There is a whole lot of power between 250hp and 400hp. At 300rwhp Miatas are legitimately fast cars. At 400rwhp they can be quite dangerous if you're not careful. The wheelbase is short, the tires are relatively skinny, the car is very light, and the chassis is not that stiff without a full cage. All of these things add to overall instability at high speeds and horsepower. If you don't want to constantly be tinkering on the car fixing stuff that breaks, I would stick with a 6258 and 300rwhp.

I have a 7163 on my car with a tubular hotside and fully built motor. Even at wastegate pressure with a 14psi spring the car pulls really hard. Spool is slower than normal due to no ebc and I'm probably only pushing somewhere around 300rwhp based on Soviet's 6758 dynos but it is still properly fast. I will be turning up the boost to 21 psi once I get the car sorted and get bigger injectors. At that point I expect more **** to break.

 

Go the other way. Start with a 6258 and upgrade if you really want more than 325-350whp someday. The 6758 is a direct replacement and uses all the same parts (IC pipes, intake, oil/water lines). You actually don't even replace the turbine housing, just the CHRA and the compressor housing.

 

How in the hell does an 18 year old have 10g's to spend on ****?

 

Main reason to start with a 6258 being to break less things? I believe they were the same price at TSE.

 

It doesn't make much difference either way, I suppose. Most people who think they want 400whp hit the 300whp mark, scare themselves once or twice, and decide that 300whp is plenty. A few crazies get to 300 and decide that 400 is still a good idea. If you think you'll be in the latter category, go straight to the 6758. I suggest the 6258 because it's the better option for most people, and for the few that end up wanting more, the turbo upgrade is a very easy thing to do later on. That's one of the nice features about my parts - you don't have to commit to the big turbo now, but buying the small turbo today doesn't mean throwing away a bunch of parts tomorrow.

 

You can also pick up used 6758's for a good bit off retail. I know I have gotten 2 around $1000 or $1100 or so. Between selling your 6258 and a used 6758, you won't be out a ton of money.

 

300 hp is pretty insane, and requires wayyyy more self control and respect than I had when I was 18. You will be at triple digit speeds in less than 9 seconds.

PLEASE be carfull dude. Respect those around you, public property, your passengers and yourself. Respect the powa.

 

If your "guideline" is the fact that you've built a fairly decent bottom end and don't want to "waste" it on a measly 250whp then consider that you've created a solid foundation for whatever you might throw at it in the future. Your quest to go straight to "insane" is ill-advised at best.

You're 18, and (probably) haven't experienced 400HP in a Miata - why try to kill yourself so early? Why not ease yourself into the madness one step at a time - you might find (as others have stated) that you'll plateau somewhere shy of that goal. Get experience at 200-250. When you master that, take a leap to 300. If you haven't scared the crap out of yourself, then "graduate" to the big leagues. At every step you should gain useful insight, experience and (hopefully) respect for the beast you've created.

 

What people mostly dont see that these cars are light. a 400 hp Miata i think is the same as a 700hp supra. A 300hp Miata is comparable to really fast cars like M4, RS4 etc

 

The amount of trouble and retarted things I did with a 170hp acura when I was 18 cannot be publically spoken about. And I was more mature and responsible than most 18 year olds.

Part of me says, *** YEA 400HP BRUH!!!! But the responsible parent in me agrees with Ryans pit of monies. Just think twice when you get in this car regardless of which turbo you choose....

 

OK, so he's already got some sunk costs, but if the target is 400 hp, at what point do you just say fuckit and go LSx?

 

You don't go LSx just for the peak power.

 

There is 1 single reason I don't have an LS in my car. I am way to god damn impatient to save up the $15k to do it properly. I have well over what it would cost to do the swap in my car. The difference is that amount of money has been spread out over nearly 10 years and has allowed me to enjoy the cars at various power levels since then. If I was more sensible, could save up, and was for sure 400+whp was my goal, then I would have an LS swap.

 

You do it for the 200lbs of extra weight, the cooling issues, and the oiling system issues, right?

 

LFX?

 

OP, you're nuts if you do anything other than the TSE kit. do not stop at BEGI, do not stop at FM, do not collect $200. Go straight to the TSE website and click the buttons on a 6758 kit.

if you cannot afford to go click that button, then stop wasting our time -- that means you cannot afford to build a high-HP miata.

 

On paper it makes sense, but for whatever reason, it does absolutely nothing for me. Not sure why, but the LFX just doesn't give me the tingles.

 

I'm in the same boat.

For me, it's that it's pretty much the same cost and effort of a V8 for power levels that are within reach of a turbo BP, unless I'm missing something.

 

Definitely feeling the TSE kit over anything else. If i were to find a used turbo for around 1k, I wonder if i could get only the manifold from TSE. That would be groovy. I can't afford to click the button yet, but when I want something bad enough, I make it happen (hence the crazy goals). When I sell a few things and after a couple paychecks, I'll go to town buying turbo parts. My dad is picking up a 270whp on the 23rd. I'll use that as my opportunity to get used to that power. I have a feeling I'll get the bug to go big.

 

Make note: If you buy the TSE kit, you're getting a great deal on the turbo as well. If you're buying the TSE setup, just buy the whole setup. You could probably save a few pennies here and there but it won't be worth it.

Unless you just love building stuff and experimenting and breaking ****. I'm not a fan, myself.