Having some spiking issues on my setup and i have been doing some research on google. the general consensus seems to be that the compressor housing is the best place to run the line for the bottom port on the wastegate. that being said, mine is hooked up there and im seeing 20 psi on 1 bar spring. this is with a holset hx35 with a tial 44mm wastegate. i dont see why the gate cant control the boost. my boost gauge is referencing the IM for its reading and it holds steady right at 20 psi. heres a pic of the manifold and gate placement

the only reason this bothers me is i just fixed an issue i was having with vtec not working and when i took it out for a quick pull in 3rd gear it hit the boost cut which is at 27. i took the gate apart before just to see what was up and why it was going to 20, i didnt see any tears or holes or anything out of the ordinary so i put it back together and put it back on. would like to get some feedback and see if i can't get this straightened out. ideally i would like to run my BBG at spring pressure in first gear, and thats not happening right now

 

after doing a quick google search i found some pictures of what the hx35 looks like and then i realized you had pics on here..



from one look at the hx35, id say its spiking because youve got a large turbo with only one wastegate...when i stepped up from a t3/04e .63 to a t3/60-1 .72 i needed to step up from a 38mm wastegate to a 44mm...id say odds are youre probably going to need a second wastegate or an even larger single if they even make one...i dont know because i havent looked myself..



good luck, im sure itll be fast as hell..

 

What are you controlling boost with? Did you pressure test the wastegate or just look at it?

 

right now the top port is open, otherwise i have s300 with a MAC solenoid. just trying to figure out what the deal is. i have no way to pressure test the wastegate, all i did was take it apart and make sure everything looked good. an hx35 isnt that big. i would think a 44 would be able to handle it. IIRC its a 55mm turbo. ive seen people use use 44mm gates on 6266's and only have it spike over maybe 3 psi over the spring.

 

anyone else?

 

Wastegate placement being less then ideal, and no tear drop, is most likely your problem. Try putting in a 8 psi spring, or removing the spring completely, and see if you still spike

 

ok, the only other spring i have is a small red spring which is a 4 psi spring according to Tial's info. if nothing else i will just have to order another one

 

A 4 psi spring would work, or just remove the spring all together.

 

Maybe take it to anyplace with an air compressor and test it?

Maybe by a mighty vac at harbor freight for 20 bucks and test it.

 

after moving the reference from the compressor housing to the intake manifold i now only have a spike to 17 on a 14psi spring. much more manageable than spiking way up in the 20's

 

It could simply be an issue of the valve not travelling far enough to bypass enough exhaust around the turbine.

a wastegate has only so much valve travel before you get into coil bind. the higher psi spring the thicker the coil the less the valve can travel.

this is why you see people stepping down to smaller springs. the spring physically has more travel before coil bind so the valve travels further and bypasses more exhaust.

 

have you plugged the two air ports on the waste gate body? The waste gate will not control boost with those open

 

IMO, locating the source of the wastegate on the compressor housing is the worst placement possible.

Why, because the air velocities at that area are insane and extremely volatile as far as turbulence goes. You simply will never get a clean signal there.

IM has a large plenum, much slower air velocity, and it tends to be fairly even flow especially if it's well designed.

 

^exactly. the air inside the compressor volute is very turbulent and uneven. this results in a lot of pressure wave pulses within the housing that can cause all sorts of issues.

the slower, more laminar flow within the intake manifold plenum is much better suited as a pressure signal.