Boost dropoff issues

[omad]

Trying to get this car sorted and can't get the thing (thus far) to hold high boost to redline. It seems to dramatically drop off between 5-6k rpm.

It has:
NO boost leaks - tested to 25PSI
GT Pumps TD05 20G
stock cams
560 evo injectors
~2 inch fmic piping with evo3 cooler
evo0 throttle body elbow
stock J-pipe off turbo
fresh rebuild
A-spec so no cyclone
Edit: also has an action dan dump and 2.5" exhaust system.

Used a HDI EBC and a bleeder to atmo (nowhere on the intake currently to plumb it back)
Can get it up to ~1.5 bar but by the time it hits ~6krpm it's at about 1.1bar

Anyone got any ideas?

 

[provan]

what kind of boost controller are you using,

 

[iluszn]

Holding high boost is not about if you have a leak, its about air flow So you may have air flow issues. ie;

Intake Pipe
Air Filter
Air Flow Meter
Cat
Exhaust
Muffler
Waste Gate Actuator opening?

Can you outline the above ??

Have you tried running 1.1bar only and seeing if it holds through to redline? How much is it dropping by redline? is it getting lower as the revs get higher?

 

[to4garret]

~2 inch fmic piping

isn't that smaller than stock for an evo 3?

 

[omad]

what kind of boost controller are you using,

HDI EBC and a manual bleed - read first post.

Holding high boost is not about if you have a leak, its about air flow So you may have air flow issues. ie;

Intake Pipe
Air Filter
Air Flow Meter
Cat
Exhaust
Muffler
Waste Gate Actuator opening?

Can you outline the above ??

Have you tried running 1.1bar only and seeing if it holds through to redline? How much is it dropping by redline? is it getting lower as the revs get higher?

Intake - 2" (alloy) as above
if you mean before the turbo, it's injen style with battery removed
AFM - 3g
Filter - K&N Pod
Exhaust - Full 2.5" system as above. pretty sure it's a straight-thru barrell muffler.

NFI about the actuator.

It seems to hold steady (at least on the manual tap) as you increase. But once you get over 1.1 bar between 5-6k it drops off dramatically, mostly all in one hit.

isn't that smaller than stock for an evo 3?

NFI man. maybe slightly smaller.

 

[iluszn]

ok, So if I understood correctly, @ 1.1BAR it holds till redline? anything over 1.1BAR and it drops back down to 1.1BAR.

You have a restriction or bad wastegate.. I remember I had a bad bend in my cooler piping and it would not hold over 12psi. I replaced the bend with a nice smooth bend and I could run 16psi no probs.

If your intake (Prior to Turbo) is nice and smooth then I dare say it may be your intercooler piping. An easy way to test is with a second boost gauge. Have one gauge tapped into the line to your actuator (So before the cooler). Your other gauge goes off your Intake Manifold. Atleast then you can see the pressure drop between the two. If you are getting pressure drop due to your cooler piping you might see a big drop ie turbo pushing 1.5BAR but Manifold seeing 1.1BAR. that is err very drastic drop, usually your hoping for 1 - 3psi difference..

Worth a shot.. Can you post some pics of your engine bay, FMIC setup?

 

[to4garret]

its fuckin 2" intercooler piping!

 

[omad]

The thing that bothers me is that it dies off so fast and that my car with stock piping, j spec cooler and 14b holds 18psi almost to redline, maybe 2 psi drop and it's gradual, not almost instant.

 

[to4garret]

but 18psi on a 14B != 18psi on a 20g.

its almost like it is hitting a choke.

 

[rob323]

Block the bov return line off with a piece of wooden broom handle and see if that fixes your problem.

 

[omad]

Block the bov return line off with a piece of wooden broom handle and see if that fixes your problem.

Forgot to mention I tried this as well with the old bov, no change =( has the evo8 bov now which holds fine to about 25ish psi...

 

[rob323]

Pre-turbo piping collapsing at high rpm restricting airlfow?

 

[to4garret]

Pre-turbo piping collapsing at high rpm restricting airlfow?

its all metal

 

[rob323]

but 18psi on a 14B != 18psi on a 20g.

The boost pressure might be the same but you will be flowing a shit load more air from the 20g at that pressure.

Where are you taking your boost pressure reading from?

 

[omad]

From the manifold. Same line as the fpr I believe.