Modern Vespa

I was told I could improve air flow and some performance by increasing the air flow through the air filter by drilling some holes on the intake tube. I did search this forum and found some things particularly an 8 page thread but that seemed to be focused on cutting a V into the top of the intake on the filter cover.

I am wondering if just drilling some large holes where I marked in yellow on the pic would improve air flow. Has anyone done just drilling holes?

What do you think is wrong with your airflow?

You just need to look inside that air filter to see it is not conducive to good streamline air flow. That "snorkel" inlet directs all the incoming air to one small area of the filter. and if you don't have a black filter you will immediately see that that is just about the only part of he filter that is being used and getting dirty.

But in answer to the question, I have never heard of anyone just doing that mod without the rest of the usual air filter mod.

That snorkel serves a purpose, preventing water or dust from getting into the filter. If you only ride on good dry tar, this shouldn't worry you.

If you try it, let us know the results.

The snorkel keeps the water out & the noise in

Run an open foam pod on the throttle body

Maybe no airbox or pod

On the 250 their is little point to doing this if you are not tuning the bike properly to get more power. If you do it you won't notice any real difference except it will be noisier and you may lose power as the ecu struggles to compensate for buggered up mixture control because it alters induction pressure waves. On the other hand it may make the motor run better at some specific speed and worse in some other areas of the rev range. I've heard it all from young un's who have actually done similar things including drilling holes such as the ones you propose. In all honesty, the existing filter works very well and you cannot make any worthwhile improvements that make any significant difference to increase power. Let us know though if you do it and what you experience! Good luck.

On a two-stroke engine it makes more sense ...

I did this prior to Cannonball this year, and it seemed to give a minimal boost. Certainly did not do any harm. Just take your time while doing it to get clean holes. If you have a drill press and method of clamping, you'll get great results.

You should disconnect the battery while doing this to reset the ecu. Once reinstalled, hook up battery, start bike and let idle for 10 minutes to relearn potential changes to the air/fuel mix.

I have experimented with airbox mods, and find them to be meh. You are unlikely to get a noticeable boost, and quite likely to make things worse. The intake is already well tuned and offers a good compromise between performance and noise reduction.

That's my opinion.

Man, that's one heavily modified Vespa.

I do agree with Jess on this point. I noticed nothing with the mod to the airbox. I did mine about 20k ago. No problems from it either.

Making the head flow better is one fix I never did.

In fact letting the engine idle for 10 mins does nothing Carl. The ECU only relearns when riding the bike. The process then allows the ECU to trim fuelling & ignition parameters at differing throttle, load & engine rev settings. It takes several lengthy rides to complete the process after which the ECU closes the learning process. It then knows how you ride the bike using what it's learned as the base parameter map. It's still a dynamic expandable map but the ECU won't keep any abnormal ride information alive in the kam (keep alive memory).

Curious, where did the 10min number of disconnect the battery come from? maybe could be less or should be more? does the workshop manual say 10 or is this duration the result of experimentation?

(Just asking)

The problem with airbox mods on the 200-300 engines is that the issue with the engine is not lack of airflow into the throttle body.. AFAIK, all of the "improved" claims come from the seat of the pants dyno, and not from anything that actually measures improvements in performance, like a real dyno. The seat of the pants dyno has been shown to demonstrate a boost in perceived performance when you cut back the power output of a motorcycle by 15% and increase the sound coming out of the exhaust. In other words, detune the engine and put a loud pipe on.
If you put a air/fuel ratio meter on these bikes, they tend to run at 14.5-15:1. So giving them more air does not bring the ratio down to 12.5-13:1 which is where the magic happens.
What does improve the engine's overall performance is bigger valves that put more air and fuel into the cylinder. The Malossi cylinder and head kit (which, sadly, is unavailable until the beginning of 2022) gives the most increase in performance, and on the dyno, about 75% of that increase is generated by the head with bigger valves. You get a bit from the increased compression ratio, and some from the increased displacement, but on it's own, a big bore cylinder doesn't change the power output that much.

Not so! My original airbox mod was dynoed by Paul Melici of PM Tuning, and he found it gave a 0.3 HP increase right across the rev range. My latest airbox mod has given me a top speed of 125 kph up a steep hill where I always test my mods, and my previous best over the last 15 years has been 120 kph.

It is not all just seat-of-pants and exhaust volume.

But I agree that the Malossi V4 kit is the only real tuning option for a GTS. All the others are just the icing on top.

Hi Mike, tbh it's difficult to assign an 0.3hp increase across the board to an airbox mod. A bigger increase would be easier to understand that this could be the case. How many times was it dyno'ed and what were the conditions & parameters for calibration & weather, temperature etc? Those factors alone can produce a variances bigger than 0.3hp.

My standard GTS300 consistently turns in an average 22.5hp at the crank on a well calibrated inertia Dyno. This varies slightly depending on the conditions prevailing on the day but the average has always been 22.5hp. Remember the factory quotes 22hp. I've had readouts of 21.9 & 22.9hp all due to those variances above, temp, barometric pressure, humidity, calibration of the Dyno etc. My bike is totally standard. It's been dyno'ed at least 8 times in the last 5 years for all sorts of reasons.

I don't know where Karl got those figures. But to be clear the GTS battery must be disconnected for at least 30 mins to reset the ecu. This info came from Piaggio hq. Relearning takes a while, not just 10 mins and the bike must be ridden, not idled and takes a few hundred miles.

30mins according to Piaggio. Ok

Re the 10 i wrote - i thought i saw somebody say disconnect for 10 but maybe i misread. :shrug:. Probably was tired.

Strom, are you telling me that Paul Melici doesn't know how to do a dyno comparison? He's been in the tuning business for many decades. I have seen the graphs he produced, but I don't think I have a copy of them any more. If you are going to be so scathing about his measurements then how about doing your own dyno test of the mod?

Why is it difficult to think that my mod could produce 0.3 hp difference? The Vespa airbox is hardly tuned for performance. Why do you think they changed it on the HPE, the first tuned Vespa in many years? The HPE change improves airflow, which is exactly what my mod was intended to do in its little way.

What is the expected HP increase that would take the bike from 120 to 125 up a steep hill?

It depends on the wind speed and direction.

Bill

There is never much wind up that hill as it is in a cutting, and the direction was uphill every time.

120 kph was the best, frequently repeated, of dozens of runs done over many years. So that would have included headwinds, tailwinds, high humidity, etc. That speed has been very consistent. Anytime I didn't manage 120 I knew I had to give the scooter a little TLC.

Mike

... with the help of a sail ...

I should always remember to put an emoji with a wink on it when I post many of my replies. 😉

The replies are often in jest.

One day I might get social media.

Bill

Mike, you seem to have misunderstood what I've said. I am not "being scathing" as you put it about anyone. Not you or Paul Melici & no one on here would surely think that.

So you know, I've dyno'ed literally thousands of bikes & cars in the last 42 years. This was an important part of my job when designing & developing motors & as a tech. I've seen every mod ever made to a car or bike engine in that time & developed many mods myself. There isn't anything much you can tell me about drilling holes in an airbox & it's effects. It may make a tiny difference, or not. It may be better, but usually not as testing has often shown. That's what I was saying.

I believe elsewhere you've said your bike is tuned? If that's the case your bike might benefit more than others, but maybe not. An 0.3hp increase suggests maybe not. Everyday you ride your bike the power output is slightly different. Due, you guessed it, to the variables I mention in the other posts above. Sometimes you'll be missing perhaps near a whole horse power or you might be producing an extra horse power, or 0.5hp. So as Peter Melici will tell you, an 0.3hp increase due to a few extra holes in the airbox isn't enough to say for definite that those holes have produced that extra power. Your bike does that frequently all on its own with or without extra holes. You'd need lots of testing before & after at several intervals to do it that way. It's much more credible that it's the usual laws of physics and all those variances at work. I refer you to my own results on my standard GTS300 bike which showed a variable output. Your bike too will be different with its power output from week to week, month to month. But not by very much one would hope. So just saying how it is Mike. An engineer would not be too quick to make the claim you have made without proper evidence. NOT dissing you.

Have a good day!

Whoa! Where'd you come from?
Welcome back!

But you are dissing me. Firstly, an engineer, Paul Melici, made the claim. I only repeated it. Secondly, I am a scientist and I know that in any experiment you try to control all the variables so that the only one that changes is the one you are studying. And any engineer would do the same. I'm quite sure Paul did several runs with and without the mod on the same day in very controlled conditions and then averaged these runs to get a significant difference. 0.3 hp does not sound significant, but its significance becomes very high when it comes out of a large number of tests. Is this not "proper evidence"? You are questioning Paul's integrity as an engineer if you don't accept the result.

And he tested it on one of his own bikes, so my other mods make no difference. Maybe it made more than 0.3 difference on my scooter, who knows?

As an engineer, I'm calling BS on this point.
It's one thing to suggest we should trust someone else's results.
It's entirely another thing to conflate disagreement with "dissing" or questioning integrity.
You know what happens when people don't question engineers (or scientists, etc.)?
Space shuttles blow up, and bridges fall down; that sort of thing.
Question everything. Test. Repeat.

Hooligan.
https://www.dailymail.co.uk/news/article-9927535/Outrage-Sydney-drivers-fined-going-just-3km-h-limit-50km-h-zone.html

My speeds are speedometer speeds, not GPS speeds. So you can knock off 10% and then I am probably legal.

Yes, but you have no right dismissing someone else's work if you haven't examined how they got their results, and haven't repeated the experiment yourself. You can't just say another's results are "not proper evidence" without good reason.

Yes, you bloody grumpy old fart, learn to use the emoji!!!!!!

PS

I tried social media, and I failed.. No idea of why...

You do know by now, why I quoted this part of your post...

Extraordinary claims require extraordinary proof
Got any?
It's not up to us to prove you wrong

A measly 0.3 hp is extraordinary???

It is if it gives you an extra 5kph top speed.

Sorry Znomit, but you are confusing two different air-filter mods. The 0.3% applies to my original mod published about 2013. The 5kph speed increase applies to my new mod of fitting the HPE air bellows to a pre-HPE GTS300, which has not been dynoed by anyone yet.

The discussion here is about the earlier mod.

Not sure if I really understood the above sentence, but for the benefit of the thread here is a link to Paul Melici's site...

http://www.scomadi.com/about/the-scomadi-team/paul-melici/

Not sure if this will help...

Thanks fir that link and reference. If he says 0.3% I think we can believe him. I do.

Mike, I've never said I don't believe anything you've said about what you've been told. I've never said your mod couldn't give you more power. I've never dissed you or Peter. You need to re-read my posts & those of others.

I'm just querying your claim, that drilling extra holes will automatically increase your power, which any engine scientist will query, when presented with information of the kind you have presented. It's common place to get variable hp figures from just about any engine when testing. It can vary daily & is a technical factual point often not known about by the public or simply overlooked. Mostly drilling holes such as yours on most bikes does nothing to enhance performance. In fact it can be quite the reverse as many engineers have determined including me. It's also not credible that 0.3hp will give you an extra 5kph uphill to 125kph. The extra power required for that feat is going to be much higher & depending on the hill of course. 0.3hp is insignificant in terms of testing & won't actually be detectable on the road. Your bike power output varies far more than that on a daily basis even in standard form both up & down the scale.

In conclusion, & to remind you of what I have said, you 'may' be getting extra power from the mod. But because the figure you quote is insignificant in engineering testing terms it cannot be regarded as evidence of improvement due to 'drilling holes', at least without more testing information. Any speed increase you are getting won't be down to just 0.3hp.