Eliminating the secondaries

[Perry Mitchell]

Thanks guys. So I take it there are no videos or DVD's. I am sure I can figure it out with the info I have. Just thought it would be easier with more pictures.

[ZWILD1]

My car came with Marc's 510 package and the secondary delete. I have some questions about it. I was going to call and talk with Marc about it. I usually think of something later that I want to ask. Like how do the fuel pumps work? Normally the car would run on the primary pump until all the injectors come in play and the secondary pump comes on. So how do the pumps work when you are running on all 16 injectors all the time? How or what is done concerning the pumps?

[XfireZ51]

Originally Posted by ZWILD1

My car came with Marc's 510 package and the secondary delete. I have some questions about it. I was going to call and talk with Marc about it. I usually think of something later that I want to ask. Like how do the fuel pumps work? Normally the car would run on the primary pump until all the injectors come in play and the secondary pump comes on. So how do the pumps work when you are running on all 16 injectors all the time? How or what is done concerning the pumps?

Think of the secondary pump as an auxiliary pump. It comes on when the ECM calcs a need for additional fuel. Otherwise, whether on 8 or 16 injectors, the motor uses the same amount of fuel and the primary pump can supply that amount. If you're running 16 injectors, the fuel delivery is basically shared equally by both injectors.

[Paul Workman]

Originally Posted by -=Jeff=-

I still have my secondaries.. they still work fine

That's what YOU think!

[Dynomite]

Originally Posted by -=Jeff=-

I still have my secondaries.. they still work fine

My Secondaries are in super shape and my FULL POWER switch is working fine.
I did replace all secondary vacuum system for $100.

New Secondary Port Throttle Vacuum System

Originally Posted by Paul Workman

That's what YOU think!

Yes........that is what I think

I think it is a bit foolish to eliminate one of the most unique and selectable and functional options for the LT5 (The Full Power switch on the console).....

And just because you do not want to do a simple fix but rather do a more complex "fix" eliminating the secondaries

[ZWILD1]

Xfire, thank you I wondered if anything was changed with the delete. I read Marc's article about going with a single pump if your sending unit is in bad condition. I saw a nice reconditioned ZR1 sending unit recently on eBay for around $475.

https://www.ebay.com/itm/90-95-ZR-1C...0/264751696997

[-=Jeff=-]

Originally Posted by Paul Workman

That's what YOU think!

No, I know they work fine. They will work fine until they don?t work fine

Same with my fuel pumps

[Hib Halverson]

With a 350, I've never been a fan of deleting the secondary port throttles because it degrades dirivatility and decreases torque output on the low end.

During the 20 years I owned Barney, my purple '95, the two times I had trouble with the SPTs, I repaired them rather than eliminated them.

For a 368...maybe, bigger than that, yeah, I'd get rid of them along with appropriate cal changes.

[Paul Workman]

Couple of things from 11 years and counting, driving w/o SPTs...

Drivability:

1. From off idle (<~1%) to WOT, there is zero hesitation or lag. Throttle response is instantaneous and continuous from the instant the pedal meets the metal (or anywhere in between): nothing for me to dislike about deleting the secondaries there. As for throttle response, it is a subtlety I think is unmistakable, but perhaps has to be experienced to appreciate.
   
2. Parts that don't exist seldom break and they don't cost much! The second time my SPTs hiccuped, and this was before Jerry carried replacement parts, BTW, OUT they came; never to return.
   
3. Valve "coking", primarily on the SPT valves, is non-existent! This. like my primary valves were prior to the secondary injectors running full time, is the result of fuel always being sprayed on the (back side) of (all) the valves. That said, if one presses the accelerator above 25% or so while in FULL POWER mode (w/o having deleted the SPTs), and then one backs off to maintain a prolonged highway speed, one achieves the same thing, i.e., flushing the secondary valves and thus reduce the heavy coking that typically forms on the secondary valves.
   
4. Torque* In (stock LT5) NORMAL mode vs. the FULL ENGINE POWER mode, the torque is only ~10% more than the FULL ENGINE POWER mode, but ONLY to around 3000 RPM. Between ~3000 and 3900ish the torque advantage of the NORMAL mode drops to zero (difference). Above that point the FULL ENGINE POWER mode provides greater torque.)

Far as the intact SPTs vs. secondary delete practice goes, for the more aggressively ported 350 cid or one with 368+ cid, I have no primary/secondary comparison data to share.

That said tho, apart from this "delete" discussion, I do have the stock LT5 and (aggressively) ported "before and after" (Dynojet) data on my 350 cid LT5.

The pick-up in torque at WOT in the "after" scenario clearly mitigates or negates entirely the ever smaller (below 4000 rpm) torque advantage present in the NORMAL switched position.

All in all tho, aside from the unnecessary complexity of the SPTs AND the uniqueness OR "NCRSness" AND the advantages of deleting the SPTs, you'll have to decide. My wife's ZR-1 does not have SPTs, but is not ported to the point where reinstalling them wouldn't be practical if someone wanted to do so. But, I like the reliability and drivability that having deleted the SPTs provide. So, I'd never consider reversing the delete procedure.

Below is a Dynojet graph of an LT5 slightly modified by Lingenfelter (specific mods unknown). From this graph one can get an idea of the differences between the NORMAL and FULL ENGINE POWER settings. Also I included the "before and after" graph results of an Excel spreadsheet showing the FULL ENGINE POWER plots for rear wheel torque for my ZR-1 in stock and fully ported configurations.

[Perry Mitchell]

I removed the plenum yesterday and replaced all the injectors along with Jerry's improved fuel pressure regulator. All the secondary vacuum lines, reservoir, solenoid, actuators, etc. were also removed. I am going to wire the secondary linkage open after I determine the best way to do it. Any suggestions there? I was figuring to wire or use plastic ties to tie the linkage lever to the original canister mounting bracket. Is that how you guys have done it? I will reinstall the plenum today while waiting for my recalibrated prom from Marc which will be here tomorrow.