We recently had a very interesting case with a F430 I wanted to share here.
The owner of a F430 installed our Smart eMT F1 Relay ECU Advanced Version
and had very often a warning code 7 what means that the F1 pump was cycling too often. Unfortunately, this owner ignored this warning and his F1 pump, motor and accumulator ended up in a total failure. The hydraulic accumulator and pump + motor have been replaced, complete fluid bleed done and the entire system has been checked for leaks, especially the power unit and actuator. Leakage rates were all in spec. Soon after these repairs, the Smart eMT ECU reported again a warning code 7. The official workshop asked us to diagnose what would cause this because they couldn't find any reasons why the pump was cycling every less than 15 seconds.
We installed our diagnostic tools on this F430 including our custom CAN-bus scanner and went for several test drives at different speeds. As soon the vehicle speed was exceeding 110km/h, the pump started cycling very frequently and we got quickly the warning code 7. We suspected that the E-DIFF was causing this and not the F1. The E-DIFF firmware version was 02.13 which is correct because we knew that some very early E-DIFF versions could cause similar issues.
After having captured and analyzed a lot data, it was now clear that the E-DIFF was causing all these issues. The following graphic shows that as soon as the speed of 110km/h is reached, the E-DIFF locks continuously the rear wheels at about 8% by applying a current of 500mA to 600 mA to the control valve which as a result locks the rear axle at about 3 bars. This permanent differential lock was consuming 10 bars of hydraulic pressure in no time and required the pump to cycle every 15 secs. Also, the graph shows that the E-DIFF will not lock the rear axle when the throttle is released. The control valve current rate was proportional to the car speed what means that at higher speeds, the differential had a higher lock level up to the point where the car became totally undrivable. After many tests, we concluded that the E-DIFF ECU itself was not at fault, was doing its job correctly but that an external event was causing this. Still, we faced a real mysterious and challenging situation here.
When analyzing our CAN-bus data captures, we found out that there was a strange difference between the front wheels and rear wheels rpms. Hmm, interesting. Then we realized that the owner upgraded his front wheels with 235/35 R19 tires
instead of the OEM 225/35 R19 tires
. That's a 7mm diameter difference
. One would say that's not a big deal and such a small difference should be fine. Well, we fine tuned some of our diagnostic tools to check what was really happening behind the scenes. And bingo, when the modified front tires rotate exactly 10 rpm slower
than the OEM front tires, the E-DIFF started to kick in by locking the rear axle. This happens exactly at the speed of 111.5km/h
! As the difference of wheel rpm between the front axle and rear axle is obviously proportional to the vehicle speed, the E-DIFF locked progressively further the rear axle at higher vehicle speeds. This constant E-DIFF lock at the rear wheels required the hydraulic pressure been built up continuously which as a consequence, made the Smart eMT ECU
warning the owner with code 7.
We asked the Ferrari factory to check our data and they confirmed that our analysis was correct, you cannot change the front tires dimensions without creating a consequence at the E-DIFF. They also added that under 40km/h and above 100 km/h, the E-DIFF goes in higher level of sensitivity excepting less tolerance between the front and rear axle rotation. This is valid for all Ferrari models having an E-DIFF, not only the F430. Conclusion: 1) do not upgrade the F430 front tires with 235/35 R19 tires because it will destroy the hydraulic system and eventually the E-DIFF differential clutches (except 430 Scuderia/16M). At a certain speed, it even becomes dangerous to drive with an important lock of the rear axle. 2) when the Smart eMT ECU early warns you with a warning code 7, you really need to check for the root cause because eventually, it will destroy the hydraulic system parts.