Hauntingly familar secondary failure #3

[4-cam]

I removed the secondarys about two years ago while I was porting my top end after reading a thread about the screws and engine damage that can occur. There was no way I was going to let that happen to me. I have corys chip for secondary delete and my 91 passed the IM240 treadmill test here in Colorado with flyin colors. Im not as confident on how its going to do with the SW headers and high flow cats that I am installing now. I did add air tubes and will be ceramic coating headers and cats to keep them nice and hot. I am going to do an emmisions test before we start the tune to see what a difference high flow cats make. Hopefully she will pass without issues.

[Franke]

Originally Posted by 4-cam

I removed the secondarys about two years ago while I was porting my top end after reading a thread about the screws and engine damage that can occur. There was no way I was going to let that happen to me. I have corys chip for secondary delete and my 91 passed the IM240 treadmill test here in Colorado with flyin colors. Im not as confident on how its going to do with the SW headers and high flow cats that I am installing now. I did add air tubes and will be ceramic coating headers and cats to keep them nice and hot. I am going to do an emmisions test before we start the tune to see what a difference high flow cats make. Hopefully she will pass without issues.

So you removed the secondary's and still passed the IM240 test here. That's good to hear as I was thinking about doing that very mod but was worried about the emissions. Did you remove the sec throttle bar as well or just the throttle plates? I am curious to see how well your Z will pass with the hi flows and headers.

[GOLDCYLON]

Originally Posted by 4-cam

I removed the secondarys about two years ago while I was porting my top end after reading a thread about the screws and engine damage that can occur. There was no way I was going to let that happen to me. I have corys chip for secondary delete and my 91 passed the IM240 treadmill test here in Colorado with flyin colors. Im not as confident on how its going to do with the SW headers and high flow cats that I am installing now. I did add air tubes and will be ceramic coating headers and cats to keep them nice and hot. I am going to do an emmisions test before we start the tune to see what a difference high flow cats make. Hopefully she will pass without issues.

It wont pass with the high flow cats on the treadmill. Been there done that with Jeal Headers. Sniffer all day.

[Paul Workman]

Originally Posted by zr-1.R1

excuse my ignorance, I am a neophyte.
if I remove the plenum, and the secondary valves, insert the liquid stop screws, pull the bolt, then the car will give me error 61? and I change gas emissions?

First, the ECM must be programmed for operating without the secondaries:

The new calibration will allow zero vacuum = OK (so no code 61)

At idle, only 1 injector is signaled "on". Above idle (>1%), the new calibration signals both injectors on but divides the dwell = 1/2 for each injector to provide the proper fuel.

Emissions might change. The tuning must be precise.

On a 1990, the POWER switch must ALWAYS = FULL POWER (VERY important!) For 1991-95 the ECM is programmed for the secondaries to always be "on".

All of the secondary circuitry may be removed (shown in PINK) and the plenum vacuum connection is plugged.

Note: On a 1990 ZR-1 the #11 "switch differential pressure" is located under the ECM. on 1991-95 the switch is under the plenum.

Note:...Please forgive me, but I don't understand what you mean by "insert the liquid stop screws, pull the bolt" = ???

Does this help?

[mike100]

I have not tested this in any way, but I think if one ran a fairly stock timing and fueling map to about 2400 rpm or so (the speed range of the typical smog check), one could pass running with open secondaries.

Maybe the combustion swirl would be wrong for the original EPA tests they do certifying cars, but for the typical inspection, I think it could do ok.

[Paul Workman]

Originally Posted by mike100

I have not tested this in any way, but I think if one ran a fairly stock timing and fueling map to about 2400 rpm or so (the speed range of the typical smog check), one could pass running with open secondaries.

Maybe the combustion swirl would be wrong for the original EPA tests they do certifying cars, but for the typical inspection, I think it could do ok.

One way to "test" it and find out once and for all would be to install a special gasket that covered the secondary ports and reinstall the stock chip and then test it again. The results would be quite illuminating.

[bradley]

my callaway 475 supernatural , drives better in every way with the secondaies removed .also since I have had them removed my mileage on the freeway has improved by 2 mpg .example , I go to see bill boudreau 3-4 times a year . before the secondaries were removed I got 21.2-.4 on a round trip now I get 23.5- 24.0 mpg on the trip. my car also has 4.10 gears

[HAWAIIZR-1]

Well, now I have another good reason to pull out the secondaries. I will wait until I get back to Hawaii, but I have been reading over the years about the pros and cons. I just figured like Marc said it not giving you problems then one could keep the system. Today while I was doing some final checks I saw the vacuum line snapped that goes past the oil filter to the vacuum pump. Not sure how long it was busted since I don't drive the car much and while not a big issue, I think I do finally want to yank all that garbage out and forgo the issues. It has been one thing or another over the years related to the vacuum system for the secondaries. I really wish I pulled them when I did the heads a few years ago. Oh well, thanks for all the information related to the issue to help me make a decision.

Tomorrow is my quest to find some hard plastic hose here in Japan to replace the broken line until I can get the car shipped back home in a few weeks. So far no luck and will try a large auto parts place and several home improvement on the way home from work.

[LGAFF]

Can you not get a section of rubber tubing to use as a connector and fix it that way?

[HAWAIIZR-1]

Originally Posted by LGAFF

Can you not get a section of rubber tubing to use as a connector and fix it that way?

Hello Lee,

Thanks for your thoughts and I do have some rubber tubing that I can use to repair as last resort until I can find the proper hard plastic tubing. It busted about right around the oil filter area near the rubber connected coming out from under the plenum. In fact, it busted before and I was able to take up slack to repair it the first time. I guess the hose is getting very brittle to just snap like that. I would have to imagine they sell that kind of tubing around here and I'll find out today.