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Has anyone installed or heard about these air deflectors that get installed on the underside of the engine bay using the existing wind screens bolts. I watched a video from horsepower obsessed where he showed step by step instructions to install both the left, and right sides.
The really odd thing is that all of the exported C8’s have them already installed as a stock OEM part! Here’s a picture of the GM air deflectors .
As this wasn’t odd enough I went to the parts department at a Chevrolet dealership in my area to order these and was told there’s a two lead time for them which was No surprise but when he plugged in my VIN I was told these wouldn’t fit my C8 Z06, and these couldn’t be returned if I still proceeded to order them. So now I’m really corn-fused because I watched the youtube video, and they fit with no issues so I’m not sure if it’s just for a C8 and not a Z06 which doesn’t make any sense and I wouldn’t be posting this however on the video they also took baseline temp readings and readings after the install and the readings were really a game changer in reducing the temperatures on the engine, headers, and cats between 30to 40 degrees cooler. That’s a significant difference and another reason to have these installed.
Anyway, your input and knowledge in this post would be greatly appreciated.
Thanks
Last edited by Gary0426; Nov 21, 2025 at 01:00 PM.
I have some on order. When they get here I will do a back to back test verify the temperature drop.
The temp numbers from HPobsessed seem pretty big.
I will be impressed if they make that much difference.
Has anyone installed or heard about these air deflectors that get installed on the underside of the engine bay using the existing wind screens bolts. I watched a video from horsepower obsessed where he showed step by step instructions to install both the left, and right sides.
The really odd thing is that all of the exported C8’s have them already installed as a stock OEM part! Here’s a picture of the GM air deflectors .
As this wasn’t odd enough I went to the parts department at a Chevrolet dealership in my area to order these and was told there’s a two lead time for them which was No surprise but when he plugged in my VIN I was told these wouldn’t fit my C8 Z06, and these couldn’t be returned if I still proceeded to order them. So now I’m really corn-fused because I watched the youtube video, and they fit with no issues so I’m not sure if it’s just for a C8 and not a Z06 which doesn’t make any sense and I wouldn’t be posting this however on the video they also took baseline temp readings and readings after the install and the readings were really a game changer in reducing the temperatures on the engine, headers, and cats between 30to 40 degrees cooler. That’s a significant difference and another reason to have these installed.
Anyway, your input and knowledge in this post would be greatly appreciated.
Thanks
likely don’t have in the states due to emissions standards and acoustic certification . Extra cooldown affects the EPA hot soak evaporative emissions and noise escaping engine bay(would possibly require recertify ing which can cost millions). Shipped overseas as standard due European heat management requirements. Rear aero balance being only negative but low effect(maybe some increased dirt into engine bay). This is a synopsis from AI. I tested some replicas and found a 10 percent reduction in temperatures in the engine bay (using oem engine compartment temperature sensors)w my headers seeing up to 30-40 degrees drop at a 60 mph sustained test. Higher mph likely to yield even more.
I have a buddy that’s going to test on his HTC soon since mine is a coupe and see how well they work on his car vs coupe doing the same test.
I wonder about the role of the cooling fans in all of this. The front fans which blow air through the cooling system radiators respond to cooling system temperature and also the AC on/off status, according to the Service Manual. The engine compartment cooling fans respond to a temperature sensor in the engine bay to control engine compartment temperature. All C8s have all of those fans. The Z51 has the extra radiator in the back. The V09 options for Middle East bound cars has another radiator on the other side in back as well. I do not know if the German spec cars, which have these extra deflectors, also have the V09 option ( I think not). Those extra radiators are of course for engine cooling. These extra deflectors will force more air into the engine compartment (in addition to all that air already coming in from the side scoops. I wonder if the extra deflectors are directing the air to a specific component in the engine compartment - I've seen an explanation on this forum that it has something to do with extra heat due to particulate filters - but I do not know if that is accurate or just speculation.
I have some on order. When they get here I will do a back to back test verify the temperature drop.
The temp numbers from HPobsessed seem pretty big.
I will be impressed if they make that much difference.
What I'd be curious about is engine compartment temperatures at idle and stop and go traffic vs driving down the highway/freeway without the scoops on a hot day. I wouldn't be surprised if the engine compartment temperatures are as hot or hotter in stop and go traffic than they are driving down the freeway. And then the same comparison with the scoops. So if you do a lot of driving in traffic the scoops may not be doing any good the majority of the time. And if the engine bay temperatures are hotter in stop and go traffic then you're not providing cooling when it needs it the most.
Another thing to consider is the scoops appear to block about 20% (guestimate from the pictures) of the opening. If a significant amount of air is drawn in the bottom openings due to convection when stopped or driving slow with the fan on then the engine bay temperatures may increase when the scoops are installed.
What I'd be curious about is engine compartment temperatures at idle and stop and go traffic vs driving down the highway/freeway without the scoops on a hot day. I wouldn't be surprised if the engine compartment temperatures are as hot or hotter in stop and go traffic than they are driving down the freeway. And then the same comparison with the scoops. So if you do a lot of driving in traffic the scoops may not be doing any good the majority of the time. And if the engine bay temperatures are hotter in stop and go traffic then you're not providing cooling when it needs it the most.
Another thing to consider is the scoops appear to block about 20% (guestimate from the pictures) of the opening. If a significant amount of air is drawn in the bottom openings due to convection when stopped or driving slow with the fan on then the engine bay temperatures may increase when the scoops are installed.
And, of course, there are those giant powerful fans in the back that respond to a temperature sensor in the engine bay according to the Service Manual. The certainly will come on in stop and go traffic. Do they also come on when rolling along at 100 mph, or is the airflow from the scoops always enough to keep the engine bay temperature below the threshold for fan operation?
And with the addition of the deflectors, when temperatures are being measured, are the fans behaving differently? I would be interested in knowing how the addition of the deflectors affects the cycling of the fans.
All very good points but I believe we all know that unless the seller’s have them independently tested we’ll never know those answers unfortunately.
i might take that chance and purchase the 3D printed ones from dynamic caps since the price on them is relatively inexpensive and pay attention to all of the good points made by everyone.
All very good points but I believe we all know that unless the seller’s have them independently tested we’ll never know those answers unfortunately.
i might take that chance and purchase the 3D printed ones from dynamic caps since the price on them is relatively inexpensive and pay attention to all of the good points made by everyone.
Yes. We know that GM puts them on the German spec cars, so,we know they do something. I'd like to know what. I don't think they will hurt anything.
There's lots of stuff in the engine bay that will eventually be aged by heat - so cooler engine bay temperatures seems to be an ok objective, if that is what they are for.
I'm curious about the reported engine coolant temperature reductions that some report. How does that happen, since the cooling system temps are thermostatically regulated. Is the cooling system already operating at maximum capacity? Again, we know that as the heat load increases the thermostats will open more, and eventually the fans will come on - the ones in front respond to coolant temps and also to AC status (I think pressure). I assume that when the lower temperature are observed its still within the normal operating range for the cooling system.
Yes. We know that GM puts them on the German spec cars, so,we know they do something. I'd like to know what. I don't think they will hurt anything.
There's lots of stuff in the engine bay that will eventually be aged by heat - so cooler engine bay temperatures seems to be an ok objective, if that is what they are for.
I'm curious about the reported engine coolant temperature reductions that some report. How does that happen, since the cooling system temps are thermostatically regulated. Is the cooling system already operating at maximum capacity? Again, we know that as the heat load increases the thermostats will open more, and eventually the fans will come on - the ones in front respond to coolant temps and also to AC status (I think pressure). I assume that when the lower temperature are observed its still within the normal operating range for the cooling system.
There are two main differences for German cars.
They have access to the Autobahn where they can legally drive for long periods at WOT or close to it.
They have GPF filters in the exhaust that are similar to catalytic converters in that they run hot during regeneration.
Both of these items probably benefit from having the scoops installed. However the scoops my increase engine bay temperatures in very low speed conditions.
They have access to the Autobahn where they can legally drive for long periods at WOT or close to it.
They have GPF filters in the exhaust that are similar to catalytic converters in that they run hot during regeneration.
Both of these items probably benefit from having the scoops installed. However the scoops my increase engine bay temperatures in very low speed conditions.
I notice they have a curved deflector that extends into the opening which from its shape would appear to direct the air toward the front of the engine bay. I'm wondering if that directs air on a specific component, such as the GPF filters. I also wonder which way air flows through those openings without the deflectors, when the car is moving or the fans are on. I would think that generally there would be positive air pressure in the engine compartment, so that when moving or with the fans on, air would flow out of those opening, rather than in. With the deflectors, air flows in when moving, but I bet when not moving, with the fans on, air will still flow out of those openings. Not moving, with fans off, convection will likely draw air into those opening, like you suggest, as hot air flow out of the higher vents. The deflectors will block that some, but the fans can still kick on to compensate, I suppose. All speculation. I suppose GM engineered all this to work together. Its a good question for the next Bash.
Great pictures.
What are these installed on a C8, Z51 or Z06?
Im asking because I tried purchasing them online at GM Direct Parts, and they emailed me back before shipping them out to me stating that they won’t fit my C8 Z06 and they are a non-returnable part.
thanks,
I notice they have a curved deflector that extends into the opening which from its shape would appear to direct the air toward the front of the engine bay. I'm wondering if that directs air on a specific component, such as the GPF filters. I also wonder which way air flows through those openings without the deflectors, when the car is moving or the fans are on. I would think that generally there would be positive air pressure in the engine compartment, so that when moving or with the fans on, air would flow out of those opening, rather than in. With the deflectors, air flows in when moving, but I bet when not moving, with the fans on, air will still flow out of those openings. Not moving, with fans off, convection will likely draw air into those opening, like you suggest, as hot air flow out of the higher vents. The deflectors will block that some, but the fans can still kick on to compensate, I suppose. All speculation. I suppose GM engineered all this to work together. Its a good question for the next Bash.
The GPF filters would be behind the catalytic converters.
We don't know the specifics of how the engine bay ventilation works, that's why it would be good to do some testing. But it is possible that the cooling fans would actually create a lower pressure area at the bottom inlets sort of like a venturi causing more air to be drawn through them when the fans are running. As more air is drawn into the engine compartment there would be more air exiting the top vents because of convection due to the hot engine (sort of like a wood stove chimney or a jet pump). This could create a lower pressure area at the bottom inlets than if the fans weren't running.
I spoke to David at Dynamic Caps which is the company offering the 3D printed deflectors and he’s sending me a set of them so I can test fit and see how these cool the temps in a Z06 engine bay.
I’ll try and answer some of everyone’s questions as far as the fans are concerned in turning on/off with temperature readings before and after the installation.
For every one’s input.
I spoke to David at Dynamic Caps which is the company offering the 3D printed deflectors and he’s sending me a set of them so I can test fit and see how these cool the temps in a Z06 engine bay.
I’ll try and answer some of everyone’s questions as far as the fans are concerned in turning on/off with temperature readings before and after the installation.
For every one’s input.
It would be important to test on a hot day since you are concerned about peak temperatures. You can't necessarily correlate cold day temperature results with hot day temperatures.
Absolutely, and living in Florida should give us those readings but unfortunately since it’s not in the heat of the summer with humidity readings reaching over the outside temperatures so I can obviously only give the readings with the temperatures I have to work with.
And (it seems obvious I suppose) the goal is to make the engine bay or some component in the engine bay cooler, right?
Is it supposed to make engine coolant cooler too?
The V09 opton on the MIddle East bound cars adds another radiator for engine cooling. That, by the way, might actually make the engine bay hottor since all of the cooling air flowing into the engine bay flows over the radiators first.
But are the deflectors also part of the MIddle East Spec? Is V09 part of the German spec car?
I'm wondering if these two options occur at the same time.
C8 air deflectors
