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Old 10-23-2012, 01:29 PM   #61
RGregor
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Does anyone know where the OP is?
He seems to be not too interested in the topic ...
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Old 10-23-2012, 01:31 PM   #62
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Originally Posted by RGregor View Post
Does anyone know where the OP is?
He seems to be not too interested in the topic ...
Since when did that stop everybody spouting off and enjoying themselves
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Old 10-23-2012, 04:41 PM   #63
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A stock euro RT will reach peak toque at just over 3000 revs..........doesn't feel like a rev monster to me
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Old 10-23-2012, 05:00 PM   #64
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Quote:
Originally Posted by chasbmw View Post
A stock euro RT will reach peak toque at just over 3000 revs..........doesn't feel like a rev monster to me
for the later ones yes, but up though '84 peak torque was at 5500rpm and peak horsepower is at ~7200 rpm. No, it's not an R1, but it's not a harley either. No they aren't "rev monsters" as you put it, but look at the stock gearing and keep in mind that these were designed for use on the autobahn. In order to get up to 80, 90, 100 mph you need to have the revs up into the 5500-7000 region. If they were designed to rev lower than that then they would be geared taller.
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Old 10-23-2012, 08:30 PM   #65
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3000 revs? Within a ftlb, my bike dynoed the peak torque at just over 3k again at a little over 4k, and then where I think the real peak is at around 5500k and that is with a sport cam and Dell's. Mainly because the throttle and the brake were hammered too hard IMO and suffered a giant oscillating dip of which it took up until the last peak to fully recover but that is another story. It all depends on how you load the engine. You can make a run and focus on getting a low rpm torque peak and then do another run and focus on a high peak hp. It all depends.

Rev monster. That I never said. No, that they are not. They don't make any power down low and they barely make more up on top but they all run strongest in the 4000 to 7000 rpm range depending. 60,s, 70's, 80's, and 90's. Sure, a lot of them are running out of steam big time at 6500rpm but it is still worth it to rev them higher than that for the next gear depending. Believe me, airheads are not torquey engines. There are lots of torquey engines out there to ride. Guzzi's and Commando's come to mind right off hand.
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Old 10-23-2012, 11:37 PM   #66
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I'd be interested in opinions on the head options, big port, big valve, D port. I'm thinking of swapping out the R90 heads for a set of R80 D port ones or 1977 40 mm inlet ones that I have in stock and seeing the difference at the track.
No plans to change the 336 cam as it flies up to the rev limited 7500 as quick as I can change the 1st 3 gears. 36mm Dells may be a bit small but at this stage happy to work with them.
I suspect the heads could benefit from some port work but I'd like to see some pictures or links.

The Guzzi's and Commandos pull away from me in 4th and 5th.....saying that they are pretty modified bikes and in a different league $$$$$ and rider wise
The 1975 Harley 1000 I can get past out of a corner and stay there.....the 1959 Harley less so.
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Old 10-23-2012, 11:45 PM   #67
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Originally Posted by supershaft View Post
It all depends on how you load the engine. You can make a run and focus on getting a low rpm torque peak and then do another run and focus on a high peak hp. It all depends.
Loading the engine means how to open the throttle?

My operator simply pulls it open within 1, maybe 2 seconds.
Comparing two consecutive runs results are nearly identical.
Not the best way to handle a Dellorto but it gives comparable data.
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Old 10-24-2012, 12:44 PM   #68
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Quote:
Originally Posted by Voltaire View Post
I'd be interested in opinions on the head options, big port, big valve, D port. I'm thinking of swapping out the R90 heads for a set of R80 D port ones or 1977 40 mm inlet ones that I have in stock and seeing the difference at the track.
No plans to change the 336 cam as it flies up to the rev limited 7500 as quick as I can change the 1st 3 gears. 36mm Dells may be a bit small but at this stage happy to work with them.
I suspect the heads could benefit from some port work but I'd like to see some pictures or links.

The Guzzi's and Commandos pull away from me in 4th and 5th.....saying that they are pretty modified bikes and in a different league $$$$$ and rider wise
The 1975 Harley 1000 I can get past out of a corner and stay there.....the 1959 Harley less so.
I have worked on heads from three different porters. They all do ruffly the same thing. D port? I call it a raised port floor but we are talking the same thing. Just about EVERYBODY is running D ports now. I very conservatively mimick what I have seen and it does help but the real answer is having them ported at a real port shop. I have helped with race bikes and the port job cost $2000 but it was worth it. The thing hauled ass afterwards! A few years back I worked on a Sportster that had Branch Flowmetrics flowed heads for $1500. The thing hauled ass! Unfortuneately, they don't do airheads anymore!

supershaft screwed with this post 10-24-2012 at 02:23 PM
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Old 10-24-2012, 12:54 PM   #69
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Quote:
Originally Posted by RGregor View Post
Loading the engine means how to open the throttle?

My operator simply pulls it open within 1, maybe 2 seconds.
Comparing two consecutive runs results are nearly identical.
Not the best way to handle a Dellorto but it gives comparable data.
Just for the sake of other readers, you are talking about an inertia dyno which really aren't even dyno's but that is another story. Most tuners I know use brake dyno's for a lot of good reasons. Big diff! I don't want to even get started with the rest of that post.
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Old 10-24-2012, 01:12 PM   #70
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Originally Posted by supershaft View Post
Just for the sake of other readers, you are talking about an inertia dyno which really aren't even dyno's but that is another story. Most tuners I know use brake dyno's for a lot of good reasons. Big diff! I don't want to even get started with the rest of that post.
Sorry, but being a non native speaker I'm not alway sure that I understand everything a 100%.
Thus the question.
And if the second part of my post does not make sense to you I'd be glad if you told me.
If you care for the sake of the other readers you could do that by PM.

Thank you.

EDIT:
To shorten the procedure:
Having a 7 years professional experience in that area I do know about the difference between inertia test stands and dynos, thank you.
But I didn't talk about the dyno, did I? Is my english really that bad that I don't know what I'm writing?

Just mentioned the procedure how to open the throttle.
As you wrote earlier it will affect measurement dramatically.
So if you want comparable results you have to do it the same way each time.
That's all I wanted to say.

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Old 10-25-2012, 03:28 AM   #71
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On Dynos, from another forum


Here's how I like to explain the difference. . .

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. Since the dyno’s power calculations are based on the acceleration of mass over time in regards to RPM, gearing is very important. Since a vehicle with a lower gear ratio can accelerate the mass to a higher speed using less engine RPM, it will show a higher horsepower number than a car with a higher gear ratio. If a car is able to accelerate the dyno’s rollers from 200rpm (roller) to 300rpm (roller)in 1500rpm (engine), then the dyno is going to record more power than a car that did that in 2000rpm (engine).

Now we go to Mustang dyno’s and other loaded dyno’s. Our Mustang MD-1100SE dyno’s rollers weigh 2560lbs. That is the actual mass of the rollers, much like the DynoJet. That’s about where all the similarities end. When we get a car on our dyno, we enter two constants for the dyno’s algorithms. One being the vehicle weight, the other being what’s called “Horsepower At 50mph”. This is a number that represents how much horsepower it takes for the vehicle to push the air to maintain 50mph. This is used as the aerodynamic force. Mustang dyno’s are also equipped with a eddy currant load cell. Think of a magnetic brake from a freight train. This magnetic brake can apply enough resistance to stall a big rig. Off one side of the eddy currant load cell, there is a cantilever with a 5volt reference load sensor (strain gage). As the rollers are spinning this load sensor is measuring the actual torque being applied. So as the rollers spin, the load sensor is measuring the force being applied, sending that information to the dyno computer, taking into account the two constants entered earlier, computing the amount of resistance needed to be applied to the rollers to load the car so that the force of the rollers resistance is as close to the force the car sees on the street. The dyno is then able to calculate the total force being applied to the rollers in torque, and then taking the derivative of that torque curve to arrive at the horsepower curve. Since torque is an actual force of nature, like gravity and electricity, it can be directly measured. Horsepower is an idea that was thought up by man, and cannot be directly measured, only calculated.

I like to state it like this. . . I start by asking how much your car weighs, lets say 3500lbs. Now you take your car and you make a make a WOT rip in your tallest non overdrive gear, how much mass is your engine working against? 3500lbs right? Now you strap your car on a DynoJet and you make a WOT in the same gear, how much mass is your engine working against? 2500lbs right? Now you strap your car on a Mustang dyno, how much mass is your engine working against? 2500lbs. Plus the resistance being applied by the eddy current generator. We’ve seen anywhere for 470lbs of resistance to over 700lbs of resistance as measured in PAU force in the data logs. So which one is more accurate? Well they their both accurate. If a DynoJet dyno says you made 460rwhp, then you made 460rwhp. If a Mustang dyno says you made 460rwhp, you also made 460rwhp. Now which one of those numbers best represents what your car is doing when its on the street. That’s a different question.

The most important thing to remember is that a dyno is a testing tool. If the numbers keep increasing, then you’re doing the right thing. We try to look over at NET gain, instead of Peak HP numbers. A 30rwhp increase is a 30rwhp increase regardless of what dyno it is on.

Now I can address how to calculate the difference between one type of dyno and another. Simply put, you can’t. Because Mustang dyno’s have so many more variables, it’s not a simple percentage difference. We’ve had cars that made 422rwhp on our Dyno, two days later make 458rwhp on a DynoJet the next day. We’ve also had cars that made 550rwhp on our dyno, make 650+rwhp on a DynoJet a few days later at another shops Dyno Day. For instance, my 2002 Z28 with a forged internal LS6 Heads/Cam/Intake, makes 460rwhp on our dyno. I thought that was a little low, since I’ve had cam only LS6 Z06 vettes make 450rwhp. So I overlaid the dyno graphs. Guess what, the PAU force for my car was almost 200lbs more than the C5Z06 that made 450rwhp with cam only. So I entered the weight and horsepower at 50 number for a C5Z06 and did another horsepower rip with my car. The only reason I did that was to compare Apples to Apples. This time my car made 490rwhp, no other changes. Now I don’t go around saying my car made 490rwhp, I say what it actually did with the correct information entered into the computer. It made 460rwhp. Now if I ever get a chance to take it on a DynoJet (which I plan to in the spring), I have no doubts it’ll be over 500rwhp. I know this based on airflow and fuel consumption on the data logs.

But since we’re asked this question constantly we're fairly conservative, and hence tell our customers that the difference is closer to 6-7%, but as you make more power, and the more your car weighs, the difference increases as well. You must remember, Dyno's regardless of the type are tuning tools, and are in no means meant to tell people how fast their car is. Now which one is more "real world" is a totally different question. I like to explain it like this..... If you drive your car in a situation in which you have no mass and you're in a vacuum, so basically if you do intergalactic racing in space, use a DynoJet. If your car sees gravity, and has an aerodynamic coefficient, and you race on a planet called Earth, then use a Mustang Dyno
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Old 10-25-2012, 04:06 AM   #72
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Quote:
Originally Posted by chasbmw View Post
On Dynos, from another forum

Here's how I like to explain the difference. . .
Hello Charles,
thanks for this post.
Most valuable for me is the vocabulary used.
So now it's clear what "load" means.

Regards, Rudi
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Old 10-25-2012, 05:19 AM   #73
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Rudi,

I'm struggling with this myself, but I think that what it means that rather than looking at spot figures, you should be looking at comparative charts from the same dyno, showing improvements in the power and torque curves
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Old 10-25-2012, 06:51 AM   #74
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No real brake measures HP - it measures torque, and this is used to calculate the HP.

But torque has to be measured at steady revs, so any machine which measures something at varying revs isn't measuring HP, it is just comparing it with an engine with known HP.

But this is schoolboy stuff - the first tuning book any schoolboy should read is Phil Irving's Tuning for SPEED, and he has all this, and more, covered with is usual combination of technical knowledge, writing ability, clarity of thought and expression.

The only authoritative work I have read on crossover pipes was written by Doug Hele, based on his experience with Triumph Bonnies.

Using a brake dynometer he found that the results were dependent on the amount of restriction in the silencer - on the, err, freer flowing production racers there was no gain, but on the silenced road bikes which lost 7 OR 8 HP half of that could be picked up with a crossover.

He found the position of the crossover made no difference whatsoever.

Despite being one of the worlds leading development engineers Doug was happy to admit that he had no idea why the bikes with the crossover made more power, and to his surprise that the location of the pipe made no difference to the power output.

But his job was done - with the "Cigar" silencers and the crossover pipe the road bikes made the same power as the proddie racers, and he was on to the next job.

I have tested my bikes, and cars, up the some test hill for years, and while it doesn't give me horsepower it tells me what direction I am going.

Sort of like a inertia dyno.

And FWIW my G/S gets up the hill as fast as my mates original one owner GSXR 750 R, notwithstanding that on an inertia dyno these things were tested to make around 86 rear wheel HP, at least 30 HP more than my G/S probably makes.
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Old 10-25-2012, 11:50 AM   #75
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Quote:
Originally Posted by supershaft View Post
I have worked on heads from three different porters. They all do ruffly the same thing. D port? I call it a raised port floor but we are talking the same thing. Just about EVERYBODY is running D ports now. I very conservatively mimick what I have seen and it does help but the real answer is having them ported at a real port shop. I have helped with race bikes and the port job cost $2000 but it was worth it. The thing hauled ass afterwards! A few years back I worked on a Sportster that had Branch Flowmetrics flowed heads for $1500. The thing hauled ass! Unfortuneately, they don't do airheads anymore!
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....
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