Speedo Error Myth

[Tufbusa]

I had the pleasure of spending a couple of hours with the big girl on the dyno last night. Must have done 25 pulls doing all sorts of exploring with this new and exciting unit from suzuki (Busa 08)

The one thing I did learn is the rumors I've heard of the mighty Busa's speedo having considerable errors at higher speed, may have no legs. After a few tests on the dyno with air pressure at 42psi, these rumors appear to be pure myth!

The dyno has a read out on the speed of the drum which is as accurate as a PoPo's radar gun. This is what I learned. At 60 mph the stock speedo is either nuts on or at least so close I could not physically see any difference. At 100 mph, it appeared the big beast was reading no more than 101 mph. At 160 mph the big girls speedo was reading about 162 mph.

The results of my experiment has me convinced the busa's speedo inaccruacy of some 10-12 mph is indeed a myth. While the busa is not deadly accruate at speed, it is indeed, very close with the bike in stock form and suzuki's recommended 42 psi in the rear tire.

 

[twotonevert]

 

[CDiPrecision]

I have a GPS that begs to differ with your findings...

 

[Tufbusa]

I have a GPS that begs to differ with your findings...

That's a ligidimate argument.

However, my own good judgment and common sense tells me the best choice would be the accuracy of the drum speed on a $60,000 dyno taking priority over a $400 GPS that does not make corrections for changes in elevations not changes in straight line speed?

Only my opinion! And, there could be a reason for your speedo being inaccurate and mine being very close to true speed. Is your bike old or new generation?

 

[Draco1340]

Back of the envelope calculation on a given tire is that you get about 2% change from a new tire to a highly used one. The difference from going from a Pirelli to a Shinko is almost 6% because of tire geometry. Surprised that your results were on the $.

 

[CDiPrecision]

The GPS if most likely accurate to within +- 1 MPH. The dyno numbers will change if the wheel slips, if theres any buildup on the wheel/roller, etc... I'm sure the math can be done on the Diameter of the drum VS RPM( Surface feet Per Minute).

We ran my bike at the track with the GPS(Zumo550) on it. The MPH on the ET slip VS the MPH on the GPS was within 2 at 150 MPH. Now if you stay in it after the lights then it wont read right, but we don't do that here.. The needle says alot higher than that I'm sure,lol.

That said, ill take the GPS numbers over the Dyno..

 

[Tybalt71]

I know the counter arguement would be that 400$ GPS is attached and works in partner with a multimillion dollar satalite$$$$$$$$$$$$$$$$ in space

 

[Commuta_Busa]

I know the counter arguement would be that 400$ GPS is attached and works in partner with a multimillion dollar satalite$$$$$$$$$$$$$$$$ in space

I was thinking the same thing... that doesn't include the launching costs or maintenace costs

GPS is pretty darn accurate. It does have a very small delay but other than that it's the tool of coice for accuracy all the way up the motorsports ladder.

I wonder what the dyno will read once you've worn the tire in a bit. the 42psi was that cold or hot? and at what tire temp.... Perhaps Suzuki did make the speedo more accurate than it was in the past but it's still gonna be off.

 

[Tybalt71]

I know the counter arguement would be that 400$ GPS is attached and works in partner with a multimillion dollar satalite$$$$$$$$$$$$$$$$ in space

 I was thinking the same thing... that doesn't include the launching costs or maintenace costs  

GPS is pretty darn accurate. It does have a very small delay but other than that it's the tool of coice for accuracy all the way up the motorsports ladder.

I wonder what the dyno will read once you've worn the tire in a bit. the 42psi was that cold or hot? and at what tire temp.... Perhaps Suzuki did make the speedo more accurate than it was in the past but it's still gonna be off.

im sure if you talk with the USA military, they are going to tell you its pretty darn accurate! lol so will ONSTAR, how else doyou think BATMAN gets Around with his GPS? huh??? lol

 

[Robot]

When I was flying Cessna's in Colorado in the early 90's the government dithered(diminished) GPS accuracy for civillians intentionally.

     We could see this inacuracy, in comparison to other navigational aids, (VOR's etc.), so it would not be used for civillian precision GPS approaches until FAA gave the go ahead.

     When Craig Button's A-10(with bombs) went missing April 2,1997. The Civil Air Patrol squadron I was flying with noticed GPS accuracy increase overnight. Military wanted that aircraft found ASAP.

    That was a long time ago GPS is bet your life on it accurate today. I dont think even a less exspensive unit would have much error. My money is on the GPS. Just my long winded 2cents.

P.S The A-10 crashed into a Colorado Mountain, I think the bombs are still missing, possibly dropped(unarmed) ,by him, near the New Mexico/Colorado border in rugged terrain.

 

[Yorad]

GPS wins this one. There are way too many variables on a dyno. Like someone else said; tire wear and brand matter, so does PSI. Think of how much HP varies from one dyno to the next (sometimes a lot) and you know there is some fudge factor involved in the math.

 

[Mr Bogus]

considering I have to trust my life to GPS when we are out fishing off the coast.. (some times 20M or more out) I have full faith in GPS..

That said it is possible to "fool" a GPS unit but it will rapidly update.. I can say my 06 is off by 10% average..


Also, I am sure that accuracy varies from bike to bike... so his speedo could be nuts on...

 

[thebbbusa]

What about the squish of the rear tire when sitting on the bike, maybe throws it off? Fact is, when I am in my car going 75 around here I'm keeping up. If I do 75 indicated, I'd better move to the right cause I'm going too slow!

My bet is the that the GPS is more accurate, and that the speedos are still off....at least on the 99-07 bikes.

 

[Commuta_Busa]

you could also view it like this... most of even the basic GPS units pickup multiple sat's.
so if you can retain all the same conditions and put the bike on multiple dyno's you could also get the average to be pretty accurate.

 

[Tufbusa]

I can see there is a fair amount of misconception concerning GPS. GPS stands for what? Yes, Global Positioning System, and yes it's dead on accurate if you want to know where you are at any given time. It is so accurate in fact, for a mere $25K spent on a reciever you can actually set property corners by GPS. If you are willing to spend $125K on a unit, you can get a unit for your bull dozer that will guide you (Nuts On)establishing position as well as elevations, for your road building operations without the use of surveyors. I don't think you'll find that sort of technology in any of your off the shelf GPS units designed for road use?

Speed calculation is a by product of GPS which is calculated by that little computerized gadget on your dash. Don't be fooled into thinking your Zumo GPS speed is always totally accurate? It is not!

 

[Mr Bogus]

That might mean the reading I got from my GPS3 unit was awry... it read 412 mph one day... (checked paint on hood, still intact so probably not a true reading)

 

[Tybalt71]

I can see there is a fair amount of misconception concerning GPS. GPS stands for what? Yes, Global Positioning System, and yes it's dead on accurate if you want to know where you are at any given time. It is so accurate in fact, for a mere $25K spent on a reciever you can actually set property corners by GPS. If you are willing to spend $125K on a unit, you can get a unit for your bull dozer that will guide you (Nuts On)establishing position as well as elevations, for your road building operations without the use of surveyors. I don't think you'll find that sort of technology in any of your off the shelf GPS units designed for road use?  

Speed calculation is a by product of GPS which is calculated by that little computerized gadget on your dash. Don't be fooled into thinking your Zumo GPS speed is always totally accurate? It is not!

Respectivey bro, tell that to a tomahawk cruise missel which depends on GPS for speed,distance,  target,obsticles,  elevations etc............. its dead on GPS, and its launched from miles away, even off shore in the ocean to land either surface to air, air to air etc.

 

[frisbee]

I wouldn't trust a dyno to tell me anything accuratly . To many variables . Not to mention that Sport Rider did a reveiw of all the major companies and the speedos are set back for import reasons . I don't remember what the reason was but all of the bikes were at least 10% off ( going 90 when 100 indicated ) May be they changed it in the last few years .

 

[UncleSteve]

I have used several Garmin GPS units. They all have been within one mph of the radar. Busa speedo is off 4mph to 7mph (depending on speed) when compared to the radar and GPS.
I have used more than one radar over the years,results are always the same, GPS within one MPH.
The 06 and 08 Busa's both have speedo issues. Neither is accurate. Always show 4-7 mph faster than actual speed. I would guess this is on purpose for liability reasons. For Suzuki, better for it to read faster than actual speed. Probably not their motive but warranty miles will click away faster.

 

[thebbbusa]

Funny how my Garmin almost perfectly matches the speed in my car +/- 1mph, no matter how fast I go, yet it consistently shows a slower speed than what's indicated on the bike.  I know for a fact that on MY bike, the speedo is off.

You really think someone would go thru the trouble to install a speedohealer...thousands of people would all buy said speedo healer to get the speedo right if it wasn't wrong?