First impressions matter right?
For my first question related topic as an inexperienced forum user I'm curious concerning the function of the "sub zero starting fluid" functionality in my 1983 RX7 GS.
Coolant doesn't combust, isn't lubricative (better compression under sub zero conditions according to other posts) and is even denounced by the manufacturer as functional apparently.

I do use it in sub zero conditions infrequently but it would be cool to make use of it as a constant system to replace mixing my fuel tank.

Could I.. treat it like a sohns adapter? 2 cycle engine oil fits all the criteria for assisting my engine under cold start conditions, I just don't know whether or not the system would be suited to allowing the flow of this substance through the system.

Redneck ingenuity yall.

Reference
Feel free to slander my foolishness for pondering this subject.

 

Seems to me that it would allow way too much oil into the combustion chamber.

I'm sure other more technical gurus will be better at answering this definitively.

Mine went in the trash 2 days after buying the car😛

 

I'd just remove the cold start assist system. If I recall correctly there was a bulletin out to remove them as they were deemed unnecessary.

In regards to treating it like an OMP adapter, well, you'd need to use an actual adapter and an OMP. The hole in the carb for it will not suffice for proper metering, and I don't know how well that tank would hold up to oil either.

I would suggest just running an OMP adapter/modified OMP with a separate tank rather than trying to use the cold start system. Not sure if you were thinking the cold start thingy would be gravity fed or what, but I think you'll have much better luck (and reliability) with an OMP or modified OMP system. The cold start system also dumps out of two holes on the AP nozzle (different holes than the AP) which are massive and comparatively far away from air flow. Just like how shortened OMP tubes cause oil pooling in the carb, I'm sure the cold start nozzles would exaggerate this effect.

 

The sub zero assist doesn't do much until the temps are literally at zero F or below. The reason they used coolant was to flood the carb with coolant to help deice it when starting. This is why its removed for most areas because it really never gets cold enough to even trigger it in most of the lower 48.

 

My car didn't have the sub-zero fluid reservoir, but since it was designed to hold coolant like the coolant overflow tank, I'd imagine it's the same material. Two-stroke oil will almost certainly eat the plastic and leak eventually.

 

the tank it’s self is ok with oil. The rubber on the bottom I’m not sure yet if it will swell with oil. The cold start system has a 12v pump and a one way check valve on top. You would need to address many mods to get the tank to take oil and gravity feed to the OMP.



Milk jug plastic good with most chemicals.

One way check valve

12v water pump

Oil seal that is probably 50/50 chance of being ok with oil.

 

I had wondered about converting this into a 2 stroke tank to feed the OMP as well, now I think I'll just make sure it's disconnected and eventually toss it when I get around to cleaning up the engine bay.

 

HDPE plastics and PET plastics (PET = soda bottles) are petroleum safe and many adventure-bikers use soda bottles to carry extra fuel. I have had a bottle of 87 oct and another of 2-stroke sitting on my work bench since Oct '18 to test them. They haven't softened at all in that time, and if they ever do then I'll know the useful lifespan.

I don't know what type of plastic the Cold-Start tank or Coolant Overflow tank are made from, but many older small-engine gas tanks look identical (lawnmower and minibikes from the '70's & 80's).

I finally got a Sohns Adapter and am contemplating what to use for a tank. I want it to have a nipple built into the bottom and a vented lid, so I'll probably look at lawnmower and weed-eater gas tanks.

If anyone knows what type of plastic the Cold Start (or Coolant Overflow) tank is, please tell.

 

I’m planning on looking for an oil tank out of a small 2 stroke scooter or dirt bike that came with oil injection. Some of the scooters even had level sensors so you can wire up a low oil warning light in the dash pretty easily.

Are Sohns adapters for 12As still available? I looked on Rotary Aviations site but only saw 13B listed. Or are they the same?

 

I have been using a washer fluid bottle as a oil tank for many years without any problems at all, I just removed the pump, made a block off plate with a gasket and it gravity feeds my omp pump and Sohn adapter.

I am not sure, but I dont think the adapters are available anymore, however there is a thread, if memory serves, that explains how to modify the omp to accept oil from a tank rather than the oil system.

Its not complicated.

I believe its better than premixing. The lubrication needs of the engine rise with rpm, and with premixing you get the same ratio of oil wether you are idling or at wot. That way you are getting way too much oil at low RPMs.

2 cents

edit:
I just went on the Rotary Aviation website and although the description states 13B, two of the pics in the posting is of a 12A adapter that looks the same as the one I bought years ago. I would give them a call.

 

like I said it’s same plastic as a milk jug.

The cap to the sub zero tank is vented already so that part is ok already.
I made a custom plastic part that is like a inspection window to replace the one way check valve.

 

Stripped down one way valve

Modified

Silicone

1st attempt

1st attempt not too bad

 

RA no longer makes them for the 12A or early 13B ('84-88). Member kutukutu1 is working on a 12A model though, based on the RA design.

 

I believe there are still some 12A adapters for sale out there, although I haven't looked in a while. Also @dwallsknox the later 13B (84+) pumps will not fit the 12A front cover without modification. I modified my front cover to fit an S4 pump, but I wouldn't suggested it unless you have a good reason to bother with it.

The adapter itself is dead simple, it's the manufacturing that is the catch since it's a spacer and a driveshaft extension. If I had the machining capabilities (I don't) I'd happily make one, so I look forward to seeing what kutukutu1 comes up with. It's also reasonably easy to modify a stock OMP to pull from an external tank - that's what I did on my S4 omp to 12A front cover hodgepodge. There are a couple of threads on the forum on the process if you're so curious.

 

Last one time be produced


I’m happy with my work.

Looks like it’s supposed to be there somehow

I’m not going to even try without a funnel

Same as the quart size but much cheaper.

I’ll do something with the window so you see red or glowing green if oil level is low.

Blue oil in line :-)

Just need to modify the cap with an air filter and string to keep the cap from dropping when filling.

 

Figured a cotton ball in the OEM cap will be a good air filter.

Not too lose not to packed.

Safety first

Nice almost like it was always this way

This window will look better in a day or so.

 

Almost done!