2004 to 2020 Mazda 3 Forum and Mazdaspeed 3 Forums banner

1 - 14 of 14 Posts

·
zoom~
Joined
·
848 Posts
Discussion Starter #1
I am kinda confused. I know boost gauges start from 29 ish inHg and goes to PSI.

So when at WOT, 29.8inHG means vaccum? or pressure? And since its always .5 lower then Baro, I am not sure anymore.

Can anyone explain the difference?


The reason I am asking is because ever since the ram air duct is built, I've been getting less (27~28) vs the original 29 ish, so I am trying to figure out whether its helping or being counter productive.

thx
 

·
zoom~
Joined
·
848 Posts
Discussion Starter #3 (Edited)
Doesnt matter of the unit, is it pressure or vaccum?

InHg is inches mercury, its one of the standardized unit. Every two inHg is 1 psi roughly.

The scanner i got say inhg so...i am stuck with that.
 

·
Registered
Joined
·
3,274 Posts
well just convert it to Kilopascals. Map sensors read in Kilopascals, although, Dynotronics said the map sensor is for closed loop emissions control only,

29.92 in HG is sea level atmospheric pressure, so your reading right around atmospheric pressure
 

·
zoom~
Joined
·
848 Posts
Discussion Starter #6 (Edited)
well just convert it to Kilopascals. Map sensors read in Kilopascals, although, Dynotronics said the map sensor is for closed loop emissions control only,

29.92 in HG is sea level atmospheric pressure, so your reading right around atmospheric pressure
Yeh, thats the baro around here, but i cant understand why its lower now with the intake litterally raming the air in the front...

Its should get tiny static pressure accumilating somewhere....not to lose it lol.
 

·
Registered
Joined
·
3,274 Posts
Yeh, thats the baro around here, but i cant understand why its lower now with the intake litterally raming the air in the front...

Its should get tiny static pressure accumilating somewhere....not to lose it lol.
temperature alone could affect the readings drastically
 

·
Registered
Joined
·
3,274 Posts
MAP, Manifold absolute pressure, directly affected by engine load.

I only know Map in the Kpa, and a map is reading Kpa of vac/atmospheric pressure inside your manifold, under low load high vac, the Kpa is Low, during wot/low vac, the Kpa rises, and will keep rising to a point of Atmospheric pressure, ( 0 vacuum )
@ -20inHG vacuum, the map is reading a kpa of probably 20-25.. @ -10 it probably reads 50-60, and @ 0 it reads Atmospheric pressure in Kpa..
and they also read Above atmospheric pressures aka boost, in kpa..

that's all I really know on how a MAP works
 

·
Registered
Joined
·
3,274 Posts
if your trying to create Above atmospheric pressure using ram air, your not going to be able too, from what I have read, with a Good ram air setup, you might see 0.03lb of above atmospheric pressure, @ 150mph. and almost 1psi @ 200mph.

Post a pic of how your ram air is setup, you might be choking it instead of helping it.

think about it with ram air, you literally need to be going fast enough that the force of the air traveling into the ram air intake is more force then 14.7PSI, which is something you just can't get in a 3
 

·
zoom~
Joined
·
848 Posts
Discussion Starter #13 (Edited)
oh no definitely not choking it.

The stock airdam is, however. I took a ...knife and some tape to it. So air goes directly to the filter.

Not "boost" I am thinking, but the "less" difference or whatever the drop in MAP reading meant, is what I am trying to figure out.

Well maybe I am, 1 inHg increase is better than nothing. That's not to say above 0, but more in reference of what the manifold used to have @ WOT.

I wouldnt dream of "psi" with just a ram air, that's FI territory, its like...how much pressure can I recover from a ram air? something to that effect...

Pic wont be posted until its...pretty enough to avoid censorship. :D
 

·
Registered
Joined
·
3,274 Posts
don't worry dude, let them flame away, whatever works for you it's cool. pic! hmm well it could of been just from enviromental changes, I'm sure your not choking it, you'll probably get some gains from it when you get all the kinks out. where is the duct for the actual air coming from? where the stock plastic thing above the radiator for the stock intake is? or down low near the wheel well?

oh is that subaru maf housing that i showed you working well? just curious cuz mine gives a cel.. but probably due to all my other junk attached to the engine lol
 
1 - 14 of 14 Posts
Top