Engine Weights...Effecting handling?

When you swap a B16, B18, or B20 in to replace a D15 or a D16 how much does it screw with the cars handling?
CRX, Civic, Integra...
let me know how your swap turned out in regards to handling issues including:
Traction at the front wheels during take offs.
Wieght distribution when cornering, braking...

I know most engines swaps are either preceeded or followed by suspension alterations... did this alleviate any problems that surfaced due to the swap?

I am begining a Project CRX right now and handling along with acceleration and braking power are my focus now.

thank you all in advance for your technical support.
what a great past time tuning is :iceslolan

If you're working with a rex, i wouldn't go bigger than a B series. But in a 92 civic hatch, no I noticed no difference in my handling, or braking. I am still using the stock VX brakes, and they are good. I had my suspension before the swap, so I can't tell you how it would be on the stock parts. Really there is only bout 85 pounds diferent between the D and the B, and about the same from B to H, so imagine a small child in your car,

imagine a small child sitting on the hood of your car. :)

I think the center of mass is located just behind where the front doors and rear doors meet, so adding weight in front of that, is good for acceleration, but bad for deceleration.

In terms of actual, but probably unnoticeable changes, cornering would produce more oversteer, or less understeer, whatever have you.

I'm assuming you know vector analysis.

If you want up to the nearest units in terms of N m^2 of the moment produced by that added weight, just use this formula, M = r x F
moment = (radius vector) x force
F= ma

taking upward as positive y

F=m(-9.81[m/s^2]) <- mass you gotta mass on your own in kg

viewing the car from the left side, that added moment in the counterclock wise direction can be eliminated if you add another moment in the clockwise direction. This can be done if you add a wing that applies the same moment.

calculate the downward force that the wing exerts. then figure out a radius(length) from the center of mass that it should be located in order to create that counter-moment.

easiest would be just to add some weight, that way you won't have to go and calculate the downforce produced by the drag in the wing.
just a simple F=m(-9.81[m/s^2]) taking upward as positive y.
solve for m = F/(-9.81[m/s^2]) = how much weight in [kg] you need

again set M = r x F and solve for the mass in the y direction.

Sorry there math racer, I was just relating from experiance and laymans terms. But since you probably copy pasted that to make you sound smart, I guess you have extensive experiance in swaps, and how motors sit in cars and react under assorted adverse conditions that you just can't calculate since there are too many variables, but next time we are in a vacuum, please feel free to drop some science.

I follow the physics and am aware that the change is front to rear weight bias will change in a calcuable amount for each engine i throw in there

but jcrx is right i cant do anything with a torque figure or a solution in Newtons
i have no way of relating that to what forces are are actually occuring with the current setup

but i do agree that the small child will be directly over the front wheels

still foggy...

thanks :sly:

viewing the car from the left side, that added moment in the counterclock wise direction can be eliminated if you add another moment in the clockwise direction. This can be done if you add a wing that applies the same moment.


the problem with that is....

While both the added moment from the extra mass, and the one from the downforce are variables. They have a different variable curve.

first of all, both moments are dependant on the lateral g's that incur from the speed/angle of the turn. (or F in your equation)

if you graph the positive y of each equation they will intersect therefor, only at the exact variable of F that would account for that intersection would the two moments equal eachother out.

other then that one moment will always be greater then the other.

:smooch: so there goes that theory....

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as for the added mass in the back, you and i both know that wont work like you want it to, obviously the force in the front of the car is not equal to that in the rear. and unless you had a way to control the amount of added mass (impossible) it would be the same way. It would undercompensate untill that intersection on the graphs of the two positive y's, at which point (and only at that point) it would equal eachother out) and then it would overcompensate.


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essentially neither would work unless you had a computer controlled variable downforce wing that would adjust the downforce according to the value of the moment on the graph of the positive y from the added mass. (which to an extent would be possible, assumng you could moniter the downforce and the lateral force applied. using the extra 85lbs as a constant on a graph, and then having a multi-variable constantly changing equation to work off of and use the intersection point to reverse the equation and find how muh downforce need be applied)

orrrrr...
a variable center of gravity device (working on the same principle of a gyroscope, but on an arm rather then a pin) that would controll front to rear weight ratios according to what was needed, and still be able to keep said ratio at it's original position (the hard part)

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probably your best bet is to not worry about it, adjust your suspension to make up for the added mass in the front and get used to it.

Sorry there math racer, I was just relating from experiance and laymans terms. But since you probably copy pasted that to make you sound smart, I guess you have extensive experiance in swaps, and how motors sit in cars and react under assorted adverse conditions that you just can't calculate since there are too many variables, but next time we are in a vacuum, please feel free to drop some science.

fyi, the information I have provided was not copy and pasted, all of those ideas came from my knowledge of the statics and dynamics course I took for my ME major. sorry if I offended you, I was just trying to get technical. why do you hate?

one thing I suggested was the wing, but this would fluctuate depending on the speed. weight in the back of the car could be added, but of course no one would want to add extra weight to the rear in order to counter the added weight to the front. the only reasonable thing to do would be to tune suspension settings like Bambooseven said. moving your car battery to the rear is an option too. battery is probably 50 lbs already.

if we took everything to be a variable, newton's laws would not apply in any system.

so, I set the frame of reference as being a static car. the system I proposed was a static car. if we took into account that all things were variable, we'd have to take into account that the earth was rotating and we all have a velocity with respect to a non-rotating earth.

I am assuming that no one would tune their suspension while their car is moving, instead they tune while the car is static, then trial and error to fine tune it.

because of the increased difference in front to rear weight ratio that the new B16 (for example) creates should i stiffen the front suspension while retaining a softer rear suspension setting?

wouldn't adding wieght to the rear of the vehicle also create a greater inertia and make it more suseptable to understeering do to centrifugal forces while cornering? or would the increase in friction the extra weight allows overcome the resultant angular momentum?

what would really help would be if someone had done the swap and could comment on what differences in handling and traction characteristics they experienced...

:confused:

Adding weight to the rear of the vehicle would not make it grip the ground any better than reducing the weight in terms of skidding outward. If you increase the weight, the outward pull would increase as well, so overall, the effect would remain constant.

When you add weight, it adds a force downward, not inward, so it would not give it better grip. But doing so, out of coincidence probably pushes your tires down so they become wider, increasing the surface area, thus more grip.

Here it is in the form of equations, again just some simple physics if you've taken a highschool course of Physics.

(force caused by friction) = (coefficient of friction)(normal force)
F = uN

N = mg so F = umg

a = acceleration toward the center

but then F = ma so
(applied force toward the center) = m(normal acceleration)
ma=umg <-- since m's cancel, increasing mass does not increase friction

a = ug
acceleration normal toward the center

you just gotta make the material more rough by increasing its coefficient of friction. Since rubber has the highest(and is the most economical material) coefficient of friction on paved roads.

In regards to oversteering and understeering, adding weight in the back would counter the added engine weight in the front(which would cause understeer) by adding oversteer. When you add weight, it also depends on where you add it. If you put it in the trunk(vs on top of the trunk), I think it's safe to assume that it is below the center of gravity, (taken from all 3 dimensions i, j, and k directions). If that is so, it would reduce roll for you as well.

As for what you can do to reduce this problem(well not really a problem. only 85 lbs huh?), just test and see what benefits the most. When you brake, the weight transfers to the front and the back lifts up(reducing grip from the rear tires). How would you tune it so that the rear goes up the least possible? I wouldn't loosen the rear because don't the coilovers pull the car down and prevent roll? Loosening it would allow the back to come up more.

I think the only noticeable difference would be braking distance. Distance will be a little longer caused by loss of grip in the rear tires. Unless you're drifting your car I don't think you'll notice that much difference.

I'm just going to use the commonsense approach.

new engine = 85lbs + old engine

A/C + washer fluid + battery + resonator box + airbag + front bumper core support + old engine = new engine

if you want the same weight it can be done. Just remove some of the following items and get a smaller battery. No one will ever know...unless it is 100 degrees, a bird just smashed on your windshield, and you have a fender bender(your car will crumble more and you will smack your head) :screwy: