Turbo BP vs Low Power Engine Swaps
 

So hey guys I’ve had my Miata for almost 8 months now. I’ve been steadily learning how to push it to the limits while simultaneously increasing performance as well as safety mods. I plan on starting to track my car very consistently (I know the related costs). I want to have a goal in mind to start saving and setting everything up for that direction. I’m not a huge fan of insane horsepower but want a modest amount of power that will make it a killer on the track. The 3 options I’m contemplating are: turbo 96 bottom end with 99 head on E85 (thanks to the Midwest), K Swap unsure of E85, and the J Swap. I know this has been discussed before but the last thread I seen in regards to the Kswap was from 2015/2016. I was wondering if you guys had any updates on if the K swap guys have ran into any issues that only time would show. Is the Turbo BP worth it? I know it’s cheaper than the K swap but like I said I’m saving with a goal in mind and I put seat time above all else. Reliability and seat time are my main concerns. Thank you guys and any info is helpful. Also anyone have any news whatsoever about the J Swap? I’ve read all over forums and it seemed to me like everything that was said was all speculation because no one had physical proof of anything

What would I do? Chinese rods, Boundary Engineering race oil pump, Supertech light double springs, Pistons from 949racing (10 to 1 if only e85, 8.6 to 1 if using e85 and pump gas), stock damper, stock flywheel, 5 speed, ACT XTSS clutch, used FM or BEGi log manifold (or well built fabricated one), if used or budget limited then 2560 at a minimum - 2860 up to 2871 better (if buying new get the small EFR if budget allows), oil cooler, giant crossflow radiator (triple pass appeals to me), 3in downpipe and exhaust, shielding to keep the transmission cool, etc.

You aren't going to make 250whp out of a K swap without a lot of money building that motor as well. Or going turbo with it. Plus the cost of the swap kit.

Easy button is BP engine for the power level you want.

Most people who have issues with turbo miata's do not research enough about which setups work and which don't. Often times there will be folks who find a turbo from a junk yard and want to assemble some sort of kit around that, and it doesn't always work because it's unsupported or few and far between. Kmo25 has one of the best budget builds making good power and is what would be considered reliable. I've not had issues with my second built motor yet, and it's been 3.5 years of daily driving, tuned between 350-400whp. Mechanical empathy saves transmissions. Good tuners saves motors. Good fueling get's you to your power goals.

I personally think a VVT turbo swap into a 1.6L chassis is easy. It wasn't always that way and I can understand how intimidating it can be. it just takes time and research. K swaps are the new hotness (among ecotec, v8 and other swaps out there) but you could easily (and reliably) turbo your existing miata engine for the same cost. That being said, once the initial cost is achieved on a K swap, the ceiling is raised a lot higher in terms of power and deliverables. If it's your first run with miata's and swaps and turbo....then a K swap might be one hell of a learning curve.

These are just my opinions and no way am I an expert. There are a lot of forum guru/contributors on this forum who can make a more solid statement, but ultimately it depends on what you want.

Where in the Midwest are you? We can definitely throw you in the right seat of one of our cars on track this year if you want to experience a K24 swap first hand. We'll have a couple cars at the Gridlife festival and a bunch of other local events.

We've dialed in the K swap very well over the last 3 years. The current package is extremely reliable and works well with the factory drivetrain. figure 220whp for a stock k24a2 swap. If you want to see around 250whp, you'll need a k20a2 head, some big cams, and maybe e85. We made 248whp on 93 with a setup like this a couple years ago.

If you have specific questions you can hit me up via email anytime at sales@kmiata.com or call the shop to chat.

Stock vvt motor with boost to 220whp. Just enjoy that power level and not enjoy the car.

In the last 4 weekends of runtime, this is the sum total list of maintenance and repairs I have done to Rover, my 220whp turbo race car:

• Added half a quart of oil twice
• Changed the tires twice
• Installed new front brake pads/rotors once
• Changed an axle (no more pre-launch burnouts for me)

It's due for an oil change and front/rear pads, but I will probably stretch the pads one more day.

The car just sits in storage between events now. I won't pretend it's as reliable as a stock-power car, but it's as close as you're ever going to get. I keep an eye on things like bearing play and oil/coolant levels just like I would any other car, but it really is as brainless as an N/A car to drive at this point. It is also stinking fast everywhere it goes. 1:39s at Laguna, 1:53s at Buttonwillow, 1:56s at CVR CW on RC-1s.

If you use good parts and do your homework, a reliable turbo car is totally, 100% doable. No BS, no caveats, no excuses.

As a lot of the track guys will tell you, there is definitely a sweet spot for power that allows you to take advantage of the Miatas handling abilities without turning it into a "Can-Am-esque" point and squirt car.
The LFX and K24 swaps fall right into the sweet spot from what Ive seen, but its not exactly cheap. At the same time, a BP can be built to make this kind power reliably for less money, you just need to follow the MTnet recipe. Its all be pretty well sorta at this point.

EDIT:
My point has pretty much been covered already. So pretty much +1 to what was said above.

these cars.......


.......show me them

NA power requires RPM
RPM - "Ruins Peoples Motors"

A mild turbo setup can be very reliable. Trying to a spin a BP to high RPM have been proven to be pretty unreliable due to a still diagnosed vibrational/harmonic issue that seems to shake them to pieces.

Seriously, what does it really take? A manifold made out of SCH40 with good welds and gussets. Inconel studs and locking hardware. Good cooling system with ducting. Keep the rev limit around 7k.

Last time I was at mrls I was in multiple turbo miata's for many laps at a time throughout the whole day and the only one that broke was one guy's silicone coupler ripped.

This aint 2000-2010 no mo

Not to toot my own horn, but if you built a reliable turbo car before 2015, you did it with an engineering degree or an extreme amount of persistence. It was certainly doable, but it was not formulaic like it has become in the last ~2yrs or so. The fact that you can buy off-the-shelf components from Trackspeed and build a reliable turbo car in your garage is a relatively new thing.

Just curious how you chose 220whp. I know you know your shit, not questioning that btw. And a huge thank you for giving us all as much info as you do. My next upgrade turbo will be bought from you fyi.

220 is the generally accepted limit for a stock-rod BP when track days or racing is involved. It was also chosen out of convenience - Rover runs a pretty basic motor package, just a Stage 1 shortblock (rods/bearings/main studs) and a stock '94 head with a set of Supertech springs, and it made ~220whp at 10psi on CA91 with a conservative tune. The motor is capable of more but you could duplicate my motor setup with a stock longblock very easily and it would be reliable. The Stage 1 upgrades lift the power/rev limits from 220whp/7000rpm to 300whp/7500rpm.

So I've done probably 50 track days on a turbo Miata. Lots of problems/failures, but 3/4 of them can be summed up as brakes and cooling. Savington's radiator basically solved the cooling problems and I think I've *finally* got the brakes licked with his stuff too. The others are spread around the entire car -- hubs/bearings (none catastrophic, fortunately), bushings, tires, and transmission failures. Some random weird failures that I think just come down to my Miata having 100K miles, 75+ track days, and 200+ autocrosses on it.

The only actual motor failure I've had at the track was caused by a broken throttle body screw. Ignoring the effect of that on the 2560, the only actual turbo-related failure was a cracked downpipe on a ~2002 BEGI-built FM2 kit.

20 or so of those track days were at 250 rwtq on a stock bottom end too... :)

--Ian

Thank you guys for all the inputs! So I'll just go top to bottom. I don't plan on making 250whp on a K Swap. With a build its possible but I was saying that in any circumstance I dont want to exceed 250whp. I have a '09 STI with 300whp and even though its 1000lbs heavier, 300whp has been enough for me on the track. I completely agree that mechanical empathy and research will prevent failures. If the K Swap is maybe $1-2k more than a reliable turbo build, is it worth not having to deal with the slightly more complex turbo system in a BP? As well as the weight savings. Im not saying a K Swap drops 100lbs but accessories aside the K swap drops 30lbs over the BP and that doesnt even include the turbo kit. It might sound like im being biased to the K Swap but im just trying to make an educated decision with help from you guys before I drop $$$$ on anything.

Im in the Omaha area. Ive seen you guys are based out of Chicago Metro and have seen your customer support on forums and those have been major factors in my consideration. Do you have any events in the Chicago area in the coming months?

If i where ever to do it again, I'd K-swap. It's a newer motor, it's stout, it's a high performer with plenty of head room. I'd love to turbo one, but still wondering about speedometer solutions if using a bmw trans.

Im in the same boat. To be completely honest, with my 6258 the car can be driven in 6th gear down to about 20 mph. It really took a lot of fun out of drives. It made driving in the twisties a lot different. No downshifting, ever, and its not that exciting until triple digits.. It just isnt laboring at 3k rpm and is still slamming you into the seat. I think a K would be more fun.

two completely different uses you're describing. I agree that being able to beat on a car, explore limits of cornering, drive flat out 10/10 is a whole lot of fun.

Then you drive that same car daily or on flat/straight roads and it's so boring you fall asleep at the wheel.

Meanwhile a fat torquey turbo powerband will keep most below 20% throttle in the twisties because both the car and the driver are simply overpowered, which does get frustrating in the corners from time to time, but feels a-ma-zing daily driving and in "point and shoot" situations and suddenly the situation is backwards.

Why not have both? :D

I think you are underestimating the cost of a kswap or overestimating a reliable turbo build. You can literally buy the ~$5k FM2 kit, slap on some hood vents and an oil cooler and do all the HPDE's you want without issue. My car has been doing exactly that for about 7 years now. Oil and basic consumables are all it has needed. 220whp 1.8.

Kswap you're looking at about $10k+ realistically. Yes I'd love one, but I'd argue the cost isn't as close as you think for a recreational HPDE build. If we're talking actual racecar then things start to even out as a turbo bp needs a few more things to handle that level of driving.

K swaps used to be $10k+, but with the new parts available we've typically been getting people into 220whp k24a2 setups for around $8500. NAs are still a bit more expensive due to the fuel system. Although we don't see it often, you can still do a budget build and make 200whp by using a cheap S2000 intake manifold/throttle body and the stock TSX exhaust manifold.

Yeah. It sucks

Start doing some searches. The number of hits you find may give you enough information.

You like your engine on the end of a big lever, right?

I know Justin @ Thing 3 Racing (https://www.thing3racing.com/) runs a J32 in his AER/WRL Endurocar. User name slammed200.

Chiming in here from an endurance race team owner's perspective, reliability and seat time are huge. I also hesitate to recommend that ANYONE add a single horsepower when learning how to drive on track. Honestly, and this is always the last thing anyone wants to hear, power doesn't help you become a better driver. I'll get off my pedal-stool now since that's not what you asked but...

Now - about the J swap. I've had to completely redo just about every aspect of the J swap components to make it suitable for endurance racing and to my knowledge I'm the only one racing it regularly in these types of events. It's a hell of a car to drive now after all of that, smooth torques for days on days, but getting here wasn't easy at all. I'm not going to comment on the other options listed other than to say simple is sweet but you can swing that tradeoff based on your goals. Reliability and seat time are my main concerns.

There is also the ecotec swap that seems like a decent option. A little less desirable than a k series, but also it's a cheaper swap.

There's a really neat manifold swap that I'm a big fan of. It generates really good power. I'm pretty sure it allows you to run a turbo on your existing engine.

Sort of like a turbo manifold?

Have to agree. I daily the turbo. It's a hoot to squirt around and break the tires free at will.

For the most part, I track a 949 95R project clone. Pretty much SuperMiata S2 specification. Fantastic track car that never misses a beat.

Sometimes I'll borrow my daughter's '15 PRHT GT with all the bells and whistles for date night.

You can never have enough Miatas. Are the '19s out yet?

Hasn't flying miata been doing this since the mid 90's? Obviously TSE has refined and taken things to the next level with the EFR turbos, but I was under the impression that the full FM kits did this pretty handily.

go back and read threads even in 2006 and see the struggles track krew were having back then. "reliable" and "turbo" and "track" were not placed into same sentence

Trackspeed wouldn't exist if that were the case.

Turbo cars with FM kits were pretty reliable at low-ish hp numbers (say 200hp) or when not being driven all that hard, but when you turned the wick up they had problems with turbo nuts loosening as well as in the cooling and brake systems. Savington has been at the front of driving solutions to these problems with the inconel studs, the big, fat, multi-pass TSE radiator, and pushing big brake kits beyond the basic 11" rotor + Wilwood dynalite caliper.

--Ian

I'll chime in where I have both a FM2 2560 powered car and a J-swap with a J32A2.

Both are being run with 0 modifications to the engine itself. I can't talk about track reliability where I haven't gotten either on a track for long sessions where cooling would come into play and the FM2 car is now an Exocet so that makes it a very different animal. For street drivability in Miata form, they are both fun cars with likely similar power to wheels ~200-225 but they behave very differently.

The FM2 kit drives pretty much stock at low throttle then opens up as you get into it bringing the smiles to the face but I found that this isn't as beneficial on the street since pretty much any time you do it its for short stints or you are quickly breaking the speed limit by a lot. Highway on ramps though are a blast being able to open it up.

The J32 has tons of torque right from the start that is great for street driving since this is typically the range you are going to be in. There is something lacking from the top end though, even though its probably just as fast as a turbo motor at the same power, you don't have the explosive power once it spools and the great noises that go along with it.

This is why I have both :)

The cost I'd say is about the same.
I did the FM2 no electronics kit with MS, 750cc injectors and AEM Wideband. FM clutch/pressure plate and Fidanza Flywheel
J32A2 came from JDM engine distributor in NYC, kit from SuperFastMiatas and has a harness from RPM systems and AEM ecu, comes with clutch and flywheel
Both came to around 7k total, but clearly you could make a turbo system for cheaper where the J-series isn't getting much cheaper.

I don't believe the TSE radiator is multi-pass, but it is really fat.

"triple-pass, dual-core design provides significantly improved cooling over comparable radiators" Straight from TSE's site.

End tanks are indeed partitioned, this is looking 2/3 down the end tank on driver side. I'm surprised it's only tacked and not welded, I guess path of least resistance is still through the core?

https://cimg0.ibsrv.net/gimg/www.mia...b39f4a7eb1.jpg

I'm thinking of the supermiata one. Carry on.

Supermiata is only 31mm thick right? It is single pass though.

Here on a whim, but you're ATX as well and MultiPass. You get a cat :likecat: