Happy Dyno?

[OB_DanaT]

Hi all,

Does anyone know why (poor calibration, faulty components, operator error, ect) that make a dyno either happy or sad?

I was wonder as I just had my 99 dyno'd for the first time. It made 149.3hp. The shop guy said that was about equal to what he has seen on other busas with slip-ons and a few more than he has seen on other stock busa. The one I saw run on the same dyno had 147hp with slip-ons. I talked to him a while and he told me that their dyno consistently made 4-8hp less than the other dynos around with the same bike.

Are the dyno jet dynos crap or what gives if there is this much variability?

-Dana

 

[OB_ZXALAN]

Hey I wonder the same, Last weekend I dynoed my Y2K with a RS3,semi-airbox mod,short stacks, 5,5,0, and 1800 miles and it only dynoed at 158 HP on a DJ 150 with SAE correction. I was hoping for around 165, boy was I shocked. But me weighing 160 in leathers my bike will do 145.60 mph at the track. Thats pretty decent trap speed for having ONLY 158 hp. I think dynos are B.S.!

 

[OB_QuickCurt]

I recently sold my DynoJet Dyno which I had mounted in an old Frito Lays 5th wheel trailer.

Most DJ Dynos automatically measure and adjust for Barometric pressure. The operator has to input the altitude above sea level.
Also some models require a manual web bulb temp test.

The corrected readings are readings adjusted to compensate for variations in the above parameters.

I used to start at 8:00am when it was cool and if I had a steady stream of bikes I could not often stop to do a wet bulb. The trailer would slowly heat up from the sun and from the bikes which caused minor changes in the output.

The DJ Dyno (150) uses a big old drum of a known weight. It simply measures how long it takes to accelerate this drum to various speeds. The drum is mounted on big ball bearing blocks. Differences in the drums weight and bearing friction cause different readings on different Dynos.

Another often overlooked factor was how you got the rear tire to hookup. Normally you can cinch the straps down just enough to stabilize the bike and get a good reading without wheelspin. (especially in the upper gears)But strap on a big power bike like the Hayabusa and you have to really pull the straps TIGHT or you get a lot of screeching and tire smoke. Just HOW TIGHT effects the reading by as much as 15hp.

We found this out by testing the same bike within 1/2 hour first using a stock tire and then a super sticky slick. With the slick we achieved the highest reading as wheel spin was not as much of a problem as with the street tire. Tire pressure makes a big difference as does the condition and tension of the chain.

Regarding tire abuse and wear on a Dyno. I personally ran my 1200 Daytona over 100 times and never hurt a tire. It makes nearly 140hp and I ran one tire 2500 hard street miles and about 30 Dyno runs with no damage.

Dynos are lie detectors. Either that $800 pipe works or it does NOT!! And the Dyno will tell the TRUTH. Thats why we call them "The Truth Booth"

My advice is stick with the same Dyno every time you test if you can. And try to do it on days that are similar weather wise using the same brand and grade of gasoline.

BTW: The bike with the slick and the street tire was a 1400cc GSXR1100 with a Jessie Gatlin motor, a turbo and squeeze! It made 397hp on the best run an scared EVERYBODY within 100 feet of the trailer. I was VERY puckered up!!

 

[OB_DanaT]

Curt,

How much are the used dynos going for nowadays?

-Dana

 

[OB_QuickCurt]

Dana,

I sold mine with a 1978 Chev Won ton Dually with a 454 and the complete trailer with built in Generator and a big bad blower for $15,000.

Dynos alone can be had for as little as $1500.00 and you then need to mount it and hook up a 486 or better computer.

Curt!

 

[OB_DanaT]

Damn,

I have been throwing pentiums away!!

I didn't know that a 486 was still useful. Had I know I would have saved the pallette of pentiums from the trash man.

-Dana

 

[OB_GSXRTURBO1]

Spread rear pads apart to eliminate pad drag

 

[Frank Adams]

QuickCurt<<We found this out by testing the same bike within 1/2 hour first using a stock tire and then a super sticky slick. With the slick we achieved the highest reading as wheel spin was not as much of a problem as with the street tire. Tire pressure makes a big difference as does the condition and tension of the chain.>>

DJ 150's have to be setup to the bike's specs before dynoing.(gearing, tire size ect ect)
The faster you spin a slick, the taller it will grow.
Thus, changing what you orginally set the dyno to in the begining.
It ends up showing more hp. I've seen them show as much as 22hp more then a stock tire!

But I do agree that tire pressure & chain tension make a big difference.

 

[OB_Cisco San Jose]

I think dyno's just give the basic baseline information for you to start before you do any changes.You should keep a record of the temperture on the day you start the dyno for your bike and as you install more go fast parts make sure you have the same type of temperture of the shop as the orginal test so that you can compair the difference if any when you modified the bike,make sure your chain is cleaned/oiled and adjusted to specs before every test.My bike 1999 did a 159rwhp on a Dyno jet 150,but to me that is not what I do my bragging about.It will end up being who is the best rider for that day and luck.So in the end don't be happy just with the horse power cause if you can't control the power you'll lose everytime or get hurt. Ride safe all.

 

[OB_bigabusa]

dynojet dyno's are best at back to back comparisions, hopefully on the same day.I've run them for 9 years. the biggest changes are caused by ( on street bikes)tyre pressures, chain friction,and sprocket wear. you must set up your barometric conditions to get good long term comparisons. on road racers i've seen huge differences from tyre compound to compound. I usually see 150 +-5 bhp on 'busa's. slip ons make 3-4 difference on peak, full systems as much 12bhp with a Yosh box adjustment. cut out airbox and BMC and remapp about 8bhp. Yosh cams 10bhp, bigbores depend on compression and size 13:1 1363cc about 15bhp.Add this lot up and your getting close to the magic 200bhp with some carefull setting up. ENJOY!!

 

[Guest]

There are lots of little things that could affect the HP reading.

When was the last time the dyno was calibrated?
Was it compensated for altitude, temp and barometric pressure?
Was your chain lubed? Someone here had a 3 hp difference.
How clean is the air filter? +approx 2
Rear wheel bolt torqued properly?
TPS calibrated?
Throttles synched?
Plug gaps?
Rear tire pressure?
Oil clean? We saw hp gains here with clean synthetic oil.
Oil level too high?
Rear brake dragging?
Quality and age of gas? Regular may be better if the bike is not timed for premium.

See what I mean.

 

[OB_GSXRTURBO1]

Cisco bring up a good point, use the dyno reading as a TOOL. Only change one thing at a time. Keep all else the same so you can see what is actually happening.