92 FD

running the proper 2 stroke oil should help because products like Amsoil's Interceptor contain detergents intended to control deposits in powervalves associated with two stroke motorcross bikes, waverunners, etc (which also tend to run rich, though not to the same extent as the FD) and moreover are designed to burn

no matter you do, you'll still get that wonderful "smoot" on the rear bumper, ha

these cars are such a pain in the *** in so many ways....if they weren't so much fun to drive I'd probably take the entire vehicle to the crusher

JConn2299

That's a highly important piece of information. Thanks for supplying it. I'm going to keep that one in mind.

moehler

iTrader: (12)

The Pettit ECU is know for dumping lots of fuel - that's really the only way to make a stand-alone ECU 'tuned' for any boost level. I would think that this is your problem - not the OMP.

92 FD

sure, I'll sign on with that

but, again, using a two stroke oil designed to control deposits http://www.amsoil.com/storefront/ait.aspx worked wonders on my (rich running) two stroke GPR12 waverunner and Cr250 motocrosser, I think it will help the FD as well (in addition to more "accurate" tuning, although still fat) with the PFC

jconn, let me know when you tear your engine down, it will still have a ton of carbon deposits

Kento

Just FYI: the "detergents" they speak of in the Amsoil product are to prevent gummy deposits from forming in the exhaust valve guides of so-equipped two-strokes. Those valves depend on oil deposited from the intake charge to keep them lubricated; the detergents keep oil by-products from building up between the valve and cylinder. Not to "clean out" any deposits in the combustion chamber or exhaust path.

All oil is "designed to burn"-- it's part of its chemical makeup. It's some of the additives that tend to not burn completely and leave deposits behind. However, fuel has a lot more additives that leave carbon deposits behind.

Using a good Group IV or V full synthetic motor oil should leave very little (if any) deposits from combustion (especially Group V ester-based oils-- in very simplistic terms, they are basically a very highly refined form of vegetable oil. A very basic analogy would be if you burned vegetable oil in a frying pan; it leaves very little deposits behind compared to animal fat).

It should also be noted that mixing oil with fuel changes its specific gravity, meaning that the flow rates are changed, which affects a/f ratios. It also affects the fuel's octane rating as well. However, since most engines using premix are hopefully tuned correctly, that is a moot point.

92 FD

good post, but I've also heard two stroke combustion chambers have less deposits when running the Amsoil product, and I noticed this with my GP1200R, compared to "bean" oils

also note that the pre-mix ratio is typically on the order of 100:1, so I wouldn't expect AFRs to be altered significantly at that ratio

for once I hope to see an FD rotary combustion chamber which is not caked in carbon after at least 10k miles

can serious deposits contribute to detonation and effect compression?

POS7

I thought carbon deposits were left on the rotors from incomplete combustion of gasoline. So, if you're running excessively rich (which the stock ecu tends to run), you should have extra carbon build up.


Also, the FD tends to have a high level of fuel dilution in the crank oil. So if you're not changing your oil every 2-3k, a significant part of your oil is not actually oil, and is actually gasoline based residue (which may be a prime reason for the carbon build up). This may go a long with what rotary resurrection is saying, and I don't have explicit proof....

92 FD

fuel dilution occurs in these cars within a very short period of time, especially if you are on the boost alot

the FD gives EPA nightmares

88IntegraLS

I didn't read through this whole thread but I've used cheap Wal mart premix for the past 2 years(*edit* the metering oil system is long gone) and have had to tear down the engine about 7 times due to side seal problems and porting mistakes. However, I've seen that premix in about one ounce per gallon seems to keep the really raspy carbon off the rotors. All I get for build up is a soft gummy thin layer of carbon on one half of the rotor faces.

The car is a large streetported FC NA with very advanced timing and about a 14:1 air fuel ratio.

88IntegraLS

Amazingly it does, one time I got lazy and assembled a motor with seals that were not free of old carbon and had some uneven compression and poor running. I tried carb cleaner in an vacuum line and that didn't do anything, so I tried 16oz of MMO on half a tank and bam, problem solved.

Sgtblue

iTrader: (16)

I wasn't aware that every car had fuel dilution problems. Judging from other threads I've read here, it seems to vary greatly from car to car. I'm still on a stock ECU, but only started having fuel dilution after my IAT went bad.