OMP removal... your thoughts?

Jim_rx7 · February 09, 2009, 01:24:28 PM

I\'ve done a bit of searching on the forum, but can\'t find that much info to be honest.

Read of people removing the OMP all together and running pre-mix. (what is pre-mix)

What are the benefits of this and are there any negatives?

Also curious as to where you would get a blanking plate for where the OMP was.

Again, what do you do with the nozzles on the top of the engine? Just blank them off with a bit of vac line and a bolt?

thanks in advance!

BlitzBoy · February 09, 2009, 02:05:00 PM

Premix is when you put 2 stroke oil in with your petrol in your petrol tank, most people add 100:1 to 125:1 depending on power levels. 100:1 means for example you put in 500ml of two stoke oil in with 50 litres of fuel. You put the oil in first into the tank then the fuel to ensure its mixed correctly.

Benefits are you can get rid of the OMP and the risk of it failing.
Even coating of the seals instead of the central part of the apex seals.
Safer on high powered Rotary as you guaranteed proper oil lube on apex seals

Negatives

You HAVE to remember to add the oil into your fuel tank on fill ups.
You will have the addtional cost of buying two stroke.
You may need to change the oil more often as you may have more oil in the sump then when you first had from the last oil change (depends on porting) .

ro284 · February 09, 2009, 02:09:59 PM

Quote(what is pre-mix)

Pre-mix is adding a good premix oil to the petrol in the tank, i use Millars
KB2T, At a ratio of 1/2 a litre to a Full tank of petrol, or 100 to 1 or some guys 150 to 1.
K.BAREHAM did a write up on replacing OMP some time ago, worth a search,
Bob

hairyhoover · February 09, 2009, 02:16:21 PM

Mark, can you explain the below again??? im confused!

"You may need to change the oil more often as you may have more oil in the sump then when you first had from the last oil change (depends on porting) ."

BlitzBoy · February 09, 2009, 02:26:23 PM

well with OMP the ecu can control how much oil to inject so on cruise hardly any oil gets injected so the right amount gets burned off. with premix you will get more oil then normally is required and not all off it gets used or burned off and gets returned into the sump, every oil change I do I end up with 1/2 litre more then when I started.

The more ported the motor you get overlap so you get wasted fuel mixture and some of that goes into your oil hence you get fuel in your oil. But this seems to affect only heavly ported engines. You can smell the fuel in the oil when you do the oil change

hairyhoover · February 09, 2009, 02:44:55 PM

Arh i see! yep mine oil stinks of petrol!!!

BlitzBoy · February 09, 2009, 02:48:16 PM

yep I change mine every 1000 miles hence the reason why I use normal Castrol or Shell Helix for my oil change no point putting something expensive to get it diluted by fuel overtime

hairyhoover · February 09, 2009, 02:53:12 PM

thats what i use shell helix! what afr do you run at idle? 10/11\'s?

BlitzBoy · February 09, 2009, 02:58:40 PM

well after doing some more research on heavy ported engines be it big street ports or bridge, you get dodgy readings, you may see afrs of 11 but this reading has been containminated by the unburnt fuel and overlap, you true afr may be 12-13.

Hence last year when I saw on my wideband my idle was 11 I tried to lean out and the engine didnt like it felt weak and wanted to cut out, so I put the fuel back in until it gave a good idle again with a AFR reading of 11.5

hairyhoover · February 09, 2009, 03:16:39 PM

anyway jim goin back to your question. I used 1 exhaust stud cut it in half ground a slot in the top of each and screwed it into the oil jet hole.

worked a treat!!

BlitzBoy · February 09, 2009, 03:30:22 PM

also you can get omp blanking plates from Reworx

karl_tate · February 09, 2009, 06:06:30 PM

or just make one.

as you know mark, im planning on running both, is there any disadvantages to this or may cause problems??

SmbFD3S · February 10, 2009, 11:08:59 AM

I run both but run a 200:1 mix really just to provide a fine coating in addition to the OMP, and shouldn\'t be as catastrophic if the OMP did decide to fail, thats my thoughts anyway lol

BlitzBoy · February 10, 2009, 11:35:13 AM

Quote from: karl_tate;582857or just make one.

as you know mark, im planning on running both, is there any disadvantages to this or may cause problems??

Yes you would have to have a ratio of 200:1 or 250:1 if running both, the main disadvantage it can lower the octane of your fuel when running both

Speedworks · February 10, 2009, 11:35:17 AM

I\'m running the PCV OMP adapter with separate oil tank. Allows me to feed pure and clean 2 stroke oil (which is meant to lubricate and burn) and the OMP still regulates the amoint that is being injected.

Works well..