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Automotive Standing mile race car twin engine heavy front end?

  1. Oct 30, 2016 #1
    got a twin ls1 standing mile car project I've been toying with for a while.My question is the engines have beeen fit in the engine bay with the rear motor having minimal setback to allow room for the front engine,the total weight for both engines is 760 lbs,half of that weight is ahead of the front axle vehicle is a 87 brick regal rwd platform,I know it will be traction limited off starting line but I'm not drag racing so the initially starting line traction isn't too much of a concern,would having a heavier front end help reduce front end lift at speed and keep it more stable,or would it lead to swaying and being unstable at high speed.
     

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  3. Oct 30, 2016 #2

    Randy Beikmann

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    With the power of two LS engines, your acceleration might be traction-limited out to a pretty high speed. The power you can put to the ground at a given vehicle speed is Force x velocity, the force being the traction available at the drive wheels, and v being the vehicle's speed. (I'm assuming it is only rear wheel drive.) Just throwing this out there: if the engines can put 700 HP to the rear wheels, and you have 2000 pounds of traction, I calculate that you are traction-limited out to about 130 mph! You'd have to put better numbers in to find out your actual traction-limit speed.

    Your traction-limit acceleration value (in g's) will be reduced somewhat of course by having a relatively small percentage of the vehicle's weight on the drive wheels.

    As for stability, you should find out your corner weights. FWD cars commonly have about 60/40 weight distribution, and you might not be too far off that now. Bonneville cars run a large percentage of their weight toward the front to increase stability, but I'm sure it can be overdone. Ideally, suspension spring rates should be proportioned for the new weight distribution.
     
  4. Oct 31, 2016 #3

    Ranger Mike

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    congratulations if you managed to stuff in two engines in that car package
    Without going into a lot of technical stuff, you got a real hand full there. This much weight on the front end will definitely change the whole geometry settings , handling, traction and safety.

    Without knowing the empirical data like wheel base, % front to rear weight, , etc.. I can tell you the Center of Gravity is changed, polar moment, camber build, scrub radius, Roll Centers are not correct, stock springs, anti roll bars (sway bars) are wrong. same with dampers (shocks). Both front and rear!
    I think you can get fairly good handling but will require a lot of rework.
     
  5. Nov 2, 2016 #4
    You always want the weight of your engine as far back as possible to keep balance and weight down on the rear axle without lifting it up. with an engine hanging over the front axle you may need to weigh down the rear end to gain a better traction.
     
  6. Mar 1, 2017 #5
    You might also want to (roughly) calculate longitudinal load transfer's effect on rear wheel traction since its probably going to be WOT and accelerating the entire time it is in the top gear.
     
  7. Mar 1, 2017 #6
    Your front end is going to load the suspension more, obviously. You will want to get stiffer springs in the front and also look at a way to increase suspension dampening. Increasing suspension dampening will be necessary due to the fact that you will have more spring force to tame on rebound, as well as more momentum created if the compression or rebound stroke is too fast. You want the suspension to be stiffer than it is now, and you want it to react more deliberately, which requires dampening.

    Another thing you should consider is wheelbase modifications. One way to help that car work correctly would be to move the front axle farther forward. This would move the fulcrum in such a way that more of the load center of gravity would be on the same side of the fulcrum as the rear wheels. It would also give better control over yaw because your wheelbase is longer.
     
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