As part of my future R129 SL track day car, I'm investigating throttle bodies. The end goal is to develop a streetable motor in the track car, transfer it to the road car, then develop something more involved for the track car.

97 M104 3.2L Running Bosch ME 2.0 / 2.1 ( depending on whose info you use. )

Stock throttle body
MB 104 141 00 25 Bosch 0 205 003 042

Bore 70 mm
Max possible bore 75 mm
Bolt pattern 4 on 70 mm square
Hose hub 83 mm

From comparing pictures, the M119 ? ( mid / late 90's SL500 motor ) has a larger bore but same pattern. Anyone have one to confirm? Part numbers are helpful too. Non MB throttle bodies ar a possibility as well.

One of my early steps is to disable the servo motor and rig up a direct throttle cable. Has anyone tried this?

There might have to be some fooling of the computer so it does not go into limp mode. My 97 SL320 road car has the same system but throttle response is soft hense the reason for a direct connection.

The issue isn't that the motor it self lays down, it is that the throttle seems to lag in opening. Also, in a forced multi gear down shift from say 3 to 1st, The motor just hangs there 1000 RPM over pre downshift while the trans and throttle catch up to each other.

Thanks

if you just want a snappy throttle you can just put in a sprint booster. As far as forced multi gear downshifts that is what you are going to deal with on the factory tune and transmission setup.
Also you should be able to have a tuner adjust the throttle ramp in the tune. Maybe not if you have 2.0 but I still think this can be done.

Hmm, I'm thinking the sprint either full time rescales throttle peddle output ( peddle 1 V out = 2 V to engine computer ) or overshoots voltage to the computer for a short time ( peddle 1 V out = 3 V to computer then drops to 1V )

It looks like there isn't a lot to do here and it seems that nothing can be done with zero to full throttle snap as there is nothing to overshoot / decrease rise time.

The feels like the aftermarket round throttle cam so loved by the Porsche 944 guys. In this case, the original oblong cam that gave long throttle peddle sub 50% to enhance slow speed drivability. The round cam gave linear response making the car feel like it has more power when in reality it does not.

At some point I'm going to scope the throttle peddle and body and see how closely they follow.

As for tuning, there seems to be a big gap in services between pre OBD 2 and mid 2000 cars. The 97 good car needs to be OBD2 / original hardware as possible, the 91 track car can eventually be anything.