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Built motors and detonation

Old 12-21-2009, 05:00 PM
  #101  
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Originally Posted by hustler View Post
Hey, Eurotrash...I'll be able to see perfectly smooth piston tops, unlike the dimpled cottage cheese *** you have to live with from going through life as a beta-male scavenger. A leak down won't show phantom detonation, but it will show that you're a latent homosexual, living the hetero lie.
Chainsaw massacre survivor, I just had my engine's head removed to find as-new pistons and a completely det free head. So don't confuse the cheese *** you're dating with my powah engine.

Originally Posted by faeflora View Post
I disconcour. Couldn't a piston be melting/hotspotting in various places without leakdown symptoms? Isn't leakdown rings? If your piston is melting and getting brittle I'm guessing detonation will break it more easily. If you saw signs of fuxage at least you could try to do something about it before your piston dies and scores up your cylinders etc.
Melting you'd see, but would also quickly become a leak. Too late anyway. Hotspotting you cannot see with a bore as you would do that with the engine off. IMHO you make sure you:
- have knock detection (on the dyno: detcans and preferably in a closed loop ECU)
- tune for safety (a few degreed south of detonation and a tad richer)

Leakdown is valves, rings, everything. Basically leaks...
So, bore comes out after you identify an unknown issue, not to measure health.
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Old 12-28-2009, 03:00 PM
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Originally Posted by hustler View Post
I haz a borescope now.
Which one did you get and what did you see?
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Old 12-28-2009, 03:22 PM
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Originally Posted by JasonC SBB View Post
Which one did you get and what did you see?
I scored one that's just an ordered fiber-optic cable (no camera) that I scored on ebay for $40. The guy selling it said there was enough resolution and magnification to see the grain structure on the pistons.
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Old 01-11-2010, 04:18 PM
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Old 01-15-2010, 06:00 PM
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So this is a little off track but I guess this is the right thread to ask in. If I wanted a 300-350whp street car that was "relyable" (could take it on day long road trips and maybe dick around at the track every once in a while) would some forged turbo pistons (Wiseco for instance), some stronger rods (Carrillo a-beam or h-beams maybe), and ARP head studs be enough? I'm guessing that would equal 15-20psi on a 2860. Oh and would this be possible on pump gas?
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Old 01-15-2010, 06:04 PM
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Probably don't even need the head studs, but an ATI damper or billet OPGs is a good idea. You won't make 350whp on a 2860RS, though, and without a stroker motor and a 3071R, 350whp on pump gas without water injection is going to be tough.
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Originally Posted by codrus View Post
Basically I've come over to the camp of "If something is a reliability problem on the track, just ask Andrew and do what he says".
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Old 01-15-2010, 06:09 PM
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Ditto. I'm all for you doing it--- I'm curious how the s4 holds up above 300whp. Corky says it's not a great idea but I think he is being incredibly conservative.
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Old 01-15-2010, 06:16 PM
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I knew 350 would be pushing it. So the head studs arent necessary because its not a track car or because of power. Also cant figure out what OPGs are.
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Old 01-15-2010, 06:38 PM
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Oil Pump Gears. I don't think anyone has had a head gasket failure and pinpointed the cause on stock head bolts. I use ARP studs, though - there's no downside aside from the cost (and it makes the head much easier to install).
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Originally Posted by codrus View Post
Basically I've come over to the camp of "If something is a reliability problem on the track, just ask Andrew and do what he says".
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Old 01-15-2010, 06:44 PM
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MX5autoxer I'm in the middle of the same thing. BEGI s4 w/ 2860, 2 1/2" enthuza, MSpnp. I have RX7 550's.

94 1.8L putting in Wiseco's, M-tuned rods, OPG's, all new gaskets, ARP head studs, DIY head porting. With the 2860 and my 550's I"m figuring 300-325 is the upper limit. Beyond that bigger turbo, bigger injectors and WI will be needed.
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Old 01-16-2010, 09:33 AM
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I'm a newb here so take it for what it's worth...

In the piston pictures all failures are near the valve reliefs. It is well known that sharp pointed objects in the cylinder get hotter, faster than thick smooth places. If I had those pistons with the machined valve reliefs I would consider smoothing them out. Each failure started with a hot valve relief edge and then torched down the side of the piston.

We run a pulling tractor on Meth with staged turbos @ 70 PSI and have seen a few torched pistons before. Usually from a lean condition on one cylinder.

Broken ringlands and lifted head gaskets without the big torch spot is from detonation IMHO.
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Old 01-16-2010, 02:07 PM
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Yes, it's becoming clear that effective knock detection/correction is an area that's lacking in the Miata aftermarket.
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Old 01-16-2010, 02:19 PM
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Boosted Miata's are so last year. It's all about LS1 now...

DUUURRR
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Old 01-16-2010, 02:24 PM
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Originally Posted by NA6C-Guy View Post
Boosted B6/BPs are so last year. It's all about boosted FE3s now...

DUUURRR
ftfy
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Old 01-16-2010, 02:50 PM
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Does the FE handle 300hp reliably without an act of congress?
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Old 01-16-2010, 03:05 PM
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Originally Posted by NA6C-Guy View Post
Boosted Miata's are so last year. It's all about LS1 now...

DUUURRR
STFU Fagazoid.
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Old 01-16-2010, 03:06 PM
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Originally Posted by JKav View Post
Yes, it's becoming clear that effective knock detection/correction is an area that's lacking in the Miata aftermarket.
What's a proven device/method of aftermarket knock detection/correction?
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Old 01-16-2010, 03:17 PM
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Originally Posted by faeflora View Post
STFU Fagazoid.
Good luck with your ticking time bomb.

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Old 01-16-2010, 03:31 PM
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Originally Posted by NA6C-Guy View Post
Does the FE handle 300hp reliably without an act of congress?
Yes, that's why I'm doing it.

Some say the number is closer to 500whp before you need to go forged.

The other advantage is more (dependable) power with lower pressure ratios....meaning you're not at the ragged edge, and have less need for advanced knock detection.
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Old 01-16-2010, 04:10 PM
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Originally Posted by faeflora View Post
What's a proven device/method of aftermarket knock detection/correction?
Were I a savvy Miata aftermarket vendor, I'd start by understanding what the OEMs do/use on their modern highly-boosted, knock-limited engines.

They've found ways to make turbo engines that generate 130-150+ hp/liter live free of det-induced destruction for ~150k+ miles despite production variation, inconsistent octane and owner neglect. And they do it with basic rods, high compression, cast pistons, skinny ringlands and in some cases open-deck aluminum blocks.

Then I'd find a way to employ the relevant hardware/strategies on the Miata engine.
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