Coupe Engine Bay Temperature

[lewma]

All

Wondering what other coupe owners have done regarding engine bay temperature management. Took the car for 100+ mile highway drive today. I have a GM427LS engine in there was was running around 192F on the highway then would get to to 203F when I'm stopped at lights. Fans come on ok and keep the engine itself cool.

The problem is that the engine bay is very hot. I've seen some coupe owners install vents in the hood. Is that the most effective way of getting the temperatures down ? Adding vents to an already painted car would be challenging. Any other tricks ?

thanks!
mark

[Rsnake]

Hello Mark,

Great chatting the other day and looking forward to May. Now on to your question, Dave has done some under hood temp monitoring and it wasn't bad at all. He then cut holes in the hood and the temps didn't change so I think it's a waste.
As for coolant temps, my coyote does the same thing. Anything under 20mph and the temps climb but the fan keeps it In check. Sounds normal to me. I would say to proceed onto other things in preparation for May.

[lewma]

Hey Greg. Great chatting to you. Looking forward to May!

This may have been covered elsewhere but where does the engine heat escape to? Seems like it would be trapped under the hood with nowhere to go? The engine itself seems to be running fine within temperature range, it's just the residual heat building up around it

Mark

[Skuzzy]

I would think the hood vents would help evacuate the hot air, via convection, when the car is moving slowly or stopped. Should help prevent heat soak when it is shut off. I could be way off though. It is something I am going to work on once I get my car rolling.

[Rsnake]

Dave did take underhood temps and hopefully he jumps into this thread as he has more details.
I think a lot of heat goes under the car but just a wag

[Dave Tabor]

Hey all,

My deal was two-fold: one, that that the underhood temps get hot when stopped, like after a track session - temps would be so high as to melt stuff like the accelerator cable housing - leading to a sticky cable - scary. Two, high sustained speed rally speeds - afterwards it smells like everything under the hood is cooking.

I put yarn strands all over the hood and drove on the highway - the airflow is laminar on most of the hood. So, I cut openings on each side of the domed part and added louvers to extract air - louvers that stick up in the air stream. Highway driving with yarn showed that even with louvers that air is not extracted but sucked down through the louvers - what a surprise.

Air pressure under the car must be lower than on the top of the hood.

I decided to make my own dimple-die panels with 4 big holes (2") to use instead of the louvers - since air is going to be sucked down anyway.

I don't remember what the effect on temps was but I think it was minimal. What I can do is drive the car with the vent holes open and then taped over and record the temps. I don't think that highway driving is going to show much difference.

Dave
Gen III #17
FRPP 302, TKO600, 3:15 IRS.

[Skuzzy]

I do not think the hood vents would work at speed, unless you created a low pressure area in front of the vents with an air dam of sorts. It should improve the effectiveness, but still not be all that effective. That said, they should work when stopped or at very low speed. Hot air does want to rise.

[lewma]

Hey all,

My deal was two-fold: one, that that the underhood temps get hot when stopped, like after a track session - temps would be so high as to melt stuff like the accelerator cable housing - leading to a sticky cable - scary. Two, high sustained speed rally speeds - afterwards it smells like everything under the hood is cooking.

I put yarn strands all over the hood and drove on the highway - the airflow is laminar on most of the hood. So, I cut openings on each side of the domed part and added louvers to extract air - louvers that stick up in the air stream. Highway driving with yarn showed that even with louvers that air is not extracted but sucked down through the louvers - what a surprise.

Air pressure under the car must be lower than on the top of the hood.

I decided to make my own dimple-die panels with 4 big holes (2") to use instead of the louvers - since air is going to be sucked down anyway.

I don't remember what the effect on temps was but I think it was minimal. What I can do is drive the car with the vent holes open and then taped over and record the temps. I don't think that highway driving is going to show much difference.

Dave
Gen III #17
FRPP 302, TKO600, 3:15 IRS.

Dave, thanks for the information. I'm going to start measuring my engine bay temps just for my own information to see how high they get. I've done a few 100 mile drives in the recent weeks but yesterday was mainly highway and it was definitely hotter when I got it home.

mark

[nick729]

I would have a look at increasing air flow into the engine bay similar to something like brake disc cooling ducts that some performance cars use. This was the first thing that popped into my mind when assembling the coupe, that all the air that passes through the radiator is then directed out from the top of the hood and none of it goes into the engine compartment and therefore there is little to no circulation there to dissipate the heat from the engine/headers/exhaust.

Not sure how much of the air goes into the engine from the bottom of the frame, since that is pretty much the only place i can see it making into the engine bay.

I might be dead wrong on this though, just my 2 cents.

Nick

[lewma]

Perhaps the hood scoop that's over the driver side wing should be made functional, rather than aesthetic ? Has any coupe owner done this ?

Found these pics:
https://www.flickr.com/photos/511030...7655401870351/

[PNWTim]

Perhaps the hood scoop that's over the driver side wing should be made functional, rather than aesthetic ? Has any coupe owner done this ?

Found these pics:
https://www.flickr.com/photos/511030...7655401870351/

So if the forward one is for cooling the footboxes what is the smaller one for? Bit of a mystery.

[Dave Tabor]

Here's what the air flow looks like over the nose:

https://youtu.be/RXNZ-W2TQUI

Dave
Gen III #17

[lewma]

Here's what the air flow looks like over the nose:

https://youtu.be/RXNZ-W2TQUI

Dave
Gen III #17

Dave, based on that video, if I make the larger vent/scoop thats on the driver side wing functional, that should send some air inside the engine bay while moving ?

[lewma]

So if the forward one is for cooling the footboxes what is the smaller one for? Bit of a mystery.

I interpreted that as smaller ones for footboxes, larger one for engine bay ?

UPDATE: Ignore me. Just looked at those pics again. Doesn't make sense to me.

[Bob Brandle]

I installed a pair of custom self-fabricated hood-top vents for my Type-65/Daytona Coupe.
I was just interested in venting hot engine compartment air at low car speeds and at rest.
When I'm driving and come to a stop, I can often see radiant heat waves shimmering above the vents.
I bought and used screening that appeared to be what Factory Five uses for the rectangular side vents to maintain design consistency.

[lewma]

Thanks Bob. I'm hoping i don't need to cut into the hood on mine. Perhaps I'm over-reacting here but I really didn't like how hot that engine bay was this past weekend. Some of the plastic wrapped wiring close to the headers were beginning to melt. I have ceramic coated headers too.

[Dave Tabor]

Dave, based on that video, if I make the larger vent/scoop thats on the driver side wing functional, that should send some air inside the engine bay while moving ?

I think yes - there is underhood vacuum wanting to pull air into the compartment from the top of the nose.

I basically have what Bob shows below.

I used a Bluetooth 2 channel BBQ thermometer to test a few things. My car is currently down for a new radiator at the present or I'd go out and take some readings.

Dave
Gen III #17

[turbodon]

I cut a series of five 1.5" holes in the back of the radiator aluminum panel in the area under the X crossmember. The holes allowed some air circulation in the engine bay when the radiator fan was on. So in stop and go traffic, there was airflow.

[Rsnake]

I decided to do some research yesterday and have the results on my youtube channel.
I did forget to mention that my Type 65 has been flat bottomed to the middle of the engine
which I would assume would trap more heat so please keep this in mind. Enjoy.
https://youtu.be/0ziZT9Ty6fk?si=O6brDwMq1zHWmDBz

[lewma]

Greg
Great video, lots of good data. I planned on doing the same thing this weekend but I ended up chasing a coolant issue. I deleted my heater core ( never going to need it here ) to clean up the hoses in the engine bay. I capped off one of the heater ports, plumbed in my surge tank on the other port then went for a couple of drives. Engine was way hotter than usual so after reading a few LS websites I discovered that you need to loop the heater ports on this engine, then T in the surge tank too. Corrected all that then the engine is back to normal again. I added a probe to the engine bay ( not as fancy as yours ) and planned on doing a couple of runs but it was too late in the evening. I'll get to that this next weekend.

For reference, I also have a complete seal around the back edge of the hood.

mark

[coyobra]

Hi Mark,

Saw your post and started thinking about solutions. Have you considered a type of blower(s) like in a boat to suck gas vapors (in your case, heat) out of the engine bay? Also, I googled heat wrap for headers to see if it would help with engine bay heat reduction and listed below are the pros and cons:

Yes, heat wrapping headers generally works to reduce underhood temperatures, improve exhaust scavenging, and potentially increase horsepower by maintaining hotter exhaust gases, but it can also lead to accelerated header wear and void warranties.
Here's a more detailed breakdown:
Benefits of Header Wrapping:

Reduced Underhood Temperatures:
Header wraps insulate the headers, preventing heat from radiating into the engine bay and potentially protecting heat-sensitive components.

Improved Exhaust Scavenging:
By keeping the exhaust gases hotter, header wraps can promote better exhaust flow and scavenging, potentially leading to increased power and efficiency.
Reduced Heat Soak:
Wrapping can minimize heat soak, where the engine and other components become overheated due to prolonged heat exposure.
Protection of Underhood Components:
Header wraps can help protect sensitive components like fuel lines, wiring, and other parts from excessive heat.
Potential Performance Gains:
Some claim that header wraps can lead to slight horsepower and fuel efficiency gains due to improved exhaust flow and scavenging.

Potential Drawbacks and Considerations:

Accelerated Header Wear:
The insulation provided by header wraps can trap moisture and heat, potentially leading to accelerated corrosion and premature wear of the headers.

Warranty Issues:
Many header manufacturers will void their warranties if header wrap is installed on their products, as the wrap can contribute to header damage.
Abrasive Nature:
Header wraps are not very abrasion-resistant and can be damaged easily when working on the engine or if they rub against other parts.
Lifespan:
Header wraps typically have a lifespan of a few years and may need to be replaced or re-wrapped periodically.
Exhaust Note:
Wrapping your exhaust may alter the sound of your vehicle's exhaust note.

Alternatives to Header Wrapping:

Ceramic Coating:
Ceramic coating can provide a durable, heat-resistant barrier that can help reduce underhood temperatures without the potential drawbacks of header wraps.

Heat Shields:
Heat shields can also help protect underhood components from excessive heat, but they may not provide the same level of insulation as header wraps.

In summary, while header wrapping can offer some benefits, it's important to weigh the potential drawbacks and consider alternatives like ceramic coating or heat shields.

[lewma]

Hey Dave, great to hear from you! My headers are already ceramic coated and I'm not too sure I want to wrap them at this point. Rsnake posted some good numbers so this next weekend I'll run up/down the I-15 and see where my temps are. Perhaps I'm overreacting here but that engine bay was hot on my last long run.

[coyobra]

Hey Mark! Yeh, these Factory Five's always seem to have a lot of engine bay heat when standing still. My fan goes on at about 180 degrees (coolant temp) and shuts off when it gets below that. Always when sitting at a stop light. I never installed the foam seals between the body and foot boxes in the Cobra, so heat escape has really never been an issue while moving. (obviously air flow from the engine bay will get hot in the cockpit on a hot day, but nice constant heat on a cold day) Still debating if I should install the seals or not. Hope you figure it out!

[Rsnake]

After a little more research online I am now confident with my numbers and I have nothing to worry about.
For your reading pleasure. https://mvfri.org/contracts/Final%20...atures%201.pdf
Thanks
Greg

[lewma]

Greg where on earth did you dig that up from ?

[Rsnake]

A study I did 20+ years ago. Just kidding, Google.

[lewma]

Updates from todays run. Did about 120 miles this morning.

Started with ambient bay temp of 70F. Within a couple of minutes, up to 115F when idling.

ECT = engine coolant temp
IAT = intake air temp ( via MAF sensor )
BAY = engine bay temp. measured right in front of the firewall about 4" from the hood.


When averaging 40mph on back roads, ECT 192F, IAT 75F, Bay 130F
Sitting in traffic, lights. ECT 203F, IAT 80F, Bay 140F
When averaging 75mph on the highway, ECT 194F, IAT 85F, Bay 120F

For me, the engine bay only starts to cool when i'm doing 60mph+. Anything lower, the bay does not cool at all seems to follow engine temp only.

Also discovered that my cooling fan stopped working sometime today too. Bringing it home was hitting 220F. Applied 12V to the fan. Nothing.

Anyone have any recommendations for a RELIABLE fan setup ? This one only has 1K miles.

[Skuzzy]

I like the Flex-a-lite fans. https://www.summitracing.com/parts/flx-105390
Breeze also has a shroud for that fan. https://breezeautomotive.com/shop/ra...r-gen-3-coupe/

[lewma]

I was looking at the same fan. Ordered.

[Rsnake]

Mark, Interesting data for sure. You did say you have the seal between the hood and cowl? If so, try removing it and run the test again as I am interested to see what the temps are.

[Dave Tabor]

Not quite engine bay temps but I was interested in directing cool air to my oil and power steering fluid coolers which are mounted behind/after the radiator.

So I added a NACA duct to the nose. But not before verifying that the air pressure on the outside nose is higher that what is coming out of the radiator output ducting - using a manometer.

Airflow looks like this:

https://youtu.be/QQhkGPrqs-0


Temperature delta between the output of the NACA duct (underhood) and non-ducted side of the hood was 30 degrees F driving on the highway. I'll take it.

Dave
Gen III #17

[lewma]

30F change is great!

I'm going to remove a portion of the seal that I have around the hood. Perhaps that will allow some of the heat to escape.

Another thought was to make that forward scoop on the drivers side wing functional. Punch a hole through the wing to get some air in there too ?

[Dave Tabor]

Sure - I'd give it a try.

Dave

[Jphoenix]

Not quite engine bay temps but I was interested in directing cool air to my oil and power steering fluid coolers which are mounted behind/after the radiator.

So I added a NACA duct to the nose.

Dave
Gen III #17

Dave did you buy the inner duct - or fabricate it? Or is it just the cutout in front of the radiator exit? My oil cooler is in the same location.

[Dave Tabor]

Dave did you buy the inner duct - or fabricate it? Or is it just the cutout in front of the radiator exit? My oil cooler is in the same location.

There is a true inner NACA duct (bought it) for a 3" hose - taped in place for the test but I will glass it in smooth, keeping a sharp outer edge.

I know it's dark (cloudy today) but if you look at the video there is some yarn down in the duct below the nose surface - the duct is black like the stripe so it's hard to see.

I may add a second duct on the other side...but debating as some amount of asymmetry looks cool...

Dave
Gen III #17

[Jphoenix]

Dave, does the 3” hose go to the oil cooler/ps cooler?

[Dave Tabor]

Dave, does the 3” hose go to the oil cooler/ps cooler?

The 3" output from the duct ends up right below my oil cooler with the nose closed - so no need for a hose.

This is what drove the positioning of the duct - mocked up by taping it to the inside of the nose and closing/opening the nose a few times to determine a position that would allow the duct to clear the radiator/shroud and direct air below the oil cooler.

The duct measures about 10"x4". Whether the black or the clear ones in in the photo, the dimensions appear to be the same. I don't remember where I got these but they are pretty standard. 'Butler' is molded into the black one and the clear is Allstar, I think.

Next trick is to glass-in the duct...I have a pair coming from Amazon tomorrow, hopefully matching.

Dave
Gen III #17
nose open 1.jpgnose open 2.jpgducts.jpgnose closed.jpg

[Jphoenix]

Thanks for the photos Dave, it appears you have the same oil cooler arrangement I have, so this is great info. I even have the same Susa cushioned mounts!

[Dave Tabor]

Temperature delta between the output of the NACA duct (underhood) and non-ducted side of the hood was 30 degrees F driving on the highway. I'll take it.

Dave
Gen III #17

To be clear, these temp readings were done at the same time with a dual-probe thermometer - probes on the non-ducted and ducted sides of the nose at the same time - this is where that temperature screenshot came from.

The temps are not 'before and after' installing the duct.

I do not know the ultimate effect on oil temperature but there is a 3" channel of ambient air blowing on the oil cooler. It's interesting that radiator air is not all that hot.

I started with a duct on the driver side because that is where the oil comes into the cooler and is the hottest (but is on the cooler side of the radiator). I'll likely add a second duct on the passenger side.

My heat issue is coming from the Nevada rally runs where the car is doing 140+ for ~25 mins (~5000 rpm, sustained). The oil temps creep up to where the gauge (analog) is not accurate - is it 270/290F? sort of thing. 20 minute track sessions get the oil up to 260+. The temp sensor is in the pan. I don't know what it is going into the oil cooler. I'm using Mobil 1 and oil analyses come back fine.

Dave
Gen III #17

[Namrups]

Dave, What weight Mobil 1 are you using?