Modern Vespa

Never ceases to amaze me how the 2-stroke can be tuned by the exhaust design.

I totally understand the theory and can do the math myself. Thing is I gave up the latter because of all the variable you simply cannot approximate accurately enough and even if you could the bends will do you in.

In scooters it again amázes me. For one the water shed between box types (divergent cone discharge in expansion chamber) and the ´proper´ resonant expansion chamber designs.

Secondly that the latter seem exclusively aimed at the higher rev range whereas (theoretically) the resonance could ´supercharge´ the OEM rev range just as easily.

Trying to distract my mind from a friend´s horrible accident stumbled on:

https://www.sip-scootershop.com/es/product/escape-racing-sip-performance-legal-para-vespa-200-rally-p200e-px200-e-lusso_2001000H?usrc=escape%20p200e

and

Would that be the supercharger of the OEM set up?
If I read the blurp correctly it is aimed at the 10-12 hp 200 cylinder and the claimed performance starts at 15 hp.
Now, I cán believe that starting with the restrictive OEM pot a tuned exhaust can lift the output from 10 to 15 hp but WOW

Bottom line is that I know that a tuned exhaust is like a supercharger which cán increase BMEP to levels.
I will be fitting a Polini box to my P200E shortly and will most likely be happy with it but... I have been fascinated by the resonance chamber effects since Ernst Degner defected and have no reservations to pay money to scratch that itch.
The crux is how valid the SIP blurp is in the real world on a standard 12hp European P200E.
What is the forum knowledge about it??

Late eighties I had (could not be more befitting the subject) an MZ ISDT 250 machine. Not the works one but the training version based on the bread and butter ETZ engine which powered my daily sidecar combination.

The ÓNLY difference between the engines was a resonance chamber exhaust and yes it had a massive effect without extending the power band as the crankcases (nor the heat management) could not handle that.

This
Expansion exhausts PX200E
is the only to the exact point thread I could find here.
The bottom line being

I wíll send SIP an email but am aware that this is akin to asking the hair dresser if you could do with a hair cut.

Hmmm... no dice. Despite the tuning to not discard low end, the JL will in comparison with the Polini box basically swap a few draft horses for a few racing horses.
It is what the bulk of customers expects/wants with tuning no doubt so, Polini box it will remain.

Polini box is a good all around solution for touring setup. Wide power band, torquey bottom end, a bit extra on the top.

THank you for the confirmation. Looking forward to fitting it.

If you happen to be looking for something between the Polini box and a full expansion, have a look at Megadella. Friends who have used them swear by them. Facebook is probably the best place to see what they do but check out the site. They do variations on each style and will advise on which to choose for your particular setup. Here's one to suit the 200 -


https://www.megadella.it/prodotto/megadella-l-compact-8-coni-x-200/

Posch Performance has been developing his resi-box (among other things) for some years now, the only one readily available is for the 306 sadly. You can read all about his experiments, failures and successes on the German Scooter Forum.
https://www.sip-scootershop.com/en/product/racing-exhaust-posch-performance-resi-box-bfa-306-for-vespa-125-vna-ts-150-vba-super-160-gs-180-ss-rally-px-pe-lusso-t5_78245615?usrc=POSCH%20PERFORMANCE

Most of this development is being driven by the need for German-registered scooters to comply with TUV compliance. Easier to use a box exhaust legally in Germany than full expansion.

There are a number of pipe design programs available allowing you play around with different specifications of exhaust. Many include the ability to print cone sections which you can transfer to steel and make your own.

Yes a proper tuned exhaust will boost the power so much I saw some dynotest results about the same top end with box and expansion chamber exhausts. Expansion chamber always give more power on higher RPMs, I wish there was an expansion chamber as silent as the box.

Bit extra maybe over standard exhaust, but considerably slower top end than a sip road 2.0. When i say considerable, we are talking 6mph difference, which is considerable for a cheap PX upgrade. I sold my polini box, as have many others and went back to the road 2.0, although the polini was great around town, hills , it would not rev high enough to allow me to reach past 59mph GPS with a DR180, despite timing changes etc. I can rev out at 65mph GPS with a road 2.0, with a gearing upgrade I could push that a couple of MPH more. If you want a cheap top end boost that a road 2.0/3.0 is the thing.

Thanks all.
With the Polini on and jetting adjusted will keep this on the list.

Expansion exhausts can de tuned to any rev range and band. Can also be made silent by muffling at/after the stinger. This does add length and bulk.
In both cases the market expects something else: More tóp end power and racy sleek looks.

Will dig into Megadella.

Read through the Megadella site. Still scratching the surface of Facebook.

Seems though that ´For original 200 engine with maximum low torque: Mod. 180704018´ is what the doctor ordered so asked for a quote.

The SLX construction looks to be impressively sturdy too!

Have answer from Italy and the pricing incl. shipping is VÉRY reasonable.

Will order it.

Ordered.

Paid.

Thank you again Ginch. Cannot thank you enough actually as I nevvahevvah would have found the product.
The guy is a pleasure to deal with.
Price a positive surprise.
Assuming the product is as described I can understand why those friends swear by them!

I hope to report a (non scientific) comparison from OEM to Polini to Megadella.

p.s. I find it really motivating that he is developing his exhausts. I mean this is 20 years after the 2-stroke was declared walking dead but wave science is not so WOW that new understanding is applied to our classic 2-stroke Vespas.

well, never expected the title to be thís apt; the Megadella boxes are pure magic.
The photo below shows the diffuser and reverse angle baffle. Missing is the blind bouncing wall. It is to all extends and purposes a tuned proper expansion exhaust. Nothing short of genius.

the dyno results are
If this can be extrapolated then that would make easily 15 hp on the P200E
Ok, that is what the theory is too but still über in a not loud bóx!

My pleasure! Shipping was very UN-reasonable to my end of the world so decided against it. I'm glad you had a good experience so far. I'm constantly amazed at the furious pace of development within Vespa and Lambretta circles over the last few years. People like Crimaz, Egig and others re-inventing the wheel into a super wheel! And as you say, production ceased years ago!

Yes, I get that a fairly heavy and none too small package to OZ gets pricy. More so post Covid as that seems to have screwed long distance cost big time because of container space prices.
From Italy to Spain is but a hop and courier competition fierce.

The development is mainly flowing sideways from dirt bikes as that still is a húge market in the smaller cil. capacities. It also explains why it is almost exclusively performance oriented. In the past century Enduro, ISDT at all, asked for more lower end tractable engines but that is no more

The same knówledge applies at lower end torque too though. It just needs a niche market manufacturer/enthusiast. Chapeau for Megadella.

An objective side note: In 1961 the MZ 125 ccc GP racer broke through the 200 hp/litre barrier. Yes sólely because of the expansion chamber technology.
Now that is available on line in kit form for vintage scooters of all things

It's very interesting that Egig when talking about his cylinders is describing them as "20/20" (not the actual figures which I can't recall), 20 PS and 20 Nm. Not that exactly, but as well as high hp figures, torque is rising as well. He says it's more important to him that the engines are easy to use with extremely broad power bands.
I think in many respects stories like this are due to sharing of information, people inspired by others and going on to develop further based on the learning of others.

Progressing insight.

And every once in a while a small step ahead is a breakthrough which others can depart from, improve upon next.

With our scooters a HUGE factor is that we, the average clients, now have more spending power that when we were faffing about as teenagers/starters. That means a viable market for specialists. A pushing/pulling power for improvement.
Looking at myself I will happily spend money on a box exhaust which would have supported my food for about a month back then.
In another perspective I now spend the same on my coffee hobby ffs
Anyway, we afficinados are now a viable market.

simply because it is só

Getting to reserve again, so about to go fourth tankful.
I hád planned to go Polini now but the engine is still noticeable loosening up so postponing till the néxt tank fill.
Will then do at least two fills with the Polini before I fit the Megadella (which has already been sent off towards me btw.) to get the jetting right for a fair comparison.

I've got 72.4mph with my VMC177 and Polini box.

As I observed I am not unhappy with the top speed. I am very aware that air resistance is exponential, especially for a scooter with a 185 cm rider sitting upright and being the equivalent of a parachute. Would be happy with a whiff more but mainly looking for (even) better pulling at low and mid range.

All a bit academic at the moment because the engine is acting up again