Seeking AFM Info

jimlem · July 27, 2013

Now I wanted to do this part separately. What you use for a catch can is important. Do NOT just use any catch can that you find in a listing on ebay or similar. A simple catch can that works pretty good and is not expensive is this one.....

http://www.jegs.com/i/JEGS/555/52205/10002/-1

Simple, cheap and somewhat effective. I have this one on now and have captured almost a shot glass worth of oil with it in right around 1000 miles since installing.

Now that I have solid proof that this is a necessity (at least for me), I am moving up to one of these cans.......

http://www.revxtreme.com/rx-catch-can-single-check-valve (the one I am eyeing the most)

Or

http://www.customcorvetteaccessories.com/oilcatchcan.html

DO NOT try to figure out what they are doing with these cans via their install files. These are performance Corvette and such shops and those engines PCV hookups an routings are different than ours. Follow what I described above.

I wonder if the oil use on these engines is really related to piston ring and other issues or if it's simply just a product of the PCV circuit? If you take your 1.5 to 2 ounces of oil at 1000 miles and extend it over the length of a normal oil change and you have a significant amount of oil right there. Still curious how or why the AFM gets the blame for the oil usage. Is it really the AFM causing it or is it just a product of the 5.3L's PCV system?

Cowpie · July 27, 2013

The way I would look at this, is that they might go hand in hand and magnify each other. The PCV oil, not separated out, then coats the intake and valves. Crud builds up when it combines with that oil. Meanwhile more and more oil is coming in. Then this affects the AFM function, which in turn causes even more oil to be "consumed". I have no real evidence that this scenario is fact, but it is sure not outside of plausible. And since it is common knowledge in the performance community that oil getting into the combustion process causes lower octane performance and can cause the ECM to revert to lower octane settings and retard timing, that this oil getting in there over time is actually costing fuel mileage and performance problems in general.

This is pure anecdotal and can only be taken with a grain of salt. Before I did this mod, we had only filled up with regular gasoline. We pretty much are exlusively driving on two lane 60 mph type highways, gravel roads, etc. Very little 4 lane cruising kind of stuff. Our mpg's were hovering right around 17-18. Many, when they switch to running E85 all the time, lose 20-25% fuel mileage, with would equate to ball park 13 mpg for me. Well due to pricing and availability, we have been exclusively on E85 since I did the PCV mod. Our mpgs are averaging slightly under 15 mpg with the E85 or ballpark 15% reduction. Would seem that maybe the PCV mod and getting the oil out of there has improved mpg and performance somewhat already. When prices change, as they always do, and the spread between E85 and gas is not as good, will run some gas thru it and compare also.

jimlem · July 29, 2013

I just read about TSB #10-06-01-008G. It is instructions to dealers on how to repair oil consumption issues on 2007 - 2009 AFM engines. It says to install oil deflector "umbrellas" somewhere in the oil pan I think as well as a new left side valve cover (on 2009s). Does anyone know if this means that they fixed those two issues on the 2010 to 2013 engines? Anyway to know if your engine came from the factory with the updated parts and design? Has anyone with a 2010 to 2013 model had a dealer install a new valve cover to fix oil consumption? Just curious. This whole AFM / oil loss thing has me bugged.

jmhornz71 · July 29, 2013

I have 2008 Suburban with 136k miles I just purchased. Its not using oil so far but would doing this help my engine too. Also is it possible to get some pictures on how you did the modification I learn easier with pics

mitchntx · July 30, 2013

I had a 98 Trans AM with the 5.7L ... An early version of today's AFM motors.

Under extreme, high RPM use on a road racing circuit, motors would oil starve on long sweeping left handers.

Oil would ride up the right side of the crankcase where the windage tray was notched for the low oil level sensor.

The initial fix was to overfill to 7 quarts of oil. In an F-body pan there was plenty of room for the added capacity. The fall out was the added volume generate more oil vapor than the vent system could handle. Vapor would liquify and pool in the system and in turn block ventilation altogether. Oil usage became a real problem. Lots of blow-by.

Once the Z06 Vettes came out, we converted to the Z06 PCV system which was much simpler and had a much larger separator built into the valley cover. The old LS1 blocks had to have an alignment boss beneath the cover milled away, but once completed, oil consumption dropped significantly.

Some racers used an external catch can. Problem was it had to be emptied regularly

If it went solid, oil would begin blowing out the can from the crankcase pressure vented to the reservoir.

Helluva mess.

Just some OE ....

Also early versions had "piston slap" on cold start-up. It was due to hyperuetectic pistons in a steel sleeve. The piston needed room to grow as it heated up.

Is it feasible that cylinders not normally supporting combustion run significantly cooler than normally operating cylinders and therefore ring gaps are not as tight?