Question: zr1 less secondary port throttle valves what means?

[italian job]

Hi all; today I have my plenum removed because I had a suspect something on the secondary working not very well (not too much difference between normal and full power key position).
Looking inside the intake ports I probabily found the cause: secondary valves are not on their places.:ugh Someone removed the butterfly valves... I know many people do this job, but what are the results?
I understand removing secondary means engine will use all 16 intake valves also when in normal power key position, so we have a 32 valves engine at all times. This maybe sound good, but I'm not too sure is really a good thing.:confused

Also looking inside the ports I notice primary ports are clean but secondary ports are smoked, what this means?:confused

I want to restore original secondary port throttle valve working way, so I'm searching for all 8 butterfly valves, new or used.

Thanks

 

[jonszr1]

i may have what you need .could you take a couple of pics of you injector housings and under plenum area. so i can see what you need /and if i have it .

 

[jonszr1]

ps . all of my zr1s have brown secondary injector ports / its normal.why i dont know but it is normal

 

[italian job]

Just need all 8 secondary port throttle butterfly valves (the disc shaped items)
all other hardware is in place (fortunately)
You can take a look at first article on top of this forurm page:
"1990-1995 ZR-1 Secondary Port Vacuum Diagnosis" by Rob.
Last pic show one butterfly valve in place.

Please let me know if you have

Thanks

 

[italian job]

Marc Haibeck solved our mistery: Fuel does not flow from the secondary fuel
injectors until the throttle is opened about 25%.
That's why the secondary ports are dirty. It's the fuel that cleans the ports.


Thanks marc

 

[ernbuild]

what will happen if?

If you were to remove or have the secondry port butterflies open all the time , what would be the result, and would it do any damage to the engine in any way ?
Reason I ask is I replaced the secondry port solenoid only six months ago and has for some reason stopped working. NO I dont have a vacumn leak... Cheers Ern :confused

 

[Hib Halverson]

On a stock or near stock LT5, there is little advantage in removing the port throttles and driveability and fuel economy will suffer.

Now if the engine is highly modified and/or race only, then port throttle removal can gain a little power.

Sadly, replacing the port throttle hardware might be a challenge because of finding the parts may be difficult.

 

[italian job]

Hi Ernbuild, some months ago I finally has my secondary system working as original stock.
Here are my experiences.
As Hib said, there is really little power gain removing secondary system, and economy will suffer.
If you remove the butterfly valves or entire secondary system you can't damage the engine in any way, my Z does 15K miles less butterfly valves and no problems.
LT5 less secondary system run a bit strong when in "normal" but no gain in "full". Economy will suffer in "normal". So, removing secondary system is not useful.:ugh

Take a look on your FSM, there are many reasons because secondary system stop working. You may have no vacuum leaks but you may have electrical failure or ECM failure and other bad things.

what will happen if?

If you were to remove or have the secondry port butterflies open all the time , what would be the result, and would it do any damage to the engine in any way ?
Reason I ask is I replaced the secondry port solenoid only six months ago and has for some reason stopped working. NO I dont have a vacumn leak... Cheers Ern :confused​

 

[ernbuild]

Thanks guys, I actually wasnt going to remove the butterflies, just prop them open 'so to speak'. I dont want to take them out altogether.
I do a bit of drag racing and gymkana events with the car nowand although a bit of extra power may be OK, that wasnt the reason to have them permanently open. Just fedup with the hassels. There are only 12 ZR1's in Australia and finding anyone to work on them is near impossible. Hence I do most of the work myself, and the time to fix this problem is not an easy fix for me.
The Vette has a Haibeck chip, a huge set of headers and twin 3 inch system as well as a Fidanza lightweight flywheel. I also run 335 on the back for a bit of extra traction, and the old girl does very well at the different events I enter her in. The engine revs easily to over 8000 rpm's and does a high 12 second quarter. I do love the car but with the fiddley bits that keep playing up, the misses is now on my back to get a new ZO6 and I cant have two Vette's.
So back to my original question, will it do any damage if I for want of a better explanation, wire them open.???
Cheers Ern

 

[Hib Halverson]

If there is limited LT5 service in Australia, I'd be careful about running that motor to 8000 rpm. Stick to the factory rev limit of 7000 and that engine will last a lot longer.

 

[ernbuild]

Thanks Hib, You have warned me about that before, And it doesnt happen often, just me being slow to change the gears. Not as fast with the reaction time as I used to be. cheers Ern.