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Old 10/20/15, 12:01 PM   #1 (permalink)
 
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engine builder advice

so the 1.6L in my turbo miata blew up. i pulled the head thinking i just over-revd and bent a valve, since it sounded like it was running on 3 cylinders. turns out i have a huge chunk missing out of my #1 piston. I had purchased the car in san diego and it was running like dog shit at our altitude, so i bought the paid tunerstudio and used the auto tune and it ran 10x better. seemed safe to me i never saw it lean under boost so i don't know what happened, but it seemed like detonation damage. I had also raised the redline recently so maybe a valve DID contact the piston but the valve's seemed ok so... ???

I am still deciding if I should just swap in a stock 1.6L and get a proper tune this time. I can get a ~50k shortblock for about $800-1000. and just drop it in.

Or I can build the bottom end of this one. looks like forged sets of pistons and rods are ~$850 or so. Then I have to get it built somewhere. Is it even worth it to build this 1.6? are there any good shops in town that would get it done right? just hot tank, hone, and assemble i guess

What do you guys think?
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Old 10/20/15, 12:55 PM   #2 (permalink)
 
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Originally Posted by bignickmetro View Post
so the 1.6L in my turbo miata blew up. i pulled the head thinking i just over-revd and bent a valve, since it sounded like it was running on 3 cylinders. turns out i have a huge chunk missing out of my #1 piston. I had purchased the car in san diego and it was running like dog shit at our altitude, so i bought the paid tunerstudio and used the auto tune and it ran 10x better. seemed safe to me i never saw it lean under boost so i don't know what happened, but it seemed like detonation damage. I had also raised the redline recently so maybe a valve DID contact the piston but the valve's seemed ok so... ???

I am still deciding if I should just swap in a stock 1.6L and get a proper tune this time. I can get a ~50k shortblock for about $800-1000. and just drop it in.

Or I can build the bottom end of this one. looks like forged sets of pistons and rods are ~$850 or so. Then I have to get it built somewhere. Is it even worth it to build this 1.6? are there any good shops in town that would get it done right? just hot tank, hone, and assemble i guess

What do you guys think?
Is this a 91 octane car? What was your AFR under boost? How much timing? What was your redline?

I don't know shit about miata engines, but usually if you scatter a piston it's something in the tune. If the higher redline caused you to float a valve and there was contact significant enough to break your piston, the valve(s) would show some obvious damage.

My guess is detonation from too much timing advance, that or you simply exceeded the limit of the stock piston.
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Old 10/20/15, 12:57 PM   #3 (permalink)
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Old 10/20/15, 04:18 PM   #4 (permalink)
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I'd just drop in a used shortblock and get a decent tune. Unless you're trying to double down on output? What supporting mods are needed then?

Without a budget, go full blown forged internals, stroked, port the heads, upgrade your turbo and run a 100 octane tune with nitrous.
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Old 10/20/15, 04:37 PM   #5 (permalink)
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It's just a Miata 1.6L. Perfect opportunity to switch to a 1.8L
Buy short block, properly tune it or switch the setup.

I will edit: Just to do a bit research. Some turbo kits are only for 1.6L not 1.8L. Either way buy shortblock
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Old 10/20/15, 04:54 PM   #6 (permalink)
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Just get a new shortblock, e85, and a good tune.
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Old 10/20/15, 05:23 PM   #7 (permalink)
 
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I would probably swap a 1.8. There are cast 1.8 manifolds on ebay now for around 100 and if you have a flyin miata or begi kit then the turbo location should be pretty close. If you decide to keep it 1.6 then I would just swap a stock block.
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Old 10/20/15, 06:36 PM   #8 (permalink)
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Originally Posted by bignickmetro View Post
so the 1.6L in my turbo miata blew up. i pulled the head thinking i just over-revd and bent a valve, since it sounded like it was running on 3 cylinders. turns out i have a huge chunk missing out of my #1 piston. I had purchased the car in san diego and it was running like dog shit at our altitude, so i bought the paid tunerstudio and used the auto tune and it ran 10x better. seemed safe to me i never saw it lean under boost so i don't know what happened, but it seemed like detonation damage. I had also raised the redline recently so maybe a valve DID contact the piston but the valve's seemed ok so...
Like Grey said, we need more info on the setup like what turbo, what boost level, timing, fuel type, fuel system, etc.

Originally Posted by JEWPRA View Post
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Damn, I must be lucky to be running 9's on it? lol
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Old 10/20/15, 07:39 PM   #9 (permalink)
 
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i don't really want to swap to a 1.8, since i didn't build the car in the first place and don't want to fuck with different sensors on the megasquirt, driveshaft, and a new turbo setup. its a newly rebuilt stock turbo from a sr20 on a cast manifold, has a genuine garret housing but not sure about the internals. i don't remember what boost i was logging, but my gauge was reading about 12-13 psi on most pulls. it has a manual boost controller that was set at that level when i bought it. i was running 91 octane

timing is locked at 10* normally on these cars, although i wasn't the one who timed it the last time the belt was changed so i guess it could be a little advanced, doubt it tho.

it has rx-7 injectors with heatsinked resistors. i forget the flow rate, maybe 360cc but that should be enough for 91. i am not going to run e-85 on this car, i am planning on using it for road trips and stuff. was getting great mileage before the explosion the tune seemed great. like 19mpg on the hard driving tanks and 28mpg on the soft driving highway tanks.

i spent a lot of time tuning idle, it was perfect. and it ran nice and lean at cruise, richened up to ~11.5 under small load, 10.8-11.0 under full boost and WOT. never saw it lean out under boost. i dont have any tuning experience but the autotune really seemed to work and made a drastically smoother map than when i first got it, and nailed all the AFR targets i wanted it to. ill get eric to tune it this time though for sure.

thanks for the help guys, it seems like im gonna say fuck a forged build and just drop in a stock 1.6 and get it running soon again.
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Old 10/21/15, 09:53 AM   #10 (permalink)
 
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Originally Posted by bignickmetro View Post

timing is locked at 10* normally on these cars, although i wasn't the one who timed it the last time the belt was changed so i guess it could be a little advanced, doubt it tho.
When you say "timing is locked in on these cars," what do you mean? It sounds like you are talking about shooting the timing at idle with a timing gun. That's not what I mean when I say to much advance. Timing on naturally aspirated cars, even carb'd dizzy cars, advances with engine RPM based on one reference or another. With fuel injected cars, those references are usually RPM and engine load, or air pressure. So as your RPM increases, your advance climbs from your base timing of 10 degrees, around 5 degrees per 1000 rpm. With power adder cars, whether boost of spray, you have to retard the timing proportional to the amount of boost or n2o. There are certain areas of your power band that are more sensitive to timing advance as well. So when you add a power adder to an engine that was originally NA, your entire timing curve has to be changed, and comprehensive testing should be done by the tuner to make sure it is the best balance of power and safety. Boost, fuel octane, sparkplug heat range and gap ALL play a part.

I don't know how your autotune works, but if it changed your timing curve, thats probably what did it, if not that, I'm guess that the curve hadn't been dialed in for the upper RPM when you increased the redline.
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Old 10/21/15, 01:57 PM   #11 (permalink)
 
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I don't think autochanges timing. I think it is just for fuel. I would compare your timing map to one on miataturbo
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Old 10/22/15, 03:22 PM   #12 (permalink)
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Originally Posted by Dark Star View Post
Like Grey said, we need more info on the setup like what turbo, what boost level, timing, fuel type, fuel system, etc.



Damn, I must be lucky to be running 9's on it? lol

I wouldn't call it luck. Plenty of cars running 9s, 8s, I think at least even one 7 second car is using it. Obviously you're motor is relatively happy on it so either you knew what you were doing when you tuned it or you had someone tune it that knew what they were doing. I'm sure you didn't just let "autotune" take the wheel for ya lol. Have to remember timing is timing and a/f is a/f so I'm not saying you can't get a "safe" tune with it.

Just a shitty EMS imo.

I've used MS, FAST, Wintech4, AEM, and ProEFI now and MS was the only one I'll never fuck with again.
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Old 10/22/15, 08:36 PM   #13 (permalink)
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Originally Posted by JEWPRA View Post
I wouldn't call it luck. Plenty of cars running 9s, 8s, I think at least even one 7 second car is using it. Obviously you're motor is relatively happy on it so either you knew what you were doing when you tuned it or you had someone tune it that knew what they were doing. I'm sure you didn't just let "autotune" take the wheel for ya lol. Have to remember timing is timing and a/f is a/f so I'm not saying you can't get a "safe" tune with it.

Just a shitty EMS imo.

I've used MS, FAST, Wintech4, AEM, and ProEFI now and MS was the only one I'll never fuck with again.
Hmm. Yes I like to hand tune myself and think it is faster than autotune. I've played with autotune several times just to see what it can do and it does all right but not as well as a good tuner can do.

What version of MS did you use? how many years ago was it? What do you think is so shitty about it?

I too have used AEM, MS, ECMlink, big stuff3 , fast. I think MS(tunerstudio) is just as easy if not easier to navigate and use and works perfectly well. Most of the hate on it comes from back in the days when it was much more "opensource" and that always leads to bugs/flaws. Its gotten much better over the years, for the price and upgradeability it is a decent buy and for some its the only choice.
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Old 10/23/15, 12:52 PM   #14 (permalink)
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Originally Posted by Dark Star View Post
Hmm. Yes I like to hand tune myself and think it is faster than autotune. I've played with autotune several times just to see what it can do and it does all right but not as well as a good tuner can do.

What version of MS did you use? how many years ago was it? What do you think is so shitty about it?

I too have used AEM, MS, ECMlink, big stuff3 , fast. I think MS(tunerstudio) is just as easy if not easier to navigate and use and works perfectly well. Most of the hate on it comes from back in the days when it was much more "opensource" and that always leads to bugs/flaws. Its gotten much better over the years, for the price and upgradeability it is a decent buy and for some its the only choice.
He had one of the very first ms3 pro P&P boxes from DIY for the supra.

I run a ms3x on my turbo ls car. It works great. For the money you can't beat it. Does everything I want it to do and is pretty dang easy to tune and I'm by no means a tooner lol.
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Old 10/23/15, 01:38 PM   #15 (permalink)
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Originally Posted by 06smokes View Post
He had one of the very first ms3 pro P&P boxes from DIY for the supra.

I run a ms3x on my turbo ls car. It works great. For the money you can't beat it. Does everything I want it to do and is pretty dang easy to tune and I'm by no means a tooner lol.

Says the guy that has said multiple times that he wishes he had gone with a HolleyEFI
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