Saturday, February 7, 2009

ATF Treatment By BOBRx-7

ATF Treatment By BOBRx-7

Restoring Compression � The ATF Treatment

One of the more common reasons for failure of rotary engines is actually very preventable and in many cases reversible. This entry will cover just how it�s done and why it works 95% of the time.

Rotor Seal Design

The rotary engine is among the simplest in overall design. No valves, cams, heads or any of the parts commonly associated with piston engines. This makes them extremely reliable with one major exception. . . the apex seals.

To seal the three tips of each rotor, a groove is machined to accept a long thin cast iron (in stock engines) insert. This is the apex seal. A spring, located behind the seal, applies the force needed to hold the seal in contact with the rotor housing wall as it passes around the inside housing wall. As the apex seals pass the narrow points in the housing, they are compressed against the springs and then move back outward in the wider parts of the housing. A corner seal at each end of the apex seal is also spring loaded to prevent combustion gasses from leaking around the ends of the rotor tip. Additional seals on the sides of the rotor complete the set to form a relatively leak-free chamber.

Over time, carbon, ash and oil sludge deposits will accumulate in the machined groove in the rotor tip. If allowed to remain, the apex seals will eventually begin to bind in the grooves and will not move outward completely during the combustion cycle or intake cycle. This allows gasses to escape into the next chamber, reducing compression. In the extreme, the apex seals will stick in the compressed position to the extent that virtually all compression is lost. At this point, the engine will likely refuse to run at all.

Dirty oil and general lack of maintenance is the most common cause of compression loss. The oil injection system on the rotary is designed to feed oil in to the chamber to keep both the housing walls and the apex and corner seals lubricated and clean. Dirty oil will simply throw grit, sludge and other combustion debris back into the chamber. Result, thousands of perfectly good 12A and 13B engines, or complete cars, rotting in the junk yard, for no good reason!!!!

Preventive Care

The obvious solution here is consistent oil changes. Never more than 3000 miles between changes and good (spelled Castrol GTX 20W50) oil with a new filter. By the way, the puny little factory filter is COMPLETELY inadequate. A remote filter setup that will allow the use of a 1 qt. filter is much better. At the very least, use a K&N or WIX filter in the stock location. These will filter particles down to 10 microns. A better oil cooler on those 83-85 12A engines is also an excellent idea.

The Fix

So what if your engine is already suffering from the dreaded sticking/seized apex seals, you ask?? Never fear. An old mechanics trick used to free up sticking valves and lifters works WONDERS on your rotary. The procedure works a little differently for carbureted engines that the EGI models, but accomplishes the same results.


Disable the ignition primary circuit by disconnecting the igniters or the negative lead on each ignition coil.


Remove the air cleaner lid on carbureted engines, or pull the Leading (lower) plugs on 13B EGI engines.


For carbureted engines, pour 2 oz. Automatic Transmission Fluid (ATF) (the cheap stuff is fine) down each primary bore (the small ones) of the carb, while an assistant cranks the engine for 5 seconds or so. On EGI engines, use an oil squirt can and pump two or three shots into leach leading spark plug hole. Have an assistant lightly bump the starter two or three times, squirt in more oil, bump the starter, squirt, bump, squirt, bump. . . you get the idea. You want to get ATF in all chambers and thoroughly distributed. Reinstall the spark plugs on EGI engines.


Allow the engine to sit in the ATF stew for AT LEAST 24 hours. Don�t be tempted to rush the process. This takes time. The detergents in the fluid, used to keep the small polished valves in an auto trans valve body free, will soften the carbon and sludge deposits.


PLEASE. . . Make sure the car is outside for this step. You'll see why. Reconnect the ignition system, hold the throttle open � way on carbureted engine and start it up. Allow to idle. The neighbors will now think that Mt. St. Helens has erupted in you driveway or a massive brush fire has broken out. It will take about 5 minutes for the smoke to clear completely, since some of the ATF has worked it�s way into the exhaust pipe and must be burned off.


Install a new set of plugs. The ATF will foul the old ones and may cause hi-speed misfire. Take the car out on the e-way and THRASH IT for a few miles to completely clear the chambers. 6 to 10 redline runs will do it.

At this point, the apex and corner seals can move freely again. In extreme cases, you may want to repeat the treatment after a week or so of driving. If so, hang on to the old plugs to use again for the second treatment.

If you were to perform a before and after compression test, you could potentially see an increase of 20 psi or more and will feel a whole lot of power that wasn�t there before. I have revived engines that would not start and know of a couple ITA drivers running junk yard engines brought back to life this way.

IT�S CHEAP. . . IT WORKS. . . And you can end up with a nearly new engine for $2. You�ve gotta love it!!



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