Boost pressure v MAP pressure

Tuning discussion for all second generation Mazda 2.3 MZR DISI Turbo powered vehicles
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chilli6565
Posts: 5
Joined: December 11th, 2015, 6:18 am

Boost pressure v MAP pressure

Post by chilli6565 »

I have been doing some 3rd gear pulls and have noticed something unusual.
At wot, max boost pressure reads about 21psi but max MAP pressure reads about 35 psi ?
Looking at the log graph they overlay each other very closely so I assume everything is all good.
Why the different readings? :beertoast
mituc
VersaTuner guru
Posts: 1063
Joined: December 17th, 2011, 2:47 pm
Location: Iasi/Romania

Re: Boost pressure v MAP pressure

Post by mituc »

BOOST = MAP - BARO
Barometric pressure is about 14.5-14.7PSI at sea level depending on altitude, how mad the atmospheric fronts are in your area at that moment, and so on. So you may get a lot less than that, or a tad more.
So 35PSI MAP for 21PSI of Boost sounds about right, and now you see how useless is to log boost instead of MAP.
2008 Cosmic Blue Mazda 3MPS
Built engine + WMI + GTX3071, ~476WHP @31-32PSI
2008 Icy Blue Mazda CX7
Stock engine and exhaust (YES!!), JBR3" + GTX2867 gen2 + Autotech HPFP, self-tuned to 320-ish BHP
chilli6565
Posts: 5
Joined: December 11th, 2015, 6:18 am

Re: Boost pressure v MAP pressure

Post by chilli6565 »

Very interesting mituc. Thanks for the info :beertoast
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