Engine failure
 

Hello Gents

From the heading you can see i have some bad news. This happened a little over a month ago, when i was getting the car tuned at RT tuning. The motor blew on the dyno during a pull. The car is a stage 1.5 GTM SC kit getting tuned for flex fuel (using vp C85). Car does have 70k miles and made a little over 500 on pump.

Based on the feed back from Vince and the shop, they were making a pull and noticed white smoke out the exhaust, so they immediately stopped the dyno session and put it aside. At first they thought it was a blown head gasket, but when they pulled the intake manifold there was parts of aluminium/piston in the manifold. :eek:

Based on the feedback and the options at hand i decided to take the car home where i would just swap in a new motor.


Here is what i found so fair..
Right off the bat when i picked up the car, i noticed the fuel pressure gauge was foggy.

http://www.the370z.com/members/jmroy...0-img-8880.jpg

Once i started to take the car apart it looked like fuel was inside the actual gauge. I primed the fuel pump to confirm, low and behold fuel come pouring out the top of the pressure relief valve. This is an basic aeromotive fuel pressure gauge, part of the cjm fuel return kit. Just bad luck and the gauge failed at the wrong time or what??? Gauge failed on a pull.. fuel pressure dropped.. went lean... caused the motor to detonated?? Based on the amount of aluminum chunks and pieces of piston rings in my upper and lower manifold id say the ring butted and blew apart the piston?

Does this sound like a likely cause from everyone? Never seen a fuel pressure gauge fail like this before but its all over the internet so..

Here's a few pics for giggles

http://www.the370z.com/members/jmroy...2-img-8918.jpg


http://www.the370z.com/members/jmroy...3-img-9215.jpg

No fun. Having issues sucks.

Ouch. Are you using EcuTek? They have failsafes that should prevent a lean condition...knock control and AFR failsafe should always be on especially when your dialing your tune in. In your second picture is the valve bent? You may have Possibly broke a valve spring, dropped the valve, hit the piston, got smooshed then went boom. Sorry for your loss!

Sorry to hear about your engine failure. Your decision to swap in a replacement stock motor is probably the most efficient way to get the car back up and running, especially for the power you were making since its not usually enough to take out a VHR.

Those gauges tend to last a few years and then the heat and vibration get to them. I have seen them fill up with fuel before. I dont think youll get enough fuel through the gauge to lean out the engine, but running that fuel you are going to have a hard time getting it to knock even if you did run it lean. Especially all in just 1 single pull, while in the middle of being tuned with a tuner watching and logging A/F on each pass.

So are you saying fuel was still filled inside the gauge and it still was pouring out of the fuel system, essentially dumping fuel?

If so then yes, that amount of fuel could cause a lean condition. If it just filled the gauge then I dont think that would be enough fuel lost to have the motor let go.

Why wasnt someone watching the gauge? I mean, that gauge is there for that one reason only, when tuning. Its not like you can actively watch it at any other point in time.

Edit: In looking back at the picture it looks so fogged up that fuel must have been in there for a while. Again, didnt anyone see this before tuning started or was occuring?

Hey Guys, my suspisuion is a cracked ringland when we first started tuning it. It was a little bit low on 93oct compared to the other 1.5 cars I've done even though he had a smaller pulley. When the motor let loose watching the data logs the knock went from -1 to -10 instantly and let loose. AFR were good and power was climbing right up till the failure.

As far as the gauge we noticed a drip coming from the gauge after the dyno sesion. At no point did it leak or spray fuel in the dyno.

When i got the car back fuel would pour out the top of the gauge just from the pump priming. If the afrs looked good during tuning then its prolly not the cause of this. It could have been a bad ringland, the motor was old and most definitely tired. Its been boosted since day one. Im not bashing anyone or blaming any products.. this is just part of the game

I say you got your money out of that stock block. Drop another one in and drive another 50-70,000 miles

I agree! The new engine is already in my garage :tup:

Agreed! I just care to make sure that its understood that an old leaky gauge, while it certainly needs to be addressed immediately, doesnt seem like it could realistically cost you an engine in the time-span of a single full throttle pull. Since any fuel leaking at all is too much, I am sure that a small leak looks significant to the naked eye. But if its not blasting out of there, I dont think youd have been at risk of running lean unless your fuel system was already on the edge. I think the larger concern is just the fuel leak itself, as a hazard for the entire vehicle.

Yeah, i understand completely; based on the feedback from Vince, it sounds like a small fuel leak doesnt have any affect on the fuel trims anyway.

Its all completely circumstantial. Using random numbers, say you have 300lph of fuel available before pressure drops, and your engine is consuming 250lph of it, then this means you can "afford" a leak of 50lph before pressure begins to drop. Your fuel consumption with a centrifugal supercharger will climb to it's peak at redline. So the closer to redline you get, the less you can lose to a system leak before its causing an immediate problem.

So you can definitely leak enough fuel to tax your fuel system to the point of running the engine lean. Only you saw how much was leaking, so none of us can say with absolute certainty whether its enough to cause a lean condition. But I have only ever heard of these gauges dripping or oozing a little, I have not yet heard of one really letting it go in a significant way, or basically bursting mid pull.

If it is truly leaking a whole ton, I would like to get it back to the manufacturer.

So is that valve guide broken and valve bent in that second pic? Any more pics of with the valve cover off? At least you have some rare moon rocks you can display now!

No broken valve or guides that i know of. Crazy to think that pieces of the piston made it passed the intake valve. Cant imagine what the combustion chamber or seats look like

I plan to disassemble the motor in the near future to see what happened. I can post more pics at a later date.

We call that condition "lifting the lands" in these parts.

i.e. What happened to your motor on that run?... "ahh it just lifted the lands".

Sucks man.