SR20 swap into Datsun 620

[datzenmike]

Engineers rarely get it right the first time. All design principals have been learned by horrific accidents and lessons learned passed on to the next engineer who builds upon them.

[paradime]

6 hours ago, Wildcat Walker said:

Your first sentence tells it all. 

 

Take a quick look at the equations for momentum. Without hauling a load, but having a greater velocity than a stock truck would otherwise have, the momentum becomes equal. Heavy load, or engine swap, the braking need is the same. 

 

The calculations we were discussing previously had nothing to do with braking performance. Assuming all else was equal, we were simply developing a means to compare cylinder bore diameters, booster forces, and equate those to line pressure. The math provides a solid foundation for comparison without having to trial and error eveything, which in todays society is more costly than ever. I think they might call this process Engineering or something like that. 

 

No matter what path is taken, get as much braking as you can get, without wheel lockup. Proportion the front and the rears. 

 

Take a quick look at my post for a moment and tell me why you think I didn't understand that momentum is proportional to mass and velocity. I'm questioning it's usefulness here. BTW, that was the 6th sentence, not the first. 

 

If someone seeking a foundation to calculate adequate braking for a given weight and velocity, with modifications they sure wouldn't start by assuming all else was equal when it's no longer equal. Assuming the had a basic understanding scientific method, they would start with the relational performance parameters of a given disk size, thermal ventilation and heat dispersion, number of piston calipers, pad friction relative to heat, tire grip relative to weight on a road surface in order to calculate the amount of line pressure required from the master cylinder. I'm confident that starting at the finish point based on a standard assumption is not the logical process of Mechanical Engineering.

 

His 620 is roughly 200 lbs. heavier than my 378hp 510, so for building an SR swapped truck using physics, this translates. It stands to reason that sharing the experience of my braking system is a very logical point of comparison. Do you disagree?

[datzenmike]

I don't know what the final weight of your 510 is but 620s are 2,750 lb or at least the '75 and up are. Saying faster speed with less weight is the same as lower speed with more weight is only true on paper. We're talking kinetic energy 1/2 m v² 

 

A 2,750 pound truck at 50 mph has the same KE as a 2,250 pound 510 at 55.35 mph. The limiting factor stopping a vehicle (as fast as possible in a panic stop) isn't so much the brakes used but the traction of the tires against the pavement.

 

 If you remove the brake booster you may be limiting the maximum line pressure you are physically capable of applying with both feet while wrenching the steering wheel out of the floor with your ass off the seat. Too much brake if preferable to too little. Some stickier tires and premium pads and shoes are also a good idea.

[Wildcat Walker]

11 hours ago, paradime said:

 

Take a quick look at my post for a moment and tell me why you think I didn't understand that momentum is proportional to mass and velocity. I'm questioning it's usefulness here. BTW, that was the 6th sentence, not the first. 

 

If someone seeking a foundation to calculate adequate braking for a given weight and velocity, with modifications they sure wouldn't start by assuming all else was equal when it's no longer equal. Assuming the had a basic understanding scientific method, they would start with the relational performance parameters of a given disk size, thermal ventilation and heat dispersion, number of piston calipers, pad friction relative to heat, tire grip relative to weight on a road surface in order to calculate the amount of line pressure required from the master cylinder. I'm confident that starting at the finish point based on a standard assumption is not the logical process of Mechanical Engineering.

 

His 620 is roughly 200 lbs. heavier than my 378hp 510, so for building an SR swapped truck using physics, this translates. It stands to reason that sharing the experience of my braking system is a very logical point of comparison. Do you disagree?

But if all we were doing was discussing the impacts of changing or removing the brake booster to fit a top mount manifold then yes we would assume that all else was equal.

 

 

Edited December 24, 2023 by Wildcat Walker

[datzenmike]

Well as I see it you are watering down your braking effectiveness while increasing the need for it.

[Stoffregen Motorsports]

You guys take all the fun out if this stuff.

 

Try it and find out.

[Icehouse]

I ran my green KA 620 forever without the brake booster.  I'd only ever had none boosted cars.  When I did the KA swap I hooked up the check valve backwards so it did didn't work.  I finally figured it out going back and forth from my other dattos.  I thought damn this pedal should be easier since it has a booster haha.  Nope!  If you get the right pads, brake master and calipers balanced it will be fine.  I personally hate boosters.  I want to delete the booster from my Z.  It's way to easy to lock up the brakes.  I prefer the feel to a none boosted pedal as well.  Seems crazy to me when guys add them to a 510.  It's so easy to lock the brakes up as is I don't need any help.