NED Import Madness 9/25/10

[FazdaBoy4ever]

my log of the partial/final run showed unstable AFR's spiking into the mid 13's at full boost. this could have been due to raw fuel being dumped into the exhaust if that cylinder was not firing at all. from what i understand, misfires where fuel passes through the engine unburned will show up as lean on a wideband.

Yes, but its not the fuel, when a cylinder doesnt fire it doesnt convert fuel and oxygen into CO, CO2, NOx, and H2O, it pumps raw fuel and O2 into the exhaust basically an oxygen pump and the sensor that uses oxygen in the exhaust gets a understandably false reading.

that plug is nasty, hopefully the cylinder is in good shape. I would tend to think especially considering your misfire was under load, that the plug was the reason for your misfire (duh) and not some nearly catastropic engine failure or melted piston, burnt valve, etc... as those concerns would continue missing after the plug was replaced. you may be totally onto something with an injector concern, its the only thing that I could think would burn up a cylinder like that.

[therieldeal]

i didnt run it hard after replacing the plug, so there is probably still some sort of underlying cause that i need to locate and fix. if it is a faulty injector i'm not going to be too happy, considering i bought brand new deutschwerks injectors just last fall, 3k miles ago

i'll pull the other plugs and get pics of them too, i was going to do it tonight but it was raining


also i understand the concept of why it shows up as "lean", its just easier to say unburned fuel than "unburned air/fuel mixture" lol

[yunvmyegt]

this kinda reminds me of the day i was out beating the crap outta my car, shift into 4th at around 7k and a plug wire popped off the disty..... i thaught my motor was done.....lol..... wound up getting lucky and popping the hood to see arc's hooked it back up and went on my way..... hopefully you didnt do anything too bad....

[crazycanadian]

The plug looks like it broke.. I don't see any signs of it melting or anything that would indicate you going lean..

If it were my car I'd check the plugs, do a compression check, if its easy I'd have a look at the exhaust wheel on the turbo.. If that checks out ok, I'd go run the **** out of it and see what happens...

[therieldeal]

The plug does actually look like it melted, I need more light and a better camera I guess. I'm sure if I cleaned it that would help too, it's fouled completely black from misfiring after the electrode came off. It also has little flecks of molten metal stuck all over it, a telltale sign of detonation. Still waiting to borrow the borescope... it finally stopped raining though so I should be able to do a comp test this evening.

[yunvmyegt]

sounds like what i told him last night.....lol...

[FE3-323]

put some ****ing iridium's in! lol im anxious to see what the bore scope shows. & if there is any damage in the chamber

you must of had that clyinder extremely hot. or a faulty plug of some sort.

[therieldeal]

i think the gauge on my comp tester is reading low, cyl 4 read ~95psi, all the other cyls were ~105-110. theres no way the comp is actually that low, i threw new plugs in it and took it for a spin and it still rips. still waiting to borrow the borescope......................... always waiting for something, story of my life with this car.

[ajax]

I wouldn't worry about a 10-15 psi difference between one of the cylinders. You're looking for a difference of like 25% for a cylinder to be considered to have "low compression". 105-110 does seem a little low but there are several things that can affect cylinder pressure readings and it wouldn't mean that you have low compression in all cylinders.

[FE3-323]

a change in CAMS is likely the culprit jon. adding duration or changing the degree position of the intake valve closing ABDC will raise/lower dynamic compression.

the Web cams you installed are likely the crazy compression difference you see.
sides that the GTR is low comp to start with.

what specs do you have for your web cams???