POLL: where do you get your wastegate actuator signal from?

[Guest bastaad525]

I keep going back and forth, from getting my signal to my wastegate actuator (and boost controller) from the stock locationg (to feeds off of the compressor housing) and the intake manifold.

 

I seem to notice little differences running each, each seems to have a little advantage and disadvantage... so I was just wondering, how all you guys run yours, and what experiences you've had each way, and why you run it how you do.

 

For me, I notice that, when hooked up the stock way, I get way less spiking (1psi), the turbo seems more responsive, and oddly, I see to get way more punch when the turbo comes on (breaking the tires loose in first in second is pretty consistent when hooked up this way)

 

When hooked up from the manifold, there's way more spike (2-3psi), but boost holds much more stable up to redline, whereas it tapers off slowly as revs increase when hooked up stock.

 

I can't decide which way to leave it!!

[Cody 82 ZXT]

I have mine at the turbo. Seems the most accurate to me.

[Clifton]

I took my signal off the turbo. The higher you set a MBC above the wastegate setting the more spike you'll have. If you are running an internal wastegate you can add a spring that attaches to the flapper that will hold the wastegate shut longer. I used a peice of threaded rod to make it adjustable. It was dead accurate even at 17 psi were the MBC would sometimes spike to 20 psi if I romped on it at higher rpms:( . It was a little better at lower boost though.

[Scottie-GNZ]

I agree that the compressor will be more accurate. OTOH, not sure if it makes that big a difference as you will set the adjustment not based on the reading at the compressor but what you see on the boost gauge which should come from the after the TB.

[Guest bastaad525]

Oh... you guys might all want to mention what kind of boost controller you're running as well.

 

 

I'm running the DIY grainger ball valve type. Spiking for me was never too bad, from 10 psi up to 14psi that I'm running now.

 

One possible advantage of running it from the manifold, with this kind of boost controller anyways, is that, between shifts, the vacuum signal in the manifold surely must close the ball valve pretty quickly and keep it shut tight, closing the wastegate almost instantly and allowing the turbo to keep spooling that much more... I dont really know how this works when getting signal from the compressor but I don't imagine there ever really being a lot of vacuum signal there (correct me please if I have this wrong) to snap the wastegate shut like that. If there is any difference there though, in practice, I don't notice it.

 

I also assume that the turbo spools up a tad more slowly when getting signal from the compressor housing, since the wastegate is going open when full boost is reached in the compressor housing, but before full boost is reached in the manifold... causing less spike and ultimately less 'push' to get the boost into the manifold faster. Again... please correct me if I have this wrong... and again, if there is a difference in practice, I dont notice it.

 

 

so far all hands for running it off the compressor so far(I had actually reverted to running it this way a few days ago). I still just don't know what to make of the boost falling off as revs increase, when hooked up in this manner. It never did this before installing my intercooler, and doesn't do this when getting signal from the manifold. Which... when considered in with the point that Scottie made, is what had me switching over to the intake manifold to begin with... ahhh but that spike!!!

[Doug71zt]

Sounds like there is too much pressure drop across the IC as the airflow increases at higher RPM. To maintain the boost pressure to the intake (compensate for the pressure loss in the IC) take your WG signal from after the IC but before the throttle body.(in the intake piping). This is probably the best compromise you can make. I take mine close to the turbo output, it is the most accurate.

 

Doug

[Guest bastaad525]

Sounds like there is too much pressure drop across the IC as the airflow increases at higher RPM. To maintain the boost pressure to the intake (compensate for the pressure loss in the IC) take your WG signal from after the IC but before the throttle body.(in the intake piping). This is probably the best compromise you can make. I take mine close to the turbo output' date=' it is the most accurate.

 

Doug[/quote']

 

 

This thought had just occured to me, literally as I was falling asleep today. I figured I was losing about 2psi across the I/C at all times. But then I noticed... when I last had the signal coming from the intake, I had the MBC set to 14psi. When I then put the signal back to the compressor housing, boost would still hit 14psi and then slowly taper off to 12. I was expecting/had thought I had seen before that it would go to 12 and then drop to 10... which had me a bit confused. So it makes sense that at first full pressure is getting thru and then as you said, pressure drop increases as revs go up. Finally that mystery solved! At least, as to the WHAT, Though I'm still a bit confused as to WHY it behaves that way. I wonder why I'm getting so much drop... 2psi is too much isn't it? It's a good I/C (Trust/Greddy) is a good size, and I'm running 2 1/4" pipe all the way. Thinking I ought to just leave it this way then, with the turbo spinning a more or less constant speed/boost level... rather than having the turbo keep spinning faster and faster to maintain same boost level in the manifold. Keep it running cooler and safer.

 

 

Sux because it has started to rain here in CA so... no more 'test and tune' for me I guess