Tial Bov interstate flutter.
Evolved Member
Joined: Jan 2007
Posts: 611
Likes: 0
From: MI
Thread Starter
Evolving Member
iTrader: (15)
Joined: May 2006
Posts: 271
Likes: 1
From: Clarksburg, West Virginia
Well the car will surge under light throttle also if I try to hold the car steady at 70mph with out the cruise. So I'm in and out of the gas to stop the surging. It does it whether I'm in the gas or letting off of it.
Evolved Member
Joined: Jan 2007
Posts: 611
Likes: 0
From: MI
that may be related the chop throttle on the cruise control
omg please read my post. i solved this issue before with my X. cable throttle ftw. also bigger turbos that spool slower than stock dont do this as much. its mostly because of the fact that you are able to build boost so early but not enough to fully open the bov or at all. tial bov's are awesome so dont chop the bov's knees. just dial back the spool with a tune and you'll notice it less.
Thread Starter
Evolving Member
iTrader: (15)
Joined: May 2006
Posts: 271
Likes: 1
From: Clarksburg, West Virginia
omg please read my post. i solved this issue before with my X. cable throttle ftw. also bigger turbos that spool slower than stock dont do this as much. its mostly because of the fact that you are able to build boost so early but not enough to fully open the bov or at all. tial bov's are awesome so dont chop the bov's knees. just dial back the spool with a tune and you'll notice it less.
Evolved Member
Joined: Jan 2007
Posts: 611
Likes: 0
From: MI
the stock BOV leaks, recirculates some of your lbs/min so the engine is never getting everything the turbo is throwing, vs the TiAL...you get every lb/min of air that turbo is producing
The ECU will give it some throttle and then the turbo spools, overshoots the desired speed quickly and then the ECU cuts throttle. This causes the BOV to open slightly which then causes excess fuel which leads to bucking. The PID control is all setup around stock power levels and when you keep the turbo responsive but up the power greatly, the stock PID control for the cruise control is junk and causes terrible overshooting.
Now compound this with closed loop throttle control that is targeting a torque value and it's even worse.
My EVO VIII did this same **** going up hill on the MAF and Tial BOV. It WAS NOT compressor surge. The turbo would spool and it would accelerate too much so I'd let off the throttle like 10%. That throttle change creates a pressure differential across the throttle plate that is enough to make the BOV light on the seat and it WILL vent some air. This in it's self doesn't cause the bucking though, it's when the ECU dumps fuel for the air it counted that is no longer in the motor.
When I went speed density, the exact same conditions would CLEARLY cause the BOV to vent some air, but because it didn't dump fuel, it was perfectly smooth.
I love the Tial BOV, but it sucks if you have a MAF for this exact reason.
Evolved Member
Joined: Jan 2007
Posts: 611
Likes: 0
From: MI
You ever driven a car with cruise control and a responsive turbo?
The ECU will give it some throttle and then the turbo spools, overshoots the desired speed quickly and then the ECU cuts throttle. This causes the BOV to open slightly which then causes excess fuel which leads to bucking. The PID control is all setup around stock power levels and when you keep the turbo responsive but up the power greatly, the stock PID control for the cruise control is junk and causes terrible overshooting.
Now compound this with closed loop throttle control that is targeting a torque value and it's even worse.
My EVO VIII did this same **** going up hill on the MAF and Tial BOV. It WAS NOT compressor surge. The turbo would spool and it would accelerate too much so I'd let off the throttle like 10%. That throttle change creates a pressure differential across the throttle plate that is enough to make the BOV light on the seat and it WILL vent some air. This in it's self doesn't cause the bucking though, it's when the ECU dumps fuel for the air it counted that is no longer in the motor.
When I went speed density, the exact same conditions would CLEARLY cause the BOV to vent some air, but because it didn't dump fuel, it was perfectly smooth.
I love the Tial BOV, but it sucks if you have a MAF for this exact reason.
The ECU will give it some throttle and then the turbo spools, overshoots the desired speed quickly and then the ECU cuts throttle. This causes the BOV to open slightly which then causes excess fuel which leads to bucking. The PID control is all setup around stock power levels and when you keep the turbo responsive but up the power greatly, the stock PID control for the cruise control is junk and causes terrible overshooting.
Now compound this with closed loop throttle control that is targeting a torque value and it's even worse.
My EVO VIII did this same **** going up hill on the MAF and Tial BOV. It WAS NOT compressor surge. The turbo would spool and it would accelerate too much so I'd let off the throttle like 10%. That throttle change creates a pressure differential across the throttle plate that is enough to make the BOV light on the seat and it WILL vent some air. This in it's self doesn't cause the bucking though, it's when the ECU dumps fuel for the air it counted that is no longer in the motor.
When I went speed density, the exact same conditions would CLEARLY cause the BOV to vent some air, but because it didn't dump fuel, it was perfectly smooth.
I love the Tial BOV, but it sucks if you have a MAF for this exact reason.
my stock turbo DSM I've had since 1999 (and still have for some reason) and the 2002 WRX we had here as a shop car(gt2871R). No problems from either
I agree with tialsport and 03. The turbo is surging still due to the lack of requirement for air by the engine and the already spooling turbo. My txs rfl did this same exact thing, and once i lightened the spring it became more reliable in transient states. Basically you need to vent some air during transient situations for best drivability witg quick spooling setups. This is my preference for the greddy type s. Not hijacking a tial promotion here, its just my preference .. it functions like stock and holds boost!
The tial could very well be remedied with a spring adjustment. Sometimes bleeding a little boost is an increase in drivability worth taking.
The tial could very well be remedied with a spring adjustment. Sometimes bleeding a little boost is an increase in drivability worth taking.
Thread Starter
Evolving Member
iTrader: (15)
Joined: May 2006
Posts: 271
Likes: 1
From: Clarksburg, West Virginia
Should I get the tial qr so it will recirculate and get a softer spring or will a softer spring in my tial vta be ok? Any suggestions on what spring I should go with?
definitely sounds like your main problem is the bov spring is too stiff so the bov doesn't open at all when you reduce throttle at low boost, causing turbo surge. VTA with Maf is bad news for driveability, as it seems you have discovered.
convert your tial Q into a QR and get the hot pink (-3psi) spring and your problems will go away.
convert your tial Q into a QR and get the hot pink (-3psi) spring and your problems will go away.