What's the min wastegate pressure to be effective?

[Zmanco]

I'm currently running with a 7-8 psi wastegate and want to begin using Megasquirt to control boost. While it will allow me to run higher boost pressures, I also want to be able to limit to less than 8 psi when the TP is not WOT. I'm using the 60mm 240sx TB which is rather touchy (a little movement makes a big difference) especially in 1st and second. Limiting it to something less would make it easier to accelerate briskly without over doing it on the street.

 

I saw this picture in PaulR's post about about his turbo build where he dropped the opening pressure of the WG down to 5 psi. Note the ring with set screws that holds the spring on the WG shaft. I love it!

 

My question is how low can I set the WG actuator pressure via the spring and have it reliably keep the WG valve closed? I'm guessing it only needs to be a little more than the max exhaust pressure after the turbine in the WG housing? Do any of you have an idea what that would likely be? FYI, I'm running a Garrett T3/T4OE with internal WG and 3" DP and exhaust all the way back.

[Evan Purple240zt]

Sounds like a smaller throttle body or a different pulley that will allow more range is the real solution.

 

I think learning to drive the car properly at higher boost levels is critical (no offense intended, honestly). I have a 90mm t/b on my RB25det and have no problem with it daily and a boost controller set to the mid 20s.

[Zmanco]

Sounds like a smaller throttle body or a different pulley that will allow more range is the real solution.

I've been thinking about changing to an eccentric pulley too. Any suggestions for one that can swap onto the 240SX TB?

 

I think learning to drive the car properly at higher boost levels is critical (no offense intended, honestly). I have a 90mm t/b on my RB25det and have no problem with it daily and a boost controller set to the mid 20s.

No offense taken - I've definitely modified how I use the throttle and shift points when driving sedately to compensate. But nonetheless it's hard to precisely modulate the throttle and boost when cornering, especially coming out of a corner in 2nd gear. I have a 4.11 diff so the boost comes on at slower speeds for me than most others. I know that to some degree this is a fact of life with a turbo motor, but if the throttle was less sensitive at small throttle openings, it would no doubt be easier to control. My daily driver is a turbo volvo and the boost comes on in a more linear fashion so that I don't have this issue to the same degree (although in fairness, it doesn't make as much torque in the mid range either).

 

FYI, to my original question, I forgot that the rod on my actuator is bent just as it comes out of the housing, so this approach isn't going to work for me.