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Old 10-25-2012, 02:02 PM   #76
supershaft
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Quote:
Originally Posted by Voltaire View Post
Can you elaborate on what " roughly the same thing" means as $2000 would seem like a lot of coin.
Hauled ass is pretty subjective to me, what seems fast on the road is like slow motion on a track due to the width.
The Harley I pass on the track probably think I " haul ass".....whereas I think the Commando does....
Well, with the airheads I meant race and championship winning race bikes. Fast on the road versus the track? I have ridden way too many race bikes to be fooled by that. Besides, I friend of mine has done a 111 mph lap at The TT with a bone stock R1 engine and they are slow compared to BMW's. I suggest reading Smokey Yunick. That's pretty much what they do. Applied to airheads with the heads on the bike: They match up the top of the port with the bottom around the guide. That's removing a LOT of material. The port is kinda tear drop shaped for it in that plane. Epoxy first between two fins in case you go through. They straighten the bowl and deepen it AMAP. The ports are only D shaped right at the port's inside radius. Epoxy on the intake (I was told the trick is one glob and NOT layers!). The exhuast has to be welded up. The floors are raised a LOT more than BMW ever did after '88. Proud seats. 70% of the flow is a combo of the bowl, seats and valve cut. Valve diameter to seat inside radius and how they get there is a huge part of the game. That sums it up without writing a book. The mistake so many people make IMO is that they think of how the port flows. Wrong. It's not how the port flows (that's two strokes!); its all about how the it flows around the valve all the way around the valve's radius AMASP. What makes that happen best might surprise some people as far as the port goes.

supershaft screwed with this post 10-25-2012 at 02:19 PM
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Old 10-25-2012, 02:17 PM   #77
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Originally Posted by BOETJE View Post
But I am sure you know all this. I am also sure that you agree that the long article printed above about Mustang dyno's is ...err..... a bit dubious..
Also thank you. From the article above the vocabulary helped, not the content.
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Old 10-25-2012, 02:29 PM   #78
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+1 Inertia, water, eddie current. They are all different. Inertia around the longest? I don't think so. My dad's water brake dyno had a torque meter and a tach. That's it. No computer. It was the early seventies.

I have read form numerous sorces that the guys in England that invented the cross over found that location mattered a great deal. That's why that are where they are on most all pipes from way back them to 90's factory super bikes. Where the crossover or collector is makes all the difference.
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Old 10-25-2012, 07:20 PM   #79
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Torque and revs are the only way to measure HP, anything else is just bullshit, like that article.

The results you will get with any changes to a exhaust system will depend on what you start with.

Doug Hele started with a well designed production racing system, which under the regs at that time was allowed to be pretty free flowing.

And he found that with a well designed, free flowing system there was nothing to be gained with a crossover.

But that does not exclude the possibility that later bikes running under more restrictive regs will benefit from a crossover, in the same way that the heavier silenced road bikes did.

On the road bikes he was again starting from the optimum system - the crossover was fitted as a last resort when all else had failed.

And he found that, starting with a well designed system, the position or number of the crossovers made no difference.

The location on the Bonneville, close to the heads, was chosen as it was the easiest (cheapest) place to put it.

But again that does not preclude the possibility that on a less than optimum system the location or number of the crossovers may mask/correct deficiencies in the design, and make some some difference.

It isn't surprising that a trained and qualified engineer like Doug would get different results from others who have little or no formal training either in engineering or the methodology for test procedures, and it doesn't change the validity of either set of results.

But until I can read something written by a development engineer who has more runs on the board than Doug I will prefer the results of his experiments.
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Old 10-25-2012, 07:40 PM   #80
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Quote:
Originally Posted by Beemerboff View Post
Torque and revs are the only way to measure HP, anything else is just bullshit, like that article.

The results you will get with any changes to a exhaust system will depend on what you start with.

Doug Hele started with a well designed production racing system, which under the regs at that time was allowed to be pretty free flowing.

And he found that with a well designed, free flowing system there was nothing to be gained with a crossover.

But that does not exclude the possibility that later bikes running under more restrictive regs will benefit from a crossover, in the same way that the heavier silenced road bikes did.

On the road bikes he was again starting from the optimum system - the crossover was fitted as a last resort when all else had failed.

And he found that, starting with a well designed system, the position or number of the crossovers made no difference.

The location on the Bonneville, close to the heads, was chosen as it was the easiest (cheapest) place to put it.

But again that does not preclude the possibility that on a less than optimum system the location or number of the crossovers may mask/correct deficiencies in the design, and make some some difference.

It isn't surprising that a trained and qualified engineer like Doug would get different results from others who have little or no formal training either in engineering or the methodology for test procedures, and it doesn't change the validity of either set of results.

But until I can read something written by a development engineer who has more runs on the board than Doug I will prefer the results of his experiments.
Careful, your calling every inertia Dynojet out there BS. That's adds up top one tall pile!
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Old 10-25-2012, 08:15 PM   #81
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So do Dynojet inertial dynos actually measure horsepower rather than torque?

I thought they measured the acceleration of a roller of known mass. Since F=MA ( force is mass x acceleration) surely it's measuring a force: torque?
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Old 10-25-2012, 09:37 PM   #82
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Originally Posted by BOETJE View Post
Every dyno measures torque one way or another. Power is a mathematical product of torque and angular speed.
Your formula ( F= m x a) is for linear motion, for rotational motion it is
M= J x q where M is moment in N/m , J is inertia in kg m2 and q = angular acceleration in rad/ sec2.
So with a given inertia and a measured increase in rpm , you can calculate the Torque and thus the power . Thanks to modern data logging equipment it can be done so accurately that you can see the variation in torque during the whole combustion cycle if so desired....

OK thanks. but where did this idea that they measure HP and calculate torque from that come from?
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Old 10-25-2012, 10:48 PM   #83
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Originally Posted by chasbmw View Post
.....
DynoJets are inertia dynos, and have been around for years, much longer than any type of load cell dyno. Inertia dyno's work on the principle of the acceleration of a known mass over time. Their rollers are the known mass. Weighing in at over 2500lbs or so. Your car gets strapped down to the machine, and the dyno collects it's data. It is able to calculate horsepower by measuring the acceleration in rpm of the rollers in regards to RPM. This is why gearing can affect the dyno results, more on that in a bit. Now that the dyno has recorded the horsepower curve, it can take the integral of that curve and get the torque curve.....

from chas's link.

So that's BS yeah?
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Old 10-26-2012, 12:00 AM   #84
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Originally Posted by supershaft View Post
Careful, your calling every inertia Dynojet out there BS. That's adds up top one tall pile!
Yeah....but Doug Hele got that 500 Triumph to go around Daytona pretty quick.
If you have ever looked at a Triumph Daytona engine they are a pretty neat bit of engineering, light and quick.
The Trident was no slouch either.
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Old 10-26-2012, 12:13 AM   #85
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When I went to school

Quote:
Originally Posted by BOETJE View Post
Dunno...never heard that one, maybe from the internet ??
Torque was the ability to do work
Power was the rate at which work is done.

Accelerating a known mass to a set RPM was a measure of power.


It's been a long time since I went to school and the laws of the Universe & Physics have changed a couple of times since then.
I blame the Internet.

P.S. a horsepower was a measure of how many loads of coal could be hauled by a pit pony in a unit of time.
A steam engine was rated in horsepower as both a measure of performance and a total cost of ownership metric.
It is a real value in as much as a yard - the length of a mans arm from the fingertip to the nose - is
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Rucksta screwed with this post 10-26-2012 at 07:52 AM Reason: clarification
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Old 10-26-2012, 12:18 AM   #86
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Originally Posted by BOETJE View Post
Let's keep it civil , and say that I don't quite understand what he means.
But I am the first one to admit that I am not the sharpest knive in the drawer
I didn't mean to insult Chas. I meant that whoever wrote the article wasn't right.

Sorry if offence was taken.
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Old 10-26-2012, 12:10 PM   #87
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No offence taken PJ.

I'll take the bull by the horns and post some dyno charts soon
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Old 10-26-2012, 01:22 PM   #88
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As I understand it, an inertia dyno doesn't measure torque like a 'real' dyno. It's an accelerometer so torque and hp are caluculated from the rate of acceleration recorded with a computer. 'Real' dynos didn't need a computer. They use to just have a torque meter and a tach. You did the simple math yourself.

There are big differences in dynos but even bigger differences in how you can operate one.
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Old 10-26-2012, 01:33 PM   #89
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My 2 cents worth.

Here is my 2 cents worth regarding dynos. I realize nobody asked, but I'll say it anyway.

A dyno is a tool. If used correctly, it can be very useful.
It should only be used by somebody qualified, just like any other tool.
It should be used to compare before and after, nothing else. As such, make sure you use the same dyno and dyno operator.
Numbers by themselves don't mean much unless you're lookiong to brag.
For all I care you don't even need numbers other than an rpm scale.
All you need are the graphs for power and torque. Do the base run, make your changes, run again. Compare results

Let the flaming begin..........

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Old 10-26-2012, 08:32 PM   #90
supershaft
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Originally Posted by Kai Ju View Post
Here is my 2 cents worth regarding dynos. I realize nobody asked, but I'll say it anyway.

A dyno is a tool. If used correctly, it can be very useful.
It should only be used by somebody qualified, just like any other tool.
It should be used to compare before and after, nothing else. As such, make sure you use the same dyno and dyno operator.
Numbers by themselves don't mean much unless you're lookiong to brag.
For all I care you don't even need numbers other than an rpm scale.
All you need are the graphs for power and torque. Do the base run, make your changes, run again. Compare results

Let the flaming begin..........
Flaming? AFAIAC, we are on the SAME page. . . . Oh dear, that will get you flamed.
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