$ per mile: high compression/high test vs. low compression/regular

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sorry, that's bullshit back at you. of course, you could always post a pic of your spectacular new invention, but you won't.

in the mean time, here's a "but the earth's not flat" concept that i think you'll have problems with - brakes don't work on "flow", they work on hydrostatic pressure transfer. since there's no "flow", there's no mechanism by which any "flap" can possibly be created.

whoever failed to teach you basic chemistry at high school really did you wrong.

no, it's not pH, it's electro-chemical electrode potential - you're dangling a metal probe into an electrolyte and measuring the potential difference for that metal relative to the [dissimilar] ground electrode.

this is usenet. "trusting" someone that tells you they have credentials rather than bothering to check facts and educate yourself is absolutely insane.

Reply to
jim beam
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valve timing doesn't affect head clearance or compression ratio.

[and strictly speaking, the valve timing is stepped, not variable.]
Reply to
jim beam

i'm sorry, but when you said "The octane requirement for an 8:1 engine is generally accepted to be about 92, and a 9:1 requires 96", i just couldn't restrain myself from pointing out that you were regurgitating someone else's underinformed bullshit.

Reply to
jim beam

A rubber flap acting as a check valve is hardly a new invention

That is ignorant nonsense. The amount of flow may be relatively small. For a 2 inch cylinder that moves 0.01" that translates into a couple inches of movement of the fluid through a hose with an 1/8" internal diameter. The fluid moves past loose piece of rubber but then can not return. It is actually just as common for a separated internal lining to block the flow in the opposite direction and that means it blocks the flow going to the wheel and prevents the brakes from being applied.

Reply to
jim

That's odd, because every car or truck I've ever owned gets at least

5% better mileage with premium fuel, which in most cases is giving equal value per mile, and without exception the car/truck always had a bit more top-end energy when needed, as well as a cleaner exhaust.

You can create low quality gas by mixing in 25% diesel with regular gas, and it'll still run but smoky and poorly unless you have a very high compression engine.

The ruse of 10% ethanol is what takes nearly 5% mileage away from each and every gallon. Very few stations will provide ethanol-free gasoline.

Reply to
Brad Guth

Actually I have heard of that being a possibility, but I've never seen it something like 1500 psi gets the fluid past a simple "flap" restriction (collapsed liner) but the roughly 7ps1 of the return fluid can't get past

Reply to
clare

Depends where you are. Here in Canada, Shell Premium is ethanol free.

Reply to
clare

There are no "flaps." The main reason for the argument here is using the word "flap." What happens is brake lines can get clogged. Not flapped. An inner liner that flapped would leave the outer hose casing subject to pressure that would swell it up and burst it. Here's what CAN happen, with photographic proof. Clogging.

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You can easily understand how 1500 psi can get through but 5 psi isn't enough to push back through. So a clogged brake hose can prevent brake retraction. I never ran across it myself, and don't think it's very common. Probably cheap ass ass hoses. Pretty easy to diagnose too, if your brake isn't retracting after you've made sure cylinders and slides are good. Just see if the brake retracts when you disconnect the hose. Now anybody who still wants to contend there are actual flaps acting as check valves in a brake hose - post a picture. That's when I'll believe it.

Reply to
Vic Smith

The FIRST and simplest test when a brake hangs is pop the bleeder screw. If the brake releases 90% chance you have a defective hose. If not you have a seized slider/pin or caliper piston.

And like I said - the "flap" is not really a flap - it is a detatched liner in the hose that "acts like a flap" - when the master cyl retracts causing low ressure on the "uphill" side and the liner collapses, restricting the fluid flow out of the caliper.

And interestingly, the MG pictures you reference show what COULD act as a "flap" as well, early in the deterioration. If the loose material jams up on the high pressure side it will move away from the orifice in the fitting under apply pressure, and flow back to plug the orifice on return. Every bit of what came out of those hoses came loose from the inner lining of the hose - and there is NO way to "prove" that none of those bits let go at one end first - causing a "flap"

I have personally cut open hoses that restricted return and found the inner liner loose, and deteriorated to the point the liner WAS perforated. Like the motorcycle line shown, the hose did bulge under full application pressure on that one - wasn't hard to know where to cut the hose to find the problem.

These were back in the seventies and early eighties. For a while parts quality was improving - making it less common to find these kinds of problems, but with all the Chinese parts on the market it's pretty safe to assume we will start to see more issues again.

Reply to
clare

Get yourself a copy of "Brake Systems: OEM and Racing Brake Technology" by Mike Mavrigian and Larry W. Carley -Published in 1996 and available from Penguin books. Check Page 15.

Also look at page 95 of "Automotive Brake Systems Classroom Manual by Cliff Owen. and Automotive Brake Systems in the "today's technician" series also by Clifton E. Owen.

Also look at page 142 of TechOne's Automotive brakes by Jack Erjavic.

Reply to
clare

looks like petroleum oil may have been mixed in with the brake fluid.

Here is another motorcycle example. In this case the brakes would not apply.

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He cut the hose open and described what he saw as:

"I decided to cut a cross section of the line to see what the internal condition was. It was sort of delaminating... not crumbling, but the cord and rubber were sort of coming apart and there was no discernable ID."

-jim

Reply to
jim

precisely. the commonest issue with the polymers use in brake hose is swelling. particularly when contaminated with hydrocarbons from things such as grease flung from a broken c.v. boot.

as the polymer swells, the layer inside the fiber reinforcement can't swell outwards so it presses inwards, constricting the bore. eventually it can close to the point where, as you're saying, high pressure fluid can get through in one direction, but the lower "let off" pressure of retraction can't.

indeed - there's no such thing as a "flap". it's just auto-tech legend invented [and apparently frequently regurgitated] to explain the phenomenon they observe in terms of behavior, ignorant of the actual mechanism behind it.

Reply to
jim beam

as a deliberately created device, not some magical self-assembling self-aligning self-calibrating spontaneity.

right. but that's not "flow" sufficient to rip and fold internal rubber.

fully separated pieces floating and coalescing in one place maybe, but like any debris blockage, they tend to constrict both ways, not just one.

as to "flap" theory, rubber flaws follow either a bending fatigue axis, i.e. perpendicular to its length, or they crack axial to the direction of the pre-cured polymer's extrusion. assuming an extreme case example were to occur where rubber cracks both axially and normally, a piece has to be detached from the embedded fiber reinforcement for sufficient length to be able to fold and block the bore, but at the same time, be secured such that folding can occur. that is acutely improbable.

that's just the material. for this "flap" be be actually folded back [presumably in the right direction], there also has to be a sufficient flow rate [note, "rate", not simply "flow"] sufficient to cause a turbulence differential that will force the "flap" away from its embedded fiber. because brakes are hydrostatic, again, this is just not possible because the "flow" volume is so minuscule - there is no differential possible without a high flow rate.

so, as said before, simple polymer swelling will restrict a hose core just fine. no magic, no need to invent "flaps" to explain.

Reply to
jim beam

so? do they have dissected hose pics showing these fantastic phenomena? or are they simply regurgitating this bizarre legend because they can't be bothered to think this through and actually research it themselves? [that's a rhetorical question]

one thing i've learned on usenet is that once one person makes some bizarre postulation that might potentially provide a superficial explanation to those who know no better, there's always someone else who will repeat it because they don't have the means by which to question or explain otherwise.

brake hose flaps and antifreeze dvm probing - absolutely my two favorite spectacular pieces of flat-earther nonsense - nonsense that some people will even put in print! it blows my mind.

Reply to
jim beam

I've seen it happen, but usually on very old cars. usually hoses will show external signs of needing to be replaced before getting to that point, or even if not, if you have a 20 year old vehicle with original hoses, proactive replacement might not be out of order.

I've heard the theory posited that also if the hoses are clamped off as in for a caliper replacement that that can cause this to happen sooner. I don't know if it's actually true or not because it's hard to get a large enough sample size for a real test, but it makes sense.

nate

Reply to
Nate Nagel

You don't even have to disconnect the hose, just loosen the bleeder.

nate

Reply to
Nate Nagel

no, you've seen constriction, never a "flap".

i did this on my 89 honda last year. frankly, it was a complete waste of money - the originals were in perfect condition. but my 88 toyota needed it badly - internal fibers were showing where the outer rubber had cracked so bad, it was starting to fall off.

if the rubber is already seriously degraded, it's possible that clamping can cause it to close or stick internally. but this hose should be replaced anyway.

generally speaking, clamping is perfectly safe. if any problem does result, someone didn't bother to do their homework on the state of the hose.

Reply to
jim beam

check.

precisely - rubber swelling and degradation constricts the core. [outside the fiber reinforcing, it can swell outwards, inside, it only go inwards.] there is no "flap".

this stuff doesn't happen on its own unless there's some highly unusual fault with the rubber compound used [some hoses are just disgustingly cheap]. all other cases are due to contamination of the fluid from inside, or the hose from the outside, and usually a hydrocarbon. when contaminated, the cross-linking of the rubber starts to break down, molecules are no longer bound as well so it then swells and becomes easily worn/fatigued.

Reply to
jim beam

Here is a picture showing a collapsed inner liner.

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Page 112, image 5.44 Automotive Chassis: Brakes Suspension and Steering, by Tim Gilles - Published by ThomasDelmar Learning. i n 2005.

Reply to
clare

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i can't see your cite - "unavailable or exceeded limit". but i presume it's this kind of diagram:

if so, it's an easy-to-grasp way of illustrating the /effect/ of a constricted hose, but like many things at the technician level, it's not accurate as to the facts of actual operation. just like flat earth theory will get the turnip truck to market, but won't ship turnip puree to japan. the average tech doesn't need to know exactly /how/ hose rubbers decompose or the exact nature of a constriction mechanism. all they need to know is that one-way constrictions can occur, so they can observe for symptoms and replace if found.

Reply to
jim beam

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