furansu

This is what I use in the SOHN tank and as a premix. The Idematsu premix oil is a better deal, when bought in bulk, but the Lucas stuff is very convenient in my area.

The RX-8 does use DFCO (Decel Fuel Cut-Off) in some circumstances, which is a toggle in the ECU, not a cell in the fuel tables of the ECU. This shuts down the injectors on no-load/decel when the engine is at full operating temperature and is in a throttle-off decel state, above 1,500RPM.

Steve Dallas

This is obviously directed at me, but I'm not sure what your point is, other than to just be a contrarian.

I did get "good results" until my engine failed compression at 45K miles--or at least what I perceived as good results. This is akin to trying to prove a negative. I saw no signs of failure, until I saw signs of failure. That is not evidence that Lucas oil is of poor quality any more than it proves Lucas oil is of good quality, or that premix is worth it or not worth it. Did premix prolong the life of my engine? It is impossible to know.

My thinking on all this has changed quite a bit. I did ALL of the recommended things to preserve my engine (dozens of track hours notwithstanding), and it still failed in more than one mode. IMHO, these engines and/or their implementations suffer from flawed engineering, and any given engine will be a victim of its particular assembly. My engine was always going to fail, and there was nothing I could do (or amount of $$ I could spend) to prevent that, although the track hours do present a significant wild card. Still, that engine served my purposes for 7+ years, and I had a lot of fun with the car.

Brettus

iTrader: (2)

Log of the exact scenario you just mentioned . Note there is still fuel being injected . I've never seen zero on the FPW log in any circumstances.

sinkas

BTW did you ever get the hear what your old engine was like internally,
or was it just sent back to mazda reman facility?

Loki

iTrader: (1)

I find this surprising. There is no reason to continue injecting fuel. Possible that the commanded pulse width is X but no actual signals are being sent? A bit like commanded AFR?

Brettus

iTrader: (2)

I'm thinking that if there was no fuel injected .... pressing on the throttle would lead to a very jerky engine .... Could be wrong but seems logical.

Steve Dallas

It was a dealer replacement under warranty, so it just went back to the somewhere within the mother ship. I do know it had a coolant seal failure, had [probably too much] metal in the oil, and barely failed compression on at least one face of both rotors.

I have tuned a handful of cars using 3 different ECUs, and I have never seen a data log with zero fuel supply, even with decel cut-off activated. They are normally limited to a max AFR of somewhere between 16 and 22. Obviously, I have nowhere near the experience of Brettus and furansu.

wannawankel

That also wouldn't make any sense to have a point that has no fuel being supplied - the air pump (engine) requires fuel in all cases to balance the forces at work. I take that back -- the Saab Sonnett 2-stroke cut fuel off in certain decel situations; however it had oil injection to the combustion chamber.

Loki

iTrader: (1)

Well the commanded AFR has no bearing on reality once you're in decel, and the actual AFR reading is limited by the sensor range. The cars I've tuned all pegged at 0.1V on the O2 sensor and 20 AFR reported. I take that as the ECU assuming that all O2 sensor voltages below 0.1V are 20 AFR.

I never really thought to look at what it does on decel in detail... and it sort of doesn't matter, that's not the fun part of the engine regime, but the observation is curious. I've also not tuned RX8s.

The pulse width is tiny, I'm not sure it would do anything for tip-in response. But this is all to say I'm surprised, not that I disagree.

TeamRX8

iTrader: (25)

It doesn’t matter who it is and has no personal intention behind it; the truth is what it is and was my only point.

furansu

Seems I was mistaken on just how aggressive DFCO can be and made poor assumptions about it. I datalogged an LS1 this morning for DFCO since I was already in it for other reasons and found that on decel (with DFCO disabled) the injector duty cycle was around 3.0% to 4.0%, but in DFCO it dropped to as low as 0.2%. A tiny amount of fuel for sure, but still a measurable amount.

Thank you for the correction.

Scarlet Speedster

Wait wait so y’all use Lucas oil in both the premix gas and the sohn tank? I’m super lost, I’m also reading it does nothing for you but then it does? Im very lost. On decel am I or am I not receiving enough oil to lubricate the engine? And if I install the sohn what’s the point in having premix still if I just use it as a daily? Sorry if this has been answered, I’m a new 8 owner.

furansu

it is the Internet, of course the answer is always in flux.

I am a fan of a well-maintained factory oil injection system, using a SOHN kit to assure I can monitor oil consumption and use a 2stroke specific oil. My oil consumption from the SOHN reservoir is fairly consistent, increasing during track use since RPM’s are higher for longer. If you maintain and service the oil injections system like it is a wear item (test, clean and replace as-needed ever 50k miles), you’ll be alright.

Pre-mix is fine too, and sometimes it may make sense to do both (track day bro) The amount of oil needed is small, it just needs to be sufficient and consistent, which the factory setup tries to do.

Factor in that too much oil is bad as it lowers knock resistance (octane rating). I will say saw now appreciable difference in performance or general temperatures between just the SOHN and SOHN+premix on short tracks in 100*f weather. I don’t have a way to measure seal surface temp to see if pre-mix served a benefit.

TeamRX8

iTrader: (25)

if it makes you feel any better; they’re all lost too.
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furansu

This.

BigCajun

iTrader: (1)

I'm bumping this for recent interest and discussion.
I've been here for about 10 years, I have a new Sohn bundle that I had planned on putting on my 8 in the event of a rebuild.

It only recently occurred to me to check with the person standing behind the warranty of my recently purchased engine, which I've yet to do.
If it will void the warranty, then my interest in it will be gone, and I'll have a kit to sell.

I've seen plenty of points made for the presumed virtues of the Sohn adapter, injecting clean 2 stroke oil designed to burn cleanly and lubricate as opposed to used, possibly contaminated, or 'dirty' conventional motor oil.

I also don't remember seeing any arguments against it other than 'It doesn't help', 'It's not proven', or just plain snarky insults.

References made to some individuals who needed rebuilds alluding to the use of it as a contributing factor are few, I don't know what the long term results have been for proponents who used, or still use them.

Membership attrition isn't helping accumulate much useful evidence either.

If anyone has any solid, logical arguments against using the Sohn adapter other than 'It's not proven' or 'No one can prove it helps', etc., I'd love to hear them, and other members still expressing interest in the kits might as well.

SleepeR1st

iTrader: (2)

I wonder if there truly is enough pressure differential (vacuum) from the sohn tank compared to the engines oil sump to work well under load. The sohn kit holds what, maybe 2 quarts? The stock stump and oil cooling system holds somewhere around 7 quarts. Being in the hvac world, it is known that pumps create a pressure differential on inlet/outlet of the impeller which is directly affected by the head of water/glycol proceeding, and I am guessing the omp "pump" works the same. While mazda's oil injection rates were pretty low from the factory, I do believe they have designed the system around total capacity in obtaining their figures, or maybe I really have no idea.

To me the 2 stroke oil makes sense, it burns cleaner, leaves less deposits and we all know this, but really how many n/a renesis engines fail because of carbon build in the apex channel or side seal channel? My grandmother driving and shifting at 4k rpm which leads to carbon deposits doesn't count as an example since that is user error in how the engine should be operated. I think a majority of the NA failures in racing are likely due to heat building up on the side seals. I have personally been in 6port FC RX7s with way more miles on their engines compared to the average rx8 engine, and I think this is due to the way the rx8's exhaust ports are designed and how it leads to side seal failure.

I've read a lot about the sohn and it is enticing, but im not convinced it would make a renesis engine last any longer than just running the omp with premix, and possibly doing the omp mod to increase output.

Again, I really have no idea, just adding to the conversation, and basing my assumptions on what past rx7 race cars have been doing. I'm in the camp of if the engine ever does go in mine and the availability and costs of rebuilds is seemingly getting difficult, I would just do the LFX swap and call it a day. I love the chassis and I love the renesis engine, but there is only so much we can do to alleviate its design flaw of the exhaust port design.

Cheers

BigCajun

iTrader: (1)

Thanks for the input.
That's some good info.

SleepeR1st

iTrader: (2)

I'm pretty much in the same boat as you BC, my engine has 22k miles so maybe halfway dead (I kid, I kid), and you purchased a crate engine, so ours are pretty close in health I would gather. We both want what's best for it, but I think what's best only goes so far you know? If I drive mine 5k miles a year, I can get potentially 20 years out of the engine, but I'm sure i'll be bored as hell after flying electric cars are blowing by me at 200mph at that point in the future.

BigCajun

iTrader: (1)

I don't know how a nearly silent vehicle can match the driving experience of our RX8s though, no matter how fast they go.
Driving should be fun.

I recently saw an article about a young woman who bought a 2014 (I think) EV and the battery died shortly after.
The battery was no longer available for it, so she ended up with a very expensive junk car.

BigCajun

iTrader: (1)

This;

https://ijr.com/electric-vehicle-nig...s-new-battery/

SleepeR1st

iTrader: (2)

EVs just don't smell the same as a properly premixed rotary now do they? Burnt hydrocarbons is half the fun

_JB_

I have a Sohn on my car and I noticed something the other day, I had the Sohn container about 1/4 full of Amsoil Interceptor oil (yellow in color). When I filled the Sohn with Amsoil Sabre Pro (blue) I could watch Sabre move down to the OMP; it took a few minutes to feed all the way. Sabre is thicker oil than Interceptor and I wonder if it is also a heavier oil, and/or if the added weight from a full Sohn container was pushing down into the OMP better. I just street drive my car but it made me wonder if running a Sohn container that low was causing issues properly feeding the OMP. After a few miles all the OMP lines turned blue with Sabre and I didn't see any air bubbles before or after this observation.

I wonder if the Ryan Rotary Performance kit (https://www.ryanrotaryperformance.co...ng-cof-adapter) is actually better than Sohn, since the RRP kit feeds into the top of the OMP vs the Sohn's side?

BigCajun

iTrader: (1)

That's interesting.
I only remember one member who had another company's kit but I don't remember who made it.

TeamRX8

iTrader: (25)

that’s probably because Amsoil Saber Professional is intended as a premix product rather than direct injection. You might want to consider asking Amsoil what their feeling is about using it that way.
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