Air filter

[Squishy]

i was wondering about the "High Air Flow" myth too and made a test by my own using an AFR gauge!
i only tested it at IDLE-speed (cause i was boring to go for more), Pilot Screw at 2.75 OUT so here are the results:

IDLE with Stock Air Filter = 11.4:1  (less air than K&N)
IDLE with K&N SU-0008 = 11.6:1  
IDLE with EMPTY Air-Box = 11.8:1  (ofcaurse more air than K&N)

so K&N is REALLY flow more air than stock even at idle speed,i guess at high rpm will have alittle more difference!

thats what i thought!

My opinion is that since factory settings are LEAN at LOW (emission control) and VERY RICH at HIGH (power/top speed limit)  you only have enrich the pilot system (pilot screw 2-2.5 out) if you have stock bike! for aftermarket exhaust you propebly have to rejet by using either stock or K&N !

There was emission control in 1989 already? I would have thought the bandit 400 wasn't affected

[Squishy]

There was emission control in 1989 already? I would have thought the bandit 400 wasn't affected
of caurse it has! Pilot Screw is set at 1.5 like all the others!

I didn't know that. You're saying by simply turning pilot screw 2.5 out rather than stock it'll run better?
I have stock airbox but a open exhaust, needles set to +1 rich

[tubular]

i was wondering about the "High Air Flow" myth too and made a test by my own using an AFR gauge!
i only tested it at IDLE-speed (cause i was boring to go for more), Pilot Screw at 2.75 OUT so here are the results:

IDLE with Stock Air Filter = 11.4:1  (less air than K&N)
IDLE with K&N SU-0008 = 11.6:1  
IDLE with EMPTY Air-Box = 11.8:1  (ofcaurse more air than K&N)

so K&N is REALLY flow more air than stock even at idle speed,i guess at high rpm will have alittle more difference!

My opinion is that since factory settings are LEAN at LOW (emission control) and VERY RICH at HIGH (power/top speed limit & cool the engine)  you only have enrich the pilot system (pilot screw 2-2.5 out) if you have stock bike! for aftermarket exhaust you propebly have to rejet by using either stock or K&N !

SpeedKing,

little question since you seem to have digged in a bit into the B4 AFRs. What would be the target AFRs for a decent idle and WOT for a setup with aftermarket exhaust + after market airfilter (no airbox)?

The 11.something values you mention, are these considered good or can it go leaner and still idle well?
Regarding WOT would you say 12.5 is good enough or better off richer than this?

[tubular]

Thanks SpeedKing.

You got me covered on the WOT AFR but you kind of leave me hangin' on the idle AFR. What is your AFR at idle?
If it is in the area of 11.5 maybe it is a bit rich? Are you happy with it? Do you have any problems with plugs fouling?

Reason I am asking is because actually I do not use carbs anymore. I have converted to EFI (if interested you can read a summary of the project here: http://www.msruns.com/viewtopic.php?f=93&t=23094&sid=0fc49ad506e436edc7725e7741d313f6 ) and since the test run proved OK now I am trying to do some more serious job on tuning the fuel map (whether I succeed or not that is another story).

No PS, no MJ anymore... It's a whole different story now. Anyway, I got a rough table and it idles good at around 11.8 but I think it is too rich. What's your feeling about it?

PS:  We're both Greeks, but this subject maybe interesting to some other board readers as well, that's why I choose to contact you from here.

 

[tubular]

Now, that's a nice diagram. This is usefull guideline to anyone.

We're kind of getting off topic so I won't mess up this thread anymore.

[Chris H]

Most tuners and dyno shops dont tune to AF.
Most tuners work to best power curve and a little rich generally gives a smoother curve and feels better to ride.
E.G with correct AF for MJ you see a lot of engines showing a ragged curve at peak power, upping the MJ a couple of sizes usually helps smooth it out.

[andrewsw]

Reason I am asking is because actually I do not use carbs anymore. I have converted to EFI (if interested you can read a summary of the project here: http://www.msruns.com/viewtopic.php?f=93&t=23094&sid=0fc49ad506e436edc7725e7741d313f6 ) and since the test run proved OK now I am trying to do some more serious job on tuning the fuel map (whether I succeed or not that is another story).

Wow! What a cool project! Thanks for sharing that.

A

[canyonbreeze]

2 cents.  I wasted money on the K&N SU-0008, ran too lean and went back to a foam filter after several hundred miles of trying to tweak the adjustments. Will sell the K&N cheap if anyone wants it.

[Nickelodeon]

? for you Speedking, is it worth running "without cover" with a K&N for the extra 2.3% of flow at top end/high speed?

Does it actually significantly improve high end horsepower?

You don't happen to know off hand the difference between "without cover" and pod filters do you?

I'm just curious....I've got the standard Factory Pro jet kit and I run the K&N and it smoothed out the mid range and gave me some  better acceleration and slight higher top speed but it tops out @ around 115mph and I don't know if I'm wasting my time because of the American BST32's(vs 33's) or if there's more to get with more air flow(pod filters).

[Nickelodeon]

So where do you get velocity stacks made for the Bandit 400?

Are they sized for the 32 or 33mm carbs?

[tomacGTi]

Look in your airbox...

[Nickelodeon]

Ah....feeling a bit stupid now...probably won't be the last time...I never noticed the inners and have a K&N and have a FP 1.0 I installed on the carbs....lol