info on turbos, leaks and EBCs from SZ

[canadian booster]

not sure if this falls under General or Technical..
it's an email from Greg @ Specialty Z with some good information in it on EBC's and turbo functions, i've asked permission already to repost from him

Sean,

The only thing that causes zero boost is one turbo that is frozen.
The Z has a crossflow intake manifold design that allows the left turbine to feed the right intake and the Right turbine feeds the left intake.
Because of the crossflow design, if one turbo does not rotate, it causes one side of the engine to have a huge exhaust restriction and the other side of the engine to have a huge intake restriction. Because of this design if one turbo is stuck, the engine can not produce any positive pressure.
Boost leaks can cause a pressure drop, but the engine will still produce some boost.
The boost controller has no effect on the engine/turbos producing base boost. No matter what is wrong with a boost controller, it will always make minimum wastegate pressure that the wastegates are preloaded to.
The wastegate actuator on the turbo has a spring that has a pre-load, that pressure is the lowest amount of boost that can be made if both turbos work properly boost is not leaking.
The boost hose going to the turbo actuator applies pressure when the car makes boost, when the wastegate actuator gets pressure that is more than the spring pre-load, it allows the wastegate door to open and routes air around the turbine wheel to keep from building more boost.
The boost controller only regulates the pressure going to the actuator to make the boost HIGHER. The boost controller can not lower the boost, but only raises the boost.
If the actuator does not get any signal, the turbo is going to make the max amount of boost possible until the backpressure blows the door open or the engine self destucts.
So when a boost controller fails, it will either make minimum boost by letting all pressure to go to the wastegate, or it will not allow enough air to get to the actuator and you will make too much boost.
Getting zero boost and having your boost controller flash makes no sense, if it did happen, it would be two different issues. The blitz only has a power, ground and vacuum/boost signal. Nothing else goes to the controller, so the only way the boost controller can flash red, is if it gets a boost signal high enough to flash, this would never cause zero boost as it can only drop to wastegate pressure for the lowest possible amount.

You can have full boost and no power, Moving air only makes power if you have the correct fuel to go with the air. So a drastic lean or rich condition can produce full boost and little power.

If the light flashed, my guess is it made more than 14 PSI, but the engine was not running well and it made you think it was zero boost.
If you truly did make zero boost, your turbo was at least temporarily stuck and not moving on one side.

[300ZXttZMAN]

Hmm so if you described it the same way to us as you did to him what is his bet????

[canadian booster]

i always thought turbos worked.. or didn't.. from what he's saying it's probably not the ebc messing up, but something else. I'm pretty sure the turbos are stock, and even after only 115,000km they're still 20+ years old and my compression reads were between 120 and 140.

i'll pull the engine, delete some stuff, reroute some other stuff, slap on some JWT500s and see how it goes. if i can avoid a rebuild i'd prefer to do that unless i can just use my internals and replace only the cylinder rings, but i doubt it since i've never heard of anyone doing that

[300ZXttZMAN]

No you need to rebuild the motor 120 and 140 is wout of spec i belive 121 is minium on tt motor with a maximum of 14 psi between cylinders...

[canadian booster]

i had 120, 130, 130, 130, 135, 140

time to build?

[300ZXttZMAN]

Yes I would..

According to the FSM, 120 is to low i mean the minium is 121 being at 120 is not to bad since it can vary if the engine was hot/cold also how accurate your compression tester is.. But since your pulling the motor you mine as well rebuild it...

But lets see what the others think..

[NissanFairladyZ32]

i had 120, 130, 130, 130, 135, 140

time to build?

Yes, the 120's and even 130s are low, a good running TT should have around 150 in all cylinders

[canadian booster]

guess i'll turn the EBC off and run low psi through the wastegate (5-7psi) so i don't damage her any further. she's going in for storage soon for winter, back out near the end of april probably, maybe i can do the engine work then.. $800 for block work + $2000 for engine internals is beyond my budget right now. booooo.

i guess if i sell like 1500 calendars i can do it!