As shipped to US Aprilia Dealers, the SR50 Factory is mechanically and electrically restricted to meet European homologation requirements. In the US we do not have to meet those requirements therefore the first step in tuning the SR50 is to remove the electrical and mechanical restrictions that were installed at the factory. The 1999-2007 Aprilia SR50 with the Morini DiTech engine has 2 restrictions, the 2009 and forward SR50 with the Piaggio engine has 3.
The first restriction is in the programming of the ECU (Electronic Control Module). The Factory loaded software delivers less fuel and an ignition timing curve that limits the horse power to about 3.8 at the rear wheel.
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The software can be updated to what is known as "Development" by your Aprilia Dealer via on-board by taking them your SR50 or High Gain Tuning via off-board by shipping them your ECU. You may experience difficulty in getting the Aprilia Dealer to perform this function. Many owners are being told lately that they either cannot derestrict the 2009 and newer SR50's or that they do not need to be derestricted because they are now being shipped to the US without restrictions. If the Dealer chooses not to or cannot do this, that is their choice. To say they are being shipped to the US Aprilia Dealers already derestricted is false. The 2009 Piaggio Purejet and forward models without a doubt perform better than the Franco Morini based engine which may have some believing they are now arriving without restrictions.
This video shows the derestricting of a 2009 SR50 ECU via the off-board method. This ECU was shipped to High Gain Tuning like many others because the Aprilia Dealer said it could not be done.
Here are the results... over .6 Horse Power increase just by derestricting the ECU! The road speed of the restricted SR50 is about 45 mph tops. We also gained a little speed but our next derestriction will help much more.
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The next 2 restrictions that can be removed are mechanical. One is a restrictor plate that sits right under the intake manifold, yup... just like NASCAR and for the same purpose, to limit air flow. The restrictor plate has a single 15mm opening, the smallest opening found anywhere in the air induction system. We have found in Dyno testing that this 15mm restriction has no affect at the 49cc displacement. This plate is only found on the 2009 and newer Piaggio engine.
The second restriction is a small spacer, only 2.3mm thick that sits sandwiched between the variator pulley halves limiting how far they can come together. This mechanical limitation stops the drive belt from making a full transition up the variator and down into the rear fixed pulley. Here's a pic of the 2 mechanical restrictions removed as compared to a dime.
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This is the result of removing the variator spacer, a 7-8 mile per hour increase.
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This is a Dyno graph showing the results of all 3 restrictions removed. Six tenths of a horse power increase and 10 more miles per hour. It should also be noted that your 0-45 mph times will improve by 2 full seconds.
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