My SC pulley is starting to go out and I'm planning on replacing it with a fixed pulley (no mag clutch). If I get the same size would I still need a tune?
278987
cars still get tuned? 
points, rotor, condenser?
what do you mean tune? sparks? coils? wires? injectors?
points, rotor, condenser? what do you mean tune? sparks? coils? wires? injectors?
Ideally, yes, the ECU should have a tune put on it with pulley modifications. This helps to optimize the performance with additional boost and helps prevent engine damage from too lean air/fuel ratios.
However, the clutch delete is a bad technical approach.
The supercharger is normally engaged and only lets go the clutch on throttle closed (preventing excessive intake tract pressure) or to protect the engine in the event of other faults or excessive air intake temps. For example, if the intercooler pump were to fail (as they often do), the intake air temp can quickly reach excessive levels and again cause lean burn damage (melted pistons and valves) (oddly with no fault light!). The clutch is a safety feature best left in place, and no significant performance gains to remove it.
You can get an inexpensive OBD wireless adapter and phone app to monitor boost, just for fun..
Aluminum pullies can fatigue and fail (at 20k RPM), so better have a scattershield - or better yet, go with a stainless pulley. There are many stories of pulley failures with holes in the hood, destroyed oil coolers, etc.
And, while looking at pulleys, inspect the lower crankshaft pulley, also known as the harmonic balancer. It has an inner and outer part with elastomer layer in between. The harmonic balancers of this era were known weak points from elastomer failure and Mercedes even had a recall on this. (yours may have already been replaced)
Watch it spin at idle, if there is any wobble, its bad,
Inspect with engine off, if there is any elastomer layer degradation, little bits missing or hanging out, its bad.
Allowing this part to fail will have one of 2 outcomes - if the outer pulley ring slips off to the outside it will just strand the car. If it slips off to the inside, it will also tear thru the timing cover and you will be in for major expense + a new harmonic balancer. If it looks iffy, proactively change it ($400+labor,, genuine parts, no shortcuts).
Happy top down spirited motoring, reliably.
R
However, the clutch delete is a bad technical approach.
The supercharger is normally engaged and only lets go the clutch on throttle closed (preventing excessive intake tract pressure) or to protect the engine in the event of other faults or excessive air intake temps. For example, if the intercooler pump were to fail (as they often do), the intake air temp can quickly reach excessive levels and again cause lean burn damage (melted pistons and valves) (oddly with no fault light!). The clutch is a safety feature best left in place, and no significant performance gains to remove it.
You can get an inexpensive OBD wireless adapter and phone app to monitor boost, just for fun..
Aluminum pullies can fatigue and fail (at 20k RPM), so better have a scattershield - or better yet, go with a stainless pulley. There are many stories of pulley failures with holes in the hood, destroyed oil coolers, etc.
And, while looking at pulleys, inspect the lower crankshaft pulley, also known as the harmonic balancer. It has an inner and outer part with elastomer layer in between. The harmonic balancers of this era were known weak points from elastomer failure and Mercedes even had a recall on this. (yours may have already been replaced)
Watch it spin at idle, if there is any wobble, its bad,
Inspect with engine off, if there is any elastomer layer degradation, little bits missing or hanging out, its bad.
Allowing this part to fail will have one of 2 outcomes - if the outer pulley ring slips off to the outside it will just strand the car. If it slips off to the inside, it will also tear thru the timing cover and you will be in for major expense + a new harmonic balancer. If it looks iffy, proactively change it ($400+labor,, genuine parts, no shortcuts).
Happy top down spirited motoring, reliably.
R
One relatively harmless bit of massaging, is to have the factory pulley machined down from stock 74MM to 70 mm, then add a tune. This will probably add another 20-30Hp. The pulley can be safely machined to 69mm, but extra margin is good. Eurocharged is a good source of tuning and dyno testing.
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