I would get a retune before playing around with that cutout open. There is a good chance your tune is far off if your old exhaust setup was restrictive.

 

Matt,

I got him to go for a test drive last night, His boost is spiking from 14psi (set) to 20psi with the cut out open. I believe his exhaust is somewhat stockish, atleast the muffler I know is. But, I do not own or modify his car so I'm not 100%.

 

Yea i'm sure it is just hitting boost cut most likely. It is probably running very lean though if the exhaust it was tuned on is close to stock in diameter.

 

True, but his car was tuned on 14psi. Not 20. LOL.

Something is causing it to spike, when the exhaust is open.

 

Yes that happens often when you open up the exhaust that much. What size wastegate and what spring is in there? Also how is the manifold design?

 

Tial wastegate
RC550 CC injectors
Master Power 57trim T3t4
Drag manifold
2.5 in downpipe
Drag intercooler and piping all flat black
Blitz BOV
P75 ECU on crome
Jumper harness 0bd2 to 0bd1
Walbro 255LPH pump
New manual boost controller
Car was Hennesey tuned on 10 psi



That's what I figured, but I'm curious to why it's spiking that much. I haven't physically looked at the car, just kinda tried to diag' it over the phone haha.

 

if i were him i'd turn the boost controller down with the cutout open then just drive normal with the cutout closed...

 

Please, please, please get a wideband on it to be sure it's not going lean. Especially if it's comming from a 2.5" full exhaust.

Removing a restriction in the exhaust will more than likely allow more air to enter the engine, a MAP based ECU has no way to measure airflow, just pressure. Air could be entering the engine that the ECU can't 'see', and as a result can't add fuel for it.

Give me a call if you don't know anyone with a wideband, or if you don't know what you're looking for. I'd really hate to see a motor lost over something easily avoided.

 

What size spring is in the wastegate?

 

Serious?

A) Drag manifolds aren't the best manifolds for controlling boost creep.
B) Opening up a exhaust from a small pipe to a big opening, is gonna allow the turbo to breathe more. Less restriction, more the motor can do work. If he had a boost controller, he could control it but that would defeat the purpose of the cutout.

Like Hennssey said, get hte bitch retuned. That is a big change in the tune. Not only is it on more psi but its spooling faster and I bet fuel isn't in the curve on the low side.