F430 Important E-DIFF information - Ferrari Life
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post #1 of 14 Old 10-27-2019, 08:19 AM Thread Starter
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Important E-DIFF information

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.
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Last edited by StefVan; 10-27-2019 at 08:25 AM.
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post #2 of 14 Old 10-27-2019, 11:44 AM Thread Starter
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PS: I didn't write it but it's quite obvious that there were absolutely no DTC error codes stored in the E-DIFF ECU, no amber slow down light etc. Such issue, except for warning code 7 of the eMT ECU, will not show any sign of an ongoing problem.
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post #3 of 14 Old 10-27-2019, 09:06 PM
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Stef- There are dozens of F430s running 235/35 19 front tires with no problems.

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post #4 of 14 Old 10-27-2019, 10:13 PM Thread Starter
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Taz, I know, they are maybe simply not aware of as there are no visible signs.
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Originally Posted by tazandjan View Post
Stef- There are dozens of F430s running 235/35 19 front tires with no problems.
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post #5 of 14 Old 10-28-2019, 02:41 AM Thread Starter
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In the same way, it's not a good idea to put new front tires, even respecting the OEM tire size, while the rear tires are totally worn out. This will make the front tires rotating slower vs the rear tires and make the E-DIFF lock the rear axle at soon as a difference of 10 rpm is detected. Obviously this will happen at a higher speeds but it will happen.

If you want to upgrade the tires on a F430, the front to rear coefficient of 0.938 maximum must be respected since the E-DIFF tolerance is very narrow. OEM front wheel diameter is 640.1mm while the OEM rear wheel diameter is 682.1mm.

It's also easy to check the E-DIFF by plugging a diagnostic tool and check at different speed levels at straight line if the E-DIFF starts locking the rear wheels (applied control valve current by the E-DIFF ECU should remain close to 0mA).
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post #6 of 14 Old 10-28-2019, 12:16 PM
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Stef- The only thing the ABS and stability control care about is the ratio between the front and rear tires being within about 5% or less of the OEM ratio. It can tell that from the wheel sensors and has a pretty good range of acceptable values to make up for tire wear, one axle only tire changes, etc. The difference in diameters between 225/35 19 tires (25.20") and 235/35 19 tires (25.48") is only 1.1% and that is nowhere near enough to cause problems.

I have no doubt there is a problem with the E-Diff or ABS on that particular F430, but do not believe the larger front tires are the cause of the problem. The system simply is not smart enough to care about that fine a difference, nor should it be for normal driving in a straight line. It can detect and react to very small differences in rotation side to side and to slippage at the rear, but a fixed ratio between the front and rear tires within its normal range is not a problem.

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post #7 of 14 Old 10-28-2019, 12:51 PM Thread Starter
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Taz - Thank you but the ABS tolerances have nothing to do with the E-DIFF tolerances. The E-DIFF firmware works in a total different way than the ABS/ASR firmware as it has a total different purpose. Anyway, I'm certain about what I'm saying since we spend many many hours comparing and analyzing data captures from different diagnostic tools and everything we found has been confirmed by Ferrari. What I posted here is just a very short resume, there's a lot more we know on how the E-DIFF firmware exactly works.

But if you can show me E-DIFF logged data of a F430 with upgraded front tires at different vehicle speeds and throttle loads, I'll be happy to look at it.
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post #8 of 14 Old 10-30-2019, 03:48 PM
 
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Stef:

Well done.

FWIW, although some on FerrariChat have recently commented on the annoyance of the beeps from the monitoring module, I find its action a great comfort.

In routine drives of some 40 miles to the same destination, the monitoring module indicates virtually identical F1 pump renewal of pressure when comparing month to month activity. I have yet to have a monitored fault since I installed the smart relay nearly three years ago.

I remain quite pleased with your product.
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post #9 of 14 Old 10-31-2019, 06:59 AM Thread Starter
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Many thanks for your kind feedback of the Smart eMT F1 Relay ECU

It's great that you never had a warning on the Monitoring Module, it really means that your hydraulic system is working perfectly fine, congrats .

In the first firmware version of the eMT ECU, the normal operation beeps (1 beep every half second when the pump is cycling) were activated by default. We changed that in the further firmware versions where these beeps are disabled by default. It's very easy to enable or disable these beeps. We even made a video that explains how to do this: https://www.scuding.com/Shop/en/cont...nfigure-videos

The most important thing is that the eMT ECU will greatly expand the lifetime of your pump and the overall reliability of the F1/E-DIFF hydraulic system. It's a digital pump motor powering device which starts the motor by providing a huge inrush current in a very short laps of time (5 micro-seconds) something a simple on/off switching device obviously can't do (like a electromagnetic relay). That means that the pump motor will immediately have all the torque needed to drive the pump and will instantly run at its maximum operating speed. Delays to pump the pressure up are also greatly shortened. With our newest version, it takes now only 2 seconds max with a OEM pump to repressurize the system from 42 to 52 bars! Compared to a OEM relay, that's 3 times less. As a result, the required hydraulic pressure is always available to operate correctly the F1 system and E-DIFF. We have a great number of race cars (not only Ferrari) running with our eMT ECU and the gain in performance speaks for itself




Quote:
Originally Posted by albkid View Post
Stef:

Well done.

FWIW, although some on FerrariChat have recently commented on the annoyance of the beeps from the monitoring module, I find its action a great comfort.

In routine drives of some 40 miles to the same destination, the monitoring module indicates virtually identical F1 pump renewal of pressure when comparing month to month activity. I have yet to have a monitored fault since I installed the smart relay nearly three years ago.

I remain quite pleased with your product.
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post #10 of 14 Old 11-04-2019, 11:08 AM
 
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Hello Stef,

thank you very much for this thread about the eDiff. It describes a similar issue i have on my 430 with no solution up to now.
Have also the Smart eMT F1 relay in my car since this summer after i got the feeling that the pump was activated too often. I get the red LED of the Smart eMT display activated only very rarely but can see a very high amount of pump activations. Never had a eDiff warning in the car so far.
When driving in a town at low speeds the eDiff valve is activated all the time (wheelspeed 0-69km/h) (have a Texa tester now so it can easily be seen in the log), driving outside of a town with speeds somehow below 120km/h the eDiff valve is off and increasing the speed (>121 km/h, eg. highway driving) the the eDiff valve is activated again and the F1 pump is activated about every 15 seconds. Pressure accumulator is new but will not help since the activated eDiff valve is causing the rapid pressure drop.
In addition it happens more and more during highway driving with constant speed in a slight curve that the "CST active" message is displayed and the engine power is reduced even on dry roads. I assume that this is because the eDiff is locked which prevents different wheelspeeds between left an right wheel.
With the tester i was able to catch such a CST active event while logging the eDiff values. CST active immediately stops once i change the lane during this event (=significant change of the steering angle). If helpfull i can share the plot.

The front and rear tires as well as the rims on my car are stock so no different tires as on the car you described.

My "feeling" is that a accurate pressure setting on the tires made the problem with the CST active worse.
The idea up to now was that i either have a issue with different wheelspeeds or one of the sensors (steering angle, lateral acceleration, yaw rate). Since the reading of the diagnosis signals from the ABS module terminates when driving faster i was looking for another solution.
I am able to read the broadcasted CAN messages but have no informations about which data is in which ID and in which byte.
The message with the wheelspeed informations i have identified so far and i assume that the values seen there have to be divided by 16 to get km/h.
Would it be possible to let us know which wheelspeed difference between front and rear wheels on a straight road is good / bad for the eDiff ? Maybe you can share a log of a car which has no eDiff activated at low / high speed ?
My idea is to play a bit with the tire pressure front/rear to confirm that i really have "only" a tire issue and replace the tires.
Is it further possible to share informations in which message ID and bytes the signals from steering angle, lateral and yaw rate are coded ?

Best regards,
Bruno
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post #11 of 14 Old 11-05-2019, 12:46 PM Thread Starter
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Hello Bruno,
Thank you for posting your detailed feedback.
Even if your E-DIFF has similar symptoms, it looks like your issue is a bit different since you have also the activation of the CST. This is something I never had with the F430 E-DIFF issue I described. If the CST activates, it would mean that a difference of wheel speed is detected between both wheels in the same axle. Maybe you have a failing ABS ring sensor on one of your wheels. Most of all, make sure that your battery is in perfect condition, these ECUs hate to be underpowered when you start the engine.

The first thing I would check, which is easy to do with the Texa, is the steering wheel angle which should be at 0 when your front wheels are straight. Then, with the Texa, try to monitor the 4 different wheel speeds at slow speed without braking if possible. The problem with the Texa, when connected to the ABS ECU in log mode, is that as soon you brake, it will stop logging and several warning lights will turn on. Make sure that all 4 wheel speeds are perfectly identical. You can also easily check the steering angle with the Texa while the car stays still. Just move the steering wheel left & right and check the values on your tool. Same for yaw, lateral and longitudinal acceleration.

The condition of the tires can greatly impact the E-DIFF too especially when they are not worn identically (bad geometry). I would recommend to remove and inspect carefully each tire.

When the E-DIFF sees that the front wheels are going 10 rpm slower than expected, it will start locking the rear axle when the vehicle speed is above 100 km/h with light engine load and stable throttle position. But if for example the ABS/ASR/ESP makes an intervention, the E-DIFF will also lock the rear axle but there are many other factors which will make this happen.

Last but not least, check the E-DIFF firmware version. Some early versions had a lot of bugs.

I hope this helps.
Stef
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post #12 of 14 Old 11-05-2019, 12:59 PM Thread Starter
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And I got also an email today from a customer who also installed the Smart eMT ECU and had warning code 7 too. He changed his front tires to 235/35 and then realized that the pump was cycling very often each time his F430 speed was exactly getting over 110 km/h. He's a very experienced competition race driver (not on Ferrari) and when he brought his F430 just for a fun drive on track, in a medium speed chicane at 140 km/h, with little throttle at the exit, the car took off with a massive rear wheel power oversteer. Fortunately, with his race driving experience, he was able to avoid a serious crash in the nearby wall. Since then, he never put his F430 back on track. It looks like we have exactly the same situation happening as I described before.
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post #13 of 14 Old 11-09-2019, 12:15 AM
 
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Hello Stef,
the hint with the brake was the important one for the ABS logging. Will try logging without touching the brake pedal next time. Unfortunately the driving season is over so this will take until next year. The steering wheel angle and the other sensors i checked already during stand still but did not see anything abnormal. Steering angle is 0 with wheels also at 0 and moving in 2,5 increments while rotation left / right. Tires have around 10.000km with only road use, no track and are looking good (3 years old). Tire pressue set to 2,2 bar with the stock pirelli tires.
eDiff SW Version should not be a issue since the car is from 2008 but to make sure i will check which version is inside. Which version names/numbers are know as good ?
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post #14 of 14 Old Today, 12:58 PM Thread Starter
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Hello Bruno,
If you have a chance, check the hydraulic leak rate also of the E-DIFF control valve. It should not be greater than 50/55 cc/min. Unfortunately, the Texa doesn't support that so you'll need a SD3/DEIS or Leonardo. Make sure you check this leak rate at different speeds.
As your car is a 2008, your E-DIFF firmware version should be fine.

Let us know what you find out once the weather allows it
Best
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