To premix or not to premix, that is the question

[Magsrx8]

I've done lots of reading around the use of premix and wanted to ask the community on here what to do with quandary.

My 2006 231 S1 had only 10,589 miles on the clock when I picked her up. It's had two actual owners, one for a year and then it's long term owner who barely used it and had it garaged. Premix has not been used so far looking at all the paperwork I have and after speaking to the only garage who mot'd it from 2009 to 2017.

General consensus seems to be to use a premix but I'm not sure whether this is necessary on such a low mileage engine which has been well looked after. Is the use of premix a preventative measure or a maintenance measure?

If you had a S1 with only 11K on the clock now, would you introduce a premix into the equation going forward?

Look forward to your thoughts.

Thanks.

[rotatopotato]

Absolutely premix it if you want it to last, the S1 housings do not get enough oil coverage in the centre (fixed in the S2s with the inclusion of the centre oil injectors). Also consider a COFS/SOHN to feed it clean two stroke, at that mileage if its got good compression then premixing will will help it last a loooong time (even better with a COFS/SOHN as well).

Given its age and low mileage its probably on older revision coils so if they've not be replaced with Mazda rev C at some point I'd look at doing that for peace of mind (or fit RRP coils).

[Lucky 8 Racing]

You should absolutely be premixing with a good quality 2T oil

[rotatopotato]

It's never to early to start premixing, though it can be too late...

[PaulAV]

It's always a good idea to get a mini map that increases the oil injection rate, the downside to pre mixing is it can give a false sense of security, on deceleration no fuel is injected into the chambers so no pre mix is introduced, I'm not saying don't do it, I'm saying be aware it's not the miracle cure to engine wear. On the subject of sohn adapter this is definitely a good idea, but a few builders are starting to question 2 stroke oil as the best to use in the sohn adapter over clean engine oil due to film strength

[350matt]

another vote for pre-mix unless you're adding loads you don't really notice any downside

[Milos_Balunovic]

If you drive an S2 or a S1 rebuilt with s2 housings and using all injection ports than sohn + map to increase the amount injected.

If not premix as side injectors lack in mid of apex on s1 (was never a problem on previous engines where there was one in midle)

Regarding fuel cut. When there is fuel cut there is no fuel to wash off the oil and what is there stays there much better than without ful cut as fuel has burned and only oil remains** in higher concentration.
** using high flash point oils ofc....

I premix 0.5% plus have increased the map for OMP with sohn.

[Steve.82]

I want to premix, but the noise around carbon buildup issues is stopping me….

[Lucky 8 Racing]

another vote for pre-mix unless you're adding loads you don't really notice any downside

Define loads, I’m still doing 10ml per L

[HarSc]

another vote for pre-mix unless you're adding loads you don't really notice any downside

Define loads, I’m still doing 10ml per L

*pours over half a bottle of premix into tank when filling up*

"Wait, where's my money gone?"

jk ha! Your engine will love you forever! - I normally run about 150ml to a tank

[79398]

20ml per 10 litres
Too much will kill the cat, took advice from Aston at Essex Rotary,

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[rotatopotato]

Sounds about right, 120ml per tank. I aim for at least that per tank, but sometimes oversquirt and end up nearer 250ml for the tank. Engine doesn't seem to mind and no cat to bother (in the 192 at least, but that's coming for the R3 too).

[rotatopotato]

I want to premix, but the noise around carbon buildup issues is stopping me….

Carbon build-up is from driving too gently and/or idling the engine without going anywhere.

Premix with 2T can help soften and remove carbon, along with driving right.

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[DrewR3]

I dont premix the R3, used to run it in my PZ. Improved engine design and mines had an oil change every 1500 miles so is always injecting clean(ish) oil. I will be investing in an RRP COFS though

[rotatopotato]

If you mean the regular COFS adaptor then that only works on S1s as the S2s have a more sophisticated OMP setup. I've been talking to Carl about it and have a potential solution lined up using a pump and version of the RRP tanks that allow for the return feeds from the S2 OMP. Seems like it should be straightforward enough - I have the pump and pressure relief valve, just waiting on some fittings before I start a bench test and dial in the correct pressure before installing into the car.

[DrewR3]

If you mean the regular COFS adaptor then that only works on S1s as the S2s have a more sophisticated OMP setup. I've been talking to Carl about it and have a potential solution lined up using a pump and version of the RRP tanks that allow for the return feeds from the S2 OMP. Seems like it should be straightforward enough - I have the pump and pressure relief valve, just waiting on some fittings before I start a bench test and dial in the correct pressure before installing into the car.

Very intresting. I had not noticed it was S1 only. That puts a damper on the running it for the R3 unless a work around is found. Looks like the clean engine oil shall remain for a while. On that note Castrol Magnatec has a good discount at Halfrauds at the moment if anyone is interested, just got a couple of 4l for 26 quid i think each instead of 35.

[SprintRX8]

I’ll be prefixing mine when finished.
Using a decent 2T oil that burns well.
Not the usual stuff you’ll Chuck in your Mower or Chain saw.

But also a COFS so it’s injecting clean oil thru the oil system.

[Milos_Balunovic]

Why are people now calling it COFS since its idea and a design (and named after it) Richard SOHN ..... for aviation engines ...

[PaulAV]

Patent/copyright reasons

[rotatopotato]

Any decent "racing" 2T should be more than than enough - JASO FD is the latest standard which has higher detergency over FC. Interestingly I've been running Millers KR2T as recommended by Revs, however that is a JASO FC and generally about twice the price of other racing 2Ts, though it is designed for high-revving karting applications.

However, one thing I need to account for is that the oil pump I'm using is designed for pumping transmission/diff oil at 70C or above - they state the oil must have a viscosity of 350cSt (centistrokes) or lower. KR2T is SAE 40 which will be fine in most summer conditions but a bit too thick in winter, esp here in Scotland. Every other racing 2T I've looked at the data sheets for is SAE 20 which looks to be fine down to approx 3C before it gets close to 350cSt (I had an interesting couple of days looking up SAE temp/viscosity charts and reading data sheets! ).

Millers also sell their ZFS 2T which is more in line with other racing 2Ts - SAE 20, JASO FD - so this is what I'm going to use in the R3s COFS system, it's nearly the price of Exol Racing 2T (which is around £24 per 5L on ebay), so that's a bonus, and the data sheet shows it to be the "thinnest" of the few that I looked at (it wasn't an exhaustive comparison of every racing 2T out there) with a kinematic viscosity @ 40C of 33.7cSt (which puts it right at the bottom of the SAE 20 viscosity range).

Why are people now calling it COFS since its idea and a design (and named after it) Richard SOHN ..... for aviation engines ...

The SOHN is one design, RRPs COFS is a slightly different design, and what I'm putting together (with a ton of input from Carl - thanks again if you're reading this!) for the R3 bears no resemblance to the SOHN. COFS = Clean Oil Feed System/Solution, which is the problem being solved here

[Milos_Balunovic]

Why are people now calling it COFS since its idea and a design (and named after it) Richard SOHN ..... for aviation engines ...

viewtopic.php?f=25&t=74962

[Milos_Balunovic]

Any decent "racing" 2T should be more than than enough - JASO FD is the latest standard which has higher detergency over FC. Interestingly I've been running Millers KR2T as recommended by Revs, however that is a JASO FC and generally about twice the price of other racing 2Ts, though it is designed for high-revving karting applications.

However, one thing I need to account for is that the oil pump I'm using is designed for pumping transmission/diff oil at 70C or above - they state the oil must have a viscosity of 350cSt (centistrokes) or lower. KR2T is SAE 40 which will be fine in most summer conditions but a bit too thick in winter, esp here in Scotland. Every other racing 2T I've looked at the data sheets for is SAE 20 which looks to be fine down to approx 3C before it gets close to 350cSt (I had an interesting couple of days looking up SAE temp/viscosity charts and reading data sheets! ).

Millers also sell their ZFS 2T which is more in line with other racing 2Ts - SAE 20, JASO FD - so this is what I'm going to use in the R3s COFS system, it's nearly the price of Exol Racing 2T (which is around £24 per 5L on ebay), so that's a bonus, and the data sheet shows it to be the "thinnest" of the few that I looked at (it wasn't an exhaustive comparison of every racing 2T out there) with a kinematic viscosity @ 40C of 33.7cSt (which puts it right at the bottom of the SAE 20 viscosity range).

Why are people now calling it COFS since its idea and a design (and named after it) Richard SOHN ..... for aviation engines ...

The SOHN is one design, RRPs COFS is a slightly different design, and what I'm putting together (with a ton of input from Carl - thanks again if you're reading this!) for the R3 bears no resemblance to the SOHN. COFS = Clean Oil Feed System/Solution, which is the problem being solved here

It might be a problem in first 5 minutes. By the time engine gets hot its not a problem as all the pipes and OMP get heated to that temp..

My question on Sohn vs COFS naming is miss understood.
And COFS is now something that is associated with RRP (exclusively).. ie its just as "copyright strike" as it is calling it a sohn.. actually more so that it (Sohn) became a sinomin to that type of device...
Im just wondering that since before RRP introduced their iteration of same item (and idea) everybody has called it Sohn. Now that RRP is making it also most have switched to their naming... Imho credit should be kept where it is due and that is Sohn.

[kopite72]

First world problems eh?

[rotatopotato]

It might be a problem in first 5 minutes. By the time engine gets hot its not a problem as all the pipes and OMP get heated to that temp..

The issue is that the 2t source in the tank doesnt get that heat, and neither will the pump I'm using (and that first 5min still needs a solution or I risk wearing out the pump prematurely). I'm thinking for extreme cold in winter a silicon heat mat attached to each side of the tank and hooked up the acc circuit for pre-heating will be a decent solution. But it may not be required, I'm just thinking ahead for belt & braces solutions.

I say COFS because it's shorter than saying clean oil feed, which is all I mean - whether it's a SOHN, and RRP COFS, or a custom solution, they're all clean oil feeds so it's just a catch-all term for me

[Lucky 8 Racing]

20ml per 10 litres
Too much will kill the cat, took advice from Aston at Essex Rotary,

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What’s a cat ?