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DLRA Speedweek 2019

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  • Andy
    replied
    Originally posted by theonetruepath View Post
    Yebbut... have you roasted beans with it...
    Oh yeah, this is a coffee forum eh. Nice work getting it back on a topic of coffee.

    Leave a comment:


  • theonetruepath
    replied
    Originally posted by Andy View Post
    Interesting idea, I had heard of pointing it into the rear rim for a similar effect. Our class rules say the exhaust needs to finish in front of the rear of the rear tyre, point away from the rider and the salt surface. I think where it is now is inside the wake, unlike the previous bike that was outside.

    My bike also throws a 5 foot flame when backing off (spectacular in the dyno room)
    Yebbut... have you roasted beans with it...

    Leave a comment:


  • Andy
    replied
    That's Gary Satara, he's a member of the 200mph club in that Jag.
    https://www.dlra.org.au/profiles/418.htm

    He is a really good bloke and is still doing lake entry (at least the last 3 years I've raced). The guys on lake entry get dust, dust, dust and none of the fun on the lake. They do an amazing job.

    Leave a comment:


  • Otago
    replied
    It's called Shaguar. See the DLRA Forum Build Diaries for a detailed description of its build process. Very interesting.

    Leave a comment:


  • Jackster
    replied
    That was the biggest eye opener that I had for salt lake racing. Vehicles are heavy!
    No aero, as it costs too much in drag. So they load up as much as they need in actual weight.
    The first year I went was a guy in a big block Jag (can't recall his name, but I think he was doing the lake entry inspections). I thought it looked impressive and asked if it was fast on the ¼ mile. He said not likely, it has a ¼" plate for the floor pan, and ½" in the boot.
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    Weight is inconsequential, as there is 3 miles to get it chuffing. It's the frontal area and the aero shape behind the centre of gravity that seem to be most important.

    Leave a comment:


  • Andy
    replied
    Good article Jackster.
    Your guestimates are pretty close too


    Several assumptions:
    1) This is a gas engine we are talking about,
    E85 running about 50% more fuel than it's petrol cousin. Extra fuel used to cool the intake charge (as petroleum based fuels just boiled the engine in under a minute)


    2) it is a four-cycle gas engine
    Yep.


    3) Combustion will be stochiometric and complete
    Running 0.82 Lambda up the top-end, stoichiometric would turn it into an oxy-torch at about half track.


    4) the compression ratio is about 10:1,
    Closer to 8.2:1


    5) the engine is throttled (no variable valve timing),
    Correct


    6) normal aspirated engine (no turbocharger),
    Supercharged and near twice the volume of the stock supercharger and more efficient at high RPM. It's also driven faster and in round numbers is 10 times the engine RPM so at 12,500rpm it's spinning at 125,000 rpm, at redline of 14,400 it's spinning at 148,000 rpm.
    Super secret before and after pic:
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    7) volumetric efficiency (the amount of air that makes it into the cylinder during the induction stroke) is 1.00
    My VE is lower than 1 looking at my graphical fuel maps.




    Originally posted by Jackster View Post
    But, you have a supercharged 1 litre, Google says 35psi (wow!). So let's say that's equivalent to a 3 litre aspirated engine.
    But the kicker is you not at 3000rpm, so triple the figure to 2150cfm.
    That's 61000 litres per minute!

    Obviously that is not much compared to the hole you are pushing in the air at 320kph..
    Not sure where you googled the blower output but the figure is pretty close. Stock H2 is 17psi boost, H2R is 22psi and this one we saw 37psi on the dyno. On the salt last week I wasn't logging boost (and too busy to look at the gauge) but we do log MAP (Manifold Abs Pressure) and it was 36psi odd at 10,500 rpm so would nearing 40psi and tears at redline just before I spit the crank out of the case and ran over it with the back wheel.

    Redline of 14,400 is unlikely to be seen (in one piece for long), we did the runs short shifting at about 6000rpm into top gear and roll-on the torque to 11,000rpm in top. The bike would do this up a wall, traction is my killer at the moment not HP or torque.

    A few of the fast guys (who were also wheel spinning the full length of the course) have 100kg of ballast in the swingarm, some even more. I suspect some of my off-season will be looking at pinning that tyre harder on the surface.

    Leave a comment:


  • JDCrema
    replied
    Brilliant, well done team Coffee Snob Green.
    Zed's effort would appear awesome in light of conditions etc.

    Thanks for the read and pics

    Leave a comment:


  • Jackster
    replied
    But, you have a supercharged 1 litre, Google says 35psi (wow!). So let's say that's equivalent to a 3 litre aspirated engine.
    But the kicker is you not at 3000rpm, so triple the figure to 2150cfm.
    That's 61000 litres per minute!

    Obviously that is not much compared to the hole you are pushing in the air at 320kph..

    Leave a comment:


  • Jackster
    replied
    How much exhaust volume? So glad you asked...

    Stolen from a engineering forum:

    Originally Posted by SBBlue (Automotive) - 4 Oct 04 23:46
    Okay, class. Excellent question, Jaded. Pay attention now, because this will be covered on the test.

    Several assumptions: 1) This is a gas engine we are talking about, 2) it is a four-cycle gas engine, 3) Combustion will be stochiometric and complete, 4) the compression ratio is about 10:1, 5) the engine is throttled (no variable valve timing), 6) normal aspirated engine (no turbocharger), and 7) volumetric efficiency (the amount of air that makes it into the cylinder during the induction stroke) is 1.00 (actually it depends upon the RPM and intake manifold pressure, but work with me here.)

    First, it should be intuitively obvious to the most casual observer that the amount of air that passes through the engine in will be equal to the engine displacement times the RPM divided by 2. For an engine of 3 liter displacement going at 3000 RPM, the amount of air pumped for minute will be 4500 liters.

    That will approximately be the intake volume flow for an engine with the throttle wide open. If we assume that the throttle is only open 33%, the intake volume flow will still be 4500 liters, but the pressure will be one-third of an atmosphere. The equivalent mass of air will be the same as 1500 liters at one atm of pressure.

    Neglecting the addition of the fuel mass, the mass of the exhaust gas will be the same as the mass of the intake gas. From the ideal gas law we know that the increase in volume of the exhaust gas will be proportional to the increase in absolute temperature. If we assume an intake temperature of 80 deg F, and an exhaust temperature of 1800 deg F (reasonable assumption, depends upon compression ratio), the absolute temperature will be 540 and 2260 deg Rankine, respectively. The volume increase will therefore be 2260/540, or 4.185.

    For the hypothetical 3 liter engine running at 3000 RPM and full throttle, the exhaust gas volume will be about 4500*4.185, or 18,833 liters/min. At one third throttle the corresponding flow is 6277 liters/min. Since one cubic foot is equal to 28.3 liters, the respective CFM flows will be 665.4 and 221.8, respectively.

    How about the contribution from combustion products? Assuming stoichometric combustion, there will be one pound of fuel burned for each 14.55 lbs of air. Air is 21% oxygen, so there is 3.05 lbs of oxygen available to burn each pound of gas.

    A reasonable chemical approximation for gasoline is octane, which has a chemical of C8H18. The molecular weight is (12*8+18*1)= 114.

    The combustion formula is C8H18 + 12.5 O2 ==> 8 CO2 + 9 H20. For each 114 grams of C8H18, there will be 12.5 moles of oxygen consumed, producing 8 moles of CO2 and 9 moles of H2O. For gas volume purposes, since equal moles of gas produce equal volume, the volume of exhaust gas replacing oxygen will be equal to 17/12.5 = 1.36.

    The volume percentage of oxygen in air is about 21% (not exact, but work with me here). This volume will be removed, and replaced by exhaust gas with a "volume" of (21*1.36) = 28.56%. The resulting post combustion volume is (79% + 28.56% = 107.56%) of the pre- combustion volume -- assuming no temperature increase.

    So what do we have? Combining the increase in volume from combustion reactions and thermal expansion, an engine with a 3 liter displacement running at 3000 rpm with the throttle wide open will have an exhaust volume (at 1800 deg F) of 665.4*1.0756 ~~ 715 cubic feet per minute. For the throttle one-third open, the exhaust flow will be 238.6 cfm.

    Leave a comment:


  • Andy
    replied
    Originally posted by Mb21 View Post
    post up a photo if you have one, be awesome to see!
    Too busy driving the dyno, the bike and the laptop while on the dyno to also get a picture but it's pretty awesome to see.

    Leave a comment:


  • Lyrebird
    replied
    Originally posted by Jackster View Post
    Andy, you have to point the exhaust into the wake behind the bike. The faster you go, the more important it is.
    Yep, a major cause of drag is the large trailing area of negative pressure sucking you backwards, anything that fills the vacuum will help.

    Leave a comment:


  • Mb21
    replied
    Originally posted by Andy View Post
    My bike also throws a 5 foot flame when backing off (spectacular in the dyno room)
    post up a photo if you have one, be awesome to see!

    Leave a comment:


  • Andy
    replied
    Interesting idea, I had heard of pointing it into the rear rim for a similar effect. Our class rules say the exhaust needs to finish in front of the rear of the rear tyre, point away from the rider and the salt surface. I think where it is now is inside the wake, unlike the previous bike that was outside.

    My bike also throws a 5 foot flame when backing off (spectacular in the dyno room)

    Leave a comment:


  • Jackster
    replied
    Andy, you have to point the exhaust into the wake behind the bike. The faster you go, the more important it is.
    There was some guru engineer doing testing on fast bikes. It's like a 5% reduction in drag at 200kph. I can't find the paper right now. Maybe it's gone to dark web repository.
    They were testing with speeds at the end of one racetrack straight, the modified tailpipe bikes were faster, and then slower without the pipe.
    Even if you don't believe me, make a pipe and take it next year to try. Gotta be worth trying it..

    Leave a comment:


  • Andy
    replied
    Originally posted by Otago View Post
    congratulations on another successful meet, albeit beaten by the weather this time. Even so, the results must give you great confidence for next year.
    It was a pity we didn't get more runs in better conditions, as luck (or bad lack) has it, some of the downtime for lightning smoked timing gear was during the coolest, nicest morning and would have been faster than any other day for Zed. His 123mph run was at 3pm after a 7 hour wait in the staging lane and would have been way quicker at 8am.

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    I'm now understanding just how much "the planets need to be aligned" for a great run even with all the right preparation.

    We did learn a lot from the runs we had and tuning between runs on my bike has resulted in a far better setup, we made lots of gearing changes to Zed's bike during the week and have a better understanding of the "zone" we need to be in. All good positives and we know the bikes will return next year better again.

    And that Brazen has to be the most impressive coffee maker that I've seen in a campsite! Makes an Aeropress look insignificant.
    Once again, congratulations.
    It was surreal to hear a Brazen finished beep that deep into the red dirt. Life's luxuries are a little extra special the more remote you are. The Aeropress does a fine job too and got used on the salt while waiting for a run, made in the back of a ute with a gas burner and a stainless pot.

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    Emptying the trailer at home we found it had a small air leak that we missed, Zed's rim was black when we packed the bike in, now red dirt coloured and the other end of the bike has some obvious skunk-stripe salt build-up.

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    Lots of washing already on both bikes, low pressure soaking over and over and a overdose of chain oil before the pull-down and manual clean. I think the snob van will need pressure washing inside and out, so much red/white in every crack and crevice and every surface feels sticky with humidity making the in-ground salt tacky.

    Ahh the fun of post-race.

    Leave a comment:

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