The Targa Miata moves to the next stage

I thought it would be along those lines. In my case, I think there's a considerable amount of convection even when moving because the air going down the tunnel is HOT. I mentioned the temperature in the tunnel on my Locost already, there was no exhaust in that. It was all from the radiator and air heated up by the engine and exhaust before the exhaust went out the side of the car. I never noticed any real heat coming through the aluminum side panel with the exhaust on the other side, because it had lots of cool air blowing across it. In the Miata, I get that pre-heated engine bay air plus the radiant heat coming off the exhaust. Both cars already have hood louvers.

Interesting build.  How about an idea straight from the far side?  (No not the comic.)   A pair of ducts that run from from the front bumper area with the ducting running over the front wheels above the fender liners then cut back in and point towards the transmission tunnel.  For low speeds there could be in-line duct fans.  Like brake ducting, but to move cool air into the trans tunnel.  

And the magic of MS paint comes through again!  Let me guess, this won't be able to move enough air to have any real effect.  

Out of left field, I like it :) I would be concerned about two things - the ability to move enough fresh air into the tunnel to cool it, and the aerodynamic effects of pressurizing the undercar region.

But I was lying in bed this morning thinking, and an airgapped heatshield might be the solution. Just a piece of aluminum plate on some standoffs would do the trick. That's if I can find room in the tunnel, although it could also be mounted in the car for a particularly industrial (but less effective) look. Now, combine that with the fresh air injection between the plate and the tunnel wall and you'd have a fairly effective heat barrier. Okay, I may not duct air into it but I'm definitely going to look and see where I have room for a shield.

Keith Tanner said:

Out of left field, I like it :) I would be concerned about two things - the ability to move enough fresh air into the tunnel to cool it, and the aerodynamic effects of pressurizing the undercar region.

 

If you move enough air through the tunnel, it should create a low pressure area under the car.

I think that only works if you're pulling air out, not forcing it in. Basically, concentrate on extraction and then find a way to feed it cold air instead of simply pulling more air from the hot engine bay.

Which is going to be outside the scope of this project :)

For your floor texture issue look at airplane wing paint. It’s designed to allow traction for pilots to access the cockpit from a low wing. It’s durable, adheres well, and isn’t very heavy.

Keith Tanner said:

I think that only works if you're pulling air out, not forcing it in. Basically, concentrate on extraction and then find a way to feed it cold air instead of simply pulling more air from the hot engine bay.

Which is going to be outside the scope of this project :)

I don't remember what the rear of the car looks like. How well are you getting the hot air out of the tunnel?

No diffuser, just a cut bumper and a lot of ground speed. In track mode, it has a reasonably aggressive airdam and a flat underbody to the back of the engine bay so anything that hits the front of the car is basically going out the hood vents or out the tunnel.

How about side pipes a la Ryan Passey's LFX powered car? Gets the exhaust out of the tunnel at least!

No, I have structure under my car that would make that implausible. And remember, the entire thread is about making this more of a street car.

Fair enough. I suppose climbing over a hot exhaust pipe doesn't exactly serve the goal of increased comfort and streetability.

In reply to Keith Tanner :

Can I just take a minute to state how much I LOVE cut rear bumper miata for some reason? I even like when they do that "let's not beat around the bush and remove the whole damn bumper" mode.

cmcgregor (Forum Supporter) said:

Fair enough. I suppose climbing over a hot exhaust pipe doesn't exactly serve the goal of increased comfort and streetability.

THERE ARE ALSO NOISE CONCERNS

Keith Tanner said:

cmcgregor (Forum Supporter) said:

Fair enough. I suppose climbing over a hot exhaust pipe doesn't exactly serve the goal of increased comfort and streetability.

THERE ARE ALSO NOISE CONCERNS

What?!

accordionfolder said:

In reply to Keith Tanner :

Can I just take a minute to state how much I LOVE cut rear bumper miata for some reason? I even like when they do that "let's not beat around the bush and remove the whole damn bumper" mode.

I prefer having at least some sort of bumper, it looks a little more intentional than "I've decided to just rip this off because racecar". Same reason I have a Miata nose on the car and not one of the effective but hideous Supermiata style airdams.

I had to do some of the cutting on this bumper after I drove over my own wheel at Laguna Seca, it originally was a little less aggressively cut. Here's the original.

In reply to Keith Tanner :

I like it both ways honestly - I think some cutting in the rear makes the car less of a bean in my eyes? I'm assuming you're talking about that video where your rear hub said goodbye to your car going down the corkscrew? I haven't been brave enough to do any cutting on my silver cars rear bumper, I probably won't for a long time unless the point is forced. 

I've been chewing on the exact problem you've stated - while I like the cut rear - I'm not a fan of the Supermiata/Good aero front bumpers. I'm considering aero for my little silver car next season. I think they look especially wonky when they're two tone.

Keith Tanner said:

cmcgregor (Forum Supporter) said:

Fair enough. I suppose climbing over a hot exhaust pipe doesn't exactly serve the goal of increased comfort and streetability.

THERE ARE ALSO NOISE CONCERNS

I actually laughed out loud at this

I think I have a plan. I'm going to try DEI Floor and Tunnel Shield. It's 5mm thick, has a dimpled aluminum face and an adhesive back that's good to 450F. The alloy face should help with radiant heat and the interstitial insulation should help with convective. I might back that up with a bit of DEI's pipe insulation.

I may have to pull the trans to install it, but honestly it's not THAT hard to drop the engine/transmission combo out of this thing on the subframe. That'll give me the chance to give this poor, tired car a good once-over. The goal will be to get that done in a weekend, no MG-style months and months on the lift. So step 1 is to measure the amount of heatshield material I'll need and get it on order. Step 2 might be to see if it's possible to remove that Thermo-Tec Cool-It that I have on the tunnel already, but that's a separate job. 

In reply to Keith Tanner :

I used that stuff's little brother to make heat shields for the Torino From Hell.  It had a rack and pinion setup where the center link used to be, and the headers surrounded it top and bottom.  Worked remarkably well.

I did a little video thing on this car. Not my best work, but for those of you who like your pictures moving...

...and for those who prefer the more carefully considered written word instead of me babbling on with no idea of how bored my audience might be, here's the latest poop.

I've spent some time thinking about that dash bar. It has two things that make it wobbly - it's got a bend in the middle to clear the vents, and it's attached to a fairly thin plate at each end that's bolted to the structure of the car and cantilevered out. I have some spare roll bar tubing so I've decided to run a straight bar from side to side and weld it to some decent structure. I'll have to do some bracketry work to attach the steering column and provide mounting points for the dash skin, but that's not too bad. I will be deleting those central vents so I don't need the clearance there.

Here it is cut to length and just stuck in place. You can see the brackets I'll have to duplicate.

It will be welded on here. If it's not stiff enough, I'll add a brace that runs forward to the tunnel. The steering column actually has a second set of mounting holes that line up nicely with the new tube.

So yesterday, this happened.

Took me about 3.5 hours to pull, which is longer than I expected. I wasn't working fast and I was trying to make sure I found everything. This is still a very big engine in a small car.

Exhaust pipes. Swain coated stainless to painted mild (where the cats used to be) to polished stainless. And lots of O2 sensors :)

The Swain is not surviving well, unfortunately. It's spalling and coming off. Swain is not concerned about it. After I took this picture, I discovered there were big bare chunks on the other side.

Here's the state of the Cool-It inside the car. Not sure how I'm going to clean that up. Dry ice? That's the passenger's side right beside the seat.

Driver's footwell did have this gold foil. It helped but did not cure the problem.

Spent a fair bit of time cleaning up the tunnel. There was just goo under here. Lots of Simple Green and wipes and brake cleaner. I should note that this tub started as red, we must have color-matched the tunnel when the V8 was installed.

To be continued...

It took longer than expected to install the heatshielding. First was all that cleaning. I cut the material into smaller chunks so I could go section by section which worked well. The various rivets and protrusions coming through the tunnel made my life difficult as well. My goal of having the drivetrain back in the same day died when I ran out of steam and and didn't want to half-ass the heatshield installation. It's a pain in the butt to get back in here.

By the next day, I got to here.

I did cover up the brake line that runs through the tunnel, as it seemed like a good idea to shield it from the heat. The cut-off switch was left on the hot side because I could think of too many ways for it to go wrong for me to cover up big fat unfused electrical connections with a conductive material.

Before sticking the engine back in, I took a good look around. And spotted a small problem with a sway bar mount.

Make that two problems - looks like I'm stressing both sides of this car evenly.

So that slowed things down. I had to pull the radiator which means part of the over-the-top intake comes out, then I welded up some reinforcements for the brackets. I could bolt-on an off-the-shelf upgrade from, umm, Flyin' Miata but my welder was right there. Don't mind the booger welds where I tried to tack it to the frame. Bad ground, I think.

With that done, I started to reinstall the engine. Slowly and carefully, as there are a number of things that are difficult to access. I ran out of time to get it in today, but I'll finish the job on Tuesday. Good progress. Still trying to figure out how to deal with that existing heatshielding on the tunnel in the interior, though.

In reply to Keith Tanner :

Keith, is your plan to pull the factory dash support entirely? When I saw this pic

I assumed you were installing behind the factory bar and tying it into it with plates. Would solve replace all the mounts for steering, dash, etc.

I was thinking of pulling the factory bar. It'll be completely redundant, and those brackets are pretty easy to do. It'll open up more options for HVAC fitment  as well, I think.