Does outside temps change amount of boost?

[fourgsixthree33]

I just installed an aftermarket boost gauge a few days ago. Up untill today, I was hitting 15psi at 5500RPM. Today is alot warmer outside and I am only hitting about 7 or 8psi at 5500RPM. I was wondering if the outside temperatures affect the amount of boost and that's why I am only hitting 7-8psi or if I have a problem somewhere else. Thanks in advance.

 

[BoostedBeaver]

The outside temp will not affect the pressure that your turbo creates. The temp will affect the air density but that is different than pressure. May want to take a look into your waste gate adjustment and do a Boost leak test.

 

[fourgsixthree33]

Ok thanks. It just shocked me is all. Something doesn't seem right. But I have no MBC or anything so would the boost presuure ever change since I am running pretty stock yet?

 

[PieEyedPiper]

It is common to boost 1-2psi more in very cold weather.

 

[fourgsixthree33]

It wasn't that cold though. Like in the 40's when I hit 15psi and now it's in the 70's and I am boosting 6-7psi lower.

 

[PieEyedPiper]

Then it's clear we're not talking about weather variations. Do a boost leak test, as suggested.

 

[fourgsixthree33]

After I blead my brakes today, I looked over the boost gauge hose. Took the hose off and the compression fitting popped off. I put the fitting back on and made sure everything was very tight. Took the car up the road. I maxed out at 11psi.

I haven't done a boost leak test yet but i relooked at all my connections for the boost gauge hose. Everything is like it is supposed to be. Tight, etc. So now I am only lacking 3-4psi. It doesn't run any worse than it did when I was running 14-15psi. Actually, it ran pretty strong today.

 

[Bud92gsx]

I'm still thinking you have a leak sumwhere..But I have seen cars run a couple more psi when the weather is colder outside compared to when it's hot out..I have never had this happen, but a friend of mine back in the day had a ford probe turbo...Well he would always tell me his car ran more boost when it was colder outside..But cold does not effect the amount of air flowed by the turbo, like stated above..It just lowers air temps, and thus makes a little more power..

 

[gofer]

Hotter air is less dense, so fewer air molecules enter the CC on the intake stroke which results in a drop of the volumetric efficiency (VE).

You might try shimming or swapping your wastegate actuator (wga) if you can't build boost, its possible the spring in there has gone bad or its holding the flapper open. http://www.dsmtuners.com/forums/turbo-system-tech/179987-anyone-shim-there-14b-16g-20g-wastegate.html

 

[dsmpat95]

Check your boost gage line, it may be kink or pinched. If you have a mechanical boost gage, where does the line come through your firewall.

 

[yosvany]

Yes you will boost a little more

 

[jeff24680]

I Live in a climate that can be anywhere from -10 degrees F to 100 F. I have noticed fluctuations on my AEM Controller anywhere from 0-5 psi difference when wheeather changes at a constant 45% duty cycle. Yours might sound a little extreme so maybe there is something else going on.

 

[BoostedBeaver]

If you could perform a BLT and report with the results that would be outstanding. I still think that you have a leak somewhere in the system. Be sure to use soapy water and spray down all connections i.e. EGR, Throttle body, biss screw, coupler connections, BOV flange, BOV itself, injector seals, intake manifold gasket, Compressor housing and any other connections that you may have between the compressor cover and the cylinder. Please report when you do the test so that we can further discuss your issue. This could also be a wastegate problem but again it would be easier to do a Boost leak test so lets knock that out and go from there.

 

[fourgsixthree33]

My boost gauge hose is run though an "X" shaped slit that I cut into the steering column boot. Which is rubber so it wouldnt damage the hose. I will look for some kinks but I am sure the hose is ran as straight as possible.

The car pulls very well. I have been impressed the past couple of days with how well it's running. She pulls very hard. Harder than what it pulled at 15psi. When it ran at 15psi, it felt like it lacked power. Not so much that it was starving for fuel or anything. Just felt like she never got up and went.

I am always right on top of any boost leaks and highly doubt I have any. BLT's are like a weekly thing with me. Once work lets up and I get home at a half descent time, I will perform another BLT to make sure.

I also doubt the wastegate is stuck open or anything. I know what that feels like and don't suspect that to be the issue. Maybe it is possible the hose was messed up from the get go. Almost as soon as I touched the boost gauge hose, it popped out of the fitting. The small comression fitting was no longer around the tip of the hose causing the hose to pop out easily.

I then put the compression fitting back on the tip of the hose, used needle nose plyers to make sure it was on snug, then tightened down the hose to the gauge.

The other day I ran 15psi on my way home from work. Then the next day I ran 7psi. After I fixed the boost gauge hose, I am consistantly running 11psi. Maybe I had a boost leak from the hose going into the boost gauge. So it didn't show the correct readings and is why it ran poorly. And now that the gauge is fixed, it runs strong since there is no longer a boost leak? Would that make sense and add up?

My Tsi is basically all stock with the exceptions of a few things. My profile is up to date if you want to check it out. Isn't the stock boost pressure around 11psi? That would make a little sense if I am running 11psi right now.
I will try to do a BLT asap. Then check the wastegate for any problems. I appreciate all the help. Keep it coming.