I have a Logitech Momo Racing wheel too, and have just been trying it out in various emulators with little success. I've been setting the steering to X Axis by turning the wheel (so I know it's recognised) and the pedals to Y Axis.
--Taito games (Chase HQ, Continental Circus, etc) don't list a seperate axis for the pedals, all you get is "AD Stick Analog X" for the steering, so I can't get the pedals to work (the steering was far too unsensitive anyway)
--Jaleco games (Grand Prix Star, Big Run, etc) work ok but the pedals appear to be digital according to mame's input controls, I don't know if the original machines were like this?
--Sega games (Outrun, Power Drift, etc) are really weird, controls seem to be mapped okay but the accelerator fluctuates on its own, making your speed drop then pick up again at random, unplayable.
--Capcom's Slipstream the steering works but pedals only worked on the select screens and not in game
--Namco's Final Lap kinda works but the steering is so wildly over sensitive I can't play it without spinning out at the slightest touch (altho I seem to remember the original arcade being a bit like this too)
I then tried games in other emulators since Mame was proving frustrating:
--Ridge Racer (VivaNonno) steering works but couldn't get pedals to work. You have to edit the *.xml file to change the config here but I tried listing "Y" or "-Y" for the pedals and could only get them to work in reverse at best (full acceleration = no pedal pressure)
--Daytona USA (Nebula Model 2) finally a game that works properly!! I set steering to X Axis, Accelerate to Y Axis Inverted, and Brake to Y Axis... everything works pretty good
--Sega Rally, Sega Touring Car, etc (Nebula Model 2) the other games you'd think would be the same, but I'm getting some weird behaviour where if I steer while accelerate isn't depressed the car spins 180, making it really difficult to play, I don't remember the arcades doing this
So, one game out of several hours testing, better than nothing I suppose :/
If anyone else with this wheel can shed some light on how to get things working good with some games, please let me know. I've been searching google for help but there's a big lack of information (that's how I found this thread in the first place).