WG Vacuum Source. Turbo or BOV Line?

[Slow95gsx]

What do you prefer. T off of the BOV line, or if avaliable off of the side of the turbo?

 

[BlackbirdOfPrey]

The side of the turbo is actual pressure, T-ing off the BOV line is adjusted pressure (after cooling, going through intercoolers, etc...). The prior is more accurate to what stresses your turbo is going under.

 

[90AWDTalon]

I voted other. I run mine off the intake manifold.

 

[andymoraitis]

I voted "other" as well. I run mine off the j-pipe. It's incredibly fast reacting that way.

 

[project_tsi]

I run mine off the compressor housing on the turbo.

Andy, the J pipe location is essentialy the same place as running it off the compressor housing b/c both show actual boost pressure, not adjusted pressure, and yes, I feel that it is more accurate there.

 

[dsm-onster]

Running a boost reference as close to the turbo as possible reduces spike. I voted for that as I've run small 16g and 18g and spike has been a minor issue.

But with the 60-1, I have a reference from the intake mani... I think this is best for a slower spooling turbo.

Think about it. If you lift slightly when you shift, there is vacuum in the intake mani and higher pressure in the intercooler piping. If you reference any where from the intercooler piping, you've got a split second where the wastegate opens even more than when on boost during the rev before. This is probably very slight, but, nevertheless, slows spool between shifts.

However, if you reference the intake mani, you will show the wastegate vacuum between shifts. This slams the wastegate shut saving every bit of what's left of the exhaust pressure to keep spooing the turbo. Probably slight. But every bit helps. I havn't actually tested this and logged it. But I will log this on DSMLink as soon as I get a GM 3 bar map sensor to see if my theory is worth the effort.

Besides, increasing the likelyhood of spike (by referencing far away from the turbo) should also be good for a slow spooler.

 

[steve]

The side of the turbo is actual pressure, T-ing off the BOV line is adjusted pressure (after cooling, going through intercoolers, etc...). The prior is more accurate to what stresses your turbo is going under.

This is a common misconception. Since your setting the MBC based on the boost gauge readings, where the adjustment screw winds up might be different but the final result is the same.

The advantage to using the turbo compressor/j pipe is the shorter length of hose reduces the chances of spiking.

Steve

 

[BlackbirdOfPrey]

I'm not following you. If your boost guage is reading 20psi (based off of the throttle body), yet you have an intercooler with a 1psi presssure drop, how is the 21psi the turbo puts out (which turns into 20 psi after the pressure drop) the same? your only seeing 20psi, but the turbo is really putting out 21psi and taking the wear and tear from 21 psi. Maybe I'm missing something. Because of pressure drop, doesn't a turbo have to be putting out more psi at the turbo to see a set number at the throttle body?

 

[steve]

I'm not following you. Maybe I'm missing something. Because of pressure drop, doesn't a turbo have to be putting out more psi at the turbo to see a set number at the throttle body?

What's the difference? Your stilll setting the MBC based on a reading from the boost gauge not some local pressure. As long as the boost gauge reference point doesn't move, the turbo will be pushing the same amount of air and working exactly as hard no matter where you pick up the pressure reference for the MBC. The only change will be the screw setting on the MBC that nets you the same 20 psi on the boost gauge.

Steve