cgryphon, you will have to stop thinking so logically if you wish to participate in our follies... I mean discussions...

OK, I'll play
 

How about an anemometer? One of those little hand held ones sailors and kite flyers use to measure wind speed?

Or build your own
[http://www.energyquest.ca.gov/projects/anemometer.html]

Clay

That sounds good...
But first you need to deal with the fact that most of us 240 owners have no tach... so we are going to have a problem standardizing the rpms for this test....

Well.....
 

I do have a tach in my 240D. It's in the same guage culster as the fuel gauge and the temp. At idle it's usually less than 2 and while I'm driving it's always pegged! :D

But seriously; Can anything simple be done to improve (reduce) blow by? Otherwise I'm goin' quite worrying about it.

Clay

Because I didn't think about it very hard (obviously) - Brian, your suggestion sounds superior, as long as there is no significant variable restriction, which I doubt. Thanks! :)

In a nutshell: no

blowby
 

Someone posted basically asking what can be done and why is it worthwile knowing. For me I use it as one indicator of remaining engine life span. But also realise that is just guesswork without testing. If you have a too much blowby it is possible to reduce it greatly and the oil consumption as well simply by using a straight 40 oil in the late spring, summer and early fall. A 15-40 Multigrade does not seem to offer the sealing effect nearly as well. Hope the oil pump chain can endure this but at that point you have very little to loose as engine is pretty well shot anyways unless you intend to rebuild it. Suspect also a blowby point at which the engine designer suggests reconditioning the engine as well. You always seem to know when checking an old air filter as if too much is getting by the filter usually is pretty oily.I still like to see it pretty dry in there. In fact if pretty wet will pass that engine by. My attitude may be a misteak as some people drive excessively hard and that may produce somewhat more blowby than an engine in as good of shape driven moderatly. Many other reasons to have a general knowledge as well i imagine. Fortunatly my engines are well within the apparent normal range at present time. :sun_smile

Barry makes a good point here. When members post here with questions about a potential purchase, I always advise checking for blowby. Unfortunately, I don't have a very specific way of quantifying that, so that my advice isn't very useful. But if I could say something like "hold an X gallon plastic bag tightly over the breather nipple for Y seconds at idle. If it's full, don't buy it" then that would advance "the cause" somewhat.

You should stop driving when......
1) Blowby empties your crankcase before you can get to the store to buy another case of 50w.
2) Blowby leaves your windshield blackened everytime you step on it.
3) Blowby leaves more oil in you driveway than you remember pouring into the car the day before.
4) Blowby makes a choo choo out of your car when the oil filler cap blows off with the pressure build up.
5) Blowby leaves the air filter so incapable of passing air that you leave it out in disgust.
6) Blowby leaves so much oil under the hood that you need a shower after just checking the dipstick.
7) Blowby leaves a smoke trail that tells your wife where you are headed to.
8) Blowby costs so much to keep the car in oil, that you shop every oil sale for any kind of oil you can find.
9) Blowby creates enough pressure to warp the valve cover and blow out the front and rear seals on the engine.
10) Blowby gets so smoky you set off the fire alarms on most homes when you drive by.

If you already own the car blow by is pointless. As long as it starts when it is cold out and runs well it doesn't really matter. Besides all you can do to fix it is rebuild the engine.

Now if you are buying a car poping the oil cap is a good fast way to see if you even want to bother with a PPI. If it looks like a steam engine I will walk and save myself the expense of having a leak down test done.

being aware of the blowby can help you decide how many miles you might get from the engine. Judging from what I know now, my car had minor to moderate blowby at 220K when I bought it. 50K later, the blowby had certainly increased and had started to affect starting a little. At 290K, starting was a problem in winter without a heater, and at 300K, with a lot of blowby, I rebuilt. It really depends on how the car is used.

OK, I finally went and made up a "blowby test" this weekend. I'm sure it can be improved upon, but in the honest interest of science, I really tried to keep it pretty simple.Here it is: 1. Pull the breather tube on top of the valve cover. 2. Push a 6' length of 5/8" (16mm) heater hose on. 3. Tape a 30 gallon, heavy duty garbage bag tightly to the other end and 4. Start the car.

Here's how the bag inflated over the next 5 minutes:

after 5 minutes, I was pretty sure the bag would pop, but it just kept getting bigger and bigger, sort of like me when exposed to beer and cookies.

Look at the last 2 pictures again. The first one was after about 9.5 minutes of idling and 30 seconds of goosing the throttle, actually trying to get the thing to pop. So after 10 minutes of idling, I shut her down. The last one, which looks very similar, is 20 minutes later! I thought the thing would leak down almost immediately, but it didn't. Hopefully, all this silliness will provide a useful baseline for quickly analysing or at least roughly quantifying blowby. My engine has about 5K on it since I completely rebuilt it, so it's just about broken back in.