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I was at a bike event in Great Yarmouth today and popped my bike on a dyno. I was curious to know how my bike was running as it was first registered 20 years ago in March. This is a late carb (1999) and the only change that might affect power was Micron end cans.
https://youtu.be/QtE-ihwd8PA

I've included a photo of the printed dyno results right at the end if you want to jump right to it.
 

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Fueling was pretty good a little lean from 60 to 90 but not bad enough to hurt anything. If you could drop a little more in there to get it to 12.5 it'll probably pull a little harder in that zone.
 

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It'd be in the needle shape to get the fuel right. You could send a pic to dynojet and see what they say.
 

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I haven't had the head off my bird to see how they are constructed, but knowing engines and valve trains, it looked like the top end might just not quite be at the peak. On the deceleration it was blowing a puff of blue. Made me think valve guides will need some attention soon. If you don't really push the bike regularly, though, it wasn't really bad, but it might account for a couple of horses along the way.
 

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Numbers are right on and A/F looks surprisingly good. Either the carbs were better tuned for A/F when new or there is a jet kit installed. The FI models are known to be way rich from the factory. HP is right on too. Stock birds typically would run a bit over 130 HP and a bit over 80 FtLbs stock. Know what gear the pull was in to hit 166 MPH?
 

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How much HP could be added on the premise of positive airbox pressure that happens on actual road?
 

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How much HP could be added on the premise of positive airbox pressure that happens on actual road?
The faster you go the better it gets. A test was done by Sport Rider once, Oct '99, I'm missing part 2 where they show hp gains, but the XX ram air works very well, building positive pressure in the air box from about 90 mph and peaking at 28mb, the highest in the test equalled by the Kawi ZX9.

I believe the net result is about a 5% gain in rwhp.
The Hayabusa in comparison makes only 16mb of pressure but fluctuates heavily getting there and is going a lot faster before making any, where the XX is smooth (as are the Kawi's, who have been at it longer).
I'm gonna look for part 2.
 

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Partsguy, do the efi models run a true ram air system? On my carb the passageways from the snouts on the front of the bike to the air box seem intentionally baffled to allow the air box draw air that is not turbulent.
I remeber the dyno tuner saying her carbs wont run optimally if they're removed.

OP, good results on the dyno there imo. With carbs it's not as easy to hit the line all the way across as with a pcommander eh.
I got lucky with my exh system, didn't need drastic changes after dyno time.
 

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Thesa
Yes it's a true ram air. The ducts are chambered to help amplify the effect. They run down either side and slip into the ports on the air box.
 

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Hey, thats weird because on my carby the inlets of the airbox are not mated to that of the front of the bike. I can't understand how that design can lead to the airbox pressurising in any meaningful manner. It seems designed to prevent that very thing? Seems to be more of a cold air feed.
Maybe my understanding of ram air is different to what it actually is?
Worked on a zx12r before and i can probably imagine that airbox is tuned for induction. Crazy thing howled/resoanted below you!
 

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Partsguy, do the efi models run a true ram air system? On my carb the passageways from the snouts on the front of the bike to the air box seem intentionally baffled to allow the air box draw air that is not turbulent.
I remeber the dyno tuner saying her carbs wont run optimally if they're removed.
It also helps the carb models run cooler by directing air at the engine.

I cannot find Nov '99 Sport Rider anywhere, anybody got old bike mags stashed away?
 

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Hey, thats weird because on my carby the inlets of the airbox are not mated to that of the front of the bike. I can't understand how that design can lead to the airbox pressurising in any meaningful manner. It seems designed to prevent that very thing? Seems to be more of a cold air feed.
Maybe my understanding of ram air is different to what it actually is?
the carb model is basically just sucking in air at the openings but it needs the white plastic deflectors to make proper air flow in the air box, without them the bike will stutter from mid rpm up.
Ram air only works if its drawing in more air than the engine can gulp down and making positive pressure in the air box, so it has to be an effective design. And that's about all I know,lol.
 

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Yep, I have an 05 EFI and it has the ram air ducts all the way into the airbox...... makes removing the airbox that little bit more tricky ;).

Nice to know what a 20yo BB pumps out...... it's a well put together motor so it probably hasn't lost much over the years.

:D
 
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