Mild airbox mod

[aussiejules]

once again are you sure we dont have a map sensor, from what ive seen in the manual we do, even the most basic efi i know of has a air flow meter of some sort, it needs to know if the vehicle is under load or if it is cruising at full throttle, the air intke tells the computer that information. Different maps just allow the computer to do more things better to what you want with this information.

 

[Doorag]

Riddle me this...

We don't have a 'forced air' system so the engine is 'sucking' air from the airbox, correct? All we are doing is making it a bit easier to suck the air in. We aren't forcing more air into the system. So it shouldn't have any impact at all as the engine will still only take as much as it needs.

 

[Doorag]

Anyone? No comments?

 

[Wavex]

We are not forcing the air into the engine via rams, so the speed you`re going doesn`t determine the amount of air that's coming in, it`s the design of the airbox that does. Thus, we don`t need a sensor for airflow. Where in the manual did you (aussiejules) see we do?

Opening up the airbox may make the air more readily available to the engine, and may improve performance indeed. But how do we know where the limit is? How big should the hole be for maximum performance? should we just all add a huge ram to the front of our bikes and it`ll give us 20 more HP??? More air does not automatically means more performance...


Again, my point is that we just don`t know, and until someone gets a proper dyno done, we won`t know for sure.

My personal bet is that gutting your airbox wide open will have a negative impact on performance, and that those who did a mild modification are more likely to see minor improvements (certainly nothing that a butt dyno could detect).

 

[urbanj]

huh? the airbox doesnt determine the airflow? air is drawn into the cylinder on the down stroke of the piston. the negative pressure causes cylinder filling. the size of the valves and shape of the ports affects cylinder filling along with other things.

everything before the throttle plates IE airbox and filter is surrounded by atmospheric pressure. maybe with a ram air set up it can be a touch above but this is no turbo where you are force air into the engine. with the throttle plates closed there is a vacuum after the throttle plates. at wot if you hooked up a vacuum gauge it would read 0. thats 0 gauge pressure which would be 14.7 psi atmospheric pressure. at idle and anywhere in between it would be in vacuum.

there is no pressure reading before the throttle plates.

Spoon a major Honda tuning company doesnt modify the stock air intakes and only replaces the filters. the theory is the intake pulses resonates from the throttle plate (or maybe it was the intake valves) to the filter and it has an effect on throttle response. i havent looked to much into intake designs but either way, the way our boxes are set up the side after the filter is left alone.

 

[Oranje]

last time i checked, air density changes with temperature and humidity...if you think our engines can't handle that, then you should go back to carbed crap.

 

[aussiejules]

If you look at the service manual page 7-1 no7 is the air intake pressure sensor, page 7-27 it shows no9 in the intake manifold as the same thing. The computer needs to know if throttle position is due to loading as in full throttle fully loaded up hill going slowish due to load /or if full throttle is because your going 120mlh light weight having fun. When it works this out from map(air intake pressure sensor) and throttle position sensor it works out how much fuel to put in. This is the main reason for the computer to work out, if it was working on standard constant readings it wouldnt need the computer. As i said the pc makes better adjustments to this, dont forget the standard settings have to be emission friendly where the pc doesnt. Here in oz emissions have to be 1.5%co but a car runs much better at 2.5% and has much better performance.

 

[Oranje]

if nothing else, the engine looks at amount of fuel and rpm.s for ****s sake.

 

[krid80]

It makes it easier for air to enter the engine. i did a crude test of running about 10psi shop air directed at the lid and there was a lot more air passing through the snorkel coming from the whole area of the whole. if you look at it from the side the snorkel bends and directs air to the filter.

also I dont know why some are so paranoid about fuel injection. I took this straight from the service manual so I can't get shot down here

"Signals that are input from the throttle position sensor, crankshaft position sensor, intake air pressure sensor, intake temperature sensor, coolant temperature sensor and O2 sensor enable the ECU to determine the injection
duration. The injection timing is determined through the signals from the crankshaft position sensor. As a result, the volume of fuel that is required by the engine can be supplied at all times in accordance
with the driving conditions.

suble changes can be picked up. if the bike runs lean from stock it will still run lean. maybe i little more but its not going to be huge. id think there would be more of an airflow difference at 0 feet of elevation vs say 4000 feet than this mod could do.

YES!!!!!! Fuel injection will adjust on it's own! :thumbup: - urbanj

 

[krid80]

We DO have a MAP sensor, it's called the Intake Air Pressure sensor. It's the same thing with a different name. A MAP sensor mounts on the Manifold hence it's name "Manifold Absolute Pressure" sensor. The "Manifold" in question is.... wait for it... an INTAKE Manifold. So.... IAP = MAP and the fuel map is not set in stone, but rather it adjusts to that which is depicted by the sensors as urbanj has said.

I wish I had brought my dyno sheets home to scan.... dangitall!

 

[FZ1inNH]

The '07-'08 models have an O2 sensor before the cat as well. '06 and prior do not, thus modding the airbox on the '07 or '08 is easily compensated for with the computer. These two model years will learn and adjust.

 

[aussiejules]

Yes you are correct but the main aim of the o2 sensor is also for emissions, to make sure they dont run too rich. Yes it works the other way but mainly for law.

 

[Oranje]

By the way, going back to an older reply...just because you have air being pulled in from an intake stroke, doesn't mean you're getting the same amount of oxygen...only same amount of volume, which can fluxuate with air density. Going back to page one of super-chargers/turbos...air density changes, and amount of oxygen per stroke.

 

[abner]

I hope we are all a little educated on this topic and not just shooting off at the mouth. I think we can all agree that the air has to travel thru an airbox, filter, throttle body, intake manifold, and past the valves to get to the cylinders, in that order.

Without looking at the bike... I am guessing the Intake Air Pressure sensor is going to be after the throttle body, so changing the air pressure before the throttle body will have little to no affect on the ECU.

Gutting the air box will only ease the travel of air to the filter. I'm guessing this will make the bike negligably more responsive. Gutting it will create less negative pressure in the airbox, if there is negative pressure in the airbox to begin with. As a matter of fact, I am of the belief the air box could be removed all together, because your filter would cause more restriction to air flow than the box. Going with a less restrictive filter will have little change in the intake pressure, but again will make the bike negligably more responsive. Remember, this is a fuelly that pushes fuel in, not a carborated engine that sucks fuel in.

Unless you change something infront of, or behind the IAP, ie: the throttle body or porting the valves, you will not change the intake manifold pressure drasticly enough, to the point that the ECU can't handle it.

Just my $0.02... if the IAP is pre throttle body, my therory is shot to hell.

 

[Oranje]

It doesn't HAVE TO travel through a filter ever rent a big truck for any reason?

 

[08fz6]

i realize it is a completley diff bike but we had a 2000 triumph trophy 900 come in and someone chopped off the lid completly so the filter was exposed and it ran like dog doo doo, it was very choppy or had many holes that bike red lines at 9500 and from 7000-9500 had no power and very choppy plus lower rpms was not good. just a easy and quick way I covered 2/3 of the filter with duct tape and ran it it ran through the rpms smooth and quick the bike was 2-3 times faster and ran smoother all becuase it had too much air. now granted it had carbs. but same idea. the bike was designed to work with the stock lid.

 

[urbanj]

i realize it is a completley diff bike but we had a 2000 triumph trophy 900 come in and someone chopped off the lid completly so the filter was exposed and it ran like dog doo doo, it was very choppy or had many holes that bike red lines at 9500 and from 7000-9500 had no power and very choppy plus lower rpms was not good. just a easy and quick way I covered 2/3 of the filter with duct tape and ran it it ran through the rpms smooth and quick the bike was 2-3 times faster and ran smoother all becuase it had too much air. now granted it had carbs. but same idea. the bike was designed to work with the stock lid.

you answered why it ran bad. it has carbs. thats why you re-jet. it cant get the fuel it needs and it throws the mixtures off. now fuel injection is a completely different ball game.

 

[08fz6]

yes and no. the amount of air that bike was getting there pretty much was no rejetting to fix the problem. the sensors arent always strong enough to regulate. if the fuel injection system could regulate that well then there would be no need for a power comander when you change exhaust

 

[urbanj]

youll probably see improvements on a stock bike with a power commander. if not peak hp i would be it would flatten the curve and improve throttle response. no stock map is optimum and they factor in all variables. either way, doing an airbox mod will not change anything any different than adding an airfilter or exhaust. combine them together and yes youll have a problem.

i wonder if snap on has a motorcycle cartridge for our scanner at work. id love to see the real time readout.

 

[Oranje]

A carbed bike needs the venturi effect for proper fuel.