1990's Exhaust Blown Diffusers

[jjn9128]

I really need to get that book. It's been on my list since release but not got around to it yet.

[Andi76]

In the 90's the exhausts exited directly into the diffuser, just downstream of the kick with the purpose of 'energising' the air flow. The cars with this sort of diffuser required a very particular style to drive - to get rear downforce and stability they'd have to get hard on the throttle earlier in the corner than was previously normal.

Great post & thanks for that!

I'm told by a Williams mechanic from the time that the EBD was on the Fw17, but not the FW17b where the the exhaust went over the top of the diffuser. This was possibly because the drivers not liking how the engine "felt" and the EBD making the car nervous off throttle as you eluded to above. However in that great article posted above about the B195, it states that;

The blowing required some adaptation work on the part of the pilot. Michael Schumacher, still in our interview in 2010, noted: "the difference in aero support between the phases where I accelerated and where I released the pedal was very significant. We worked to reduce this effect. Renault brought several solutions: "butterflies always open, ignition delayed ... We focused mainly on partial loads. Michael was excellent at keeping an identical throttle position throughout a turn. I used his skills to show Olivier Panis what to do. "

So I suspect that is the difference between whether teams used it beyond 1995 or not was the skill of the drivers, not any reg changes. I know there were changes to the diffuser at Barcelona 94 and Hockenheim, but Autosport seems to suggest that exhaust outlets positions were not changed during these raft of changes. But the diffusers were cut to reduce their effectiveness. So I can only assume the new regs raising of the cars' ride height in 1995 led to EBD being less effective. Thereby meaning that driver skill on making the EBD work for them was even more of the defining factor on whether it was kept on the car or not.

If you are still interested, i can tell you who exactly stopped using blown diffusors. I just have to take a look at my notes and technical papers. From memory i can tell you some things- Benetton in 1994 and 1995 used an extreme version of the blown diffusor, with 2 exhausts blowing in the lateral channels and 2 in the central diffusor. In Hockenheim 1995 they brought a less extreme version, as variations in downforce were just too extreme. Ferrari stopped using EBDs in 1995, as did Williams in Portugal. In 1996 only three teams used EBDs, i think it was McLaren, Jordan and Tyrell. Benetton stopped it in Kanada i think. In 1997 only McLaren used EBD. They continued untill 2001 i think. I always wondered about Neweys comment in his book as EBD never got banned in untill the 2010's and were widely used in the 80's and 90's. The reason most teams stopped using them in 1995&1996 was that driveability and less variation in downforce became the focus. Also a lot of drivers often crashed and lost confidence in their cars because of the huge variations in downforce. Also the special driving style(keep throttle open)was something that a lot of drivers were not able to do(as they would have needed to, what also was a reason for huge differences between some drivers and their teammates). Also teams became more sophisticated in relation to how to make the diffusors work better, so the need for EBDs was not there any more. So - it was a combination of things why the teams stopped the use of EBDs im the 90's.

[johnny comelately]

In the 90's the exhausts exited directly into the diffuser, just downstream of the kick with the purpose of 'energising' the air flow. The cars with this sort of diffuser required a very particular style to drive - to get rear downforce and stability they'd have to get hard on the throttle earlier in the corner than was previously normal.

Great post & thanks for that!

I'm told by a Williams mechanic from the time that the EBD was on the Fw17, but not the FW17b where the the exhaust went over the top of the diffuser. This was possibly because the drivers not liking how the engine "felt" and the EBD making the car nervous off throttle as you eluded to above. However in that great article posted above about the B195, it states that;

The blowing required some adaptation work on the part of the pilot. Michael Schumacher, still in our interview in 2010, noted: "the difference in aero support between the phases where I accelerated and where I released the pedal was very significant. We worked to reduce this effect. Renault brought several solutions: "butterflies always open, ignition delayed ... We focused mainly on partial loads. Michael was excellent at keeping an identical throttle position throughout a turn. I used his skills to show Olivier Panis what to do. "

So I suspect that is the difference between whether teams used it beyond 1995 or not was the skill of the drivers, not any reg changes. I know there were changes to the diffuser at Barcelona 94 and Hockenheim, but Autosport seems to suggest that exhaust outlets positions were not changed during these raft of changes. But the diffusers were cut to reduce their effectiveness. So I can only assume the new regs raising of the cars' ride height in 1995 led to EBD being less effective. Thereby meaning that driver skill on making the EBD work for them was even more of the defining factor on whether it was kept on the car or not.

If you are still intetested, i can tell you who exactly stopped using blown diffusors. I just have to take a look at my notes and technical papers. From memory i can tell you some things- Benetton in 1994 and 1995 used an extreme version of the blown diffusor, with 2 exhausts blowing in the lateral channels and 2 in the central diffusor. In Hockenheim 1995 they brought a less extreme version, as variations in downforce were just too extreme. Ferrari stopped using EBDs in 1995, as did Williams in Portugal. In 1996 only three teams used EBDs, i think it was McLaren, Jordan and Tyrell. Benetton stopped it in Kanada i think. In 1997 only McLaren used EBD. They continued untill 2001 i think. I always wondered about Neweys comment in his book as EBD never got banned in untill the 2010's and were widely used in the 80's and 90's. The reason most teams stopped using them in 1995&1996 was that driveability and less variation in downforce became the focus. Also a lot of drivers often crashed and lost confidence in their cars because of the huge variations in downforce. Also the special driving style(keep throttle open)was something that a lot of drivers were not able to do(as they would have needed to, what also was a reason for huge differences between some drivers and their teammates). Also teams became more sophisticated in relation to how to make the diffusors work better, so the need for EBDs was not there any more. So - it was a combination of things why the teams stopped the use of EBDs im the 90's.

did "they" go to a trailing throttle map at some stage??

[Stu]

That was the RedBull innovation, very clever mapping that effectively used the engine as an air-pump once the throttle was closed (almost certainly using the throttle input as a fuel-requirement device rather than an air-requirement device - like an old-style diesel).

[johnny comelately]

That was the RedBull innovation, very clever mapping that effectively used the engine as an air-pump once the throttle was closed (almost certainly using the throttle input as a fuel-requirement device rather than an air-requirement device - like an old-style diesel).

Thank you
It must have required adapting their driving style quite a lot

[Stu]

It seemed to suit Vettel rather than Webber, once it was gone Vettel suddenly looked quite average!!!

They used the effect right through the early 2010’s.

[Zynerji]

It seemed to suit Vettel rather than Webber, once it was gone Vettel suddenly looked quite average!!!

They used the effect right through the early 2010’s.

Webber even referred to Vettel as a "computer" for his ability to control it.

[ScrewCaptain27]

Minardi ran a blown diffuser in 2001, and Williams in 1999 as well. The latter must have been quite similar to the McLaren one, since it made the car sound quite similar:

[Andi76]

Minardi ran a blown diffuser in 2001, and Williams in 1999 as well. The latter must have been quite similar to the McLaren one, since it made the car sound quite similar:

I remember the Williams one. They went back to EBD in 1999(for this season only)after they stopped using them in 95. As you said it was similar to the McLaren as both blew in the central tunnel.

[Stu]

The Lotus one could have been a game-changer, but didn’t work out that well, was it a bad concept or just poorly executed!

[bigpat]

The application of the exhaust blowing between the 1990's and 2010's was very different. In the 90's the exhausts exited directly into the diffuser, just downstream of the kick with the purpose of 'energising' the air flow. The cars with this sort of diffuser required a very particular style to drive - to get rear downforce and stability they'd have to get hard on the throttle earlier in the corner than was previously normal. Maybe it's apocryphal but there's the story of Mansell and Piquet/Patrese getting the first EBD car and finding it hard going, when the car slid the natural reaction was to come off the gas, which lost downforce so made the slide worse. When told to stay on the gas to increase rear downforce Mansell trusted the engineers and instantly went 1.5-2 seconds faster, while his team-mate took longer to adapt. Could be one of Mansell's self-aggrandizing stories, but I think it was one of Frank Dernie's stories.

The 2010's EBD was different in that it exited on the 'top' of the car to the sides of the diffuser - the rule being that floor had to form 2 solid surfaces (step and reference planes) when viewed from below - which was added to the regulations somewhere between 1994 and 1997. The function was different too, as the diffuser kick started at the rear axle line the squirt from the tyres would end up in the diffuser flow, so the high energy gas from the exhaust was used to 'seal' the edges of the diffuser, kind of like an air curtain pushing the tyre wake away from the diffuser. At this point they were cleverer about advancing or retarding timings or cutting cylinders to maintain mass flow, so it was more automated without the driver needing to be on the gas.

Blown diffusers were used as far back as the 80's turbo era, long before the Mansell/Patrese era.
That story about the car sliding was particular on the FW 14B where with active suspension, the diffuser could momentarily stall on corner turn in, and cause oversteer. Yes keeping the foot buried would keep the exhaust flow through the diffuser, but it was the stall which was the overarching cause, but the driver needed to trust that the downforce would return, as a lifted throttle cost laptime...

[bigpat]

The Lotus one could have been a game-changer, but didn’t work out that well, was it a bad concept or just poorly executed!

From what I have read is that it worked quite well in mid to high speed corners, where the ride height is lower, but suffered against the diffuser blown cars in slow speed ( most important to lap time) corners, where the running the rear at a higher ride height was beneficial, as well as the fact that the diffuser blown exhausts offered better traction performance off the corner. At Monaco, Hungary, and Singapore was where the Lotus suffered the most....