Blown Motor @ 11psi

[igdrasil]

Update:

New Pictures added (digital camera), better detail, engine is out of the car.. (under the old pics as attachments)

For the people that doesnt know what happened:

I was boosting 11psi and found an STI on the streets so I decided to test drive my tune. For my surprise, I won all 4 races agains the STI. All 4 where not from the hole but rolling on 1st gear.

Anyway, this I was just racing alone...I left the STI way behind. I went WOT in 4th gear, the A/F was showing 13:1 but the EGT was showing cold exhaust temps ~1150, so I kept flooring it and BANG...the engine died on me, lots of smoke, vapor and oil all over the place.

Now, this is what I still dont understand. I found something interesting...

My intake cam was broken where the sproket is and 1 intake lifter (if its that how is called, first pic). Looks like the cylinder 1 got the valves stuck open. Both rods 1 and 4 broke, piston 4 broke and block damage all over the place.

I must admit that on the mornings, the was a ticking sound comming from the cover, like a lubrication problem on the cams/valves...so all cold starts had this ticking sound, but gone after a couple of minutes.

I really dont know what happened!!

Enjoy the crappy pictures...I lost my digital camera...so all I have is the handycam to take pics.

 

[Captain KRM P5]

wow man, i think those are the only blown engine pictures i can say are worse than mine. nice work. if there is any way i can help you out please let me know.

 

[Metal MP5]

that sucks man

what are the plans now ? Just replacing the engine or you're gona build it up this time ? (assuming this one wasnt forged)

 

[Matthew]

damn dude, what engine are you on now?

 

[changedman]

ya, what matt said!!

this is making me VERY hesitant on going FI

 

[Pirana]

Sorry to hear that....are you going to rebuilt?

 

[protegeV]

rebuild time...dun give it up

 

[Captain KRM P5]

ya, what matt said!!

this is making me VERY hesitant on going FI

i've been running over 30k on the new motor without any problems whatsoever. Then again, I've never really gone above 6 or 7 psi during that time.

 

[FrigginGLI]

11psi on that kit is alot is it not? Nice kill, but was it worth the blown engine.

 

[Matthew]

without being forged its a good bit i would say. i would bet that 11psi is making around 250ish whp or more.

 

[Kooldino]

without being forged its a good bit i would say. i would bet that 11psi is making around 250ish whp or more.

Nah, not THAT much power.


igdrasil - What told you that your A:F was 13:1? A narrow band or a wideband?

 

[TurfBurn]

Do you think that the piston slammed into the valve and snapped the components you see damaged in the cams and so forth? Is the valve damged or bent at all? That was my only thought as to how some of the damage could have occured.

 

[ghost]

<--adjusts psi to 7psi

 

[flat_black]

Hrrm... This is the third one I've read about with similar symptoms... Cold EGT and a decently rich mixture. My guess is that piston number one went first, then the rest died from there. Looks like a chunk of the piston got jammed, and jarred the valves open, too. That's really nasty. =/

 

[TurfBurn]

Mine blew up on Monday running 8 psi... soo . LOL... but anyway... viewed from the drivers seat cylinder number 4 is the one to the far left (so far right when you are peering into the engine bay) based off what the shop manual shows. If it is other than that I'd like to know. But by that convention my number 4 cylinder is what had the rod snap. I haven't seen what the pistons look like yet... but the rod is GONE

 

[mp5jeff]

that sucks dude...

 

[LinuxRacr]

I think you have caught me on the number of blown engines!! Yeah, I just realized that the engine I have in my car now has been in the longest, and it started life in a 626! (eek) The valve probably got jammed open when the piston slammed into it. My old head shows the same thing with the stuck valves.

 

[badAzLava3]

Damn....
Those are some ugly pictures....

Don't ever believe just the EGT's and think that you are okay.maybe a head gasket was starting to go.....

AFAIK, a 13:1 A/F ratio is pretty lean for 11psi...
A Mazda 2 liter motor at 11psi is probably doing 230-240hp.

I think the EVO's and STI's are fueling in the high 10's and low 11's when they are in boost. I like to see my AF peg rich when I romp on the boost, myself.

After losing 2 1.8 motors,one via a friend romping on a cold car, and the second being a tired 10yr old OE fuel pump, I now have the forged stuff in, but I added the big ass fuel rail and a big ass fuel pump to try to get anti-lean insurance.

I ran #4 lean because the fuel return is btwn 3 and 4 on the Miata, so at least make sure you have a dual feed fuel rail in if you are not doing both.

The later model Mazda OE rods on 99+ Miata's don't take a lot of boost, so above 9psi, you are rolling the dice.

Good luck.

 

[Kooldino]

Damn....
Don't ever believe just the EGT's and think that you are okay.maybe a head gasket was starting to go.....

*Ahem*

http://www2.msprotege.com/forum/showthread.php?t=39881&page=22&pp=15&

AFAIK, a 13:1 A/F ratio is pretty lean for 11psi...

Yup. And it was 13:1 according to a narrow band, AFAIK.

A Mazda 2 liter motor at 11psi is probably doing 230-240hp.

Yup.

I think the EVO's and STI's are fueling in the high 10's and low 11's when they are in boost.

Yup.

http://www2.msprotege.com/forum/showthread.php?t=39881&page=22&pp=15&

 

[ghost]

WOW!! Dino Im trusting your word that all is well with 7psi,lol