kevink0000

I had an A-HA moment when thinking about Brett's racing buddy attributing engine failures on the racetrack to the use of a Sohn. There could be a correlation, maybe just not for the reasons stated.

Maybe both ideas are correct. The Sohn can oil starve, but most of the time doesn't. Especially on the street, since G loading like this is very seldom, but in racing it can be a couple of times a lap.

Maybe this has been covered somewhere before, if so, I haven't seen it.

Brett's racer friend had said the stock system provided positive pressure at the OMP feed hole, which we have found it does not.

BUT, the gravity feed on most Sohn installations may be subject to temporary interruption of flow, not due to gravity, but to negative G loading in the tube going to the Sohn under low speed (high G) acceleration, which, in 1st gear, can approach 1g.

Since there is a larger offset longitudinally than in height from the OMP to the Sohn tank, hard accel may cause the flow to the pump to slow or cease as normal gravity is overcome by G loading from acceleration. The pump has no ability to "suck" oil into itself. It has to be bathed internally in oil to pump that oil.

Also, changes in track slope can also affect the flow into the Sohn, when combined with lower gear acceleration. I don't believe there is enough of a difference for R/L turns to pose problems.

The stock system gets its oil from drainage from what appears to be an oil/air separator in the front cover. It is immediately above the OMP feed.

The way to "fix" this is to possibly mount the tank so there is no "slope" in the line to the pump, and the mass of oil in the tube is always subject only to normal gravity, not potential interference from G loading for the car's motion.

This is kind of an undeveloped idea so far, so its definitely subject to change!

What do you guys think of this?

Brettus

iTrader: (2)

That guy wasn't someone I knew personally , but was well known in the racing scene.
You may have a point .... although we don't know how the reservoir was set up in that car that had all the engine failures . Plus , that is the only instance I've heard of so the info isn't exactly compelling.

kevink0000

Oh I see. I thought there were multiple track failures and he pointed out every car that failed had a Sohn. I misremembered the account I guess.

Brettus

iTrader: (2)

Quoted from my post ...sounds like just one car .

TeamRX8

iTrader: (25)

https://www.seeingeye.org


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SiNfidelity

AGREE 100%. BASED on what we already know about the omp flow chart, the SOHN mod could really only be blamed if there were starvation issues due to race conditions.
solution = small surge reservoir in between the main reservoir and omp.

I have a question, is there room
and an ideal location for an inlet to be tapped into the factory omp for a fitting ?

I love the SOHN concept as I used one with my Lpg /propane 20b t rx8. Worked a treat. I was surprised/shocked at how much 2 stroke the omp actually flowed. Got a bit expensive actually 😛🤣

obviously I’d have to block the engine oil flow to pump also for the omp Mod.

thoughts?? Can it be done? Is there room ?

SiNfidelity

the silence is deafening here lol
I guess I’ll strip it down And have a look 😓

TeamRX8

iTrader: (25)

the answer is just pre-mix 1/2 oz/gal and don’t waste your money on an unnecessary extra add-on that really has no advantage long term.

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SiNfidelity

sorry bro. I don’t trust the slap happy premix concept. Chuck it in and hope for the best.
oil separation etc.

SiNfidelity

which channel is for oil into OMP. ? Anyone know ? 1 or 2 ?



now that I’m looking at it, maybe the front cover oil channel is gonna be the best option. Omp not a lot of room there.

need a front cover disassembled grrr

Red line envy

2stroke is designed to mix and burn with gas. Tbh I have a hard time trusting the Sohn.

SleepeR1st

iTrader: (2)

I agree, the renesis also had reduced omp output likely due to meeting emissions standards. How would the sohn overcome this? With the sohn you're pretty much forced to modify the omp output to get to the same level of safety premixing offers.

I recently talked about pressure differential with the sohn compared to the engine oil sump, and I believe others in the past have done a deep dive of how the omp truly operates with the physics of fluid dynamics in mind.

Red line envy

Ya engine oil must be pushed to the Omp. So how can gravity fed oil supply possibly give enough to the Omp. Add In the g force factors of driving and I don't trust it.

SleepeR1st

iTrader: (2)

My question was always, what exactly does the fuel atomization and combustion look like inside a renesis engine?
I tried finding a see through renesis engine example on youtube to no avail, but I did find a couple videos of test bench rotary engines with a see through style side plate so we can watch in slow motion.

The first link is about as basic as a rotary engine can get. It looks like he is likely to be premixing this gas a little, and the AFR is unknown, but looking at the likely very rich mixture, it is pretty evident how much that air fuel mixture covers essentially all of the apex seal. Given the side seal side seal and exhaust port design of the renesis, I would think premixing the fuel would allow it to have better coverage in that area as well. Some food for thought, not very scientific, but I was always curious what this truly looked liked.

The second link looks like an updated version of the rotary engine, too bad this design never made it to Mazda. The company currently has some projects with DARPA for I am assuming aircraft engines, and recently did a generator project for something in the military. @TeamRX8 You get your hands on one of these yet?

SiNfidelity

depends on how good I set up the reservoir and line I guess. It worked fine in my 20b. Worked too good actually. Was using shittonnes of 2stroke. The the official measurement.

kevink0000

I would just buy the Sohn. Its a lot of work to adapt a different source and as you know its rather important to have it working properly. Its something I wouldn't mess with and I mess with a lot of other things. Its just good to know you have one less garage mod you have to double check all the time. Which, in my garage is a good thing.

kevink0000

It works more than fine. Some don't like it, and can't give a good reason why.
Engine oil is not pushed to the OMP, it is a gravity drain from one of the small bearings, in the front cover, I can't remember which one.

kevink0000

2 stroke oil is injected all the time in 2 stroke engines, it still burns.

kevink0000

1/2 oz gallon is not enough even for super-awesome oil. Ok for low throttle, not OK for anything close to full throttle.

TeamRX8

iTrader: (25)

apology if it wasn’t clear; assuming gasoline fuel with the MOP still in place and functioning properly it is. Again, don’t waste your money on an unnecessary Sohn kit.

If you don’t have a MOP then premixing 1 oz/gal is the NA racing standard.
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Loki

iTrader: (1)

Have you looked at a Sohn setup closely? There is no slosh volume, it's filled with oil all the way up to whatever reservoir you set up. g forces make no difference, unless the car is upside down. Nothing in the injection setup requires oil pressure, it only requires oil to be available at the OMP entry, which the Sohn provides.

While I'm not trying to sell anyone Sohn adapters, the arguments against it are strange or not different from the stock setup. But at least with the Sohn I can choose different oils for injection and for engine lubrication/cooling.

Premixing solves different a different problem from the Sohn: getting oil into places where the stock injection system can't - side seals. Premixing and running a Sohn are not mutually exclusive.

SiNfidelity

AGREED100%

the oil line itself from the reservoir is not gonna empty under g”s the arguments against it are quite baffling to me.
I guess if one was set up extremely poorly, then u Cld be in trouble. But u wld have to be a complete moron to mess it up

SiNfidelity

The adaptor is a luxury item for me at the mo. Over 250aud delivered. I think I can do the same job for $20 without the adaptor.

I think the blue circle Cld be the sweet spot. Not a lot of room between manifold and Omp. But maybe enough. And thread a grommet to block off the oil out from front cover

kevink0000

I don't want to get into a premix/ OMP debate, there are other places for that.

That is indeed what the racing standard is in most places I have seen. I still have questions about that.

I also know from my previous experience that any 2 stroke piston engine would seize when run at high or full power with that ratio, 128:1. The bearings might tolerate that ratio for a period of time, but the piston and cylinder wall would become good friends, even with modern cylinder and piston coatings superior to what Mazda uses and has used in the past in their rotaries

Since we are talking about the OMP here, it should be noted that the stock OMP at the stock settings delivers 3x-4x that ratio at full throttle. And, it can be modified to deliver more than that.

kevink0000

The line will not empty, but it could stop flowing under very hard (1st gear) acceleration because the head height is less than the longitudinal distance from the tank to the OMP. In other words, there is a slope, and more oil mass in the longitudinal direction of the line than the vertical. If there is hard acceleration up a steep grade that could also cause a temporary pause. The OMP has no intake "suck" to speak of. It has to be primed at all times. But, It may or may not amount to anything in the real world.

I have the opposite view of the OMP vs premix. I believe the OMP does a better job on the side seals/irons than the apex seals or aluminum housings. Based on one of my engines that had a verified history, the OMP did a great job in 185000 miles of keeping the side seals and irons lubricated. The apex seals and chrome were severely worn. I reused the front iron in another build that is running currently. If that engine was premixed also, it may have gone well over 200k miles.