Boost variation in different climates

[IwantMKIII]

Edit: keep in mind this is a stock CT in excellent condition

Just wondering about how much boost levels should change depending on temperatures. I tuned my car in hot weather, probably 80's to 90's weather and humid (was done in Philly area PA, don't know altitude). I've noticed as its gotten colder the boost has been getting quite a bit higher which is normal. However this extreme cold weather is now kicking in. I was driving to Detroit from Charleston (WV) and was in 5th boosting 18.1lbs of boost :aigo: within seconds of pressing the throttle (around 3100RPM), this was confirmed with my mechanical gauge as well. Thought this was a bit extreme since i have it normally around 11-12PSI

Setting in warm weather are for 11-12PSI at ~38% Greddy Profec II (all gain settings down as low as possible)

setting in cold weather (ie ~10-15*F) ~35% 18.1PSI. Had to turn in down all the way to ~22%.

Are these gains normal or should i be looking for a possible problem.

 

[gaboonviper85]

As I mentioned on the phone....when weather turns cold, your psi should drop a bit...gaining psi is not normal in cold weather...you hit fuel cut at 12psi this summer so you should be fuel cutting at let's say 10 psi now.....but if you head higher in altitude then you'll start to see higher boost psi considering the air gets thinner...

But gaining psi is not normal when weather gets cold....it should be droping...

Where you driveing uphill when it hit 18 psi? How far north where you when it happened?

Come to think about it...I never felt your car hit fuel cut this summer either...although you probably wouldn't hit fuel cut at 3500rpm anyway...

 

[grimreaper]

I too have similar results. Warm weather= 16psi, near freezing= 18+ psi. I thought it was backwards but no fuel cut either. Doesnt "feel" any stronger though.

im guessing the altitude difference has to be significant, but here it DFW the difference is only a few hundred feet MAX

 

[91toy]

I'm no rocket scientist, and this is only my second turbo car, neither of which I drive in winter, it would seem to me that the colder the air is, the denser it will be and the easier it should be to compress to make boost. Having said that, shouldn't your wastegate regulate the pressure to the level regardless of temperature?

 

[IwantMKIII]

I'm no rocket scientist, and this is only my second turbo car, neither of which I drive in winter, it would seem to me that the colder the air is, the denser it will be and the easier it should be to compress to make boost. Having said that, shouldn't your wastegate regulate the pressure to the level regardless of temperature?

the wastegate is electronically controlled by a %. The more %, the more the boost solenoid opens and closes, this ultimately decides the PSI levels with Greddy Profec B spec II's

I found on a few of other websites where drivers PSI goes up with lower temps...just not sure how much is normal

 

[trydrew]

I was on my way home from Dayton (75miles away) the other night and had my Profec BII set to LO which I have at about 15% (8 psi with controllable quick response "DD mode"). Well I got the the S I75 bridge and it was clear. My oil pressure was making a noticable climb on my gauge by now thanks to me taking it easy in the 5*F weather. I figured my cooler curcuit was still cooling it despite the thermo being closed, that said, I decided to warm it to OT with my hairdryer .

I down shifted to forth and it held on at what felt like normal boost until about 4200ish rpm. Then it hit fuel cut twice before i got out of it. I backed out and eased back into it (experimenting, it's done this before). It then pulled fine again at ~8psi through the rest of fourth.

Well, later down the road, I did a fifth gear pull and this time I had view of the BC head unit. Well my warning was set for 13.5psi with no limiter, because it shouldn't be that high in that setting anyway. Well I started pulling and I saw the screen go red so I watched it. It slowly (relatively) climbed all the way to 15.1 before FC. I noramlly hit FC at just below 14. Well I got back into it and it boosted good again...

What i'm concerned about is why is my BC slipping liike that?

 

[IwantMKIII]

well i was driving in the same weather as you, last night....in the same area, I75. Given we both have Greddy Profec and are both experiencing the same problem, i find it odd yet comforting. Only difference is mine uses a Perrin boost solenoid as my Greddy burned up in the fire 8 months ago.