Airbox vs Pods vs Velocity Stacks

teazer said:
Absolutely correct but the biggest change was the use of LEDAR (Lincs Engine Development And Racing, IIRC) emulsion with taller spray bars to tilt the fuel slope. Check out a really late RD400 and you will see that the #284 series emulsion tubes look like a copy of the LEDAR parts with tall spray bars. That was an innovative solution combining two stroke spray bar technology onto a bleed, 4 stroke, style emulsion tube. But Leon Moss was a clever dude. RIP Leon.

Here's one site to start thinking..http://www.calsci.com/motorcycleinfo/Airboxes.html

http://www.tl1000s.info/Randys_TL1000S_Site/Airbox_design_v1_resonance.html

http://www.autospeed.com/cms/article.html?&title=Building-and-Testing-an-Airbox&A=113248
It had Ledar emulsion tubes fitted as well, it ran really sweet, though when I got my YPVS tuned by Stan Stephens I left the airbox on. It was just as fast as the LC had been with k&ns.
 
Brent said:
This is a silly statement. Why don't you now explain why the velocity stacks on the 650 are the shape they are if Honda were just throwing things together.

The velocity stacks are a part of the air box, not the air box. I didn't say that they didn't know anything about fluid dynamics or they didn't test and tune prototypes. I am saying that the engineering that went into a 1980 Honda air box is not equivalent to a 2015 Yamaha R1 air box.

Don't believe me?

Tell me that this was designed to optimized the acoustic resonance to increase volumetric efficiency, and not molded to fit the frame rails - this is the OP's OEM air box from a 1980 Cb650. Found the pic online.

s-l1600.jpg


honda-cb650-1980-usa-air-cleaner_bighu0134f0a17_5d24.gif


the outside two cylinders would have the resonance wave interrupted by the frame rails and there is a big hole in the center that would not have helped. There is also very little volume in the main chamber. not 100% sure, but I would guess that the other, back part of the air box was designed not for all out performance, but to accommodate a battery or tool box.

Hell, look at the Yamaha RD400 - a sporty bike for the time. being a 2 stroke, it didn't even have expansion chamber pipes from the factory.

YAMAHARD400-2454_1.jpg


Not saying that the Honda engineers were stone age, but the HP wars were not really hitting the CB650 at that time.
 
Well put Rus. As I mentioned earlier, I'm pretty sure these air box designed were not geared for performance as much as emissions and noise reduction. Back in the 80's the laws were getting stricter about noise reduction on motorcycles and companies could only reduce so much from the exhaust, so they had to take away from the intake noise as well.

Having said that, as we speak I am fiddling with the air box setup once more to see if I can perfect it more than the pods. I have a feeling I'll be able to. I'm determine to have a smooth performance bike, without destroying the insides. *cough cough* stacks
 
thwrightstuff said:
Well put Rus. As I mentioned earlier, I'm pretty sure these air box designed were not geared for performance as much as emissions and noise reduction. Back in the 80's the laws were getting stricter about noise reduction on motorcycles and companies could only reduce so much from the exhaust, so they had to take away from the intake noise as well.

Having said that, as we speak I am fiddling with the air box setup once more to see if I can perfect it more than the pods. I have a feeling I'll be able to. I'm determine to have a smooth performance bike, without destroying the insides. *cough cough* stacks

;)
 
I'm right in the middle of it so I'll get back to you later today to see if it helps. When all is said and done, i've found a dyno I can use for cheap, so I may take my bike there and try pods vs air box and see what the results yield. I'll post that information here if I do that.
 
Here's an update guys. I've spent the last few days tirelessly butt dynoing my bike and I've had some great success! Believe it or not, it was much easier than getting the pods to work. I have a little bit of minor tweaking left for tomorrow; my system is running ever so slightly lean and as a result, takes some time to warm up because it runs well.

Here's the info on my carbs now. Pilots went from 45 back down to 42, mains went from 142 down to 90 (stock) and my adjustable needle I set to the richest setting (may need to shim this tomorrow).

It's amazing how quickly one can achieve a proper tune when taking a systematic approach to these things.

My conclusion on this whole debate is this: if you are a regular street rider like me and don't do any racing, save for occasionally releasing the inner speed demon, air box is the way to go. Best all around performance and ease of tuning, as many others have already indicated. Pods look great and all and are easy to remove, but trying to account for the air turbulence is a nightmare. I can't speak from experience about stacks, but from what I've read and heard form others, keep those strictly as race mods only, in a situation where the engine is constantly being tuned, cleaned and tweaked.

I easily spent over a year and a half tweaking my K&N's trying to get them right and only ended up with maybe 70% of my bikes power. After two days of fiddling with the air box, I've gained back another 20% power, and after tomorrows tweaks, I fully expect to be back to full performance again. I hope this is beneficial to all other newbs out there wondering the same thing I was.

If I ever get the time and money to afford putting my bike on a dyno, I will post my results here with a fully breakdown of analysis.
 
Rather than relying on your butt dyno, why not just time yourself?

Find a nice long straight section of road, shift the bike into a high gear at low speed (don't bog the engine, though) and just crack the throttle. Shorter time between two points = better tune.
 
Hmm good idea, Sonreir, but wouldn't my time be different regardless of the trial? I'd have to make sure I am going the exact same speed in the same gear when I start, right?

Although, my butt dyno is pretty sensitive and tells me my whole system is running slightly lean. Usually, I can confirm that by pulling the choke slightly and seeing my bike revs higher and has more power when I do that. I wasn't able to make any progress on this yesterday due to other plans and i can't do any riding today since it's raining. :-[
 
o2 sensor per hole is the only way to be perfect, I wish a dyno was available here that was not so far or a pia to make use of... plug reading and ass dyno is really all thats left carb bikes are never gonna be like modern FI :-\
 
thwrightstuff said:
Hmm good idea, Sonreir, but wouldn't my time be different regardless of the trial? I'd have to make sure I am going the exact same speed in the same gear when I start, right?

Yup. That's the idea. Same gear, same speed, same stretch of road. It's one of the more accurate methods of tuning except a wideband O2 sensor.
 
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