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Bonneville speed trials

Started by justbummin1, October 12, 2011, 11:04:25 AM

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justbummin1

After having a terrible week top speed wise at the Bub speed trials at Bonneville I found you guys on line in my search for knowledge and answers.

So here's the short version of the back story. We bought a 2007 GS-500F and decided to run in the production class this year at Bonneville (we are also running a ZX10 and a Hayabusa in the stock production classes). The record is 112 and change so after getting all the safety requirements done, carb work done and a couple dyno runs to prove that this record was a joke and didn't understand why it was so low and that we would be leaving with an new record!!!

WRONG!!! Reality is a Buddha Loves You and this is way harder then we ever thought it would be. We got in 12 runs over the 5 days with a blazing 104.905 as our fastest of the week. We made 2 front sprocket and 3 rear sprocket changes, 5th gear passes, 6th gear passes and most all of the runs where in the 100 to 102 mph range. We where having a fuel feed problem with the stock fuel petcock (now after the fact I see here that this is a common issue with the GS500's) so I don't know if on the extended full throttle run we where leaning out the motor and just starving it??? We did a plug check at the end of a run and they looked good so i think we where jetted right for the altitude but I am lost on why that was as much speed as we could get???

Any suggestions on what changes we need to start making for next year would be much appreciated but being in the production/production class we cant make any real changes from "factory stock"

Thanks, Rob

BTW: be gentle with me I'm new here!

burning1

You're asking an interesting question... Will do a little reading/thinking and get back to you. Need to look into the speed week rules.

Off the top of my head though, 112MPH is pretty close to the maximum achievable speed of the GS500 on pavement... It's my understanding that you don't normally see a vehicle's maximum road speed on the salts, is that correct?

I can say, that on the local road race circuit, my maximum GPS confirmed speed was ~102MPH down the .4 mile front straight section of track (production bike, 100% stock intake, engine, exhaust, jetting.) I know the bike can do better than that, but an additional 12 MPH might be too much to ask, even with prod legal mods.

The Buddha

Sorry to break it to ya ... but ... that's the rules, I dont make them, I only follow them ... but its OK you're new we can give you some slack right guys and gals ... So on behalf of the whole world of gstwin ... Pics ... or it didn't happen.

Cool.
Buddha.
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I run a business based on other people's junk.
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justbummin1

burning 1 - You are correct about losing top speed on the salt. I think most people figure about 2 to 5% slip depending on salt conditions which adds up quicker then you think. My dad rode the bike this year (72 year old guys are not real flexible to get down on the tank right) and the plan is for my son to run it next year so we should pick up a little there since he is smaller and can get tucked up better to get out of the air. When you are only working with 40 horse power wind resistance really counts.

Buddha - If I can figure out how I will get some pictures up tomorrow.

Currently we are trying to find out how much work we can do inside the motor and keep it legal. Don't know if they only check bore and stroke or if they do compression also??? Since you guys are the experts would polishing the intake/exhaust and shaving the head to bump up the compression get me any gain or would i just be pissing money away?

Rob

burning1

Knowing what you can do legally would be a huge help. I tried to find the rules for your class, but it looks like I'd have to order the rulebook. If you happen to know of an online copy, I'll review.

The GS500 is a pretty low compression engine; 9:1 or so. Machining the heads/block will give you some power. An aftermarket exhaust (~$200-$300,) intake, jetting, cams, etc. could help a lot as well, especially if you port. But it depends on how much you're willing to put into the engine, and what the rules permit.

Stock, the GS500 puts out about 40 horsepower or so, at the rear wheel. I've seen race bikes that can put out 60 or so with the stock bore/stroke. Most of those engines have:

- Airbox removed, pods or intake trumpets
- Cams, shim-over-bucket, springs, etc.
- Full exhaust
- High comp pistons
- Rebalanced, lightened crank
- Rejet and/or flat slide carbs
- Balancer shaft removal

Cost on all that is probably ~$2000.

The Buddha

I dont think you can touch anythign past the exhaust and jetting for it to stay stock ... but you should read the rules carefully.

BTW I have heard the pipes being 2 into 2 help ... but worth the weight penalty ... no idea ...

Now, where are those GS'es that go 130 clicks that show up time to time on craigslist when you need em.

Cool.
Buddha.
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I run a business based on other people's junk.
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burning1

Weight shouldn't really be much of an issue for top speed runs. If you add 100lbs to the bike (without changing the aerodynamics) the bike will still reach top speed. So, anything that can add horsepower without affecting CdA will help.

Production rules can be strange, for example, the AFM allows a surprising amount of modification to a production bike. So, I'm not going to assume anything. :)

lucky4034

Now this is a badass thread!!  I hope you keep us updated with your progress....  My grandfather was part of the design crew for Donald Campbell's BlueBird CN7 that ran at Bonneville... I love reading about this stuff.

Own:
'09 Suzuki GS500F
'05 Kawasaki Ninja 250R

Hope to own one day:
'11 Honda CBR600RR
'87-'92  Yamaha YSR50
'90-'93 CBR 250RR
...and counting

guilfordin

Regarding  this thread, here are a few comments.  First off, you're not going to get any slippage with a stock GS.  The reason you can't pull like you do on asphalt is primarily due to the track elevation.  At 4216 feet above sea level, you're going to give up oxygen molecules.  On average, you can figure a 10% loss in HP  for every 5000 feet of elevation.  If the stock bike makes 40 HP at sea level, subtract roughly 8% for the loss of air, and you lose about 3.2 HP.  Also, the salt has a higher coefficient of friction and you can lose 3-5% of your top speed due to this loss.
And someone did mention, that the addtional weight should not make a difference, and that is wholly correct.  Weight is a consideration in acceleration only.  The Arrow Racing teams 500 cc streamliner, weighs in at 1200 pounds !  Slippage doesn't become an issue for motorcycles, unless you are making very high HP to weight ratios.  Out there, gravity pushing down is your friend.

Gary

twinrat

a suggestion, on salt or sand for records you need narrow tyres that are smooth and high pressure to keep as little of your tyre in contact  with the surface  as it is all friction.Also a hard tyre not a sticky one. cheer's

guilfordin

For Bonneville you are required to run tires that meet the rules in the handbook.  You cannot run any style of square edged tires, because they groove the salt.  I run a 6" wide road race slick, no tread, as do most other bikes.  There is a real catch 22 with the salt, because you are trying to lower rolling friction, but in so doing, you are losing traction.  Your stock or modified normally aspirated GS would not have a problem with traction,  I would try and find a 4" rounded, worn slick, and you should pick up a few MPH over any street or off road tire.

twocool

#11
Wow...really cool!

I can see that 112 mph is a tough record to beat!  And not as easy as it may at first seem...

I did some rough math calculations and can see why.........

THe way I see it, the two main obstacles to attaining that speed, are Horsepower and Drag.

On the H.P. side, you are fighting a loosing battle...because the formula for HP vs speed says you need 8 times the HP to go only twice as fast...

So some quick numbers...

Say the GS is producing 40HP to ground at the rear wheel
And say you're getting a top speed of 100 MPH


If you desire to increase to  110 MPH...you need to produce 53 HP....thats about a 32%increase in HP just to go 10 MPH faster.........

It takes a lot of engine tuning to do that...probably not even close to realistic......


I figure all the tuning you could do might give 2 to 5 more HP at best! (and maybe 1 MPH)

Now lets look at drag...

Using the drag, HP, speed formula......A 40 HP bike going at 100 mph is pushing about 150 lbs of drag.......that's a lot!!   Bikes have terrible shape for aerodynamic drag...also rider is not good shape either...

In order to go 112 mph.....(with same 40 HP) you must reduce the drag to 133 lbs.......

This is not all that much ...in fact only 11% reduction.......

To me it would be far easier to accomplish an 11% reduction in drag, that to get a 32% increase in HP........

Some say the fairing on the GS500F actually creates more drag than not having a fairing!

The fairing has a rather blunt rear edge shape which would create lots of drag...

Of course there are a million other things creating drag on this bike...
Riding position, shape of rider's helmet, legs.. feet.. knees.. sticking out...cooling drag by the scoops in the fairing around the engine...shape of wheels, rims, spokes, tires..exhaust sticking out, mirrors, turnsignals, top edge of windshield...interferance from one shape into another...etc.....

I've done a bit of work on airplane drag reduction...on a fast airplane even one little radio antenna can result in a loss of two or three MPH in speed.....proper wheel covers can increase speed by 5 MPH.....Design of the air intake ducts and engine air cooling ducts and cooling air exit...all can add several MPH.....The sailplanes we fly will produce only about 50 or 60 lbs of drag at 100 MPH.......because they are perfectly smooth!

I am not sure how the Bonneville rules would allow "modifications" to the fairings, lights etc...or if you can wear streamlined helmets and clothing like speed skiers and bicyclists do???

But reducing drag in the answer IMHO, this will give big results....10 MPH or more...engine tuning will only come into play if you need that extra tenth of a MPH or so to break the record...

Cookie















burning1

I can say from personal experience, that the GS500 will easily do 100MPH on good pavement in stock trim without a long run-up - I've confirmed that using a GPS data logger on my track bike. Faster is absolutely possible - I was limited by the amount of pavement rather than the absolute top speed of the bike - and remember, I ran low tire pressures, for increased traction at the cost of increased rolling inertia. I'd estimate that 110 is possible, bone stock. The quoted top speed seems reasonable.

There are some major aerodynamic improvements possible that are production legal... Excellent tuck position, leathers with a good speed hump will help (the leathers give a shape similar to a bicycle aero helmet.) If after-market clip ons are legal, I'd use them to help improve BP. Lower, narrower clip ons will help get the elbows out of the wind.

twocool

Quote from: burning1 on December 24, 2011, 07:10:12 PM
I can say from personal experience, that the GS500 will easily do 100MPH on good pavement in stock trim without a long run-up - I've confirmed that using a GPS data logger on my track bike. Faster is absolutely possible - I was limited by the amount of pavement rather than the absolute top speed of the bike - and remember, I ran low tire pressures, for increased traction at the cost of increased rolling inertia. I'd estimate that 110 is possible, bone stock. The quoted top speed seems reasonable.

There are some major aerodynamic improvements possible that are production legal... Excellent tuck position, leathers with a good speed hump will help (the leathers give a shape similar to a bicycle aero helmet.) If after-market clip ons are legal, I'd use them to help improve BP. Lower, narrower clip ons will help get the elbows out of the wind.

It's a long way from 100 MPH to 112 MPH...with somewhat limited HP.....as our Bonneville racers found out.

As mentioned earlier a couple of problems with Bonneville is the high altitude=less HP

And the rolling resistance of salt seems a bit higher than that of (tarmac) pavement.

Again, just my opinion, but it seems easier to get more speed by reducing drag, that it is to increase HP, especially with the limitations when the engine is supposed to be "production" .

I could  see streamlining the rider by clothing and riding position, big difference in drag and could easily add a couple of MPH..

I see Bonneville as a nice "standard" however...as it is level, and the runs go both ways accounting somewhat for wind....

(actaully) the average of a downwind run and an upwind run will be slower than a run with no wind...




burning1

Agreed, and good reminder about the altitude difference.

twocool

Quote from: burning1 on December 26, 2011, 11:39:04 PM
Agreed, and good reminder about the altitude difference.

Just for the fun of it...Is there a place where you could run full out, and have a longer straight than the track?  (run tires hard)....

(I'm a wimp and never went more than 80 MPH on the GS!)

Cookie


burning1

Might be able to find an event at a local airport. Texas mile perhaps? Personally, most of my top-speed runs have been on the local freeway.  :oops:

twocool

Quote from: burning1 on December 27, 2011, 06:34:27 PM
Might be able to find an event at a local airport. Texas mile perhaps? Personally, most of my top-speed runs have been on the local freeway.  :oops:

Guys often run at airports around here.   The airport where I work, we often run cars or bikes....but the runway and parallel taxiway are only 3200' long.....so just when you really start getting up to speed, its time to figure out how to slow down.  (there is no over run area, just a cornfield!) So it's more like 1/4 mile speed runs.

A couple of years back the airport owner ran an event for his car club.  The deal is they brought out all kinds of exotic cars, Ferraris, Cobras and the like.  For a charity donation of like $200 you got to make like three runs in the car of your choice.  It was up and down the runway a couple times (drag race) and around the perimiter road, and then circles around a skid pad.   Kinda cool!

The other local airport runs Drag races on sunday mornings for the Corvette club.  Also "motorcycle stunt riding school" a couple of times a year.  This place is like a three ring circus.  All At the same time I've seen:  Airplanes, ultralights, skydiving, drag racing, model RC planes and motorcycles!!!

The "big Boys" of motorcycles have a stretch of RT 80 out west of here where the cops do not enforce speed.   The only way to get a ticket is if somebody complains to the cops, then they come out, otherwise it's a free for all.  One friend of mine claims 218 MPH (on gps because speedo doesn't go that high) on this stretch, on a Ninja 1400 (modified)....

The trouble with trying to determine absolute top speed on the highway is that it is not a controlled environment...always some wind...always up or down hill a bit...


Cookie






guilfordin

Not sure if any of you out there are aware that starting on April 28 & 29, the East Coast Timing Association (ECTA) will be running their events at Wilmington Ohio, between Cincinnati and Columbus.  Maxton is shut down permantly.  It would be a great opportunity to bring your GS's and get some idea of what LSR Land Speed Racing is all about. 
Membership, Rule books and registration can be found online at:  ecta-lsr.com


justbummin1

OK, here is where we are at today. Talked to AMA/Bub and pretty much as long as we don't go over 500 cc, they don't care what we do inside the motor. So it is at a shop in Minnesota now getting some love (Mill the head to increase compression, new cams, some carb work, polish all passage ways etc, rework the exhaust pipe to let it flow better as well ). We have lowered the bike 3 inches and had padding taken out of the seat to help to punch a smaller hole in the air, New ceramic bearings front and rear, replace fuel petcock and lines (as stated earlier I think we where having issues with fuel).  The hope is all of these little changes will add up and get us the extra 8 miles and hour plus.

Any other thoughts on changes that can me made I am all ears!!!

Thanks, Rob

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