Alex builds a Quattrini 252ccm Vespa engine 4 - stage 2 with exhaust test

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In the fourth part of our little blog series we make the following changes to our test engine:

The cylinder is attached at the foot with two 1mm Spacers increased by a further 2mm compared to level 0.5. This changes the steering angle of the transfer channels from 124° to 126°. The outlet is adjusted to a control angle of 190° by milling. To do this, the outlet in the cylinder was raised by 1.8mm. The outlet width remains unchanged at 57%.

 

The first attempts are made with the Elron

 

A little more nervous exhaust systems would show a clear shift in the direction of performance with the changes made, but the Elron is almost unimpressed by the specifications of the cylinder and retains control over the characteristics of the engine. A slight increase in the maximum values ​​after the decimal point only indicates that the Elron has noticed that the cylinder is sending a clearer signal through the exhaust. However, the maximum torque remains at the same level as in the first construction stage.
The available speed range is reduced by 500 rpm to 3540 rpm.

 

Polini box

 

As a box exhaust, the Polini exhaust system reacts more as expected. Similar to the Elron, the can from Italy only shows small reactions. The lower effective compression makes the curve dip a bit in the rise between 4000 rpm and 6200 rpm. The system converts the slightly increased time cross-section at the outlet window with a gain of just over one horsepower at peak.
The maximum torque remains the same at 35.2Nm and is only shifted by a few hundred revolutions in the direction of higher speeds.
With a bandwidth of 3800 revolutions, the Polini system is slightly behind stage 2, but this test shows that the box does not necessarily prefer the very small steering angle. In a direct comparison to stage 1, the bandwidth and maximum values ​​have increased significantly.

 

 

 

JL left hand / JL performance

 

Our test subject had a short break in the previous construction stage due to appointments away from home; but now plays again in the third construction stage. So here is the comparison between levels 1 and 2.
This also shows how clearly an exhaust can behave when it is operated from other steering angles. The JL, which is considered good-natured, turns out to be a very approachable partner in the search for performance.
At the top, the JL provides almost five and a half more horses and climbs over the 36PS line in the graph. The torque remains at 32.6Nm at the same level as in the first attempt. However, the torque extends over a much wider range - beyond 7000rpm. The performance peak is reached with 36.4PS at 8400rpm. The JL falls below the 25 HP line considered in the bandwidth only beyond 9600 rpm and can therefore not be described as a lazy speed. In general, the graph shifts significantly in the direction of higher speeds. With a bandwidth of only 3400 revolutions, the JL even lags behind the Elron and brings up the rear in terms of bandwidth in this construction stage.

 

Scooter and Service Newline

 

The edgy powerhouse from the north feels really comfortable in this expansion stage and takes two best values ​​with it.
There are no notable changes in the rise in the newline, but it does quite a bit due to the larger advance angle in the engine speed range. With 37.3Nm, it takes the top position in terms of torque in the third construction stage. The available speed range is narrower compared to the previous tests, but here too the Newline achieves a range of 4000 revolutions. With these values, considerations germinate after a longer primary with 24-60 ...

 

Nessie

 

Like the Elron, the sea monster from Posch Performance is not quite sure what to do with the changed control angles. Maximum torque remains the same and peak power increases by one horsepower. While the Nessie was still way ahead in level 1 with 4300 rpm in terms of bandwidth, the available speed range in level three is a bit on the dip station and is in the upper midfield with 3700 rpm.

 

 

 

Racing Resi

 

The Racing Resi taste the changes better. Rather devoted to the higher control angles, the Resi develops one more horsepower at the top and adds torque, which hardly affects the bandwidth on the 25hp line. In absolute terms, the Resi holds the position of the highest peak power with 38.9 hp in this level. We are slowly approaching the 40hp mark with the expansion stages.

 

 

Lakers

 

 

With 126° to 190°, the Lakers are not yet playing in their comfort zone. Although it also clearly converts the changed control angles into performance. With 38.4 hp at the top, it is only just behind the Resi. With a speed range of 3700 rpm, which already extends to 10.100 rpm, the Lakers shows where the journey can go with suitable peripherals.

Here is an overview of the results. Best values ​​are highlighted in green.