Clutch Slip or Aux Pump/Tuning Issue

[Burton5251]

had my car tuned and it was brought to my attention that the clutch started to slip at ~4.4K on the E85 tune but was not present on the 93 tune (see the dyno graph below: 93 Blue, E85 Red). Upon driving the car I confirmed that the "hesitation" was present and seemed indicative of the clutch slipping. However, I thought this was a bit odd unless we truly found the "sweet spot" so to speak where the clutch began slipping.

I requested a data log (they only had the E85 pull) and you can see at exactly 4.4K the FSCM is pulling fuel pressure due to the aux pump kicking in and exceeding the requested fuel pressure. The fuel pressure then drops to 53 PSI as the FSCM compensates for the over-fueling. I know that this is a known issue that the FSCM overcompensates, the pressure undershoots the requested fuel pressure and then increases back to the requested fuel pressure; identical to what I observed in the data log.

Could this "hesitation" actually be caused by the drop in fuel pressure and not actually the clutch slipping? I find it ironic that the identified clutch slippage point is identical to when the fuel pressure drops below the requested fuel pressure.




Any insight would be greatly appreciated!

[Jukkiz]

Originally Posted by Burton5251

had my car tuned and it was brought to my attention that the clutch started to slip at ~4.4K .
Upon driving the car I confirmed that the "hesitation" was present and seemed indicative of the clutch slipping.

I find it ironic that the identified clutch slippage point is identical to when the fuel pressure drops below the requested fuel pressure.

Any insight would be greatly appreciated!

There seems to be dip in the torque curve and bumb in the rpm before, so I think the problem might be between the engine and dyno rollers. Maybe clutch.

I think with aux pump, the fscm isn't really pulling fuel pressure, it just lets the in tank pump to idle, because fpcm doesn't know where the fuel/pressure is coming from. When the aux pump can't provide enough fuel/pressure fpcm start to command more duty cycle from the in tank pump. That is semi slow process, as can be seen from your log, but I think it could be improved by tuning.

I'm just guessing,

[Burton5251]

Originally Posted by Jukkiz

There seems to be dip in the torque curve and bumb in the rpm before, so I think the problem might be between the engine and dyno rollers. Maybe clutch.

I think with aux pump, the fscm isn't really pulling fuel pressure, it just lets the in tank pump to idle, because fpcm doesn't know where the fuel/pressure is coming from. When the aux pump can't provide enough fuel/pressure fpcm start to command more duty cycle from the in tank pump. That is semi slow process, as can be seen from your log, but I think it could be improved by tuning.

I'm just guessing,

Appreciate the thoughts. After doing some logging it turned out to be both ironically enough. By logging "calculated gear ratio" it indicated that the clutch is slipping as the ratio was changing mid pull. The aux pump was a tuning issue where the min fuel pump voltage table had to be adjusted.

Just glad it squared away. Time to save for a clutch