Exhaust Blown Diffusers: Pics from the past

In my previous articles on the subject, I’ve explained the Renault Re40 was the first F1 car to blow the diffuser(1983 first year of flat bottoms).  I got these pictures today and felt it was worth sharing them along with some insight from the man who brought the idea into F1, Jean Claude Migeot.

 This is what Jean Claude Migeot told me about the development

Exhaust blowing was on my menu of aero development during the first year of the flat bottom era (1983) as one possibility to recover some downforce. I was in Renault at the time in charge of aero and, after some checks on the engine bench as we were terrified to face another lag time (!) between throttle movement and downforce creation, I was given the green light to experiment in the tunnel. Exhaust blowing to create a fluid skirt on the side of the car (also tested early 1983) did not worked but blowing the rear diffuser was quite powerful (I remember something like 50 kg on the rear axle at full throttle whatever the speed). 

It was introduced at MonteCarlo in 1983 on the RE 40 and stay on it most of the season. It was kept on RE50 the year after (ask Derek Warwick!) and I introduced it also on the F1/86 (Canada 1986) when I worked for Ferrari later.

I remember well that in 1983 we were immediately protested by Brabham and Gordon Murray (on the basis of the exhaust blowing being a movable aero device) but Renault managed to win that case. A pity they did not return the favor to Brabham at the end of the season!!!

Diffuser blowing is specially good for traction out of slow corners but it has its downsides too. It increases balance sensitivity to throttle position which may create problems on high speed corners. Good and bad sides are quite depending on the driving style too: some drivers can take advantage of it more than others. The gas momentum available in the exhaust today is anyway much reduced compared to the turbo era (about 50%).

The Renault Re50 from 1984 split the 1.5l V6 twin turbo exhausts into two, plus the wastegate pipes, to create six outlets in the diffuser


From beneath you can see how the exhausts extend inside the diffuser Copyright: JC Migeot

The Benetton B196 blew the pair of exhausts from the Renault V10 into the centre of the diffuser


11 thoughts on “Exhaust Blown Diffusers: Pics from the past

      • EBDs will be around next year. They cannot blow into an open slot in the diffuser, except for a 5cm section nearest the tyres. EBDs will have t blow over the top of the diffuser, they will still be important as they add low speed downforce.

        F-ducts are only banned from the point of view of driver control. A passive duct like Mercedes have used, which has no driver input will still effectively be legal.

        Adjustable rear wings will be allowed, the driver can adjust the rear wing with any amount of wing any number of times, as long as he’s within 2s of the car ahead. This should aid overtaking in a straight line (less angle = less drag) and may be even more grip for the corners (more angle = more DF). If he’s in clear air then then he cannot adjust the rear wing.

        I understand this is as a replacement for the frotn wing adjustment, which is no longer allowed next year.

        So a passive F-duct will still be beneficial for lap times, such as runnign in free air or in qualifying.

        Complicated or what?

      • The wing will only be adjustable when within 2s of the car ahead? Does that mean if a driver has trimmed out his wing and passed someone on the straight, he’s then stuck with the same low-downforce setting until he comes up behind someone else?

      • It was told that the moveable rear wing will be usable in qualifying and practice at will. If nothing changed, then we may not see any passive F-Ducts..

        It’s a very stupid idea BTW, creating artificial overtaking. F-Ducts were cool, it’s a shame whey won’t be allowed any more. They could replace them with moveable wings, but without restrictions designed to create artificial overtaking. Even drivers criticized this idea, I remember that it was compared to PlayStation racing games – you push a button and overtake on the straight.

        Never heard about banning moveable front wing flaps. Are you sure? 😉

  1. I would think it would become a higher priority now that less down force can be created through the double diffusers. But I’m not an expert, and I don’t even play one on the internet 😉

  2. Look at the effectiveness of even the crude tech of yesteryear… Imagine the gains that could be made now if they could add extra exhaust! Pipes would be tuned so that the “six pipe” setup would be in harmony like a clarinet or saxaphone. No throttle liftoff reduction and I would assume massive grip gains.

    Stop turning F1 “SPEC”! Open up the genius jar, we need a Scarbs overload! =)

  3. Have you ever detailed the passive F-Duct from Mercedes? I didn’t know there was such a thing…. how is the air flow controlled without having a “non-movable structure”?

    • I believe it has to do with the pressure differentials at different air speeds. It was believed Mclaren was going to run this system before they popped the inlet duct on it before the first race. Maybe they have the passive system developed in case of a regulations dispute going against them.

  4. Interesting stuff!

    Normally downforce rises exponentially with speed.. I wonder how does the extra downforce from blowing the diffuser react – is it constant, linearly correlated with speed or it just makes the diffuser more effective.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s