I have an 1989 S5 convertible with a failing OMP. I would like to disable my OMP and start premixing. I was thinking I could use one of those RTEK 1.0 chips, but have come to find that is not an option, if I cannot find one. What are you guys using? Are there any other cheaper alternatives to using Haltech, Power FC, etc?

 

I went with a Haltech Sprint RE. Wasn't too much for an aftermarket ecu (has onboard MAP sensor too). Welded omp spot shut and plugged the oil injector/dripper holes with small bolts. Gotta premix every time though. There is the aviation omp setup you can add that premixes also.

 

Seems Overkill to run a EMS when all I need is omp disabling. Are there any alternatives?

 

Oh yeah my B you got a vert XD Yes it would be overkill. I had to go standalone when doing my cross series swap so I'm not sure on a cheaper alternative for your ECU situation unless you can find the one you stated :/

 

Why not just use block offs like XBLADE suggested? You do not need an ECU to do anything. There is a thread telling you what size scews to use if you don't want to buy a kit for this as well and would be cheaper. I also removed my omp and blocked it off as well as the lines. I just premix now. The kit below is $25.

FC3s OMP Elimination Kits

 

you can do that, though it still leaves a big bulky junky S5 OMP flopping around in the engine bay.

 

Yea my previous owner just mounted it up near the airbox mounted near the atmospheric sensor I mean, it's not in the way but meh... A trained eye can spot it here..

 

but he said his omp is failing, which SHOULD mean he's fighting limp mode

if this is the case, your only options are to replace the OMP with another one. Find a used Rtek for sale that matches your ECU #, or go standalone

 

You are correct lduley, I am getting a code 20. . Luckily my ecu isn't fried, but I may not be so lucky next time, the stupid OMP fails.

 

maybe try finding a used one

 

OP - chances are your code 20 problem is NOT the OMP or the ECU, but is most likely a poor connection in the associated wiring. Fact is, unless you recently replaced the harness with a new OEM harness, that thing is probably very corroded, and has lots of brittle, crispy & broken insulation after almost 30 years of use. Doesn't take much to have intermittent open circuits or shorts with these old harnesses, either of which would cause the ECU to flag an error (limp home mode for anything OMP related) or end up frying itself. Solution is to rebuild harness or buy a new one. Buying a used harness is a gamble, unless it was one that was recently purchased, say < 5 years old.

Test the OMP stepper & position sensor per the FSM (disconnected from harness - simple resistance tests IIRC); that would tell you whether or not the OMP is good.

To those who said he can just disconnect the OMP and do a block-off plate & premix, that won't work on a S5 car with stock ECU - ECU will keep him in limp home mode unless a working OMP remains wired in.

 

^Yup. s4 omp is mechanical and s5 is electric.

 

Do believe I said that? lol

 

if the OMP isn't completely failed you can still use it remote mounted and bypass limp mode though.

 

Clarified for accuracy. To dodge limp mode in an S5, the OMP needs to be electrically functional, to include the ECU getting correct feedback from the OMP position sensor.

 

generally the car won't go into limp mode as readily, if the OMP isn't mounted to the hot engine and isn't spinning. at least that has been my experience with most of the failed ones that turned into ornaments that kept crapping codes once the engine got hot. it's the ones that go into limp mode immediately after starting a cold engine that usually you cannot do such a thing with, those are hard wiring faults, fried ECUs or internally completely shorted OMPs.