McLaren MP4-26 exhaust – is the “U” bend a Front Exit?

 

MP4-26 - the "U" bend is visible between the diffuser and suspension

McLaren lead the way with innovations in 2010 with the F-duct, but they were late to debut their double diffuser and blown diffuser. In 2011 McLaren appear to be right on the tail of this year’s novelty the front exit exhaust.
So far in testing, the MP4-26 has been seen completing a diligent aero programme with the car appearing with two different format exhausts. One conventional set up which blows over the diffuser and another which appears to have a “U” bend in the system. This latter solution is believed to be a front exit exhaust as used by Renault (http://scarbsf1.wordpress.com/2011/02/01/renault-r31-front-exit-exhausts-fee-explained/).

But as yet there is no sighting of the actual exhaust outlet.

Last year teams started to blow the exhaust over or through the diffuser to produce more downforce. With the method of opening the front of the diffuser up and letting the fast moving exhaust blow inside the diffuser, being the most effective route for more aero grip. Rule changes for 2011 prevented teams opening the front of the diffuser up (aside from a 5cm outer section of floor). So teams are faced with either blowing less efficiently over the floor or finding a new way. Renault have exploited another way, by leading the exhaust forward and pointing it under the front of the floor. Blowing the exhaust at the leading edge of the floor effectively creates more flow under the floor, which in turn creates more downforce. This front exit is a good aero solution, but packaging the duct from the main exhaust to the front of the sidepod is difficult due to the space constraints within the sidepod and heat rejected from the exhaust duct itself.

MP4-26 the conventional exhaust exits at the rear and blows over the diffuser

With McLaren’s conventional exhaust the four pipes merge into the collector and the secondary exhaust pipe points backwards to blow flow over the ramped outer section of diffuser. This set up has been used on and off consistently through the test. It also appears to the baseline configuration. As a lot of the aero tests using pressure rakes, flow-viz and long runs, are being completed with the conventional exhaust.

MP4-26 with the conventional exhaust exposed, the "U"bends crease in the floor can be seen

However other tests have been completed where the sidepod is revised. The sidepod features a bulge at the rear of the coke bottle, the bulged section appearing to house a revised exhaust system. Looking from the rear where the normal exhaust outlet can be seen is instead a “U” bend of exhaust tubing. With this set up the exhaust exit cannot be seen. Although several photos of sensors and cabling around the sidepod\splitter have prompted some fans and media to propose they are exhausts. In my opinion no photo as yet exposed the real exhaust outlet. With both systems, the rear of the floor and diffuser are the same.

MP4-26: This is how the "U" bend exhaust might look

Knowing the “U” bend system exists, I’ve tried to find proof for a front exit. One bit of evidence is on the launch car, which was initially unveiled without bodywork. Clearly a lot on the car was missing, but the floor appears definitive enough and just below the normal exhaust collector was a crease in the floor. This niche moulded into the floor is in the same location as the bulge in the sidepod when the “U” bend is run. Looking at its shape, I’d suggest this is where the collector and secondary pipe sit when the “U” bend exhaust is fitted. We can roughly predict that the collector sits further outboard and a little lower. The secondary pipe then curves inboard and then forward under the branch of four primary pipes (see illustration). Of course from here we don’t know where the exhaust routes, so we can’t confirm if it does blow back under the floor.

MP4-26: this is the aero rake used to measure flow accross the floor

Amongst the various aero rake tests McLaren have run, some tests features a huge array of pressure sensors in a rig mounted behind the diffuser. A later test had a simpler rig, which passes the floor ahead of the rear wheels. Initially this system ran with a conventional exhaust, and then later the rake was run with the “U” bend. I believe the rake was used to look at the pressure distribution under the floor. The two runs were used to map the different between the conventional exhaust and the improved flow of the front exit. So this suggests they are running some form of front exit.

MP4-26: the aero rake and "U" bend being run simultaneously

So where is the exit? I’ve looked at every picture I can find of the MP4-26 and I have yet to see any evidence of the front exit. I do believe its there, hidden behind the bargeboards somewhere below the sidepod inlet, or routed inside the splitter and blowing backwards. Other journalists at the Jerez test have confirmed some form of exhaust exit appears to be in there, kept out of sight both by other bodywork and the huddle of mechanics around the front of the car with the portable blowers to keep things cool when it returns to the pits. Also I’ve heard that the switch for one system to another takes 2 hours, which has reduced the McLarens track time.

But until we see a photo of the exit we can only speculate.

Notes:

This is not an exhaust

 

This is not an exhaust

 

This is not an exhaust

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46 thoughts on “McLaren MP4-26 exhaust – is the “U” bend a Front Exit?

      • I agree for the small one ^^
        I consider it also as a temp sensor

        But for the upper one, which is really big, I thought it was the real exhaust ^^ It seems I wrong

        Anyway, thanks for sharing your point of view :)

  1. Pingback: Tweets that mention McLaren MP4-26 exhaust – is the “U” bend a Front Exit? « Scarbsf1's Blog -- Topsy.com

  2. McLaren have brought us another interesting quest for information. Last year we were guessing weather the F-duct existed, what it was and how it worked.

    Renault was uncovered in Valencia, great work. Now for McLaren’s exhaust system. Clearly they don’t want to give anything away (nice try by Keith Collatine in Windsors TFL yesterday though).

    Will you be in Barcelona?

  3. would a system like f-duct which blows the air over the floor instead of the rear wing be legal? would that help create more downforce.

    • Nope. Any system where the driver manipulates airflow is illegal.

      Although on that train of thought would a system where a stall was automatically created when travelling over a certain speed work and be legal? I think I remember hearing Ross Brawn saying that Mercedes was trying/running that system last year.

    • No, the exhaust can’t be blown through the floor, because the floor can’t have any holes in it (barring the 5 cm outer portion of the back of the floor, and any extremely clever interpretations of the rules :D)

      And @ ChimpSafari – you’re right, driver manipulated aero devices are illegal – by the way the rule is written, however, in theory, a steering wheel should be illegal, because turning the tires alters the airflow around the car… :(

  4. looking at the last picture in the article (the one pointing to the gaffer tape holding down the sensor wires)… is there a duct like shape literally to the right of the red line? Could just be the shape of the floor section in the area though.

    @steven, can’t be done, rules preclude any openings as viewed from underneath (double diffusers got round that loop hole by having a limited projection in this plane… that’s now been closed off).

    I wonder if accomodation for this system is also part of the reason for the lack of undercut in the sidepods (coupled with the “U” inlets).

    • I figured there probably would be a rule. Now I know for sure, thanks. Im sure that as the season starts we will find out. I like all the inovations on the McLaren, I hope they go fast this year!! GO Lewis!!

  5. Mechanically-manipulated airflow (other than the rear wing) is not legal. What about mechanically-manipulated exhaust flow? Could a system that had a number of possible routes for exhaust flow have any benefit? Would it be legal?

    • running with this thought (and legality)…what about trying to tune an exhaust to exit different routes based on rpm? ie. slow corners/low rpm, one exit, high speed/high rpm, another exit.

      scarbs, keep up the great work.

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  7. I have seen a photo where there was a large opening where the tea tray connects under the driver. it was oblong with a turning vane in front to direct air flow close to the side of the side pod. I am unable to find the photo however this area is usually blocked by the side barge board and can not be seen.

    Possible location?

  8. These are my two hypotheses about the forwarded exhausts: A_like in the Lotus Renault, the floor is a little bit folded under the sidepod air inlet (the thin line gives a clue about it) and the exhaust gases are routed under the floor: http://yfrog.com/h6t00cxj; B_the bargeboard’s shape redirects the gases to the sidepod, over the car’s floor: http://yfrog.com/h6asufj

    The absence of any kind of thermal sensors on the sidepods, and the fact that this solution is inspired in the Renault’s make me chose option A as the most probable of them.

    Your thoughts on this, Craig?

  9. Sorry if you felt my last comment was inappropriate or spam, it wasn’t my intention to promote my yfrog account, or to harass you, Craig. I would upload the images to tinypic if that was the problem.

    My apologies again, I really enjoy your work, on the blog and on twitter. Don’t want you to feel that I’m getting advantage of it.

    Kind regards.

    (I sent this message in a comment, since I don’t see any other way to contact you privately, feel free to erase it when you read this)

  10. Wedge, I don’t think what you suggest is possible on 2 counts:

    I believe the rules only allow 2 outlets for exhausts….

    It is prohibited to use variable geometry, or variable length exhausts. Some teams experimented with dual length exhausts in the 90′s, using butterfly valves to divert gases through different length exhaust tracts.

    In my opinion, theoretically its an interesting idea to think about. Operationally though, I don’t think it would ideal, with flow under the car switching on and off mid corner, imagining it will the alter balance and vertical loads on the tyres noticeably. Imagine having to lift to correct a twitch mid corner through Turn 8 at Istanbul, or the sweeping turns of Spa or Suzuka, and having the aero balance change on you. Not nice….

    • I believe Mclaren have tested with a conventional exhaust to get a base line and also a radical exhaust. This is one of the reasons they spent long periods in the pits at Jerez. It takes about two hours to change exhausts.

      • I agree. but now it seems like they chose conventional design bacause there’s not enough time until season opening. probably this is final version.

  11. Craig, could You enlighten me on one matter – how does Renault’s and McLaren’s FEE solutions compare? It’s just that Renault seem to have designed the exhausts route much better than McLaren, we can’t see any U-bend sticking out of the back of the Renault. Would it be possible to just point out the exhausts in front straight from the engine, without u-bends?

    Also, do such long and twisted exhausts affect the engine performance? The exhaust fumes have much longer and more complicated route to exit, that should increase the pressure in the cylinders, resulting in power loss (as i understand it). Please give your thoughts on that.

    Also, incredible blog. The amount of technical knowledge you have is outstanding.

  12. Im not really an expert on this but would you get the same benefit if you made a hole in the floor(under the car) to do the same thing or is that not legal?

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    • I’ve seen this picture and analysis published in a few places. It seems to be contradictory as the picture shows the outboard exhaust outlet from the barcelona test, but then says the outlet goes under the gearbox and thru the starter hole.
      It might be the earlier “u” bend set up did this, but the barca version with the bulged floor ahead of the wheel and slit suggests to me the exit is aheade of the rear wheel.

  15. Pingback: F1: 2011 Constructor McLaren | Georgegumm's Blog

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