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EXNINJA's kit car build thread

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Old 02-08-2018, 05:06 PM
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EXNINJA's kit car build thread

Some may know I own a Miata. Yup, gay. If you know that, you may know I want to turn it into an exo-car (less gay). The kit I want is called an Exomotive Exocet. It's like a DF Goblin, but using a Miata.



I've been saving for a few years now. Since I started saving, we've moved homes and had two more kids. It's been tough to save. This year is different. I've got a good stash saved up, but tax refund is going to be good and work is giving me a great bonus (thanks Trump). Time to be frivolous.

Originally I was thinking I'd build it with the 1.6 and get it running, then maybe boost if I felt like and then save some more for big V8 POWAA down the road. Like this:



What changed? A few months ago I moved the Miata to clean and organize the garage. I left it idling since it hadn't been run for quite a while. I cleaned for 30 minutes or so, then glanced at the car. The secret ingredient was leaking. The fan decided not to work anymore. I filled it with water and it started again, then I put it away. It still sounded fine, but the head is probably warped. This accelerated my swap schedule. I don't want to bother getting a likely-broken motor running in a new car, nor to all of the work and expense to get a good 1.6 going.

So why am I posting a build thread here? Because I've decided I want to put an Ecotec in it! I saw someone post a picture of their LE5 going into an Exocet and it actually makes a lot of sense. There's a Canuck company that has adapter kits for Miata Ecotec swaps. The bare-bones kit has motor mount adapters, transmission plate adapter, and an oil pan for a decent price.

While the V8 is tempting, it's a bit much. It's difficult to put that much power down in a 1500lb car. Then there's the cost. No way I'd get it bought this year.

If I stay below 250hp, I can keep the Miata trans and diff. I'm not 100% that I want to do that, because the gears are pretty short as-is. But that's the cheapest route for sure. I could get a taller diff pretty easily and cheaply if I want. If I go above 250, I'd be looking at getting an AR5 transmission and likely a Getrag rear diff, or splice in a Ford diff.

So I see three choices right now:
1 (cheapest): LE5/LE9 mated to Miata drivetrain
2 (2nd cheapest): LAF/LEA mated to Miata drivetrain
3 (send it): LHU mated to AR5

The LHU is enticing but gets pricey. I'm sure I'd be content with 250HP (when I add boost) on the 2.4L. But I could just send it.

So I'm still in the planning stage. I'm going to order the kit in 2 weeks. I'll have a few months after that to get things in order before it comes.
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Old 02-08-2018, 05:29 PM
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just ******* send it.

LE5 with a zfr6758 matted to a AR5
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Old 02-08-2018, 05:37 PM
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I can def get it going now NA and upgrade later.
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Old 02-08-2018, 05:42 PM
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Finally pulling the trigger, eh? I would go the 2nd cheapest route to get a feel for the project then upgrade later.
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Old 02-08-2018, 05:43 PM
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The LAF/LEA version? It would be easier to make 200hp NA and more control with boost, only drawback that I see is price. I need to price some of those motors.
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Old 02-08-2018, 05:44 PM
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CI seńior

...very much emphasis on "senior".
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Old 02-08-2018, 05:51 PM
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Old 02-08-2018, 05:58 PM
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thats really cool. how much of the miata does it use? just suspension and cradles, or does it use thing like the cluster, steering collum, seats, etc?

i agree with not wanting to run a v8. too much torque, too much weight on the front end. love the idea of the ecotec, its so light and power options are good.

now as for what combo thats a tough one. really i come up with a final power goal (and a realistic one) and work towards that. its always more money to go in and have to change the engine/trans/diff later down the road, let alone all the custom work having to be done twice. now keep in mind that if a miata trans and diff will hold 250 hp in a miata (2100-2500lb curb weight, plus occupants) itll hold far more power in this thing. however if your gonna be wanting 300+hp, id just go with an ar5 transmission from the start. for one, it bolts right up with no adapters, just the way gm designed it to. engine choice is up to you, however myself, id lean towards the non direct injected engines, they are just simpler, cheaper, and allow easier fueling upgrades. they also open you up to stand alone computer systems. the 2.2l is dirt cheap, toss in a set of aftermarket rods and pistons, along with valve springs, and your supporting 450hp. you can do the same with the le5, they usually arent as cheap to find. heck, can even keep them stock and keep the boost down, and if you happen to lift a ring land, in a weekend you can swap another engine in for a couple hundred bucks.

when i did my 944 swap i ended up building it for the ultimate goal, and thats 600 whp. already had the built motor, no sleeves or girdle, so its limited to 425-450 ish. i already had a manifold, small t3 turbo, small intercooler, megasquirt and fuel system, and i could have made around 350hp with all that stuff. in the future i would have had to built a new turbo manifold, new downpipe, new charge pipes, mount a new intercooler, redo oil lines, etc just to upgrade the turbo. i ended up selling it all and waiting till i could spend the money on the stuff for the ultimate goal, that way build it once and done. in the future i can build a girdled block, drop it in and turn it right up.
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Old 02-08-2018, 06:04 PM
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Awesome following
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Old 02-08-2018, 09:53 PM
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Originally Posted by ECaulk View Post
just ******* send it.

LE5 with a zfr6758 matted to a AR5
Holy wheel spin batman
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Old 02-08-2018, 10:07 PM
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Originally Posted by double clutch View Post
Holy wheel spin batman
Open wheel so plenty of space for a nice wide grippy tire and I'm sure you can adjust the suspenion so it will plant the weight to the rear wheels better
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Old 02-09-2018, 12:51 AM
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Thanks Sharkey.

I need to decide if I'm content with the 250hp limit. I think I am, for the same reason I don't need a v8.

I'm pretty certain the same limitation applies even though the chassis is lighter. Torque is torque. The lighter frame just means more acceleration, but the same power goes through the trans.

LE5s aren't too bad. They're getting them as low as $200 but usually around $500. They were in a lot of cars.

My first instinct was port injection. I should stick with that.

Oh, and it uses pretty much everything but the tub. Suspension, steering, seats, even gas tank if you want. There's not much to the kit other than welded tubes, a floor, and a hood.

Last edited by exninja; 02-09-2018 at 01:13 AM.
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Old 02-09-2018, 01:59 AM
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Originally Posted by exninja View Post

I'm pretty certain the same limitation applies even though the chassis is lighter. Torque is torque. The lighter frame just means more acceleration, but the same power goes through the trans.
it doesnt. there has to be load against it to cause it to break. if you decrease the load on the transmission you can input more torque without breakage. think about how the 3.82 ratio lnf transmission breaks 3rd gear, the 4.05 lsj trans can break 3rd but its not as common, and the 4.45 will take the most power. this is because the taller final drive ratio reduces the load on the pinion shaft and mainshaft.

in another example, a 3rd gen camaro/firebird t5 manual transmission will break in a stock car if you look at it wrong. those cars are 3500 lbs + and most have a 3.08 final drive. the same t5 transmission in a fox body mustang is 3200 lbs and usually had 3.08 or 3.27 gears, and they will take a bit of a beating making more power than stock. internally the transmission is no different ford vs chevy, its simply less load against the drivetrain that allows it to hold more power.
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Old 02-09-2018, 06:26 AM
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Build it with a good base so you don't have to do it all over again. Which ever motor you do invest in good components in the short block, even if that means you have to stay na for awhile. You can always turbo it down the road but at least you won't have to worry about the motor. Trust me I've been down that road too many times with v8's back in the day.
If you want to get it up and going quicker use the Miata trans and rear end, and keep your eyes open for a good deal on the beefier gm stuff you can purchase and set aside for install down the road. Don't skimp on a unreliable motor.
250hp in that would fly
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Old 02-09-2018, 08:25 AM
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Sharkey, interesting. I'll stick to 250 just cuz I'd rather not risk getting stranded. It's got 140k miles on it anyways, and I don't really know its history.

I think I'll get it running with this and be on the lookout for a good deal for ar5 and whatever rear I want. I haven't heard too many good things about the solstice getrag diff. I'll see though.
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Old 02-09-2018, 08:31 AM
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It would sound better with a screaming supercharger on it

But in all seriousness awesome project. I'm starting to think more and more if I get to that point I will just do a tube frame kit car instead of gutting and caging the balt. Mainly because it would be lighter and easier to work on.
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Old 02-09-2018, 09:38 AM
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Originally Posted by Sharkey View Post
it doesnt. there has to be load against it to cause it to break. if you decrease the load on the transmission you can input more torque without breakage. think about how the 3.82 ratio lnf transmission breaks 3rd gear, the 4.05 lsj trans can break 3rd but its not as common, and the 4.45 will take the most power. this is because the taller final drive ratio reduces the load on the pinion shaft and mainshaft.

in another example, a 3rd gen camaro/firebird t5 manual transmission will break in a stock car if you look at it wrong. those cars are 3500 lbs + and most have a 3.08 final drive. the same t5 transmission in a fox body mustang is 3200 lbs and usually had 3.08 or 3.27 gears, and they will take a bit of a beating making more power than stock. internally the transmission is no different ford vs chevy, its simply less load against the drivetrain that allows it to hold more power.
I thought the fulcrum of the pinion was a bit higher to help brace against the higher torque in the V8s? I'm sure I'm wrong but I remember reading about some of the difficulties in the power transfer and distribution that lead to these failing prematurely, and the idea was a higher balance point over the synchros for less flex on the material (or something like that).
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Old 02-09-2018, 09:51 AM
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Originally Posted by jdbaugh1 View Post
It would sound better with a screaming supercharger on it

But in all seriousness awesome project. I'm starting to think more and more if I get to that point I will just do a tube frame kit car instead of gutting and caging the balt. Mainly because it would be lighter and easier to work on.
I mean a TVS 1320 on a 2.4 would be damn awesome for auto-x and tight cornered road tracks
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Old 02-09-2018, 10:06 AM
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Honestly that whine is very tempting. It's basically built for autocross. The aerodynamics are pretty much garbage. As in, the drag coefficient is similar to a garbage bag.
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Old 02-09-2018, 10:26 AM
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Originally Posted by exninja View Post
Honestly that whine is very tempting. It's basically built for autocross. The aerodynamics are pretty much garbage. As in, the drag coefficient is similar to a garbage bag.
If you run a TVS1320 or zfr6758 it doesn't give two ***** about drag coefficient
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Old 02-09-2018, 10:38 AM
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even better, a TVS AND ZFR
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Old 02-09-2018, 10:52 AM
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I'll tell you I run a TVS for autocross and think it's perfect. I have more power than I can put down in most instances at even low rpms and instant. Should be able to but a bit more down now though with quaife LSD.
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Old 02-09-2018, 10:54 AM
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running a zfr you would be in full boost basically the entire time, and the ar15 can handle it. The boost curve on it is insane.
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Old 02-09-2018, 10:59 AM
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Great build. I'm partial to the direct injection turbo.

I don't hate the maiata. I think for what it is, it is a great roadster. It is one of those cars that I have on my want list.

I own a 2009 Solstice GXP. I bought it new when GM was tanking. Paid 21K and got double my GM money deal. It was too good to pass up. The car has 4000ish miles on it because it is just so impracticable to drive. No trunk. Top is a pain to put up and down. But it is unique and is ecotech powered.
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Old 02-09-2018, 11:17 AM
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I mostly put the gay part for ECaulk's sake

I agree, it's a fun little car. Just underpowered, esp the 1.6. Mine happens to be bent in a few places, so this makes a lot of sense to me. Taking out weight and adding reliable power is a super win-win.

I do like the simplicity of the LE5 vs DI. I'd have to reroute the oil cooler if I kept the Miata transmission. However, I have seen some issues with the flywheel adapter that they make. Ugh, I want to keep it simple. There's also a company that builds a rear diff adapter to mount the Getrag to the Miata subframe, but that piece alone is $1000. I'd have to fab one myself.

For now, it's LE5 NA with Miata trans and diff. I can still put light boost on it and have tons of fun. Supercharger can keep the same exhaust so that's more likely. More than 200hp and I'd be using up too many tires anyways.
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