Engine Cooling

[skid542]

I'm starting to really get my heels dug into my build now and will be putting the engine in the car next week. Because I am still refusing to run intercooled and looking at all my cooling coming from my injection system I am trying to minimize as much heat in my intake tract as possible.

I'm doing this in a couple ways. The first is general heat in the engine compartment - all my exhaust pieces are being ceramic coated and my turbo will be wrapped in a blanket. The radiator hoses will also get heat wrapped. The second is I'm looking at phenolic spacers, assuming I can get clearance to my hood with the IAT sensor mounted in the center of the plenum.

The third approach is heat blankets around my manifold and over the coolant cross over. Which brings me to my question at hand - how effective is our cooling system? If I put insulation over the top of the block, am I going to overheat the block or cause significant uneven heating of it? My radiator is an aluminum CR Racing radiator with two low-profile fans. I am planning on having insulation on the underside of the manifold too.

Am I going overkill? Will I be looking at damaging the block? It is a race car and will get driven hard so I do want to make sure it's got cooling capacity. Are there are any black coatings I can put on the radiator to make it more effective?

[ciper]

Do you regularly monitor coolant temperatures? Do you push your car hard? If so I have something for you to try and Id give it to you very cheap as long as you promise to give me data...

BMW doesnt seem to think so...
http://www.bmwblog.com/2009/10/20/bmw-s ... echnology/

I read an article devoted to the engine encapsulation idea but I cant find the link at the moment.

[evolutionmovement]

I read before that BMW was also using heat to run a steam turbine that would generate electricity.

I'd be curious about this myself. I'm not going to covering the engine and the lack of weight and turbo will be low stress, but the EJ22 I'll be using in Tigershark will be in a semi-sealed engine compartment and using a smaller radiator. Hopefully, I'll be able to match the stock radiator's cooling ability by using a 2-row radiator and because the ducted airflow should allow for much more efficient heat transfer than the Legacy installation.

And I'm always looking for more efficiency.

[Legacy777]

Personally, I think you'll be fine. I've been running the non-turbo radiator with my turbo motor for several years now in Houston heat and have not ever seen temps creep up.

As I may have mentioned, the tuner in California said my car was one of the coolest running Subarus he had ever had on his dyno.

I run a 50/50 premix antifreeze & water, and Redline water wetter. It's worked very well for me.

[RJ93SS]

a big fat mid hood scoop will keep that intake manifold cooler

[93forestpearl]

A vent like mine between the radiator and motor pays huge dividends. The engine is a relatively high pressure area. Letting air escape from the engine bay helps significantly.



This vent dropped my intake temps by about 35 degrees by making my intercooler much more efficient.

[skid542]

Thanks for the replies guys.

The whole point of doing all of this though is to avoid the tiny amount of lag of a FMIC and more importantly - I want to try and keep the car a bit more stealthy. A big scoop like that kinda defeats that purpose .

[ciper]

You want the car to look stealth, so why aren't you installing an AWIC? I have a ton of them and wouldn't mind to sell you one. You could run a small heat exchanger in the front and no one would be the wiser. You keep your short intake and you could even use an NA hood.

Why aren't you ceramic coating the intake manifold? Buy the sticky mylar heat wrap for the intake components.

I've always thought that if you cut vents into the portion of the firewall that leads to the wiper arms it would help reduce temps.

If you plan to run a cat it helps to move it down to a part of the exhaust that runs parallel to the ground.

[evolutionmovement]

The wiper arm area is actually a high pressure zone—that's why the HVAC takes air from there. Where Dan has his vent is a low pressure zone, so the high pressure from inside goes out. I'm likely doing the same with mine, but using building a shroud (if I can fit one) to use it strictly for the radiator exhaust and sealing off the rest of the compartment and upper grille. Should reduce temps and drag.

[skid542]

Ciper, I don't like the mess of an AWIC and the extra plumbing and such. current front strut bar would also have objections. It's an option but it's not one I'm wanting to use.

I thought about coating the intake but it's a cost item. I'm also not sure I would gain much in ceramic coating it vs just heat wrapping it well. I know ceramic's the way to go with exhaust pieces and it would probably as effective with lower temps too. The heat wrap I have should be pretty adequate though - designed for aircraft motors.

And I don't have a cat (sorry EPA/PETA) but my downpipe will be ceramic coated.

[kimokalihi]

While reading this I was thinking, would it help to come up with a shroud/vent that would go over the entire radiator and direct air from the fans down under the engine? Would this work?

I too am looking for ways to keep my intake temps down. I already installed the 8mm Phenolic spacers under my intake but I'd like to do all I can to keep the temps down which is one reason I don't want to use a cone filter in the engine bay.

I think without completely redirecting the airflow from the radiator fans, wrapping the coolant hoses are going to bring you less than significant gains. There's far more heat coming off those fans than off those hoses. I'm interested in the ugly hood scoop if it can be combined with my idea of a shroud type vent for the radiator but I'm more partial to the idea of routing it under the engine if that will work. Don't like that hood scoop but I'd do it if there were significant gains to be had and routing it underneath wasn't going to work.

I'm pretty sure our cooling system can handle quite a bit of heat, I've NEVER had my legacy get hot even during the hottest of summer days. I'd be interested in having my intake ceramic coated if that would make difference worth the price. I plan on ceremic coating my header, up pipe and turbo. Maybe down pipe too. I may buy a heat blanket for my turbo as well. For now they're just heatwrapped.

[evolutionmovement]

My guess is exhausting the heat under the car wouldn't be as efficient at low speeds or idle (heat rises) and the fans wouldn't have as much volume to dump the heated air into. At speed where the cooling system isn't (usually) as taxed, with the engine compartment to be sealed and, what I think, with as smooth a transition as possible to reduce turbulent air under the car, you'd be better off than the stock design of just dumping heated air into the turbulent engine compartment. Optimized, it's still going to be a higher pressure, more turbulent zone than exiting through the top of the hood (over which, the rushing low pressure zone will draw air through the radiator), but could be an improvement if the fans can still get out enough heat at idle (which I would think they probably can). But it probably wouldn't be a good idea to block the upper grille opening with that approach, if drag reduction is important to you. I think the shrouding would be easier to do in that case as well, since the area underneath is less restricted and more uniform.

[Legacy777]

Lee,

I really think you're splitting hairs on what you're trying to accomplish with these modifications. I can understand where you're coming from and what you're trying to do. I've been there myself. But you may need to take a step back and look at the big picture.

To do all this stuff you will see very diminishing returns on the modifications to acheive what you ultimately want. The extra lag shouldn't be that noticiable if you have the piping sized correctly and aren't doing a bunch of crazy bends.

[skid542]

Josh, I know I'm starting to get down to the fine threads. I'm not looking at doing special ducting or anything but it does sound like I can do the blankets over the engine block without trouble.

I know FMIC/TMICs are the norm and they are a great passive system. I just really don't want to go the route of a FMIC with this car for many reasons. I also auto-x the car and any TMIC will get heat soaked. I know that water/alky injection has been used very sucessfully as the only form of cooling on high power cars - BXSS comes to mind. I'm just trying to optimize with minimal efforts.

Don't get me wrong though - I'm loving all the comments on the heat blankets and the other discussions this thread has generated. I'm still open to more ideas.

[ciper]

I think to get better cooling in the engine we should tap the gooseneck right in the center of the engine for the heater outlet rather than using the outlet on the 2/4 side of the block. I think this bypass setup is part of the reason cylinder three dies since it is undercooled when the thermostat is closed.

The wiper arm area is actually a high pressure zone

I thought domestic guys put spacers under the hood hinges so air from the high pressure zone went down the firewall?

Ciper, I don't like the mess of an AWIC and the extra plumbing and such. current front strut bar would also have objections. It's an option but it's not one I'm wanting to use.

You can't see the mess when the hood is closed and you're traveling at 65mph lol Besides its a factory part :p
Front facing strut tower bars aren't that hard to find

Are you not interested in helping me test my thermal item as mentioned in the first reply?

[skid542]

Ciper, I'm going through a lot of work to clean up the engine bay. I know you can't see it going down the highway but I'm looking forward to have a nice, clean, clutter free engine bay again . And I don't want to give up my current strut bar, it's super beefy and I've found it very handy to be able to mount things too.

As far as the thermal item, I may be, depends on what you're thinking. It sounds 'top secret' so maybe we need to take it offline. I do push my car hard though - not as hard as some of the guys here as I'm not open-tracking the car and I won't be making 300+whp (chp but not whp).

[ciper]

I was gonna send you a PM but I can't figure out how lol
Its not top secret but I want to make sure it's good before I post on the forums. I'd hate everyone to use it and then some problem is discovered later.

[evolutionmovement]

Ciper, the domestics might do that as a kind of cheap cowl induction solution, though I can't say for sure. If their aim is to draw air out of the engine bay, they're doing it in the wrong place, though it probably helps cool things off. At low speeds and idle the heat could vent out on its own and at higher speeds the air going in would help cool also. As far as aero goes, it pretty much would just be more turbulence under the hood. Cowl induction works by taking air from the high pressure zone at the windshield base and channeling it into the carb(s).

If anyone's interested, there's a video or two floating around on youtube (I think) that some guy put up doing tuft testing on a 1st generation Legacy sedan, which can give you a better idea about what's going on in terms of aero.

[SubiePrice88]

this is all very helpful and interesting to read.

What is your guys input on the RS/OBS style hood vents?

[skid542]

Ciper - I got your PM, let me do some thinking on it.

Steve - I'll have to do some searching of youtube, I'd like to see that. You can get a pretty good feel for the flow if you drive in the winter on wet/dirty interstates and look at the residue patterns. You can distinctly see the seperation bubbles and a few places of transition.

Jordan - I think those vents would work very well. However, all the ones I've seen don't actually have holes all the way through and into the hood compartment, more of an aesthetic item.

I also don't want to be getting a lot of water and dirt falling down into the engine bay. I know my knock sensor is always upset after the car's been sitting in a good rain from the water coming in the stock hood scoop.

[SubiePrice88]

Yeah I was thinking the same thing as far as holes in the hood (hood vents) water and dirt would love it.

But my buddy has a 2000 OBS and the vents have a piece underneath that you can take off so its an actual vent. He runs it like that in the summer and in the winter puts the under cover? things on.

Ive been wanting to get the vents but the lowest Ive found used is $50.00

[evolutionmovement]

The vents are in the right spot for heat venting, too, as can be seen by the spots that don't seem to frost up on cold mornings and they're in a low pressure zone, so they should evacuate air as you drive. I prefer the early Impreza Turbo style vents, as they look like the Legacy rally car's, but they are not cheap when you can find an overseas source for them. Functionally, I don't think they make a difference, but being simple louvers, they MIGHT keep more water out of the engine compartment than the Impreza RS style.

[SubiePrice88]

I'm most likely going to try this than. Thinking about running two different hoods one with just the WRX scoop for winter and than another hood with a WRX or maybe larger scoop with the RS vents for the summer. That way I wouldn't be worried so much about water or snow during different times. Plus I love changing the look once in awhile.


Newb question here: Can you please explain the high and low pressure zones. I didnt know such things existed under the hood

[evolutionmovement]

Under the hood is turbulence. It might be above atmospheric, below, or the same all within the engine bay at the same time. The air going over the top of the hood is speeds up, which reduces its pressure. Pressure likes to equalize, so high pressure wants to go to low pressure. Venting the relatively higher pressure engine bay air to the lower pressure of the air rushing past will draw it outside. That's the most simple of it and I'm a lousy teacher as I tend to go off on tangents, so you should probably google car aerodynamics if you want a better idea.

[SubiePrice88]

Thanks!

Where would the low and high zones be?