About Turbo

[jonny-rockets]

I have a question about boost gauges and turbos in general.

Where does the boost gauge take its reading from? Is it before the air is distributed across all 4 cylinders, or is that the pressure from within the actual cylinders?:dunno:


For example, I believe a stock wrx turbo's max is around 15-17 psi. Does this mean that each cylinder gets approx 3.75-4.25 psi boost?

Thanks,

Anthony

[method]

It is measuring it off the intake manifold. I think your thinking of flow by splitting it up like that. Pressure won't divide per cylinder. The pressure will be about the same everywhere inside the intake manifold minus any pressure drops due to friction. So if your reading 15psi, it is 15psi going into each cylinder - minimal pressure drops.

[Nate8409]

Yup just as Method said.

The ecu gets it reading from a sensor in the intake manifold and like most of us with a boost gauge we get the reading off a nipple coming off the intake manifold that provides presure to the bypass valve or blow off valve.

So under boost you are holding the blow off valve shut and under vacuum (between shifts) you are opening it with the engine vacuum.

With that said you might think that every time you let off the gas it would open this valve and divert the pressure back. It doesn't though because the valve has a spring in it that holds it shut until a certain vacuum can be created by the engine which can only happens under a certain amount of boost prior to you lifting off the gas.

[jonny-rockets]

Thanks,

So, people with loud blow off valves, do they have modded equipment that opens that valve every time they let up on the gas? Or does this valve still only open under hard driving circumstances, and their louder sound is just from a bigger blow off valve kit?

[method]

They are probably running a "vent to atmosphere" type BOV. These vent the air out of the valve with a 'woosh' or whistle sound instead of the stock recirculating or hybrid valves. Recirculating and hybrid valves are are your best bet for the WRX.

[Nate8409]

There for the most part is no upgrade for the stock WRX/STI bypass valve.

Most parts are downgrades and a waste of money. They are noisemakes. Unless you are running some insane volume of boost and even then not really.

Kind of like intakes. They are just noisemakers.

The stock valve and configuration is almost always best.

[jonny-rockets]

cool great to know! thanks for the info guys.

Anthony

[Kevin]

also on blow off valves you can't make them work any better with a tune. The only way they will work well on a subaru is with a blow through maf or a aftermarket ecu that doesn't use a maf.
I've had a few and they make your car run like shyte. I've had my stocker up to 22 psi and worked fine.

[Nick S.]

I have a blow through set up on my car and it is handling 38 lbs/min of airflow fine.

On your blow through set up did you just relocate the stock MAS or were you using an after market set up?

The only problems that I've run into with mine is that the calibration is way off. Which I have adjusted in DSMLink.

From what I have seen on Enginuity on Kevin J.'s car it doesn't look that complicated to recalibrate a stock MAS or an aftermarket one in a blow through set up. As long as you have enginuity and a wideband that you can log you just use the wideband data to recalibrate the MAS.

The only advantage to having a blow through set up is that if you blow an intercooler pipe off you can still drive the car.

I would not recommend venting a stock BOV set up at all just like the other guys said your ECU will have inaccurate airflow counts causing bad idle and running rich between shifts.

[jonny-rockets]

yo,

i am looking for a good place to put in a T-valve to hookup the sending unit for my boost gauge.

i can see a couple of places where it looks like it will fit. is there a specific line I need to tap into?

eh pic kinda fails at showing the one i wanted to...

http://i284.photobucket.com/albums/ll21/unhiol/DSCF0206.jpg

[wagonmafia]

hey, just put the t into the vacuum line by the stock bpv. if you want ill pop around and show you . but here is a pic if you look at my stock i/c at the bov you will see where i ghetto fitted my old boostgauge line.
http://i4.photobucket.com/albums/y116/67GTOchick/DSCN2454-1.jpg

[kgj996]

The stock BPV line is the easiest place imo because it is close to the driverside fire wall, for routing the line into the cabin. And it is very acessible.

[jonny-rockets]

anyone have a close-up pic of that area, or line exactly?

i don't know where that is still :(

wagonmafia if your free at some point tomorrow afternoon shoot me a PM. i think i am up for a round of golf in the AM, and then i need to swing by work for about an hour,

but after that if you want to just swing by and show me where it is that would be sweet!

its an electrical gauge, so i have a sender unit i need to mount, and i can just route the cable through the clutch, there was a good post on scoobymods about this...

[wagonmafia]

thats the same as mine then so you can just copy it.

[jonny-rockets]

so i am looking for a line that goes back into the intercooler... right?

[jonny-rockets]

and wagon wait a sec,

you mention in your first post there, next to your stock IC.

i only see an STi IC there...

confused.. or are you referring to the TMIC as stock IC before you had the FMIC dropped in?

[kgj996]

No, the one that goes to your BPV. The BPV is attached to your intercooler. You just need to cut the line and put a T fitting in it and run your boost gauge line from the T. Easy as pie!

[wagonmafia]

As Kevin says. Cut the small vacuum line in the bpv and put the t in there.

[kgj996]

This is the same on all TMICs. Hope it helps.
http://i245.photobucket.com/albums/gg45/kgj996/BPVLine.jpg

[jonny-rockets]

aha excellent pic!

i will see if i can get this all done tomorrow!

[wagonmafia]

**** thats a hot wrx, must be super fast...

thanks Kevin, i was just doing that.

[kgj996]

**** thats a hot wrx, must be super fast...

thanks Kevin, i was just doing that.
It has to be an 11 second car by the look of the sweet decals!:lol:

[Kevin]

**** thats a hot wrx, must be super fast...

thanks Kevin, i was just doing that.


naa I heard it was an auto:rofl:


j/k

[Nick S.]

It has to be an 11 second car by the look of the sweet decals!:lol:

:D

[jonny-rockets]

you guys use the stock vacuum lines? i have heard that some people replace them with some nicer lines, and get the little clamps.


these lines are a ***** to connect...

[Kevin]

on my daddy's electronic boost gauge the tee gets cut in the hose going to the bypass valve. then the gauge should come with hose to go the gauge.

[jonny-rockets]

yeah that's the plan where im putting it in all right.

i have some of the plastic vacuum tubing they supplied with the gauge, and i need to hookup the sending unit to the mini air filter, then to the T.

that's the tubing i am talking about

[Kevin]

mini air filter?

[jonny-rockets]

yeah i hadn't seen that part with my last gauge... it must be a new thing..

its this little glass mid piece with a foam filter in the middle. i'll take a pic in a minute..

[jonny-rockets]

you'd think this would throw off the readings... no? at least make the response a bit more sluggish...

hmmph

http://i284.photobucket.com/albums/ll21/unhiol/DSCF0215.jpg

[Kevin]

hmm what brand gauge prosport?

my guess is maybe something to keep oil out of the sensor.

[jonny-rockets]

ya its prosport

[wagonmafia]

thats probably just to save the sender unit from some moisture, me personally wouldnt even bother with that. just 2 more connections for a leak.

the wagon is a auto tronic. way better than tiptronic.lol