Reducing underhood heat - S10 pickup edition

I have noticed my LS swapped S10 generates a ton more underhood heat than it did when it just had a 305 SBC (big surprise).  The radiator and fan are keeping up with cooling the engine in its stock form, but I am worried a bit, both for when I add more power, and more so for cooking wiring, plastics, etc underhood much faster than they would be otherwise.

A quick view of how it is stock:

The airdam is attached to the leading edge of the bumper:

View under the bumper.  The large round objects are the mounts for the core support, and the radiator is inset into it, so it sits back from the airdam, obviously.

From the various pieces of plastic attempting to redirect or block airflow, I think GM didn't really try to create much of a low pressure zone behind the radiator, they just tried to keep turbulence from preventing air flowing through it:

I can't remember if this foam was stock, or if it was on the 3rd gen F-body I used as a donor for the 305.

I am wondering if a second airdam below the core support would lower the air pressure in the engine compartment to the point that it could extract a bit more hot air to the underside of the car while I am driving.  Something like this:

I'm not really in a position to do a bunch of detailed analysis.  I suppose I could see if my gopro knockoff still works, rig something up, and tape some tissue paper strips under there, but I wanted to see if this idea is sound or not at all.  If so, would it also make sense to create a horizontal surface from the front of the stock airdam to the new airdam?  I'm wondering if there would be some weird effects from air getting trapped between the two if I don't.  Would it also make sense for the new airdam to be lower than the stock one?  I don't want to go too low, so I can still get a jack under it easily.

Is this whole idea stupid, and I should consider coming up with some hood vents (would rather not due to rain) or some vents on the fenders to extract heat?

eastsideTim said:

Is this whole idea stupid?

nope.  but, this might be one of those "god is in the details" scenarios.

eastsideTim said:

I should consider coming up with some hood vents (would rather not due to rain) or some vents on the fenders to extract heat?

that would usually be my recommendation... especially after seeing how high the radiator is mounted in your S10.

eastsideTim said:

I have noticed my LS swapped S10 generates a ton more underhood heat than it did when it just had a 305 SBC (big surprise).  The radiator and fan are keeping up with cooling the engine in its stock form, but I am worried a bit, both for when I add more power, and more so for cooking wiring, plastics, etc underhood much faster than they would be otherwise.

A quick view of how it is stock:

So, first thought is:  I would suggest moving the Hella lights apart to either side of the grill (it's ok if the upper quarter of each light covers the bottom corner of the grill.  That would help unblock some of the good clean flow coming in to the radiator.

eastsideTim said:

[...]

View under the bumper.  The large round objects are the mounts for the core support, and the radiator is inset into it, so it sits back from the airdam, obviously.

From the various pieces of plastic attempting to redirect or block airflow, I think GM didn't really try to create much of a low pressure zone behind the radiator, they just tried to keep turbulence from preventing air flowing through the it:

I can't remember if this foam was stock, or if it was on the 3rd gen F-body I used as a donor for the 305.

 

I am wondering if a second airdam below the core support would lower the air pressure in the engine compartment to the point that it could extract a bit more hot air to the underside of the car while I am driving.  Something like this:

 

I'm not really in a position to do a bunch of detailed analysis.  I suppose I could see if my gopro knockoff still works, rig something up, and tape some tissue paper strips under there, but I wanted to see if this idea is sound or not at all.  If so, would it also make sense to create a horizontal surface from the front of the stock airdam to the new airdam?  I'm wondering if there would be some weird effects from air getting trapped between the two if I don't.  Would it also make sense for the new airdam to be lower than the stock one?  I don't want to go too low, so I c an still get a jack under it easily.

I think one of the biggest issues the "lower airdam" idea you have is that (I'm assuming here... I don't know the dimensionality details of SBCs or LS') the LS motor is so close to the back side of the radiator, that you're probably going to have trouble getting flow out of the bottom. 

one of the best first things to do is make sure any of the air that comes into that grill, *has* to go through the radiator, by making a shroud between the bumper (where the grill is) and the radiator.  And then making sure the shroud is sealed to the bumper and to the radiator side.

then, after that, work on figuring out ways to unblock the back of the radiator so the exhaust air can escape.  Unfortunately, glancing at those pictures... I'm not sure there's much room to move the radiator forward; or do anything about tilting it?

In reply to sleepyhead the buffalo :

Thanks for comments.  The factory air diverter in the diagram doesn't form a perfect seal, but it appears to work like a shroud, filling the gap between the frame rails and keeping air going through the grill from bypassing the radiator and going out behind the bumper.

The radiator is as far forward as is practical for now - the core support was opened up enough to move it forward to where the AC condenser used to live, and there is a transmission cooler in front of it on the passenger side that comes close to contacting the back of the grill.  I'm not too concerned about the cooling capacity yet, but will be in the future.  The truck only runs a smidge over 200 degrees when it is moving, and that's with a 190 or 195 degree thermostat.  Bigger concern right now is getting stagnant hot air out of the engine compartment.

I know I have seen hood vents that have some method of directing water into a drain tube, so I may have to look into something like that.  I'll also try to get some pictures to show more of the engine compartment, and the space it has.  I think there is enough room to get air out via the underside, but I could be wrong.  Being a pickup, it's got to be pretty aerodynamically dirty underneath, but with it being stock ride height, there are a lot of opportunities for air to get out from under it.

The 4WDs have a plastic pseudo-skidplate which sorta does the same thing as your idea for a 2nd air dam, and it does extend lower than the factory bumper-mounted air dam.  I would believe it if someone told me the result was a high pressure 'bubble' increasing front end lift at high speeds... but I cannot imagine any way for it to hurt airflow thru the radiator or out of the engine compartment.

Not the best pic, but it'll have to do for my lunch break. 

Quick measurements put the crank pulley about 4.5" behind the core support, and the oil pan somewhere around 7 to 8 inches behind the core support.

Tim, what radiator are you using?

If you don't mind putting holes in things... what about more air in?  A hole saw to the bumper could make quick work of this.

gsettle said:

Tim, what radiator are you using?

C4 Corvette automatic transmission radiator

¯\_(ツ)_/¯ said:

If you don't mind putting holes in things... what about more air in?  A hole saw to the bumper could make quick work of this.

I'm getting enough air to keep the coolant at a reasonable temperature as is.  I've actually blocked a few holes in the core support that aren't being used anymore in order to force more of the air to go through the radiator.  I suppose I could unblock them and see if that helps underhood heat without hurting engine temps

Really don't want to cut up a rust free bumper in Ohio.

In reply to eastsideTim :

In that case if you want some vents, there are a bunch of variants of these cheap on Amazon and they're pretty low profile.  I've used them on a couple things now.

Would adding vents into the front wheel wells do anything to help, or just let road spray and dirt into the engine bay?

Maybe that's not so easy to test, I forgot the S10 has full steel inner fenders (the Colorado/Canyon has an easy-to-remove rubber flap).

I found a thread from Ecomodder showing the results of CFD for a 2nd gen S10.  However 1) it's a 2nd gen not a 1st gen; 2) the analysis included some aero mods like an extended airdam; 3) the analysis did not include airflow thru the radiator, plus the entire underside is a simple flat plane.

In reply to Oapfu :

Interesting how abrupt the change from high to low pressure at the edge of the front end is.  I would assume, due to the flatter shapes, the 1st Gen S10 would be even more severe.

I'm not sure how to interpret the air speed diagram.  It makes sense that the air behind the extended air dam is going to be moving slower than the air going under it.  The layer of fast moving air at the bottom makes me wonder how low an air dam would have to be to work the way I want it to.

I may just have to do a little experimenting, with some cheap plastic, and see if I can find a temperature probe that I am willing to stash under the hood in various positions.

I have a 98 (2nd gen) Sonoma that ran hot on track. I bought a S10 hood at the junkyard (s10's have a ridge down the middle of the hood with about another inch of under hood clearance) and cut some vents about 12inch square right behind where the core support is.

I ran about 120 miles at Putnam park about a month ago and temps stayed right around thermostat temp

In reply to gsettle :

I'm casually keeping an eye out for a Lumina Z34 in local junkyards.  They have functional hood vents with diverters underneath to run any water out of the engine compartment.

Maybe my reading comprehension isn't great, but are you seeing elevated underhood temps with this swap?  Your coolant temps aren't showing it, with coolant just over thermostat rated opening temp, right?  I'm wondering what you need to fix here.

If you have determined that temps are elevated, I wonder about a small version of the classic Mopar "dustpan" hood scoop turned backwards to vent underhood air towards the windshield.  Not sure what air pressure is like across the hood though.

In reply to pres589 (djronnebaum) :

You are correct - coolant temps are fine.  I'm more concerned about accelerated wear on wiring and plastics under the hood.  So not exactly something critical right now, but would be nice to address.

I'm wondering if there's a low cost absolute pressure gauge that could be temp mounted in the cab for reading while driving, and run a hose to different positions under and above the hood, to find a spot where pressure under the hood is at maximum to place a hood vent.  Probably hard to have something low cost with high accuracy and resolution though.

Fleabay chinese dual fans are cheap, slim, and move massively more air than factory.  Also the generic bug radiators from summit/jegs should drop right in.  
 

in terms of aero stuff I'd seal up around the rad and then maybe do some kind of ducting scoop in the spoiler?  Like this ish?

Sorry I'm late to this, but I'm seeing a lot of focus on the radiator and flow, but nothing on what's going on with exhaust.

So, I had a 95 Miata that I put a header on. Stock form was fine, but after I put the header on the underhood temps were awful. The hood would steam in a light rain. I got a trackdog header blanket and the underhood temps wound up better than stock.

So what's going on with the exhaust?

Not the same vehicle but I added an air dam under the bumper of my 66 Chevelle and it helped with under hood temps a lot. I also plugged every hole, crack, slit that I could find so that the only air getting in is through the radiator.

At the same time I sealed the bottom of the bumper back to the core support with aluminum panels so less is getting in around the bottom. 

I also wrapped the 8-10" of exhaust pipe down to the catalytic converters. 

I too never had a cooling issue. It runs very cool but when I'd open the hoo$, wow, was it hot under there.

No more.

So, I think you're going to have to do some more experimenting.  Typically, the air dam will create a low pressure area just behind it.  And using the 66 Chevelle as an example above, the air dam appears to be pretty close to the bottom of the radiator.  Which means the hot air coming from the radiator is easily drawn downward into this low pressure area and drawn away from the radiator quite easily.  Probably why the owner of the Chevelle had a very successful outcome.

While I think the air dam on the S10 would be an effective tool to create the same low pressure area, the part that would concern me is that the radiator is too far away from the air dam to be able to take advantage of this low pressure area.  Obviously, as the speed of the vehicle increases the low pressure area becomes slightly greater and more effective at removing the hot air from the radiator.  

As another example, I copied a similar design that Ford had done on the FOX bodied Mustangs and added a similar lip to a Honda Civic this past summer.  The lip I added was just below the bottom of the radiator, and while not useful just tooling around town..........it helps when I get the urge to have some fun spinning the engine up to 7,000 on a regular basis.  (See picture.)

My suggestion is that somehow, someway get the radiator closer to the air dam.  Or ditch the air dam, and put a lip spoiler just under the bottom of the radiator. In so far as underhood heat goes, placing a hood vent or vents between the front edge of the engine hood and the front tires would help evacuate some additional heat out.  Placing hood vents too close to the windshield will only draw air into the vents.  

On my Chevelle, the bottom of the radiator is even with the bottom of the front bumper. So the entire airdam is below the radiator. I think what makes it work so well is that it's completely sealed from the bottom of the bumper back to the core support/bottom of radiator.

Refering to the CFD above, I would guess the high pressure (red) on my car doesn't extend near as far under the front. Less air under the car creates low pressure at speed which gives the hot, high pressure air under the hood an almost vacuum to flow into. Almost.

The same CFD shows that if a hood vent is going be effective, it's going to have to be right behind the radiator. Venting closer to the windshield won't help at all.

Bumping this up since I may be having a dying alternator that really doesn't like the heat.  In order to let its future replacement have a better life, I'm thinking more on venting the heat out.  While Lumina Z34 and Lebaron turbo vents would look better, they are pretty much nonexistent in the used market anymore.  
 

It looks like GNX replica fender vents are easy to come by, and the inner fender structure on the S10 is open enough that air could flow to them.  Also, they aren't showing up in u-pull yards near me yet, but 2014-2015 Camaro SS hood vents may be an option, too.  Not sure I want to lose the era appropriate style the truck has right now, though.

Finally, Apexcarver's post has me thinking about the stainless headers on the engine.  Maybe I should wrap them up as much as is practical and see how much that helps.  EDIT:  Just looked under the hood.  No way I'm wrapping the headers unless I do a lot of disassembly under the hood, and remove them.  Just too tight to wrap the primary pipes in place.