Modern Vespa

Hundreds (thousands?) of GTS owners have fitted the Malossi V4 kit which makes their scooters slightly more powerful than the HPE. Hundreds have also fitted the Malossi ForceMaster ECU override which pushes the rev limit up by another 1000 rpm.

I have never heard of any problems caused by over-revving as a result of these mods.

Stromrider - I generally find your posts about engines to be interesting and thought provoking. I’ve been building engines and transmissions (and a host of other things) since the early ‘80’s and am a six time certified Master Tech, though no longer professionally. Based on that, unless design engineers at Piaggio have specifically told you the speed limiter was put in place because the engine can’t handle higher revs i think your post is highly speculative. As you know, even with the Kubler ring installed the engine still has a rev limiter. It is not reliant upon the speed limiter to protect the engine from over rev. Furthermore, due to variance in RPM at any fixed speed based solely on throttle input and angle of climb or descent (characteristics inherent in the CVT design) attempting to protect an engine from over rev based on vehicle speed instead of engine speed would be both ineffective and silly.

I’d like to see some proof to back up your theory. Otherwise I remain convinced the speed limiter has nothing to do with engine protection, and has more to do with the fact that large frame Vespas have always had a top speed in the neighborhood of 75 mph. Realizing this version had enough power to go significantly faster Piaggio programmed in a speed limiting function.

Yep, but be careful WEB-Tech. You will lose the up to 10% factory over read put there by the manufacturer under international law to prevent you getting a ticket, which in reality could mean that some days you will likely be going faster than you are actually being told by your speedo. Few bikes actually have a 10% over read. And if they do it's because of lots of variables.

For the benefit of folks who don't know, your speedo reading accuracy will vary from day to day, season to season. Huge variables like ambient temperature, tyre wear, rider weight, how much fuel you have on board, tyre pressures etc etc (there are more but can't speak of them here as it's technical), and indeed the speed at which you are riding all make the speedo read differently from day to day. Speedos even read differently at the start and end of a journey and this alone can amount to a difference of several percent under some circumstances depending on ambient temp. Some of these variable only make a small difference, but some make a very big difference.

My GTS has on average a 3-5% over read. It varies depending on the speed at which I ride and for how long, plus all the other variables that we all suffer. At 60mph I'm actually doing 57-58mph. It's always been that way. All my bikes are and have been quite accurate with their speedo reading.

From what I've been told by an agent selling the Kublar ring, it definitely removes the up to 10% over read put there by the manufacturers under international law (to prevent you getting a ticket), so it will move your speedo reading nearer to accuracy, some days! There is a but though! If an HPE bike is similar to my GTS, and it likely will be, with a Kublar ring fitted and from what I'm being told about this ring, you may find your speedo will be under reading by quite some way on some occasions and you will likely get a ticket as some point. 60mph reading could be 65mph or more in reality if the variables conspire against you. Most folks don't know how to test their speedo for accuracy. They think you just hook up your cell phone with a gps speed reader on it and do the test. It doesn't actually work like that and is much more involved. You want more than just a snap shot. Testing takes several hours to get an accurate reading doing it that way as your speedo accuracy can vary at the start and finish of each journey. It will vary again the next day, or the next month or whenever the weather or temperature changes. It can increase or decrease in accuracy by several percent. I see on here folks claiming their speedo is 10% out. It might have been that day under those circumstances that prevailed just then. But 10% is actually quite a rare figure, it's normally not that much and usually around half that figure on modern bikes. And of course, some bikes are worse than others. Also the owner is maybe not checking tyre pressures or is running them at the wrong pressures or tyres are worn. It can indicate other issues too.

So if you fit a Kublar don't take it for granted the speedo is going to be accurate. Accurate speedo readings really don't exist on road bikes inspite of what some folks say.

Hi bosco, nice to talk with you. I understand where you are coming from.

Yeah what I am saying is if the engine is going past the 75mph mark the engine is over revving and going past the engineers designed speed. The rev limiter is preventing the motor going faster at 75mph because the design engineers have altered the rev limit ceiling so it's lower. Lower than on the earlier motors. Earlier motors have the rev limiter coming into play at around 81-83mph indicated (I've seen both those speeds trigger the rev limiter) and it will vary from bike to bike due to lots of variables. On the HPE they have done this to maintain long term mechanical reliability. This is needed when you produce a mass produced engine with substantially increased power based upon an older design (although it's perfectly good to do this). Don't forget the HPE has 18% more torque (the engines actual power) and 12% more horsepower (a measure of how quickly the engine can produce that power). That is substantially more than the euro3/4 motors. But it comes at the cost of less top speed to protect the motor.

If you fit the ring it fools the ecu into thinking you are going slower than you actually are so it continues to let the revs build and therefore the bike goes faster. The gearing of the variator, belt position etc etc is not affected and cannot be affected by the ring. The HPE is running in it's highest gear position at 75mph so the only way it can go faster is for the motor to rev past it's designed set speed as set by the design engineers. This means it is over revving, the rev limiter speed restriction has been raised.

I've not had the HPE on the dyno yet or seen one being dyno'd and I haven't had the chance to take one flat out yet, but I bet at 75mph the motor seems to tighten and then doesn't want to go faster. That's because the "Rev Limiter" is reducing fuel to the injector and retarding the ignition. It also eventually probably starts to cut out shortly after in bursts to let you know to back off the throttle to prevent engine damage. The rev limiter on the HPE is much more subtle than on the earlier bikes which almost straight away go to engine cut out mode. That's how rev limiters work. There is no speed limiter as such, only the rev limiter. Folks often confuse the two. Trucks have speed limiters and these can work a bit differently and can even apply the brakes to maintain the correct speed even downhill.

Fitting the ring! It's a bonus if it makes the speedo a bit more accurate, but you should take that with a pinch of salt as it's impossible to make a completely accurate speedo for everyday use because of all the variable that affect speedos and talked about endlessly in other threads. But no doubt it is more accurate but at the expense that you may end up going faster than the speedo is registering because you have lost the under read safety zone specified by manufacturers.

That said and as I mention in an earlier post, I don't think the ring will do any actual harm if one is not using that top end performance too regularly. I'd fit one if I had the HPE, but then maybe I wouldn't. Little point in my opinion. If you want to go above 75mph on a regular basis, get a bigger bike!

I've heard the stories about "Europe requiring a lower speed reading," but haven't seen that written anywhere other than forums. Seems suspect to me. I could believe manufacturers build that in to make customers feel better about how fast their scoots go.

Piaggio has decided that as a mass produced scooter engine that is often ridden flat out by it's owners, the HPE engine is at risk if it is allowed to rev out to the same extent as the lower powered euro3/4 GTS bikes. So giving it more power, but lowering the rev ceiling to make sure of avoiding problems down the road is quite normal. I've done this myself when revising and developing some types of engine designs for manufacturers. This is quite common. Manufacturers don't want their bikes to get a bad reputation for unreliability. I haven't checked the final drive gears to see if they are the same as the previous bikes but even if the HPE has the same gearing engineers have in my opinion taken a prudent step to protect the engine.

They have decided not to let the engine rev out to the same extent as the previous versions for one reason only, reliability. Retaining that on a mass produced engine is vital. The rev limiter (the HPE does not have a speed limiter) is reached very quickly on the HPE and that is a signal that is important to take note of. Manufacturers don't do that without reason. Some of that reasoning is no doubt due to the small wheels but the engine will be the most important factor here.

With the Kubler ring fitted, the engine still has it's rev limiter but it will be coming in to play much later when the engine is well beyond it's designed and intended revs. Now on the older euro3/4 bikes this is clearly not an issue as the motors are very robust in that format. The HPE, maybe not so much.

The Malossified euro3/4 bikes are fun, but eventually will have a shorter overall life if ridden with gusto. They put out much much more power and at much higher rpm. Something the engines were never intended to do. It will shorten the engines life, but by how much we are not sure just yet.

Piaggio don't take risks. They cannot afford to do so. They won't go for big power and big speed figures on an engine such as the GTS bikes have. It's not suitable. But the HPE is only 1mph slower than the earlier bikes. It's just the earlier bikes can rev out more with that rev limiter set very high by comparison to the HPE. Remember though, the HPE is a totally revised engine and is not designed to rev out as much as the earlier bikes.

Not trying to pour cold water on the Kubler ring, but just making sure everyone understands how this thing works. It's ok to fit one in my opinion but care is needed. Understand what the consequences are for warranty and maybe engine life into the future.

Malsosi claim that their ForceMaster 3 removes the speed limiter and extends the rev limit by 1000rpm. So they disagree with Strom about the existence of a speed limiter.

But I gather from reports in other countries that not all HPE models have a speed limiter. Maybe only in Europe? Been Googling it but cannot find anything.

Ask Malossi, they have an information form and are very willing to give information.

Malsosi claim that their ForceMaster 3 removes the speed limiter and extends the rev limit by 1000rpm. So they disagree with Strom about the existence of a speed limiter.

But I gather from reports in other countries that not all HPE models have a speed limiter. Maybe only in Europe? Been Googling it but cannot find anything.

Really? When my ForceMaster 2 didn't work (TPS setting failed) I couldn't get any response from them. And when I approached SIP, where I had bought it, they just referred me to their user forum. No help at all. My ForceMaster is lying in a drawer in my shed, useless.

They sell us little black boxes and offer no support at all.

Whenever i contacted them (recently for the 183cc modification for my scooter) they replied.

I found them ok too! Maybe the European SIP is better than the US one.

There must be something wrong with your bike Steve if it showed a speed under read against your GPS. By law your Speedo must over read.

As mention earlier the rev limiter gets information from several sources but makes the final decision to cut revs based upon crankshaft revs only. It can slow you based upon speed only though, acting in a similar way to a "speed limiter". Thanks for posting that info though.