exhaust manifold/boost problem

[mazdaspeed32007]

heres the scoop...

got a new exhaust mani. went for a spin after it was installed and my boost was only hitting 15-16 psi. (target 19) brought it back to the shop for a look see and sure enpough there was an exhaust mani leak right at the turbo housing. i fixed it. went for a spin on the way home tonight and sure as s***....didnt hit full boost.

my first question: can a small leak in the exhaust manifold cause boost loss?

second question: if yes to question 1, please explain to me because i thought the exhaust side had nothing to do with boost pressure....or is it because its on the front side of the turbo? im still confused.

this damn manifold has cause me nothing but problems. go medieval! its pretty though.

oh, and theres no other leaks in the fmic, piping, bpv.....anything.

i just figured the boost problems might have to do with the tune. i have a stage 2 tune but the exhaust mani isnt added to the tune. would that cause it to lose pressure?

 

[Remspeed3]

Yes a manifold leak would decrease your boost pressure, the turbine is not going to spin as fast if its loosing manifold pressure because of the decrease in exhaust gases passing the turbine itself...which would result in lower turbine speeds and a loss of power. The exhaust side turbine and compressor side are connected by a shaft and work as one unit, so thats the reason your boost pressure is affected. If you did in fact fix the leak, then your manifold is throwing the tune off...im sure it wasn't calibrated for the increased flow from the tubular manifold.

 

[mazdaspeed32007]

ill try the new tune today and see what happens. with all luck its just the tune. ill post back when i give it a go.,

 

[TheDoc]

I know a lot of Medieval manis shipped with warped flanges that will need to be decked prior to being usable.

 

[mazdaspeed32007]

yeaaaa....thats mine. new tune did nothing. yey. i get to do it AGAIN!

 

[Remspeed3]

yeaaaa....thats mine. new tune did nothing. yey. i get to do it AGAIN!

so the manifold is still leaking? if so sounds like the stock is a better choice...most of the time the aftermarket parts are a big pain in the a$$!

 

[mazdaspeed32007]

this is the first part ive ever had a "problem" with. this one is a super pita though. once i get it machined it should be alright. with all luck. ive done it 3 times so its easy to pull in and out now. like clockwork.