How to shave 2 seconds off the ET of a econobox to get it into the 14's, with virtually no cost modifications. I wonder if a future version of LFS will allow such simple mods as shown and discussed in this informative thread:
I was getting ready to rubbish the article, but for once there isn't a single mis-truth in the whole article. Anyone into their cars should read this. A lot of the stuff is 100% applicable on the road too, although some of the later mods might be a bit far for load legality.
Cool. Although I'm sure high speed acceleration will suffer, that surely can't be more aerodynamic. I'm mostly impressed with how much weight they saved.
It's amazing to me how many people in club racing really don't take this to heart. Can anyone take a guess as to how many roll cages in BMWCCA don't use Chrome moly as their metal of choice? As far as I can tell, I'm the only cage builder in the series who uses the stuff. Mostly because other builders charge outrageous prices to install chrome moly because they don't want to take the time to preheat and anneal the welds. But a chrome moly cage can save 100lbs (45 kgs) or more.
We just finished building a new car for our shop. This car isn't a customer's car. It was built by us for us. This means that we sparred no expense in weight savings and chassis strength. The chassis is a BMW E36 which normally weighs in at ~3200 lbs (1450 kgs). After we were finished with it, it weighed in at just under 2200 lbs (997 kgs). It has an extensive cage that ties into all the suspension/subframe mounting points. It still has the heavy iron block straight six (for durability's sake) and giant 18 x 305 tires and wheels. There's still weight to be taken out of the car.
Here's the thing. Everyone says the magic number for this chassis is 2400 lbs (1088 kgs) and if you get under that you're a magician. I mean, big time builders are saying this. People who've spent a decade building these chassis are all saying that. Recently, Jon posted the weight on a BMWCCA message list and got a very lukewarm response. NO ONE BELIVES US! Well, it's going to be fun when we show up at an event and roll that thing up on the scales for all to see and then go out on the track and proceed to kick their ass with 40 less HP.
Wouldn't the removal of the factory body affect aero though
The weight of the panels that have been removed would probably not counteract the aero affects on a proper circuit. But for drag racing, that's , erm , kinda useful.
Did you post about it on Bimmerforums? I think I might have seen that. To say the response was "lukewarm" is a bit of an overstatement. I don't think the response was even that positive. Sounds like you guys put together a winner, though.
Most GT, rally and touring cars are built from shell up. The shells are substancially strengthened over the road cars. Normally they are fitted with transmissions that are considerably different to the road cars. The engines are normally production 'based' that normally means making a produtcion block out of better quality alloys (I don't beleive the story of the 1000 bhp BMW F1 turbo engine being a used production block) then completely rebuilt with components some of which resemble the production ones just built at much finer tolerances and some which don't really have anything to do with the production car. Homologation specials are a useful way to get things into the race car but the homologation cars are still only road cars with some fancy bits bolted on.
Well, to be fair, magnesium and Kevlar have their uses too.
Of course, if you really want to see what can be done with stripping down a car, just look at an Ariel Atom. 300HP, 500Kg. As long as it doesn't come to a top speed battle, it'll outrace cars costing literally 10x as much--and that's before you add the downforce package.
It's also got a curved beam backbone, which goes to show that even uncompromised cars like the Atom are HEAVILY compromised by looks. Engineering rule of thumb - Never use curved beams for supporting loads.
If they had used a straight section(s) then the car could have been made with smaller diameter tubing, making it even lighter and stiffer. But no, they wanted it to look 'impressive' and missed their chance.
At least there is room for improvement with the Atom2
We don't have a build story on the website. In fact, the car isn't finished yet. It still has to go to paint and then final assembly can begin. The mock up actually weighed in at 1910 lbs. When it was weighed the car had no hood on, had no seat, windshield, quarter windows or dash (which will be a small carbon fiber panel that just holds the tach, temp, oil pressure, oil temp and switches for the windshield wiper and so forth). The cage wasn't completed yet. We were still missing about 30lbs of cage. It did still have the glass rear window in it though. That's going to end up being plastic like the windshield. So, 2200lbs for the final product is a pretty conservative estimate. I think this car is going to be lighter than our wrecked E30 that we raced last year. It came in at 2181lbs with a half tank of gas.
One thing we did that we haven't seen any other E36 club racers do is we completely cut out the rear firewall that separates the trunk area from the passenger compartment. It's going to stay like that too as we're using the stock fuel tank. SCCA/NASA/BMWCCA have designated that the E30/E36 can use the stock tank since it's plastic and located in front of the rear axle/subframe. Fuel cells typically weigh more than BMW stock gas tanks. Most people in BMWCCA use a fuel cell. I'm not exactly sure why they do this with the E36 chassis since the fuel starvation problems prevalent with the E30 is a non factor with the E36 and a duel fuel pump setup. I guess because it has a high cool factor. Anyway, since there wont be a fuel cell back there, we wont be needing a firewall. Another thing we've done is completely cut out the trunk floor sheet metal and replaced it with sheet aluminum. We've even cut off the frame rails aft of the subframe and replaced them with 1.5"x.095 chrome moly to mount the gutted rear bumper to. Don't worry, the entire rear subframe/suspension is located and mounted to the cage. This includes the upper shock mounts which are boxed in with .095 sheet steel. The rear fabbed frame rails are mounted to this box as are the rear trailing arm mounting points, and all four subframe mounting points. The rear down tubes for the cage are also mounted to the boxed in shock mounts.
These are all things we haven't seen from any other car we've examined at the track. The thing is, we want to win. We just don't have the kind of coin the other front runners have. What we do have is know how and time. So, we try innovative stuff like fitting 18x305 slicks onto an E30. Yeah, they all said that couldn't be done either..but we did it anyway. One thing we can't do is spend $20,000 on a motor, so we are constantly underpowered. Last year we were down an estimated 60 hp from the other top competitors. Next year is going to be just as bad. One of the top CMod drivers will be moving down to DMod next year. He's going to be bringing a de-stroked 3.0l Euro M3 motor that we estimate will be putting out 340-350hp (incidentally, we built that car). This is going to be the first time some one's going to be running that moter and after he shows up with it, others will migrate. We can't even come close to matching that. So, where's that leave us? We aren't going to go racing just to give a good showing. We're going racing to vie for another championship. So, we've got to do stuff no one has ever tried before. We've got to push the envelope of chassis fabrication. Getting light has always been our mantra. This year we're taking it to a whole new level.
Well, technically, the current atom is the "atom 2", (the original had a rover engine, now its got a honda engine) but I know what you mean.
I think the curved beam is fine, and wasn't necessarily just for looks. First of all, the side beam has to be high and wide in the middle for side protection and space for passengers, but low and narrow in the front and back for the suspension mounting points--so a curved beam is a simple solution. An additional reason for a high middle is greater stiffness--by increasing the distance between the upper and lower beams of the truss on each side, the stiffness increases,
Secondly, the primary loading forces are all more or less in the plane of the curve. If the force was longitudinal, then a curved beam would be terrible because it's already on its way to buckling. In this configuration, where the main loads are pushing the two ends upwards against a central downward load, the curve acts like an arch. Arches are better at supporting this kind of load than a straight beam.
Finally, using the smooth curve minimizes the number of beams needed to make the frame. With straight tubes only, seperated pieces would have to be welded on to allow the chassis to narrow at the front and back, which means sharp angles with welded joints, which are weak points prone to flexing and breaking. With the curve, they can use a single, continuous tube almost the full length of the car.
Really, if you want to make it any lighter, I think a better way would be to make it single-seater. But then it would lose what little practicality it has--in other words, if they do make a single-seat version, they should keep making the two-seater too.
