Hauntingly familar secondary failure #3

[Schrade]

That moth has some pretty nasty fangs!

[GOLDCYLON]

Originally Posted by Schrade

That moth has some pretty nasty fangs!

Yes the screw with you moth

[Paul Workman]

Originally Posted by efnfast

Guess I'm sold when it comes time to do the heads.

No need to wait to do the heads. Two ways to go:

If you wanna try it but be able to revert, you can simply zip tie the actuators open and substitute the appropriate calibration (chip).

Or, for optimum performance, or where porting results in expanding the runner size beyond the stock diameter, for instance, the plates and rods can be extracted inside an hour, once you have the plenum removed.

On a 90, as a precaution, you'll want to place a jumper across the POWER switch so that it is always in FULL POWER mode. If you have a 91-95, the chip calibration can be changed to always be in FULL POWER mode.

Aside from you questions regarding what the down sides are, you didn't even touch on what the upsides are, and has anyone ever reverted back to reactivating the SPTs (for other than possibly a new emissions compliance problem). For that there are many UPSIDES to eliminating them:

Both intake valves are constantly washed in fuel, keeping the clean!!
Reliability! Parts that don't exist, don't fail, and don't cost anything.
Throttle response(!) as there no longer is any transition lag.

I've been without 'em for 4 years now, and love the way it runs. I'd go kicking and screaming if I had to reinstall them (assuming that was an option - which it is NOT in my case...)

[GOLDCYLON]

Originally Posted by Paul Workman

No need to wait to do the heads. Two ways to go:

If you wanna try it but be able to revert, you can simply zip tie the actuators open and substitute the appropriate calibration (chip).

Or, for optimum performance, or where porting results in expanding the runner size beyond the stock diameter, for instance, the plates and rods can be extracted inside an hour, once you have the plenum removed.

On a 90, as a precaution, you'll want to place a jumper across the POWER switch so that it is always in FULL POWER mode. If you have a 91-95, the chip calibration can be changed to always be in FULL POWER mode.

Aside from you questions regarding what the down sides are, you didn't even touch on what the upsides are, and has anyone ever reverted back to reactivating the SPTs (for other than possibly a new emissions compliance problem). For that there are many UPSIDES to eliminating them:

Both intake valves are constantly washed in fuel, keeping the clean!!
Reliability! Parts that don't exist, don't fail, and don't cost anything.
Throttle response(!) as there no longer is any transition lag.

I've been without 'em for 4 years now, and love the way it runs. I'd go kicking and screaming if I had to reinstall them (assuming that was an option - which it is NOT in my case...)

Thanks Paul was hoping you would chime in.

[efnfast]

Better air flow without the plates and rods in the way? I would assume yes, but a measurable difference?

[GOLDCYLON]

Originally Posted by efnfast

Better air flow without the plates and rods in the way? I would assume yes, but a measurable difference?

Mr. Haibeck documented about a second delay from command of a full throttle action to the actuation of the secondary systems for one. With no secondary's to open... no delay.

[chriskinzel]

I'm in the process of removing my secondaries. Just pulled the shafts today with a new tool. It is a vice grip that has a slide hammer attached to it. Slicker than bacon grease! I put a nut on the shaft and with 3 hits from the slide hammer the shaft is out. Under 5 minutes to remove all 8. The shafts are bent, and unsealable, but so what I am throwing them anyway. I have got ant inspection camera and I will be checking all cylinders before reassembly. All of my screws are accounted for. (Maybe not all my marbles though).

[PhillipsLT5]

Mine are long gone, great

[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.