I'm new to forced induction so can someone explain how negative boost pressure (<-0.8 bar/vacuum) is created when your off throttle..? onder2:

Also does 1.1bar peak sound about right..?

You may have guessed, I've just fitted a boost gauge (Blitz)..!

Cheers

Jason

 

The vacuum is created as the engine normally sucks air in (how do you think normally aspirated cars work ). Only once the turbo is pushing air into the engine do you see +ve pressure.

 

what is the car/mods to see if boost is correct?!

 

I understand the mechanics of N/A induction but not forced..!

I would appreciate the plumbing of a turbo application. As far as I know the turbo runs off the exhust manifold, compresses air, which is then cooled via the intercooler and fed into the intake manifold. But how come the vacuum created by normal compression does not suck the turbo compressor into reverse..?

Also where does the air intake plumb into the induction cycle..?

Jason

 

Ahhh, check this out:

http://auto.howstuffworks.com/turbo.htm

 

Std 05 WRX 3000 miles (optimax/OB)

1.1 bar peak & -0.5 to -0.8 bar off gas

Cheers,

Jason

PS excellent web page, just what I'm after..!

 

As far as I understand boost can be measured as absolute pressure or relative to atmospheric pressure. This may explain -ve boost.

 

If your reading a boost gauge on a turbo car...bear in mind it's connected to the inlet manifold...So when you close the throttle no air can be drawn into the engine, and thus a vacuum is created. The turbo can still be whizzing away under high pressure (Eg immediately after snapping shut the thottle whilst on full boost), but because of the closed throttle you'll read a vacuum on the guage.

 

Hi Jasonius.
What gauge have you fitted? Did it require some connections to the engine bay (to the manifold)? If so how did you do it neatly and where have you mounted it?
sorry for all the questions but I am looking to buy a boost gauge or a turbo timer.
Dan

 

Hi Dan,

I ended up getting a Blitz R115 (52mm mechanical- £78 scoobyworld) as it matched the dash best ie chrome bezel, white on black, red needle and greenish light-up. (I've partly coloured the bulbs green so it's now a perfect match on light-up..!). Very impressed with build quaility.

As for fitting it's a piece of cake (you do have to connect a pressure hose using a 't' piece (supplied) but it's really easy..!

You have to remove lower panel under sterring wheel (two screws, again easy, to fish wiring through)

I used a AVO corner pod which looks really good. (powerstation £38)

Andy (mightyvid) has a .pdf file which shows exactly where to 'plumb' in to a WRX 04/05, I'm sure he wouldn't mind me sending it to you if you like..?

If you want the info pm me.

Jason