I tried posting this on several Nissan boards, but nobody seems to know what's going on. Have any of you guys here dealt with this "preload" process before? I've never seen anyone have to do it before.

--
Hi All:
A friend of mine has a 92 300ZX and purchased some JWT Sport 500 turbos from a forum member here. Before installing them, he had them rebuilt by Turbo City.

The turbos did not come with actuators, so he gave JWT a call. JWT does not sell the actuators separately. Their response was that they use modified OEM ones. They said to take the stock actuators and chop a 1/2" section out of the actuator rod. Then use a die to thread the 2 rod ends and use a turnbuckle to connect the 2.

The shop doing this work was able to do all of this, but something is still not quite right. The turbos spool incredibly slow and even with the boost controller completely max'd out, boost only reaches 15 psi.

JWT said, "The actuator preload needs to be set to 12 psi".

The shop says that they did this, but I don't know how they determined it. Has anyone here done this preload operation? I assume it means that you do the following:

1) Install turnbuckle as described above
2) Pressurize wastegate actuator to 12 psi
3) If actuator opens before 12 psi, tighten turnbuckle and try again. If actuator does not open at 12 psi, loosen turnbuckle and try again.

If anyone can shed any light on this subject, it would be GREATLY appreciated. This project has turned into a nightmare in terms of the time and money involved!

Thanks,
Sonny
--

Thanks,
Sonny

 

I would remove the boost controller and peload the acuators in actual service until the motor gets 12lbs. That way you are using the same pressure source (boost perssure) it will see under operation rather than a pump. This might eliminate some variables you may not be adressing.

another problem might be that the flapper is not closing completly regardless of the actuator preload. Is the bypass/blow off valve leaking?
Also were the compressor housings clocked in a way that it might bind the actuator and prevent it from closing? check to see that the rod is not rubbing on the hole in the end of actuator can.