So I had about a month of downtime while getting my clutch replaced. When I got back on the road I did a highway pull and noticed it went to 30psi. A normal highway pull will do 29psi peak then taper down to about 26psi. I have a hallman bc by the way. Only different thing I notice is that today the weather outside is at 65 degrees, the coldest of run my evo 8 in. Should I be worried?

 

Boost creep...also the colder air will cause for a more efficient system and increasing boost pressure.
Solution; lower MBC, or run ECU controlled boost

 

+1 colder air=denser air.

 

Where should I start? Should I lower it a quarter turn?

 

Lower it until it peaks at the same psi it was tuned to. I adjust mine an eight of a turn or so with changes in temp.

 

MBC's don't compensate for change in air temp. Just lower the setting on your MBC.

 

Mount it close to your radiator and the boost swing will lessen. Also, if there is no knock, take advantage of the increased boost.

My Hallman swings from 30-32 psi between cold and warm weather, and has been doing that for years now. No problems.

 

I would play it safe than sorry ...if you're not tuned for the increased boost I'd steer clear

 

You could just turn down the boost controller in 1/4 or 1/2 turns until boost lowers to where it was previously or, as long as there is no knock, you can run with the extra boost.

As others have said, the colder air is more dense than warm air, which causes the boost increase.

 

Will do thanks guys

 

Back the knob out 1/2 turn and then retest at WOT in 3rd or 4th gear, at same ambient air temps. I don't think that a half turn alone will get the peak level back down to the same level that it had been at before. So, be prepared to back the knob out an additional 1/4 turn at a time after the initial 1/2 turn until you achieve the same boost level as before.

 

Oh Wow I didn't know when the air is colder it changes how much boost you run. Just learned something new. Now i need to lower mine too because its getting colder over here in Canada

 

Kanada is Khuuuul!

 

Colder air packs more oxygen molecules in a given volume of space. Denser cooler air = more boost pressure

 

I thought maybe it will go up 1 or 2 psi max but 4 psi!?!? Scary,