Modern Vespa

top left is the gt200 airbox, main pic is the gts airbox.

It is exactly the same airbox bar the central pipe.

As far as I can see the u shaped apperture in the 250/300 airbox was designed to have that central pipe in the 200 diagram fit into it. Thats why its the shape it is.

The fact there isnt a central pipe in the 250/300 airbox leads me to think that piaggio in thier wisdom left it out, presumably to allow a larger and smoother airflow into the box for the larger engines.

makes sense to me.

If piaggio had specifically designed the airbox for the 250/300 why cast it with the u shaped apperture? why not cast it with a hole lower and close the u up across the top so the filter is being held even more securely?.

because they used the 200 airbox design, just took the central pipe out and it worked well enough


but with piaggio in thier wisdom leaving out the central pipe in the 250 airbox they themselves have increased the chances of dirty air getting into the engine by having the filter just resting on top of the u shaped cutout, The airbox was not designed to work this way.

The filter in the 200 airbox doesnt have this (admittedly small issue) as it seals against the square end of the central pipe.

If piaggio "designed" the 250 airbox to seal as well as the 200 airbox they would have added a piece to seal the top of the u and added the hole lower.

like this



I think I will add my own bit as above to ensure the filter is 100% sealed as it is on the 200 after all this is the way the airbox was originally designed to work.

This is where I disagree with opening the u aperture at the top as you are significantly increasing the chances of dirty air getting into the engine (sorry Mike, You still take the credit for the mod )

What about my 2nd nipple?

Without it, you're only half a man. You need two nipples!

So, for Mike and the brave souls who copied Mike's design prematurely, here's an idea how to eliminate the risk of a flapping filter letting in dirty air: bridge the two ends of the partition, to form a new sealing edge.

I've used a longish clip designed to bind paper documents together. The outer edge is rounded, which won't be biting into the foam as well as a sharp edge, but will still seal better than no edge at all.

Below are two quick shots to demonstrate the idea and the part I used. They use(d) this part in Germany. Not sure if it is available in other markets as well.

Been kicking the same idea around today. Going to pick up some small metal tubing tomorrow to slot the ends to fit over the web. Then I'll remove most of the web.

Here's a represenstation of how much I've cut away;



Not so much that the filter can "flap around" but enough to increase air flow. I've also cut a vee in the top of he inlet snorkel.

The other thing to remember is that the air is coming in to the air box through the top of this snorkel ONLY. So as long as that's pretty well embedded in the filter foam there isn't too much to worry about unfiltered air!

My filter has not budged after hard riding - have opened it up three times to check. But considering the damage a bit of grit could do, I heartily recommend the bridge over the gap.

No idea about the missing nipple. Have you considered plastic surgery?

Mike

Sorry Scaramanga, no idea?

Wasnt one for draining water and the other for oil?

I might have just made that up though.

Expanding on windbreaker's idea to bridge the U I went down to the hardware store and got some thin aluminum tubing. I cut the plastic out to the last rib on each side. The tube was cut to length and the ends slotted so it fits over the remains of the dividing wall.

Have not run it on a bike yet.

quickly do it now!

Let us know how you go.

Very brave chopping there, Patrick. You removed twice as much as I did. Can't wait to hear the results.

Mike

How can you tease us like that?

I'll be here rubbing my nubbin waiting on your results.

It was pouring down rain here by the time I finished and I want to have a quick ride on the bike before making the swap so the comparison is closer in time. Given I'm doing this on a GT and don't have the benefit of an ECU to fix the jetting for me I'm not sure what to expect. I know the LX does not like having it's airbox messed with much but it starts out as a single box with tuned inlet tube.

The cutting is not so brave as I have a second airbox to play with. I'll try and make the swap tomorrow during lunch. I'll be switching it back to stock after the test so the results will be bracketed on both sides with a comparison to stock.

Took mine out for a test yesterday and I can scientifically say that my GTS is now faster than a quantam sports car and a Harley.

http://www.youtube.com/watch?v=ZCDRMF6mfuc

How about this???

I was wondering if any of you who have tried this mod have one of those Super Corsa Power Boosters from Motorsports Scooters? These are designed to allow you to increase your fuel mixture. I have one on my bike and it does make a difference but If I do this mod should I make any adjustments to the Power Booster as well?

I can say with certainty that the GT200 does not like having its airbox messed with. Most likely a mixture issue due to the CV carb. Initial roll on was promising but then it just started surging and would not rev out. CV carb + CVT transmission makes jetting a pain.

I'll see if I can find a GTS to try it on.

Funny. I would not have thought that any modification would actually be easier on a fuel injected machine! But so far changing exhausts has been accommodated ably, and we shall see how Mikes Mod takes on some more GTSs. Given also that Jess got the Malossi V4 head/cylinder running fabulously with no changes to the EFI, it looks like the EFI system Piaggio use is more flexible and adaptable than some have previously thought.

Back in the good old days of 2-strokes, who could have dreamed that a scooter would one day adapt itself to take advantage of our modifications!

Hey, Glover, cool it!

You will lose all credibility for my mod! 8)

Sorry it didn't work for a GT200, Patrick. Maybe it needs a larger jet to go with it. But CV carbs are rather a mystery to me too. I tried studying up on them when I had a GT, but never realy got the hang of it.

Mike

Anybody else take the plunge on this?

Windbreaker?

Anyone?

I'm still on the fence. Waiting for some nice weather so I can get inside the airbox (actually, airboxes...need to clean filters for both mine and my wife's GTS). While I'm in there, I'll assess the situation and decide whether I'll cut or not. If I decide yes, I'll first do a comparison ride vs my wife's GTS to have a benchmark. So far, I only remember reading that it FEELS quicker, not that it actually IS quicker. Placebo can be one strong effect

Although I believe it is quicker (and torqueyer), I really wish i would have done some benchmarking first to prove it out.

Paul Melici of PM Tuning has put my mod on a dyno. He found about 0.3 hp increase over the whole speed spectrum. I was a bit disappointed - it feels like more than that to my backside. But he was surprised that a simple pocket-knife hack could produce that result.

Paul thought the extra air might make it run lean, and with an aftermarket exhaust this could be exaggerated. But I think he was just trying to sell his TFI unit. The Piaggio unit should cope, if it can cope with a Malossi V4 mod.

Mike

NB1. I didn't really use my pocket-knife. I used some small tinsnips.

NB2 I recommend the version of my mod that keeps the top of the U intact for holding the filter, and just opens things up below that.

Mike

For my baseline I used a straight section of road with about a 4% up hill grade. Found a line in the road for the start and gave it WOT. With a good Tach the RPM leveled at about 7300-7500 and I crested the hill at 50mph indicated.

If power had been improved I would expect to see higher RPM on the tach as well as faster speed at the crest of the hill. This method should work as long as the speeds stay below ~65 where the variator maxes out.

Two comments on that:

1. I would think that .3 hp are within the mean variation of a dyno. That would be about +/- 1.5%.

2. From what I would expect, and from what you guys who did the mod report, it should be torque that's increasing, not horsepower. If you feel better acceleration, that's torque.
I think more hp would mean more RPM with enough torque to keep pulling--and, at least on my GTS, I'm reaching the point where the governor kicks in without the mod.

The dyno graph Paul sent me showed the "after" line consistently one line width above the "before" line, over the range of 10 mph to 85 mph. That corresponds to about 0.3 hp. If this is within the range of error, then the dyno errs very consistently over two consecutive runs and a wide range of speeds.

Pauls comment was -
There is defiantly a marked increase by the thickness of 2 lines and almost all the way across the speed range, quite significant for a quick mod

Mike

Mike what silencer are you using LV,PM ??

The standard Piaggio silencer. I like my scoot quiet.
Also have a Polini variator and Malossi clutch springs.

Got a look at a standard gt125 airbox today and guess what.

No central pipe.

Thats my theory fucked then.

Really? carbureted, not fuel injected?

Carb model, I suppose someone may have taken it out.

airbox was exactly the same as my 250.

After having cleaned the filter and having looked inside the air box, I decided against a mod for now. I found it would not easily be reversible, so I will live with what I've had and what made me happy for the last 27,000 miles.

78MPG I woulds leave it alone too.

Having recently done both the Dr. Pulley Sliders (10g) and both the V cut and the cut on the outer air cover mods I just want to give you guys my findings....

I really should have done each mod separately and rode the bike for a couple of weeks so I could have individual results. But I was too excited to get everything done in one shot so here we go.. Acceleration has definately improved, feels torquier throughout the whole range. People say the sliders make the tranny "smoother" but I find it not so. The extra power makes it actually a tad jerkier or harder to maintain at low low speeds. I noticed with the original rollers I can easider control the RMP from 1750 to 4000 range. With the sliders it's a bit harder. With a bit more throttle it'll go right up to about 4500rpm, thus really noticing a good improvement in takeoffs. In general the bike feels about 15% faster. More responsive, maybe a bit too responsive in the low rpms. Not a big deal though because you do get use to it rather quickly. Noise level wise, it's not noisier in any way. Like Mike said, just maybe a different tone.

Now for the bad news... I notice that my fuel economy has really suffered big time. With the rollers and "pre" airbox mod I would get about 200-210km on a full tank (about 7 litres, or when the last bar on the fuel guage dissapears). It's safe to say that I'm getting about 150-170km per tank after both mods. The fuel gauge is currently at the half way point and I got 65km on this tank (I usually get 100km right at the half way mark). However, I was riding double up (250lbs) and averaging 80-120km/h on this tank of gas, pretty much WOT most of the way.

It really is more fun to ride with the new mods but that's too much of a hit mileage wise. I'm going to undo the outer airbox cover mod but plugging the large hole I made to get more air. The V cut will stay as is as there's no way of reversing this. I will also be opening up the crankcase and checking to see if the belt is doing any rubbing on the case after the Dr. Pulley slider mod.

You can't just change torque without the power changing also. If the midrange torque increases, power increases also at those rpm's even if the top end stays the same. If there is torque, there is always horepower (or else the rpm has to be 0). I can't understand that torque is used to denote engine characteristics up to a certain rpm and after that, power is used instead.

Power = Torque * RPM / 5252.

it's important to remember that whenever you modify your scooter, your first fuel usage figures will be off... cause usually you are opening up the throttle wide open in order to "test" your scooter!

So a vast majority of the riding will be harder than what you were doing before, also after doing the air mod you should disconnect the battery overnight so that the ECU can reset itself... i find it helps keep the fuel usage from rising too much as well.

I've refilled twice since the mod, and I don't notice much difference in fuel economy. Click on the fuelly banner below for my fill ups. My commute is stop and go on surface streets which is why the low number.

My car gets 15.4 over the same commute (plus $12-20/day for parking), so a bit of a decrease would still be way better than my alternative.

Even if I did notice a dramatic decrease in economy, I don't know that I would reverse it . . . I like the way it now confidently pulls out of a corner when i roll on the throttle, and I like having the extra oomph in tight situations.

The difference from economy comes from the Dr Pulley sliders. I liked them initially until I discovered they were casuing the belt to rub a deep gouge in my crankcase. They came out to be replaced with a 9 roller Polini which is much nicer, and much more economical.

I got 120 miles per tank with the DPs and 140 with the Polini. The air filter mod made little difference.

This just in:

You implying my mod is just a "nose" job?
Mike