Uncontrollable boost.

[MC_Bob]

Bit of an odd one. Since trying to sort closed loop boost control, I've run into a new issue which I believe is with my turbosmart gen 4.

 

I have a Mac 3 port plumbed to top and bottom. This has worked well for this season. 

 

Now, no duty cycle and I'll make 8psi throughout the whole range. As little as 15 percent duty and it'll make 15psi. A couple percent makes a massive difference.

 

I believe what's happening. Maybe. Is that when the stage 1 is active. It's pressurising the top of the wastegate. This is then sealed shut and doesn't bleed off it's air due to it being plumbed in to the Mac valve port.

 

My question is.. should the wastegate actually bleed off some of it's pressure over a second or so? You can apply pressure to it on a test bench and it holds it's air. 

I believe this is why I'm having boost issues. 

Is this true or am I barking up the wrong tree.

Clutch at straws a bit  .

 

I've tested the Mac valve, and the ports/diaphragm on the valve work ok on a bench.

[atlex]

If by wastegate you mean the wastegate actuator, I'm fairly sure it shouldn't bleed anything at all - it should be open as long as there is pressure and it shouldn't leak down. You can test it with a tyre pressure pump. You don't need to remove it to test it.

8PSI sounds good for the range for a standard type actuator.

 

[Adamw]

If boost controls ok in open loop mode but not in closed loop then it would suggest an issue in your settings.  Attach a copy of your tune and a log.

[dx4picco]

what is the max boost you are trying to acheive? 

4 port may help a bit when plumbed that way, but yes still sensitive.

if your max target boost isn't too high, only plumb it to the bottom port it will tame things down alot

[koracing]

Having the wrong frequency on the solenoid can also change the response range of the solenoid into a very non-linear response.  You should bench test or "ear" test the solenoid with different frequencies and should hear clear clicking with a good frequency from 10 or 15% duty up to 80-90% duty.  Also there are a *ton* of knock off mac solenoids that have terrible response and are super sensitive, so where you get the solenoid from makes a big difference in how it responds as well.

[MC_Bob]

Hi guys.

 

Thanks for all your replies.

 

It's sorted now. I must have always had a small leak o. The diaphragm. But since last doing a bolt check and refitting the top of the gate there is now no leak, and the way I had it plumbed, air pressure would stay trapped in the top of the gate.

I've since redone the plumbing to a more conventional style and it's working well,