[6speedTi]

Cooler then stock is all you need.

That colder 40* or whatever works wonders on parts lasting longer.

That stock temp for the gen1 is why you all have the problems you all have. I don't know what GM was thinking when they did that. It certainly didn't do wonders for their profits.

Higher temps are for emissions. You get a cleaner burn at higher temps. That is why I believe the ECU is program to run at higher temps for cleaner emissions. If the temps run colder then the ECU may not reach its Optimum settings for proper emmisions. It may not make a difference to the daily driver but that is why the higher running temps. Too bad the failure rate of these parts is high from higher temps.

 

[snowwy66]

NOX goes up.

 

[BigLee]

Engine temperature wont significantly affect NOx.
Maybe if its overheating it might affect it more.
NOx forms when combustion temps exceed around 2500°F.
They used to control this with EGR.
The exhaust gas was mixed into the intake charge to act as a buffer gas, preventing peak combustion temps from crossing over 2500°.
Nowadays, they simply allow it to form during combustion, and use improved catalytic converters to break it back down.
The higher engine temps are meant to help reduce hydrocarbon emissions. The difference is small though. But with the EPA counting every molecule coming out of the tailpipe, it sometimes helps tip the scales into a more favorable emissions tier category, which gets additional credits to the manufacturer...

 

[CRUISE-CRUZE]

I agree.
I think that the plastic cooling system components are very close to their limits of durability, especially longterm.
My 13 Sonic has had 4 water pumps (not plastic, but the seals are definitely stressed), 2 resivoirs, a water outlet, and a radiator replaced.
I think that lowering both the temperature and pressure will greatly reduce the stress on these parts.
Lower pressure surge tank caps are available, and are definitely recommended as well.
GM/ACDelco part#s are:
15 psi - 15075117 / RC98
9 psi. - 88986846 / RC108
The 9 psi cap is probably best used after the cooler thermostat, and an auxiliary radiator fan switch is installed.

Just look at my original post and see the picture with the initial coolant reservoir. High temperature & high pressure are not for this vehicle! The 15psi cap works the best, going to 9psi may risk to boil the coolant if the mixture is not properly done.
And I said before, GM moved back to a lower temperature thermostat lately. Look for example the 2018 Cruze, it has the thermostat that starts opening at 180F! In theory, yes, higher temp and pressure will give you better performances. IF.. you use quality components, but if you try to cut cost everywhere, using cheap materials, then have the decency and change also the mechanical components to adjust to the new situation.

 

[plano-doug]

IF.. you use quality components, but if you try to cut cost everywhere, using cheap materials, then have the decency and change also the mechanical components to adjust to the new situation.

I see this as more a case of inadequate qualification testing rather than going cheap. Given the time frame of when this car came to market in the US, during development they were recovering from the 2008 meltdown, and were surely somewhat disorganized and likely short-handed.

So, while getting all the components tested and qual'd, as necessary for ramping production, they probably had a mixture of not enough test time to find all the vulnerable components, and not enough time to fix everything properly when they did - ie, to re-qual improved components - so some questionable pieces went into production. Coolant reservoirs and water outlets come to mind.

I'm not absolving them of blame, just trying to illustrate that, in many cases, it's not obvious where the weak joints are, so to speak, until you've got a significant number in the field, or lots of time spent in the test labs trying to identify all the marginal stuff, and trying to do accelerated testing, hoping to do a life-cycle test in only four months

There's an old saying: It's time to shoot the engineers and start production. They can't miss the start of the model year - they have to ship something to the dealers regardless of whether every last kink has been worked out or not. That's why it's not good to buy the first model year. Unfortunately, some of these problems lingered into the 2nd and 3rd model years

Doug

.

 

[BigLee]

And some of the problems persist to this day, sometimes despite 2 or 3 supposed design revisions to address known issues...

This engine was an Opel design to begin with, so it was in use in Europe for 3-4 years before being offered in the U.S. market.
It had sufficient time to get the bugs ironed out.
I dont know what temps or pressures these early European market vehicles used though.
Perhaps GM upped them on the U.S. models.

 

[BigLee]

Just look at my original post and see the picture with the initial coolant reservoir. High temperature & high pressure are not for this vehicle! The 15psi cap works the best, going to 9psi may risk to boil the coolant if the mixture is not properly done.
And I said before, GM moved back to a lower temperature thermostat lately. Look for example the 2018 Cruze, it has the thermostat that starts opening at 180F! In theory, yes, higher temp and pressure will give you better performances. IF.. you use quality components, but if you try to cut cost everywhere, using cheap materials, then have the decency and change also the mechanical components to adjust to the new situation. View attachment 283383

I agree.
Maybe I'm a little overly cautious with using the 9 psi cap, but thus far, it's working well on both vehicles, and I am confident that cracked plastic cooling system parts are a thing of the past.
I work at a GM dealership, and I see first hand the number of failed cooling system parts being replaced on Sonic, Cruze, Trax and Encores. It's rare that a day goes by without one of these vehicles being in our shop for a coolant leak somewhere...
Mixtures are good...
And I've had a long history with running cooling system pressures between 7-10 psi on lots of vehicles in the past. No issues from it.

 

[BigLee]

Just an update.
My Sonic has been using the Dorman 176° thermostat for over a month now, and our Trax has had it for over 2 weeks, and both passed OBD inspection today.
The spring issue I mentioned above doesnt seem to have made a difference after all, as both vehicles seem to have pretty much the same operating temps on the highway.
Both cars are daily driven, and
no codes have appeared on either vehicle.

 

[snowwy66]

IIRC.

You only need somewhere around 135 before emissions ready. Might be lower. Been a long time since I checked it out.

 

[BigLee]

I assume you are talking about going to closed loop.
And 133-135°F used to be the minimum temp before closed loop was permitted on older GM models, but these cars are capable of going to closed loop operation at much lower temps.
I've seen my Sonic go to closed loop after a cold start at ~45°F ambient at ~65°F coolant temperature in as little as around 40 seconds after starting.

But if you are talking about the readiness monitors, they are already set from previous drives, regardless of current coolant temps.

 

[Cwooz]

Just wanted to say thank you for the solution you provided and taking the time to share it with the rest of us. I have a 2012 1.4 that has had all the problems; several multiple times. I read your solution, ordered the Dorman thermostat, and received it today. I removed my old thermostat housing, removed the thermostat, then realized i had replaced it with a non-oem the last time it failed. You must have the oem housing for this to work!
Fully committed, i went to the dealer and bought the oem part, which i brought home, modified with the "old school" thermostat, and reinstalled. It works exactly as you said. I've been driving around all afternoon, watching the almost imperceptible movement of the guage as the thermostat opens and closes. Perfect!
I also replaced the cap with a 15psi cap. Thanks again.

 

[BU54]

I have an actual temperature gauge on my '66 chevelle that reads in fahrenheit. Thermostat opens at 195*F and I can see the temp gauge drop when it does. Now that's the way it should be without computer controlled or assisted crap. Ahhh the good ole days gone by....

 

[HL66]

Installing a colder thermostat might set a DTC for thermostat performance sooner or later. The ECU monitors operation of the thermostat by comparing engine and radiator Temperature and maybe also ambient temperature and expects specific values after a certain engine run time. If they`re not met, it will set a code and MIL after a few drive cycles
You can alter the desired ECT by changing it in the calibration

@BigLee:
the engine does have internal exhaust gas recirculation.. this is realized by the VVT system, not by an external EGR valve.. in medium load conditions, specific timing of the exhaust cam makes the exhaust valves stay open for some time of the intake cycle… this allows some exhaust gases to be sucked back from the exhaust manifold into the combustion chamber and being burned again. In this engine this is enough to reach the desired emissions

 

[snowwy66]

Valve overlap. I think that's what it was called.

Engines have always had that.

Intake opens up slightly before TDC. Exhaust closes slightly after TDC.

Probably different these days. As far as timing to piston position.

 

[BigLee]

Installing a colder thermostat might set a DTC for thermostat performance sooner or later. The ECU monitors operation of the thermostat by comparing engine and radiator Temperature and maybe also ambient temperature and expects specific values after a certain engine run time. If they`re not met, it will set a code and MIL after a few drive cycles
You can alter the desired ECT by changing it in the calibration

@BigLee:
the engine does have internal exhaust gas recirculation.. this is realized by the VVT system, not by an external EGR valve.. in medium load conditions, specific timing of the exhaust cam makes the exhaust valves stay open for some time of the intake cycle… this allows some exhaust gases to be sucked back from the exhaust manifold into the combustion chamber and being burned again. In this engine this is enough to reach the desired emissions

Well, my car has been through a few hundred drive cycles with the cooler thermostat, and so far no codes.
Not saying it wont ever set a code for low temp. Fall and winter are approaching, and we'll see how things go then at ~176°
It went through last winter at ~190° without issues.

And VVT isnt there to provide EGR.
The valve timing alterations needed to attain sufficient exhaust gas dilution would almost certainly be detrimental to both fuel economy and driveability. While it's true that you almost always have some residual exhaust gas in the cylinder from the previous firing, it's not enough to to prevent NOx formation threshold.
The formation of NOx is actually an indication of a more fuel efficient combustion event, as it provides more heat (and thus pressure) to drive the piston with.
The converters break down the resulting NOx...

 

[HL66]

Sorry, VVT on a gasoline engine can be used for internal EGR and top optimize torque and power ..

check this for example

Exhaust Gas Recirculation (EGR) System

 

[BigLee]

Sorry, VVT on a gasoline engine can be used for internal EGR and top optimize torque and power ..

check this for example

Exhaust Gas Recirculation (EGR) System

Key words are "can be used".
Like I said, if you are using VVT as EGR, then you are sacrificing power, drivability and fuel economy for NOx reduction.
What a waste of VVTs potential, when either an actual EGR valve or converter could be used to achieve it, while letting VVT focus on it's more beneficial aspects.
Besides, many non-VVT engines have also ditched their EGR valves as well.
The later model Chevy 4.3s (iron) and LS family V8s (pre-VVT models) come to mind.
So how are they controlling NOx?
The converters...
Converters are the preferred method of controlling NOx now.
It let's VVT focus on more beneficial things, and eliminates the efficiency reducing aspects of diluting the intake charge with buffer gas, which requires increased ignition advance to maintain efficiency, reduces peak heat energy extraction, and increases the odds of misfires.
All three of these things are undesirable.

Causes of High NOx Emissions

NOx (or nitrogen oxide) is a chemical in automotive exhaust that gets created when the temperature inside a vehicle engine's combustion chamber exceeds 2,500 degrees Fahrenheit. It is a pollutant that helps create smog, acid rain and particulate pollution. This can cause health problems for...

itstillruns.com

Technology Details | MECA

www.meca.org

 

[BigLee]

Sorry.
Double post.

 

[snowwy66]

NOx increases as engine temps increase. As already posted.

That's why I"m surprised GM went with a 220 thermostat for the gen1. More NOx is produced.

Could also be why imports run 180. Less NOx.

And that. Is what's taught in emissions classes. Or was.

When I took it. It was mostly centered around Cali's smog problem.

 

[HL66]

currently we have a big NOx and particle discussion in Europe.... on Diesel engines EGR is mainly used to reduce NOx… high EGR rates reduce NOx but increase soot particle emissions… so this has to be balanced… as converters do not fully convert NOx, they add DEF fluid to chemically reduce NOx.. on gasoline engines EGR is used to reduce fuel consumption in low and medium load conditions..EGR generally reduces combustion temperatures. On gasoline engines it is possible to do Internal EGR with the VVT system. Reduced combustion chamber temperatures also mean less tendency to knock. Downside of EGR can be driveability issues and oil contamination. Reducing emissions of the raw exhaust is always preferred over using expensive components for aftertreatment