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Discussion Starter #1
Thought Id share the knowledge with you guys as Id never come across this phenonemon before and perhaps it might help some of you with various problems you might be having.

Anyway, first of, my dilemma....Im running at the moment a rb25 with a T78 setup, fat injectors, rail and all that, and for months the lowest I could get it to boost at was 1.5/6bar, external gate wound all the way out, top pipe to gate off etc...and it was annoying, the spring in the gate was a 1.2-1.7bar sping, and nothing I did would allow me to lower the boost (1.5bar ALL the time is a bit of a handful, specially in the wet and RWD)

In the end I got fed up, and bought me a 0.8-1.2 bar spring instead, hoping it would solve the problem...nope, lowest boost then was 1.1 and some boost creep.

Pissed off indeed, as the engine thats in atm is a temp for getting around (blew the previous rb25) until I can pick up the rb30, its only got a normal nissan internals, gasket ect so I only want to run 0.8 bar MAX.

After much messing around under the engine bay, I thought Id take off the pipe that goes from the throttle top to the wastegate and give it a bit of a blow incase theres any crap in it...nothing, was as easy as blowing down a inch bore hosepipe. Then I turned it around, pipe on the nipple that it connects to, and blow down that (throttle body is clean btw).....holy ****! No chance of blowing down that without the lungs of a whale!

Concerned I tried a few other pipes in various places around the bay, some were extremely easy to blow air down, others were almost impossible.

Id never come across this before, and ive worked on many engines, so all I can guess is that some piping points on an RB are vacuum only (sucking on the pipe resulted on a flow of air :confused:)

Back to my problem, I changed the piping to the boost controller and wastegate so that it piped into a "free flowing" pipe, and TADA!!! 0.8bar steady on a test run!

So when plumbing in new stuff, or boost senstive item, give the piping a bit of a blow and make sure its free flowing, otherwise you could end up with a nasty result!

Also, plumbing of many items into a good flowing line doesnt make any noticable difference to the result (it still behaves)

I guess something like this "could" also cause boost spiking as well as creep and higher than expected boost.
 
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