Houstonderk

iTrader: (3)

So I totally forgot about the not getting premix will fuel is cut for some reason. I have a half-bridged tii motor with n/a rotors for alittle while and always found it easier to drive city wise with the fuel cut on real low like 1700 rpms and just let it coast without fuel instead of it bucking with the amount of gas it uses. It might just be the tune though. Has there been any kind of proof of oil starvation this way or since its not combusting, does the oil stay coated ok?

SpeedOfLife

iTrader: (16)

I would never want to stop supplying the chambers with oil while it's turning faster than startup speeds or when warm.

forced inducted fd dude

well if you decel it'll be fine the injectors are still on spray, now unless you have a fcd then your going to start having compression prob after a while on the rear housing i believe

Houstonderk

iTrader: (3)

I'm running a haltech e6k. But the fuel cut decel feature is on real low so it doesn't buck so much, but then I realized that premix doesn't get sprayed since there is 0 duty cycle though. I've seen a bunch of threads but they basically have no answer, just a bunch of people arguing and then it gets closed. Some say since no combustion happens its okay, while others say the oil gets scraped off easily. This is basically the only thing I found on the topic and seems pretty good.

SyonykYou'll be fine. Premix does leave a protective film behind, and the engine under fuel cut deceleration is experiencing basically no significant loads - there's no combustion forcing the apex seals out, so it's spring & centripital forces.

The whole point of premix is to leave a lubricating film behind - that's how it works. I have a S4 NA, 20k miles on a rebuilt engine with fuel cut intact & running premix the entire life of the engine. I engine brake quite a bit, and I've never worried about it at all.

Don't worry about it. The early rotary engines didn't have anything for seal lubrication, and they were able to run fine.

-=Russ=-

classicauto

iTrader: (3)

First, having the fuel cut really low should be making cruising speeds difficult since it will cut fuel during any decrease in RPM that is ABOVE the inputted number. With 1700 in that field, when you are driving at any RPM above 1700 and the haltech sees a decrease in RPM - it cuts fuel.

Your description and experience are bass-ackwards.

As far as the question goes, I can't see it hurting that much. I ran my car like that with no troubles. There's many ways to think about it but really, whats going to happen when there's no (or very minimal) lube at the seal/housing surface? Wear, yes?

How many engines get rebuilt because the seal simply wore out? Not many. There's usually 1700 other causes by the time it reaches that point. Sure, the majority may be "wear" in essence since that what causes low compression but I dunno - thats my story and I'm stickin' to it

For me, the 2 fold increase in fuel mileage means I can afford to rebuild that much sooner

RotaMan99

It doesn't matter what RPM you are at, you can be at 8000 rpm and fuel cut will still happen on very light load or no load. First its the front rotor and then its both rotors.

The fuel gets turned back on at around 1100-1200 rpm which is where it may get a little jumpy.

Wrong, on decel, the fuel injectors shut off, there is NO FUEL on decel meaning NO 2 STROKE. There is very little oil left over once the injectors shut off which will get forced out the exhaust port during decompression.

Combustion doesn't force the apex seals out, that is spring and centripetal force like you said. The combustion forces the apex seals to the sides which seals off the combusted chamber from the other 2 chambers. You still need lubrication, just not as much. The "film" you are talking about can only last for so long, how long is beyond me but im sure most gets forced out of the exhaust port during decompression. The "film" during combustion will easily get burnt away since most 2 stroke oils have a flash point of about 200*F, and the combustion is higher then that. Im going to go out on a lim and say that the combustion at idle is somewhere around 300*F? According to my water temp gauge with the fan off , it stops around 250, no I did not do this on purpose.

Please, don't ever EVER tell someone not to worry about lubrication of the APEX seals. Why do you think mazda installed the lubrication system instead of running the seals dry? Mazda designed the OMP system to injector oil even on decel. Now I havn't seen high millage 2 stroke engines around, most are older high millage engines with premizing only running for about 30,000 miles or so.

RotaMan99

I guess I missed this

I was talking about the stock ECU.

Aaron Cake

iTrader: (1)

No proof except my wild speculation.

Based on the fact that no one has had an engine failure related to oil starvation on decel I doubt it's a big issue. I just brought it up as a point in the last thread because those who always support premix like to nitpick every minor point as well.

For the record I think for lubrication premix does a fine job. Obviously it works. Does it work better then the stock system? In my opinion no because in order for something to work better it must be superior in all aspects. It's a royal pain to premix, while the stock system requires virtually no attention.

Everything in the post above is wrong.

EFI systems cut all fuel during decel when the TPS is at zero. Otherwise you firehose unburned fuel from the exhaust, cause the engine to buck and contaminate the oil. All aftermarket EFI systems have the option to enable or disable decel cut but I can't think of any possible reason you would want to disable it. Maybe in a high overlap port in a racing situation to smooth out the throttle transition.

An FCD is simply a voltage clamp and prevents the ECU from seeing the real boost the pressure sensor is measuring past a certain point (8 PSI or so). This eliminates the ECU's fuel cut.