Removing Secondary Vacuum System questions.

[32valvZ]

So what exactly would be a good reason to do this if everything is working properly?

[rudolph schenker]

Originally Posted by 32valvZ

So what exactly would be a good reason to do this if everything is working properly?

[XfireZ51]

Originally Posted by DScott600

Oh and in response to John Boothby I'm sure that running without the secondaries would effect emissions. Marc told me that the main reason GM did the secondaries is for emissions. But I'm sure the experts may chime in on this one.

Could have been for gas guzzler tax with the drive cycle performed using primary runners only. 2nd Gen LT-5 was eliminating secondaries.

[Paul Workman]

Originally Posted by 32valvZ

So what exactly would be a good reason to do this if everything is working properly?

Reliability, simplicity, and more air flow!

After alcohol-sensitive injectors, or injectors in general, it would be my observation that issues with the secondary control system is the second (if not the first) issue related to LT5 reliability - a WAAAAY over engineered solution to a "problem" that might have been overcome (and was on the GEN-II LT5) another way.

For example:

• There are 4 separate signal lines from the ECM controlling 4 separate relays each controlling (yet) a second pair of injectors; 24 connections in all, not counting the relays themselves.**
• There is the vacuum pump that initially charges the system and maintains vacuum as the secondaries are opened and closed (in spirited driving).
• Then there is the check valve and (old) rubber connections, plastic lines, the reservoir, solenoid, and let's not forget that the actuators should to be balanced to work in unison.

In my case, I concluded that
the air flow disruption was a consideration in the quest for HP,
throttle response is improved w/o all the stuff that needs to be actuated, espcially when all injectors are working all the time - no lag,
and since all the vacuum "stuff" could be eliminated and removed along with all the stumbling, and high idle, crap that goes along with something failing in the vacuum secondary system
the KISS principal.

So, except for a NCRS car, my question was why keep all that nonsense and the potential for complicating the troubleshooting aspect of maintaining the LT5?

The one item left to be eliminated (by me) is electrical. It stems from the way chip I have installed operates. The engine now depends on all injectors to be running - each injector sharing the load demand. If for any reason, and there are several, that the ECM should turn off the secondary injectors, some serious leaning would result and one would have to "limp home" until the problem was corrected.

So, the solution would be the equivalent of latching the secondary relays closed all the time or connecting the primary and secondary injectors in parallel - so they work as "one". The jury is still out on this - but I think Marc H agrees it may remove some potential for harm should some or all of the secondary injectors suddenly quit.

All that said, I couldn't find a reason NOT to remove the secondary actuation system. Of the 6 of us sitting at the table last week, I believe only one of us still was using the stock secondary system. The rest had removed all of the hardware, or tie-wrapped them open. As to how we liked running w/o the system, it was unanimous that we did prefer NOT having the secondary system installed.

Looks tell the story: Simple is a good thing!



FWIW,

P.

[tpepmeie]

Originally Posted by Paul Workman

So, the solution would be the equivalent of latching the secondary relays closed all the time or connecting the primary and secondary injectors in parallel - so they work as "one". The jury is still out on this - but I think Marc H agrees it may remove some potential for harm should some or all of the secondary injectors suddenly quit.

Or, disable the program logic which would ever cause the secondary injectors to shut down.

Or, implement a substantially lower rev limit (say 3000 rpm) in the event the secondaries are commanded shut down.

Different ways to skin this cat.

Todd

[DScott600]

When I read about and look at the LT5 it is a marvelous engine. The only thing that really bothered me was the secondary system. It looks like a last minute cobbled together idea and it is way over complicated. In the late nineties I had a 1996 mustang cobra. They had secondary throttle blades too that opened up at 3250 RPM. They were used for low end torque. The system was much simplier, they had plates between the intake and heads that were operated from a control box under the intake. It was a compact design and if you wished to eliminate it you pulled the intake to do so. In 99 Ford changed the design of the heads so that the system was no longer needed and they haven't used it since. My point is the system could have been similar to fords and we would have little to know issues with it. And everyone who has done it says that you notice no torque loss and even Marc says that it was for emissions. The Ford design was for low end torque but even they went away from it when they redesigned the heads to promote better low end torque.

[32valvZ]

I see the pros to the removal of all the secondary components if theres problems with it. However, I may be in the minority here, but I believe my secondary system is working just fine. When I did my injectors and coils etc., I replaced both the vac cans with new, tested units turned the right way of course. In addition to that, I silicone sealed any questionable vacume connections and zip tied all the others with the appropriate sized ties.

My secondary engagement is just about seamless. I guess if I start experiencing problems with it, I might want to do the removal procedure. For now, I'm happy with the whole set up as it is.

[xxxscimitarxxx]

I have got vaccum problems now so was looking to replace all my secondary gear ....'all of it' on the basis that lm in the UK and knowing my luck the one part l wouldnt order would be the part l needed ( and there arent corvette spares on every corner in UK.....so

if l go the secondary actuator delete route...l more or less dont buy anything apart from plenum gaskets and l get a more reliable and simple fuel injection system....so

a couple of Qs

is it as simple as ripping out the vac plumbing, jumping the power and signal wiring from the primary injectors to the secondary injectors, tying open the secondary throttles

If not....then is there a 'step by step with pictures' available for this job....or can someone please send me a napkin schematic

what happens to the ECU outputs....codes, CEL other nasties that the ECU might do to the cars performance

are other engine data sensors affected which then provide bad signals to the ECU

But all in all....this sounds good to me....and Im a firm believer in KISS

(so why did l buy a ZR1 .....)

Oh yes I know why...they go great....sound great....look great....and have lots of interesting moving parts (some of which it seems l will now remove)

Any additional help to the above would be appreciated

Dave

[secondchance]

Originally Posted by 32valvZ

I see the pros to the removal of all the secondary components if theres problems with it. However, I may be in the minority here, but I believe my secondary system is working just fine. When I did my injectors and coils etc., I replaced both the vac cans with new, tested units turned the right way of course. In addition to that, I silicone sealed any questionable vacume connections and zip tied all the others with the appropriate sized ties.

My secondary engagement is just about seamless. I guess if I start experiencing problems with it, I might want to do the removal procedure. For now, I'm happy with the whole set up as it is.

I am in the same boat. I finally got everything sorted out. I have this fear of something going awry due to removal. Also, VA emission test.

[Paul Workman]

Originally Posted by xxxscimitarxxx

I have got vaccum problems now so was looking to replace all my secondary gear ....'all of it' on the basis that lm in the UK and knowing my luck the one part l wouldnt order would be the part l needed ( and there arent corvette spares on every corner in UK.....so

if l go the secondary actuator delete route...l more or less dont buy anything apart from plenum gaskets and l get a more reliable and simple fuel injection system....so

a couple of Qs

is it as simple as ripping out the vac plumbing, jumping the power and signal wiring from the primary injectors to the secondary injectors, tying open the secondary throttles

If not....then is there a 'step by step with pictures' available for this job....or can someone please send me a napkin schematic

what happens to the ECU outputs....codes, CEL other nasties that the ECU might do to the cars performance

are other engine data sensors affected which then provide bad signals to the ECU

But all in all....this sounds good to me....and Im a firm believer in KISS

(so why did l buy a ZR1 .....)

Oh yes I know why...they go great....sound great....look great....and have lots of interesting moving parts (some of which it seems l will now remove)

Any additional help to the above would be appreciated

Dave

It IS as simple as removing the secondary vacuum pump associated hardware, actuators, and even the friggin throttle plates too!

You don't need to be jumping anything. I Just pluged in a Marc Hiabeck chip programed for cars sans secondary "system". Marc's chip also provides programming to better control the cooling fans, fix the high idle, optimize engine performance for higher operating temps, anti-backfire when using long tube headers. I'm VERY pleased with how the car performs now with the new calibration, as compared to stock. Smooth and very responsive, and no change in my fuel mileage...except maybe 1/2 a mile better w/ cruise control running! (28.5 mpg).

P.