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Old 08-01-2013, 05:42 PM   #201
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Originally Posted by JustinOMGWTF View Post
Funny that SouthBay didn't have anything to say about the RC's either, but I have been hearing a lot of great things about the ID's. I'll look into them.
I ran RC550's on my car for about 1000 miles. They were better then my rx-7 440cc and DW1000 injectors in terms of idle quality. My ID1000's idle even better then I ever got my RC's idling. Even knowing all that I would not suggest that you upgrade to the ID1000's yet. It seems like money not well spent unless you decide to turn up boost and actually run out of head room on the RC's.

Along with the forged pistons I am hoping you are getting forged rods, or already have them in the block.

No matter what after the new motor is in, you will need to take it back to the dyno and have it re-tuned.
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Old 08-01-2013, 05:42 PM   #202
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How about a decent knock sensor?
Did research into utilizing the Knock Sensor on my DIYPNP board, but it looked to be buggy and more trouble than it's worth.

Anyone here running knock sensors on their Miatas that actually work well?
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Old 08-01-2013, 05:52 PM   #203
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I ran RC550's on my car for about 1000 miles. They were better then my rx-7 440cc and DW1000 injectors in terms of idle quality. My ID1000's idle even better then I ever got my RC's idling. Even knowing all that I would not suggest that you upgrade to the ID1000's yet. It seems like money not well spent unless you decide to turn up boost and actually run out of head room on the RC's.

Along with the forged pistons I am hoping you are getting forged rods, or already have them in the block.

No matter what after the new motor is in, you will need to take it back to the dyno and have it re-tuned.
If I was going to make the investment in the ID's then I'd probably just go for the ID725...not really planning on making any more power, just want a wider margin of error. Idle quality and drivability was no problem with this last setup, so I can't really see there being that much room for improvement...hard to measure "smoothness" and as stated more power output is not a goal any longer.

Yep - I was running Manley/SCAT H-beams with ARP 3/8 bolts. You can probably see them in the pics I posted earlier. They're in the midst of being checked for straightness at the machine shop.

With the minimal changes you think I'll have to get retuned regardless? That would probably be best practice, but it's the same head and block, just forged pistons (.2-.5 static comp ratio drop) and slightly bigger intercooler.
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Old 08-01-2013, 06:14 PM   #204
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You have to get retuned because this tune blew up your engine. I thought that was rather obvious.
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Old 08-01-2013, 06:25 PM   #205
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You have to get retuned because this tune blew up your engine. I thought that was rather obvious.
...yet it ran fine during the dyno session, daily beaten and abused for 4-5 months, and 3 auto-x events.

Besides not having anyone in the tri-state area that wants to touch MS besides Xenocron, I'm sure you can see why I don't want to get a complete retune. Small improvements in the current setup and toning down the tune will suffice for my goals of just having a larger safety margin. If it detonates again, then you can say "I told you so."
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Old 08-01-2013, 06:45 PM   #206
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Why don't you have wideband readings?
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Old 08-01-2013, 06:46 PM   #207
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If this was your first rebuild, I would probably agree with you.




At this point, I don't think you have luck on your side.
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Old 08-01-2013, 07:02 PM   #208
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Why don't you have wideband readings?
What I meant was that I didn't have any readings during the catastrophic event.

However, you did just remind me that I took logs during the misfiring shortly thereafter. I've attached it in case anyone was interested in what a 3-cylinder BP-T looks like

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If this was your first rebuild, I would probably agree with you.

At this point, I don't think you have luck on your side.
That I can completely agree with. Sucks having to budget by cutting corners but there are other priorities in life.
Attached Files
File Type: msl 2013-06-21_13.37.21.msl (1.19 MB, 83 views)
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Old 08-01-2013, 07:15 PM   #209
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What were the wideband readings at WOT before it grenaded?

I would do low-comp pistons and a bigger intercooler, but I'd also take 4-6* out of your timing map above ~140kpa. It's way, way, way too aggressive for pump gas. Maybe more than that if you failed and bought a 0.64a/r GT2871R.
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Old 08-01-2013, 07:35 PM   #210
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Originally Posted by Savington View Post
What were the wideband readings at WOT before it grenaded?

I would do low-comp pistons and a bigger intercooler, but I'd also take 4-6* out of your timing map above ~140kpa. It's way, way, way too aggressive for pump gas. Maybe more than that if you failed and bought a 0.64a/r GT2871R.
WOT at 20psi was around 11.2-11.5 AFR. Attached the last dyno run log so you can see what it was running. I didn't have my eyes on the AFR during the detonation, though.

Have these Wiseco pistons on the way:

Part # Application Bore Size Compression Ratio
K553M835 BP 1.8L 83.5mm (+0.020" Over Bore) 8.5-8.8:1

Bigger intercooler is also in the works - doing some research. Any recommendations off the top of your head?

Turbine housing is a ported .64.

Attached timing map with 5 deg taken above 140 - does that look right? Again this is on a 99 head with the intake retarded 7 degrees.
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Built motors and detonation-timing.gif  
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File Type: msl run1922013-03-14_15.35.32.msl (295.4 KB, 73 views)
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Old 08-01-2013, 08:51 PM   #211
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Still kind of aggressive for 91. Might work on 93-94. The 0.64a/r turbine is not doing you any favors here - swapping to a 0.86a/r housing would let you get away with more timing and it'll make more power to boot.
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Old 08-01-2013, 09:05 PM   #212
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Still kind of aggressive for 91. Might work on 93-94. The 0.64a/r turbine is not doing you any favors here - swapping to a 0.86a/r housing would let you get away with more timing and it'll make more power to boot.
Appreciate the constructive feedback, Savington.

It was ran on only 93 octane. I'm in contact with tuner right now to see what my options are and will update this thread after everything's sorted out so others might learn from my mishap.

Understood that a smaller housing is restrictive at these levels of boost and hurting performance, but I also originally targeted a quicker spool for general purpose street and auto-x...both of which it does a pretty good job of. I ran larger housings on other cars and despised the sluggish off-boost response, so I decided to compromise this time. Besides, I'm strapped for cash at the moment so minimal changes ($$$) permitted at this time.
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Old 08-01-2013, 10:32 PM   #213
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The spool difference is minimal between the 0.64 and the 0.86 on a Miata. The torque difference in the midrange and the extra det threshold headroom isn't. I'd swap the turbine housing.
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Old 08-01-2013, 10:50 PM   #214
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The spool difference is minimal between the 0.64 and the 0.86 on a Miata. The torque difference in the midrange and the extra det threshold headroom isn't. I'd swap the turbine housing.
ok, ok - I'm sold. Have one for sale?
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Old 08-01-2013, 10:59 PM   #215
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Having trouble finding GT2871R .64 vs .86 comparison. BUt then there's the newer GTX series:

GTX2867 .86 A/R vs .64 A/R Turbine Dyno
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Old 08-02-2013, 12:58 AM   #216
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with a precision 600 and colder weather, no?
Yes, with a big intercooler and excellent AFR
I was still shitting bricks
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Old 08-02-2013, 01:29 AM   #217
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Having trouble finding GT2871R .64 vs .86 comparison. BUt then there's the newer GTX series:

GTX2867 .86 A/R vs .64 A/R Turbine Dyno
Different engine. Results don't apply to us.
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Old 08-02-2013, 01:31 AM   #218
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And yet, I wonder: is it really as drastic as you say it is. I've done a quick search and every time we talk about this, its just talk. Do you have some proof?

For the record, I'm of the same mindset as you and usually side with the larger hotside, but all MY proof and/or experience has been on other cars, with larger motors from our 1.8....So I really can't say for 110% sure when talking about a miata with a gt28xx turbo
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Old 08-02-2013, 02:32 AM   #219
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And yet, I wonder: is it really as drastic as you say it is. I've done a quick search and every time we talk about this, its just talk. Do you have some proof?

For the record, I'm of the same mindset as you and usually side with the larger hotside, but all MY proof and/or experience has been on other cars, with larger motors from our 1.8....So I really can't say for 110% sure when talking about a miata with a gt28xx turbo
https://www.miataturbo.net/diy-turbo...43/#post642164

Not apples to apples, but close enough. The difference can be compensated for entirely by using a good tubular manifold and downpipe.
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Old 08-02-2013, 02:59 AM   #220
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Ha, even in that thread I was agreeing on the .86 being the better choice.

However, and maybe cause my plans and goals for current car have changed drastically from the previous, but I've been re-thinking my logic (and that discussion).

I don't think its a fair comparison at all:
non vvt head vs vvt head (like 500 rpm worth of lowend just in that alone)
his is also mildly worked which usually tends to improve topend at slight expense of spool
cast log mani vs one of the best tubulars (another like 300-400 or so)
race gas vs e85 (e85 promotes better spool too, dunno how much exactly)

the only slight disadvantage you have there is your high flowing honda im vs his stocker

Anywho.....I wish we had an actual apples vs apples comparison on a miata. Cause I think this is far from a clear cut open and shut discussion.

*edit: also the more I look the more I see stuff like this online:


which supports a whole lot of the claims that many make:
smaller hotside - broader torque curve
larger hotside - hits later but harder
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