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Turbo BP vs Low Power Engine Swaps

 
Old 03-18-2018, 11:30 PM
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Default Turbo BP vs Low Power Engine Swaps

So hey guys Iíve had my Miata for almost 8 months now. Iíve 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. Iím 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 Iím 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 itís cheaper than the K swap but like I said Iím 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? Iíve 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
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Old 03-18-2018, 11:36 PM
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I would also keep the stock Miata trans and diff. I wouldnt go past 250whp since I feel like thatís more than enough for me on a track
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Old 03-19-2018, 07:30 AM
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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.
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Old 03-19-2018, 11:45 AM
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So you believe in the reliability of a turbo Miata? I know build and quality parts are the biggest factors but I just donít know about throwing a couple thousand at a motor that was engineered back in the late 80s/ early 90s. Do people have a lot of issues with turbo Miatas? Has anyone also heard any good or bad about the K swap
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Old 03-19-2018, 12:16 PM
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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.
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Old 03-19-2018, 12:19 PM
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Originally Posted by Chr1s7ian View Post
So you believe in the reliability of a turbo Miata? I know build and quality parts are the biggest factors but I just don’t know about throwing a couple thousand at a motor that was engineered back in the late 80s/ early 90s. Do people have a lot of issues with turbo Miatas? Has anyone also heard any good or bad about the K swap

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.
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Old 03-19-2018, 01:55 PM
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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 [email protected] or call the shop to chat.
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Old 03-19-2018, 01:57 PM
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Stock vvt motor with boost to 220whp. Just enjoy that power level and not enjoy the car.
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Old 03-19-2018, 02:25 PM
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Originally Posted by Chr1s7ian View Post
I know this has been discussed before but the last thread I seen in regards to the Kswap was from 2015/2016.
Really, 2016??

You apparently did not search very hard.



I would much rather drive a 140-150whp VVT engine'd car then a 220whp turbo car and all the extra reliability and durability headaches.


VVT swap, get the head shaved to bump compression, do I/H/E and MS3 and enjoy ~150whp with E85.
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Old 03-19-2018, 05:50 PM
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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.
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Originally Posted by codrus View Post
Basically I've come over to the camp of "If something is a reliability problem on the track, just ask Andrew and do what he says".
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Old 03-19-2018, 08:52 PM
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Originally Posted by Savington View Post
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:.
And to replicate you're set-up one would have to pay 4-5x the cost of a 150whp VVT set-up? More?

And lets not pretend you didn't have some teething and overheating issues...i.e. couldn't run a full 30 minute session in 90 degree heat without overheating.



OP - Turbo track setups are better than ever. As Savington has pointed out, a 220whp turbo setup can be very reliable and durable, but it takes a lot of work and a whole lot of money, especially if you have to shell out $$$ for a Trackspeed kit. Luckily, there should be a track worthy and much, much more affordable option on the market soon. Still, if it were my money I'd go for the cheap 150hp and spend the rest on track time. Lots of it.
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Old 03-19-2018, 09:17 PM
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Originally Posted by Efini~FC3S View Post
And to replicate you're set-up one would have to pay 4-5x the cost of a 150whp VVT set-up? More?

That you would rather have less power and spend less money has little relevance here. The comparison being discussed is between a turbo BP and a K24.

The K24 is $1-2k more expensive and roughly 2x the number of man-hours to complete. The benefit is a simpler car with N/A engine characteristics (higher revving, better throttle response, less mid-range torque).

The turbo BP is cheaper, less labor-intensive to build, and has an objectively better powerband and more headroom to grow into higher power levels. For similar parts+labor cost, the 220whp K24 would compete against a ~280whp turbo BP.

I have played with both setups, they both have pros and cons. Much like the Rotrex vs. Turbo debates, in my experience, there is minimal overlap between the customer base. Once you distill down to what characteristics are important to a specific customer, the correct build path reveals itself pretty quickly.

And lets not pretend you didn't have some teething and overheating issues...i.e. couldn't run a full 30 minute session in 90 degree heat without overheating.
Sure, but those issues are now fixed, and I coach customers all the time on how to solve those same issues before they ever crop up on their own cars. That's sort of the entire point of my racing and product development program. It would be petty to fault me for sharing those development notes with the community as a whole.
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Originally Posted by codrus View Post
Basically I've come over to the camp of "If something is a reliability problem on the track, just ask Andrew and do what he says".
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Old 03-19-2018, 09:41 PM
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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.
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Old 03-19-2018, 10:04 PM
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Originally Posted by Efini~FC3S View Post






I would much rather drive a 140-150whp VVT engine'd car then a 220whp turbo car and all the extra reliability and durability headaches.

these cars.......


.......show me them
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Old 03-19-2018, 10:30 PM
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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.
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Old 03-19-2018, 10:36 PM
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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
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Old 03-19-2018, 10:43 PM
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Originally Posted by 18psi View Post
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.
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Originally Posted by codrus View Post
Basically I've come over to the camp of "If something is a reliability problem on the track, just ask Andrew and do what he says".
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Old 03-19-2018, 10:45 PM
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Originally Posted by Savington View Post
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:
Just curious how you chose 220whp. I know you know your ****, 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.
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Old 03-19-2018, 10:54 PM
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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.
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Originally Posted by codrus View Post
Basically I've come over to the camp of "If something is a reliability problem on the track, just ask Andrew and do what he says".
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Old 03-19-2018, 11:11 PM
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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
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