NoSeeUm

Not sure what you are asking. First my truck is a 5 speed, so we are talking apples to apples just different kinds of apples.

Initially I went with assuming like you are running, by relaxing (lengthening) the actuator connecting rod and lowering the waste gate opening pressure on my secondary. I was trying to minimize drive pressure and I had the problems you describe. I was trying to spool the s400 sooner, but it would not spool well nor quickly enough no matter what I tried. My problem was not spool up so much as trouble pushing EGT's down. I had to get in it hard and stay there. Not great for towing and tons of smoke off idle.

To improve my performance I went the other way, like Hohn describes. I had to raise the waste gate opening pressure and shorten the connecting rod on the secondary. Now my secondary spools much faster and sooner. This gives me much better low rpm boost and still provides very good EGT relief towing. In fact, I have almost zero EGT concerns 95% of the time any time. Ussually almost no smoke, more of a gray haze if I "sort of" get in it.

At maximum power, this set-up might cause some exhaust choking and I would likely relax the waste gate on the primary a bit if I get on a dyno again. But overall for street and towing it works for me much better.

I am going to guess my secondary waste gate comes open fully around 30 psi boost, but is delayed due to the boost elbow. If I stay in the throttle and boost gets up around 50-55 psi I have seen close to 50/50 primary/secondary contribution for a few seconds. Initially, I remember seeing 10 psi primary 35 psi boost during spool up. The whole process is difficult to watch and drive. My set-up is probably not optimum, but it works.

For me it was a total over the whole learning process and I am far from expert.

Jim

Mike Holmen

Sorry for the dumb question here but how did you adjust the wastegate opening pressure? Adjusting the wastegate activator only adjust if you pull on the activator rod very hard this will push the opening pressure higher, but you have only so much travel. I had to take the turbo off to see if the wastegate was fully closed and how much it opened at what pressure. I would rather have a more fine control with what pressure and how much it opens at for a certain pressure. I have a hard time see how the wastegate effect intial spool-up unless you can pull 20+boost instantiously. The only thing I can see if you where running the wastegate open slightly all the time then I can see it would be slower to spool. You have to get the wastegate fully closed, for an intial pressure setting. I've ran two different pressures on my PDR HX-40, one at 40+psi and 22 psi. Guess which made more HP and lowest egt's? The lower pressure on the wastegate, the 3B would light harder and push the torque up. I have even tried running just on my primary turbo and running my HX-40 in fully wastegate fully open just see how it would work. Its nasty, very nasty slow slug. My current HX-40 is set to start openning at 22 psi and to be fully by 28 psi. My prior 40 was set to start at 40psi and was partially open at 50psi.

Big Blue24

Mike, don't forget about drive pressure making it open sooner than your shop air test. My gate starts to flutter at 26 psi boost even though the actuator is completely closed off with a brass plug.

Or in other words, my drive pressure blows the gate open at 26 psi and continues to float as boost peaks around 38.

NoSeeUm

Not a dumb question.

Initially I cut slots in waste gate actuator so I could loosen the bolts and slide the actuator off the bracket easily. This way I could increase or decrease the tension on the waste gate by lengthening or shortening the connecting rod. This bascially sets the preload that resists blow open creep that is cause directly by drive pressure. Mine is set pretty tight, I assume it takes 20-25 psi of drive pressure or so for it to begin creeping open. End result is faster spoolup, but less bypass into the hot pipe initially.

I use a simple boost elbow to set the waste gate opening pressure. I set this only using trial and error. The adjusting screw is also set pretty tight though. Probably less than one turn open.

Basically, I have tried to set it up so that it is fairly hard for the waste gate to open vice it being fairly easy for the waste gate to open. This way I rely mostly on boost from the secondary while using the primary simply to significantly enhance overall performance. Like I said this likely hurts my maximim Hp, but provides a really good compromise for the street and towing.

What size housing on your HX40? I am running a 14cm WG.

Jim

Mike Holmen

What size of wastegate actuator you using? There are different style and spring sizes. I've thought that might happen. Just thinking outloud have you considered that Turbotechnic has a double inlet/outlet actuvator that you could pressure up the inlet side to add some extra holding power. Its something to keep in mind. I'm just brain storming idea on my twins. I've been working on my down pipe and I've been thinking too much to getting anywork done.

NoSeeUm

LOL

Don't we all. Them BB turbos are spendy, well worth some brain $$$ before pocket $$$.

I am running stock actuator and an un-modified waste gate.

Jim