[iqraceworks]

Well, I finally got around to doing some more troubleshooting on my rough idle issue that popped up a while back. Did a compression test...all are 160-165psi.....except #4. It's only 55psi 😕 what's the best way to figure out if it's a ring/piston issue...or possibly a valve/spring issue? The plug for #4 looks pretty dark and sooty.

I guess that either way, the head needs to come off first. Right?

[iqraceworks]

Dumped a little oil into the cylinder, psi jumped up to 120. Guess it's definitely broke ring or piston ringland.

[The_E92_Fan]

RIP. Built block this time? At least do pistons rods and head studs.

[iqraceworks]

Originally Posted by The_E92_Fan

RIP. Built block this time? At least do pistons rods and head studs.

Yeah...not sure how much I want to invest into it, but it's definitely going to get a set of forged pistons in it. I'm pretty happy with the power it was making (585-ish)....so at this point I'm just wanting to make it reliable enough to handle that power without breaking another ringland.

The narrow gap on the rings is what actually breaks the lands, so I'm wondering if the stock pistons might be fine as long as I gap the new rings a little bigger. It's not like I'm running crazy amounts of boost (25psi).

I guess I need to get the motor out first and open it up...see what I find.

[suspect]

Originally Posted by iqraceworks

Well, I finally got around to doing some more troubleshooting on my rough idle issue that popped up a while back. Did a compression test...all are 160-165psi.....except #4. It's only 55psi 😕 what's the best way to figure out if it's a ring/piston issue...or possibly a valve/spring issue? The plug for #4 looks pretty dark and sooty.

I guess that either way, the head needs to come off first. Right?

That’s bad news. My symptoms are identical to yours where there is a very slight stumble not visible on rpm and one plug is dark and sooty. I’d have thought that much compression loss would’ve been more than just a slight stumble at idle. WOT would feel like there’s no power or mpg would suffer.

Do you have to hold the throttle body open when doing a compression test on N54? If so how?

[iqraceworks]

Originally Posted by suspect

That’s bad news. My symptoms are identical to yours where there is a very slight stumble not visible on rpm and one plug is dark and sooty. I’d have thought that much compression loss would’ve been more than just a slight stumble at idle. WOT would feel like there’s no power or mpg would suffer.

Do you have to hold the throttle body open when doing a compression test on N54? If so how?

Yep....sounds identical to what mine was doing. It actually still ran really good....just had that weird bobble feeling at idle, not enough to see an rpm change but you could feel it through the seat.

As far as the compression test....nope, just crank it enough times until the needle on the gauge finally stops climbing. It was pretty easy...just make sure you unplug all the connections on the injectors.

I have a bore scope....thought about putting it through the spark plug hole to see what I can see in that cylinder.

[suspect]

Originally Posted by iqraceworks

Yep....sounds identical to what mine was doing. It actually still ran really good....just had that weird bobble feeling at idle, not enough to see an rpm change but you could feel it through the seat.

As far as the compression test....nope, just crank it enough times until the needle on the gauge finally stops climbing. It was pretty easy...just make sure you unplug all the connections on the injectors.

I have a bore scope....thought about putting it through the spark plug hole to see what I can see in that cylinder.

Did the bad cylinder show up different on INPA rough running? What were your fuel trims like?

Looks like compression test is next on the list. Was also thinking of doing walnut blast as I don’t think it’s been done.

What adapter do you use for compression tester?

[iqraceworks]

Originally Posted by suspect

Did the bad cylinder show up different on INPA rough running? What were your fuel trims like?

Looks like compression test is next on the list. Was also thinking of doing walnut blast as I don’t think it’s been done.

What adapter do you use for compression tester?

I never hooked it up to INPA. I did use MHD to run some logs at idle. The fuel trims were all great, AFR's were good, VANOS numbers all good.....as far as the data goes, everything was fine. No codes...nothing.

I just felt that odd idle that felt slightly rough...that it.

My compressor tester kit came with several difference spark plug thread adapters...I just picked the one that fit

[whyzee125]

That sucks man, sorry to hear it. Hope she gets built back better than ever!

[iqraceworks]

Originally Posted by whyzee125

That sucks man, sorry to hear it. Hope she gets built back better than ever!

Yeah...that this point it would be a waste to not rebuild the motor.

[oVeRdOsE.]

quick question, what would be the most probable cause?

lean due to a faulty injector?

[suspect]

Originally Posted by iqraceworks

I never hooked it up to INPA. I did use MHD to run some logs at idle. The fuel trims were all great, AFR's were good, VANOS numbers all good.....as far as the data goes, everything was fine. No codes...nothing.

I just felt that odd idle that felt slightly rough...that it.

My compressor tester kit came with several difference spark plug thread adapters...I just picked the one that fit

Great engine. Runs fine even when broken

I think the thread is M12.

[iqraceworks]

Originally Posted by oVeRdOsE.

quick question, what would be the most probable cause?

lean due to a faulty injector?

From what I've found....broken ringlands is a pretty common issue with these motors. Could have been an injector going bad causing a lean condition, could have been bad luck, could have been too much boost? Could have been just the fact that the OEM cast pistons can't handle much more than 600hp? Hard to tell really........

[suspect]

Originally Posted by oVeRdOsE.

quick question, what would be the most probable cause?

lean due to a faulty injector?

iq had a leaky injector so could be oil contaminated with fuel. Could also be slightly bent rod wearing out compression or oil control ring.

[suspect]

Originally Posted by iqraceworks

From what I've found....broken ringlands is a pretty common issue with these motors. Could have been an injector going bad causing a lean condition, could have been bad luck, could have been too much boost? Could have been just the fact that the OEM cast pistons can't handle much more than 600hp? Hard to tell really........

Even my completely stock motor is suffering with same issue.

[oVeRdOsE.]

damn, those engine got 99 problems , but internals shouldn't be one.

twins are hard on the engine, more torque at low rpm.
Looking for a 6062 gen2 to to begins.

I want to prevent any internal failure if possible. Ill recheck all injectors adaptation. I have 3x index 12 and the 3 others are stock.

[iqraceworks]

Originally Posted by suspect

iq had a leaky injector so could be oil contaminated with fuel. Could also be slightly bent rod wearing out compression or oil control ring.

I don't think so...but who knows. That leaky injector wasn't leaking very much, didn't even affect cold startup like a leaky injector usually does......and the oil only had 1000 miles on it.

I think at this point, there are enough people out there I've seen who are making similar power (close to 600) who have had the same issue. I think once you push these motors with the stock cast pistons over 600hp and 25+psi boost, it's just a matter of time.

I'm assuming that if I rebuilt it with forged pistons and rods....it should be pretty reliable at the current power it's making?

[iqraceworks]

Originally Posted by oVeRdOsE.

damn, those engine got 99 problems , but internals shouldn't be one.

twins are hard on the engine, more torque at low rpm.
Looking for a 6062 gen2 to to begins.

I want to prevent any internal failure if possible. Ill recheck all injectors adaptation. I have 3x index 12 and the 3 others are stock.

My tune was setup to be pretty easy on the motor....low/mid rpm torque was pretty low, and the boost would ramp up in the higher rpms. The entire reasoning was to take it easy on the rods. Who knows.....cast pistons really aren't that great for big power apparently.

[whyzee125]

A failing injector seems pretty likely to be the culprit to me as going lean under high boost produces an insane amount of heat in the cylinder if that were to ever happen. You already know you had a leaky one on that cylinder so seems quite likely that caused it. The O2 sensors only measure across the whole bank so one could easily go a bit lean without throwing your AFR readings off much in a log, especially if the other cylinders compensated.

[oVeRdOsE.]

Originally Posted by iqraceworks

My tune was setup to be pretty easy on the motor....low/mid rpm torque was pretty low, and the boost would ramp up in the higher rpms. The entire reasoning was to take it easy on the rods. Who knows.....cast pistons really aren't that great for big power apparently.

define big power. For a road car, able to go from 300bhp to the near 490bhp on stock turbos, or 6xxbhp on aftermarket turbos without taking the engine apart this is huge power imo for stock internals.

If you check audi world, on unitronic webpage, you dont see any doubling power on stock internals.

Originally Posted by whyzee125

A failing injector seems pretty likely to be the culprit to me as going lean under high boost produces an insane amount of heat in the cylinder if that were to ever happen. You already know you had a leaky one on that cylinder so seems quite likely that caused it. The O2 sensors only measure across the whole bank so one could easily go a bit lean without throwing your AFR readings off much in a log, especially if the other cylinders compensated.

right O2, I saw a lot of post on that, but on other platform people get rid of this issue using 90° elbow tube to keep the o2 away from flame/excessive heat and still have good reading, and I never saw any discussion on e90post about this solution.

is it because it's been tested and has no effect? or nobody tried.

very popular on audi/vw engines.

something like this (an no this is not for space in that case, but really to avoid O2 get destroyed or check engine code)

[whyzee125]

Originally Posted by oVeRdOsE.

define big power. For a road car, able to go from 300bhp to the near 490bhp on stock turbos, or 6xxbhp on aftermarket turbos without taking the engine apart this is huge power imo for stock internals.

If you check audi world, on unitronic webpage, you dont see any doubling power on stock internals.



right O2, I saw a lot of post on that, but on other platform people get rid of this issue using 90° elbow tube to keep the o2 away from flame/excessive heat and still have good reading, and I never saw any discussion on e90post about this solution.

is it because it's been tested and has no effect? or nobody tried.

very popular on audi/vw engines.

something like this (an no this is not for space in that case, but really to avoid O2 get destroyed or check engine code)

That's not what I'm talking about here, his O2's are fine but his piston/ringlands may have been damaged from heat. Yes, people do this with ST manifolds sometimes or there are heat sinks you can buy but totally different issue.

[AWD Addict]

Sorry IQ! Keep us posted on what your plans are.