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Login to post Forums » Grassroots Motorsports » So, turbo Miatas...how reliable can they be?

July 6, 2011 4:05 a.m. Racer1ab Reader

A few years ago, I sold my '95 supercharged Miata and have regretted it ever since. The only thing more impressive to me is a turbo NA Miata, and I've been doing a bit of shopping recently at the request of SWMBO.

Anyway, the car in question is a 1.8 Miata making around 250 horsepower at 12 pounds to the wheels and it's controlled by a Flyin' Miata Link system.

I'm aware 250 horsepower is kind of pushing the limits of the stock motor, but realistically, I don't drive that aggressively any more, so I'm wondering if the engine is living on borrowed time at these boost levels or is it only a problem if I'm at high rpm's for a prolonged period of time...say at a track day or something. The car still has a stock radiator, so I know I would have to address the cooling system before any real track time.

I don't have a lot of experience with the Link system, but did get to drive a car years ago with it installed, and was impressed you could adjust the boost with it. For daily driving, is it a smart idea to just go ahead and turn it down to 5 or 6 psi?

Anything else I should look for when checking this thing out? FWIW, the seller is incredibly knowledgeable and seems very honest about the car, so I'm certainly not looking at some half-hearted Greddy setup that's about to go wrong.
July 6, 2011 6:32 a.m. Dashpot Reader

In reply to Racer1ab:

For a fun street car - yes it can be reliable. For a track car you have some work ahead of you, much more than just a radiator. For now, do the normal pre-purchase stuff and make sure you get at least a compression check, and preferably a leakdown test too. If it passes those, the motor (and tune) is mostly good.

I wouldn't bother dropping the boost on the street if the tune's good, that's what you're buying it for. I've been running and racing an older FMII for over 3 seasons now, and have a decent idea of what's needed to keep it alive. PM me if you want the details and good luck with the purchase!
July 6, 2011 7:18 a.m. z31maniac SuperDork

Dashpot wrote: PM me if you want the details and good luck with the purchase!

If you have good, first hand info, share with all of us!
July 6, 2011 7:47 a.m. Autolex HalfDork

Paging Keith Tanner, Keith Tanner to the thread please...
July 6, 2011 7:56 a.m. 92CelicaHalfTrac SuperDork

On a healthy motor with a good tune, that thing is certainly not on borrowed time.

250whp is up there, and will be damn fast, but i wouldn't say that it's "pushing the upper" limits of the 1.8 BP. At least.... not by my definition.

I wouldn't bother turning down the boost for daily driving. Unless you want to be able to punch it a little without getting arrested in short order.
July 6, 2011 8:06 a.m. mndsm SuperDork

92CelicaHalfTrac wrote:

On a healthy motor with a good tune, that thing is certainly not on borrowed time.

250whp is up there, and will be damn fast, but i wouldn't say that it's "pushing the upper" limits of the 1.8 BP. At least.... not by my definition.

I wouldn't bother turning down the boost for daily driving. Unless you want to be able to punch it a little without getting arrested in short order.

Yeah, you'd hole the block and still try and turn up the boost, rods all flappin' in the breeze and whatnot. I know how you think.
July 6, 2011 8:19 a.m. Duke SuperDork

That car sounds remarkably like mine, though mine is blown, not turboed. Same ECM, approximately same power levels. Mine does have a big aluminum radiator, coolant re-route kit, and intercooler. The previous owner ran it at track days with very few problems. Although it spikes temperature at first, as soon as the thermostat opens, it stays rock steady around 185 under just about all conditions.

I usually shift at 6000 when driving in anger, but the engine sure doesn't sound too stressed to me. I'm expecting to get plenty of years out of the bottom end. So far I have only autocrossed it, but I'm looking at track days in the future.
July 6, 2011 10:11 a.m. Turboeric New Reader

I have a 1.6 Miata with an FM system running a Link at 12 psi. 220 hp at the rear wheels. Mucho autocross and high altitude 100 degree track days. Daily drive it all summer and have for 6 years. Reliable as a hammer now for >60,000 miles.

Reliability has a lot to due with the quality of the tuning. Mine is very conservatively tuned (It's pulled 240 on the dyno, but it's dialed back for everyday use) and has no issues. Just make sure the cooling is adequate - you'll want a bigger rad if you're going to push it hard at all. For semi-sane street driving, you'll be OK.

I'd go for it.
July 6, 2011 10:13 a.m. Keith SuperDork

A 1995 at 12 psi and 250 rwhp should last a long, long time. We've got a customer who's over 350,000 miles with a 1991 at a similar boost level. He's at about 225 rwhp because of his smaller 1.6, but the engines really are pretty much identical.

The Link ECU isn't the latest technology, but the software was written specifically for Miatas with FM turbos and it's a lot more capable than you'd expect from the spec sheet. The only danger with the Link is the age of the electronics. Components on the boards are starting to fail, and a few solder joints have proven to be prone to cracking. The latter is an easy fix, and we do have parts boards here that we can use to scavenge components.

You'll definitely have to address the cooling system, even just for street use. The plastic end tanks on that 16-year-old stock radiator are ready to crack. The hardest part of tracking a turbo Miata is keeping the temperatures under control. We've made some really big strides on that in the past 18 months at FM, and I don't think anyone else has caught up yet Shifting at 6500 instead of 7200 rpm will actually make a pretty big difference.

The biggest problem with buying used modified Miatas (and probably other cars) is that they tend to go through a few owners in quick succession. Let's say Alan owns the car and modifies it. He does all the research and lavishes love and money on it. Then, years later, he sells it to Bob. Bob finds it a bit too complex so he sells it to Charlie, who then soon passes it on to Dave. Each time, the car is either neglected or is monkeyed with. By the time Ernie buys the car, it's getting a bit shagged. It's not unusual to have to refurbish a lot of things. Sounds like that's not the case with this car, though. That's a big plus.

We do have upgrades and replacement parts for almost all of the FM II turbos. We've tried to make any new designs backwards compatible with the old ones. Our new downpipes, for example, fit the older turbos. You can retrofit the new intercoolers and piping. The manifolds fit, etc. So we'll be able to support this thing.
July 6, 2011 10:23 a.m. z31maniac SuperDork

^You always want to make me buy a Miata instead of playing with E30s.
July 6, 2011 10:28 a.m. 92CelicaHalfTrac SuperDork

z31maniac wrote:

^You always want to make me buy a Miata instead of playing with E30s.

You've got awhile. It only took him about 4-5 years to get to me.
July 6, 2011 12:12 p.m. Duke SuperDork

...whereas I bought my Miata out of the blue (never even driven one except this one) and suddenly found that Keith is my new best friend!
July 6, 2011 12:45 p.m. Racer1ab Reader

Thanks a lot, guys! Sounds like I should be ok!

If I end up with the car, I will definitely be giving the good folks at Flyin' Miata a call.
July 6, 2011 12:54 p.m. Jay_W Dork

I personally know that the stock bp rods can take 18psi for pretty much ever under rally conditions. 21, not for even part of one stage. As long as that engine passes the compression test and there's no sign of crank pulley wobble (very unlikely), it'll go another 100k easy. Go for it. You ain't gettin any "talk me down" from the likes of this board!
July 6, 2011 1:03 p.m. Keith SuperDork

You guys are making me blush.

It's not really boost that breaks rods, it's knock. The Link has a decent knock sensor setup, but it's not really good for running over 18 psi due to limitations of the MAP sensor. That's okay, that turbo (very likely a GT2560RS, same one we use now) isn't really good for much more than that anyhow.

Racer1ab, if you do get the car, send us some pictures as well as any details you have on the previous owner. We like to keep records of where all the Links are and we'll help identify exactly what you're dealing with.
July 6, 2011 5:20 p.m. Teggsan New Reader

Keith wrote:

[smart stuff about the Miata]

I've heard that the FI Miatas have a hard time delivering HP after being run hard for a while (e.g. a track session). Heat soak throughout the system; intake temps get up there.

Is this a major concern?

Thanks for any comment.
July 6, 2011 8:20 p.m. JamesMcD Reader

What about running water injection on one of these?
July 6, 2011 8:55 p.m. unevolved Dork

JamesMcD wrote:

What about running water injection on one of these?

I can't remember where I read it, but some book said that water injection on a turbo car is nothing but a bandaid for a poorly designed system. Any problem water injection will solve can be solved better at other points in the system.

Maybe that's just a matter of opinion, but it makes sense to me. There are more efficient ways to deal with high charge temperatures than adding another failure point.
July 6, 2011 9:51 p.m. DaveEstey HalfDork

Water/methanol injection has been used extensively in the subaru world. I've seen these systems put down incredible torque numbers.
July 6, 2011 11:04 p.m. Keith SuperDork

Teggsan wrote:

Keith wrote:

[smart stuff about the Miata]

I've heard that the FI Miatas have a hard time delivering HP after being run hard for a while (e.g. a track session). Heat soak throughout the system; intake temps get up there.

Is this a major concern?

Thanks for any comment.

That's going to depend on the choice of intercooler. A stock Mazdaspeed model? Definitely, it'll lose 15 hp over three dyno runs. One of the water/air M45 supercharger intercoolers? Oh yes, as they use the coolant overflow tank as a reservoir from what I recall. The intercoolers in the FM II or most other aftermarket turbos shouldn't have a problem, though. They tend to be a good size air/air setup that gets a lot of airflow. They're more likely to hit the overheat protection from a high coolant temperature.

As for water/methanol, it's not a bandaid. It can let you run a LOT more timing, almost as if you're running race gas. And timing equals power. An intercooler can only drop the intake charge to ambient temperatures, remember. With water injection, you can get lower. I've seen datalogs where the intake temperature has gone down on a full throttle run You get great resistance to detonation, far better than you can with just cool intake temps. I believe it's because it will actually cool hot spots in the combustion chamber.

Water/meth injection can be implemented poorly, though. If done well, the ECU will react to a loss in water flow and go to a safe "no water" map.

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