How to retain the OMP?

[Lucky]

Hoping someone can offer wise advice on this one, or allay some of my worries at least!

The main question I have is, how do I go about plumbing in the oil metering pump when replacing the carburettor setup? The original one has an actuating rod from the throttle linkage on the Nikki carb that opens the pump, and two lines from the OMP into the carb venturi via brass nozzles (this is on a Series 3 RX-7, though the new engine is from a Series 2, I think. AFAIK, all the OMP/Nikkis are the same though?).

The manifold I have for the new Weber has a blank boss cast onto each pair of runners which I guess are intended to drill and tap for OMP nozzles. This isn't a problem, but will it matter that the oil will be introduced into the mani rather than the carb itself? I don't want to run into problems of pooling or dribbling oil rather than it getting misted in with the fuel. Also, how to actuate the OMP itself? Just adapt the linkage rod onto the Weber throttle linkage? Has anyone done this?

And I'd prefer not to go to premix, before anyone says. It's a pain in the posterior I'd prefer to avoid if at all possible. All insights and suggestions welcome though

[Chud]

On the IDA on Nev, there is a hole on each venturi which are the perfect size for the stock OMP lines. Now whether these are an alteration to the carb I don't know but they do the job. I'll brave the cold in a bit and post a pic up.

Regarding the OMP itself, ours is just set to 'flat out'. Doesn't seem to have any detrimental effect on the idle smoke.

I wouldn't have thought theres any problem with having the lines go into the inlet assembly though - remember, the 12AT go in the centre plate and the 13BT have them in the housings…..

[Chud]

Here ya go….



Ignore the twaddle about the 12AT, I had a momentary brain fart. I got my injectors and OMP's all ass backwards.

If you look far left of the IDA on the opposite end to the throttle cable - you'll see a sort of cam with a hole in it. I'm guessing back in the day that would have regulated the OMP.

[TOOL]

Yes, brain fart.

That is amodified IDA. They don't come with that stock.

Re the "cam" thingy, not sure what these are for. Perhaps connecting up multiple IDAs as in V8 set ups would be my guess.

More than one way to skin a cat. As mentioned here: http://www.mazdare.eu/viewtopic.php?f=1 ... p=277#p277

[Lucky]

Thanks for the photo, Tim. Yeah, I noticed the spurious cam on the carb and came to the same conclusion as MR TOOL that it's probably something for like Jags to sequence multiple carb linkages from. I guess it could be adapted for OMP linkage, though it looks as though the rod would end up going through quite a few bends, not sure how useful that'd be. Since you guys seem to get them to work happily just fixed wide open, that would seem the way forward. It's the failsafe option isn't it; if I made some really long bendy linkage that then screws up with the OMP shut, that's not such a bonus

Cheers for the reply, though, that pics' useful for helping me visualise it without all the parts to hand

[Chud]

No worries, I just need to do the rounds first in future to see where everyones putting their input at that point in time so I'm not at the party al by myself.

[JayoM]

When we carb'd the 13b, after reading a few forums and talking to some rotorheads around Ireland, we just set the OMP permanently to 9 o'clock. No problems so far