Random thoughts thread

[OrbitalEllipses]

Originally Posted by IntotheOcean

Lol no its not today... Thank you though.. It was awhile ago..
I dunno my life is backwards. The only guy who got me a birthday card and gift was my teacher friend-not my father, and not my ex's/current fuck buddy(at this point why the fuck would I call him bf)
I think I'd probably start crying if I ever meet a guy who cared enough to go above and beyond like that. -Le sigh-
I set myself up for this shit. I need to be single but don't know if I'm strong enough-talk about being pathetic. Ah well...

And that's why.

[Re~Mix]

I think I was my car more than I clean my apartment... Priorities...

Just looks so sexy sparkly clean in the Cali sun.

[SVTSHC]

Originally Posted by OrbitalEllipses

Well you should, because a lot of those luxury lines aren't that dependable/reliable. Perhaps across the boars it might appear that way but I know for a fact all of the German brands have at least one model that's rock solid to carry their ratings. For instance, Porsche's 911 is way above average but their Cayenne model actually has below average ratings (lol VWAG engine); it's just the same for the other German brands. There's a reason that people say they won't own one outside of warranty.

Noooo I said I don't count them because I personally have zero interest in Luxury lines at the moment. Whether they're amazing or below the standard I don't see myself owning anything from a Luxury line for more than a few years, I like my not-so-comfortable modded DD's :P.
Trust me I know aaaaalll about how undependable some of the luxury brand individual platforms are. As far as I'm concerned the E65 was one of the worst series of BMWs ever made .

[IntotheOcean]

Originally Posted by Jayde

What part of NY are you in?!

I'm from massapequa and work in Oceanside. So I saw this cool dude on sunrise highway

[IntotheOcean]

Originally Posted by OrbitalEllipses

And that's why.

wait, what?
It was a figure of speech lol

[Dimman]

@Calum How deep is your hydraulics knowledge? I have some damper-related ideas floating around in my head.

[Jayde]

Originally Posted by IntotheOcean

I'm from massapequa and work in Oceanside. So I saw this cool dude on sunrise highway

Awww Long Island.

[OrbitalEllipses]

Originally Posted by IntotheOcean

wait, what?
It was a figure of speech lol

There's a little bit of truth in everything.

[Dimman]

@serialk11r

Any chance you can share/teach me the math/physics to break down mean piston speed to reasonable estimates at which positions as the piston moves through its stroke? Say if I want to break down piston speeds into 5-10° blocks.

[IntotheOcean]

Originally Posted by Jayde

Awww Long Island.

People here mostly suck at driving lol. Lots of first pumpers and sluts. I'm very lucky the customers at my job are nice-just very...... Dense; to put it nicely

[Want.FR-S]

Originally Posted by Dimman

@serialk11r

Any chance you can share/teach me the math/physics to break down mean piston speed to reasonable estimates at which positions as the piston moves through its stroke? Say if I want to break down piston speeds into 5-10° blocks.

If I may...

Quoted from Wiki: MPS = 2 * Stroke * RPM / 60

http://en.wikipedia.org/wiki/Mean_piston_speed

This is the *average* speed of piston so it does not give you instantaneous speed at any given crank angle.

Having said that, here is another explanation about piston speed:

http://en.wikipedia.org/wiki/Piston_motion_equations

There are equations where the instantaneous speed, position, and acceleration can be calculated based on rod length and stroke size. You can build a spreadsheet to calculate these values based on these parameters to your liking.

Hope that helps.

[Dimman]

Originally Posted by Want.FR-S

If I may...

Quoted from Wiki: MPS = 2 * Stroke * RPM / 60

http://en.wikipedia.org/wiki/Mean_piston_speed

This is the *average* speed of piston so it does not give you instantaneous speed at any given crank angle.

Having said that, here is another explanation about piston speed:

http://en.wikipedia.org/wiki/Piston_motion_equations

There are equations where the instantaneous speed, position, and acceleration can be calculated based on rod length and stroke size. You can build a spreadsheet to calculate these values based on these parameters to your liking.

Hope that helps.

I forgot that you are a fancy math/physics guy, too. Thanks.

The mean piston speed formula I have, it's the instantaneous ones I want (I think).

I want to look a little deeper into what's going on during the intake and exhaust strokes, and what effects different cam profiles, port sizes and valve diameters have.

Something I foresee having difficulty with is air's inertia. There are formulas for estimating average port velocities from mean piston speeds. But it's not instantaneous, right? The gas flow 'lags', right. Piston goes down creates a vacuum, air tries to equalize pressure by running down the port, if it comes in fast enough it will continue filling even as the piston starts to rise. But how long does it take before it starts to flow, and how long can it continue to flow against a rising compression piston?

But I will start with just instant velocity estimates for now.

Thanks.

[Want.FR-S]

Originally Posted by Dimman

I forgot that you are a fancy math/physics guy, too. Thanks.

The mean piston speed formula I have, it's the instantaneous ones I want (I think).

I want to look a little deeper into what's going on during the intake and exhaust strokes, and what effects different cam profiles, port sizes and valve diameters have.

Something I foresee having difficulty with is air's inertia. There are formulas for estimating average port velocities from mean piston speeds. But it's not instantaneous, right? The gas flow 'lags', right. Piston goes down creates a vacuum, air tries to equalize pressure by running down the port, if it comes in fast enough it will continue filling even as the piston starts to rise. But how long does it take before it starts to flow, and how long can it continue to flow against a rising compression piston?

But I will start with just instant velocity estimates for now.

Thanks.

Just so that we can understand this together. The speed equation is with respective to the crank angle. It does not relate to the RPM. Therefore, to measure the *true* piston speed with respect to the piston head, we need to consider the RPM as well.

Now that I am thinking about how the intake and compression cycles work, and the things about changing the timing of opening the intake/exhaust ports, I realized that I need to study more on that area before I can make any sense on this.

[Dimman]

Originally Posted by Want.FR-S

Just so that we can understand this together. The speed equation is with respective to the crank angle. It does not relate to the RPM. Therefore, to measure the *true* piston speed with respect to the piston head, we need to consider the RPM as well.

Now that I am thinking about how the intake and compression cycles work, and the things about changing the timing of opening the intake/exhaust ports, I realized that I need to study more on that area before I can make any sense on this.

What I'm looking at is the different ways that flow in a head is controlled. Most port work on a flow bench just chases a big cfm number since they just measure pressure differences on a cylinder head attached to a giant vacuum, but I want to look more closely at how velocity affects power. The nature of the piston motion and its velocity curve pulls in air, plus how a cam's profile affects the airflow and velocity.

What flow benches can't account for is how long it takes the air to start moving, plus how long it will continue, even after the piston stops 'pulling'. All rpm dependent, too.

I'm thinking that my old Supra could benefit from slightly smaller porting, but larger valves and longer duration cams. It has a longish 91mm stroke, so chasing big flow with rpm will be more stressful on the rods.