The issue I'm having is that my boost keeps dropping 2 psi by the time it hits redline. Boost always comes on strong until it hits about 7k rpms and starts to slowly fall off. This is why I hit 470tq in the midrange and 696 hp up top because I hit 28 psi but dropped to 25.8 - 26 psi at the end. I would have made 700 if it weren't because of this issue. This kinda sucks because I want to keep the boost in the midrange the same up top so I'm not over boosting at the peak tq area. My current setup is

Sidewinder manifold
6262sp T3 hot side with .82 ar.
Tial 44 MVR wg with 10 psi spring.
MAC 3 port solenoid
Controlled via KPro

I'm not sure how accurate the solenoids are at high duty cycles but to hit 22 psi I'm at 66% duty cycle and to hit 28 psi I was at 95% duty cycle. Are these things even working properly at such higher dc? I wanted to run more dc up top to keep boost level but I was maxed out. When I say 22psi I mean in the mid and dropping to 20 up top and 28 psi dropping to 26. I get the same issues even at 14-16 psi.

Someone was saying that I could run the 4 port solenoid to get more out of the spring and to lower by boost controller duty cycle. Any thoughts in what might work?

 

I am not familiar with K-pro but I know that on AEM there is a compensation table to adjust for this. This is how i have mine setup and it only varies like .5 PSI from mid-range to red line and sometimes not even that much

 

On my AEM, LJ had to add a few % wastegate duty cycle in the upper revs to stop it from falling a couple psi.

 

Did you try turning the duty cycle down up top?

 

You should be able to adjust that, and get 2-3 times out of your w/g spring. With a standard boost controller, you don't normally see that, but with a solenoid you can squeeze out a good bit more from your w/g spring.

I'd check for boost leaks, thats usually where you see your boost falling, with that turbo, it should scream into the 30+psi range and hold.

 

Most likely you have too much emap and are pushing the valve open with exhaust pressure. Running a larger spring or switching to a 4 port solenoid will probably fix your issue. With the 4 port solenoid you can get way more boost with a small spring. You can lower pressure on the bottom port while raising it on the top port simultaneously to have the larger pressure differential needed to hold the valve shut.

 

How would I test the BOV? The only way I can think of is capping off one end of the charge pipe and using the other to pressurize.

 

The BOV could be a factor but I believe he is referring to the spring in your wastegate. At a certain point the pressure in the exhaust manifold is enough to overcome the spring in the wastegate even with manifold pressure assisting it. You should try a different spring or add another spring to target the lowest amount of boost you plan to run, then use the solenoid to bump you up to your peak boost.

This is part of the reason why the drag racing guys don't even use springs in the wastegate and instead use CO2 to control it.

 

Well I run 10 psi 1st and 2nd gear and it's awesome cause it hooks. If I have to I'll run a 14 psi spring to get more duty cycle out of my bc and then turn I up a couple% up top.

With this Mac solenoid, is it working properly at 95% duty cycle?

 

Please correct me if I'm wrong here but looking at the compressor map for the 6262 it seems that it falls off around 675hp or so CRANK.

It's running a bit past it's efficiency range, it COULD be simply out of steam at this point and choking due to the inability to flow more air.

As I said, I've no experience with this particular turbo but I'm finding it likely that this could be the case since he's talking about being at 700whp!

If that IS the problem then the matter is simple, the turbo can supply the PSIG until CFM grows too great to be kept up with at which point the PSIG drops, as you continue to rev further the motor is asking for more volume but the turbo is unable to supply it, so it instead just starts making excessive heat and less pressure (pressure not volume). This is completely typical of this situation.

Again, please correct me if I'm wrong here about this turbo or if my compressor map is inaccurate.

-Greg


EDIT> Disregard, I saw the "happens at 14-16psi" bit. That changes everything