Zoom zoom BoOm x2.

[Bigg Tim]

Well wouldn't there have been the damage there by the dyno guy holding the rev's that high for so long? That's crazy he held it there. And what about the talk about the broken drivetrain? If something snapped in there, couldn't that make it over rev real quick and cause some damage too? If it was detonation and/or no rev limiter, the holding there for 6 sec had a big part to it too, if not the cause of it. I have rev'd high before, not that high, and the J&S came on from detonation, but I am still running. Anyone who would hold the RPM's up there for that long on a dyno is an idiot. How long does it take to do a dyno pull, maybe 10-20 seconds, and the extremely high rev's were held for 6 sec's of the entire dyno pull??? WTF!!! I never sustain a certain RPM during a pull, it's always moving. Why wasn't this guy watching the tach?

 

[Spooled]

Cutting ALL fuel is what you want to do... and that is how you rev-limit a car. Cutting spark is dangerous as dumping in raw fuel can cause washing and pre-ignition and detonation as well.

Gotcha. So if the extra injectors and the main injectors aren't cut at the same time, it will lean out for sure.

I still think that there is a possibility of an injecor failure in cyl. #1. It looks like it was pocked to hell, and the others looked fine in comparison. Any thoughts?

Edit: It could have been the revs that caused an injector to fail, too. Chicken or the egg...

 

[BlkZoomZoom]

It may have been that you leaned out. What is the stock rev limit on your car? It looks like you have the extra injector set to run to high in the rpms.
How much boost, what kind of fuel, what kind of intercooler, what were the arfs on the dyno?

Not entirely sure what the stock rev limit is. 6800-6900? 17-18psi. 6gallons of 107 mixed with 3gallons of 93. Intercooler is the smic that custommsp sells. Afrs? Good question. Didn't last long enough to get a clue.

I also think it's b.s. that all four pistons cracked in the same place.

 

[BlkZoomZoom]

Well wouldn't there have been the damage there by the dyno guy holding the rev's that high for so long? That's crazy he held it there. And what about the talk about the broken drivetrain? If something snapped in there, couldn't that make it over rev real quick and cause some damage too? If it was detonation and/or no rev limiter, the holding there for 6 sec had a big part to it too, if not the cause of it. I have rev'd high before, not that high, and the J&S came on from detonation, but I am still running. Anyone who would hold the RPM's up there for that long on a dyno is an idiot. How long does it take to do a dyno pull, maybe 10-20 seconds, and the extremely high rev's were held for 6 sec's of the entire dyno pull??? WTF!!! I never sustain a certain RPM during a pull, it's always moving. Why wasn't this guy watching the tach?

It's not entirely his fault. We both didn't realize it went that high until later when I remembered I datalogged the run and played it back. I was standing right next to it and didn't realize something broke until he let off and it shut off. It didn't really sound like it broke up or anything. It just kept climbing...

 

[BlkZoomZoom]

Gotcha. So if the extra injectors and the main injectors aren't cut at the same time, it will lean out for sure.

I still think that there is a possibility of an injecor failure in cyl. #1. It looks like it was pocked to hell, and the others looked fine in comparison. Any thoughts?

Edit: It could have been the revs that caused an injector to fail, too. Chicken or the egg...

If the injector failed it would have started misfiring. It wasn't misfiring.

 

[azian6er]

do pistons come pre-balanced from the manufacturer? Did you not do some of your own "modification" to the piston tops when you were doing your build? Not sure if that could have an effect or not, but at such high revs and load, a little unbalanced piston could be prone to crack in my opinion.

this really isnt my forte, but it looks as if spooled may be right... the stock 320 cc injector could have screwed up and led to an extremely lean condition. at 18 psi, those stock injectors are way past 100% duty, i am sure..

all i know is that what happened sucks, and it makes me paranoid.

-B

 

[azian6er]

If the injector failed it would have started misfiring. It wasn't misfiring.

maybe it was durring the 6 second stint at 7200 rpms +..... how could you even tell at that high of rpm?

 

[BlkZoomZoom]

I had the pistons balanced after I played with them. They were within a 1/2gram.

 

[BlkZoomZoom]

It didn't register any misfires through the pcm. Nor did I hear it misfiring.

 

[azian6er]

what about the duty cycle on the stock injectors though? regardless of whether it misfired or not, wont the duty cycle on them be through the roof at 18psi? i know the extra inj. setup will give the extra fuel needed, but what happens if one of your injectors craps out due to high duty cycle?

-B

 

[BlkZoomZoom]

The max voltage the pcm saw for the stock injectors from the maf was 4.58v. I highly doubt that they would go static from that low of voltage.

 

[igdrasil]

100%, thats why they failed. Now the questions is why did it detonate? Need to see the tune map.

HEAT I think, higher revs means its producing more heat, maybe the head is not optimized for such amount of flow, gases will get stuck in the chamber and problem begins.

Question is:

Does the head has some work on the exhaust port and valves?
Whats the exhaust trim on the turbo?
Any EGT peak n hold gauge? and is it located in the manifold or downpipe?

 

[BlkZoomZoom]

The head flowed around 190 on the exhaust side, it was plenty worked. The exhaust trim of the turbo was the stock T-25. No egt.

 

[igdrasil]

The head flowed around 190 on the exhaust side, it was plenty worked. The exhaust trim of the turbo was the stock T-25. No egt.

t25, small trim, check the turbine efficiency map, this is an issue. Im not telling that this was the reason that blew you engine, but you might want to change it.

 

[ddogg777]

How is this the case?

Just picture it in your head, if there were too much clearance between the ring landings and the wall then one side of the piston could have more room if it squished up to the other side. This could be microscopic difference that the unaided eye can't see. The rings could still be holding compression if they were ground properly, couldn't they?

How does a ring "toast" with out stroke?

I said with our stroke, not without. The tangential velocity of the rods to the crankshaft increases with the increased radius of the crankshaft (our cars have a greater radius than say, Hondas). So, at the same rpm, our pistons are moving faster than the Hondas. So, when our engines overrev, they are cruisin up and down really, really, really fast... From there, anything can happen and all problems are compounded. Perhaps the piston/wall clearance is fine and the rings were ground nicely and their was adequate lubrication. If that were the case, then the pistons/rings just couldn't handle it because it looks as if the rings broke the piston 'lips' right where Steve pointed it out, where there was least amount of aluminum.

@Blkzoom- How was your block honed? Was it align-honed on a machine?

@Turfburn- Ahhh! You meant ring grooves of the piston, not the rings themselves. I was like "How can the skirt be wider than the rings because the rings expand and touch the cylinder wall..."

 

[BlkZoomZoom]

Dont know. Block was a brand new one from Mazda. Not a reman.

 

[ddogg777]

Well, I still feel really sick for you. I will be doing the same thing on the dyno here this month-cross fingers!
Here's a picture of the machine that "straightened out" the cylinders on my block (#3 was out of line!). A good .02 overbore fixed it...

 

[igdrasil]

I dont see any pics of the ring lands to say that the rings broke the piston that way. A piston ring will not break the top of the piston that way. I think we all agree that those are meltings.

The only harm a piston ring can do like that is, like you said, @ high rpms the piston is moving way faster than a shorter stroked engine in any given rpm. The rings will be so damn hot that IF you have too much clearance, the piston ring will heat the mixture and become a potential hot spot on the chamber.

 

[ddogg777]

These are clear breaks: http://www.msprotege.com/forum/attachment.php?attachmentid=50072
http://www.msprotege.com/forum/attachment.php?attachmentid=50070
In the second one you can see where there is a crack from the forces pushing up.

I think you can even see the ring lands or rings in those pics too.

 

[TurfBurn]

I dont see any pics of the ring lands to say that the rings broke the piston that way. A piston ring will not break the top of the piston that way. I think we all agree that those are meltings.

The only harm a piston ring can do like that is, like you said, @ high rpms the piston is moving way faster than a shorter stroked engine in any given rpm. The rings will be so damn hot that IF you have too much clearance, the piston ring will heat the mixture and become a potential hot spot on the chamber.

My only concern at this point as far as those rings is if the ends butted and it jammed.. that piston would slam down on that ring with some considerable force... It looks like you can see the ring in one of those pictures right at the fracture zone.... But otherwise the only potential issue would be severe detonation, but I would think you guys would have heard it... The odd thing is how every single piston cracked on the same spots and tended to pop the right hand relief I believe more than the left...

Is the tranny indeed shot/broken??? or was the noise you thought was that some serious detonation issues.