Secondaries? Pros and cons?

[We Gone]

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

[XfireZ51]

Originally Posted by We Gone

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]

Originally Posted by 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?

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]

Originally Posted by 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?

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.