Well THERE"S my problem... tear down pics

[OrangeSVT03]

Well we just got the head off and low and behold I managed to break another piston. We were pretty sure it was heat related... the good news was there is ZERO damage to the cylinder!!!!!!

Anyone guess where the bad spots are..........










I'm going to pull them out tommorrow and give the other 3 a good going over and then I'll have to decide what to do next.

[ClintB1321]

what piston were these?

[IslandFocus]

Probe correct?

[OrangeSVT03]

For those of you that dont know the "back story" I had been trying to figure out an electrical issue... the issue caused the car to run rough and the EGT's to go WAY high. Well when I finally figured out that it didnt do it when I unplugged the J&S the car had started smoking just a little, so I went ahead and did one last datalog it.

During the datalogging I would drive it with the J&S plugged in then unplugged and you could see an absolute difference... you could definitly see on the logs where I would unplug the J&S.

I do not blame J&S for the incident... John makes a GREAT product and has offere to check it out for me... and hopefully I'll get to ship it out next friday.

Could the J&S have caused it??? Sure .... BUT its a piece of electronics and sometimes things go wrong no matter how well made things are.


The pistons are Probes, there is NO signs of detonation like you would expect to see. I feels its purely heat related due to the retarded timing.... and there's no cylinder damage (thats TWICE that I've been lucky like that).

If the other 3 pistons check out, my plan is just to replace the 1 piston and re-rings all 4.... no sense in replacing stuff that isnt broke.

[CatMostFeared]

get it right and get the 400whp mark

[ZtsFucus]

how much boost were you pushing during these logs?

so when you unplugged the J and S the EGTs dropped?

[-Rudel-]

Damn; just as Cat says, "get it right and get the 400whp mark"

[OrangeSVT03]

Originally Posted by ZtsFucus

how much boost were you pushing during these logs?

so when you unplugged the J and S the EGTs dropped?

Wiht the J&S plugged in it wouldnt go past 4k rpms and maybe 7psi if that, unplugged it would run 7k and 20psi... just like it should have.

Yes the EGT's would drop as soon as I unplugged it... back down to normal.

[pocus]

what are you talking about I thought those were the custom super duper valve releaf pistons.

sorry to hear that man hope you get that up and runing soon.

[Gigaherz]

The same thing happened to me on my spi, no signs of detonation on my probe piston but a chunk was missing nonetheless. Happened on the valve relief on mine too!! I believe high egt's and inferior piston design were the cause. I feel your pain!!

[eg02svt]

Damn i was looking foward to the v8 swap LOL

[AcIdBuRn02ZTS]

possibly a design fault by probe? i'd contact the company considering the two very simular situations...

also sounds like the J&S was acting up... i'd be contacting them aswell...

good luck man!!
-AcId-

[strubmotorsports]

sorry for my ignorance whats a j&s

[OrangeSVT03]

a J&S is a standalone knock sensor setup.... its far nicer than the factory stuff.

www.jandssafeguard.com

[lil_silver_rocket]

Could someone explain in more detail and in "laymans" (i.e. Not the most tech savvy) terms how the J&S retarding timing caused heat failure of the pistons?

I'm a bit unclear on the connection, and would appreciate any & all enlightenment.

Thanks in advance!

[bryst06]

pure and simple. he knew he had a problem and went lil to hard on car and BOOOM.

[OrangeSVT03]

Originally Posted by lil_silver_rocket

Could someone explain in more detail and in "laymans" (i.e. Not the most tech savvy) terms how the J&S retarding timing caused heat failure of the pistons?

I'm a bit unclear on the connection, and would appreciate any & all enlightenment.

Thanks in advance!

When you pull too much timing the air/gas mixture doesnt explode in the cylinder it burns and it stays burning as it is pushed into the exhaust manifold.. so instead of a quick "poof" you get a slower, longer burn which causes cylinder temps (EGT) to go up.

Pulling to mich timing can and will have the same effect on an engine as going lean.

[OrangeSVT03]

Originally Posted by bryst06

pure and simple. he knew he had a problem and went lil to hard on car and BOOOM.

Right, I knew there was a possibility of toasting the engine, but I needed the datalog... since I had been chasing this issue for months and this was the first time it actually occured while I had the laptop hooked up to the car so I was going to get all the data I could.

[Dukman]

Out of curiosity, what EGTS were you seeing with the J&S active? And do you have EGT sensors on all pistons or just use one to get an idea. As most of the other pistons will (should) be in-line with those temps.

[OrangeSVT03]

I pegged the gauge.....

When the car ran normal... EGT were normal... as soon as it would act up the EGT went immediatly high and if you tried to maintain say 60mph they would just go crazy high.... it would only be seconds before the gauge would peg.... at 1600*

I only run 1 sensor on #3 cylinder since its usually the hottest.

[Dukman]

Originally Posted by OrangeSVT03

I pegged the gauge...

Holy ****!

That's definitely not a warm and fuzzy to see that.

[boostedzx3]

ahhh the beauties of high performance. There are some days where I wish I would have left my car alone......then I lay into the gas and the thought exits my mind quickly.

[Simon170]

What management do you run?

[j20000]

Where did the other 2 pieces of the piston go? Thats SUPER lucky not to score the cylinder wall or damage the head. They had to go somewhere though.

[belacyrf]

Originally Posted by OrangeSVT03

When you pull too much timing the air/gas mixture doesnt explode in the cylinder it burns and it stays burning as it is pushed into the exhaust manifold.. so instead of a quick "poof" you get a slower, longer burn which causes cylinder temps (EGT) to go up.

Pulling to mich timing can and will have the same effect on an engine as going lean.

Just to help clarify our power hungry, power obsessed, and overall nut-job friend of ours

The air/fuel mixture should never explode.
Air/Fuel mixture should burn smoothly and evenly all the time.

Timing refers to "WHERE" in the power stroke, the igniter lights the Air/Fuel to start it's burn.

Picture a piston moving up the cylinder. A piston moving up the cylinder with valves closed means it is on it's "Power Stroke" and will be compressing the air/fuel and will be mixing it at the same time (Google "Squish Area" for more info about the mixing). Advancing Timing means that spark is generated while the piston is lower in the cylinder while on it's way up, where Retarding Timing means that the spark is generated while the piston is higher (Higher = closer to the top)

What happens to air as you heat it? It expands!!!
This expansion is what creates the force that pushes the piston back down. Now you can imagine that if you advance ignition to much, then the air might expand too much and will fight the piston on the way up which can cause the piston to rock back and forth which is "Ping" or what we refer to as detonation (though nothing is really detonating).

True detonation or what is correctly called "pre-ignition" is when the air/fuel ignites by itself without the spark going off, which is never a good thing and is always to early. Also lean pockets in the air/fuel mixture can cause an uneven burn and can lead to deposits, less power, and higher EGT's as well, as it leaves fuel unburned or burning on the exhaust stroke.

Hopefully that clarifies the concept of timing and what retarding and advancing it does. Basically you want the burn to complete if it doesn't complete because of timing being retarded to much, then the burn process continues beyond compression raising EGTs (not to mention it leaves all the power on the table)