wastegate signal... run from the turbo or manifold?

[Guest bastaad525]

I've been reading up at this page:

 

http://www.atlanticz.ca/zclub/techtips/turbo/

 

that link was posted here a while ago, and there is a lot of good interesting info there, but there are some things mentioned that I either was not aware of, or that conflict with what I think I know.

 

One thing I saw mentioned was that you would get better boost response after shifting (or any time you were in boost, then closed the throttle and suddenly opened it again), if you have the wastegate signal coming from the intake manifold instead of from the turbo itself. Quote from that page:

 

"If you remove the sensing line for the turbo, and put it to the stock manifold you will notice the boost off lift-throttle works much better, as when you slam the throttle shut, the vacuum of the manifold closes the waste gate actuator much faster, and holds it closed tighter during cruise, making for good boost response."

 

Is that really the case? Would I be better off getting my wastegate signal from the manifold? I had heard of people doing it this way before, but had also read that running the signal from the intake manifold causes more of a spike when boost first hits.... right now with the manual, grainger valve boost controller I only get a 1psi spike or so before it settles back down to 10psi... not sure how much more of a spike I could safely get away with. Also, with the nature of the one way grainger valve, I would think as soon as vacuum hits the valve would close anyways so the wastegate wouldn't actually see the manifold vacuum anyways, right?

[fl327]

it might work better. I did it mainly to offset the pressure drop of the intercooler piping to bring it back to stock boost.

[Sparky]

its possible it would work better. but In my opinion its better to run it off the manifold anyway in order to get a true boost reading to the turbo. just like Fl327 mentioned, this will take care of the pressure drop you might have across your IC and its related tubing.

[Guest bastaad525]

have no I/C yet so for the time being that's not a concern... but if I would benefit by better response between shifts, then I'd do it... as long as the boost spiking wasn't too bad. I still think, with the one way Grainger ball and spring type valve, vacuum would never reach the waste gate actuator anyways.... which is the whole point, to get vacuum to the waste gate to hold it closed between shifts and keep the turbo spooling. But as soon as the boost drops that grainger valve is gonna snap shut, I think, and no vacuum will be acting on the WG actuator at all. Also... I wonder if subjecting the WG actuator to the extremes of rapidly going from 10psi of boost to 20hg's of vacuum may be rough on the actuator diaphragm... more input please

[Guest Jason84NA-T]

I run mine off the plenum instead of the compressor housing. It gave slightly more accurate boost response.

 

I ran the car at stock boost (man, it feels slow) with the ball and spring out, then I ran it with the ball and spring in, but only adjusted to stock boost or VERY slightly higher (I think it was under 7.5PSI) and boost response actually seemed faster. I don't have any real proof on this, just seat of my pants... I think if anything, the fact that the ball/spring valves block the signal to the actuator until they hit set pressure would help boost response.

The spring in the actuator does a good enough job keeping the wastegate closed.... engine vacuum assistance is probably meaningless.

[Sean73]

You would only see a minor difference in wastegate reponse with an intercooler because of the pressure drop across the intercooler. There are pros and cons of one configuration vs the other. It's covered pretty thoroughly in Maximum Boost.