Harv

iTrader: (4)

<- Should have realized was in Race Prep section.

Mobius

iTrader: (2)

So maybe I'm missing something ... why pull air from the cowl?

Given: all of your current heat exchangers are ducted out of the engine bay, therefore airflow through them is unaffected by air pressure of the engine bay itself.

Therefore: run one opening from the high pressure bumper area into the engine bay. Run hose pointing at turbo, if you want. Put reverse naca duct or louvers above turbo for exit.

Profit?

ThePass

iTrader: (3)

I'm with you Mobius. Pressure doesn't build into anything significantly positive until you get to the windshield glass itself. Fine for an intake, but I'm trying to force air through the duct.

Venting directly up and out looks like the best exit. So the higher pressure at the inlet the more effective this will be. Logical place to look for that is the front of the car.

The only concern is introducing drag with a forward facing duct. But unlike a duct going to a heat exchanger which is a large flow impediment, this actually shouldn't have much obstruction, so I'm thinking drag increase would be minimal.

If I'm ducting from the front, I'm thinking one 3" diameter hose should do the trick... Does anyone know where to find flow data for different hose diameters?

I have an inlet on the right side of the air dam for the oil cooler, so I could kill two birds with one stone and satisfy my OCD for symmetry by matching that inlet with one on the left for this.

-Ryan

nitrodann

Great thread,

I like the idea of a duct from the front or from the undertray. How do you intend to run the hose, which way through the bay, also what kind of hose?

Dann

ThePass

iTrader: (3)

Probably the same stuff used for brake ducting, high temp. Need to figure out the routing...

Mobius

iTrader: (2)

Do you necessarily?

If you provide a bumper opening for a source of air, provide the low-pressure exit through the hood, and put some radiant heat shields around the turbo that will also act to reinforce the chimney effect, aren't you 90% there?

Edit: taking you above template, but leaving the front open, is what I'm thinking. It will create its own airflow. Sealing it and ducting the source opening directly to it would probably be more effective, but will be more fiddly.

ThePass

iTrader: (3)

It would probably be effective to some degree, but I'd like to make it more

Building a bit on that though, what do you guys think about heat differentials; the heat radiating off the turbo has to be what, several hundred degrees? That temp quickly falls off as you get further from the turbo, but my hood has been 600* after a session, so 600+* around the turbo safe to say...

Comparing to that, what's the air temp coming out the back side of the radiator? 200-ish or less?

Since the desired effect is to simply move the super hot air around the turbo out the hood, not to actually cool the turbo itself, I'm thinking 180* air will be just as effective at this as 95* air (ambient in the summer).

And since the secondary goals are:
- need decent pressure at inlet to ensure directional airflow
- ideally don't add another opening to front surface of car which would marginally increase drag
- *bonus goal* be able to vent the turbo heat through this system while stationary in pits

If I duct air off the back of the radiator fan for this vent system, I think I'll achieve every one of those goals, including the bonus of being able to kick the fan on in the pits and push air through it.

The slightly hotter than ambient air is still cool air relative to the turbo, this would be super efficient (recycles "wasted" air), doesn't add another opening to the front, and requires less ducting length and simpler/straighter than needing to go around the intercooler/radiator.

I'm liking this more and more as I go over it in my head...

-Ryan

nitrodann

Good idea, please continue.

cordycord

iTrader: (2)

My six year old is watching me type, and he wanted "the glasses falling on the beaver."

The most direct way to get rid of the heat would seem to be out of the exhaust. I know that some people ceramic coat the hot side, and others put a heat blanket over the hot snail.

A slightly larger heat shield area could be made as you're suggesting--and it would definitely benefit from internal heat coating. It would basically act like a larger version of the turbo jacket, except that you want the radiant heat to exit a chimney.

Maybe a good test would be to build the shield first and put some heat strips on it to check temperatures. Obviously if stuff is melting then it's too hot:


If the box with heat shield doesn't do enough to stop the heat, then play around with air flow. You may not even need an outlet to make a difference.

Duct / Exhaust Hoses

freedomgli

Bernoulli's equation will give you a very close approximation. You'd need to use CFD to get exact numbers because the geometry likely gets rather complex when factoring the effect of your duct work, turbo, heat shield and hood vent.

See also Lined Silicone Air Duct Hose Pressure and Vacuum Limits

Have you considered adding a thermally insulating turbo blanket instead?

cordycord

iTrader: (2)

Let me know if you simply want a pre-made K-member...stronger, lighter, and more room for ducting.

ThePass

iTrader: (3)

The TD04-15G with its external wastegate has a funky shape that is difficult to wrap a turbo blanket around. The only decent looking blanket for a TD04 I've seen (not interested in the china-made ebay stuff) is the PTP blanket, but that's for a Subaru TD04, and from what I can see the shape seems different enough that I'm not sure it would fit my turbo. Don't really want to take the $150 gamble on that.

I'm considering wrapping the downpipe, but possibly would do that even with the duct since the downpipe extends out beyond the shielded area...

-Ryan

cordycord

iTrader: (2)

I'm sure you know this but I'll say it for posterity; wrapping exhaust headers concentrates the heat to an extent that the metal underneath can become brittle and crack. You may not have any issues, but then again you might.

ThePass

iTrader: (3)

Yep so I have heard, and why I have not used wrap to keep heat down to date.. but was considering it as a way to, as you said, contain the heat and evacuate it out of the exhaust.

I did some testing with hose and duct placement relative to the radiator fan yesterday and then started construction of the heat shield, but only had a little time to spend on it before going to the dyno so I'm rejoining that project later today after I get some work done.

-Ryan

freedomgli

All exhaust systems suffer from thermal fatigue. But using thermal insulating barriers is generally not an issue provided you're using the right exhaust materials to begin with! Inconel, 304SS, 321SS, galvanized mild steel, cast iron and various proprietary alloys all have their purpose. As we all know, design is a matter of compromise and all exhaust systems are wear and tear items so I would expect a mild steel downpipe to behave differently than an Inconel one. And cost a lot different, too!

If it was me I'd probably call PTP to ask them about how one of their blankets might fit your application. I'd also consider Zirotec or your ceramic flavor of choice. Belts and suspenders approach. Not that this ducted vent idea is bad idea. It's a neat science project and seems very resourceful and economical to achieve. I just rather drive than tinker!

Peodi

I have a ptp blanket on my td04 and it is rather effective. It is a pretty general shape using stainless wire to tie the ends together so it may fit, though would second giving them a call to find out.

ThePass

iTrader: (3)

Thanks for the solid info on the ptp blanket fitment.

I've spent some time researching the subject of turbo blankets and decided a blanket is not the appropriate tool for what I want to achieve.

Progress with my heat venting system is ~50%, had to sideline it a bit to prep for a shakedown at an autocross that was today. That went well with just a few small bugs to work out overall, so back to this project in the next day or two.

I'm making it modular so that I can do some back to back testing of a few different configurations and hopefully have some good data at the end of this.

Considering my options for taking heat readings. The alcon brake temp strips and brake temp paint both have less than ideal temp ranges and increments. Not to mention rather $$. I might just use a digital infrared temperature gun.

-Ryan