Ferrari F150 – Starter Motor Hole – Blown Diffuser

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Ferrari are amongst many teams that have placed their exhausts down low close the cars centreline. In doing this they are passing some of the exhaust gas through the starter motor hole in the diffuser to create more downforce. This solution was likely given the cars exhaust and diffuser layout, but was proven when Felipe Massa’s fire on the third day of testing showed the flames passing not only over, but also through diffuser via the starter hole. Given the rule changes this year, this solution is surprisingly legal.

Teams were using this legal opening in the diffuser last year for aiding their double diffusers. Using the opening as an extra slot to make the diffuser more aggressive, just as rear wings use more slots to allow them more angle-of-attack. Mid season in 2010 the FIA issued a clarification to reduce the size of the slot. This formally made it into the technical regulations for 2011 as article 3.12.7.

3.12.7 An aperture for the purpose of allowing access for the device referred to in Article 5.16 is permitted in this surface. However, no such aperture may have an area greater than 3500mm2 when projected onto the surface itself and no point on the aperture may be more than 100mm from any other point on the aperture.

It doesn’t state or prohibit what else the aperture can be used for, just its maximum surface area and width can be. A rectangular slot would be 10cm wide and 3.5 cm tall, a simple round hole would be a 66mm in diameter.

As the FIA moved to prevent double diffuser, the loophole allowing opening the floor was also closed to the kind of open fronted diffuser as used by Red bull and latterly many of the top teams. With this change in the rules teams are limited in how they can blow the exhaust into the diffuser. Aside from Red Bulls exploitation of the outer 5cm of floor, the only other option is to blow some of the gas through the starter motor hole.
By pointing the exhausts along the sides of the gearbox the fast moving gas flow will pass over the top of the diffuser, when it hits the trailing edge and gurney flap it will help draw more flow underneath the diffuser.

11 thoughts on “Ferrari F150 – Starter Motor Hole – Blown Diffuser

  1. What I am wondering is how they are gonna keep this additional slit? I can’t see any slit connecting it to the starter hole and thus making it a single opening.

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  4. Craig, huge fan of your work here in America (NY NY to be specific). It’s insight like yours that drives my personal passion for this amazing sport and I just wanted to say thanks keep up the great work!

    One thing though and in no way am I trying to be nit picky or a jerk but there is a typo in this last post and I wanted to bring it to your attention.

    “Teams were using this legal opening in the diffuser last for year aiding their double diffusers”

  5. Scarbs, I have read that Williams have managed to package their gearbox in a way that the rear suspension and the rear wing support have been joined, due to a very neat gearbox? I dont know quite how this would be helpful, and was hoping for you to work some of your magic 😉

    • You’re right, the williams gearbox is exceptionally neat and low. this is for better airflow to the rear wing.
      You really should follow me on twitter (@ScarbsF1), I’ve been sending dozens (hundreds?) of updates over the launches and first test. I find twitter quicker to send snippets of info rather than post on the blog. That said I am doing a Williams FW33 tech piece and a more detailed piece on the gearbox soon.

      Heres the Williams rear in all its glory….

      • Is this the same ‘box that HRT will get, or will they just get a more standard style, similar to Williams’ 2010 gearbox?

  6. Given that KERS cars have a pretty large battery and motor already on board, the external starter is really redundant. That might give the opportunity to just use a slot in the diffuser. The technical regulations only say that ‘[a] supplementary device temporarily connected to the car *may* be used to start the engine both on the grid and in the pits.’ (My emphasis; rule 5.16.)

    The start hole seems like a loophole that should be closed, if the car has KERS.

    The rules do say that you’re not allowed to top up a KERS at a pit-stop (5.2.4), so repeated no-starts would be a problem if you didn’t have an external starter. Presumably the energy used to start the car would also be counted in the 400kJ per lap.

    As with the rest of KERS, this would be a case of road-car technology transferring to F1 – every Prius that Toyota has built over the last 13 years has started its engine from the high-voltage battery using the smaller of the two high-power motors in the transaxle. If the HV system fails it cannot start its engine, there is no low voltage starter motor.

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