Full Catch Can --> A Lot of "Blow by"

KahneFan · Jan 16, 2019

So, I empty my catch can every 5K or so miles and it's usually full. I posted this on a FB page and people said that means I have a lot of "blow by". 1) I have no idea what that means. 2) I have no idea if it's a bad thing.

Anyone able to shed light on this?

muddy12 · Jan 16, 2019

Blow by is combustion gasses "blowing" past the piston rings, and getting into the crank case.
Not sure what what is considered to be a normal vs excessive amount of blow by for the 5.7?

I had a lot more that that from my last catch can dump, but I had been making a lot of short trips, and had a lot of condensation in the oil.

Nick@GotExhaust · Jan 16, 2019

How many oz cup is that?

MADDOG · Jan 16, 2019

I'd like to know as well. How many ounces is in that cup? Can you measure the oil with a measuring cup?

And...how many miles on your truck?

Blowby is normal for the HEMI. The amount which is normal is a subject of debate. I think it varies depending on mileage, how the owner drives the vehicle, ambient temperature, etc...

I get an amount similar to what's in that cup from the catch can on my SRT8 when I run it hard in hot weather in about 3K or so miles.

turkeybird56 · Jan 16, 2019

WHAT is skerry that all that stuff being dumped back into intake and plenum. One reason why I am gonna get a CC in late spring when $$$$ free up a lil

MADDOG · Jan 16, 2019

I know their hearts are in the right place but the EPA and state regulatory bodies just don't get it. Running that oily gas back into the intake does reburn some of the hydrocarbons but not all of it. Eventually that oil will create deposits inside the intake, on the valves, in the combustion chambers and then into the catalytic converters. Poor performance results, systems are damaged and since it can be an expensive fix, owners ignore it and the crud eventually finds its way to atmosphere. So what did we gain here, hmmmm???

OK...soap box put away...

Here's normal blowby in my SRT after 2K miles in colder weather and with me driving relatively sanely. (It's hard to keep my foot out of it...

)

1K miles, cold weather, no racin':

Hotter weather and running hard (0W-40 full synthetic) means I'll have a 1/2 to 3/4 full catch can. Next time I dump it I'll measure the volume of the lower portion of the can. I called BT but the guy who answered the call had no idea what their 5.7L Ram truck catch can fluid capacity is.

Oh, and here's the BT one I have on the car now:

mohemipar · Jan 16, 2019

MADDOG said:
I know their hearts are in the right place but the EPA and state regulatory bodies just don't get it. Running that oily gas back into the intake does reburn some of the hydrocarbons but not all of it. Eventually that oil will create deposits inside the intake, on the valves, in the combustion chambers and then into the catalytic converters. Poor performance results, systems are damaged and since it can be an expensive fix, owners ignore it and the crud eventually finds its way to atmosphere. So what did we gain here, hmmmm???

OK...soap box put away...

Here's normal blowby in my SRT after 2K miles in colder weather and with me driving relatively sanely. (It's hard to keep my foot out of it... )

1K miles, cold weather, no racin':

Hotter weather and running hard (0W-40 full synthetic) means I'll have a 1/2 to 3/4 full catch can. Next time I dump it I'll measure the volume of the lower portion of the can. I called BT but the guy who answered the call had no idea what their 5.7L Ram truck catch can fluid capacity is.

Oh, and here's the BT one I have on the car now:

Seems very similar to what I have experienced for levels in my 2018. Last summer after some abuse I saw the most collection. Lol.

MADDOG · Jan 16, 2019

Somebody once posted in a 300 forum, "How many horsepower does a catch can get you?"

The response, by a fellow named Jay who lives just North of me was; "You don't get any more horsepower. However, you do get the keep the horses you have."

MADDOG · Jan 16, 2019

News Flash!

BT Catch Cans hold 4.17 ounces per BT. That's from the lower portion of the threads inside the can to the bottom.

Tach_tech · Jan 16, 2019

I don’t think that’s excessive for 5k miles at all. That’s pretty good.

I get that much out of my truck in less than 1k km, more if I’m hard on it. Boost and wider ring gaps will definitely increase it though.

Nick@GotExhaust · Jan 16, 2019

These post are proof of how beneficial a catch can is. I run one on my Mustang and would run one on my 6.4 if I could. We got UPR and Mishimoto cans if anyone is interested. UPR has been a crazy hot seller!

16RamHemi · Jan 16, 2019

i plan to do this soon. these reports are proof of its importance. once one is installed how should one go about cleaning out whatever needs cleaning from that junk?

MADDOG · Jan 16, 2019

It's easy to clean. On mine I just remove the lower portion of the can, dispose of the contents (in an environmentally friendly manner) and reinstall the lower portion of the can.

Here is the catch can disassembled:

Once every 4 or 5 cycles I remove the upper screen, clean out the steel filter material placed in the upper section by givimg it a quick solvent rinse, wipe out the cap, swab out the two nozzles and put it all back together. I don't have to but I'm just OCD that way.

tap4154 · Jan 16, 2019

Interesting seeing all these threads on the catch cans, and it does seem like it could be a useful device. Unfortunately in California you can’t do anything to alter the emissions system. If you have one of those installed it won’t pass visual inspection during a smog check.

Wild one · Jan 16, 2019

Moroso builds a catch can that uses a drain valve,you can put a hose on and drain into a catch basin,instead of having to unscrew the bottom half of the can to dump.

MADDOG · Jan 16, 2019

tap4154 said:
Interesting seeing all these threads on the catch cans, and it does seem like it could be a useful device. Unfortunately in California you can’t do anything to alter the emissions system. If you have one of those installed it won’t pass visual inspection during a smog check.

Another example of regulatory misguided children and it demonstrates that odd behavior of regulating with reason.

Wild one said:
Moroso builds a catch can that uses a drain valve,you can put a hose on and drain into a catch basin,instead of having to unscrew the bottom half of the can to dump.

I've seen those. That drain valve is a handy feature but since my catch can is mounted level with the PCV system (base of intake manifold) and near the power center, I'd rather not run anymore hose than needed for draining through the bottom.

huntergreen · Jan 16, 2019

tap4154 said:
Interesting seeing all these threads on the catch cans, and it does seem like it could be a useful device. Unfortunately in California you can’t do anything to alter the emissions system. If you have one of those installed it won’t pass visual inspection during a smog check.

You could remove and replace be fore inspection.

Nick@GotExhaust · Jan 16, 2019

16RamHemi said:
i plan to do this soon. these reports are proof of its importance. once one is installed how should one go about cleaning out whatever needs cleaning from that junk?

Just dump the can into something and screw the can back on. very quick and simple. I like to pour it in a big gatorade bottle so i can see the look of the oil. Then empty it in a oil container and get rid of it anywhere that accepts waste oil like an auto zone, walmart, etc...

Nick@GotExhaust · Jan 16, 2019

huntergreen said:
You could remove and replace be fore inspection.

yes that is true. They can be installed and removed fairly easily and quickly.

Fitz-0518 · Jan 16, 2019

I have a UPR catch can on my 03 5.7 1500 in Ca. Some smog techs have no idea what is factory or aftermarket change. Mine does. Easy off and on every two years. One nut and bolt and two hoses.

Full Catch Can --> A Lot of "Blow by"

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