sidneyam

I've been reading about safety boost and I can't figure it out what the hell it is even though i've done hours of searching. I read that it can come with ECU code 34. I've actually had code 34, have I been running on safety boost the whole time without knowing? Does this safety boost crap always come on with a code 34?

ZLover4Life

Yes, code 34 means safety boost. If you have code 34 then you have safety boost, that's all there is to it. (You can't have a code 34 and not be in safety boost.)

The stock TB02/22 turbos have a wastegate preset of 6psi. The 300ZX has wastegate solenoids that act like primitive boost controllers, raising the boost to 9psi. When in safety boost (which occurs when the engine is not at operating temperature or the detonation sensor signals detonation below 3k rpms), the wastegate solenoids open and your boost drops to a maximum of 6psi, and your timing is retarded, all to prevent detonation.

Most common cause is a bad detonation sensor harness. If the det sensor or a temperature sensor are inoperative, they can also cause safety boost. Finally, if you're actually detonating (usually caused by low-octane fuel), you'll obviously end up in safety boost (and rightfully so).

sidneyam

Does safety boost only apply to turbo then? Because i have an NA 90 300ZX, so if i do the relocation of of the knock sensor will it still serve its purpose well or is it just a dangerous bypass?

ZLover4Life

Your timing is being retarded, resulting in reduced performance, even if you don't have turbos.

The engineers who designed the sensor put it where it is for a reason - the relocation is a bandaid fix. If you're considering that route, just bypass the damn thing, since it won't be effective either way. But if you want to actually fix it, pull the plenum and replace the harness and it'll probably be fine. If it's not an easy task for you, it's advisable to replace the censor, too, just to be certain you resolve the issue.

For what it's worth, I did the bypass until I was able to replace the harness.

sidneyam

I read about the plenum pull for this procedure so I wanted to know if it was absolutely necessaryto remove the timing belt in order to get to the lower parts of the engine in order to replace this sensor. Or can I just do this all while working through pulling off the top of the plenum without removing the timing belt.

ZLover4Life

You may be able to do it without a full timing belt removal. The detonation sensor is under the lower plenum, which has an idler pulley on it. If you loosen the lower plenum and pull the belt off the idler pulley (do not let the timing belt move from the cam gears - use c-clamps to prevent the belt from jumping a tooth, else you face lots of problems and/or more work), you should be able to remove the lower plenum and get to the detonation sensor without any further timing belt interference.

And as a plus, you can do both the injectors and your detonation sensor at the same time. Convenient.