When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
What does the enhanced cooling of the Z51 package include?
On my C6 Z51 (m6), GM put an external oil cooler, without a thermostatic control. The result is the oil takes forever to warm up in cold weather. If there is external oil cooling on the C8, has GM cured that short that design shortfall?
What does the enhanced cooling of the Z51 package include?
On my C6 Z51 (m6), GM put an external oil cooler, without a thermostatic control. The result is the oil takes forever to warm up in cold weather. If there is external oil cooling on the C8, has GM cured that short that design shortfall?
Not sure on the C8, but the later model C6Z06s circulates the oil through the radiator to help warm it when cold and cool it when hot.
What does the enhanced cooling of the Z51 package include?
On my C6 Z51 (m6), GM put an external oil cooler, without a thermostatic control. The result is the oil takes forever to warm up in cold weather. If there is external oil cooling on the C8, has GM cured that short that design shortfall?
Had an 09 Z06 that had the external (air to oil) oil cooler, had to cover it in the winter to get the oil up to temp. In 2010 (if memory is correct) GM changed the oil cooler to a water (coolant) to oil heat exchanger. It uses engine coolant exiting the block (hot) to warm the oil faster on cold startup. It would also keep the oil from getting too hot when driven at 7/10ths, but wasn't very good at keeping the C7Z06 oil temp low enough when tracked on a road course on a hot day.
The additional C8 Z51 radiator cools the engine coolant after it passes through the front mounted radiators. Tadge stated that the additional (3rd) Z51 radiator "super cools" the coolant (gets the coolant closer to ambient temp). The "super cooled" coolant then flows through another water to oil heat exchanger that cools the DCT (DCT and LSD/ELSD share oil, so it cools both). I guess they realized they needed the extra cooling for the DCT/LSD when driven hard while they were testing/developing the C8.
The LT2 uses the same type of oil to water heat exchanger that the late C6/Dry sump engines used and the C7 Dry sump engines used. So oil warm up will not be an issue. I thing the driving factor for GMs change to oil to water oil cooling was to improve gas mileage on cold starts.
Had an 09 Z06 that had the external (air to oil) oil cooler, had to cover it in the winter to get the oil up to temp. In 2010 (if memory is correct) GM changed the oil cooler to a water (coolant) to oil heat exchanger. It uses engine coolant exiting the block (hot) to warm the oil faster on cold startup. It would also keep the oil from getting too hot when driven at 7/10ths, but wasn't very good at keeping the C7Z06 oil temp low enough when tracked on a road course on a hot day.
The additional C8 Z51 radiator cools the engine coolant after it passes through the front mounted radiators. Tadge stated that the additional (3rd) Z51 radiator "super cools" the coolant (gets the coolant closer to ambient temp). The "super cooled" coolant then flows through another water to oil heat exchanger that cools the DCT (DCT and LSD/ELSD share oil, so it cools both). I guess they realized they needed the extra cooling for the DCT/LSD when driven hard while they were testing/developing the C8.
The LT2 uses the same type of oil to water heat exchanger that the late C6/Dry sump engines used and the C7 Dry sump engines used. So oil warm up will not be an issue. I thing the driving factor for GMs change to oil to water oil cooling was to improve gas mileage on cold starts.
The C6ZR1 was the first to switch in 2009 and then the C6Z06 in 2010, but what’s strange to me is the dry sump Grand Sport still has the external oil cooler. My coolant hit 250 and oil was only 285 at COTA in 95*, in C5 with no oil cooler I could hit 300* oil and only be at 220* coolant at 80* ambient. Oil runs too cool in the winter on GS for the street though as you mentioned, barely gets to 130* which is what I like to see before getting on it.
I've thought wrapping my cooler for the winter too.
I forgot about the cooling needs for the transmission. what's the ideal temp for a DCT? I put an external cooler on my Camaro when I put a high stall in it. IIRC, the ideal temp (160 - 180*) was much lower than ideal engine oil .
Last edited by Ragtop 99; Nov 2, 2019 at 06:49 PM.
The third radiator on the Z51 is used to cool the transaxle and eLSD. Per a GM seminar at Carlisle, the coolant from the front radiators is branched off before reaching the engine, to the 3rd radiator, which feeds the transaxle, and is then routed back through the main coolant system. The 3rd radiator doesn't directly cool the engine at all, but by off-loading the heat from the transaxle to a third radiator it keeps the coolant the engine sees cooler.
I've thought wrapping my cooler for the winter too.
I forgot about the cooling needs for the transmission. what's the ideal temp for a DCT? I put an external cooler on my Camaro when I put a high stall in it. IIRC, the ideal temp (160 - 180*) was much lower than ideal engine oil .
Lots of cooling. These are some pics:
Z51 added Liquid/Air heat exchanger. Coolant from front rads gets extra cool and goes to DCT Heat Exchanger and Engine:
Liquid/Liquid DCT Heat Exchanger
LT2 Liquid Engine Coolant/Liquid Engine Oil Heat Exchanger- Similar to LT1 BUT Larger
The third radiator on the Z51 is used to cool the transaxle and eLSD. Per a GM seminar at Carlisle, the coolant from the front radiators is branched off before reaching the engine, to the 3rd radiator, which feeds the transaxle, and is then routed back through the main coolant system. The 3rd radiator doesn't directly cool the engine at all, but by off-loading the heat from the transaxle to a third radiator it keeps the coolant the engine sees cooler.
Technically all 3 radiators are in series and all cooling the entire thermal load of the driveline: engine & transaxle combined.
To the OP the Z51 adds a 3rd radiator in the passenger side intake... it's in series with the other two.
Z51 added Liquid/Air heat exchanger. Coolant from front rads gets extra cool and goes to DCT Heat Exchanger and Engine:
That's the driver side.... that is only a fan used to push air through the engine compartment to keep engine bay cool in summer traffic. Front engine cars have the radiator fan to blow air over the engine whereas a ME car doesn't. The Z51 radiator is on the other side. Base cars have fans on each side.
I know that GM does a lot of testing In hot climates. My concern is that all of hot weather testing was done in low humidity environments. They also should have tested in high heat and high humidity conditions like South Florida (Sebring Race Track) in June through August. I asked Chevy engineers about this after the C7’s started showing their over heating problems. They told me that they did not test in high heat / high humidity 98 degrees and 95% humidity conditions. There were early pictures of the C8-R testing at Sebring at night but I did not see regular C8 testing down in South Florida.
I know that GM does a lot of testing In hot climates. My concern is that all of hot weather testing was done in low humidity environments. They also should have tested in high heat and high humidity conditions like South Florida (Sebring Race Track) in June through August. I asked Chevy engineers about this after the C7’s started showing their over heating problems. They told me that they did not test in high heat / high humidity 98 degrees and 95% humidity conditions. There were early pictures of the C8-R testing at Sebring at night but I did not see regular C8 testing down in South Florida.
Friday, I asked the engineer accompanying the C8 displayed at the Rolex 24 if the car had been tested and could run a Sebring 30 minute DE in summer conditions without problems (overheating, limp mode, etc.). He didn’t know but wrote himself a note and promised to have an answer for me before the end of the race.
When I caught up with him Saturday he had an answer: “No the production car had not been tested at Sebring summer DE conditions, but based on other testing that has been done it is believed that the car can handle the conditions outlined”.
I know that GM does a lot of testing In hot climates. My concern is that all of hot weather testing was done in low humidity environments. They also should have tested in high heat and high humidity conditions like South Florida (Sebring Race Track) in June through August. I asked Chevy engineers about this after the C7’s started showing their over heating problems. They told me that they did not test in high heat / high humidity 98 degrees and 95% humidity conditions. There were early pictures of the C8-R testing at Sebring at night but I did not see regular C8 testing down in South Florida.
SAE paper said Z51 validated on track at 100 degree ambient temps with pro-level driver for 30+ minutes of use. I don’t suspect any issues at all. I had none TTing my C7 Z51 at VIR in high 90s.
I know that GM does a lot of testing In hot climates. My concern is that all of hot weather testing was done in low humidity environments. They also should have tested in high heat and high humidity conditions like South Florida (Sebring Race Track) in June through August. I asked Chevy engineers about this after the C7’s started showing their over heating problems. They told me that they did not test in high heat / high humidity 98 degrees and 95% humidity conditions. There were early pictures of the C8-R testing at Sebring at night but I did not see regular C8 testing down in South Florida.
While humid air has slightly less heat capacity than dry air it also has less oxygen for combustion (less heat into the engine) so I'd expect any differences cooling to be noise level on a NA engine.
While humid air has slightly less heat capacity than dry air
Wait, what? Humid air has greater heat capacity than dry air.
Water has way higher heat capacity, humid air contains more water than dry air; Thus humid air will cool or heat faster (exchange will be faster).
Engine oil has around 215-220*F, so 110*F in Florida anyway will be cooling. 110*F dry is, in theory, worse than 110*F humid, but in reality while car is going 100mph or more, heat exchange is so fast that this ~2% of heat capacity difference (dry vs humid) doesn't matter.
And point about lower amount of oxygen in humid air is valid, so as it was pointed, in theory, combustion will be calmer...
Wait, what? Humid air has greater heat capacity than dry air.
Water has way higher heat capacity, humid air contains more water than dry air; Thus humid air will cool or heat faster (exchange will be faster).
Engine oil has around 215-220*F, so 110*F in Florida anyway will be cooling. 110*F dry is, in theory, worse than 110*F humid, but in reality while car is going 100mph or more, heat exchange is so fast that this ~2% of heat capacity difference (dry vs humid) doesn't matter.
And point about lower amount of oxygen in humid air is valid, so as it was pointed, in theory, combustion will be calmer...
Sorry, a little bit of a brain fart. I said heat capacity and meant thermal conductivity. That is what I get for doing this from memory. I searched online and couldn't find the chart I was thinking of (I believe in a reference book for a job I was doing years ago). But here is an article with a similar chart: https://www.electronics-cooling.com/...-of-moist-air/
^^^ Yep, when looking at the weight of the DCT versus the C7 M7 have to remember the M7 Trans cooler was a separate air to fluid cooler with a fan and the eLSD hydrilic pump included an electric motor with valves, hoses etc all separate from the Trans. With the DCT it's all together. That liquid/liquid heat exchanger is also more efficient than air/liquid.
Someone pointed out that the Z51 extra air/fluid cooler is on the other side of the car and what I showed was just the fan blowing air through the hot engine compartment when it gets too hot.
Z51 enhanced cooling
Yep, when looking at the weight of the DCT versus the C7 M7 have to remember the M7 Trans cooler was a separate air to fluid cooler with a fan and the eLSD hydrilic pump included an electric motor with valves, hoses etc all separate from the Trans. With the DCT it's all together. That liquid/liquid heat exchanger is also more efficient than air/liquid.