Mini Racecar Introduction

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Early in 2004 I purchased a brand-new Mini Cooper S.  Before the Mini I had not modified or worked on my cars - except out of necessity. 

 But starting with this car i became more interested in engine tuning, ECUs, wiring, sensors, and went on to racecar construction, aerodynamics, chemistry, welding, thermodynamics, materials fabrication, etc. In the end I have transformed the car into a dedicated track car.  This first post provides an overview of the early developments.  Subsequent posts will focus on specific areas of work/improvement.

Stage 1

  The car started out as a “normal” heavily modified 2004 Mini. I started with the standard bolt-on aftermarket stuff: GRS intercooler, Detroit Tuned brake kit, Leida suspension, better seats, etc. etc.

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Stage 2

The madness started to increase when I found a local shop (BHS). They specialized in getting high-end BMWs to insane power levels. We started with simple stuff (Quaife LSD, lightened flywheel, etc.). Along the way we went so far as to replace the internals with lightweight, high-strength, balanced components:

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 Stage 3

Things really started getting crazy when I acquired components of a twin-charge (Supercharger+Turbo) kit. With a good bit of rework, BHS was able to produce a well-integrated system with a very non-turboesque behavior. Here is a picture of the installation at that point, including my crude but effective temporary heat shield:

Here is a system diagram I put together showing the interconnections and control of the twin-charge system:

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I have been pretty consistent with getting a dyno run on the same machine after each modification, so I have a pretty good history of the performance gains at each stage. With the addition of the turbo, it progressed to a *much* higher level: 298whp/234ft-lb tq.

The really phenomenal thing about this is the tabletop-flat torque curve through most of the power band, and the consistency from run-to-run. It behaves & sounds much more like a bigger engine than a turbo.

I had the chance to try the car out on the track for the first time at aTexas BMWCCA DE event in 2007. The event was held at the MSRC track near Dallas. It's a technical track with medium length straights that favors cornering over power, so I wasn't expecting it to be magically different than before.

Net net, the car was *fantastic*. Even though it was the first outing & I wasn't pushing the car to the limit, I improved upon my best lap time for that track by over two seconds.

And it really felt like a very different car....which also means that I have to totally relearn how to drive it. There were at least two turns that I used to be on full-throttle at the apex that I couldn't anymore because I was spinning *both* of the front wheels - even with a quaife differential and wide sticky tires!

To get a feeling for it yourself, here's a video from one of the sessions. FYI the Miata in the video is a heavily modified with a Turbo...they don't usually take me that long to pass :-)

Note: the audio is a bit deceptive. With the waste gate open, the car is *very* loud. So I had to really turn down the Mic input...which means you don't hear much of the normal engine sound until the Turbo is fully spooled up:

http://www.youtube.com/watch?v=uh6DDMsmgPc

At that point I had a data logger hooked up to gather standard GPS information as well as RPMS, Oil pressure/temp, boost, A/F Ratio, etc. Just to give you a sample, here is a graph of the boost vs. speed for one lap:

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I also experimented with a math channel that calculates deviation from "theoretical optimum power delivery". With a perfect car & driver this graph should be zero everywhere.

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Overlaying this run with one from the previous year, you can see how the peaks are generally sharper indicating faster acceleration/deceleration. But in other areas it's actually worse...mainly because I'm wasting too much time spinning the wheels and/or being less consistent through the turns...more confirmation that the biggest thing needing improvement now is the nut behind the wheel :-) :

Stage 4a

I ran it this way for about a year before the car developed an electrical fault. At this point I decided to make it into a track-only car & get rid of the stock computer. With BHS's help, we began stripping the car, filling in the sunroof, and adding new seats & rollbar:

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I particularly like this picture up through the roof with the sunroof assembly removed:

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We chose to replace the ECU with a MoTec race computer.  There were a number of challenges in this process. The first challenge was driven by our decision to try to reuse existing Mini sensors instead of buying new (and expensive) MoteC sensors. It seemed logical (and cheaper) to try to reuse as much as possible...but in the end trying to figure out the behavior and properly calibrate the sensors was not worth the effort. Almost all of the sensors on the car were ultimately replaced with MoteC units.

The second challenge was our decision to try to keep the electric throttle controls rather than switching to a mechanical throttle. The MoteC has an electric throttle control package, but it is very poorly documented. It took a few tries to get the wiring and software working correctly. But having the electric control enables a whole bunch of valuable ECU capabilities (traction control, idle control, etc.)

The third challenge was in getting the cam sync sensor working properly. We first tried using the stock HAL effect sensor, but couldn't get it to work. We switched to a MoteC magnetic sensor, but it was difficult to adjust & got out-of-sync frequently due to noise. Finally we got the stock HAL sensor working properly. The timing sync is rock-solid now.

One of the last things we added was a front-mount intercooler from GRS. I purchased a top-mount GRS intercooler early-on and have had excellent success with it. But having both the turbo+supercharger was a bit much for it. The front-mount version is a piece of art:

Stage 4b

Unfortunately BHS closed down early in 2009, so I had to complete the wiring & various mechanical/interior/finish details myself. To further enhance the ability to capture & edit the settings, I mounted an additional embedded Windows XP computer in the car permanently connected to the ECU and GPS logger. This also enables the use of low-cost USB-based cameras for video recording. And by attaching a USB WIFI dongle, I can now tune the car wirelessly from a laptop (as well as watching the video wirelessly in real time  ):

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Finally, I finished cutting & installing the aluminum floor plates. Even though I made a cardboard template, I had a few issues with fitment...but I think it turned out good enough:

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I've already gotten a lot of positive feedback on the floor & interior in general. It feels minimal, but very functional.

Posted on October 23, 2013 and filed under Cars.