Airbox versus Pods

[Nerobro]

If the airbox weren't such a steaming pile of crap on the GS550, I'd run an airbox.

If it weren't for the craptastic airbox on the GS550, it would make 57 horsepower. At least if the horsepower numbers for the GS650 are correct. That means despite getting lighter slide springs, the 550 is still down 15% on the horsepower it should be making with a proper airbox.

It's SO bad, they had to install restrictors on the center two carburators to make the outside carburators flow the same as the centers.

I'm very much a proponent of airboxes. In a large part, that's why I built the air filter I did. I haven't had the chance to tune the carbs properly for it, but the "filter" is essentially an airbox.

Proper carb tuning is highly dependant on smooth, and more importantly consistant airflow. Without an airbox, you're exposing your carbs to the wild and wooly world of the outside atmosphere. If you need more proof, racers used to remove airboxes. They don't anymore. and haven't since the 90's. The airboxes provide better perfomrance than pod, or open carburator intakes.

What I've figured out about airboxes... Bigger is better. More filter area is better. Calm, cool, consistant air is what your engine wants.

At least, that's what I think ;-)

 

[KEITH KRAUSE]

Pods vs airbox. It continues.
On our bikes, the CV's are more work to re-jet. They can be re-jetted with good results but you have to have patience sometimes. Most of the bad things you hear about re-jetting CV's is related to the owner having a lack of patience and/or other tuning issues/incorrect parts. The bike has to be ready to be re-jetted. CV's are sensitive and changing the flow will bring up issues you may not like. But if correctly re-jetted, the issues will be small and the pod filtered bike will make more power. The powerband may change but it will make more power.
The VM carbs are very easy to re-jet in my opinion. You may still have some minor issues but those are usually related to the cut-away and most of us just won't bother with that.
I've re-jetted a lot of bikes and when it's done correctly and the right parts/mods are matched, the bikes run faster with pods every time. You generally have a small loss of torque at lower rpm's/throttle openings but the overall power increases. My way of dealing with this is to suggest a larger piston kit and/or better cam timing. Matched with K&N pods and a good pipe, you'll have more power everywhere and still have great road manners/reliability.

 

[Slingshot383]

If you are running the CV carbs, then keep the airbox, you can modify it for more airflow, and use a K&N filter. If you are running smooth bores or flat slides, the pods are probably better. You can get some fiberglass sheetstock and make a large still air chamber/heatshield that goes in front of the carbs and bends back just below the carbs. Look at an old GSXR, and you'll see what I mean.

 

[humhead]

Sharpy
That's a nice looking setup. Do you know the part number of the K&N filter you're using?

Terry

 

[saaz]

I am with Keith here.

If you have CV carbs, be wary of getting rid of the airbox. With the slide carbs, as long as you free up the exhaust side and do some engine mods, pods make a difference. I run the K&N setup of two oval pods for the 4 carbs. I did run a K&N filter in the standard airbox without the lid on, and it ran quite ok. The main reason for the pods is that carb access is so much easier when you are playing with jetting.

With my mods (78 GS1000, 1080 kit, ported head, cams, 4-1), I have more power down low than standard, but it does not feel like it because above 3000rpm it starts to take off far more aggressively, and above 6500 strat to get serious. The cams, ported head and exhaust just do that.

But..airboxes can be good things. On my ST1100 it has really long intake runners, and the whole setup is tuned for torque from really low up to 8000rpm. If you start messing around with that sort of setup, you have bought the wrong bike lol!

 

[49er]

Thanks for your fed back guys. This subject really does compare with religion.

In many circumstances, I'm sure that the manufactureres of yesteryear didn't get it right with their carb configurations and airboxes. Even from model to model there would have been dogs, as pointed out by Nerobro.
I think that it's a pertinent point that racers are now retaining the manufacturer's airbox. Their decisions to do so in some instances are probably dictated by the need to abide by the racing class rules. However, that would not be the case at the drag strip.
Keith & Saaz, I respect your views on the pods. You do admit to loosing some bottom end performance at the expence of gaining top end. This is of course after you have increased the capacity, reground the cams to a higher spec, ported the head and run a good 4-1 exhaust system. I presume you increased the valve sizes as well as the porting.
Saaz, you didn't mention whether you retained your standard carbs or not.
By doing these mods, you have radically changed the engines harmonics and characteristis of the airflow. It would be very difficult to compare the standard airflow with the new flow patern in relation to torque paterns at various points in the rpm just by feel of the pants, except perhaps at higher rpms.
Have either of you tried a modified airbox setup, and done dyno tests to compare it with your pod setup. That would be the telling factor.

 

[morthrane]

I think that it's a pertinent point that racers are now retaining the manufacturer's airbox. Their decisions to do so in some instances are probably dictated by the need to abide by the racing class rules. However, that would not be the case at the drag strip.

Those airboxes are retained because they're a tuned instrument (helmholtz effect) that can be used to cover holes in the rev range or increase peak power.

 

[49er]

Those airboxes are retained because they're a tuned instrument (helmholtz effect) that can be used to cover holes in the rev range or increase peak power.

Your'e preaching to the converted. But there are still a lot of heathens out there.

 

[KEITH KRAUSE]

Keith & Saaz, I respect your views on the pods. You do admit to loosing some bottom end performance at the expence of gaining top end. This is of course after you have increased the capacity, reground the cams to a higher spec, ported the head and run a good 4-1 exhaust system. I presume you increased the valve sizes as well as the porting.

A little low end torque loss generally happens with pods/pipe but it's easy to get that back, and then some. Better cam timing of 106 or so will give you more low end grunt with just a little lost top end, which on the street is more usable power. A big bore kit will do it too. No need for porting, cams and other stuff to get back that power. Pods must be complimented with a good pipe. I see no sense in running just one or the other. Not for more power.
Bottom line, like 'em or not, any bike with quality K&N pods/pipe will out accelerate an airbox equipped bike, as long as all other tuning/engine condition is the same. The K&N's breath better. More air, more power.

 

[Guest]

Nothing scientific here, but when I ran against Tom_MLC's stock skunk vs my skunk with pods, pipe, and jet kit, I was beating him by over a second in the 1/4 mile on the DynoDrags. That is a significant increase. Reaction times were about the same.
I have not noticed any real significant loss of low end power. My bike seems to still pull as well or better with my mods.
The CV carbs may be a different beast, I don't know. My 1150 is all stock with a K&N filter inside a closed airbox. It seems to have leaned it out a bit, but I was running rich anyway since I'm at high altitude.

 

[ScottMc1100L]

The K&N's breath better. More air, more power.

...more dirt? I've heard (this is the trouble sometimes with these forums so many opinions becomes confusing) that K&N is better flowing primarily because of the lower level of filtration when compared to a stock filter. I'm not putting them down, just sort of wondering. True or not?! More opinions:-s ?

...I was beating him by over a second in the 1/4 mile on the DynoDrags. That is a significant increase....

A second is HUGE in the 1/4! Maybe swapping bikes for a run would yield different results?

 

[49er]

Scotty Mac
I agree with your views on the drag stip results. Changing bikes would show up weight differences, and variations in rider ability. If you are talking times in the 11-12sec range, over 1 second difference equates to a huge difference in trap speed, probably in the vicinity of 20 mph.
A friend of mine suggested that we change rally cars for a run at the drag strip. He managed to get within 0.35 of a second of my time and I beat his by 0. 08 of a second. These times were after two runs each. That is a test of freindship. The ability to change gears at the ideal rpm comes from the feel of maximum torque being reached at change. Dyno tests can confirm this point for the novice.
I guess my point is, you must compare apples with apples.

 

[Guest]

Scotty Mac
I agree with your views on the drag stip results. Changing bikes would show up weight differences, and variations in rider ability. If you are talking times in the 11-12sec range, over 1 second difference equates to a huge difference in trap speed, probably in the vicinity of 20 mph.

True. It equates to about 10% faster, which I think is what one should expect by adding pods, pipe, and jet kit to a stock bike.

 

[49er]

True. It equates to about 10% faster, which I think is what one should expect by adding pods, pipe, and jet kit to a stock bike.

Wow, 10%? They should be charging twice as much for those pods and jet kits. That's cheap horse power.

 

[KEITH KRAUSE]

Some K&N's and a quality pipe really open up our old bikes. Most bang for the buck by far.
Hard to say if the right name for our old airboxes isn't really "restrictor". Add a quality pipe to help things flow better both ways and you'll feel the difference. Just be sure to re-jet correctly.
Get the cams dialed in about 106-108 and your powerband is wide and the bike will be more fun to ride. I'd say a full second decrease in 1/4 mile acceleration time is spot on, from my seat of the pants experience and how these modded 750/1000/1100's run against other bikes with known quicker 1/4 mile times.

 

[Jethro]

Wow, 10%? They should be charging twice as much for those pods and jet kits. That's cheap horse power.

Wait until you pay $120 for 4 tint needles and 4 small machined pieces of brass with holes in them.

 

[tkent02]

Hey, you get a drill bit too!!!

Hey, you get a drill bit too!!!

Wait until you pay $120 for 4 tint needles and 4 small machined pieces of brass with holes in them.

But what you are paying for is the time and effort they spent and you don't have to. Spending a few hours wages is totally worthwhile if it knocks a number of hours or days off my tuning time, even more so if it prevents burning a valve along the way.

 

[lecroy]

Nothing scientific here, but when I ran against Tom_MLC's stock skunk vs my skunk with pods, pipe, and jet kit, I was beating him by over a second in the 1/4 mile on the DynoDrags. That is a significant increase.

I wonder what sort of accuracy it would have and if you could predict a real race with it. I would guess for a street bike that tire slip has a major impact on the E/T. It seems like a wheel dyno would not tell you much about the power of the two bikes. If two brand new bikes were put on one side by side and both had the same tire pressures, same rider, etc, I bet just how tight the two bikes were strapped down would have more than a 5% difference in the E/T. Reguardless, I bet it was fun.

 

[Guest]

It was fun, but I'm not sure how accurate it was either. Two of the same bikes might be fairly accurate, but I agree with the strapping down part. When I ran my 1150 against a modified VRod, my back tire was spinning and hopping.... I don't think they had it strapped down good enough. But I still beat him! \\/

 

[ScottMc1100L]

...but I still beat him!

renobruce love the pic and video . I does appear that your bike was bouncing more that the Hog was. Do you think that is suspension related or how it was tied down? Maybe the operator of the Dyno favors Harleys:-s ?

Was the end of the video cut off where you looked over to your oponent and said:

"And....I OWN it!! :razz: "
or
Not bad for a 21 year old bike eh? :-k "