Engine bay aero?
 

OK, we all know that the engine bay is very dirty aerodynamically.
In most cars we can't avoid passing some air there.
We also can't make the flow there clean, far from that.

The question is:
Can we make the airflow cleaner than otherwise? Cleaner enough to be worth the effort?

In my car, Honda went through some lengths to direct the air which passes through the radiator, out through the wheel wells rather than the rear of the hood or the bottom of the engine bay. Presumably there was a reason for this, but I have no data or facts to support this.

What let's air out can also let water spray filled with road salt in.

This will corrode the electronics.

However, it may take many years to do this.

Today's electronically dependent cars have design measures to avoid this, most designs over 20 years old do not - in my opinion.

Think twice before you let the devil in.

I definitely get road salt in the engine bay. Thankfully most stuff is aluminum in my car. I've considered making baffles to block spray.

I've been thinking about fabricating something to cover the rear well area to prevent salt from getting in. What's wrong with air exiting underneath the car? Seems like the airflow under the car would keep the exhausted air flow attached.

Unsure. Might make it a high pressure zone? Just a guess.

I don't think I get salt in from the rear/bottom, but the tires throw salt all over the catalyst when turning, which is probably why they rust so badly. I could also see salt affecting the coil packs on the back of the engine.

I used to get salt and stuff from underneath until I installed Scott's belly pan (which I had to retrofit because the OEM one was like ripped off with the bolt threads rusted in) but the pan is shielding the engine now. I still get crud and stuff in through the wheel wells though. Don't want that, plus there's a risk of that crud somehow getting caught up into my WAI.

Depends on the car. My Superbeetle has a positive displacement pump that moves air from the engine compartment into the shrouding. Streamlining is not an issue.

The Dasher has a rat's nest of hoses and cables and wires. More modern cars have coils right next to the spark plugs and covers for the bumpy bits. Look for show car engine compartments, the have flattened firewalls and hidden wiring.

Most of the internal drag is in the radiator itself.

engine bay
 

*an old metric was,that the cooling system could constitute up to 12% of a vehicle's overall drag.
*over the years,automakers have improved on that,with fake grilles,active shutters.
*the 1963 Walter Korff' Chrysler Charger Daytona cooling system would cover the inlet portion of drag,with it's 1/6th-height grille inlet,and fully-ducted passage to the radiator.
*to reduce from there,you'd have to fully duct the extractor portion,with contoured tuned outlets located at low pressure regions on the body.Ferrari has spent over $100,000 to develop a working system such as this.For one specific car.
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The lowest drag cars are electrics,with virtually zero cooling systems,or ICE vehicles,with closed fronts,and rear radiators of integrated,aerodynamically-tuned design.Again,$hundreds of thousands.

I think on your own front engine car, the best you can do if you have a really big grille would be block part of it off and make some ducting for the radiator right? It would be very difficult to tell how the air flows through the engine bay and modify fenders or the hood accordingly.

The 2 dirtiest parts of the engine bay, from my experience at least, comes from the gap between the front bumper cover and the radiator being open (some manufactures have this open, some don't) as well as the area from the front bumper cover to the frame crossmember being uncovered (again, some manufactures cover this already). My wifes old car was pretty dirty under there, a good majority of the air through the lower grill would easily just get redirected under the car. I used coroplast to make ducting from the grill opening to the sides and bottom of the radiator and blocked off half of the opening and saw a noticable improvement. I then made an under tray/belly pan from the bumper to the crossmember and on the interstate I was getting about 6 mpg more than before, and that was with 4 adults in the car. With the belly pan going back/down to the crossmember there should have been plenty of room for the air to get out, if anything I think it may have even created a low pressure area to help draw air out of the engine compartment.

Pictures here:
https://ecomodder.com/forum/showthre...pan-17232.html

Was the side panel ducting to increase efficiency because of the blocked off upper grille?

From that thread:
https://ecomodder.com/forum/showthre...n-17232-2.html
Did you ever get the cooling issues resolved?

I am not a fan of grille blocks because I had some scary moments of near overheating when the weather and or traffic changed plus once a fan controller failure forced me to pull over.

Not so much due to the grill block, but in general just to direct all the incoming air to the radiator.

The cooling issues got resolved with a new radiator/coolant flush. After pulling the old radiator I back-flushed it and got some nastiness out. The fans would only kick on if stuck in traffic with the new radiator/coolant.

That car is long gone, one day the trans decided it didn't want to disengage the parking pawl when I put it in gear (my best guess anyway). It had been sitting for about a month due to a seized AC compressor so I suspected the brakes were sticking when I tried to back up. Gave it some gas, heard/felt a big clunk, and ended up with trans fluid on the driveway.

One of the main reasons to take air into the front is the radiator. Can you move the radiator to the rear of the car, fan the air from under the rear, through the radiator, and exit it through a new grill between the tail lights, filling in that low pressure area? You can use a much smaller front intake, perhaps a small thermostatically open-able chin intake where you can reduce under-car flow,, to vent the hot engine compartment air out behind the front wheels, where there is a low pressure area.

That's a bag of cats.

Maybe you should find some historic examples of what you are talking about, probably looking in early 1970's racing and read why they may have failed.

Maybe a living example can be found in one of today's race cars.

Someone is going to mention one of the Ford Probe cars, maybe the IV..........let us know what you find.

I personally think radiators like high pressure areas to force air though their gills, lower pressure at the tail end of the car maybe isn't all that attractive from an engineering efficiency standpoint.

Instead of saying NO, why don't YOU let Us know why it hasn't worked?

Part of the whole thing of coming forward with new ideas is doing research on them prior. It's not on us to prove you wrong, but on you to prove yourself right.

Or I can keep it short to save time. drawing the air from under the car is inefficient because of already turbulent airflow. Removing some of it and discharging it out the back isn't going to do any good becuase you're taking turbulent air from 1 area and moving it somewhere else. It would lower the air pressure under the car which will screw with aero on the sides, same way your rear window aero is weird due to air coming from the sides and wrapping around. I imagine there's probably a really good reason why you don't see it on racecars. The only racecars I can really think of that relocate the radiator in any way are some rally cars, where aero is minimally important. Probably the best cars to look at for ideas would be NASCAR racers, since they are required to keep the radiator up front. All the ducting you'd have to run, not to mention the weight of the fans to pull the air up is just going to be extra weight that's going to make the air leaving the car turbulent as heck.

I've always imagined that the front of the car is kind of like a parachute when it comes to drag. I think that adding hood vents to a car would have a measurable gain in fuel economy, but I have yet to obtain hood vents to try this.

Instead of rejecting others' contributions, you might do a site search. Here's one example of what you can find, a thread from 2013 that kach22i was in:

https://ecomodder.com/forum/showthre...ery-26356.html

And Indycars:

https://ecomodder.com/forum/member-v...627-104113.jpg

And prototype racers:

https://ecomodder.com/forum/member-v...627-105925.jpg

And aero is very important in the series those types of cars race in.

Perhaps the reason we don't see rear-mounted radiators in street cars isn't that it's unfeasible, but it's unfeasible at an acceptable cost and with typical packaging. Just look at the size of the ducts on the LF-A:

https://justforsneaks.files.wordpres...arter-view.jpg

It's not on me to prove a suggestion to you and that mouse in your pocket. It's just a suggestion, and I make them all the time. You don't have to look into them if they are not addressed to you.

We may as well be nice to reach other, OP hasn't posted since permalink #1.

"That's a bag of cats" ≠ NO
What makes you think that's a mouse? :)

edit:
The question isn't about cooling, it's about cleaning up the engine compartment to reduce internal drag.

VW operated successfully for decades with rear engine cooling. The trick is the shape of the roof and the careful shrouding around the cooling fan.

https://c1.staticflickr.com/3/2689/4...b3f0b781_b.jpg
https://c1.staticflickr.com/3/2689/4...b3f0b781_b.jpg

A German Look Beetle will have a plenum to calm the intake air for induction. A front engine, for balance:

https://i.pinimg.com/736x/56/c9/cc/5...ef00ac7e9f.jpg
https://i.pinimg.com/736x/56/c9/cc/5...ef00ac7e9f.jpg

Good Thread, rear radiator shown on post #32 Probe IV, and twin rear radiators post #51 Lexus LF-A.

Still not sure where that Lexus is drawing feed air in from, must be from under the car via tunnels like an F1 or Indy car.

EDIT:
Thanks for posting that image, it really clears it up.

I just didn't see any openings on the side large enough to do the job, they hide them in lieu of highlighting them. Guess the incorporation is just too slick for my eyes at a quick glance.

http://www.thedetroitbureau.com/2009...11-lexus-lf-a/
http://www.thedetroitbureau.com/wp-c...side-scoop.jpg
So it wasn't on the concept we looked at a couple of years ago?

I think they were just much smaller on the concept FL-A.

They still look too small for the job, but I bet it's been tested to death and is spot on.

EDIT-2:

More on the FL-A Concept as the old links are in the old thread are somewhat disrupted by time.

Lexus LFA Concept
https://en.wikipedia.org/wiki/Lexus_LFA
https://upload.wikimedia.org/wikiped..._I_Megaweb.jpg
https://upload.wikimedia.org/wikiped...Geneva_168.JPG

These inlets remind of a recent McLaren model.

The 2018 McLaren 720S has 15 air inlets, and here's what each one does
https://www.motorauthority.com/news/...-each-one-does
https://images.hgmsites.net/med/2018...00595881_m.jpg
I don't think they were worried about it filling up with snow.

I didn't say "NO".

I said it was a bag of cats.

I also said see Ford Probe IV, vintage race cars and current race cars.

In one of the old threads linked to mention of 24 Hours of LeMonds was made, in addition check out many off-road buggy type vehicles.

Bag of cats isn't NO, a bag of cats says be careful you could get scratched and it probably will not be worth it.

I meant it in humor, not as an attack.

It's just that I've seen the language "tell us" or "show us" many times used to say "It's you against all the rest of us". Maybe I over reacted. I apoligize.
I agree. kach22i. I apoligize.

I didn't know the LF-A had rear-mounted radiators until I read through that thread. That's how subtle those openings are; I had assumed they were for a differential cooler like the 2013-2017 Viper or 2014+ Corvette.

http://www.blogcdn.com/www.autoblog....t-viper-fd.jpg

https://www.corvetteforum.com/forums...r-stingray.jpg

On those tires, that thing probably doesn't even move in the snow. I pulled the Viper out of the garage in the snow once just to rearrange some things and it took me half an hour to get it back in.

I have many similar stories.

I used to have super sticky summer blend Yokohama tires on my old 911 (not good below 50 degrees), went to put gas in it for the winter at the nearby gas station. The temperature had dropped and there was a slight dusting of snow blowing across the road. I decided that a 3/4 full tank was good enough as I slid across the road sideways trying to make it back to my garage. I never left the side streets, never got the gas.

I don't think the McLaren people worried much about their cars being driven in the snow or in the rain for that matter with that intake design.

EDIT:
Vman thanks for bringing up the point of other inlets, lead me to discover this about the FL-A.

Dec 2011
2011 Tokyo: Lexus LFA Unclothed, and How it Was Built - Diorama Style
Dec 2011
https://www.motortrend.com/news/2011...-style-141375/
http://forums.pelicanparts.com/uploa...1548872164.jpg
http://forums.pelicanparts.com/uploa...1548872164.jpg

Apparently not all of the FL-A's cooling requirements are addressed at the rear, that makes much more sense to me now. A V-10 takes a lot of cooling, those tiny rear/side window inlets are not alone.