Subaru WRX Forum banner

boost gauge reading?

5K views 36 replies 6 participants last post by  Rambo 
#1 ·
Finally my back ordered SPT boost gauge has arrived and its being installed today. Other than the SPT cat back that has been installed, I'm stock and on stock maps (for now). What should my gauge read as "normal". I've never had a boost gauge and never had experience with them before.

What shod it be at idle?

At WOT?

And during normal driving?

Thanks!
 
#2 ·
What shod it be at idle?
- In vacuum. This depends on the gauge. I believe mine reads positive pressure in psi, and negative in inHg. I believe it sits around -20. Regardless, should be under zero.

At WOT?
- Whatever your target boost is. This will depend on RPM & Load, and more so your specific car. Stock 08+ I'd expect 14-16psi. I'd be concerned that you have a leak if its under 14 psi at peak torque (3-4k RPM WOT)

And during normal driving?
- Somewhere between idle and zero normally. It tends to "center weight" at zero on my gauge due to the change in labels (psi from inHG)
Thanks!
=)
 
#6 ·
It's probably not psi, FWIW. I think idle is around -10psi if you are speaking in relative terms.
 
#5 ·
At idle and normal cruising, you'll be reading vacuum (I usually read about -10-15mmHg, but YMMV). At full throttle in 3rd gear, Cobb Tuning reported peak boost of 15psi on the stock tune, and it quickly tapers off after that. See the Boost and Air/Fuel Ratio Graph in their map notes here [PDF]: https://static.cobbtuning.com/cobbtuningweb/site/maps/subaru/map_notes/SUBA_US_WRX_09-13.pdf

So you could expect to see a quick spike around 15psi when you hammer down, then the boost will drop off after that.
 
#8 · (Edited)
It shows proper psi at WOT 14ish but every other moment idle or driving normal is 2 inHg.

Anyone have a clue as to why it has started reading this way?! 3rd and 5th gear the turbo psi registers up to14psi and lliterally every other time other than a slight move of the needle, its at 2 inHg
 
#9 ·
rurso01 said:
It shows proper psi at WOT 14ish but every other moment idle or driving normal is 2 inHg.

Anyone have a clue as to why it has started reading this way?! 3rd and 5th gear the turbo psi registers up to14psi and lliterally every other time other than a slight move of the needle, its at 2 inHg
Could be a vacuum leak. What is AF Correction @ idle?
 
#10 ·
Would I need an AP to know that? I'm not sure how to obtain that info. I did listen under the hood asmy girlfriend lightly hit the gas and no leaks that I could hear. It was working fine the first 2 days and already on the 3rd day its acting up...
 
#11 ·
rurso01 said:
Would I need an AP to know that? I'm not sure how to obtain that info. I did listen under the hood asmy girlfriend lightly hit the gas and no leaks that I could hear. It was working fine the first 2 days and already on the 3rd day its acting up...
D'oh! For some reason I thought your car was StageI (too many open windows confused me). You would need some form of datalogging. Where about do you live?
 
#12 ·
Maryland, Washington County to be exact. Any where near you? Other than a leak, could it be anything else? I guess it might be worthy to take it back to Subaru since they installed it for me. Everytime I take a car into a dealership I always leave with scratches on the interior or paint so I dread taking it back again.
 
#13 ·
rurso01 said:
Maryland, Washington County to be exact. Any where near you? Other than a leak, could it be anything else? I guess it might be worthy to take it back to Subaru since they installed it for me. Everytime I take a car into a dealership I always leave with scratches on the interior or paint so I dread taking it back again.
That's near Baltimore/DC, right?
 
#18 ·
rurso01 said:
Is there anything bad that can happen if there is indeed a leak? I don't want to drive the car until its resolved if it could be detrimental
A vacuum leak will cause the car to run lean at idle
 
#21 ·
Running lean can increase knock as well as temperatures where you don't want increases. This can lead to a blown engine.
 
#22 ·
I was doing some research on others who have a boost gauge operating correctly with PSI but idle is at 0 and some people mentioned the hose could be pinched? Could this be a possibility? I get that the vacuum could be leaking and while that is the worst case scenario, is it the most likely considering it has been driven 3 times since its install from the dealership?

Also EJ257, are you from the area?! I saw you mentioned Gaithersburg.
 
#23 ·
Sorry one more question.. how should I approach talking to the dealer about this? Not normally put into this type of situation. I am thinking of taking it up with the service manager since the tech who worked on it was quite douchey and sorta rude to me during the 15 second convo I had with him about placement of the gauge.
 
#24 ·
rurso01 said:
I was doing some research on others who have a boost gauge operating correctly with PSI but idle is at 0 and some people mentioned the hose could be pinched? Could this be a possibility? I get that the vacuum could be leaking and while that is the worst case scenario, is it the most likely considering it has been driven 3 times since its install from the dealership?
Didn't realize it was so recently installed.

rurso01 said:
Also EJ257, are you from the area?! I saw you mentioned Gaithersburg.
No

rurso01 said:
Sorry one more question.. how should I approach talking to the dealer about this? Not normally put into this type of situation. I am thinking of taking it up with the service manager since the tech who worked on it was quite douchey and sorta rude to me during the 15 second convo I had with him about placement of the gauge.
Just explain the symptoms you're having. Don't guess the problem.
 
#26 ·
rurso01 said:
Does it being so recently installed make you second guess the whole vacuum leak idea?
I'm not sure. But you're noticing a problem with a recent install. Call yesterday to explain there may be a possible issue with services rendered (depending on how long it's been, you could get fixed free).
 
#27 ·
It was installed on Thursday so its definitely related to the install. I am going to take a picture and upload it in a few minutes. I don't know if they t'd it in the best place. They sliced the mesh material hose. When I have looked at other install pics, people have used a different hose to install on. Uploading shortly...
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top