Subaru Impreza Pikes Peak

30 Nov 2014 | Author: | Comments Off on Subaru Impreza Pikes Peak

Pitch study

I apologize for the lack of recent updates, but the project kept me very busy, and it is now in its closing stages with the redaction of the final report. I still wanted to present some trends for the model I have created, and I will finish with few more pictures in a next entry. It will be then time to move on to other projects, one of which has been shown here.

A hint: some like call it #8220;Hulk#8221; due to its bright colour!

In the meantime, here are some more results of the Pikes Peak Subaru I have created. As a reminder, I took the Pikes Peak v2 shown earlier on, and proceeded to a pitch analysis. I simply varied the pitch angle from -1.5[°] to 1.5[°]. Below are the aerodynamic coefficients obtained:

This follows the theory, and makes sense of course because the diffuser under the front splitter only works efficiently if close to the ground, to take advantage of the so called #8220;ground effect#8221;. This kind of behaviour can be seen also if the whole ride height is reduced, until the car gets too close to the ground and suffer from blockage. The drag coefficient remains fairly constant and indicates that the rear wing#8217;s angle of attack change due to pitch does not cause stall.

Let#8217;s take a look now at the downforce repartition:

As it was seen earlier with the Pikes Peak v2 that enhanced the front downforce balance over v1, further pitching increases the balance even more. But a large problem occurs with negative pitching angle (nose of the car up). At -1.5[°] the car loses almost all balance at the front, which is a major issue.

Imagine the driver braking, taking the corner, and accelerating out of it. The car will understeer a lot. The problem with devices that work in ground effect is their high sensitivity to ride height, as were the Formula 1 cars of the 1980s.

A way to counteract the loss of aero balance at the front could be the use of anti-squat system or stiffen the suspension to reduce the body pitch and roll.

A large front wing across the front bumper would have provided a lot of downforce as well, and not suffered from this pitch sensitivity issue, but the scope of the project forbids the blockage of the intercooler. News from the Roger Clark Motorsport Subaru Impreza (which was shown in an earlier blog entry) showed issues with cooling, which gives sense to the scope I have defined prior to the project.

Therefore, a way to drive this car (after suspension tuning of course) is to use trail braking as much as possible. By doing so, the driver would take advantage of the extra downforce given by a pitch angle to turn the car early into the corner, and then accelerate while being in a straight line as much as possible. Late apex driving is of course forbidden!

Further refinement of the front splitter diffuser could be made, but it is important not to forget that the base car is a road car and that chassis modifications cannot be made.

The next entry will be about yaw and should come soon!

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