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Discussion Starter · #1 ·
I noticed my cruze barely had any acceleration power in sixth gear this summer.
Temps where in excess of 100F (more so on interstates with hot concrete).

I disabled my AC, and think the car's air/fuel mixture is too much off.
It feels like the car is hesitating, like careful acceleration. I dare not to press the pedal too hard on the interstate, as acceleration doesn't really get better between 20-50% of the throttle.
This was in summer, but now that it's winter, I notice the car accelerates just fine, even with airco on.

There was an ECU recall, which was done to my car, but I don't think it actually helped the issue.

It's never been this hot in FLorida before, or at least, I don't remember the in car thermometer ever passing 98F in years past.
This summer it's been up to 106F.
The temps also have been on and off. Every time I thought we had the worst of the worst, I would fuel up regular (Shell 87oct), and we'd hit a high we hadn't before.
When I then fuel up mid-grade or premium, the temps dropped that week, and the car was operating normally.

Just thought of mentioning it.
 

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ProDigit, stick with premium. With this car as the temps go up so does the octane requirement. You also probably noticed a pulsing in the throttle - that's the ECU protecting the engine from ping/knock. Higher octane helps prevent this so the ECU doesn't have to throw detune the engine to protect it.
 

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I would definitely keep 93 octane in your vehicle. The surging as obermd said is the engine retarding timing to protect itself from spark knock. Also, all engines are adversely affected by hot weather as hot air is not as dense as cooler air. The issue in turbocharged cars is exasperated because turbochargers use already hot exhaust gas, makes it hotter, and then relies on a hot intercooler to cool the air before it enters the combustion chamber. In the Cruze, the intercooler is sandwiched between the radiator and A/C condenser, both of which are super hot in the summer.

TL;DR, higher octane is necessary especially when it's hot out because the combustion chamber air is going to be a lot hotter in the summer.


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The hotter the air, the less dense it is - meaning less fuel needed to combust at the proper AFR - leading to less power.
 

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I would definitely keep 93 octane in your vehicle. The surging as obermd said is the engine retarding timing to protect itself from spark knock. Also, all engines are adversely affected by hot weather as hot air is not as dense as cooler air. The issue in turbocharged cars is exasperated because turbochargers use already hot exhaust gas, makes it hotter, and then relies on a hot intercooler to cool the air before it enters the combustion chamber. In the Cruze, the intercooler is sandwiched between the radiator and A/C condenser, both of which are super hot in the summer.

TL;DR, higher octane is necessary especially when it's hot out because the combustion chamber air is going to be a lot hotter in the summer.
You have some of the science a bit messed up there, but you got the gist.

The car is pulling timing because of pre-detonation of the A/F mixture in the cylinder (aka- knocking).
 

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You have some of the science a bit messed up there, but you got the gist.

The car is pulling timing because of pre-detonation of the A/F mixture in the cylinder (aka- knocking).
Right - spark knock. The tendency to knock increases with increasing combustion temperatures. Should've added that in near the end instead of assuming the connection would be made. My bad.


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These engines are really prone to knock in hot temps - my car just feels way more lethargic in the summer with AC on than it does the rest of the year.

Like others have said, use 93.
 

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These engines are really prone to knock in hot temps - my car just feels way more lethargic in the summer with AC on than it does the rest of the year.

Like others have said, use 93.
That's pretty common with any engine, really - but a lot more noticeable on most gas four cylinders, due to the added drag on the engine. Even my 2.2L in my Cobalt gets upset when you flip the AC on (a rare occurrence) - but the Cruze diesel doesn't care at all - but you have the added rotational force due to the high compression ratio.

A tiny I4, like the 1.4T will really show the AC's drag.
 

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That's pretty common with any engine, really - but a lot more noticeable on most gas four cylinders, due to the added drag on the engine. Even my 2.2L in my Cobalt gets upset when you flip the AC on (a rare occurrence) - but the Cruze diesel doesn't care at all - but you have the added rotational force due to the high compression ratio.

A tiny I4, like the 1.4T will really show the AC's drag.
Yeah, but the high IAT temps from the intercooler/condensor/radiator sammich aren't helping matters any. Yes, it's down on power from AC compressor drag (not much at lower fan speeds), but it's also really down on power from pulling timing to keep it from knocking.

My turbo Volvo was also bad about pulling timing in the summer - but most N/A cars don't do it nearly as much.

Darn heat soak.
 

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Read up on DA (Density Altitude) when you get a chance. It looks at altitude, humidity, temperature, and barometric pressure to come up with a calculated DA value. The lower the value, the better your engine will run. It's quite common for engines to have reduced power in the summer months. I had a modified Pontiac G8 GT that I used to take to the drag strip from time to time. In the summer months, about the best it would run was 12.70s. In the spring and fall it would dip down into the 12.20s/12.30 with nothing different about the car other than the cooler weather. Me and my drag racing friends knew not to expect a new personal best in the summer and couldn't wait for fall to get here for the better ETs.
 

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Discussion Starter · #11 ·
Thanks for the confirmation.
Issues not really noticed below 100F.
Usually it doesn't get above 95-97 in the summer over here, but the last summer was unusually hot.
I will put mid-grade in it in summer, and if a heatwave is on it's way, I'll put in premium fuel.
 

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We have the same issue in Phoenix. Trifecta tune, 91+ octane fuel, and check your spark plug gap. These made a huge difference in throttle response and acceleration.
 
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