Boost Reading

[cactus]

Ok... question time.

I have an electronic boost controller, and then boost gauge... As you do.

Now, boost controller is ProfecB II, so one line feeds to the gate, and other line feeds into intercooler piping pretty much straight after compressor housing. So, I assume it reads the boost at this point... and this is monitored by controller which opens/shuts gate when it hits max boost.

I have my boost gauge (autometer) reading off the plenum.

The situation is that I am getting a 5psi reading difference between the ProfecB setting (1.3 Bar) and the gauge (1 Bar), which is a fairly big difference.

Question is, is it a fauly boost gauge, or is the profecB getting a reading too early on, and there is a boost drop or something from the turbo all the way to the plenum?

Cheers.

[iluv2moan]

pressure drop across intercoller core?

[Lump]

yes & probably gauge inaccuracies
i believe boost signal for boost control should be from the cold side of the cooler so move it there

[Lonewolf]

combination of the two, boost drop across the piping and IC, and guage inaccuracy.

where the boost controller tap comes from doesnt really matter, as long as you are setting boost according to the gauge,

eg. your only actually running 1bar at the moment.

[Scradly]

The controller recieves its signal from the small vacuum line out the back of the controller itself and this tells the solenoid what boost to set it at.
Run the Boost control signal line from the same place as where your gauge is connected ie: plenum.
This should make them closer. There will still be a slight varation of about 1-2 psi.
If it is still reading 5 psi difference i would say its the boost gauge faulty not the boost controller

[cactus]

Awesome, cheers for the replies!

[Saf]

Matt, Always reference all boost signals and measure (gauge) from the plenum. There is only one point you ever need to measure, thats inside the plenum and whats going at the motor. First thing first, swap all your refernce lines to the plenum.

Secondly, Auto Meter gauges are very ordinary gauges that are over glorified that they are actually accurate. If you can afford it swap to good electronic gauges, Defi, GReddy (both made by same mob) , HKS or Apexi for eg. After years of tuning and working with them to always find they are out somewhat, your better of saving up and getting a good set.

Are you runnind a chin-cooler ?. The pressure drop along with the gauge in-accuracey can be giving you the reading your seeing. Only needs a 2.5psi pressure drop and the Automuter can be out that much at one bar easily.

[R3N]

you can get more boost with a new gauge*

*may or may not be true

[cactus]

OK ... let me pitch this to you, see if it makes sense.

Now, the solenoid for the boost controller has two outputs/inputs for vacume hose. One goes to my external wastegate, and the other goes to the nipple on the elbow that comes off the compressor housing (as I explained above).

Now, wiring goes to the actual boost controller unit, I assume to feed information from wastegate to unit vice versa.

There is also a vacume line that comes off the back of the unit, which I have t-pieced into the fuel reg. Do you still thinking there could be an issue, or because I have the unit t'd into the fuel reg it would be reading correctly?

- I suppose to see if there was a difference, I could disconnect the nipple from the elbow and run that line to somewhere off the plenum?

[Saf]

The fuel reg will be a line running from the plenum, and a line to go into a a good sourse.

[cactus]

so should I change the line where the solenoid gets its reading from...? Move it towards the plenum?

[Saf]

Do that and see where your at.

[RRob]

T'ing it off the fuel reg will be fine.

And you got ex. gate? Sounds like you havnt got it set up the best way...

[cactus]

Yeah I do... any guru want to come around/me come to your house and you can take a look at it?

[RRob]

Is it tuned?

Be careful playing with boost setting etc. when it been tuned to suit the way it is now.

[cactus]

Yeah its tuned, but if it does change when I move it ill be sure to get it tuned straight away. Dont really drive atm anyways, too wet.