2nd Generation Specific (1986-1992) 1986-1992 Discussion including performance modifications and technical support sections.

How do you "pre Mix"?

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Old May 30, 2002 | 10:42 PM
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How do you "pre Mix"?

Please excuse my mechanical retardness. I searched and found nothing. Even though I now fully understand how to do the ATF treatment on the rotary, I still don't know how to correctly "pre mix". I am new to rotary and there seems to be a lot of tricks for this engine.

So basically, how do you do Pre mix? How do you do it properly? Instructions would be nice.

Can I do it a week after the ATF treatment?

thanks!
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Old May 30, 2002 | 10:49 PM
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premixing is adding oil to your fuel in the gas tank, just like a 2 stroke boat or motorcycle. there is a specific ratio for it, but i dont know what that formula is. the premixing practice is usualy considered to be a safety measure on 7s with the omp still functioning, but some folks diconnect the omp and then premix. there is a little more to it than that, but its a basic explanaition
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Old May 30, 2002 | 10:51 PM
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Ahhh....

How can you tell if the OMP is working? What does it look like? Also, I have a bottle of two cycle oil sitting in my garage begging to be used and thrown away.
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Old May 30, 2002 | 10:52 PM
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Add 2 stroke oil to your gas tank before you fill up.
Most people remove the MOP first. If you do, add one once of 2 stroke to every gallon of gas, or 16 ounces per tankful. This works out to around a 128:1 ratio.
I do it.
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Old May 30, 2002 | 10:52 PM
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Pre-mixing means mixing some oil in with the fuel instead of having the metering oil pump inject it directly into the engine. If you remove the metering oil pump you have to manually pour a small amount of oil into the gas tank every time you refuel.
Unless you’re planning to remove the metering oil pump (and there are plenty of threads arguing the pros and cons so please don’t ask), you don’t need to worry about it.
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Old May 30, 2002 | 10:53 PM
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Originally posted by telus.net
Ahhh....

How can you tell if the OMP is working? What does it look like? Also, I have a bottle of two cycle oil sitting in my garage begging to be used and thrown away.
Follow the test specs per FSM or Haynes. It involves removing two lines and testing to see how much oil comes out per a set rpm and set amount. It is the small thing with four clear lines coming off it on the passnger side of the front cover.
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Old May 30, 2002 | 10:54 PM
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Damn, beaten to it!
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Old May 30, 2002 | 11:18 PM
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hey scathcart.......any mention in those books about exactly how you would get those lines disconnected without removing the intake first?

I noticed that little test procedure in the Haynes manual and wondered how the hell you were supposed to do that without first taking the intake off, removing the oil injectors, pulling the oil lines out to the front of the engine, putting the whole intake back on, running the car at the given RPM/time, probably find out the MOP is not dispensing the correct amount of oil, tear the intake off again, hook the lines and injectors back up, then put the whole intake back on again. Sounds like a bunch of work to do such a simple test.

Anybody got any ideas as to the best way to measure the MOP dispensing volume without going through the above?

Can some temporary lines be hooked up to the pump itself to measure this.

I have been premixing because my car never uses any oil. It is making me wonder if the MOP is really functioning....even though I have no check engine light or codes in the ECU.
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Old May 30, 2002 | 11:23 PM
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The FSM and Haynes both suggest making or buying "temporary lines" as you mentioned, you shouldnt have to take the whole intake off of the car, as a matter of fact, im pretty sure the car is supposed to be at operating temps when you test the MOP. If you have an S4 car, the check engine code wont come on due to it being strictly mechanical, S5 cars use an electrical MOP and therefore are controled by the ECU. If an S5 MOP goes out, a code/check engine light will come on. Hope this helps and please correct me if im wrong.
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Old May 30, 2002 | 11:24 PM
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damn! Adding oil everytime you fill up? I rather spend my hard earned money on fuel injectors and fuel treatments!
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Old May 30, 2002 | 11:25 PM
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Originally posted by 91vert
hey scathcart.......any mention in those books about exactly how you would get those lines disconnected without removing the intake first?

I noticed that little test procedure in the Haynes manual and wondered how the hell you were supposed to do that without first taking the intake off, removing the oil injectors, pulling the oil lines out to the front of the engine, putting the whole intake back on, running the car at the given RPM/time, probably find out the MOP is not dispensing the correct amount of oil, tear the intake off again, hook the lines and injectors back up, then put the whole intake back on again. Sounds like a bunch of work to do such a simple test.

Anybody got any ideas as to the best way to measure the MOP dispensing volume without going through the above?

Can some temporary lines be hooked up to the pump itself to measure this.

I have been premixing because my car never uses any oil. It is making me wonder if the MOP is really functioning....even though I have no check engine light or codes in the ECU.
Yeah, unbolt the lines at the MOP from below. just catch whatever drips out. That, or go to a wreckers, cut off two lines, unbolt them from the MOP, and then bolt them on with the old lines just hanging there.
The haynes does not say to remove the oil injectors or the intake manifold).
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Old May 31, 2002 | 01:17 AM
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Originally posted by telus.net
damn! Adding oil everytime you fill up? I rather spend my hard earned money on fuel injectors and fuel treatments!
Yeah i guess you could. but if your OMP fails then now you can spend your hard earned money on a NEW engine, and new fuel injectors won't help you there. The S4's were mechanical and are very reliable. The S5 were ECU conrolled and IMO are as far away from going out as a fuse. Plus motor oil burns really poorly, whereas 2 stroke, ashless burns much cleaner. Better for emissions too. This way you can run full Synth and not worry about alot of build up INSIDE your engine. Sure you can do the ATF trick but trust me it's not gonna remove the 100,000 miles of build up in one shot. You'll have to do several and then still not get it all out.Yeah it's more work and i wish i didn't have to do it, but i guess that's what we get for working with rotaries. Think of it as an insurance.
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Old May 31, 2002 | 02:37 AM
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well, dont you have to put gas in your fuel tank every time you run out?... whats the big deal if you have to toss a lil oil in there too, what, another 30 seconds more at the gas station?.. much easier than replacing the egine if the MOP goes out IMO
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