Have had this 1997 Miata for almost 5 years now. Enjoyed it stock for several years but was bit by the turbo bug. I wanted to take my time and have lurked here and other sources for about 3 years now. The car is still stock now, and after taking a break from spending time and money on it due to moving around and buying my first house I am determined to have all the parts I need by the end of this year for me to install over the winter.
The car is mostly stock but I have done a couple of things to it to prepare for the turbo to go on:
-Installed aftermarket water temp, oil pressure/temp and afr gauges
-3in exhaust from the cat back
-Deleted A/C, charcoal canister and windshield washer system
-FM stage 1 clutch
-10lb flywheel
-Coolant reroute
-Supermiata crossflow radiator with the FM one piece lower hose
-A/C fan runs in tandem
-Running car on 93 octane and Rotella T6
-Gearbox oil and torsen diff oil changed to redline

At this point I am looking for a suggestion on the route I should go. My goal is around 230-250whp with as fast spool as possible. I want to keep the motor unopened for now but would entertain the idea of building it later. My initial idea was to replicate a FM2 setup with megasquirt so I have acquired these parts:
-Used GT2560r
-Taco manifold (which I have decided I will not keep and go FM instead)
-FM downpipe and elbow
-Oil and water lines used from a wrecked FM2 car
-Ebay intercooler

And planned to add:
-MS3 Basic + AIT sensor (possibly with CAN module also looking on suggestions if I need this or not)
-EV14 640cc FF injectors
-Catch can
-Inconel studs with locking hardware

However I keep hearing how amazing the BW EFR turbos are and am wondering if I should cut my losses now and sell the 2560r and FM exhaust stuff and go 6258 instead - which will require new downpipe components and possibly manifold. I dont mind the bump in cost as I will be acquiring everything I need slowly throughout the rest of this year. I guess my question is does the 6258 offer a significant increase in performance in the power range I am looking for (230-250) to justify this change in plans? If so what route would you suggest for manifold and downpipe combo?

Thanks in advance for any input. Also thank you for being such a great resource all these years. I am just starting my turbo project and feel like any issue I come across can be solved by reading through here. Thanks for doing all the hard work already!

 

I think so. I switched from 2560 to 6258. The EFR spools just as fast, maybe faster. Ill check some logs tonight. I would also consider the Kraken manifold if TSE is out of reach.

Im sensing a snowball. good luck

 

The better question is whether you're actually going to stay at 230-250, because most say that, and very few actually stay there. But no matter how you slice it, the only reason not to go EFR is cost. No other reasons.

 

This is true and there are some considerations you should make should you think that you want to go up in the future.

One of those things is injectors. The FF's are plenty fine, but if you think you're going to want to go bigger in the future, even if it's in a couple of years, then ID1k's might be the better bet for future proofing. If/when you do decide to build a motor, you can always just get a motor or shortblock in the future and build/assemble it on the side while you drive your car. Having a running car that you can enjoy kind of takes the stress out of getting everything running in a certain timeframe, though there are definitely those folks that want to stick to the motor that came in their car and just pull things and have them running together shortly. If you're theoretically going to be using a machine shop, then this may be a bad idea depending on how good/bad they are at getting things out the door on time.

I second RMP's comment re: getting the Kraken if TSE is too backed up if you're willing to spend the money for an EFR.

In the end it's both a cost:benefit thing and a time thing. Often a built motor is going to run into issues that a factory assembled motor won't and this can take time to navigate all those things, especially if you're new to things (as I am though I'm not sure about you).

230 feels plenty fast in a miata to be honest. The only reason I ended up going for a built motor and such was that I like tinkering and I wanted to learn how to do some of this stuff. If you'd rather spend that time driving the car, then that's totally reasonable as well.

TLDR: 6258 will be better than a 2560 even at low power levels, and a TSE/Kraken maniofold will be flow better than a FM/taco setup. The 6258 should be good to 325 wheel if not a bit more (thats when the efficiency starts to nosedive), so you're looking at about a 75hp benefit with a built motor if you want to stay 'safe' on a stock motor (~200-220rwtq).

 

Apparently I need to clarify this.

Our manifold was scratch-drawn in CAD in 2014. It is an original design, drawn for us under contract by a very talented CAD engineer in the LA area with extensive experience in both casting toolings and aftermarket automotive applications.

I'm unsure when Kraken's manifolds were designed. He joined the forums in late 2016, roughly 6mos after our parts were released to customers, and roughly 15mos after we began first article testing.

Their design is, erm, annoyingly similar to ours. So much so that I have had third party people point it out to me with all of the implications that brings.

I am glad the community has options, but it's still a little bit of a gut punch to me personally. Our manifold is still a better product by far for several reasons. Better casting process, better material, better testing and validation program, and far more real-world success in the harshest applications.

To clarify, we have absolutely nothing to do with Kraken, and we never will.

 

Decide now whether you are going to go cheap or for big power (a specific amount for a specific purpose) and stick with your plan. Otherwise you'll end up constantly pushing for more power, more reliability, more driveability, etc and it will never stop.

Then again, keep in that a 20 year old Miata is going to be needing new everything anyway, and this will be an endless treadmill of maintenance until you've replaced everything at least once. You might be able to fit quite a few mods into regular maintenance duties.

I would get the car running in factory condition and then do a mild boost setup on stock block/transmission. I would only go farther down the rabbit hole if you really enjoy wrenching and don't have responsibilities that will interfere with your hobby.

Past 15 psi I have traction problems galore. My personal falling is that around that mark you're getting incrementally more enjoyment for lots more money.

 

You have a solid build plan.

having owned a 2560r setup and now upgraded to EFR 6258, I will say you can't go wrong with either choice, if you are content with about 250hp. Which in a miata is no joke.

2560r is fairly happy making about 250-260hp. After that it's pretty much out of breath and that's when the EFR starts to shine over the 2560.

spool is similar between the two.

for example, my 2560 made 264hp at 17psi. And my new 6258 is making 300hp at 16 psi and it's happy to make these, not pushed hard at all.

it's a hard choice, but if do it once and do it right is important to you, I would go EFR.

another option is ditch the fm stuff, get a kraken t25 manifold and downpipe and use your existing 2560r. When you decide to upgrade to an EFR, all you need is a new downpipe, the manifold is the same.

 

So refreshing to see a new turbo miata with a solid build plan.

having owned a 2560r setup and now upgraded to EFR 6258, I will say you can't go wrong with either choice, if you are content with about 250hp. Which in a miata is no joke.

2560r is fairly happy making about 250-260hp. After that it's pretty much out of breath and that's when the EFR starts to shine over the 2560.

spool is similar between the two.

for example, my 2560 made 264hp at 17psi. And my new 6258 is making 300hp at 16 psi and it's happy to make these, not pushed hard at all.

it's a hard choice, but if do it once and do it right is important to you, I would go EFR.

another option is ditch the fm stuff, get a kraken t25 manifold and downpipe and use your existing 2560r. When you decide to upgrade to an EFR, all you need is a new downpipe, the manifold is the same.

 

'
+100. The above quote just really resonated with me. I went from a "budget build" to a semi built 99 motor on a 2560. I can vouch that i have replaced just about everything on the car at least once, partly out of necessity and partly because "if i replace this i might as well replace that" mentality. I also struggle now with the idea that maybe i just up the boost a little and if the turbo isn't efficient, maybe i get a new turbo. As mentioned above, it can be a serious rabbit hole if you're not careful. Its a fun game and If you have the money (and more importantly, the time) to go through the process then more power to you (no pun intended). Just wanted to echo the quoted comment from someone who has lived it!