DYNO QUESTION

[OB_BarryW.]

While dynos don't give the exact power value that a ram-air-assisted engine exhibits at speed, they are the most accurate tool we have to measure relative performance. I.e., if a mod. gives more power on a dyno, it'll give more power in the real world. What do you mean by bikes with airbox mods "losing some drive"? I'd guess that you've seen/experienced poor transient throttle response from bikes with full airbox mods. This would manifest itself as a stumble when the throttle is opened rapidly, especially from low engine speeds and is really more of a driveability issue than a power issue. It results in a rapid loss of port velocity when the throttle is opened quickly. A less restrictive airbox causes a larger initial drop in port velocity than a stock box. In fact, this phenomenon is what prompted Suzuki to incorporate the second set of butterflies found in the '00 GSXR 750 throttle bodies. By electronically controlling the butterflies they are able to provide the smooth transient throttle response required for roadracing by controling transient throttle port velocity. My understanding from reading the boards is that bikes with a full box mod make more power on the dyno and more speed at the dragstrip (real world power). It doesn't mean they could get around a road course faster, where predictable throttle response might allow faster laps than a more powerful engine with a "toggle switch" throttle. I'd suspect that most of this bad behavior could be compensated for with the correct FI remap.

Regarding your statement about modified boxes having lower velocity and hence lower flow, this is incorrect. In fact, the best that an airbox can do is completely stop the air, thus allowing it to reach its stagnation pressure, the highest pressure that can be achieved from an airstream flowing at a given velocity. Think of the airbox's role as being to raise the pressure of the available air to the engine (nature's turbo) and don't confuse inlet velocity in the airbox with port velocity, which is an entirely separate issue. I know this has gone long, but I've tried to be as brief as possible while still relaying the pertinent fluid dynamics involved.

 

[Guest]

I have a blue w/ Sato pipe, PC2(w/ 006 map, 0+1+1), full themotorhead airbox mod, dyno'ed at 160.6 bhp w/ air temp approx 100 degrees, humidity 100%.
I gained power all across w/ the full cut box, very happy with it.
My buddy on a 99 w/ Yosh pipe jumped me this weekend, I left him.

Kurt

 

[OB_THE MOTORHEAD]

ya get the map i sent ya lantabusa?

 

[Guest]

Naw, was it an attachment or something???
Haven't seen it...;(

 

[OB_BarryW.]

Motorhead:
What's the trick to entering your website? I'm hanging up on the intro page with the crosshairs and skull. Also, do you have any experience with the driveability of a 'Busa with the full box mod, pipe, and good remap? I like to ride the twisties in addition to the strip, but the abrupt off-on throttle performance of my stock '00 sucks IMO and I wouldn't want to make it worse in the canyons just for better et's. at the strip.

 

[Guest]

Barry, I did 636 turns in 22 miles w/ my rig, beatch comes out of corner exits in 3rd pulling like crazy. Come out in 2nd and it's a wheelie.

Kurt

 

[Guest]

gotit den, gonna try it now

 

[OB_BarryW.]

'Lanta_man,
Sounds like you've got some killer roads out there. I ride the Texas Hill Country, which has its good stuff. I guess I don't trust the Bridgestones enough or something, but compared to my D207GP-shod ZX9R (heavy '97 model), the Busa's off-on throttle transition seems abrupt enough to really upset the bike during mid-corner roll-ons. I do love this thing at the dragstrip though!

 

[OB_SUPERTUNER]

Back to original topic of the post...don't any of your shops have a kick-*** high volume fan to assist pressurizing the air box? On the flip side...make no mistake about it...those 4 injector bodies swallow up and draw in HUGE amounts of air! Dyno and real world are not too far apart in my experiences
with any pressurized air box motorcycle. We have a testing/tuning program in place that is real accurate in knowing that a customer is leaving running well in the real world. Knowing how to "interpret" the dyno data is just as important as having a dyno in the first place.

 

[OB_Bikenut]

You could always use 2 leaf blowers directed into the front ducts. Seems like the best idea I could think of besides owning your own wind tunnel. Has anyone tried this??

 

[Frank Adams]

Now that we're getting into the ram air subjects again might I add this...

To set your ram air bike up right by simulating air flow through the air box, it should be done by wheel spin of the rear tire.
If the rear tire is going 100mph then that same amount of air should be put into the air box.

But where is there a shop that can do this?

 

[GSX]

I am wanting to get opinions on dyno tuning. How can a bike that is tuned for a peak number on a dyno work well in the real world? I have always believed that the ram air bikes cannot be dialed in on a dyno. I have a 2000 busa that has never seen a dyno. With a 39 rear sprocket, I was able to pull 200.3 mph and still hit the rev limiter. Other mods include PC2 and an aibox mod (elimination of flapper valve). I have not cut my airbox out because the bikes that have had this mod lose some drive. Again these things have been proven in the "real world" and not on some dyno. A bigger hole in the airbox on the dyno will show a higher number because more air is getting to the engine at a stanstill. When the bike is moving at speed, this big hole slows down air velocity. The little stack in the stock airbox increases velocity, therefore the engine gets more air at speed. I want other people's opinion on this subject.