20 psi on 16 psi Spring Press when using TC compressor as source??

[turbo96max]

bouncy 18-20 psi on 16 psi Spring Press when using TC compressor as source on the boost gauge, but according to fuel psi , its a steady 20 psi ,, anyhow, i changed the vac source to a port on the dog house and got the steady 16 psi which is the spring pressure.


any idea why the difference? i had the vac line from the tc cover, to the bottom of the gate, and nothing to the top. same as i do now, just vac source is from the intake...

what do you guys think about the way the return dumps back into the dp. i personally didnt like it, i would have made it with a much better angle for better flow, but i dont have a welder or the equipment and paid a shop to do it, the guy swears it wont cause backpressure issues controlling boost of he will redo it... i guess i can live w it if it functions properly,, so far it holds 16 psi nicely

 

[Chuck Leeper]

"what do you guys think about the way the return dumps back into the dp."

It would have been easy to clock the w/g closer to 12 o'clock, and enter the dp at an angle a lot less than 90*.

I think if it entered further down the dp, flow would be better, too.

 

[1fast6]

looks like your welder is lazy.

 

[pacecarta]

what kind of hokey crap is that with the hose from the compressor to the gate , hard to tell but is that a factory gray tee in there
if you want lowest possible boost it should jut have a straight hose from compressor to base of gate , nothing in between .

any leaks in that will cause boost to be above the spring and by going to the manifold the available boost is less than at compressor which if anything should have resulted in higher boost
my guess is when you replumbed to the manifold you eliminated or sealed the leak that you had


as to the gate dump should be ok dont know the story but it could be that was the only pipe he had available to tie it in , did you provide the pipes to plumb the gate?
i would have come off the header at more of an upward angle than the straight tee that it looks like .. and then once the gate was done on the headers and the down pipe put back in he used what he had and rotated it to fit the dump side

btw what did you use to block off the wastegate hole in the exhaust housing , you did block it right??

 

[turbo96max]

what kind of hokey crap is that with the hose from the compressor to the gate , hard to tell but is that a factory gray tee in there
if you want lowest possible boost it should jut have a straight hose from compressor to base of gate , nothing in between .

any leaks in that will cause boost to be above the spring and by going to the manifold the available boost is less than at compressor which if anything should have resulted in higher boost
my guess is when you replumbed to the manifold you eliminated or sealed the leak that you had


as to the gate dump should be ok dont know the story but it could be that was the only pipe he had available to tie it in , did you provide the pipes to plumb the gate?
i would have come off the header at more of an upward angle than the straight tee that it looks like .. and then once the gate was done on the headers and the down pipe put back in he used what he had and rotated it to fit the dump side

btw what did you use to block off the wastegate hole in the exhaust housing , you did block it right??

well the line coming from the compressor is just joined together by an alumninum pipe, i didnt hear any leaks there, routed straigh to the gate.ill buy some line and route new line to the gate and bypass the pipe joint and see what that does.

i totally aggree, when i saw what he did i was pissed, he was totally lazy, and didnt care about doing it properly. he told me since i wanted to cut down on cost he did what he could without removing the header or the dp. i still see plenty of space where he could have implemented better angles, but at this point, as long as it hold boost properly ill live with it.

i plan on ordering the blockoff sandwich plate that rjc sells, for now the puck was just welded shut, so as if the original internal gate was operating just always closed. it builds boost fine, you think i should still get the plate ?

 

[RUQWKNF]

i plan on ordering the blockoff sandwich plate that rjc sells, for now the puck was just welded shut, so as if the original internal gate was operating just always closed. it builds boost fine, you think i should still get the plate ?

I would and here's why.
The downpipe puck actually moves / rotates on a rivet pin. Unless it was welded in place as well, there is a chance that the puck could still be blown open enough to cause some leaking and potential spool up issues. Running the block off plate would remove all doubt about sealing that hole closed.

At least that is what I would do.

Patrick

 

[pacecarta]

a plate might cause lineup problems for the gate with the gate plumbed off the header

 

[turbo96max]

a plate might cause lineup problems for the gate with the gate plumbed off the header

very true, with the plumbing done already things wouldnt line up, i will have to tap and plug the the hole on the housing

 

[bison]

The angle isn't going to matter. There isn't much backpressure at all at 16psi unless your mufflers suck. What is your target power level? I'm thinking backpressure on the other side of the gate will become your problem later when the power goes up it will push the gate open unless you replumb your wastegate. If the spring is 16lbs then the backpressure can't be anything if the valve is 1 square inch or greater suface area or the gate will crack open without any pressure on top of it at 16psi. I'm sure it's over 1 sq inch too.

 

[turbo96max]

The angle isn't going to matter. There isn't much backpressure at all at 16psi unless your mufflers suck. What is your target power level? I'm thinking backpressure on the other side of the gate will become your problem later when the power goes up it will push the gate open unless you replumb your wastegate. If the spring is 16lbs then the backpressure can't be anything if the valve is 1 square inch or greater suface area or the gate will crack open without any pressure on top of it at 16psi. I'm sure it's over 1 sq inch too.

well the car has a pitbull atr 2x 2.5 system, with a cutour on the dp. so let me see i understand what your saying. if i go up in boost, say 25 psi on good gas, i cant just put in 25 psi worth of springs and use the bottom port only.... i should keep the 16 psi and through a controller bleed boost to the top and increase the boost that way?

 

[bison]

well the car has a pitbull atr 2x 2.5 system, with a cutour on the dp. so let me see i understand what your saying. if i go up in boost, say 25 psi on good gas, i cant just put in 25 psi worth of springs and use the bottom port only.... i should keep the 16 psi and through a controller bleed boost to the top and increase the boost that way?

It's not that simple. There are 3 things to consider here. The pressures applied to the gate and the surface area the pressure is working on, the spring pressure, and the ex pressure pre turbo and the surface area on the wastegate valve the pressure is working on. There is a point where a stiffer spring will be needed because the ex pressure will rise a lot more than the pressure in the intake. There are a lot of things that can be done to overcome any issues that could come up. Your looking for linear boost. If it's linear either add some confrolled pressure to the top of the gate or increase the spring tension. Sometimes you have to do one or the other or both. There are other things that could be done by adding a controlled pressure to the top of the gate from an external source but there is no need to get into that here.