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I've followed all the threads on the C8's displayed water temperature. Most roughly 180 +/-. Many factors in those discussions. Reason for this thread is that I thought that the old days of 180 were no more due to higher Temps required to meet epa output. 205 +/- for most vehicles.
What triggered this is that my 2017 RV with a 2016 ford 6.8L V10 engine runs at 229F as SOP summer interstate driving. Winter and slower (<70mph) lower Temps- I think.
How does the C8 meet the requirements with a 180F operating temperature?
Moving the cats closer to the engine, inside the engine bay, helped meet emissions. What likely matters for emissions is exhaust gas temp and how quickly you can get the cat up to operating temp. My wife's 2021 Jeep turbo typically runs in the 170's as well and has the cat immediately downstream from the turbine housing.
It's rare that mine gets up to 170. I'll check it now that the weather is warmer, but this particular car seem to run cooler than others I've heard about. Makes it a bitch to get warm enough to check the oil. I've driven for well over a half hour down the freeway and still not up to 170, even if I run it in 3rd or 4th gear. To get it up to 175 I have to run it for at least 15 minutes, THEN get into stop and go traffic.
It's rare that mine gets up to 170. I'll check it now that the weather is warmer, but this particular car seem to run cooler than others I've heard about. Makes it a bitch to get warm enough to check the oil. I've driven for well over a half hour down the freeway and still not up to 170, even if I run it in 3rd or 4th gear. To get it up to 175 I have to run it for at least 15 minutes, THEN get into stop and go traffic.
Yeah, I see the manual does say check when its at least 175 degrees. I does not appear to make clear if it is water temperature, or oil temperature. Just an observation, don't know if it has any significance.
It takes a minimum of 5 miles / 10 minutes for my C8 to reach 160 oil 180ish water in the Florida summer. I have and think that the Z51 package is the reason. I don't know if the non Z51s take that long.
It takes a minimum of 5 miles / 10 minutes for my C8 to reach 160 oil 180ish water in the Florida summer. I have and think that the Z51 package is the reason. I don't know if the non Z51s take that long.
FWIW, I have Coolant, Engine Oil and DCT temps displayed on the left of the dash.
Typically, mine in winter is ~176 and all three about the same. In summer Coolant may get to ~185 and the other two low 180's. To answer your question, DI and CAT location is why it can get be that low and meet EPA emissions.
IMO it's lower because they pushed the HP from my C7's up 30 hp with similar cam timing and a few intake and exhaust flow tricks. An old Hot Rod trick was to use a low temp thermostat to run more timing advance (avoiding detonation) and gain power. Recall the Hypertech Programmer I use in my V6 S-10 suggested a 160 F thermostat! Was OK but would occasionally trip a CEL (Coolant too cold) and I used my OBD device to cancel!
The LT2 with 495 hp has pushed the timing (and probably the richer fuel/air mixture) as far as they can to avoid detonation. So you need 93 octane to get max power, 91 octane reduces power (probably pulling some timing) and 87 octane is warned can harm the engine. In the C7s LT1 could use 91 octane and if needed 87 octane was acceptable (no doubt also pulling timing that would cut power.) BUT you can only do so much with timing etc until you run out of what can be accomplished.
........you need 93 octane to get max power, 91 octane reduces power (probably pulling some timing)......
I agree. But the 2023 Owner's Manual says 91 Octane is required, and the "reduced power" wording found in the earlier manuals has been deleted. But....in the section on tracking, the 2023 Manual continues to say that 93 octane if required. While I agree with what you said, the manual no longer specifically says the power is reduced when using 91 octane.
^^^
Yep, recall that changed wording BUT IMO the 2023 Owner's Manual had new editor (who caused a number word changes!) And did they just say 91 is required to make the many buyer's in CA (and some other places) feel better!? Could be so since nothing was said on how they magically changed the situation. I'll stick with my 2020, 2021 and 2022 LT2 statement! We'll see if they ever say just what the situation is, reduced power or not!
^^^
Yep, recall that changed wording BUT IMO the 2023 Owner's Manual had new editor (who caused a number word changes!) And did they just say 91 is required to make the many buyer's in CA (and some other places) feel better!? Could be so since nothing was said on how they magically changed the situation. I'll stick with my 2020, 2021 and 2022 LT2 statement! We'll see if they ever say just what the situation is, reduced power or not!
They did make some "minor" engine modification that was said to be related to emissions standards or maybe fuel mileage - I can't find that info right now. But some have attributed the change (from 93 is required but 91 is ok at reduced power if 93 is not avialable to 91 is required, but for tracking 93 is required) to that modification. I have not seen any specific evidence to support the connection. I also think that some may have overlooked the fact that in the track section, the 2023 manual still says 93 is required. When emissions and fuel consumption are evaluated by the EPA, is the octane required a factor in whether or not vehicle (or vehicle fleet) meets the standards? Seems to me that as a practical matter both the new and older manuals allow 91 octane, but suggest an advantage to using 93 octane. The wording change, however, may mean that more owners will start to use 91 octane.
^^^
Around here and I thought in most of the country you don’t have a choice. It comes piped from Gulf Coast refineries as 87 or 93 octane and many pumps mix the two and around here it’s usually, 87, 89, or 93. All but Sam’s Club who only have two, 87 and 93.
Now the wife’s BMW SUV requires only 91. So since we use Sam’s 93 octane it’s typically $0.50/gallon cheaper. Even $0.20 less the Buc-ees who just came to town with 125 gas pumps!
Sofor her car if we’re shopping at Sam’s I’ll pull in for gas with a little over half a tank and use 87 octane and mix my own in her tank! *
Frankly usually fill both cars when ~half full. I always fill the Vette with 93 octane.
There are three separate thermostats in the cooling system
Originally Posted by C8J
.......How does the C8 meet the requirements with a 180F operating temperature?
I don't know the answer that (the service manual mentions a 176 degree thermostat) - but I during discussions of operating temperature, owners report numbers all over the place, which we attribute to different ambient temps and different driving conditions. Still I was kind of surprised to the the fluctuations, given that the cooling systems generally have excess capacity and so it should be possible to regulate the operating temperature and keep it near a target value. I was thinking that maybe there were computer controlled thermostats (there are not). I looked in the 2020 Service Manual, and it turns out that the car has no less than 3 different "Engine Coolant Thermostats". 1) Auxiliary Radiator Inlet Hose to Auxiliary Radiator Inlet Hose, 2) "At Engine Coolant Manifold", and 3) Radiator Inlet Hose to Auxiliary Radiator Inlet Pipe (with V09). V08 is a code for Heavy Duty Cooling System. I could not find anything for code V09. These three are self contained thermostats with no external electrical nor vacuum connections, so no computer control. The computer does control the activation of the fans - as we know. Anyway - I thought the fact that there are three thermostats might be of interest.
1) Auxiliary Radiator Inlet Hose to Auxiliary Radiator Inlet Hose
2) "At Engine Coolant Manifold"
3) Radiator Inlet Hose to Auxiliary Radiator Inlet Pipe (with V09) (V09 is as written in the manual - cant find that code - V08 is heavy duty cooling
Ha. Actually there are at least three temperature gauges measuring engine coolant temperature in various places.. Radiator Outlet Hose, Engine Coolant Temperature Sensor, and Oil Cooler Outlet. I believe the oil cooler is a heat exchanger between the engine oil and the engine coolant, and this last one measures the temperature of the engine coolant that is exiting the oil cooler. There is wording that suggest to me that the engine coolant temperature gauge is reading only one of these (though its not entirely clear) - the one called Engine Coolant Temperature Sensor but not certain. I was just looking for anything that summarized the overall strategy for engine temperature management that might provide a clue about the target temperature and target for variations. Did not find that.
Engine Coolant Temperature Sensor
Engine Coolant Temperature Sensor Replacement - Radiator Outlet Hose
^^^
Yep, recall that changed wording BUT IMO the 2023 Owner's Manual had new editor (who caused a number word changes!) And did they just say 91 is required to make the many buyer's in CA (and some other places) feel better!? Could be so since nothing was said on how they magically changed the situation. I'll stick with my 2020, 2021 and 2022 LT2 statement! We'll see if they ever say just what the situation is, reduced power or not!
The C8 is marketed as a track capable car thus they needed to make sure the car can perform on the track using 93 octane. It would be interesting to see how much the C8 pulls timing on the track on 93 octane, perhaps even higher octane would help on the track.
A C8 Z51 engine won't come close to the engine temperatures encountered on the track even during spirited driving on the street. It also would be interesting to see how often timing is pulled on 91 octane during street driving. This could be monitored using an OBD tool (or perhaps even Cosworth Toolbox?). I suspect that there aren't many times that timing is pulled when running 91 octane on the street where 93 octane would have made a difference.
The C8 is marketed as a track capable car thus they needed to make sure the car can perform on the track using 93 octane. It would be interesting to see how much the C8 pulls timing on the track on 93 octane, perhaps even higher octane would help on the track.
A C8 Z51 engine won't come close to the engine temperatures encountered on the track even during spirited driving on the street. It also would be interesting to see how often timing is pulled on 91 octane during street driving. This could be monitored using an OBD tool (or perhaps even Cosworth Toolbox?). I suspect that there aren't many times that timing is pulled when running 91 octane on the street where 93 octane would have made a difference.
Yep, perhaps with higher track temps with 91 octane the timing, air/fuel ration MAP isn't sufficient to pull enough timing to prevent detonation. Would be hard to hear as there are many knock sensors. When any is detected, they first reduce ignition advance, then richen the fuel air mixture. At some point you get a CEL telling you to "BOX BOX" (F1 term! )
The C8 is marketed as a track capable car thus they needed to make sure the car can perform on the track using 93 octane. It would be interesting to see how much the C8 pulls timing on the track on 93 octane, perhaps even higher octane would help on the track.
A C8 Z51 engine won't come close to the engine temperatures encountered on the track even during spirited driving on the street. It also would be interesting to see how often timing is pulled on 91 octane during street driving. This could be monitored using an OBD tool (or perhaps even Cosworth Toolbox?). I suspect that there aren't many times that timing is pulled when running 91 octane on the street where 93 octane would have made a difference.
The 2020 service manual says "if the control module has determined that knock is present, it will retard the ignition timing in an attempt to eliminate the knock. It will always try to work its way back to zero compensation level, or no spark retard. " This implies a couple of things. 1) there is a target timing setting - and that setting is the maximum advance (0 compensation). 2) To "work its way back", it must reduce the compensation until it either reaches the target ignition setting, or knock is occurs, than back off again (and again..). Are we running with a slight amount of knock all the time? Or, does it periodically test for that at a slower rate - say every 5 minutes. I have found nothing in the manual that describes that process in more detail.
Engine coolant temperature
Could be so since nothing was said on how they magically changed the situation. I'll stick with my 2020, 2021 and 2022 LT2 statement! We'll see if they ever say just what the situation is, reduced power or not!
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