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+--- Thread: What is considered excessive blowby in a Dyno? (/showthread.php?tid=3357)
What is considered excessive blowby in a Dyno? - rrod - 07-30-2018
I’m searching about this topic and the only thread found was http://rawze.com/forums/showthread.php?tid=587 where he talks about 4.5 blowby, which apparently is good.
Could someone explain what amount and why would be considered excessive in a Dyno test result ?
I just learned reading another thread that :
“If you have crank case pressure issues you have one or more of three things that can cause this. One too much blowby from piston rings. Two aircompressor is pushing pressure into crank case. Three the turbo seal is allowing boost pressure to cross into oil drain which goes into crank case. Rawze has video on how to check blowby with homemade manometer.
http://rawze.com/forums/showthread.php?tid=65”
I guess that complicates things, maybe to be excessive first have to find out what is causing it. Some input would be appreciated.
Thanks
RE: What is considered excessive blowby in a Dyno? - Rawze - 07-31-2018
Here is the tipping point that would cause me to start wanting to do something about it. I know the video is kinda red-neck .. the guy just wanted a comparison to another truck so that is what we did to get a sort-of rough idea between the 2 trucks. It is certianly no kind of official type of test in that video, just us playing around...
https://youtu.be/-Og4jCM6Rfg
BTW: that guy had just purchased his truck from loan mountain and had bad overhead cams, turbo issues, and a whole lot more problems he ended up spending thousands on out of his own pocket after weeks of arguing with them, getting nowhere.
This guy later ended up having to de-mandate vs. reman the engine. The extra blo-by it was not turbo related. Sure it still ran, but the thing kept the DPF wet with oil all the time and it would clog up every few thousand miles or so. After the de-mandate, and a few oil changes, it got slightly worse because all the carbon packing around the rings went away.
RE: What is considered excessive blowby in a Dyno? - in2trux - 07-31-2018
(07-31-2018 )Rawze Wrote: Here is the tipping point that would cause me to start wanting to do something about it. I know the video is kinda red-neck .. the guy just wanted a comparison to another truck so that is what we did to get a sort-of rough idea between the 2 trucks. It is certianly no kind of official type of test in that video, just us playing around...
https://youtu.be/-Og4jCM6Rfg
BTW: that guy had just purchased his truck from loan mountain and had bad overhead cams, turbo issues, and a whole lot more problems he ended up spending thousands on out of his own pocket after weeks of arguing with them, getting nowhere.
This guy later ended up having to de-mandate vs. reman the engine. The extra blo-by it was not turbo related. Sure it still ran, but the thing kept the DPF wet with oil all the time and it would clog up every few thousand miles or so. After the de-mandate, and a few oil changes, it got slightly worse because all the carbon packing around the rings went away.
God bless redneck engineering!
This is on of the simplest and most effective ways to evaluate engine health when considering purchase of a used truck. (quick)