Hey All,
I have an "engineering" question about the installation of the Blitz SBC-iD boost controller. The installation manual indicates (twice) that the "in" port for the controller's solenoid should tap into the intake BEFORE the throttle body. I currently have mine fed by a T in the vacuum line coming off the plenum. This line also feeds my boost gauge.

So can anyone tell me why this line is supposed to be pre-throttle-body? Am I placing anything at risk by having the plumbing like I have it? Thanks for any responses.

 

I am pretty sure thats where mine is hooked up. I can check when I get home for you. I believe it just needs manifold pressure. I cant quite remember right now though.

 

if anyone with this installed could shed some light on all the connections that would be great. If I read the manual right you should have the following connections for an external wastegate:

Signal line from turbo to lower wastegate port
Signal line from plenum to control unit
Signal line from out port on solenoid to upper wastegate port
Signal line from intake pipe pre-throttle body to in port on solenoid

 

I just talked to a friend at a shop here in the area, and he recommended we tap into the piping between the compressor and the throttlebody. This could be anywhere, even in the intercooler piping, so we have quite a few options as far as placement goes. I wouldn't be comfortable running it off a T from the plenum, if that is not recommended by Blitz.

My SBC is going in next Wednesday, so I'll post some pics of what we came up with then.

 

I wonder what that line does exactly? The other one goes from manifild to control unit so I assume that is read and the controller outputs a signal to the solenoid.

 

According to Blitz that is the line that sources pressure to keep the wastegate closed to increase boost. For this reason he said it needs to be there to ensure that even if the manifold is under vacuum and boost is being built that there is pressure there to keep the wastegate closed.

 

that's what I'm wondering. Since the control unit has a manifold pressure signal and it controls the solenoid, what does the "in" port do on the solenoid? Doesn't make a lot of sense to me and I'm wondering if what the difference is between a pre-throttle body signal and a manifold signal....

 

So it's that line that gives the boost controller the ability to increase the low/mid-range boost by holding the gate closed until the desired pressure is achieved and then allowing the gate to "snap" open?

 

EXACTLY. That line is the source of the pressure used in the OUT port to hold the wastegate closed. Thats one reason why they want it to read pressure even if the throttle body is still in vacuum or even pressure.

 

But once you open the throttle plate, the pressure in the pipe and the pressure in the manifold should be roughly equal, so vacuum in the manifold (while the turbo is still working towards 0 or positive pressure) will equal vacuum in the pipe, won't it?

 

IT should be but who knows. It may see pressure sooner. Like I said I didnt't design it. I'm just going on what Blitz told me

 

I'm with ya....I'm just gonna go out there and throw a sandwich at it and see if that works.

 

ROFLMFAO!!! It might!!

 

You guys are all on the right track. The differences in pressure between manifold pressure, pre-throttle body pressure, and turbo outlet pressure are all going to be nearly equal at all times. In really nasty big turbo situations, I could see a scenario where the turbo outlet location or pre-TB location would be better. I say flip a coin.

For what its worth, I also have used manifold tabs, without any boost issues.

 

Hey Sharif,
I know we spoke about this briefly. So it's your opinion that tapping into the pre-TB piping is NOT necessary in this application? The only time I can see that the two spots would be different is when the Throttle plate first closes. The manifold is going to go instantly to vacuum, but the charge pipe is going to still be pressurized while the BOV is venting the compressor surge. That shouldn't make any difference though, right?

 

At that point no not really as the BOV will open to release the pressure anyways at that point. Like I said I'm not trying to argue that the manifold locations absolutely wont work. It very well might. I'm just going off what Blitz says in the instructions and on the phone. If the manfiold doesn't end up working thats fine then switch to the intake pipe later

 

That's correct. In practice, there will be no meaningful difference between the two, and so I trying to understand why Blitz is the only boost controller i have seen where they specifical say pre-throttle body.