functions somewhat differently than '91-'95 cars...not sure if that matters at all.

Thanks again, all!

[PhillipsLT5]

For me, removing them was a no brainer. Less moving parts and less chance for a vac leak.

I agree, mine are gone + 10 HP RWHP with tune, GC lost a motor with them, Marc can burn chip as needed

[XfireZ51]

So far, this is pretty much the feedback I was expecting.

Please forgive my ignorance on the specifics of the system, but am I correct in assuming that removing them will disable the "valet key" function of my car? Remember, mine is a 1990 and the switch on my car functions somewhat differently than '91-'95 cars...not sure if that matters at all.

Thanks again, all!

16 injectors operate unless motor goes idle. The advantage is that it keeps injectors operational and secondary valves cleaner.

[We Gone]

I have to keep mine another year than no more emissions so out they come.

[XfireZ51]

I have to keep mine another year than no more emissions so out they come.

Steve,

You can ask Darby (4-cam) about emissions and secondaries. It really doesn't make a difference as long as you have a proper tune. The motor will only use so much air/fuel regardless of whether it's delivered by 1 or 2 injectors/runners.

[tf95ZR1]

One reason to keep the secondaries is if you live in a strict
smog control state. If you do a search on the subject, comparing
dyno charts showed more torque at low end, but this was
disputed. You would also have to reprogram to compensate
for no vacuum secondaries.

Just read other posts. Has anyone in a strict smog state like CA
passed smog without secondaries?

[tf95ZR1]

To REHASH:

#56
http://www.zr1.net/forum/showthread.php?t=19823&page=6

But read the entire post for (+) and (-)

[4-cam]

2 years ago I removed my secondarys and ported the top end and passed the tough IM240 emmisions in colorado with a chip from Cory Henderson. This was a pretty much stock calibration.
I just added headers, magnaflow cats, and 3" exhaust and it failed miserably with the prevoius calibration. I used one of Dominics calibrations and it passed without an issue.
My vote is to remove them but have a good tuner lined up before you get going on the project.

[KILLSHOTS]

My car is emissions-exempt, so that isn't a factor. I already have one of Marc's chips, but would send it to him to have him change the calibration to handle the new setup, so no issue there, either.

Again, can anyone answer my earlier question: would removing the secondaries eliminate the "valet key" feature? (so it would always be in "full engine power" mode?) And if so, is that the only real "change" that I'd notice in the car's operation?

[KILLSHOTS]

One reason to keep the secondaries is if you live in a strict
smog control state. If you do a search on the subject, comparing
dyno charts showed more torque at low end, but this was
disputed. You would also have to reprogram to compensate
for no vacuum secondaries.

Just read other posts. Has anyone in a strict smog state like CA
passed smog without secondaries?
More torque at the low end AFTER the secondaries are removed? Phillip also mentioned +10 RWHP after removing them and adjusting the calibration.

Is this true, that removing the secondaries adds power? I knew it was a "reliability" upgrade but I had no idea that it was also a potential performance upgrade...

[4-cam]

And yes, the valet key is programed "ON" all the time. All injectors are also "ON" when TPS position is more than 0 % .

[We Gone]

Thanks for the info. on secondary and emissions, as I only have 1 more year than the car is exempt and the test is only $20 I will wait. Plus I don't have a good tuner around me. It does not sound like something Marc could do via mail.

[Paul Workman]

My car is emissions-exempt, so that isn't a factor. I already have one of Marc's chips, but would send it to him to have him change the calibration to handle the new setup, so no issue there, either.

Again, can anyone answer my earlier question: would removing the secondaries eliminate the "valet key" feature? (so it would always be in "full engine power" mode?) And if so, is that the only real "change" that I'd notice in the car's operation?

On a 90 the "valet" key function is lost, i.e, must always be in FULL setting ALWAYS!** in that with the secondaries removed, the fuel delivery is split between both injectors, and should one injector be turned off, the calibration doesn't have a way to revert and a very lean situation results (according to Marc, when he sold me his chip).

From 91 on the calibration can be programmed to keep the system in FULL POWER. However, the 90s depend on that mechanical switch to remain in FULL 100% of the time. Those switch contacts in the 90s have been known to become tarnished over time, and electrical connections become sketchy. SO! I simply soldered a bridge (wire) across the two wires leading to/from the switch contacts, thus removing the possibility of the switch contacts becoming sketchy - or someone switching it to NORMAL w/o me noticing.

PROS (for keeping the system stock):


At low throttle, as in city traffic, Graham produced some dyno graphs that show slightly higher torque is produced in the stock motor with the secondaries not activated.

Although meeting emissions, even in some severe States, has been demonstrated - WITH the proper calibration - keeping them AND having the stock calibration chip handy, might make keeping the system intact.

NCRS cars might benefit by keeping the system intact.

It IS possible to pin (tie-wrap) the secondaries open to give one the option of running w/o secondaries and retuning to stock setup relatively easily by clipping the ties, re-plumbing the MAP, and installing the stock chip.


CONS (to keeping the secondaries)


Throttle response lag when snapping to WOT, and between gears too, unless the throttle is held above a certain % during the shifts.

The secondary intake valve becomes caked with carbon to the point of impeding WOT performance. This can be minimized when on a long cruise by going WOT to open the secondaries and then maintaining something like 10-15% throttle after WOT will keep the secondaries turned ON. However, this gets to be a nag real quick in traffic or when on hilly terrain.

It is difficult to quantify due to practical matters e.g., removing the plenum to remove the secondaries, but the throttle plate rods run through the center of the laminar flowing air stream in the runner. This is never a "good thing", far as theory goes. For an all-out effort to gain hp, certain things are based on good engineering practice, if they can't be practically proven, and removing those plates/rods falls into this category. I'm skeptical of absolute numbers "before and after" removing the secondaries, due to difficulties in controlling all the variables that affect dyno results in the interim of removing them to re-test. But, the principles of laminar flow convinces me there is some advantage, maybe 5-10 hp would be about what I would guess.

"What parts don't exist seldom break, and they don't cost anything!" If for any reason one has to go plenum diving more than once to chase a secondary problem, one might consider deleting it entirely...is what I did.

If one ports the intake runners beyond 36mm, then the throttle plates no longer function as designed anyway. So, keeping them becomes moot and a detriment to performance.


Getting back to the loss of low speed torque resulting from removing the secondary port throttles (SPT):

From my personal experience, if there was some torque loss, I didn't notice it at all. But, mitigating circumstances includes the fact that I switched from the stock 46# dual mass flywheel to a 13# single mass aluminum flywheel at the same time. I don't know to the extent the FW mitigated some of the low end torque "loss" due to pulling the SPTs, but theoretically it would have resulted in more engine torque passing through to the drive train instead of being absorbed by the heavy dual mass FW. (Marc Haibecks inertia dyno sheets substantiate an effective 15 hp gain at the rear wheels by switching to a light aluminum FW.

In my case, the difference in FW mass calculates to a 11.9 ft# increase in rwt at peak power rpm (note: 4th gear). HOWEVER, the effective torque throughput resulting from the lighter FW increases with the rpm rate of change. The rate of rpm change is much higher in the lower gears, and so the mitigating effect of a lighter FW would also be significantly more than that 11.9 (effective torque) in 4th gear - perhaps exceeding the torque advantage of keeping the SPTs. (I believe that to be the case.)

AND, as part of my top-end porting mods, I realize a significant increase rwt across the full rpm range, compared to my baseline dyno results for my stock LT5.

[KILLSHOTS]

On a 90 the "valet" key function is lost, i.e, must always be in FULL setting ALWAYS!** in that with the secondaries removed, the fuel delivery is split between both injectors, and should one injector be turned off, the calibration doesn't have a way to revert and a very lean situation results (according to Marc, when he sold me his chip).

From 91 on the calibration can be programmed to keep the system in FULL POWER. However, the 90s depend on that mechanical switch to remain in FULL 100% of the time. Those switch contacts in the 90s have been known to become tarnished over time, and electrical connections become sketchy. SO! I simply soldered a bridge (wire) across the two wires leading to/from the switch contacts, thus removing the possibility of the switch contacts becoming sketchy - or someone switching it to NORMAL w/o me noticing.

PROS (for keeping the system stock):


At low throttle, as in city traffic, Graham produced some dyno graphs that show slightly higher torque is produced in the stock motor with the secondaries not activated.

Although meeting emissions, even in some severe States, has been demonstrated - WITH the proper calibration - keeping them AND having the stock calibration chip handy, might make keeping the system intact.

NCRS cars might benefit by keeping the system intact.

It IS possible to pin (tie-wrap) the secondaries open to give one the option of running w/o secondaries and retuning to stock setup relatively easily by clipping the ties, re-plumbing the MAP, and installing the stock chip.


CONS (to keeping the secondaries)


Throttle response lag when snapping to WOT, and between gears too, unless the throttle is held above a certain % during the shifts.

The secondary intake valve becomes caked with carbon to the point of impeding WOT performance. This can be minimized when on a long cruise by going WOT to open the secondaries and then maintaining something like 10-15% throttle after WOT will keep the secondaries turned ON. However, this gets to be a nag real quick in traffic or when on hilly terrain.

It is difficult to quantify due to practical matters e.g., removing the plenum to remove the secondaries, but the throttle plate rods run through the center of the laminar flowing air stream in the runner. This is never a "good thing", far as theory goes. For an all-out effort to gain hp, certain things are based on good engineering practice, if they can't be practically proven, and removing those plates/rods falls into this category. I'm skeptical of absolute numbers "before and after" removing the secondaries, due to difficulties in controlling all the variables that affect dyno results in the interim of removing them to re-test. But, the principles of laminar flow convinces me there is some advantage, maybe 5-10 hp would be about what I would guess.

"What parts don't exist seldom break, and they don't cost anything!" If for any reason one has to go plenum diving more than once to chase a secondary problem, one might consider deleting it entirely...is what I did.

If one ports the intake runners beyond 36mm, then the throttle plates no longer function as designed anyway. So, keeping them becomes moot and a detriment to performance.


Getting back to the loss of low speed torque resulting from removing the secondary port throttles (SPT):

From my personal experience, if there was some torque loss, I didn't notice it at all. But, mitigating circumstances includes the fact that I switched from the stock 46# dual mass flywheel to a 13# single mass aluminum flywheel at the same time. I don't know to the extent the FW mitigated some of the low end torque "loss" due to pulling the SPTs, but theoretically it would have resulted in more engine torque passing through to the drive train instead of being absorbed by the heavy dual mass FW. (Marc Haibecks inertia dyno sheets substantiate an effective 15 hp gain at the rear wheels by switching to a light aluminum FW.

In my case, the difference in FW mass calculates to a 11.9 ft# increase in rwt at peak power rpm (note: 4th gear). HOWEVER, the effective torque throughput resulting from the lighter FW increases with the rpm rate of change. The rate of rpm change is much higher in the lower gears, and so the mitigating effect of a lighter FW would also be significantly more than that 11.9 (effective torque) in 4th gear - perhaps exceeding the torque advantage of keeping the SPTs. (I believe that to be the case.)

AND, as part of my top-end porting mods, I realize a significant increase rwt across the full rpm range, compared to my baseline dyno results for my stock LT5.
This is awesome, Paul. Can't imagine a more complete explanation, answers my questions fully. The idea of going to the lightweight flywheel does intrigue me but I don't want "gear rattle." Or at least I don't think I do...what does it sound like exactly, and do guys have a problem with it after this switch?

Thanks so much for taking the time!!

[KILLSHOTS]

To REHASH:

#56
http://www.zr1.net/forum/showthread.php?t=19823&page=6

But read the entire post for (+) and (-)
If I'm reading this correctly, it looks like there is a difference of less than half a point in both HP and torque at peak. That probably falls within "variances between runs" anyway. Unless there's something else that I'm missing? Thanks!

[XfireZ51]

I call this my "Stairway to LT-5 Heaven" dyno graph. It shows the progression of power and torque through stages of modification and tune. The bottom one demonstrates a ported top end with secondaries tied open. The throttle plates had been removed however but the shafts remained albeit w the least surface facing airflow. The calibration has an injector "turn-on" delay which is eliminated when the secondaries are deleted or at least it should be.

http://i187.photobucket.com/albums/x198/Z51Xfire/CamEvolution_zps14e88fe5.jpg

[Paul Workman]

This is awesome, Paul. Can't imagine a more complete explanation, answers my questions fully. The idea of going to the lightweight flywheel does intrigue me but I don't want "gear rattle." Or at least I don't think I do...what does it sound like exactly, and do guys have a problem with it after this switch?

Thanks so much for taking the time!!

With stock cams, and even with some custom phasing, there is very slight rattle, especially at the first start-up of the day when the engine is dead cold.

However, Marc increased my idle to about 850 to help with smoothing the idle, and that all but eliminated it.

As far as the rattle itself goes, it sounds like marbles rolling around in the transmission. It is noticeable? Yes. But, is it annoying? Well, that is subjective, and except for a cammed LT5 it is very subtle with good injectors and 850 rpm idle, IMO. (Note: My NOS injectors succumbed to alcohol in an insidious manner over a couple years. After replacing them, one of the unexpected bonuses was the near disappearance of the trans rattle.)

[Hog]

If I'm reading this correctly, it looks like there is a difference of less than half a point in both HP and torque at peak. That probably falls within "variances between runs" anyway. Unless there's something else that I'm missing? Thanks!

Lets make that a bit bigger.
http://i1202.photobucket.com/albums/bb373/Paul_Schermerhorn/portthrottles_zpsa2a0f9f3.jpg (http://s1202.photobucket.com/user/Paul_Schermerhorn/media/portthrottles_zpsa2a0f9f3.jpg.html)

From one of my previous posts, much more than 1/2 a point at the power torque peaks. Make sure you are NOT comparing teh numbers noted on teh actual graph, as they are giving power/torque numbers at 3900rpm which is NOT a peak for any of the curves. For peak outputs compare teh actual numbers at the top of the graph labelled MAX POWER/MAX TORQUE.


"You can see the torque advantage of 30 lb/ft at 2600rpm for the closed Port throttles, but at just 4500rpm, the Closed Port Throttles give up roughly 45hp at 4500rpm to the open Port Throttles. At this same 4500rpm, the CLosed Port Throttles are all done and power falls off abruptly after than as airflow is choked off It should be noted that the low rpm torque difference between the Open vs. Closed Port throttles would increase if the dyno run was started at a lower rpm.
It appears to be a significant low rpm difference between Open and Closed Port Throttles.

The Open Port throttles continue to build another roughly 125hp from 4500rpm to their peak of 469hp at 6600rpm or so.
All totalled the Open Port Throttles are worth an extra 160hp vs the Closed Port Throttles.(469 vs 309hp) and an extra 428 lb/ft of torque (417 lb/ft vs 389 lb/ft) when the entire vastness of the LT5 rpm range is considered."

To keep or remove the Port Throttles, THAT is the question. And the true answer for you personally is exactly at what rpm you drive.launch/cruise. Get under 2000rpm and the torque difference gets larger, at least on the graphs.

Basic answer to one of your questions, no, you cant retain your "power key" function once you delete your Port Throttles.

[Paul Workman]

The graph below is veering OT, but with regard to PORTING in conjunction with removing the SPTs, one of the myths so often bantered is how opening up the runners will slow velocity and thus "kill" low rpm torque. Bullshiet!

Apparently, the LT5s (especially the 90-92s) were starving for air (something addressed, perhaps, with the Gen II LT5 that was destined for the 95 ZR-1).

http://i185.photobucket.com/albums/x220/6PPC_bucket/tech%20files/12-27-09002Large.jpg (http://s185.photobucket.com/user/6PPC_bucket/media/tech%20files/12-27-09002Large.jpg.html)
http://i185.photobucket.com/albums/x220/6PPC_bucket/tech%20files/IHporting001.jpg (http://s185.photobucket.com/user/6PPC_bucket/media/tech%20files/IHporting001.jpg.html)

This graph depicts the torque plotted for my stock LT5, and after being fully ported. The motor retains the stock cams AND throttle body (see my signature for more details).

http://i185.photobucket.com/albums/x220/6PPC_bucket/Dyno%20graphs/Dynographs_zps723fdad7.jpg (http://s185.photobucket.com/user/6PPC_bucket/media/Dyno%20graphs/Dynographs_zps723fdad7.jpg.html)

For planning purposes, removing the SPTs in conjunction with porting appears to buy back the 25+ pounds of torque advantage through 4000 rpm when in NORMAL power mode. And, of course, above 4000 rpm torque comparisons for the ported LT5 simply runs away from the stock performance. What a shame Graham's new GEN II LT5 baby never saw the light of day. To use a phrase borrowed from Mike 100, there's a lot of "low hanging fruit" available with the LT5 - and 500+ hp is possible w/o compromising the nikasil liners or stock cams; i.e., the reliability.

[Hog]

Was the OBD2 LT5 engineered for roller cam followers, I cant remember?
EDIT-The mods I was referring to were part of the planned 1995MY upgrades to 475 bhp, that ended up being as tillborn project, unfortunately. It was incorrect for me to refer to the 1995MY upgrade engine as the "OBD2" engine although the upgraded engine would have required OBD2 qualification for MY1996.

[A26B]

........... The idea of going to the lightweight flywheel does intrigue me but I don't want "gear rattle." Or at least I don't think I do...what does it sound like exactly, and do guys have a problem with it after this switch?

Thanks so much for taking the time!!

I also have the 13# Fidanza Flywheel in my 94 ZR-1 with a 415 LT5. Cams are moderately "lumpy." I don't have any trans gear rattle as long as the clutch is depressed. I do have gear rattle when it's in neutral and the clutch is engaged.

The gear rattle is of no consequence to me because I am seldom ever in the car with the clutch engaged, in neutral. Some folks do that at stop lights, I don't.

The lighter flywheel takes a little street driving adjustment because of the lighter rotating mass & faster spin-up. Likewise, if you are drag racing, the correct launch rpm & clutch release is more critical, walking a fine line between bog & excessive wheel spin.

Doug Rippie used to offer a 24# iron LT1 flywheel for the LT5 that was popular. It helped mitigate the street driving & drag racing issues while shedding several pounds from the D/M flywheel.

I would expect the heavier flywheels would also help reduce the transmission rattle.

Fidanza 13# (alum billet)
Jerrys Gaskets 18# (alum billet)
Jerrys Gaskets 22# (alum billet)
Stock D/M 33#
McLeod (I don't know the weight, guessing around 16~18#)

[A26B]

Was the OBD2 LT5 engineered for roller cam followers, I cant remember?

I don't know if the OBD2 is the same as the 95 MY 475Hp LT5 that never made it to production, or not. If it is, the answer is no.

[WARP TEN]

I also have the 13# Fidanza Flywheel in my 94 ZR-1 with a 415 LT5. Cams are moderately "lumpy." I don't have any trans gear rattle as long as the clutch is depressed. I do have gear rattle when it's in neutral and the clutch is engaged.

The gear rattle is of no consequence to me because I am seldom ever in the car with the clutch engaged, in neutral. Some folks do that at stop lights, I don't.

The lighter flywheel takes a little street driving adjustment because of the lighter rotating mass & faster spin-up. Likewise, if you are drag racing, the correct launch rpm & clutch release is more critical, walking a fine line between bog & excessive wheel spin.

Doug Rippie used to offer a 24# iron LT1 flywheel for the LT5 that was popular. It helped mitigate the street driving & drag racing issues while shedding several pounds from the D/M flywheel.

I would expect the heavier flywheels would also help reduce the transmission rattle.

Fidanza 13# (alum billet)
Jerrys Gaskets 18# (alum billet)
Jerrys Gaskets 22# (alum billet)
Stock D/M 33#
McLeod (I don't know the weight, guessing around 16~18#)

I took the opposite approach with regard to the flywheel when Marc did his 510 package. I stayed with the dual mass flywheel because unlike Jerry and others, I do put the car into neutral every time when I come to a stop. It is easier on both my leg and the throw out bearing. I have heard the gear rattle on other cars and I do not like it. As a result, my 510 package is technically about a 500 package but anyone who wanted it all could install a Fidanza. I have also heard some people complain that the lack of mass in the Fidanza sometimes makes getting off the line more difficult. As I recall Marc said a stock dual mass flywheel will handle up to about 550 hp.

I also had the secondaries removed when Marc did his work and I notice no issues without them. The car runs strong and although Marc and others say you do lose a little low end torque, I certainly don't notice it.--Bob

[Hog]

I don't know if the OBD2 is the same as the 95 MY 475Hp LT5 that never made it to production, or not. If it is, the answer is no.
I just wanted to add a correction.
This engine should have been referred to as the MY1995 "upgrade" engine. It never made it to production as MY1995 was the last year of ZR-1 to be built, not the OBD2 engine as I did. The 1995MY upgrade engine would have had to qualify for OBD2, just like the LT1's did. Chev. was preparing for OBD2 in for MY94/95 with the introduction of the flashable ECM/PCM's.
To certify the 95MY uprgrade engine would have required a substantial effort, probably including a new ECM to include the missfire detection the OBD2 requires.

The lifters/followers were not rollers, 2 test mule engines were built either with a special Lotus lifter, or using camshafts that were developed FROM the info supplied from the Lotus piece.
The Lotus hydraulically variable device that fit into the space of the OEM lifters and would switch profiles to boost low rpm torque(the lack of was often criticized) and an upper rpm breathing to 475 bhp profile. But again my interpretation of Mr Behans report of the 2 1995MY upgrade engines isnt clear, the engines either used the Lotus variable lifter device as part of the 95MY upgrades, or used cam profiles with conventional LT5 valve actuation equipement, that were derived from testing with the Lotus device installed.

[Billy Mild]

Was that dyno of a stock car with the secondaries removed? If so I need to rip that out ASAP on my 1991. 469 WHP at the wheels is impressive.

[Hog]

Was that dyno of a stock car with the secondaries removed? If so I need to rip that out ASAP on my 1991. 469 WHP at the wheels is impressive.
I doubt these were chassis dyno numbers, but engine dyno numbers. I really wish there was a date on this graph

No that was the same engine, and same configuration. One pull with the port throttles closed for the whole pull overlayed by a pull with the port throttles open. As you can see, port throttles open allows excellent upper rpm breathing, PT's closed, no upper rpm power, but more torque(30 lb/ft)and growing) at 2500rpm.

This was a full open vs closed port throttle exercise. You gain 160hp and 30 lb/ft torque by having the port throttles OPEN vs. CLOSED.
The graph is really showing what happens when you turn that "Power Key". Obviously you want them opening if you are driving, maybe not if you are letting Junior take a date out in your car.

.

[Billy Mild]

How hard is it to eliminate the Secondaries? If I get my intake manifold off I only want to do it once, not multiple times. If there is power to picked up that is not costly here I would like that.

[Hog]

How hard is it to eliminate the Secondaries? If I get my intake manifold off I only want to do it once, not multiple times. If there is power to picked up that is not costly here I would like that.
I believe that power simply from removing the port throttles would be minimal, other reasons for their removal would carry more weight.
I suggest reading this entire thread and theeh other on Secondary removal, removal of secondaries, or secondary port throttle removal.

It also makes sense to do all maintenance work that can accomplished once you get the plenum pulled.

Others will have more valid input than myself.