PUNTO INCIPIENTE SLITTAMENTO
P.I.S. for short, the Italian translation: Slip Beginning Point. This is what the Italian Auto Manufacturers are referencing when they use the acronym P.I.S. PIS also referred to as the KISS point, is a boundary set in the gear box control module(NCR)(TCU) for the clutch engagement point. The PIS is the actual thrust bearing position at the time of clutch touch or engagement. This value as you are in the scan tool parameters is in millimeters, it directly relates to the Closed Clutch Position. The PIS does not factor in clutch wear, however, friction disc surface condition (or alternate disc type like Kevlar) and clutch temperature (thermal expansion) are a factor. Furthermore, how this is set up in an F1/E gear car makes all the difference in the world as it relates to how much a clutch is worn or it’s longevity. It is the biggest single factor.
How it relates to your Exotic Experience is even more important. You could be sitting at a stop light with the vehicle completely cold, and as you go to take off, the rpms go to about 2500-3000 before finally fully engaging the clutch, and you are thinking, “what the hell is going on?” You begin to smell the slight burning of the friction discs slipping, and people are kind of chuckling at the Ferrari/Lamborghini driver who cannot drive stick shift. Unfortunately for you most don’t know anything about an E-gear or F1 car.
Very rarely do I jump into any of these vehicles and I’m satisfied with the way the previous Technician set up the PIS point. I’d give it 8 out of 10 times I’m not. There’s actually good cause and reason.
Reasons of OEM Recommendations for PIS
Let’s talk about the Manufacturer’s recommendations for these cars as it relates to the KISS point. I want to start by stating that I don’t believe I’ve once set the KISS point of any Ferrari or Lamborghini at their recommended position. The older the vehicle the less likely I would even set it close to their recommendation. (They make no recommendations for altered friction disc materials like Ceramic/Kevlar as most will not even undertake these jobs without OEM recommended clutch materials).
I guess we need to take into account that they are training Techs to be fast and efficient at what they are doing for services. They want them to have guidelines to just dial it in and get the Client on the road. It’s a great recommendation as a business model, not so much as it relates to the health of the clutch in the car itself. Just as the clutch life in a true manual car depends on how it’s driven, subsequently how much the clutch is slipped, so are these cars. Once you dial in the parameters of PIS for the car they stay this way until a Tech with gearbox NCR access comes back in and readjusts it.
P.I.S. Too Low
I think we can all guess as to what would happen if the PIS is too high in an F1 E-gear vehicle because we’ve mentioned it above. Essentially it’s that the friction discs slip against the flywheel and do not bite properly. This in turn will create hot spots (harder spots on the metal of the flywheel) that the friction discs will then ride on top of. It can also glaze over the friction discs of the clutch and even if the PIS point is set up correctly afterwards you’ll experience slippage. In sum, you don’t want the KISS point set to high, it’s not enjoyable, and creates unnecessary wear of the clutch.
In opposition to being set to high is being set to low. What exactly, at least in my opinion, were these Manufacturers trying to avoid by going too low in KISS point?
Anytime I’ve readjusted PIS points in these cars and gone too low there’s a few things that will happen. The most serious result is damage to the components themselves. This I’ve never experienced but it can happen. More than likely what happens is the friction discs drag on the flywheel and the car moves forward simply by removing your foot from the brake pedal. This is a sure sign the KISS point is too low. When you remove your foot from the brake pedal the car should not inch forward on a flat surface.
Another aspect you need to account for while setting up the KISS point outside the Mans. recommendations is Thermal Expansion of the friction discs. As we continue to discuss this topic you very well might realize why these manufactures decided on playing it safe and just giving their Techs the recommended settings for PIS they did for these vehicles. I don’t agree with it, but it’s a whole lot easier to just grab a scan tool enter the number between their recommendations, or their lowest number without thinking about it and move the Client down the street.
This is the scenario for a low KISS point that is much more likely to happen to me as I dial in a KISS for any one of these cars IF I do not drive the vehicle a good 30-45 minutes BEFORE setting it up. I set the PIS close to what I want, making sure the car isn’t inching forward on a flat surface, and take it out on the highway. After shifting up and down multiple times and leveling out in 6 gear, I’m cruising along and need to down shift or come to a stop to take an exit. As I do so, I toggle down for downshift and nothing happens. The gear indicator blinks signifying shift issues and the car does NOT down shift at all but is stuck in gear. What happened?
Let me state, this doesn’t happen to me, and hasn’t in a really long time because I always drive the vehicle to obtain maximum thermal expansion of the friction discs beforehand. I do so to avoid this very scenario. Being in Boston traffic numerous times as well (stop-n-go) the heat can be vicious on those friction discs with these high horsepower engines. You do not want to find out you incorrectly set up an F1 car by not being able to switch into gear.
Essentially what happened in the above scenario is that the KISS point was set too low and did not allow for thermal expansion which in turn doesn’t allow for enough clutch pull in order to release the shift fork. THIS is what the Manufacturers wanted to also avoid.
Along these same lines is when it’s set too low it could drop the clutch and stall the car out. Less severe it could be extremely jerky coming off the line.
As a slight caveat here, there is one other factor I’m not entirely sure they were factoring in but I think they probably were. That’s friction disc tolerance. Not every single Valeo (the OEM supplier for these clutches) clutch is the exact same thickness, or sits exactly where they told the NCR it would sit at. I believe this is also why when you have clutch wear read-outs you have people who claim their clutches are either gone before the 100% clutch wear algorithm, or vice versa have 110% wear on a stock clutch. This is more pronounced when I’m setting up a Kevlar clutch or alternate friction disc material in an E-Gear/F1 car. The last one I did I went to the outer limits of PIS of what the scan tool would even allow me to in order to set it up so as not to drag off the flywheel because the friction discs were thicker in regards to what an OEM clutch would be. Consequently, because of build tolerance thicknesses it’s another reason I feel the Manufactures play it safe and have a higher standard recommended KISS point.
Not Following OEM Recommended Settings
So let’s use an example of a Maserati GranSport that has damn near the identical F1 system in it as a Ferrari. They recommend 4.8mm being the lowest the KISS point should be at, I believe they took a safe line to allow for Thermal friction disc expansion/tolerance after being in hot traffic or spirited driving. By using this recommendation, the Client never gets stuck, but they also will generally wear the clutch out faster than if you actually take the time to dial the clutch in as it should be. I also believe this is why F1/E-gear cars clutches do not even close to as long as a standard version of the same vehicle.
Anytime I replace the clutch in any of these cars I make sure to set up the KISS point very carefully so that it beds properly. After about 500 miles of bedding in the clutch I find the car gets extremely jerky and I reset it for the Client. My key focus is not glazing friction discs or putting hot spots in the flywheel during this critical period. I tell every Client to drive as if they have their Grandmother in the car.
I will personally then set the KISS point so that it essentially engages right around 1100-1200 rpms. Now please note again, it won’t stay this way on a cold car because of thermal expansion. That rpm range will vacillate during warm-up and different climate conditions. On the thermal expanded side I make sure the car doesn’t roll off the line when hot, and isn’t extremely jerky. I worry less about the cold side because it’s the hot side that’s actually going to determine the lowest it can go.
Setting P.I.S. On Alternate Friction Disc Materials
This past year I was hired to drive down to New Jersey to set up a Twin Turbo Murcielago for a Client that was at a Tuner’s shop. It was set up so harshly that the Tuner could not get the vehicle on the Dynamometer (Dyno). Two things to note about alternate friction disc materials in these cars. Do not drive the car the same way as if it’s a stock clutch. You need to allow it to slip more through depressing the fuel pedal slowly, yes allow it to slip. Secondly, do not set it as close as you normally would. These type of clutches can take the slip and not wear out like organic material clutches can.
This specific Tuner needed to be taught how to drive an E gear car with a Kevlar clutch. The quickest way was to tell him to reverse any knowledge of how he had been driving a normal E gear car. He rode shot-gun with me and I described every step I was taking coming off the line. Patience was key, and not feeling pressured coming off the line to over-engage the fuel pedal or the car would jerk back and forth violently. Driver control is more important than bringing the PIS up to engage at 2000-2500 rpms. You want obviously to have a higher PIS than normal, but not so high that it’s dropping the clutch stalling the car out, which is what will happen.
Hi Craig
What would you recommend as a good scan tool that would interface with a 2006 Cambiocorsa to bleed the clutch and set a new PIS value?
I’d suggest Texa personally but Autel, is cheaper and also would work.
HI Craig, thanks for a good article. I have a question re the pis . The pis is a distance in mm defining an actual physical event such a when the clutch will actually start to slip when going from being closed. If you enter a different pis value how will this impact on the actual reality of when the clutch starts to slip. For example if the clutch starts to slip at 4.5 mm and you enter 4.0 mm in the TCU what will happen? This doesnt mean the clutch starts to slip at 4mm so what will happen. I would assume the engine torque will be transferred to the transmission earlier than the TCU expects ie at lower rpm and this then would result in an aggressive launch. So the rpm is controlled by the accelerator pedal so could one feather it . Of course the car may inch forward when the brake is released which as you said one doesnt want. Am i understanding this correctly?