Modern Vespa

Didnt see if you mentioned it in the OP, or any of the later posts but DO NOT do this mod to your airbox on a carbed scooter. There is a breather tube that fits in that recess and it limits both the volume of the airflow as well as the turbulence to an extent. Minus that tube the carb will be sucking in too much air and you'll be running very lean, and develop the "lean jutters" where at certain points in the powerband it will hesitate and obviously if you keep it up you'll be damaging your engine.

I attempted to remove the breather, and open the passage a small amount and that was the result for me. I've since replaced the tube, and patched up the cuts. Back to normal operation. This serve more as a warning to the casual modder, or might attempt this and then wonder wtf happened.

Note again for the casual modder: the reason this will work on a fuel injected engine is the ECU will adjust the mixture (add or subtract fuel being injected) based on the air intake. A carb has no ability to do that hence the issue.

You may now return to your normally scheduled broadcast. Thank you.

good warning, 100% treu but you forgot something...

with a carb engine you can do this mod but you just have to put in a bigger jet, wich one depends ons wich one you have now and how far you go with this mod.(the more airflow the bigger the jet)

I take no responsibility here! You'tre on your own, Baby!

Mike

filled her up today, i did 195km+-2km with 6L since the mod and the new airfilter.
my driving style was more faster then normal because of the joy of the throttle repsonse etc.
so i mostly accelerate WOT and some top speed WOT runs here and there + the stormy weather with windgusts up to 90kmh where i was forced to ride with WOT to keep some speed.

normally on a normal day with normal speed and not driving so much with WOT i would do 185 - 190km max so i have to say untill now it seems my milage went up !

i also changed the sparkplug to a iridium version, i was forgotten how a PITA it is to change that d**n plug !!
i'm going to make a thread asking if somebody knows a better way to change it...

Hello,

I'm an Aprilia Sportcity 250 owner. I'm posting on your site because I scour the net to find hints for projects I undertake on my scoot.

I caught your site/airbox thread after I had started mine. There is also another one on this site for the MP3 bike:
Airbox modifications

I thought I'd share my efforts if it helps any of you:
http://www.apriliaforum.com/forums/showthread.php?243738-SC250-Airbox-Mod

Our airboxes are different, but we are trying to do the same thing, modify the airflow through the stock airbox for improved performance without increasing the noise level too much.

For me, I found it useful to make some measurements of the airflow path to see where the airflow restrictions are and modify against those points. If someone does this, I would be interested in your observations vs. what I may uncover. In the end, we have similar displacements, so the airflow observations should not be too far apart.

Jerry

As an update to my mod, I want to show the effect it had on my air filter.

In the image below, just consider folding the filter to the right as if it were a page in a book, to make it sit where it was.
You can see where the air is coming in. Just look at the black areas. Clearly, the three holes I drilled are utilized by the air, and the original end opening of the rectangle duct is equally utilized. (Unfortunately, a positive effect on engine performance is still pending...).

The filter has been in use for about 6K miles and shows vast areas of unclogged surface, so the cleaning interval is more than safe, even with all the cotton we have in our air these months from cottonwood trees. They are what you can see piled up on those black areas and inside the airbox cover, opposite the air outlet of the duct.



Just FTR, I clean a dirty filter with gasoline, dry it completely, and then use Uni air filter oil to prepare the filter for its job.

Question to all who have done this mod: have any of you noticed a check engine light coming on at certain situations?

I am pointing to my thread on this issue and am curious to hear what you have (or have not) found.

I have no problems whatsoever...


Engine light can't be caused by the air filter as far as i know, there are people riding K&N sportfilters on theyre mp3's without any problem.

No problems here, but I did not do a too drastic cut...

Some guys have cut away that whole panel, and then fitted a strip to keep the filter in place, and not reported any problems.

Mike

Yeah I use Mike's mod now, but beforehand I have installed pod filters on GTS, BV, and Scarabeo 250ie and 500ie...

Not once did a pod filter cause any kind of engine light, and if the pod filters didn't then Mike's mod won't either.

Something else is going on with your system mate!!

Yeah, I could not really see it either but needed to know to eliminate this option.
I will be installing a new lambda sensor this weekend and hope that will be the end of it

Subscribed!

Timely (not!) update: the hose from the evap system to the intake had come off. The new lambda probe was a waste of time and money.

I like the looks of this mod. After reading this long discussion I kinda got lost. If I want to do ths to my 2012 gts super what parts/size do I need to get to make a pod type filter? Send me a PM if anyone wants.

Glad to see you are still around!! How you doing Arno?

Did the mod on my supersport gts 300 2 days ago.
Anyone NOT doing it is missing out big time I think.

The intake "channel" i did the "naca" profile on as seen in beginning of thread.
The opening inside the box, I did not widen it at the top, but created a pear shaped opening.

I do get perfomance gains. Top speed is up, I now hit the revlimiter when going slightly downhill and a slight headwind. Previously this required a big downhill section with some tailwind.

Acceleration is improved, it keeps speed at indicated 130 km/h even uphill and slight headwind, that was impossible before, it was just over 120 before.

But, the biggest improvement is in the not measurable part of an engine characteristics.
The engine is now so much smoother. Before it was a bit "rough".
When standing at a traffic light, previously I never used the rear brake, since the whole bike started to shudder quite badly. Now it shudders, but not much, very tolerable now.

Throttle control at low speeds is better, the "shudder" accelerating from slow is gone. Now acceleration is smoooth.

The FEEL of the engine is MASSIVELY improved.

I did not touch or clean the filter.

I did reset the ecu, disconnected the battery for 1.5 hours.

Also I had the exhaust off and I did put in new shock absorbers in the rear, zelioni. But I would not imagine they would impact the feel of the engine?

Anyhow, Many Many thanks to MIKE, the hero, for initialising this mod, it is just beautiful. Had I paid a 1000 dollar for these improvements, I would have been resonably happy. SUPER MIKE for president.

And do you now get 100 miles to the gallon?

Come off it, OrangeDanger! My mod can't be responsible for all that! You must have changed something else at the same time.

Many have been pleased with my mod, but nobody has praised it that highly before.

I often wish I had patented it and charged a fee. 8)

Mike

Very true, Tech, but if I had a carbed engine I would be doing my mod and then fitting a larger main jet (and adjusting the other jets to suit). I got a nice improvement by just upping the main jet of my GT200. Doing this mod I could have gone even further.

Mike

I love the mod, fuel consumption, well, I do not check anymore. But I can check next tank, not that I care, but still interesting.

The only thing changed at that time was the rear shocks, to new zelioni stuff, which has also made a massive difference to the bike. Now I have front zelioni and brembo left to install.

Hey, I was just kidding about the fuel consumption, in response to your over-the-top praise for my mod.

But I am delighted that you are so happy with it. Your enjoyment made my day!

Mike

hi, interesting topic and thanks for the pics, please share your views whether these cuts are the most appropriate ? I Will open and try these out, cheers

Naca like this:
http://members.modernvespa.net/oopsclunkthud/uploads/img_2187_212.jpg

pear shaped, no pics of, but I started expanding about 1 cm below the top, so I do not widen the gap at the top. Then so wide that I touched the "bulge" on the left side, when viewing from the side that does not have the Intake pipe into the engine. Then replicate on the other side. Left about one cm from bottom of pear shape, to the bottom of the filter box.

I hope that will do. I really to not think you can go wrong with it. Just do not drill extra holes, that I do not think promotes a smooth flow of air.

Good luck and do not be afraid, you will need to remove the box from vespa, cut is possible to do with the box just opened, but still attached to the vespa, but the cleaning is impossible, for me at least.

Here's my hack-job, one year later(less than 5000km, all in Sydney metro). The bike is certainly more responsive and the part-throttle midrange is definitely better. It's also a little louder than other GTS 250s. I have never had any problem with engine lights or the like.

I removed a dodgy fuzzy washer today & haven't ridden it again yet so the top speed remains to be seen. I don't have the room to wind it up, the Warringa Freeway is too short and too busy. The engine (I replaced a dead one) came with a Malossi variator which I have 11.5g weights in so the top speed is probably not tops but the acceleration is, I rarely need to use WOT in general traffic. Well, "need" is such a subjective term.

Fuel economy? The 11.5g variator weights added about a cup (give or take a tablespoon) to my usual ~7.5 litres per 200km which is entirely inner-urban Sydney.

Thanks Mike, I like your mod.

Its not my mod that makes it noisier, its the Malossi red filter. But fit an aftermarket exhaust and you won't notice the induction noise anymore!

Mike

I'll be back ...for report.

Cutting away the snorkel like that will help a bit, and bring more of the filter into use, but I think the performance gains are mainly due to the extra holes/cut away in the dividing panel in the other half.

Mike

A little bit, i think you' re right.

I'm gonna do the rest of the mod and i'll report.

Done ! I'll be back to report. Maybe 33% larger hole.

Nice and clean, now any improvements ? Will probably cut likewise

I think that's better, maybe around 15 per cent, i don't know.

To be sure the machine should be evaluated before/after with a horse power mesuring system...

If someone....

first of all, many thanks for this ideas, will try this on my 300ie Super (2015 model) in next days

I have only one comment on the V shaped cutout (one of the solutions)

as engineer would recommend you NOT to finish the V with the acute, sharp angle! because, this will be ideal crack propagation spot!

better would be to roughly find out where the you want that your tip finish and drill bit bigger hole (7-10 mm dia) there. then, using Dremel or scalpel finish your V shaped cut pointing towards the centre of the hole!

this way, you will avoid any "crack" (intentional cut in our case) to propagate under vibrations and loads of that piece of plastic.

alternative would be very rounded V shape Philip190 used.

V shape is good for one more reason: further noise reduction

Okay, I've spend allot of time reading about this air filter mod. I can't friggin wait to hear those sounds you guys are yappin about. My dishwasher just beeped. after drilling and cutting I thought it would be good to give them a good cleaning. I will add mineral oil to the filter too...

Hi friends,
I did the following calculation:

outlet from airfilter body: 45mm dia circle = 1590mm²
inlet into airfilter body: 27 x 50 mm = 1350mm² or 85% of oulet

Would'nt it be necessary to have at least an equal outlet and inlet?

By adding a plastic tube with 25mm diameter as additional inlet we would get 16% more inlet area then outlet.

What's your opinion on that idea? Nonsens or worth to follow the route?

Ciao
Nicolaus

the engine draws air from the airbox only 1/4 the time (on the intake stroke)
the airbox can draw air from the atmosphere all the time.

Have a video of it so we can hear the noise.

This all sounds facinating, looking forward to the next instalment!

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Philip, the airbox mod was tested on a dyno by PM Tuning many years ago, and Paul Melici told me they got a one-third horsepower increase right across the rev range. Doesn't sound like much, but not bad for a simple mod you can do with a pocket knife!

Mike

after a good long read of this thread ive given it a go.
my 250gts already had the curved cut in the airbox,so just the v-cut in the front cover.a definite low burble on acceleration,not annoying at all,sounds better imho. acceleration,improved
ill give it a while to see if its worth making the curved cut any larger?
thanks for your input

There's another happy user that owes me a beer. I'll have to schedule a round-the-world trip someday to collect!

Mike