New engine fail after only 600 miles
 

Hi from Italy!
Unfortunatly my new engine has failed after only 600 miles after the new build, i was running with k1 rods and OEM new pistons and rings, all the engine has been rebuilted with the correct tollerances.
Then a terrible damage of 3 pistons.
It's a really strange piston fail.
https://cimg4.ibsrv.net/gimg/www.mia...a47ca8b03.jpeg

https://cimg1.ibsrv.net/gimg/www.mia...d7da0c9e0.jpeg

https://cimg6.ibsrv.net/gimg/www.mia...2f943d457.jpeg
https://cimg6.ibsrv.net/gimg/www.mia...5d9fb7737.jpeg


I'm trying to understand what has appened. My tuner sais that is because of too much pressure/ boost on the Oem pistons.
I was running at 13PSI and i get 222,2 Hp at the crank at 5970 rpm and 241 ft-lbs at 2942 rpm.
https://cimg2.ibsrv.net/gimg/www.mia...818104446.jpeg

More pictures can be seen here

I don't know squat about why engines fail - but Miata motors (including my own) have run far above 222whp (and 13psi) on stock pistons and stock rods.

I'm curious to what others think about your images.

I'll try to add more info.
https://cimg0.ibsrv.net/gimg/www.mia...3380cf513.jpeg

https://cimg8.ibsrv.net/gimg/www.mia...b1b2503b0.jpeg

https://cimg6.ibsrv.net/gimg/www.mia...7fb630350.jpeg

Piston indeed looks strange.

Your fueling is on the lean side, timing isn't conservative either (is that a 99 engine? These have higher compression) and on 95 ron (?) + 30°c temps in Italy (my mum's from Napoli!), you can expect some knock, especially with a bad tank of gas.
It's most likely a combination of all of the above, but I would search a different tuner.

What turbo is that? That's roughly 200wtq at 2800rpm, crazy!

The turbo Is an IHI TD04L -13TIt's a 1995 engine 9:1 ratio running with 95ron when the engine fail but has been tuned with 100 Ron.
The tuner tell to me that i can use It even with the 95 Ron.
I cannot understand why the knock sensor has not worked.

Wait, the tuner TUNED THE CAR ON 100 and said "you can fill up with 95 and be good"?

No wonder... I'm running a 1994 rods only engine (8,8:1) and only put in 100+octane and my timing map isn't as "aggressive" as yours. It's the mid range I'm talking about.
That tuner should be slapped with a big ass Spianata!

Can you try to explain to me where my timing Is aggressive in that map? So i can talk with him.

Now I m rebuilding the engine with wiseco 8.5:1 83,5mm bore.

Midrange, 110-170kpa. But the real fault is the statement "put 5 oct less fuel in it and give it the beans"...
You tune on 95 and put 100 in just to be safe... Bad fuel, excessive heat etc

Thankyou for your help.
What do you suggest for the New build?

Lower compression pistons OR more conservative timing map OR switch that enables a secondary timing map that has more conservative timing map for lower octane gas.

My personal choice would be the switch - and run high grade gas whenever possible. I'm interested in hearing other opinions.

This time I am gonna rebuild It with cast wiseco pistons 8,5:1 83,5mm.

Im interested in hearing all the opinions too!


​​​​​​

Probably went lean. Also, timing at 200kpa @ 2300 ish is aggressive for pump gas IMO.

You mean for the 95 ron?

Euro-spec 95 RON is approximately 90.7 in US-spec R+M/2.

So, yeah, that's not especially high octane relative to your timing and mixture for >200 HP.

That engine ran lean and hot, and probably experienced lot of detonation.

Which is what we already knew from the first photo you posted.

190 kpa is not outrageously high for a completely stock 1995 1.8 liter engine, assuming that the fuel mixture is correct and the ignition timing is conservative.

Am I reading that timing map right, 35 degrees at idle?

Your tuner blew it up. Find a new tuner.

Does it really bug anyone else that everything is 'specified' to the thousandth of a degree / VE% / AFR target?

The only thing I can figure is that there was very heavy use of interpolation between various bits of the map, but I still can't figure out why the software/ECU lets you specify that level of accuracy when there's no hope it could physically ever meet those targets.

I read that, too. I don't know how dude's can run a company and TAKE MONEY for this kind of SHIT

Fueling looks more like a modern turboed engine than a tuned 80s engine in mid boost. This can also lead to transient fueling det depending on enrichment settings. I'd run safer - a bit of fuel use is a low cost for safety margin. At 200KPA on std compression and 95 - I'd be flooding it until I knew it was safe.

Agree that timing on mid boost looks too sporty on 95. Timing at 180 - 200 KPA which youre targeting then drops off a cliff and looks low so almost running boost for the sake of it.

I'm an armchair critic and novice mapper but it looks lazy, inconsistant and has probably cost you you're engine if tolerances were good. The pistons looks to have picked up so it does look potentially hot and tight although the top ring is still in one piece.

Also look potentially like mapper concentrated on ramp runs at desired higher boost then worked back and interpolated or blended badly to a hot base map in the mid boost range instead of starting low and building up. Only a guess.

Injector Base fueling VE looks far too low on boost as well so potentially a setup issue with injector settings. Doesn't mean its not hitting the targets on that map as may be mapping around wrong settings but values look wrong.

From everything i have experienced first hand it strikes me that the BP is extremely prone to mid range knock. I have a forged bottom end(9:1) w/ a vvt head running a 6258 and the thing will knock like mad anything between 2500 and 4500 depending on ignition timing and VVT settings; even on ethanol(65% or so at the pump). I have also experienced this on stock blocks which is even more terrifying.

I have essentially given up on trying to maximize power in the midrange and instead chose for a safe relatively moderate timing and VVT settings instead so it runs smoothly on the street and lasts a long time.