92 FD

just got done tearing my engine down....7k miles on a reman with re-used, but thoroughly cleaned, rotors

sure enough, combustion chambers are caked in carbon residue (again)....I saw the same thing on mahjik's thread and many others, as well as my previous rebuild

after talking to a few people, I'm convinced using the OMP to inject 4 stroke oil which is not designed to burn IS the culprit, and I intend to remove the OMP and pre-mix with Yamaha synthetic or Idemitsu rotary pre-mix oil from now on http://www.rotorsportsracing.com/per...g/idemitsu.htm

I'm sure there are other threads on this topic, but I wanted to find out what the current pre-mix guys are using and what results they are seeing after tear down

rynberg

Here are my rotors at 85k miles:




60k+ miles on the stock ecu, 20k+ miles on the PFC, normal OMP settings, running 10-14 psi on stock twins

I think it's a bit of a jump to blame excessive carbon build-up on the OMP metering 4-stroke oil into the combustion chamber. Sounds like you're just running too damn rich, driving like a grandma, or the rotors weren't fully cleaned when they went in the reman.

92 FD

um...all these cars run pig rich

I ran the stock ECU for about 3 years and the Pettit for about 4

I definitely do not drive like a grandma (!), and run Mobil 1 with 93 octane at all times

I think the 4 stroke oil is a major contributor to excessive carbon build up...using something like MMO on occasion likely helps

poss

iTrader: (5)

It's an engine, you're going to have at least a thin layer of carbon. Any pics of how bad your's is?

rynberg

You've provided no evidence as to why you think that way. How is 4-stroke oil from the OMP significantly carboning up rotors as compared to running really rich?

92 FD

after 7k miles?? WTF?

I need to post some pics

t-von

iTrader: (8)

Here:


http://www.rotaryaviation.com/oil_in...p_adaptors.htm


Use one of those an run a separate tank to hold 2 cycle oil. Also how new are your plug wires and plugs? Do your plugs have good burn color?

92 FD

pre-mix is a far more accurate and reliable way to meter oil (2 stroke syn) into the engine....I only drive my car on weekends anyhow, so the "inconvenience" is negligible

the OMP is going straight into the garbage can, and the flimsy plastic lines

t-von

iTrader: (8)

See that link I posted. Any experienced builder will tell you that injecting 2 cycle oil is preferred over crank case oil.

92 FD

Most stock engines use a metering pump pumping a small amount of engine oil from the oil pan into the intake manifold and/or directly into the combustion chamber. Engine oil is designed to lubricate sleeve bearings and carry heat from the engine interior to some cooling areas. In the RX7 the heat is removed from the oil in an oil cooler. When engine oil is getting into the combustion chamber, it only is burning partially, leaving some unburned deposits behind. These deposits can build up and reduce engine performance.

One obvious method of preventing this is to disconnect the metering pump altogether and mix two-stroke oil to the gasoline like some older two-stroke engines require. With this method it has been demonstrated that two-stroke oil is an effective lubricant and there is no build up of combustion residues.

bingo

rynberg

And I've got my 85k motor with ZERO oil-related damage whatsoever telling me that the OMP works just fine.....

Again, if someone has a technical explanation or link that proves that injecting 4-stroke oil into the combustion chamber carbons up rotors, I would love to read it.

rynberg

My motor was cleaner than average according to my mechanic (you can see all pics in my rebuild time thread), and I've even been running, gasp, synthetic oil....

Mind posting a source for that quote?

92 FD

see link above

hey, do whatever floats your boat

I was primarily looking for feedback from people who have pre-mixed for a significant period of time and torn the engine down....if there are any such people

t-von

iTrader: (8)

Ryn it's in the above statement.

"When engine oil is getting into the combustion chamber, it only is burning partially, leaving some unburned deposits behind. These deposits can build up and reduce engine performance."


The partially unburned oil left behind is going to allow carbon deposits to stick to it. No one is saying that the OMP doesn't do it's job, that's why rotarys have been proven to last over 200k. The facts are you wouldn't have as much build-up if 2 cycle oil was injected.

92 Fd get your rotors ceramic coated. Someone here did it and after 10k miles, he claimed to have absolutely no carbon build up on the rotor faces. He's also getting better mileage too.

rynberg

There's nothing in your post that indicates the source of that info....

And you're right, I've stated my opinion and will now leave your thread alone. You might also get more responses in the Haltech forum, since everyone in there has to run pre-mix only.

Unless you are an automotive engineer, I'll wait until I see someone post some scientific basis of proof....

I'm not busting ***** here, just trying to prevent the spread of misinformation....

92 FD

I can tell you this, I was running a cheap "bean oil" in my GP1200R waverunner for several years and the powervalves were caked in carbon deposits

started running Amsoil syn 2 stroke and it was like night and day....cleaned them right up....amazing...I know that is a different application, but use of a syn 2 stroke oil which is actually intended for the stated application should dramatically reduce deposits

RotaryResurrection

iTrader: (8)

As bad as I hate to do it, I've gotta side with rynberg on this one.

The OMP has proven itself to work properly on many 200-300K+ mile FC's and 100-150k mile FD's on the original engine. Driving habits and brand of gasoline have more to do with carbon buildup than the OMP, however it should be noted that those who do not maintain their oil change habits religiously can suffer from excess carbon buildup.

I take apart engines all the time, most of them original. I usually see less carbon on a bone stock 100k mile engine than I would a highly modded (i.e. rich mapped) engine that was put together 10-20k miles ago.

I just took apart an FC turbo engine that has a bit over 4k miles on it, and broke the rear plate at the dowel area. The engine had the carbon of a 150k mile engine. I attribute this to the overly rich tuned mixture.

Kento

Exactly.
Really? How do you know exactly how much fuel you have in the tank when you dump in the two-stroke oil? You do know that some two-stroke oil can settle in greater concentrations to the bottom of the tank after sitting for a while, right?

While I'm not saying that pre-mixing for the rotary is bunk, I am saying that blaming the OMP and metering regular motor oil into the combustion chamber for excessive carbon buildup is bunk. There are a lot bigger culprits to carbon buildup.

While the Rotary Aviation site has some good info, just because they state something like that to promote their OMP bypass (which appears to be a quality product) doesn't make it gospel.

92 FD

ok, Kevin, good post

but I'm still chucking my metering pump and pre-mixing 2 syn stroke

t-von

iTrader: (8)

Again no one is disproving that the OMP is not doing it's job. It does a great job of injecting oil. I'm just saying that it's better to burn an oil that is designed to be burned in the cumbustion process. Crankcase 4 cycle oil isn't really designed for this 2 cycle oil is. That's why any rotary performance builder will tell you 2 cycle oil is better however, 92Fd's situation could easily have an engine running too rich.

cptpain

iTrader: (1)

if you wan to get rid of carbon build-up do this:

1) wait until your gas tank runs as low on empty as possible, then drain the tank of any remainig fuel.

2) go to your local munincipal airport and purchase 5-gallons of fuel. most of the small plane airports carry 104 or 108 octane fuel. of course this will cost about a good $30-45 depending on your location

3) fill up the tank with all of the fuel

4) drive around the block a few times so that the car will adjust its A/F ratio.

5)once step 4 is done drive in stop and go traffic in any gear up to 5k. do this for 2-5 miles

6) then with the remaining fuel drop the hammer on the car all the way to just before fuel cut-off rpm in 3rd gear. basically have fun with the car with the fuel you have.

7) if you still have fuel left then the next day all you need to do is let the car warm-up and repeat step 6.

this method may not work for everyone but i have done it and to me it works. i actually saw in my rear-view that i was puffing out all that carbon buildup in small puffs of smoke and when revving at idle i saw that also some of the carbon was coming out in small pieces from the rest of the exhaust. mostly on back-fires. i did this to fix my problem of my GSL-SE not revving past 5-6k and now it goes up to a fuel-cut off of 8.5k.

Kento

Uh, sorry, but there's no way you can "see" the carbon "in small pieces" getting "puffed out the back in clouds of smoke". If they were big enough to see, they'd be big enough to cause damage to your apex seals and probably your exhaust turbines (with the FD, at least).

Also, filling up with avgas at the local airport will damage your 02 sensor and cats for those still running them.

92 FD

Marvel Mystery Oil reportedly works well

t-von

iTrader: (8)

Your not taking into account all the carbon build-up in the manifolds and exhaust. A good cleaning can break down carbon throughout the entire exhaust system (manifold back).

t-von

iTrader: (8)

I use the water steam cleaning method twice a year or every 6k. Regular cleanings will keep the build-up down.