more flow in - same flow out

[donzo]

What if I opened up the airbox and got a dp ecu for now and saved the exhaust mods for later? 

[He Man]

not sure, but you can run open airbox with stock exahust within acceptable limits. i have stock ecu cored pipes and open airbox.

[redial]

youll still have more flow out, it will just be more "cramped"

you should be fine, its just that airbox+exhaust+ engine software will have a 1+1+1=4 effect

do you guys agree with that synopsis?

[Scotzman]

not sure, but you can run open airbox with stock exahust within acceptable limits. i have stock ecu cored pipes and open airbox.

Do you notice any problems or benefits with the opened airbox and a stock ecu?

[teddy037.2]

if it's just a matter of "what can I find right now for sale" I'd say just collect the parts, and install them all at once.

dumping more air/fuel in w/o the higher flow out probably won't hurt, but it is kind of pointless, if your bike is currently running fine



*the obvious advantage to slip-ons first is the noise it makes    then do the intake/fuel after for full gains

[redial]

++++++++


if i may get nerdy for a second, this is how it was explained to me a long time ago. most of my experience is with cars so if anything doesnt apply to bikes, or if anything is just plain incorrect, please do hurry to correct me, as i know there are much more knowledgeable people out there.


so lets call engine E and then  0 will be a puff of exhaust gas (a puff because air comes out as the cylinder exhausts gas, not a constant flow)
and then > will be a vacuum:

E  >  0  >  0  >  0  >  0  > (atmosphere) 

as a puff of air is shot out the exhaust, behind it forms a vacuum. each vacuum created by the engine forcing air outward through the exhaust, helps to pull the puff of air behind it
this is 'Backpressure' .

Let us assume that this structure of exhaust gases and vacuums helps to vent gas best somewhere between idle and 100% WOT
this optimal pressure most efficient in doing the above job.

we often hear "less restrictive" when talking about exhaust. a less restrictive exhaust will allow larger puffs of gas, while still mainting these vacuums.
so why dont we all throw 5" straight pipe on everything? because if there is not sufficient pressure to produce a vacuum, your exhaust now looks like this

E00000000

and there is danger of spent exhaust gas being drawn back into the cylinder as the exhaust valve closes. (instead of the vacuum pulling the air out) this spent air is not combustible because weve already burnt the oxygen in it.

so by having a less restrictive exhaust, you move the "optimal point" of this system higher into the RPM range (where you are pulling more air)
it will give you more horsepower at that specific rpm, but theoretically less, wherever the old optimal point was.

so how can an aftermarket exhaust dyno show gains at ALL rpm levels?
because stock exhaust is first made to comply with noise and emission controls. it has to comply with EPA standards, and after that they can engineer for performance reasons.



Back to Airboxes, ecus and exhausts.

what will airbox alone do?
well i would guess that it would increase the airflow, increase backpressure at all RPMS (moving your optimal exhaust point down in the RPM range) more air into the engine using the same fuel mapping will cause the bike to run lean, if it were stoich before the mod. this is why people say to do it all at once
is this useful? dunno.

what about exhaust only?
probably the opposite, it would decrease backpressure at all RPM, therefore moving your optimal efficiency point up in the RPMS. probably where we all want it. it also should not cause the bike to run rich because it has no effect on the air being fed into the throttle bodies. so is this useful? i say yes.

whats the ECU do?
adjusts the air to fuel ratio to compensate for the leaning out caused by the intake, or to custom choose the best a-f ratio for your specific application. for example, many boost set ups run rich because unspent fuel cools the hot compressed air. you really need a dyno and a wideband AFM meter to take full advantage of tuning with an adjustable afr tool like this
in addition, stock AFR is also set up to comply with emission levels. rumour is that the EPA only tests at a certain rpm, and so retards the mixture at that level. this can be seen on a dyno for bmw e46 zhps at  4100 rpm quite easily. im not very sure how stringent bike requirements are, so i cant say if a motorcycle would suffer the same "dyno-dip"

so hopefully that sheds some light on simple mechanics for anyone who didnt know

hurry someone smarter than me red pen this!

[yotogi]

No expert, but everything that I have read on airbox, header, exhaust mods lead to leaner and leaner conditions.

Need an expert here...

[Gus Duc]

No expert here but I've had several exhaust & ECU combinations on my 06 S2R1K.  I'll also add I never had any surging issues & bike ran good stock.

My first mod was 14T sprocket & Spark collectors with closed lid & stock ECU with O2 sensor connected.  Much better bottom end & decent sound too...... temps dropped & fuel mileage stayed similar.

Next setup was the Sparks, Arrow carbons with S pipes & stock lid & ECU...... sound was great but the bottom end suffered some while the top end gained some.  Real problem was the S pipes... which started @ 40 mm & ended up @ 50mm... no room on the right peg for my foot.

That led to my last setup...... ditched the Sparks & went full Arrow..... deeper sound, & much more room .... I could use he whole foot peg   I dyno'd it with the full Arrows, open lid, OEM ECU & O2 sensor...... it made 82 Hp & 62 ft./lbs of torque & had an average A/F of 15/1 which is lean but not much different than stock.  I then added a DP ECU & it only gained 4 HP but 7 ft. lbs of torque & the TQ below 5K was much higher...... the motor really like the extra fuel.  Average A/F was 13/1.

I recently went back to all stock.  First I tried the open lid but the intake noise with no exhaust noise drove me crazy.... sounded like I was going to be sucked thru the tank into the airbox   I put the OEM lid back on & then the OEM ECU & I noticed that I lost some throttle response which I'm sure is a combination of the lid & the ECU.  Still no surging with the O2 sensor plugged in but It's way softer on the bottom & seems to run hotter...... I'm sure that's the udder causing that.  I put the DP ECU back in with the stock exhaust & closed lid & it's much nicer down low..... didn't dyno it but plugs look good & it feels much nicer.... kind of like going down a tooth on the front sprocket.

If I could design any exhaust, I'd have one that had the clearence of the Arrows but had a little smaller tubing & exited into a single can so you can see the whole rear wheel.

 

[donzo]

wow, that's a lot to digest.  thanks.  so many different combinations, but the consensus looks like a dp ecu for any set up would be recommended.  pretty much essential if air flow in is altered?

[redial]

allowing greater air in without altering air fuel ratio will make your bike run lean

unless its already running rich, then itll fix it 


exhaust should be perfectly harmless by itself

[Howie]

You have a US version 800 no?  No O₂ sensor, correct?  A Power Commander with a custom map will fix you up.

[redial]

in addition, stock AFR is also set up to comply with emission levels. rumour is that the EPA only tests at a certain rpm, and so retards the mixture at that level. this can be seen on a dyno for bmw e46 zhps at  4100 rpm quite easily. im not very sure how stringent bike requirements are, so i cant say if a motorcycle would suffer the same "dyno-dip"

just thought id mention, FastandLight posted his dyno, and it illustrates the "dyno-dip" just perfectly.
as you can see, he did away with that with a custom map  good work fastandlight

can also be seen on the HP curve, but its more apparent on the tq curve

[teddy037.2]

yep, my bike had the same dip 'round 4k