# Decreased Engine Performance Very Hot Weather



## jblackburn (Apr 14, 2012)

Yeah, seems like everyone else with the 1.4T notices that, but I haven't heard much about the 1.8.

I've got mine to where it's decently drivable as normal if the A/C isn't on fan speed 4. How?

-Airbox resonator delete (see how to forum) helped tremendously with pickup from a stoplight. I'd like to get a cold air intake.
-Regap spark plugs to .035".
-Run more than 87 octane. 87 is probably detonating at low RPM and causing the engine to lose power.


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## Skraeling (May 30, 2012)

Isnt the 1.8 a non turbo? If hes detonating on a N/A engine on 87... the cars crap or somethings wrong. Regardless of how hot it is. It was 105 yesterday and the 1.4t was doing fine on 87.


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## jblackburn (Apr 14, 2012)

Mine chokes any time it's above 90 on 87 octane in stop-and-go traffic.

The inconsistencies in spark plug gaps alone I believe tend to confuse the cars computers and would be worth checking.


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## Skraeling (May 30, 2012)

If hes having engine issues, it needs checked out. Thats not normal behavior.


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## jblackburn (Apr 14, 2012)

Skraeling said:


> If hes having engine issues, it needs checked out. Thats not normal behavior.


See above.


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## Dale_K (Jul 16, 2011)

I have an LS with manual trans too. I notice a dropoff in power in hot weather with the A/C but it's liveable. The Cruze A/C compressor has variable displacement. It works harder when it needs to and it makes sense that you might feel the extra drag when the compressor was operating at maximum capacity.


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## coinneach (Apr 10, 2012)

All internal combustion engines make less power in hot weather. It's simple physics: hot air = less dense = less fuel needed to maintain 14:1 stoichiometric ratio. Forced induction helps, but doesn't eliminate the problem.

In the general aviation world, there's a rash of takeoff crashes every summer because pilots forget to set the engine's mixture for best power (full rich is the usual practice at low altitudes) and don't recalculate their runway requirements. We don't have it quite that bad, but you'll never see the same performance from any engine in summer as in winter.


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## obermd (Mar 3, 2012)

:sigh:


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## S101986 (Jul 21, 2012)

Mine shuts off if it's above 80 at random times ac on or off.


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## sciphi (Aug 26, 2011)

These engines just seem not to like hot weather. Not sure why, but they don't. Fuel mileage goes down, and if you run the A/C, forget about going anywhere quickly. Eh, likely just a quirk of the car.


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## Gritts (Jan 23, 2011)

I've noticed a decrease in MPGs (about 2) in summer. However, power remains unchanged. I re-gapped to .035" on the plugs, have a K&N drop-in filter and a dual outlet exhaust. I don't think deleting the resonator helps at all and probably hurts performance (that was my experience anyway). I have an LS with the manual transmisson. Using a higher octane fuel might help if there is a problem with knock. Does anyone know if Ethanol is blended into the higher octane fuels?

BTW, since I'm back to using the snorkel, I drilled some holes in the top portion of the grill to get air directly into the snorkel's mouth. Otherwise, air is fed to the snorkel from the opening around the hood latch. Yikes!


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## XtremeRevolution (Jan 19, 2012)

Gritts said:


> I've noticed a decrease in MPGs (about 2) in summer. However, power remains unchanged. I re-gapped to .035" on the plugs, have a K&N drop-in filter and a dual outlet exhaust. I don't think deleting the resonator helps at all and probably hurts performance (that was my experience anyway). I have an LS with the manual transmisson. Using a higher octane fuel might help if there is a problem with knock. Does anyone know if Ethanol is blended into the higher octane fuels?
> 
> BTW, since I'm back to using the snorkel, I drilled some holes in the top portion of the grill to get air directly into the snorkel's mouth. Otherwise, air is fed to the snorkel from the opening around the hood latch. Yikes!


How big are the holes you drilled? Keep in mind, air will travel through the easiest path. The intake sucks air through the snorkel, and creates a negative pressure in that chamber. That negative pressure will pull air through the easiest path, which will still pull plenty of hot air from the engine bay. 

The resonator bypass pulls air from lower down in the fenderwell where it's at least colder, and removes the restriction of the 3-5 feet of plumbing and the resonator box the air would otherwise have to travel. It's basically the same place as where the Injen cold air intake pulls the air from.


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## XtremeRevolution (Jan 19, 2012)

Mine is usually ok on power when it gets hot, but a couple of days ago it was well over 100 degrees out and the car felt like it had significantly less power than it usually does. The only difference between this time and the hot days before it was my reduction in spark plug gap from .038 to .033. I think I'll be raising them to .035 this weekend.


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## rgenther (Jul 28, 2012)

MWCOOL said:


> I have a 2011 Cruze LS Manual 6 Speed, 1.8 with 55K on it. This is the second summer that when it's over 90 degrees that the engine bogs down quite a bit. This is not about A/C on or off. I typically run the A/C when it's high 70's anyway and the car performs fine. As soon as it gets around 90 I find my self downshifting on the same roads I normally stay in high gear and the car often dogs on leaving an intersection. Also, mileage drops 4-5 mpg during very hot periods. Anyone else?


My 2011 Eco Power during hot weather or stop and go errands feels like its going to stall then very slowly picks up speed, but seems to work itself out after a few stop-lights. You can forget, even on its best day, beating someone off the line for more than a few inches. Performs pretty well at FWY speeds, the turbo is pretty strong when needed. The Gas tank has a sense a humor, never sure where it will stop filling. Not too happy with the fresh air vents sending warm air into the car, we find ourselves using the air on rainy cool days and on a hot day it takes forever to cool the Interior, not to mention we seem to need the fan on high most of the time.
Our dealer said to never use octane above 87, it would not do any good, was this Bull to get us to buy? Would appreciate a professional opinion, I would be happy to step to 89 if my performance will improve.


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## XtremeRevolution (Jan 19, 2012)

rgenther said:


> My 2011 Eco Power during hot weather or stop and go errands feels like its going to stall then very slowly picks up speed, but seems to work itself out after a few stop-lights. You can forget, even on its best day, beating someone off the line for more than a few inches. Performs pretty well at FWY speeds, the turbo is pretty strong when needed. The Gas tank has a sense a humor, never sure where it will stop filling. Not too happy with the fresh air vents sending warm air into the car, we find ourselves using the air on rainy cool days and on a hot day it takes forever to cool the Interior, not to mention we seem to need the fan on high most of the time.
> Our dealer said to never use octane above 87, it would not do any good, was this Bull to get us to buy? Would appreciate a professional opinion, I would be happy to step to 89 if my performance will improve.


89 and 93 octane will definitely help, especially in hot weather. This has been tested and proven not only by tuners, but also by a few magazine review companies. 

Sent from my Bulletproof_Doubleshot using AutoGuide.Com Free App


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## Gritts (Jan 23, 2011)

XtremeRevolution said:


> How big are the holes you drilled? Keep in mind, air will travel through the easiest path. The intake sucks air through the snorkel, and creates a negative pressure in that chamber. That negative pressure will pull air through the easiest path, which will still pull plenty of hot air from the engine bay.
> 
> The resonator bypass pulls air from lower down in the fenderwell where it's at least colder, and removes the restriction of the 3-5 feet of plumbing and the resonator box the air would otherwise have to travel. It's basically the same place as where the Injen cold air intake pulls the air from.


The resonator is designed to provide more torque at lower RPMs that is why I re-installed the unit. I also like a quiet engine. As for the holes--I used a 3/8 bit and drilled a few holes in the front upper grill (you can't see the holes because of the way the grill is made) to allow more air into the snorkel. Perhaps the best solution would be to leave the resonator, but remove the snorkel. My thinking is the snorkel is there for some reason--probably just to prevent water from getting into the intake. I drilled the holes trying to achieve a 'ram air' effect.

Believe me--I like my Cruze--and like everyone else I try to get the most from the little engine. But you can't change lead into gold and if I could afford it, I would upgrade to the Verano 2.0 or a Camaro. (Heck, a Cruze Eco with a tune would be a big improvement). I wish they would bump up my GM card!


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## obermd (Mar 3, 2012)

XtremeRevolution said:


> 89 and 93 octane will definitely help, especially in hot weather. This has been tested and proven not only by tuners, but also by a few magazine review companies.


And multiple CT members. What you're looking for when increasing octane is throttle smoothness. Increase your octane one step at a time. Once the throttle is smooth during acceleration, there is no reason to go to the next higher octane.


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## rgenther (Jul 28, 2012)

XtremeRevolution said:


> 89 and 93 octane will definitely help, especially in hot weather. This has been tested and proven not only by tuners, but also by a few magazine review companies.
> 
> Sent from my Bulletproof_Doubleshot using AutoGuide.Com Free App


Perfect time for me to do a test. We live in Pasadena, CA. We are doing an early Sunday Morning Vegas Run and I filled up last night with 87. I will fill-up on Tuesday on the way home, from Vegas, with 91 and see what the Computer numbers say. Won't be a complete fill-up but more than 1/2 a tank. The trip back from Vegas will be about mid-day right through the desert.


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## rgenther (Jul 28, 2012)

rgenther said:


> Perfect time for me to do a test. We live in Pasadena, CA. We are doing an early Sunday Morning Vegas Run and I filled up last night with 87. I will fill-up on Tuesday on the way home, from Vegas, with 91 and see what the Computer numbers say. Won't be a complete fill-up but more than 1/2 a tank. The trip back from Vegas will be about mid-day right through the desert.


So much for that test, The weather was cooler than normal, the traffic snarls were often and my Mileage was an unimpressive 34.5 (according to the Car). We even got a lightening show with cloud bursts nearing Stateline NV driving home reminding me that this light little car is very stable on the highway. As for the power, in hot weather, issue, I guess I will find out if 92 Octane helps when the weather heats back up . . .(no hurry, I like the unusually cool summer temps)


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## XtremeRevolution (Jan 19, 2012)

Gritts said:


> The resonator is designed to provide more torque at lower RPMs that is why I re-installed the unit.


I would like to know how you came to the conclusion that a resonator box, which is designed to reduce turbo noise, is able to provide more torque while also creating an additional restriction point in the path of airflow. 

Sent from my Bulletproof_Doubleshot using AutoGuide.Com Free App


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## jblackburn (Apr 14, 2012)

XtremeRevolution said:


> I would like to know how you came to the conclusion that a resonator box, which is designed to reduce turbo noise, is able to provide more torque while also creating an additional restriction point in the path of airflow.
> 
> Sent from my Bulletproof_Doubleshot using AutoGuide.Com Free App


Especially when the exact opposite happens...just sayin. 


Sent from my Autoguide iPhone app


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## Beachernaut (Mar 27, 2012)

I have the same behavior in my car. Anything above 80 degrees and the car doesn't like low rpm. From a stop it's very bad if I have the AC on. I believe part of that is also compounded by my altitude. Figure somewhere between 18 and 20% power loss due to altitude (out of boost) + air density + heat soak + AC drag = fighting a stall unless I rev up to get some boost while taking off.


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## Healtotoe (May 21, 2012)

I have noticed the same problem. Last week I gassed up on a 1/2 tank of Shell 87 with Mobil 87. I noticed the car bogged down more than usual when it was very hot in the afternoon (car's temp read 102). I added about 3 gallons of Shell 89 and 3 gallons of Shell 87 to the original mix. The car seemed to run better after about 10 miles or so. I wonder if mixing different gas brands makes a difference or whether one brand is better at high temps over the other.


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## Healtotoe (May 21, 2012)

One thought....could inconsistent spark plug gaps cause/exacerbate this hot weather problem?


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## jblackburn (Apr 14, 2012)

healtotoe said:


> one thought....could inconsistent spark plug gaps cause/exacerbate this hot weather problem?


yes


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## obermd (Mar 3, 2012)

Healtotoe said:


> I have noticed the same problem. Last week I gassed up on a 1/2 tank of Shell 87 with Mobil 87. I noticed the car bogged down more than usual when it was very hot in the afternoon (car's temp read 102). I added about 3 gallons of Shell 89 and 3 gallons of Shell 87 to the original mix. The car seemed to run better after about 10 miles or so. I wonder if mixing different gas brands makes a difference or whether one brand is better at high temps over the other.


Octane. Higher octane is more resistant to knock. The Cruze's ECU is very aggressive when it comes to knock elmination. It does this by backing off the spark timings, which reduces power. Higher octane gas is more resistant to knocking so the ECU doesn't have to play with the spark timing as much. As a result both power and MPG are improved.

The 10 miles it took to start running better is the distance it took to replace the 87 octane in the fuel line between the tank fuel pump and the injectors.


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## Skraeling (May 30, 2012)

snorkus (read: silencer deletes) were popular among older wrx's that still had them.


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## Healtotoe (May 21, 2012)

obermd said:


> Octane. Higher octane is more resistant to knock. The Cruze's ECU is very aggressive when it comes to knock elmination. It does this by backing off the spark timings, which reduces power. Higher octane gas is more resistant to knocking so the ECU doesn't have to play with the spark timing as much. As a result both power and MPG are improved.
> 
> The 10 miles it took to start running better is the distance it took to replace the 87 octane in the fuel line between the tank fuel pump and the injectors.


Very interesting. Thank you for that explanation. I assume the knocking is polluting. Otherwise, why would they want to decrease the power/mileage. I recall somewhere that higher octane fuels burn hotter. Perhaps they don't want the higher engine temps so they say to stay with 87 octane.


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## XtremeRevolution (Jan 19, 2012)

Healtotoe said:


> Very interesting. Thank you for that explanation. I assume the knocking is polluting. Otherwise, why would they want to decrease the power/mileage. I recall somewhere that higher octane fuels burn hotter. Perhaps they don't want the higher engine temps so they say to stay with 87 octane.


Knocking is detonation; when your fuel ignites as a result of a source other than the spark plug,_ after the spark plug has already ignited the mixture. _It can cause serious engine damage if not tuned for. Small amounts of knock are detected by the ECM long before dangerous levels appear. The ECM pulls back ignition timing in order to prevent this knock. However, that timing retard also robs power. 

Running a higher octane fuel allows whatever it is that's causing the knock to have less of a chance to create knock, allowing the ECM to advance timing and give you more power per amount of fuel used. The technical term for the ECM's reaction to knock is called KR (knock retard). Without it, you could have a nice big hole or crack in your piston. 

Unfortunately, there's only so much explanation one can do on this topic without teaching the fundamentals of ignition timing.


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## Healtotoe (May 21, 2012)

XtremeRevolution said:


> Knocking is detonation; when your fuel ignites as a result of a source other than the spark plug. It can cause serious engine damage if not tuned for. Small amounts of knock are detected by the ECM long before dangerous levels appear. The ECM pulls back ignition timing in order to prevent this knock. However, that timing retard also robs power.
> 
> Running a higher octane fuel allows whatever it is that's causing the knock to have less of a chance to create knock, allowing the ECM to advance timing and give you more power per amount of fuel used. The technical term for the ECM's reaction to knock is called KR (knock retard). Without it, you could have a nice big hole or crack in your piston.
> 
> Unfortunately, there's only so much explanation one can do on this topic without teaching the fundamentals of ignition timing.


Thank you. That is an excellent description. I never knew that and it makes a lot of sense.


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## XtremeRevolution (Jan 19, 2012)

Healtotoe said:


> Thank you. That is an excellent description. I never knew that and it makes a lot of sense.


Technically, I misworded my post. I was referring to pre-ignition, not detonation by definition, so I updated that post. 

Pre-ignition as I described earlier is the result of the air-fuel mixture being ignited by an external factor, such as hot spots in the combustion chamber or carbon build-up. Detonation is the spontaneous combustion of the remaining air-fuel ratio in the cylinder after the spark plug has ignited the mixture. 

Detonation can be tuned for. Pre-ignition can be catastrophic. Imagine the air-fuel ratio igniting some time before the spark plug ignites it. The resulting pressure wave on the piston as it's moving up is like the slam of a jackhammer. the crankshaft keeps turning, but the piston stops. Do the math. Higher octane fuel and lower air intake temperatures help prevent this from happening. 

For those who want to learn this in more detail, the following pages explain it very well:

Engine Basics: Detonation and Pre-Ignition: Streetrod Stuff
Detonation and Pre-Ignition



> As you may recall, increased fuel octane will increase the temperature required for spontaneous combustion of the gas. But any gas will spontaneously ignite at some given temperature. If the pressures and resulting heat generated by the combustion chamber reaches that spontaneous combustion temperature of the gas, havoc breaks loose within the combustion chamber, and the above picture shows the results.
> 
> With normal burn rates.* The linear expansion of pressures are handled by the engine parts. This is because the energy expended by the burn is extended over a lengthy period of time (tens of crankshaft degrees). Detonation expends this energy all at once which creates a spiked compression pressure rise. This spiked pressure rise hammers against the piston top and combustion chamber walls, and makes that metallic hammer sound, sometimes referred to as a ping or rattle.* Some forms of detonation make very little noise yet cause very great damage. This sudden release of energy has several down sides.
> 
> ...


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## obermd (Mar 3, 2012)

XtremeRevolution said:


> Knocking is detonation; when your fuel ignites as a result of a source other than the spark plug,_ after the spark plug has already ignited the mixture. _It can cause serious engine damage if not tuned for. Small amounts of knock are detected by the ECM long before dangerous levels appear. The ECM pulls back ignition timing in order to prevent this knock. However, that timing retard also robs power.
> 
> Running a higher octane fuel allows whatever it is that's causing the knock to have less of a chance to create knock, allowing the ECM to advance timing and give you more power per amount of fuel used. The technical term for the ECM's reaction to knock is called KR (knock retard). Without it, you could have a nice big hole or crack in your piston.
> 
> Unfortunately, there's only so much explanation one can do on this topic without teaching the fundamentals of ignition timing.


Knocking can lead to increased tail pipe emissions as well since the fuel isn't burning properly. The other big factor that appears to be playing in the Cruze engines is improperly gapped spark plugs. When the plugs aren't gapped properly the fuel doesn't burn completely at ignition. Some fuel can actually be left behind in the cylinder, leading to a higher incidence of premature ignition on the next cycle. This is especially noticable when the plugs are gapped the same, much less to the correct spec. This is why you'll see repeated recommendations in multiple threads to check and correctly gap your spark plugs. Here are the specs according to Chevy:

1.8L engine 0.028"
1.4T engine 0.033 - 0.037" (original according to the dealership service guide)
1.4T engine 0.025 - 0.027" (current according to Tom Reid at GM Powertrain - thanks to XtremeRevolution for running this down for us)


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## joelunchbox (Aug 8, 2018)

I've got a 2015 cruze 1.4 turbo. It's my wife's car so I don't drive it often. Two weeks ago I got to drive it and I was astounded by the lack of power on the highway. Only way to accelerate was when it downshifted and even then I wasn't impressed. I don't like my cars to run poorly. I got a scan tool with live data and this past weekend I got my wife to drive around while I watched the data. Of course, the car ran fine. Getting a little over 20 inches of boost and the car never downshifted as she accelerated. She was actually pushing the car harder than I had! Reading this thread, something occurred to me--inlet air temp. I am almost hoping for another really hot day so I can hook up the scan tool and monitor air intake temps. Gotta be something that makes the computer pull back power.


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## jblackburn (Apr 14, 2012)

joelunchbox said:


> I've got a 2015 cruze 1.4 turbo. It's my wife's car so I don't drive it often. Two weeks ago I got to drive it and I was astounded by the lack of power on the highway. Only way to accelerate was when it downshifted and even then I wasn't impressed. I don't like my cars to run poorly. I got a scan tool with live data and this past weekend I got my wife to drive around while I watched the data. Of course, the car ran fine. Getting a little over 20 inches of boost and the car never downshifted as she accelerated. She was actually pushing the car harder than I had! Reading this thread, something occurred to me--inlet air temp. I am almost hoping for another really hot day so I can hook up the scan tool and monitor air intake temps. Gotta be something that makes the computer pull back power.


87 octane in hot weather retards timing hugely.


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## Bluelight (Jan 17, 2018)

coinneach said:


> All internal combustion engines make less power in hot weather. It's simple physics: hot air = less dense = less fuel needed to maintain 14:1 stoichiometric ratio. Forced induction helps, but doesn't eliminate the problem.
> 
> In the general aviation world, there's a rash of takeoff crashes every summer because pilots forget to set the engine's mixture for best power (full rich is the usual practice at low altitudes) and don't recalculate their runway requirements. We don't have it quite that bad, but you'll never see the same performance from any engine in summer as in winter.


One thing to add to this is elevation. If the OP is in a high desert region, they are already starting out with thin air to begin with, and this "hot n' high" operation is a serious power suck, especially in naturally aspirated engines.

Summer before last, I was driving through eastern BC, which is nearly a mile up and the temp was in the mid-90s. The ZX2 I had at the time, which normally had no trouble lighting up it's own tires in lower/cooler conditions, couldn't get out of it's own way. Hitting the gas felt more like an electric shopping cart than a car!


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