Home Made RAM AIR for CBR125R

[scaffardi]

Ok ladies and gents ive got a month off uni and nothing to do and a cbr125r that is waiting to be fiddled around with. It already has a roo racing pipe which is very loud and i am now looking to make some saught of home made ram air system so i have something to do for the next month.

Any one got any ideas of what i can make it out of or how i could do this and if it would work. The bike has two little triangle vent/holes at the front which i suppose i could use as the start of the system. Please help me with this as i am very bored at the moment. Thanks.

[nath]

Reasonable question... Keep it on topic.

[Desmogod]

Oh WHAT!
That shit was funny!
I still reckon put one of these on.
Would piss.

[barfridge]

The pipe may have it running a bit lean already, adding more air would only make this lean condition worse. So you will have to look at rejetting the carbie.

And trying to compensate for speed not revs is fun fun fun (not).

Best of luck mate, keep us updated.

[Desmogod]

Where does your airbox get it's fresh air flow from?

[scaffardi]

gday barfridge its EFI so dosnt it readjust itself???

[scaffardi]

the air box is under the seat it had a snorkel in it i took it out,it runs better and sounds better to .

[Desmogod]

For ramair, you'll want to stuff as much air in that hole as you can, funnel it in, but honestly, ramair only works at high speed.

[scaffardi]

aye i can get it upto 140km/h and the airbox is saughta secluded from the outside so it dont get much air into it so i reckon this would/could make a difference.

[barfridge]

aah, the old forgot about the EFI trick.

Sorry, I'll give myself an uppercut immediately.

[scaffardi]

thats ok barfridge. but theoretically could his work?

[Orson]

Or give yourself an undercut Jeff!...somehow.

[Desmogod]

Theoretically you may get another 0.5 horsepower.
I'm not taking the piss at all mate, but it's just not going to give you any noticable benefits.
You would be better off losing a few kilos off an alread light bike.
Your bike is an awesome learner/communter, but it doesn't lend itself too well to performance modifications.

[scaffardi]

ok but wat about acceleration?

[barfridge]

change the geaing for acceleration. Either smaller front sprocket or larger rear sprocket. But you will lose top speed, and on the 125 you don't have much to lose

[scaffardi]

yer ive just bought a one tooth less for the front sprocket but i want something i can built at home so i can by time until uni starts again.

[thro]

Just on running lean...

EFI may or may not adjust for pipes and stuff automatically.

It depends on how it determines how much fuel to deliver.

O2 sensors are typically only used for cruise AFR adjustment.

When under load (when the air/fuel ratio really matters for engine life), it will primarily calculate fuel from a load sensor - either

- an AFM (or air flow meter) or
- a MAP (or manifold air pressure) sensor

An AFM actually measures the air injested, and will give you mostly accurate fuel delivery if you change pipes, etc

A MAP sensor will not. Because it only measures air PRESSURE and not flow it has advantages and disadvantages

advantage: there's nothing protruding into the air stream, slowing the air down, so its more efficient in terms of airflow

disadvantage: volume of air injested is dependent on pressure vs restriction. If you only work out pressure, the amount of air calculated is only valid for a single flow restriction factor. change the restriction (via air filter, pipe, etc) and you'll flow more air at the pressure determined by the MAP sensor. This will cause the motor to run leaner.

Small changes, you'll get away with it.

Big changes, you could potentially sieze the motor/burn pistons/valves/etc.

I think most EFI bikes run MAP sensors?

[Tornado]

Desmo and Barfy are on the money in my opinion. The mods u mention will make a little difference but not alot. Sprocket ratio changes may be of benefit as barfy says. You can either go for better acceleration at the expense of top speed or the opposite. If all you are after is a bit of extra zip around town the sprocket option may be well worth considering. Sprocket calculators are normally easy to find too. Give you an idea of what the ratio changes will mean to you. Revs vs speed in each gear.

Please note that if your speedo doesn't run off the front wheel it will be out if you change ratios. It probably doesn't

[thro]

^^ yeah, i wouldn't expect any engine/exhaust/intake changes to make more than 5-10% difference on a modern bike. So you're talking about maybe 1-2hp gain. If successful.

As stated, better off changing sprockets, and forget about the engine mods.

[Rich]

Go ahead make some ram air tubes...

It will be a talking point but thats about it...

I doubt you'll get any noticable gain...