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-   -   Dead Engine Autopsy (picture intensive) (https://www.miataturbo.net/engine-performance-56/dead-engine-autopsy-picture-intensive-49851/)

miata2fast 07-22-2010 04:18 PM

You have a detonation problem on all 4 cylinders clearly. Those clean spots on the piston edges and ridges are not good. I would rule out the coolant reroute, and concentrate on tuning issues. I think you have the timing way to hot.

When you pull the pistons, report on how much tension you have in the rings. Over heating would make them weak, and you will notice cylinder wall scuffing and piston scuffing. Detonation will not necessarily have an affect on ring tension. Over heating will.

johnmatt 07-22-2010 04:46 PM

1 Attachment(s)

Originally Posted by wayne_curr (Post 605435)
Your detonation doesn't look nearly as bad as mine did though.

Got ya beat
Attachment 195786

Braineack 07-22-2010 05:38 PM

http://www.boostedmiata.com/gallery2...-1/pistons.jpg

gospeed81 07-22-2010 05:54 PM

3 Attachment(s)
You pussies don't even know what det is...

Attachment 195783

Attachment 195784

Attachment 195785

levnubhin 07-22-2010 06:17 PM

You fuckers need to learn how to tune lol.

<- hopes to never eat those words.
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wayne_curr 07-22-2010 06:43 PM

1 Attachment(s)
This should all be making Mr. Ganger feel better about his engine.

Attachment 195782

hustler 07-22-2010 06:48 PM

lol @ pushing it and not finding the conservative happy place.

90R 07-22-2010 08:46 PM

why do #1 & #2 rods have rust on them?

is the head flat?

gospeed81 07-22-2010 11:13 PM


Originally Posted by hustler (Post 605557)
lol @ pushing it and not finding the conservative happy place.

My tune was conservative, for me. Water injection, Brainy's advance dialed back a few degrees...

You know who killed mine, you met him. Let him borrow it over Christmas break and he brought it back smoking.


New tune will be higher resolution MS2, crank trigger, and real, new injectors. Water injection soon to come, just missed a good deal from Sav, but eyeing splittime's setup.




Dopple, I'm in to see where your tuning went wrong as well. I thought my timing advance table was gravy, but you can see from the above there were some bad spots in it that ate up the motor during consecutive pulls (although he said he was eating up STis and such and having fun, so oh well).

Doppelgänger 07-22-2010 11:54 PM

Well, it was tuned by a VERY respectable tuner here in GA. The guys tunes TONS of stuff...everything from carb'ed turbo cars, to SPEED challenge cars, to Spec Miatas, to high-strung all motor Hondas. I trust him. Actually, I was running that tune since a month after I bought the car. Tracked it, drove it across the country, daily'ed it...everything. Something happened pretty quickly..as in within a couple of weeks before the failure. I'm almost wondering about a bad tank of gas that I got the week before at some podunk station in Alabama.

Cylinder walls are perfect and the cross-hatching is visible as it should be. No scoring, gouging or scratches at all.

AutoFreak57 07-26-2010 10:44 PM

How many miles did you have on that setup again? I think it was a lot if I remember right

Doppelgänger 07-26-2010 11:00 PM

FWIW, I wiped the carbon off the pistons tonight and found some small pitting on #1 and #2 by the exhaust valve area but not much on #3 or #4.

Edit- fuckit here are pics of the pistons with a little rubbing off...

piston #1

http://farm5.static.flickr.com/4083/...8e7d898c_b.jpg

#2 on right #3 on left

http://farm5.static.flickr.com/4150/...d3073f93_b.jpg

#2 close

http://farm5.static.flickr.com/4103/...bfd85cd2_b.jpg

cross-hatching

http://farm5.static.flickr.com/4152/...01df810d_b.jpg

#4

http://farm5.static.flickr.com/4106/...b98d3f1c_b.jpg

lordrigamus 07-26-2010 11:24 PM

What about air temps? I've seen the hottest AITs ever in my car during this never ending heat wave. Yesterday was the nicest day we've had in two months up here.

I agree with the above mentioned thoughts as well. 1&2 look bad and the#1 rod does look bent. Don't be surprised if the ring lands fall off of #1 when you pull it. Post that spark map anyway, inquiring minds want to know.

sixshooter 07-27-2010 08:28 AM

So Doppelganger, do you think the reroute with the 01+ headgasket was the primary problem or do you think your tune needed less spark advance when IATs get above a certain threshold as was proposed by Lordrigamus?

Doppelgänger 07-27-2010 08:55 AM

I think it was the reroute. Seems the lack of flow around the topend on 1 & 2 indeed caused excessive heat/detonation. I will be adding a front t-stat and plumbing to my reroute very shortly.

miata2fast 07-27-2010 09:15 AM

I have my doubts about the reroute. All four pistons look like they have been in a tumbler. That is not a overheating issue That is many miles of fun.

Let's face it, a boosted engine that is beat on is not going to come out unscathed with stock pistons forever. Even with a conservative map.

Doppelgänger 07-27-2010 09:16 AM

1 Attachment(s)

Originally Posted by lordrigamus (Post 607458)
What about air temps? I've seen the hottest AITs ever in my car during this never ending heat wave. Yesterday was the nicest day we've had in two months up here.

I agree with the above mentioned thoughts as well. 1&2 look bad and the#1 rod does look bent. Don't be surprised if the ring lands fall off of #1 when you pull it. Post that spark map anyway, inquiring minds want to know.


Originally Posted by sixshooter (Post 607574)
So Doppelganger, do you think the reroute with the 01+ headgasket was the primary problem or do you think your tune needed less spark advance when IATs get above a certain threshold as was proposed by Lordrigamus?


I don't have a map on my work computer, but I do have a 1st-4th gear pull .csv log where you can see what my timing was doing under boost :dunno:

Doppelgänger 07-27-2010 09:18 AM


Originally Posted by miata2fast (Post 607585)
I have my doubts about the reroute. All four pistons look like they have been in a tumbler. That is not a overheating issue That is many miles of fun.

Let's face it, a boosted engine that is beat on is not going to come out unscathed with stock pistons forever. Even with a conservative map.

True, but there is obviously more issues with 1&2 where it's known that the design of the 01+ HG reduces coolant flow significantly.

fooger03 07-27-2010 12:14 PM

Just out of curiosity, you weren't the one that posted a recent vid of your car hitting 26 psi, were you? :giggle:

Doppelgänger 07-27-2010 12:21 PM

nope, not me.


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