Reliability of a modestly boosted Miata

I'm posting this as follow up to another thread.

I have a 2001 LS that I am in the process of refreshing. I have finished a full repaint,replaced the top and installed elise seats.

I'm now collecting parts for spring wrenching. Brakes,exhaust etc.

While the car is in refresh mode I have been thinking of going FI. I would be planning a basic Voodoo II install, with an attention to detail and no designs on squeezing out extra power. I want reliability, with a modest power increase.

The question is to those who have experience with a modestly boostedMiata how has reliability been?

The car would be street driven with a few trackdays thrown in.

T

Depends on your expected use of the car. Street car? Probably just as reliable as a stock miata assuming the tune and assembly is good.

I haven't had any true reliability issues with my turbo Miata. It's had issues, but nothing has broken yet, nor has it left me stranded.

Then again, i also drove it less than 3,000 miles this last summer.

[edit]

Ah, missed the track days portion of it. They can be reliable. Upgrade to iconel EVERYTHING.

The Iconel studs would be excellent insurance, but it does depend on how hard you're driving the car. Not every turbo Miata on the track has stud issues, but the guys who push the cars the hardest do.

Otherwise, concentrate on a good cooling system. Cooling problems cause more difficulties than anything else on track, even on lower power car. Fans are important at speed - you don't have 80 mph air blasting through your radiator at 80 mph, far from it - and don't be tempted by cheap "slimline" units that are worse than stock. It's a good idea to replace your radiator as the plastic end tanks of your 12-year-old one are a liability, and again - get a good one instead of a cheap one. Fin density and flow design trumps core thickness. Shifting at 6000 rpm will help a lot too.

I have a friend who's put over 50K miles on a stock miata motor running about 8-12 psi of boost...

Keith Tanner wrote: and don't be tempted by cheap "slimline" units that are worse than stock.

I'm a huge fan (shoot me) of SPAL. The tiny little slim fans we used in FSAE had enough thrust in reverse to lift off a table. Not crazy expensive, either.

Keith should write a book...oh wait.....

I agree with the cooling deal. On the street a stock, new, Miata rad will do. You will need the underbody tray. Don't take it off and throw it away. Newer electric fans will be nice but I don't feel they're necessary on the street if both stock fans are working well and the rad is new. Check all your hoses. The underhood heat will cook the sh!t out of them. Remember, this is all street prep.

On the track you'll need the largest rad you can fit/get. Even 5lbs of boost can overheat if you're tracking the car hard depending on your cooling system and state of tune. Get the best fans you can get. Flyin Miata has a great set. There are less costly, and less effective, alternatives that may work. I ran a car at VIR with a Mishimoto rad, two of the largest slimline fans, undertray, and stock coolant circuit routing without issue at 8lbs of boost in the spring. I'll bet the FM kit could support much more than that and reliably. Iconel is a great way to go with the turbo to exhaust manifold joint. I would V-band the turbo to downpipe joint. If I were to do it again I'd follow Keith's advice on how to make sure every part downstream from the exhaust manifold holds together. Even with iconel studs I had a hard time keeping my turbo attached to my exhaust manifold. Mechanical skill of the builder could be the issue.

Sky_Render wrote: I have a friend who's put over 50K miles on a stock miata motor running about 8-12 psi of boost...

Any idea how many of those miles were on the track?

Xceler8x wrote:

Sky_Render wrote: I have a friend who's put over 50K miles on a stock miata motor running about 8-12 psi of boost...

Any idea how many of those miles were on the track?

It gets autocrossed regularly. I don't know how many times (if any) it's blasted around Summit Point or VIR.

Warren v wrote:

Keith Tanner wrote: and don't be tempted by cheap "slimline" units that are worse than stock.

I'm a huge fan (shoot me) of SPAL. The tiny little slim fans we used in FSAE had enough thrust in reverse to lift off a table. Not crazy expensive, either.

SPAL makes good stuff - we use their fans. But when it comes to pulling air through multiple heat exchangers (condenser, radiator, intercooler, oil cooler), you need torque. And that means a fat motor. Check the fan ratings for flow with static pressure, you'll see how they fall off really quickly with slimline motors while the big boys continue to pull. I've not been impressed with the Mishimoto fans in particular, they just don't seem to move lots of air and they're too close to the core.

Testing a fan on a table is a quick demonstration on just how much dust is in the vicinity!

We've got tough cooling conditions here - high ambient temperatures, low humidity (good for people, bad for cars) and low air density. My 1.6 Voodoo II with the little GT2554 used to have trouble staying cool on the highway but not in town. We tried a bunch of different radiators and a different intercooler that we thought might offer less air restriction. The thing that did the trick? A set of good fans on a good shroud. Contrary to common sense, cooling at rest was never a problem. But I digress...

The weakest joint in the system is the turbo-to-manifold bolts. If I were designing a system from scratch, I'd mount the turbo differently. But we've stuck with the current design for legacy reasons, as it allows us to support customers from the 90's. The turbo-to-downpipe joint is far less problematic.

We rarely have problems with our turbo track cars at FM. A large part of this is (probably) driving them a bit more conservatively than lap record speed, I expect. As usual, it's that last 5% of effort that causes 50% of the problems.

Sky_Render wrote:

Xceler8x wrote:

Sky_Render wrote: I have a friend who's put over 50K miles on a stock miata motor running about 8-12 psi of boost...

Any idea how many of those miles were on the track?

It gets autocrossed regularly. I don't know how many times (if any) it's blasted around Summit Point or VIR.

So not even close to valid comparison then?

My Miata did 83K miles on the original bottom end before I pulled it out to rebuild it. Compression was down on #4 when I pulled it out, but I probably wouldn't have done the rebuild except that I already had most of the parts out of the car due to a head gasket problem after losing my coolant at Laguna the previous year.

50K of those 83K miles were boosted, mostly above 220 rwhp. The motor did probably 40-50 track days (split roughly evenly between boosted and naturally aspirated) and several years of autocrossing. It was making 255rwhp before I tore it down.

That said, I did have to replace the exhaust valves around 50K miles. The turbo manifold warped and the exhaust valves where it was leaking weren't sealing properly. I'm not sure which was causal to the other.

If you're going to track it with the turbo, you'll want a big radiator, coolant re-route, oil cooler, inconel studs, and race gas while on the track.

Expect the 5-speed's life to be short without "mechanical empathy". Even with it, mine failed at Laguna last year. I've got a 6-speed and 3.636:1 in it now.

In reply to Tralfaz:

I have a 92 running an FM system at 12 psi using the MiataLink management. It's my daily driver in the summer, and has been autocrossed regularly and gets 2 - 4 track days a year for the past 7 years. It now has over 60,000 turboed miles on it. In daily driving - no issues. At the track, heat management is the biggest issue. As Keith suggest, keeping your shift points down is key. My oil temp gauge is really a cumulative revs gauge. Shifting at 6500 rpm, my FM radiator and two oil coolers manage without difficulty. Shifting at 7200 rpm, I have to keep an eye on both temp gauges and back off occasionally.

My motor is a 1.6 with a fairly conservative tune (219 rwhp, 205 ft/lb). If you heat shield, heat wrap and reroute anything that doesn't react well to excess heat, you'll have no serious issues.

I appreciate the feedback.

Thank you.

T

I am currently rebuilding a Mazda 1.8L BP engine and I can assure you that the engine can take what you plan on doing. Keep the engine cool and watch the A/F ratio under boost and you should have no problems.

Turboeric wrote: In reply to Tralfaz: I have a 92 running an FM system at 12 psi using the MiataLink management. It's my daily driver in the summer, and has been autocrossed regularly and gets 2 - 4 track days a year for the past 7 years. It now has over 60,000 turboed miles on it. In daily driving - no issues. At the track, heat management is the biggest issue. As Keith suggest, keeping your shift points down is key. My oil temp gauge is really a cumulative revs gauge. Shifting at 6500 rpm, my FM radiator and two oil coolers manage without difficulty. Shifting at 7200 rpm, I have to keep an eye on both temp gauges and back off occasionally. My motor is a 1.6 with a fairly conservative tune (219 rwhp, 205 ft/lb). If you heat shield, heat wrap and reroute anything that doesn't react well to excess heat, you'll have no serious issues.

Good info. I'm seriously considering boosting my track Miata.........but I don't want to have to lower my shift points.

This is relevant to my interests.
Always wanted to run 1 bar of boost, never quite got there with my Supra...
(87, not one of the ones everyone hopes )

z31maniac wrote: Good info. I'm seriously considering boosting my track Miata.........but I don't want to have to lower my shift points.

Ah, but when there's torque waiting for you when you shift, it's an easy adjustment to make!

I want it all!!

I've probably put 60k miles with my supercharger installed on my '97. I was at 11psi for a good 50k (crappy tune too!), and I'm now at 14psi. I have 249 hp to the rear and 220 torque. No issues ever, and the car has always gone through a little oil since I bought it. I'm at 110k miles now, and I'm tempted to freshen the engine a bit so it runs cleaner (little puffs of smoke on the dyno), but it's still going strong.
I've only had track days in it while it was NA. I still need a better radiator before I do it with the blower.

-Hamid

AverageH wrote: I've probably put 60k miles with my supercharger installed on my '97. I was at 11psi for a good 50k (crappy tune too!), and I'm now at 14psi. I have 249 hp to the rear and 220 torque. No issues ever, and the car has always gone through a little oil since I bought it. I'm at 110k miles now, and I'm tempted to freshen the engine a bit so it runs cleaner (little puffs of smoke on the dyno), but it's still going strong. I've only had track days in it while it was NA. I still need a better radiator before I do it with the blower. -Hamid

That's very encouraging, especially since the engine is working harder for those 249 horses than a turbo setup.

Been running 7lb boost on the RB supercharger for at least 5 years. AutoX and at least one track weekend a year. So far not a problem. No oil burning. I still need to dyno it.

Hmm I do have some miata turbo parts laying around and a new AL radiator... Spring is quickly approaching...

Keith Tanner wrote: Testing a fan on a table is a quick demonstration on just how much dust is in the vicinity!

I lawled.