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Learn me Turbo conversion Miatas
ddavidv PowerDork
10/29/16 3:08 p.m.
I've got someone interested in my E30 race car but would still like to have a track toy. I want something that handles really well like my E30 but has more power than my BMW's 167 horses while also being GRM priced. If anyone has suggestions outside "The Answer" I'm open to them.
That said, I've been browsing around looking at NA and NB turbo Miatas. Having driven a turbo NA Miata years ago I sort of know what I'm getting into. I don't give a hoot about SCCA classes so anything goes. I know Flyin' Miata is the go-to source but there are some other kits out there like Greddy that I have no knowledge of. I'd like to buy one turn-key vs building my own. Pitfalls, things to look for, etc would be helpful. I ignored Miatas for years while playing with German cars but now regret not keeping up to speed.
I also have a S197 V6 Mustang but the cost to make it anything approaching a fast and nimble track car would be ridiculous.
SVreX MegaDork
You could get in this one and drive :
KyAllroad UberDork
Be aware that turboing a Miata is the easy part if your plan is to do track days. Heat is the enemy and must be aggressively managed. Where a spec Miata may go on and on in 95 degree temps, the turbocharged time attack monster can do 10-15 minutes flat out before needing to pit and cool down.
Keith Tanner MegaDork
The GReddy kit has been gone for some time now. Its primary attraction was that it was cheap, now that has passed.
Yes, heat is the enemy. Not having AC and being willing to chop up your hood goes a long way. Our old "Track Dog" track car used to be able to pound around all day due to careful heat management. It's the dual duty street/track cars that have the hardest time. It's worth noting that backing off just a little big (shifting at 6k instead of 7k, for example) can have a big effect without a large drop in times.
Now, buying a used turbo Miata. You can get some great deals doing this. You can also buy some real turds. Here's what I'd keep in mind.
it's being sold for a reason. It probably has some unresolved issues which are contributing to the sale. Be prepared to go over the car top to bottom.
it's fairly common for them to pass quickly through several owners when the original modifier sells it. Partly because the new owners find it's not what they wanted, partly because something weird goes on and they can't fix it. So they tend to get rougher and rougher in a hurry, and the knowledge of what's been done tends to decrease at the same time. Again, be prepared to go over it top to bottom. It's pretty common for us to get an email with a photo of an engine bay asking "so, just what do I have here?"
if it has an aftermarket ECU, expect to have to learn how to tune it and sort it out. This is especially true of the cars described above. If you want full production car manners, you may have to change out the ECU as some of the older cheap stuff had a better reputation than was possibly deserved for anything but dyno runs. Also, ECUs age. The Link ECU from FM was a good unit with custom-written firmware, but the hardware is failing on them after 15-20 years.
if the car has some sort of jacked up fuel setup like a FPR with a stock fuel pump or a resistor on the coolant temp line, you'll want to deal with that.
if possible, get a car with an FM kit. I'm not just bragging on our brand here, it's because you can still get parts for it. Ebay specials, non-FM kits, small manufacturers - if you need something, you may not be able to get it. We support all of our turbo kits and have backwards compatible parts for them. The manifold/turbo/downpipe are all part of a system, so if you have problems with one you may have to change two or three if parts aren't available.
if possible, get records. Helps a lot when you're trying to solve a problem or get parts.
take a good look at supporting mods such as suspension or cooling. Good parts? Well installed? Or are the Mishimoto fans (run away from those) ziptied to the radiator? It's a good judge of how the car's been built and maintained.
They can be very reliable if built out of good parts with attention to detail and driven with some mechanical empathy. If they're neglected or abused - some people seem proud of breaking things, which I've never understood - they can be a constant headache.
BoxheadTim MegaDork
Keith pretty much summed it up, but just to reinforce his comments about the variable quality of turbo kit installs...
Quite a few years back in the UK, I bought a turbo 1.6 off a forum egg spurt. It had almost all the right bits on it and the guy was well regarded as being knowledgeable on the forum - OK, the turbo log manifold was half decent, the rest of the parts not so much - but the install was utterly atrocious. All the piping was the cheapest metal pipes from the local plumbing supply store (no, I'm not making this up) combined with the cheapest silicone hoses known to man, not held together by the cheapest hardware one could find on ebay. Not that it would've made much of a difference, because the genius installer didn't bead the piping, so running the car under full boost for more than a minute resulted in the hoses popping off.
Which was a good fail safe, because around the same time the cheapo fake Garrett turdo would start smoking like it had a four-pack-a-day habit.
The less I write about the emanage piggy back and its set up (it was a top-of-the-line emanage, so the problem was definitely the setup), the better.
These days I'd either turbo the car myself using a well known kit from someone like FM or another reputable source, or I'd buy one with an FM kit. The cheap E36 M3 gets really expensive when you get to limp it home everytime from your track days after only putting a couple of laps on it.
Interesting and appreciated. So glad Keith chimed in.
The one and only turbo Miata I drove was waaaay back when Corky Bell's book was first published had a highly modified Greddy kit on it with an added intercooler. The little thing ran like stink but never saw a track day so I had no understanding of the heat concerns. I know turbos make heat; don't get me wrong. The builder had cut some vents into the hood though. I was really impressed with the performance at the time and felt the car was fast but nicely balanced. I'd like something fast for track days but not any of the clumsy V8 cars nor high priced, high maintenance stuff like E46 M3s. A turbo Miata seemed like a great solution. I do have reservations about the quality of worked performed by other backyard mechanics but most stupidity has visual cues as soon as the hood is raised.
lotusseven7 New Reader
What about a V-8 Miata?????
Turbos have come a long, long way since Corky's book was published, and it's got stuff in it that's just plain wrong as well as highly outdated.
V8s have their own issues, mostly due to the fact that you're working the rest of the car really hard. If done well, the drivetrain is bulletproof as it's understressed. But you're putting a big load on brakes, wheel bearings, axles and suspension parts. They're also usually more expensive. There are a lot of sketchy home builds out there as well, but also some really really well done home builds.
Making power makes heat - if you double the amount of power in a car (by any method), you'll double the amount of heat it produces. You have to get rid of that. With a turbo system (and a proper supercharger), you also have an intercooler that's probably mounted in front of your radiator. Plus in a turbo, you've got the heat load coming from the water cooled turbine. The heat concentration at the turbine can also cause localized heat problems such as loosening manifold bolts and melting master cylinder reservoirs.
If you read some forums, it'll be made to sound like an insurmountable problem. But a lot of that is dick swinging. It's viewed as somehow wrong to pay attention to your car and to practice mechanical empathy. This attitude often goes along with people who have to win track days. If you don't have to win the day and you want to have fun, then it's quite possible to drive within the (quite elevated) limits of the car and really enjoy yourself.
10/29/16 10:11 p.m.
In reply to Keith Tanner:
Assuming a quality build, would you recommend a turbo Miata or a V8 Miata for his application?
Stefan MegaDork
I'm not sure a track day/street capable V8 Miata would be GRM priced, but then I'm only familiar with FM conversions and the kit parts aren't cheap. They are worth the money though.
SVreX wrote: In reply to Keith Tanner: Assuming a quality build, would you recommend a turbo Miata or a V8 Miata for his application?
I really like the way an LS3 Miata has a bombproof drivetrain and no cooling concerns - LS3 cool well, and there's no intercooler or turbo heat load. I also personally prefer the feel and massive amounts of torque. I drive around turbo Miatas the way that turbo Miatas drive around stock Miatas My consumables are high (for a Miata), with a lot of fuel and tire consumed in a given session. But it's a stupendous experience that does not grow old. Given the choice, independent of budget, I'd go with the V8. My track Miata is a V8 and my street Miata is a turbo, which is a good way to go.
But it's impossible to separate budget from the decision. Assuming the turbo car is a typical 250-ish hp setup, it's significantly less expensive than a good V8. Figure a factor of 3 or more. If you're looking at the 400+ hp range, it's all about the V8. But that's not the application under discussion, so the turbo is the way to go here. You'll get a lot more car for the money.
I've got a lot of seat time on track in turbo Miatas. They're fun, no question. You can keep them together. They're quick and a good mix of challenge and friendly.
codrus SuperDork
10/30/16 4:18 a.m.
I've had 3 different generations of FM turbo hardware in my Miata over the last 15 years or so, have done a lot of track days on them, and I have a few thoughts.
For much of that time, I was battling cooling and brake problems. Before 2010 or so, the best off-the-shelf solutions on the market for those issues were not adequate for sustained track use at 250+ rwhp levels. That has changed, there are bigger and better brake kits, off-the-shelf brake duct packages, multi-pass radiators, coolant reroute kits, turbo attachment hardware with improved metallurgy, etc. The cooling system in my car now is working very well, the coolant temperatures are stable at 95-96C while making 340 at the wheels. The brakes are also working well, although consumable life dropped from 4-5 track days to about 2 track days when I went from 290 to 340. I've made a few more tweaks, hopefully I can get it back to the 4-5 track day level.
The one thing that hasn't really been solved for high-power turbo Miata use at the track is transmission strength. The V8 conversion doesn't have that problem, because it includes a T-56. There are folks working on T-5 adapter kits for the Miata 1.8, but nothing you can buy and bolt on just yet.
Dumb question but I'll ask it anyway...does a turbo Exocet suffer from the same issues? With that car being lighter and a barely covered engine bay I'm thinking it would cool vastly better.
10/30/16 10:26 a.m.
When I'm talking about turbo Miatas, I'm usually talking about the common 200-250 rwhp ones unless stated otherwise. That's the point of diminishing returns. Cars like cordus' are outside the norm, and start to really stress the drivetrain as well as have even more heat difficulties. At 250 rwhp, the stock trans can fail but has a decent lifespan. At 340, you should keep a spare on the trailer.
As for the trans, I'm meeting with someone at SEMA next week who's come up with what looks like a very interesting solution. We'll see. We've got a T5 Miata bellhousing at the shop and have for years, but it's not a great option.
Turbo Exocets cool really well. Not due to the weight (on track, the atrocious drag balances that out) but they have massive airflow through the rad and don't have A/C. Our shop turbo Exo doesn't have any concerns with temps at all. They're also easier on brakes and tires - that IS the light weight.
Knurled MegaDork
Keith Tanner wrote: If you're looking at the 400+ hp range, it's all about the V8.
Guy I used to work with had been running 40psi in a BP. ("The LS2 coils don't work well over 28psi so I had to switch to IGN-1A coils") He was apparently changing head gaskets like most people change their socks. He has an LS1 in the pipeline, I don't know if it is going to be turbocharged or not but knowing him, it will be turbocharged sooner or later, probably sooner than later
Keith Tanner wrote: As for the trans, I'm meeting with someone at SEMA next week who's come up with what looks like a very interesting solution. We'll see.
Is this a stock-case solution or a bolt in new parts solution, he asked pointedly?
I have most of the bits to throw a T5 in the RX-7 and I have everything I need to bolt a T56 up to it except for the actual transmission, but there's something nice about stock-ish parts, as problematic as the smoothcase can be.
200 HP in a Miata is plenty for me. I'm not interested in pushing the envelope to see how much power I can build. I just want a fast, responsive car.
You've given me a lot to think about.
This may not be the answer after all. Problem is I don't see many enticing alternatives in the bang-for-the-buck price range I can find turbo Miatas for. I also like the affordable tires/brake pads/etc aspect. Won't get that with a Corvette or Mustang...or Porsche.
200 hp is pretty bomb-proof.
The new trans is from an alternate OE application and used parts are available. We'll see if it's plausible.
Keith Tanner wrote: 200 hp is pretty bomb-proof. The new trans is from an alternate OE application and used parts are available. We'll see if it's plausible.
Looking forward to hearing about alternate transmission options. :)
One comment about the "200 hp is enough" thing. My experience is that for most people it starts that way, but it rarely stays that way. More power is seemingly just a tweak of the boost controller away. A better intercooler adds another 5-10, then a 3" exhaust adds 10-15 more, plus better spool. Now the injectors are the limit, etc, etc. After a few years "200hp" becomes "250hp", then "300hp" and on it goes.
You say that, but I'm still running my 2554
It is true, though. Part of the secret to keeping a turbo Miata together is resisting the urge to give it just a little more power. Although from a professional viewpoint, I strongly encourage this behavior.
Kreb UltraDork
David: If all you need is 200 HP, what about the K24 swap? That should be lighter than the Turbo Miata, less maintenance, and 220 WHP is a cinch.
Or I could just buy an S2000, couldn't I?
Two problems with that: One, the ultra-rev happy Honda engines don't appeal to me and Two, how many of those already converted cars are on the market? I haven't come across one. I'm too old and lazy to take on something like that myself. That ship has sailed, as they say.
V8 RX-7? How common are those things?
icaneat50eggs Dork
Norotors.com Always has a few for sale.
I'm intrigued because v8 swapped nd rx7 Are usually cheaper than v8 miatas
MrJoshua UltimaDork
icaneat50eggs wrote: Norotors.com Always has a few for sale. I'm intrigued because v8 swapped nd rx7 Are usually cheaper than v8 miatas
Assuming you mean FC-They aren't that different in weight, drag race better, and have more room to fit rollover protection that isn't right on your helmet. They don't feel nearly as tossable to me though.
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