Technical #4 Cylinder is dead…any ideas as to what caused the failure?

[IQraceworks]

What's a typical leakdown rate for a fresh motor? I ran through all of my cylinders, and they are all between 5-7% leakdown rate.....cold, with rings that haven't been seated. I'm assuming that's pretty good for a fresh build?

Thought I was going to have it all back together by the weekend...but FCP Euro sent me the wrong timing chain kit, so that was a little bit of a setback. I did go head and install the "updated" BMW N54 crank hub. The friction rings are quite a bit more grippier, and have more surface area that the old style.

Can't wait to get this thing fired up!

 

[IQraceworks]

Well....the engine is finally in the car! What a relief! Now it's just time to hook up the exhaust, and the 8 million electrical connectors. Hopefully I will get it fired up soon!

 

[SlowE93]

Hopefully you don't have issues with head gasket

 

[SlowE93]

Progress update ?

 

[IQraceworks]

Slow but steady......this is taking way longer than it should! But between servicing all of the fuel injectors I'm helping people out with, and family stuff....free time it at a premium. It's a bad sign when my daughter has time to sneak into the shop and write stuff all over my car in all the the dirt that's accumulated on it!! As soon as this thing is running again..it's getting washed!!

Got the downpipes, exhaust, and transmission brace all hooked back up...next step it to tackle all of the wiring, cooling lines, and then hopefully get this thing fired up!!

 

[seb.apprenti]

To begin with, thank you for this post. When your problem started, did you notice a drop in your negative boost at idle? my negative boost is currently at -8.4 PSI...I haven't found any leaks. but I have another problem. my twins are making a weird noise...they are popping up. apparently it could come from one turbo which spins faster than the other, due to a compression problem. the logs are good, no defects, no abnormal noise or smoke. my twins are HYDRA. I'm doing my compression measurements on Thursday...I admit that after reading your post, I'm not really reassured

 

[SLOWESTN54]

To begin with, thank you for this post. When your problem started, did you notice a drop in your negative boost at idle? my negative boost is currently at -8.4 PSI...I haven't found any leaks. but I have another problem. my twins are making a weird noise...they are popping up. apparently it could come from one turbo which spins faster than the other, due to a compression problem. the logs are good, no defects, no abnormal noise or smoke. my twins are HYDRA. I'm doing my compression measurements on Thursday...I admit that after reading your post, I'm not really reassured

I recommend a Leak down test over a compression test, It'll give you a more definitive answer of is somethings wrong.

 

[IQraceworks]

To begin with, thank you for this post. When your problem started, did you notice a drop in your negative boost at idle? my negative boost is currently at -8.4 PSI...I haven't found any leaks. but I have another problem. my twins are making a weird noise...they are popping up. apparently it could come from one turbo which spins faster than the other, due to a compression problem. the logs are good, no defects, no abnormal noise or smoke. my twins are HYDRA. I'm doing my compression measurements on Thursday...I admit that after reading your post, I'm not really reassured

My car was actually running pretty good....but I started to notice a slightly rough idle, I mean really slight. That, and if I got on the gas hard I would notice a little smoke out the exhaust. I'm assuming the broken chunk out of the piston and broken ring is what caused that

If your turbos are making a weird noise, I would say the problem is with your turbos...and not your engine. But yes, a compression check is a good place to start. When I did my compression check....all the cylinders were around 170-175 if I remember right, except #4...it was down around 60psi, it was the one with the broken piston ringland.

 

[seb.apprenti]

Thank you for your answers. I will start with a compression test because a friend lent me the tool, I will surely do a leak test afterwards depending on the result but there is no one around me who has this equipment (I live on a small stone lost in the Indian Ocean ...so I don't have quick access to parts or tools). If I really lost a cylinder, I know the cause. not having an e85, I installed a methanol port, 6 nozzles on the collector, one in the charge pipe. on my first assembly I did not have a non-return valve on the nozzles... just a solenoid on the distributor. I made big blue flames and the detonation was worthy of a military attack. I even burned my 02. I didn't do much acceleration in these conditions. I quickly brought everything back into compliance... but I think the damage is done. At this stage I really hope that my problem is with the turbos even if they are new. if this is the case I switch to a small single to obtain 550/600whp. but if it's the engine it's going to take me a long time to rebuild. If you give me permission, I will give you the result of my test here

 

[IQraceworks]

Well....I finally got her fired up!

 

[r0nd3L]

Nice work! Motor sounds good and I hope it runs well for a long time.

Thanks for sharing the journey, despite some of the haters on here

 

[IQraceworks]

Well....I got the motor all fired up, and it's running great! Those Mahle coated pistons are nice and quite at startup, not like some of the forged pistons I've had in other engines. Nice and smooth at idle, the thing runs awesome! I have about 200 miles on the break-in oil, just putting it through some heat cycles and trying to get the rings seated in good. I think this project can be put to bed.

 

[wheela]

Once you're done breaking in and get back to doing some WOT pulls, would you mind following up if you run into any false knock? I've heard conflicting stories if this is an issue with built engines, or at least at what level of "built" it can become an issue. I suppose like anything, it depends on a lot of other factors. But you've done a great job calling out specific details of your build, so I think this will be a good data point

For reference, I've seen one other person (f80 forum) claim no false knock with just forged pistons.

 

[IQraceworks]

Once you're done breaking in and get back to doing some WOT pulls, would you mind following up if you run into any false knock? I've heard conflicting stories if this is an issue with built engines, or at least at what level of "built" it can become an issue. I suppose like anything, it depends on a lot of other factors. But you've done a great job calling out specific details of your build, so I think this will be a good data point

For reference, I've seen one other person (f80 forum) claim no false knock with just forged pistons.

Yeah, I've seen a few forum posts over the years from people with built forged piston motors saying they had false knock. That was one think I wanted to make sure I didn't run into. I reached out to several well knock N54 engine builders, and also Mahle asking them about false knock issues. The engine shops, and Mahle all say that with the coated Malhe pistons, they have never once had a report of false knock issues. I've made a few hard pulls, and so far...no false knock issues at all.

I'm just guessing there.....but I bet most of those false knock issues are from people throwing a motor together with way to big piston to wall clearances, or pistons with bigger than stock compressor rations. Unfortunatly, the couple of posts I've seen about "false knock" after their forged piston builds.....don't include any data, or factual information at all.