GT2554R Record??? leads to a run of the mill EFR build - Page 11 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 06-29-2016, 01:25 PM   #201
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nonsense. Pretendingtofgt is about to disprove the whole 1.8>1.6 myth

you guyths need to embrace da future
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Old 06-29-2016, 01:32 PM   #202
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timing breaks rods.\

he didn't need all that horsepower to beat a c6.
*C5 Z06, and I know. I had planned this day (the 300hp attempt part, not the blown engine) ever since I pulled the trigger on the 2860R a couple months ago, Corvette guy just happened to challenge me at the perfect time so it lined up. It was fun while it lasted and I knew the risk, time to start over!
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Old 06-29-2016, 01:37 PM   #203
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VVT.

you're welcome.
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Old 06-29-2016, 01:46 PM   #204
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VVT.

you're welcome.
But is it realllllyyyy worth it over a standard BP4W??
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Old 06-29-2016, 01:49 PM   #205
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As an aside, overboost protection won't cause a total loss in oil pressure. The oil pump is still spinning at ~6000rpm regardless of whether the injectors are on or not. You will lose some pressure briefly, but that's just because the bearings aren't as heavily loaded as they were a split-second beforehand. IOW, hitting overboost didn't break the rod, but ~300whp on a stock bottom end did
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Old 06-29-2016, 02:04 PM   #206
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As an aside, overboost protection won't cause a total loss in oil pressure. The oil pump is still spinning at ~6000rpm regardless of whether the injectors are on or not. You will lose some pressure briefly, but that's just because the bearings aren't as heavily loaded as they were a split-second beforehand. IOW, hitting overboost didn't break the rod, but ~300whp on a stock bottom end did
Yeah I'm not thinking the oil pressure had anything to do with the rod failure, I was thinking going from 235wtq into a full power cut and then back on boost was probably pretty stressful for the rods (rapid changes in torque?) because it developed the ticking sound immediately after that happened. The wording int he video was a little confusing because when I was leaving the dyno we still hadn't figured out what was damaged.
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Old 06-29-2016, 02:45 PM   #207
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But is it realllllyyyy worth it over a standard BP4W??
A standard BP4W isn't going to give you 150rwhp as a base...
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Old 06-29-2016, 03:25 PM   #208
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A standard BP4W isn't going to give you 150rwhp as a base...
4w is a z3 or 6d with slightly less midrange
it will make same power

there is nothing wrong with starting with a 4w
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Old 06-29-2016, 04:46 PM   #209
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nothing wrong except that's it's missing out on a bucket full of mid-range and no extra top end (especially once you bolt up a square top) -- out of the box.

If youre going to do a motor swap, do it right.
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Old 06-29-2016, 05:01 PM   #210
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It really does make a huge, huge difference between 3000 and 4000rpm. I've posted charts comparing them before, since I had the same 2871R setup on a BP4W and a BP6D head. Especially with larger turbos, the difference is dramatic.
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Old 06-29-2016, 05:32 PM   #211
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nothing wrong except that's it's missing out on a bucket full of mid-range and no extra top end (especially once you bolt up a square top) -- out of the box.

If youre going to do a motor swap, do it right.
midrange yes.
topend same.
get your NB knowledge straight, old timer

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Old 06-29-2016, 07:11 PM   #212
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It really does make a huge, huge difference between 3000 and 4000rpm. I've posted charts comparing them before, since I had the same 2871R setup on a BP4W and a BP6D head. Especially with larger turbos, the difference is dramatic.
Im personally limiting the power of even 2560r cars in that range due to drivetrain reliability and traction. In what scenario is having even more than a 2560r on a BP4W worth it (300 odd ftlb)? Autocross with a built everything huge huge wing and slicks?

Dann
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Old 06-29-2016, 07:27 PM   #213
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more? probably not. but having 300tq when running good tires and 3.6 final drive is pretty cool
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Old 06-29-2016, 07:32 PM   #214
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Yeah I'm not thinking the oil pressure had anything to do with the rod failure, I was thinking going from 235wtq into a full power cut and then back on boost was probably pretty stressful for the rods (rapid changes in torque?)
Nah, the rod sees larger compressive load changes every other crank rotation because it's a 4-stroke. A power stroke is maximum compressive load, an intake stroke is maximum tensile load (worst when pulling against a vacuum in the manifold).

--Ian
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Old 06-29-2016, 07:39 PM   #215
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I think the boost cut was just coincidence. And it was doomed anyways.
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Old 06-30-2016, 11:59 AM   #216
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I think the boost cut was just coincidence. And it was doomed anyways.
Just odd that it's been putting down roughly 240wtq for a year, and it was only making 230-235 all day, and after a very abrupt OBP limit it was game over. But it's anyone's guess really. I'm interested to see what the other 3 rods look like.
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Old 06-30-2016, 12:22 PM   #217
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Like most of the members on this site, they likely aren't straight
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Old 06-30-2016, 12:23 PM   #218
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Like most of the members on this site, they likely aren't straight
Ahhhhh where's the drumset emoji when I need it most
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Old 06-30-2016, 12:26 PM   #219
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Just odd that it's been putting down roughly 240wtq for a year, and it was only making 230-235 all day, and after a very abrupt OBP limit it was game over. But it's anyone's guess really. I'm interested to see what the other 3 rods look like.
Where did you have the redline set? Did you rev it higher when upping the boost? Ever miss a shift and hit 2nd instead of 4th?

AIUI, most rods fail in tension (that's where they're weakest), usually at high-RPM with vacuum in the intake manifold (maximum tensile load), and it's not unusual for something that weakens a rod to result in it a seemingly random failure days or weeks later.

FWIW, my stock motor had arrow-striaght rods when I took it apart, with 50K boosted miles on it, much of those at 250-260 rwtq.

--Ian
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Old 06-30-2016, 12:50 PM   #220
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Where did you have the redline set? Did you rev it higher when upping the boost? Ever miss a shift and hit 2nd instead of 4th?

AIUI, most rods fail in tension (that's where they're weakest), usually at high-RPM with vacuum in the intake manifold (maximum tensile load), and it's not unusual for something that weakens a rod to result in it a seemingly random failure days or weeks later.

FWIW, my stock motor had arrow-striaght rods when I took it apart, with 50K boosted miles on it, much of those at 250-260 rwtq.

--Ian
Yeah it definitely saw a few flashes of unsafe RPM in its day, mostly due to times when the flatshift was being temperamental and I'd get a nice little 7700rpm overrev despite the limiter being at 7300. The engine has been through a LOT. I was just thinking the OBP was the straw that broke the camel's back, because the ticking sound developed immediately afterwards, and it was loudest right by where the rod exited, making me think it might have been bent enough to be tapping the bottom of the cylinder wall?
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