Ducting and airflow
 

I'm re-shuffling my shit, yet again. Last event at WSIR, I stacked the intercooler and oil cooler on top of each other, sealed them together, and stuck them in front of the radiator. Oil temps were LOW, like 180 degrees, but coolant temps were 240 and rising on the 2nd hotlap.

So, back to the drawing board. With constant overheating issues, and more power on the way, I don't think there's any way around it except to feed fresh air to the radiator at all costs.

Therefore:
-IC gets laid back, ducted to the front mouth, exits underneath the radiator
-Radiator stays in stock location, but gets fully sealed to the mouth
-Oil cooler gets hidden where the OEM crash structure normally is. It's so big I don't even know if I'll need any ducting to it.

Beginning of the IC duct:
Attachment 204695

Final IC duct:
Attachment 204697

Oil cooler location:
http://img.photobucket.com/albums/v3...g/DSCN1542.jpg

Comments? Hustler thinks the IC won't get enough air. The surface area of the opening to that duct is about 30% of the surface area of the core. I also have water injection, 3gph above 6psi, so I am hoping to not have IAT issues either way. Oil temps are essentially a non-issue with this massive new cooler, so I can tuck that away wherever I want. If I see it getting warm, I can punch a few holes in the bumper or figure out a ducting scheme to remedy that.

If you car is fully apart. I would copy David's (Splitime) setup to the T. Full vmount, and don't waste time doing anything else. Do it now so you don't end up doing it later.

I have no desire to v-mount the car. There are serious aerodynamic problems with that.

Explain....

You need explanation on how cutting an enormous hole in the upper skin of the bumper causes a fuckload of aerodynamic drag?

You dont need to cut anything. What are you talking about. The bumper can easily remain stock and still implement a full vmount setup. If you can't envision that then there is no helping you.

Just because Dave cut the hole in his bumper has nothing to do with the actual setup. Its just something he chose to add.

Don't treat me like a retard when you can't get your ideas across correctly.


In the stock location, there's around 3" between the splitter and the bottom of the radiator. I've basically laid the intercooler back so it vents under there. I guess I've moved the intercooler into the location it would sit in a v-mount setup, but not the radiator since it still sees full airflow in the location it's in. Do you think tilting the rad forward would give enough of a benefit to warrant the work? I'm really not keen on cutting the radiator support out, either.

I was talking specifically of the Vmount setup. Not cosmetic changes to the outer skin of his car. Sorry if there was a communication break.


I did look at how you have it laid and if you say the rad has enough space as is then I would say leave it how you have it. I think the greatest benefit as far as reducing charge temps would be to have an "under tray" extend past the IC and have a vent on it similar to how you would have an extracting hood. Only underneath the car. I haven't seen any shots of your car from overhead, but I assume you already have an extractor on it as well?

Yeah, there's a big hole cut in the hood. The splitter extends back, the width of the subframe, to the front of the steering rack. I was originally going to put my oil cooler under the steering rack, but I am wary of cutting a hole of any sort under there, on the off chance I go off track. If I were to put some ducting on it, it would have to hang lower than the splitter, and I'll inevitably tear it off on a curb somewhere. The two bolts that attach it to the subframe back there have scrapemarks on them, so I know they touch something.

I'm also wary of trying to pull air underneath the car, since it reduces the low-pressure zone under the car and would have an effect (a big one?) on any diffuser I try to work with in the future.

Here's a photo that shows IC angle, space under the radiator, and the splitter length.
Attachment 204693

I would have the IC butted up against the rad and sealed with weather stripping. You want to maintain a high pressure region in front of both, and that gaping hole is going to prevent that.

As far as the extractor I mentioned. What I envision is simply like a 2" wide rectangle the length of the ic core starting right where the top of the core is if you drew a straight like down onto the splitter. Then bend down the leading edge about 1/4-1/2". The lip would create the same effect as the hood extractor but be much smaller. Hell, you might not even need to make a lip since the splitter already creates a low pressure region underneath it.

In the background on the driver's side, you can see a little piece of cardboard that is the beginning of the duct that will gap the IC and radiator. I figured that I was better off moving the intercooler forward and trying to get some air to trace over the top of the IC ducting into the bottom of the rad, vs. butting it up against the rad and losing an inch or so off the bottom.

"bending the leading edge down about 1/4" is easier said than done, since the splitter is 12mm birchwood. I suppose I could do a rectangular hole and then chicken-wire it.

My issue is with surface area. Your pictures demonstrate the problem perfectly. If you look at your 3rd picture, you can see the top of the radiator, and the bottom is just hidden behind the intercooler, it's a fairly large radiator.

Yet if you look at your second picture, between the top of the cardboard ducting and the bottom of the yellow tape, that's all that's exposed to air, and it's not much. I wouldn't hesitate one bit adding a little drag if it meant it would solve my cooling issues.

Also, NACA ducts would be great on the bottom of your splitter to maybe point some more air up to the radiator, that's a steep angle though.

It's actually going to end up being like a 30x3 hole. The radiator itself is 12x24 (288sq.in), the hole in the mouth will be 30x3 or so. 30%.

Is that considered a lot? I'm not trying to be sarcastic or anything, I honestly can't tell if you're saying "it's plenty" or "I've seen bigger grains of sand".

I remember seeing somewhere that you only need about 1/3 of the surface area of the radiator worth of airflow (because the fins and crap end up taking up 2/3 of that surface area). That's what we are going off of for whether there is a big enough opening.

https://www.miataturbo.net/forum/t14760-3/

start at like post 160 and read through to the end. There is some shit that Pats posted that I ignored because I had an IC, but now that I have free air I think I can implement some of it.

I'm also going to put this fans vs. no fans horseshit to bed once and for all. I'm going to leave my current setup (sealed 11" spals) in place, throw a magnehelic gauge into the chamber between the fans and the radiator, and take a pressure measurement. Then remove one fan, test again. If the pressure goes down with the fan removed, then it's a success.

FUCK Y*S!

whoops.

Tried, its too much words for midnight, I'll read later when I don't have to wake up in 4.5 hours for work.

This is great info for the rest of us, thanks for testing new ideas! Sav, how long does it take you to get your bumper off, must be pretty quick at it?

Like 5 minutes. I just put it in place when I am doing this sort of stuff, though, so I can have it on or off the car in about 10 seconds.

Just read through that thread. Pat is 100% correct IMHO. Bigger surface area does not increase pressure. Small in, larger out does. The link provided in that thread confirms this. Can't wait til you test this out once and for all with actual proof/data.

off topic/
Pat is a smart fucker, I wish he was still here
/off topic

Side ducts. It'll give me as much as possible to the radiator.

http://img.photobucket.com/albums/v3...g/DSCN1553.jpg

Attachment 204691

I am going to be using sheet aluminum (forgot how thick, like .050ish) and rivets to actually build all this stuff. hardest part will be doing stuff in as few pieces as possible, and getting all the little stuff right (mounting tabs and stuff).

IMO that will work as good as it could. This isn't far from what AIM tuning did on their time trial turbo Miata. The only improvement would be in cruves vs. the straight off angles. Harsh angles create a ramp launching the air vs. providing a contoured surface for it follow and encourage expansion. Same stuff you see on all the prototype cars - and stock cars as documented in this article. Graphic from article:
http://image.stockcarracing.com/f/88..._cool2_6_z.jpg

I think there's a reason you see 800hp cars running 24hour races with a full body and not over heating. They focus not on the size of the inlet nearly as much as the exit of the air and what happens to the air after it's passed the inlet. In general, I agree that enlarging the inlet may show improvements over stock, but would arguing that it's not nearly as efficient as improving other aspects - like extracting or sealing up the mouth or reforming the interior of the OE mouth...

Something to consider per your oil cooler feed too- that air will be exiting into the area that contains the high pressure for feeding your rad. So you'll be fighting a pressure differential at that point from the air exiting your oil cooler vs. the air trying to pass through the rad. You might only drill two holes, bring the hold saw to the track and see what happens, drilling more holes as needed. Or devise a means for blocking the oil cooler holes (racers tape?).

what is the 3 inch gap under the radiator where all the air goes? did I miss that part?

What you are creating is something I have been mulling over for a few weeks as well (no, I'm not turbo'd, but studying and planning still). You have created a Vmount setup in this configuration, just with the IC on the bottom instead of the top where most people's end up. The hot air leaving the IC will not be a factor in your radiator's cooling capability anymore and neither will the restriction of forcing air through the intercooler before allowing it to the radiator. The low pressure area behind the IC and the radiator created by the splitter and your well-sealed ducting will ensure plenty of pull through both heat exchangers. I see it as a win.

If you saw fit, you could move, seal, and duct the oil cooler so that it's hot air exits through the opening between the leading edge of the hood and the top of the core support (where the filler panel is by the hood latch) and goes over the rad, just like the IC's hot air goes under the rad. Just brainstorming on that one. Good luck.

god I love a thread with pictures.


I could see a plate in front of the bottom edge of the IC being helpful.

Corky's rule of thumb is 1:8, inlet to surface area. Anything more ("within reason") is a bonus, provided you maintain positive pressure up front, and negative pressure behind the heat-exchanger.

- L

The way I understand it, the gap under the rad is the exit for the intercooler.

Why not cut the bottom support off the facia. Then extend a sheet of aluminum up from the splitter to the bottom edge of the IC, and extended the scoop/shroud out.

right, i see it now.

and there will be a barrier between the IC and radiator on the top of the IC?

Sav: I wouldn't worry about taking air from under the bumper. it's all going to exit the engine bay under the car anyway.

That's how I understand it. And here's a pic that applies the theory from that stockcar article discussing contours past the entrance.

now just stretch that contour across the entire bottom edge of the radiator.

+1 each.

curves mean attached flow and attached flow means flow to the bottom of your radiator.

The plan is to seal the bottom of the mouth to the top of the radiator, creating a separate chamber for the oil cooler. It'll exit above the radiator.

I have plans for one as well, as well as extending the plate on top across the radiator. I like the idea of cutting the bumper down, though.

I also like the curves. Straight lines are about a thousand times easier to assemble and build, though. Any ideas for attaching the side ducts to the bottom ducts? I was going to just have little bent tabs on the sides and rivet them to the bottom, but I can't do that with curves.

Into the engine bay, or through the hood (hole/extractor)? I wonder in this situation if it did go into the engine bay, what kind of impact it's going to have on the pressure differential there since it has a separate entry from the mouth (rad/IC feed).

The oil cooler dumps into the engine bay, but there is a hole in the hood.

I will have to cover/uncover that hole when I do the magnehelic tests.

Just be careful with cutting all this aluminum, that stuff can be sharp as a razor blade!

Sav, have you instrumented if your problem is lack of airflow or poor heat transfer from the coolant to the radiator? My guess though, is lack of airflow.

I think the reason why V mounts help, without increasing the frontal hole area, is akin to impedance matching in electronics. When you have a very high airflow velocity the high resistance of the radiator core + i/c core just makes the air pile up in front of the radiator.

I have a theory that during road testing this problem manifests as significantly higher coolant temps at higher cruise speeds (e.g. 75-85 mph) vs. at lower speeds (55-65). This is as opposed to setups which overheat in stop and go traffic.

With V mounting the air spreads out over a larger area, plus the resistance the cores present is reduced (the rad and ic aren't stacked).

This theory is probably also why my AG Bell book "4 stroke performance tuning" suggests that a lower fin density radiator is better for high speed cooling.

As patsmx5 alluded to before, enlarging the frontal hole area of the car is not good, but my theory is not so much because it doesn't improve cooling (it will somewhat), but because the cooling to drag penalty is poor. (big increase for marginal improvement in cooling).

BTW the TDR ic has plastic panels which bend airflow smoothly towards the radiator, along the same lines as m2cupcar's drawing in post #30.

I have a v-mount that I am finishing up right now. I was planning on waiting until I had some road testing in place so I could have some data to back up the design. But, if y'all want to see it I'll post up the picts beforehand.

It is a top-mount v-mount using the stock NB nose. Minimal cutting required for the body, and the framework was easy to fab as well. It is all boxed in (splitter and undertray) so all of the flow coming in the nose is forced through the radiator and IC (and a/c condenser).

Sure you can. Use a metal shrinker. What kind of aluminum are you using? If it's the hardened 6061-T6 stuff i see widely available, you'll want to anneal it first before bending.

Holy shit, that's awesome. Too bad they are expensive. :(

I have access to one if you're up here. Not very good at using it tho... Techshop FTW!

Come on with the pics!! Although, Sav might prefer in your own thread so you don't hijack his. His/your call.

I know someone else is about to post v-mount pictures very soon too.

Yeah I'll start a new thread :) Threadjack over.

Sav -

If you have access to a welder, weld bosses on tabs onto the side panels, after you have tapped them. Then bolt the lower plates into place with a rubber gasket between the pieces.

- L

Sav, I bought some extreme weather ducting tape at home depot today, might wanna look into it. I'm using it to tape some insulation to the tranny tunnel to control heat, but you might wanna think about sealing all your ducting with it. Not only will it hold up to the heat, but it'll blend in and really create an air tightish seal. Freaking stuff was $20 a roll though, good to 260*

I will look into the tape, and I like the welded boss idea. I think I can just cut the metal with the boss attached and then bend it to avoid the welding, as well. The plan is to use rivets to assemble it all.

that's all splitime is using, tape & perforated plastic panels.

Savington's set-up is fine. "We're" running a similar set-up on Matt's car and with the "splitter panel" between the FMIC and radiator at 1" enough air goes to the radiator that it never went above 200* at WS in 101* heat...and that car makes well into 400whp.

previously mentioned tape, it's pretty badass.
https://www.miataturbo.net/forum/t36161/#post433042

Direct link to tape since it's on the 2nd page of that thread. I'll be picking up a roll tonight!

https://www.miataturbo.net/forum/t36161-2/#post433042

Good stuff. That's actual duct tape used on real mechanical ducts. Inspectors won't allow the stuff that's called duct tape on ducts anymore since it dries up & peels off after a couple of years.

Ah, that stuff. I had a roll for a long time, just finished it off. It's great for covering holes in the firewall, stuff like that. I always just called it metal tape :D

Anyone have a link to a cheaper price? It was $20, and I was worried I wouldn't find a cheaper price and just have to go back. I needed to get it done anyways.

I'm considering cutting a hole in my bumper between the blinkers to feed by oil cooler, so I am currently reading through https://www.miataturbo.net/forum/t14760-2/ thread. I'm slightly discouraged by people saying "it won't work" but from what I can tell, they're saying it won't improve cooling for the radiator and intercooler proportionally to the size of the hole in the bumper. The one thing it will do for me it give air to my oil cooler, which currently has none. Anyways, I just thought I'd share one of Sav's old quotes, I find it funny considering the work he's now documenting in this thread.

My plan + side ducting. Comments?

Your artwork sucks.

Sucks in air I hope yeah... :jerkit: