Modern Vespa

Hello All,

Just from a general improvement to the standard of the production line bikes, I wondered if anyone had done a comparison on the dyno of:
1) Euro 4 bike against Euro 4 bike with a Euro 3 or below standard silencer ( I ask as I believe the Euro 4 silencer has an additional cat installed). I know the Euro 5 has a different downpipe, etc with an additional cat in the mid pipe too.

2) 140/70/12 rear tyre Vs standard 130/70/12, with and without the speed ring swap. I t would be nice to see how the slight upgear affects general performance.

3) Mike Holland's airbox mod on the Hpe Vs standard.

Plus obviously a bike with all three simple mods which may just free up the engine and transmission a little.

Cheers.

Number 1, unless you remove the cat completely will not do anything to improve gas flow

Number 2 is not really an improvement on the gearing at all. It is just a 10mm wider tyre.. You need to change the rim size from 12" to 13"or the tyre wall from 70 to 80 if you want to change the gearing.. Going from 130 to 140 you have just gain extra weight and not much else..

The HPE has a very different air filter box, and my air box mod is not relevant anymore. I don't think anyone has tried an open air filter on an HPE yet.

I believe the air box change is only in the Asia Pacific models not the European or North American

Thank you for the responses.

Mike - Not sure about the US and SPAC regional changes, but the Euro 4 scooter have the same style air box as before, so I'll try one of my spare modified airbox units with a Malossi red/double red filter and an ECU reset, then maybe the TC o2 emulator afterwards......😂🤣😂

Burt37 - 1) I was asking if anyone has checked as the exhausts look very similar, but had been informed the Euro 4 has a more restrictive internal catalyst, which if an older style (Euro 3 backwards) was installed and the ECU reset may offer a little improvement, especially when combined with other tweaks.

2)I'm not sure you understand tyre size/ratios as moving from a 130/70/12 to a 140/70/12 is approx. 2-3% upgear, as you add 15mm to the total diameter and 45mm to the circumference.

As I stated I'm gonna just go back and check these changes to see how the Euro 4 bike reacts. Just glad I didn't hold on for a Euro 5 as they seem to the next level of restrictive.

I was actually referring to the part of your post: So I thought you meant to choosing between having the old system with one cat or the new that like you said could have more restrictions. Hence, my reply that unless you remove the cat completely it won't make much difference between the two..

Regarding the tyre size, yes you are right, the 140 does give you a slight bigger diameter, but I think you will eventually find, that is not a noticeable advantage as mounting a 13"rims like most people do when they want to achieve a different gear ratio.. That, at least was my experience...