secondary flies... what?

ok guys, been looking more into the design of of my velocity stacks and thought i would try removing the secondary flies for an even more efficient design (should have the first couple ready by this coming week).

At the time i had the moto flies and wandered whether removing them would damage throttle response (could go into why but cant be bothered at the moment) but it didnt at all. In fact i think it may have crispened the response. So the moto flies are staying out (not that there is anything wrong with them... in fact they are amazing compared to the stock ones) due to the advantages are to come.

Now i am able to make a more efficient design for the dual velocity stacks.

Let me make this clear though (as i a not trying to slag any of aarons work as i know we would be lost without him)... the moto flies are better than the stock ones and will smooth out the throttle response drastically. Although i do believe that you dont need any secondary flies (after a back to back ride).

Well MrZ you could have let me know this about 2 weeks ago DOH!!

So - removing the secondariy flies entirely smooths fuelling and gives a crsiper throttle response?

Is this only with the MH airbox, or only with new velocity stacks, or just in general?

Dutch,

There was some debate a few years ago about running with and without flies on the Superduke. I don’t recall there being a conclusive answer. I did aim to get a conclusive answer via dyno with and without the flies on my bike.

Any road up (Sorry, I’m from Yorkshire), I took the flies out and felt by the seat of pants that I had a crisper motor. (Of course my pants may need recalibrating?). I never did get it on the dyno again

Having ridden for two seasons without the flies, I’m happy. My suspicion is that the flies will help tame the throttle action for those who may yank the throttle open at the wrong time. With enough miles under your belt and muscle memory, making the mistake of over gassing without the secondary flies should not be an issue.

Before I took my secondary flies out, I consulted with Dynojet in the UK, they made mention of a Yamaha where they had achieved better results without the flies. Having said that, different motor, different throttle bodies, different ECU.

I think I'm inclined to just try the MH oval flies and see what happens. It sounds like it's unlikley to do anything drastic, like ruin my current setup. (?)

i wouldn't think so, they do very little except reduce a bit of intake noise, they're supposed to keep air speed up at certain throttle positions too to help with low speed running and smoothness but from what i've been able to find there's very little "proof" that changing from std, to moto, to none makes much of a difference at all. I've gone with the moto flies cause i got them with the airbox, if anyone has before and after dyno runs on just the secondary flies and it shows a difference i haven't been able to find it.
Different shape velocity stacks can vary peak HP by 1 or 2, but they mainly affect the torque characteristics by moving it higher or lower in the rev range with the subsequent affect on peak hp as hp is only a calculation based on torque x rpm. Ducati and yamaha ran variable length velocity stacks in WSB at different times with success but it was part of a very complex engine mgmt system that factored in much more than just throttle position and rpm. KTM's secondary flies are a crude but interesting attempt to replicate the same effects but with the added benefit of reduced intake noise (benefit the lawmakers), simplicity and lower cost.

paul.

Yes. My understanding was that the secondary flies are more to do with intake noise for Euro legislation rather than to add any performance gains. Not really sure though. Jesters summation of the reasons was new to me - but it might make sense.

edit- There are two threads on this subject running at the same time. Jesters comments are on the other one

i found that the throttle was made smoothest with the motobox.... i still had the standard flies and couldnt stand the chirping.

so i chucked the moto flies... felt about the same. Then i took them out so that i could make my dual velocity stack design slightly more efficient.

It did not make the throttle more snatchy, but it did make the throttle more responsive.

heat them up with a torch or something-- they strip easy. put paper towels so you don't drop the screws downthe intake..

my jerkyness went away.. loved the bike after it.. It does act weird every once and a while. not sure if the ecu is confused but i will never put them back on..

bike is stock with slipons by fmf

Sooo.....leave, change or remove????
I am for removing anything unecessary.
I did my SAS, will do my O2 and if these are not needed, I yank them to.
What is the consensus???

remove

I removed my 2nd flies last year when I had all that shit going on with the bike - it made no difference to the problem.

I've never bothered putting them back in and the bike runs very strong. (For a retro twin design.)

removing them won't make the bike slightly leaner? or will it make no difference to the A/F ratio?

I don't think it makes much difference mate.
I think my bike is running on YOUR map actually!

so i got my SD back a week ago or so after a long stay at the dyno shop ( owner of shop had to leave the state for almost 3 weeks ) , wasn't that big a deal as it rained constantly anyway. To get to the point. We tested on the Factory Pro Dyno about the secondaries , found they weren't necessary so we deactivated them and got a horsepower gain. We continued with the train of thought and figured if the flies can be deactivated then what about that big fookin secondary shaft sitting right there in the throttle body throat ? Lets take the whole fookin shaft and butterflies and all completely out !! 4 HP gain !!!

So i'm running like that - separate cylinder remapping , some timing work , whole secondary aparatus removed , matching sensors everywhere , O2 sensors gone , evap can gone , SAS gone , MotoHooligan box installed , silencers out of the Akra's and the bike's running phenomenal in my opinion , i'm totally stoked. Crisp very crisp throttle response. And i will add i can now rev down to 2,500 rpm in 6th gear where before anything below 4,000 was a biatch ! The bike is an absolute pleasure to ride anywhere anytime ----- well except below 15mph that 1,500 rpm idle there's just nothing i can do about that ...

We also bumped the rev limiter to 10,000 but i swear the guy left it at 10,300 as i'm sure i broke the 10,000 mark the other day. The power band just starts to level out at 10,000 rpm

i'm a twisties guy and i could really care less about doing 150mph so when i wear out my sprocket/chain i'm going to go from the 16/40 i have now to the 16/41 - i gotta try that combo out !!! would be about 135 mph top speed max which is fast enough for where i ride.

Cheers

Johnny

Damn I feel like a proper noob being schooled

Nice one guys. I have to admit I'm very tempted to whip them off.

no doubt was implied Johnny, don't worry - maybe it's a combination of English senses of humour and the fact that this board is generally very light-hearted, tongue in cheek with a lot of piss-taking going on...

we're not asking for the map to check it, we're asking for it so we can steal it!!

what format is the map file? and what was used to tune the bike? Power Commander, TuneECU, TuneBoy?

You are correct Klink... It will need to richened mildy from 4g up but if you run you akra map. But you could always run it to see if required anyway... Obvoisly every decent mod will require a new map.

thanks for the advice, and don't worry about the map - I wouldn't expect us internets people to be your highest priority!

Have just finished( after mr z34 twisted my arm) removing the secondary flies on mine, i havent taken it out for a spin(rain) but the bike has a very nice intake note... my neighbours confirmed that.

I did it differenty, i put a UNF thread in measured and cut 4 bolts and finished with gasket goo on the thread.
Has made the bike look cleaner and lost a little weight.

i took the bodies off the bike and made sure they were spot free before they went back on.

Well my blanking plugs have turned up but I'm moving this weekend so no chance of getting into the pits to do the job Annoying but there it is. Hopefully will get it done early next week and will let people know how it feels.

Definitely less clutter, I did the tubing route but will tap and plug next winter as well as remove the extra connectors from the loom.

Anyone been on a Dyno for a new map yet?, (without mega advance).

Are the Aussie base maps are the same as the American or European maps?

Will

I removed mine today. Was an easier job that I expected. Grabbed my map with TuneECU, disabled 2nd Flies and increased revs to 10k. First impressions in there is def a lot less engine braking. Seemed a bit up on power but nothing seriously noticeable. Will hopefully be getting a new custom map done soon with TuneECU so will then see if there are any increases. Going to wait for MrZ32 to see if his new velocity stacks do the biz though as they might get added as well.

Thanks again.
Did you happen to notice that it's able to tool around at low RPM better? Like trying to be quiet near the cops etc.