GRM Exclusive Reveal: Exocet Spec-A

Warren v wrote: I wonder if Mazda put variable durometer rubber bushings in the lower control arm as a way to control toe under lateral load...that might also help explain why Miatas are so prone to wheel hop...

The different bushings do have different durometers for some passive rear wheel steer. Mazda made a fuss about it back in 1990 when rear wheel steer was cool. The wheel hop is, I believe, front/rear.

Guys keep adding great info to this thread as I'll be rereading all this when I can get back to finishing my Exocet. I'm trying to get my barn up to spec so I can finish the Exocet (it's on a dirt floor with no lights in there). Cement contractors giving me heart attack with price for whole project. So it looks like I'll be learning how to excavate, grade, add crushed stone, poly, then do my own rebar/remesh shield and hire them to do only the pour and finish. That'll save me several thousands but probably break my back in the process. Anyway I at least get to go run the BRZ at the Glen this weekend with NASA TT (yay!).

For those of you (Keith, Warren, anyone else?) who have driven your Exocets on track, which brake pads are you using? I'd imagine the idea of a true dual purpose street/track pad becomes more viable with the significant weight reduction.

We've been using the FM Little Big Brake Kit in the 10" size, and I think it's what Exomotive has on at least one of their cars. Pads are wilwood E.

Keep in mind that kinetic energy is directly proportional to weight, but proportional to the square of velocity. So we ran the FM Big Brake Kit (Stage 2) on the high hp XXXocet. Don't recall pads, it'll probably need two compounds.

Keith Tanner wrote: We've been using the FM Little Big Brake Kit in the 10" size, and I think it's what Exomotive has on at least one of their cars. Pads are wilwood E. Keep in mind that kinetic energy is directly proportional to weight, but proportional to the square of velocity. So we ran the FM Big Brake Kit (Stage 2) on the high hp XXXocet. Don't recall pads, it'll probably need two compounds.

Ahh yes, good old 1/2 MV². I was thinking the drag to hp ratio would keep top speeds pretty close to that of a Miata with similar power on higher speed tracks. Roughly 600 lbs less at the same terminal velocity = the brakes doing less work. I have some different pads laying around, I'll just have to experiment a little. As always, thanks for the info.

It's also worth considering that the brakes see a lot more airflow than on a Miata.

Slosean wrote:

Keith Tanner wrote: We've been using the FM Little Big Brake Kit in the 10" size, and I think it's what Exomotive has on at least one of their cars. Pads are wilwood E. Keep in mind that kinetic energy is directly proportional to weight, but proportional to the square of velocity. So we ran the FM Big Brake Kit (Stage 2) on the high hp XXXocet. Don't recall pads, it'll probably need two compounds.

Ahh yes, good old 1/2 MV². I was thinking the drag to hp ratio would keep top speeds pretty close to that of a Miata with similar power on higher speed tracks. Roughly 600 lbs less at the same terminal velocity = the brakes doing less work. I have some different pads laying around, I'll just have to experiment a little. As always, thanks for the info.

You're assuming that your speed between corners is drag limited. That might be true for turn 1 after a long straight, but not for shorter straights where the Exocet will have faster corner exit speeds and more acceleration.

FYI, rough guide learned from Laguna Seca - the Exocet with a stock 1999 engine has roughly the same acceleration in 4th gear as a Spec Miata.

In reply to Keith Tanner:

This is true, I am more focused on the higher speed 4th gear straights where speed would be mostly drag limited, perhaps too much so. Like I said, I'll just have to try the different pad compounds I have now and make a determination from there.

Warren - have you guys collected any lap times yet from local tracks? I'm think that a stock-motor Exocet would be extremely quick at AMP; less so at Road Atlanta.

Last time I was there, the Spec Miata record was a high 1:38 (slicks, obviously).

Here's what a lazy 1:28 looks like at AMP: https://www.youtube.com/watch?v=YfWkiB7f8Yk

Turbo is making 220, he's coasting a lot before the braking zones, and those are street tires. Also, passenger! I think a time-attack style lap on A6s would be close to 1:20 if not better.

Warren,

I don't recall any mention of the grill on the new style nose. Are you guys working on it?

In reply to ashneyder:

Obviously each builder has the final say, but I would discourage a grill or any sort of mesh covering on the intake. No matter the thickness, it will reduce radiator effectiveness. Even stock-power Miatas have seen overheating issues from mesh grills, even "high flow" meshes.

While the Exocet doesn't have as much of a problem with extraction, every little bit of airflow helps. Tripping up that nice, laminar flow into the radiator is going to reduce efficiency.

If you would like to install mesh, it is easy to find your desired style, buy a small sheet, trim it to the shape of the intake, and adhere it to the backside of the fiberglass with polyurethane adhesive.

In reply to Warren v:

My concern is about road debree damaging the radiator.

In the Miata world, everyone who runs a grille has a story about how it's saved the radiator. Meanwhile, the guys who don't have grilles don't seem to have problems with radiator damage. Go figure

It can make a considerable difference to the look of a car like the Exocet, though. The one on my Seven really improved the look. Based on what I've seen of Exocet cooling so far, I wouldn't worry about the effect on airflow. They seem to be pretty much immune to temperature.

Afore

After

How it's built. Wire perimeter frame with mesh welded on, bolted on via studs.

WOW Keith, the grill gave you THAT much power! I want one!!!!

Just kidding looks very nice...

Warren or Kevin,

Do these radiator mounts (guides.exomotive.com/hc/en-us/articles/203092956-2014-Exocet-Radiator-Mounts) now come with the kit, or is it a separate option?

They come with the kit now. Remember, they only work with NA radiators. If you have an NB donor, it's probably due a radiator anyways, so you might as well get a cheap OEM-style replacement NA radiator. Many swear by the Mishimoto radiator, too, if you want the extra looks of an aluminum radiator without the cost of a real crossflow.

Thanks Warren. I'll make sure I'll get an NA replacement. Do you have any idea how easy it would be to mount NB fan on NA radiator?

What are you guys doing with your donor tubs? Selling them for scrap metal? Is there any kind of market for a stripped Miata tub if I were to advertise it on Craigslist?

NB fans have different mounts on the bottom. I think you can do what you need to do with a small 90 degree bracket.

Shell value depends on where you live. Around here, they're worth scrap metal value.

So if you use a NA radiator with a NB engine do you need NA or NB radiator hoses?

In reply to tony_soprano: If the tub is in nice shape, there's probably a spec miata guy that could use it. Mine had some rust in front of the rear wheels so I just gave it away on Criagslist. Sell the hood, trunk, doors, etc..

ImprobableConstruct wrote: So if you use a NA radiator with a NB engine do you need NA or NB radiator hoses?

There's no significant difference. The inlets and outlets are in the same place. I'd recommend an NB lower hose because it's one piece.

Are customer who have already taken delivery of their chassis now receiving their bodywork in 'large numbers', or are most still waiting? What about fenders ... are those now being delivered?

In reply to einy: Ordered last October, kit shipped in April, haven't seen bodywork yet. Good thing we're taking our time with the build...