I installed Blitz DTT boost gauge back when I only have 800
miles... my car was making some peak 1.28 hkpa (bar) in the
lower gears and 1.32 in the higher gears...

My EVO only has around 2300 miles.... and only makes 1.23
in the lower and 1.28 in the higher gear....

Is this a sympton is loose intercooler pipings?? But would the
clamps loosen up over time??

 

I have the same guage (Blitz DTT) and can't always get the full 19 psi of boost. 1.17 to 1.22 in lower gears and 1.25 in 5th gear on a 70 degree day. 1.22 to 1.28 in lower gears and 1.31 in 5th gear on a 40 degree day. I always get a lot more boost on 5th gear. Is this normal for the EVO?

btw 1 hkpa is 14.7 psi according to the Blitz website but I always thought it was 14.5.

 

i dunno your readings in PSI but my peak boost is 17.5 psi in lower gear
it's around 18 psi on the 5th. i think there's some loose clamps or even leaks.

 

What are the outside temp differences in relation to the different boost readings?

I do know my car reads less boost overall during the winter months, but that's when it's real cold, like below freezing.

 

Dont you normally make a little more boost when its cold? Ive heard a lot of people are hitting fuel cut becuase its cold.

 

Yup kinda strange that some people are making less boost when it's cold, it's opposite for me.

 

I'm getting more too. It's occasionally hitting 1.59 now (23 PSI) with the boost restrictor removed. When the weather was warmer, peak was 1.49 (21.6). If you guys are peaking at less than 19 PSI, I would definitely check all the clamps. Or maybe you have a leaky BOV or something?

Anyone know the actual reason why colder air affects boost pressure?

 

I've checked all my clamps but I can hit 19psi only on a very cold day in 4th and 5th gears. Aren't you hitting fuel cut at 1.59 bar? I'm thinking of removing the restrictor since my boost is not very high. Last time I had my airbox out I tried to squeeze the restricter out of the hose but it wouldn't budge, is there an easy way to remove it?

 

The reason colder air affects boost is becuase your intake and intercooler are taking in really cold air which is denser, allowing your turbo to make more boost.

 

Cold air is denser air (takes up less space).. Denser air means more air into the system before its even compressed.. After its compressed it heats up and expands... But since there is slightly more air in there on a cold day as opposed to a warm day, hence slightly higher boost. I experienced fuel cut as the air got cooler and denser, my MBC was tuned to 21.5 (Approx) psi during the warmer weather.. For the most part the boost was spiking higher than it was when it was warmer and I had to turn it down. I decided to remove the MBC and put the stock solenoid back into action only to discover it was spiking on my car on cold days as high as 22psi (19-20 psi in most occasions)

If you have an aftermarket cat-back exhaust, it seems like you definitely need to regulate your boost better than relying on the stock solenoid.. Although it doesnt typically go higher than 21psi, part throttle spiking under load can go 21psi or higher, and you'll hit fuel cut (Stumbling sensation under load)

In cold weather, I'd recommend staying with about 19psi just to be "Safe" From spiking (depending on your fuel tuning)

 

Hmm.. so evo should make more boost on colder days??
Does that mean some part of my intercooler piping has loosen
up since when my car was only 800 miles???

The Blitz DTT was installed when here (socal) was still hot...
around 90-95 degree days and 75-80 nights... now it's more like
70-75 days and 50-55 nights...

Anyway to check the clamps easily?? Do I have to remove the
front bumper??

 

You have to remove the front bumper if you want to check every
clamp including the intercooler piping clamps. You can check
the upper clamps w/o removing the bumper. I would check all
the upper clamps first starting from the throttle body and then
work your way down. You will need to take the intake snorkel
out to get to some of them. If you want to do the whole nine
yards, removing the bumper/undertrays is not that hard but it's
time consuming. FYI I removed the bumper and tightened every
clamp but it didn't change my boost. Good Luck, tightening clamps
helps boost for some people but not everyone.

 

I think the deal with fuel cut is not that it is getting that much more cold air to make the boost too high but the ECU knows the air is cold and it is flowing x amount and seeing x amount of boost. It is more of a calculation given the inputs from all the various sensors. When you lie to the ECU about MAF flow then you are affecting the end result of these calculations and causing fuel cut because of the boost level given the inlet air temperature and the current boost level.

If that made any sense, let me know.

 

I forgot to mention also that during cold winters not only my boost is overall lower, but my fuel cut kicks in at a lower boost as well. I believe this has something to do with how the mass airflow sensor reads the air.

 

I understand that there's more oxygen going in there when it's cold, but why isn't the system able to regulate this to keep it at a max of 19.5 PSI? The ECU knows how much boost pressure there is, so howscome it can't properly adjust the wastegate to hold it at the desired pressure?