Boost all over the place

[ShawnR]

Standard draw-thru setup, but I have added an RJC boost controller. Drove the car to work today, and just like the last few times max boost was about 5-7 lbs when warmed up. Used to be around 12 max.

Coming home from work it was around 5, and then after getting off of the freeway it would get back up to 12-15 again. No signs of vacuum leak that I could find and it idles & runs fine.

Is it probably just the wastegate dying? Is there a decent way to bench test it?

 

[pacecarta]

the rjc has a check ball with a spring that has a cracking pressure of around 15psi so below that essential you have no pressure getting to the wastegate so its the wastegate spring vs backpressure only controlling boost
the spring in the rjc is around 15psi cracking because it was meant for use on 86-87 intercooled cars which can tolerate 15psi to prevent boost signal air from opening gate too early and IC cars came with a 10psi spring wastegate
if you want lower control youll need to change the spring in it for something weaker and check the cracking pressure with a regulated air source with a gauge

 

[b4black]

Did the low boost start when you added the controller?

The controller is a check valve. It holds back about 5 or so psi and let's the rest through to open the wastegate. There needs to be a small, controlled leak on the actuator side, otherwise the pressure stays there holding the wastegate open all the time. Pull the hose off between the controller and actuator and see if the boost is now correct. If it's correct one time, and then low again, you need to add a small leak to bleed off pressure.

The actuator has two sides, one for boost and one for vacuum. Pull the hoses off and see if either leaks. The boost side should push the rod out with about 5-10 psi. The other side (plumbed to the carb plenum) doesn't anything useful, often leaks and should just be disconnected (and capped off at the plenum).

 

[b4black]

the rjc has a check ball with a spring that has a cracking pressure of around 15psi so below that essential you have no pressure getting to the wastegate so its the wastegate spring vs backpressure only controlling boost
the spring in the rjc is around 15psi cracking because it was meant for use on 86-87 intercooled cars which can tolerate 15psi to prevent boost signal air from opening gate too early and IC cars came with a 10psi spring wastegate
if you want lower control youll need to change the spring in it for something weaker and check the cracking pressure with a regulated air source with a gauge

I believe this would cause high boost, not low boost.

 

[pacecarta]

the rjc has a small bleed hole on the wastegate side

 

[oddmonte]

The sooner you dump that hokey setup the better off you will be. Trust me!

 

[ShawnR]

The sooner you dump that hokey setup the better off you will be. Trust me!

Meaning the RJC controller? Or the whole carb/draw-thru setup?

Still gathering parts for the EFI build, but will be posting something soon to get opinions and I want yours because going Sniper is one of the options.



As for the wastegate/boost thing:

Pulled things apart and did some testing. (Watch the actuator arm and the pressure gauge)

Wastegate by itself starts opening around 6-7 psi.

WIth the RJC contoleer inline, it starts at about 12 psi. Pretty much just like it is supposed to.

I'll swap out all of the vacuum lines and if things are still wonky I will pull off the exhaust housing from the turbo and see if there is any crud on the puck over the exhaust hole.

 

[b4black]

Can you take the controller apart and clean it? My controller gets gooped up after a while and doesn't fully reseat (leaks internally). Our boost is mixture of air and fuel. The SFI engines are air only.