I have a jdm b16 n just finished boosting it. Got it street tuned yesterday and my tuner told me i was losing pressure at high rpm. Im running off the waste gate spring and its a 10.2 lb spring. The highest the boost goes is 8.8psi and than slowly drops down to the 7's when at high rpm. My tuner said its because of my exhaust how its so small, its a greddy sp2 60mm. Is that true or is there something else wrong?

 

with boost, you want to expel the exhaust gas as efficiently and quickly as possible..

could be the exhaust being a restriction or exhaust manifold choking up.

Usually log manifolds dont flow well past 6g

 

Yea i have a log as well. Im keeping my exhaust cuz i love how quiet it is. Is it bad if i keep it? I will just up the boost to make my power goal is that fine?

 

i actually had my car tuned yesterday and i too have a boost leak, so i made a little home made leak down tester and found out that it was the throttle body shaft bushings that went bad! i don't know if it will help you, but it cant hurt to check it out.

 

Hm never thought i had a boost leak i will check that. My tuner just said its my exhaust being too small.

 

check around all your intake charge pipe couplers, it's probably leaking around one or more of those.

 

So this is probably a boost leak and not my exhaust being to restricted? I just noticed a little crack in one of the couplers on the intercooler going to the intake pipe. I will do a boost leak when i get home.

 

it's not because of your 60mm exhaust.

As friends told, check boost leaks.
Or maybe your turbo is too small.

 

I have a precision 60 trim turbo .60ar its not the turbo. This turbo is able to handle 500+. Can it be a leaking vacumm line? or a bad vacuum line?

 

so check the line from the turbo compressor to the throttle body.

 

If you have any small leaks at all it could be the problem.

 

The exhaust has nothing to do with it LOSING boost pressure, so forget that. When you're losing boost pressure at higher rpms, that means that one or several things need to be checked/addressed:

Narrow this list down and go from there.. THESE ARE ALL CAUSES OF THE CAR LOSING POWER at some point.


TURBO
-Foreign object or body in between the air filter and the turbo itself

-too much carbon build up in the turbine wheel (only if the turbo is pretty old)

-Turbo has worn journal bearings

-Turbocharger may have a leak in the compressor housing itself at higher rpms (due to loose bolt or cracked backplate)

WASTEGATE SYSTEM
-Wastegate spring is a bad mismatch to work with the boost controller (Meaning too low a spring with high duty cycle of wastegate..) but because you're so low a boost pressure, this is not likely

-Wastegate leak at a flange or gasket issue.


PIPING SYSTEM
-collapsing or restricted vacuum lines

-Loose clamp, flange, or bolts either on the turbo itself or the intercooler piping. ( I think this is the more likely cause)

-Intake manifold or exhaust manifold has cracked or has loose gaskets

FUEL
-Fuel pump doesn't have enough capacity to take the additional fuel when at Higher rpms.

-Fuel injectors could be worn or old

 

make sure you used the right spring in your wastegate... other guess is you're hanging the valves open... also whats sort of intake piping or filter is on the turbo itself?

 

Im using a .7bar spring which is 10.2lbs. When i street tuned the max i seen was 8.8. And at the moment im not using a filter for the turbo. I have to get a pipe custom made to fit a filter on it.

 

is your turbo damaged or have any shaft play?

 

boost leak... do those checks first... rule out the easy ones first...

 

What turbo?

 

what size external gate? what could be happening is since you are running off the spring pressure and have no boost controller in-line that at the higher rpms the drive pressure is much higher, causing the wastegate to creap open sooner when paired with the constant boost the wastegate port (nipple, whatever) is seeing. Try getting a ball-and-spring type manual boost controller and get it to sit 9psi.
Remember that drive pressure is still there.....

 

I did a smoke test yesterday and found a boost leak on the driver side intercooler coupler. I tightened it up today and checked everything else. Took it for a ride seems to hold boost for longer but still drops down to .6 bar when it should be staying at .7. Going to get a smoke test done again n see if it still leaks. Will keep u posted

 

if its still leaking after tightening it... put some hair spray on your finger and rub it on the inside of the coupler so it touches the charge piping... hair spray does a great job at sealing up some of those leaks for us poor folks that cant afford vanjen claps all the way around lol

 

haha if it still leaks i think its my clamps. I have 2.5" piping and i think the t bolt clamps are for 3"s cuz i tighten them all they way to where they cant even tighten anymore.