On Fri, 20 Jun 1997 16:22:44 -0500 (CDT) todd@nutria.nrlssc.navy.mil
(Todd Mullins) writes:
>Gary Burrell writes:
>
>> [ I wrote: ]
>
>> > One distinction which I feel needs to be made here, and for some
>of you
>> > it may fall into the realm of nitpicking, but I'll make it anyway:
>> > Brake performance has nothing to do with engine performance.
>Sure, it's
>>
>> > The only case in which an engine upgrade necessitates a brake
>upgrade is
>> > top speed. If you increase your top speed, then braking FROM THAT
>TOP
>> > SPEED will require more energy dissipation. But it takes a whole
>lot of
>> > horsepower to overcome the aerodynamics involved.
>> .... Much deleted
>> >
>> > Please note that this is explicitly NOT a suggestion to take a
>cavalier
>> > attitude regarding brake performance. You can never have too much
>> > brakes, no matter how powerful your engine is or how fast you go.
>My
>> > point is simply that there is no direct causal relationship
>between
>> > motor and brakes.
>> >
>> I beg to differ here. A higher performance car will get you to
>> a higher speed faster, thus giving you less time to brake, hence
>> the need for better brakes. Illistaration 2 cars at a stop light
>> 1 low power, 1 high power. Some distance down the road is a
>> obstruction which can be see from X yard away. Both cars leave
>> the light but don't have a chance to get to top speed before
>reaching
>> braking point, high power car would be going faster hence need
>better
>> brakes than low power car.
>
>You didn't read what I wrote (and you snipped the most important
>part).
>
>Fact: Higher speeds require the brakes to dissipate more energy than
> lower speeds.
>
>Fiction: More powerful engines force you to drive faster.
>
>Understand?
Immaterial;
Fiction- more powerful engines make cars faster
Fact - more powerful engines accerate cars quicker
difference being that speed, while dependent on availible power, is also
a function of gearing. Example (non LBC) My works Moto-crosser was
extremely modified for power. In fact the versions we rode put out almost
twice the power of the un-modified version. BUT the top speed was about
20 mph SLOWER. Because the purpose was to get there quick, not faster.
As to the need for better brakes with a modified engine, one must
consider the entire car when making modifications. The thing is a
system.
To look at it another way, suppose you modified and improved your brake
system. Does that then mean you then must drive at a higher rate simply
because of better brakes? Of course not. Then just because you have a
more powerful engine, you are not forced to drive fast. But the purpose
of power is to utilize the quickness, thus under those conditions where
it is appropiate to take that advantage, then it behooves you to have the
ability to DE-celerate in a similar manner.
>> > > 3) Competition Style exhaust with Long Center branch Header
>>
>> > Actually, the dual-carb factory exhaust manifold is pretty darned
>good.
>> > Does anybody have any hard numbers on the performance gain that a
>LCB
>> > header nets?
>> >
>> Yup, see below
>>
>> > > 5) Electronic Ignition kit. I used the crane/allison kit
>> > > but the new in the distribuiter type looks nice too.
>> > > (cost $100) I also used a sport coil ($40)
>> > > (More power to sparkplugs)
>> >
>> > All the electronic ignition really gives you is reliability and
>> > stability. It doesn't actually make any more power. The Sport
>Coil may
>> > allow you to open up your spark plug gap, which will make power,
>but not
>> > a whole lot (again - anybody have any hard data, so I can quit
>making
>> > such qualitative musings?).
>> >
>> Well no quanitiative data but qualitative data. Sport coil allows
>> higher voltage at plugs.
>
>Agreed.
>
>> Electronic Iginition also supplies more
>> power to plugs than points,
>
>Disagreed. Electronic Ignition doesn't send a damned thing to the
>spark
>plugs. Electronic Ignition ONLY tells the coil when to fire.
But electronic ignition are capable of firing a much more powerful coil
than is a point style system, especially at higher RPM's
>> Also at high RPM (5500) points suffer
>> from point bounce)
>
>Right; forgot about that one.
>
>> A quote from "Performance MGB" about the
>> Newtronic (Pirhana) Electronic Ignition: "We ran a rolling road
>> comparison test against conventional points. The resultant power
>> curves prove the Newtronic Ingintion system offered greater power"
>> My results on my car (qualitative) support this.
>
>There isn't enough information here to debate. And I still contend
>that
>any increases in power due to "hotter spark" come directly from the
>coil.
>
>> > > After you've done this you probably want to change the carb
>> > > needles on your SU's to something slightly richer
>> >
>> > I've never quite understood this thinking. If you need a richer
>> > mixture, why not simply turn the jet screw a few flats?
>>
>> This only serves to richen the mixture at Idle not accross the
>> entire power band.
>
>I'm sorry, but this is blatantly incorrect. Do you know how SUs work?
>
>And can anybody else tell me why engine modifications require a
>different needle?
The airflow rates into and/or out of the engine have changed, and not
necessarily in a linear manner.
>> O.K. Now for Some real # from MOSS UK "Performance MGB"
>>
>> Stage 1: K&N Filters, LCB Manifold
>>
>> And now the numbers measured on a dyno
>>
>> Stock: 74.1 bhp 105 ft/lbs
>> Stage 1: 80.7 bhp 110 ft/lbs
>>
>> My obsevations 9% more power just by adding K&N and LCB header
>
>Yes, but how much does the LCB header alone net you? K&Ns are
>routinely
>claimed to yield 3 to 5 horsepower; how much does that leave for the
>LCB
>header?
Math says that would be about 1-3 HP.
But that assumes the "claim" of K &N filters is correct. I havn't seen
that particular claim for a LBC filter. The one my #2 son installed on
his 275 HP 'vette does make a similar claim (5-8 HP).
>Todd Mullins
>Todd.Mullins@nrlssc.navy.mil On the lovely Mississippi (USA)
>Coast
>
>'74 MGB Tourer with unknown coil
>
>Atheist #685 "Whatever, baby."
Just to keep the pot boiling, I submit my tuppence wortth
Rick Morrison
72 MGBGT
74 Midget
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