Cooler Weather and Higher Supercharged Boost
 

I'm seeing boost pressures increase as ambient temperatures drop. I knew I might see an increase in a pound, MAYBE two, but am seeing as much as 4-psi higher. I've read of many people seeing around 1-2, and a couple seeing 3-4 (as I am), but wanted to see if anyone else has noticed with weather getting cooler.

I'm running stock exhaust and the stock 90mm Magnuson pulley. With ambients around 90*, I'd see 13-14-psi. There was a cool morning I wanted to recheck the tune on, and I was seeing 18-19-psi (and NO changes mechanically or to the tune, except for fueling and ignition timing [I lowered timing for tuning]) when it was in the mid-60*s. I didn't change cam timing or anything, only adjusting for fueling and I retarded the timing for safety. I was thinking maybe my cats' are clogging, but they were visually perfect a couple hundred miles ago, and the car only has about 1100-miles on it. My fueling, at the 18-19-psi was a little fat, and I wasn't getting any crazy retard, but I'm more concerned with the high pressure. My injector PW is under 6 and nothing is really showing me I need to be concerned in the logs.
I'm not confident that is it choked exhaust, because, after warming the car up, I made a hit, where I got 18-19-pounds, and made a few more hits within about 10-minutes (I never shut the car off - all of these runs were the same tune, same time, etc.), and I got one more close to the same, but also showed boost falling closer to normal in the later runs... Maybe I'm wrong, but I'd think restriction would increase as I made more runs, even though that's not what happened.

Does anyone have any insight? I never really logged the 1.7 blower, and the gauge was showing around 11-psi, but now that I'm logging the 2650, and know that boost should be something around 14-psi, I'm just concerned with logs showing up to 18-19-pounds. Thanks for any comments or thoughts.

Yes I see a increase of about 1-1.5 psi from 70-90 degree weather compared to 55-65 degree weather. It definitely pulls harder on the fuel system too.

Cooler air is denser and that equals more boost.

Exactly! Just saw a solid 1.5 psi increase this past weekend too. Weather is definitely having an impact.

My ZL1 seems to love the cooler dense air of the Fall now!

My car was loving it last night, went up into the Hollywood hills at 10 pm on Mulholland Dr. with fog rolling over the top and car was flying, throttle response felt quicker and tires spinning like crazy. Then today heat is back and it's 102 F tomorrow.

Having had several sc vehicles over the years, that is my typical experience. With the ZL1 I'm curious as to the hp gains of 1-1.5lbs more boost?

Boost weather is real

All other things remaining the same, boost increases as DA increases. We could figure out an equation.

Thank you for all your responses. You've confirmed a lot for me.

What I question is just how much more boost I'm getting. About 4-psi. Admittedly - because this great State (right...) is still burning, I could perhaps see how much of my testing/tuning during this time might, theoretically, see a bit lower boost, on account of the smoke displacing some of the oxygen. My runs with the boost 4-psi higher were on days there seemed to be less smoke, and obviously, cooler air, so some of that (increase in boost) makes sense. I was advised that perhaps the newness of the blower, on a new car, could play a role in that, too, so maybe all of these little factors can add up.

Does anyone have an option on the OEM LT4 short block holding up, so long as the tune and fuel are okay? I know there are many shops that build combinations well-into the teens (boost), but that's with a bigger cam, LTs, etc. I'm only running a Big Gulp and gutted resonators (I was hoping to lower heat/restriction because I need to keep the primary cats' at least), and even though my data logging shows my fueling is adequate (for now) and I'm not showing anything weird, I just needed to hear I'm within the realm of what other people are seeing. IAT 2s aren't showing any change with the higher boost. I will admit these are just real short runs from a dig to more more than about 80, so a 1/4-run would probably see slightly higher heat (though - my IAT 2s rarely increase more than a degree after a run starts - they usually fall after I get some air flow).

Thanks again for any comments or input you feel like adding. I do read and think about all of them. Your time sharing is not wasted.