Posts filed under Cars

Mini Racecar Turbo & Ignition Coils

 

I had an issue with the turbo starting to leak oil. Upon investigation I found that the turbo was heat spiking, causing it to wear prematurely. It appears that this is pretty common when you track after-market turbos that don't have water cooling.

So I decided to switch to water-cooling. You can order the turbo casing with or without the water coolant connectors. It's not really that difficult. You split off the tubes from the main line; they enter/exit 90 degress from the oil connections. You can see the red & blue connectors on the sides of the turbo in the picture below:

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The trickiest part was figuring out how to attach the braided lines into the existing coolant hoses...I finally found a reduction fitting that works well. And part of the tubing rises & falls right at the level of the overflow tank. So I adapted a gas sampling connector to act as a bleeder port. It works perfectly.

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The other issue I've had is that the ignition coil is too close to the turbo (see picture above). The connector & parts of the casing are beginning to melt. And my attempts to shield it have just made it worse by blocking the air flow around the turbo.

I've wanted to switch to one-coil-per-plug to provide more individual control of each cylinder anyways. This also solves the heat problem by moving the coils far away from the heat source. I looked into changing to coil-on-plug, but I could not find ones small enough to fit in the R53's spark plug tubes. However Motec mates a coil-near-plug variant:

Coil-near-plug.png

I purchased these & struggled with how to mount them in the Mini's very cramped engine bay. I finally came up with a simple but effective mounting scheme tying them together with small strips of aluminum:

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Because I don't have the top-mounted intercooler, this *just* fits between the head and injectors and attaches with a small bracket to the header bolts:

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Here's a picture of it mid-way through wiring them up:

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And here's what it looks like with all the wiring:

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And finally everything together:

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This has not only moved all the wiring away from the turbo, but it has opened up a better air path back to the turbo:

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And I'm thinking of mounting a curved metal sheet where the coil used to be to help direct the air flow between the valve cover & the turbo.

Ok, the car is running like a dream now....but I did have to fix two (of my) stupid mistakes first:

My first Homer-esque mistake I discovered immediately when I went to run the ignition tests with the ECU. I hooked up a spark tester to ignition output 1/cylinder1, told the ECU to fire the spark (2400 RPM @ 6ms dwell) and it worked great the first time!!! Same thing with output2/cylinder2, output3/cylinder3, output4/cylinder4!!..... dope! They're supposed to be wired in firing order!! Sigh. Check the book...no, I can't tell the ECU to change the firing order. Fortunately I just had to rearrange one control wire for 2,3 & 4...sorted!

Ok now everything works great! Great spark, everything in the right order, injectors running great, etc. etc. Finished reassembling everything, pushed the car out into the driveway, fire extinguisher handy, turn everything on, push the button - car turns over fine....but will not start. Nada. zip.

Hmmm....well, I know the ignition & injectors are working OK. Let's pull out a spark plug & check the spark - perfect! (actually the best I've ever seen it). Battery low? Ok charge it...no change. I was running a bit rich last time I started it, maybe I'm flooding it. Trying cutting fuel by 10%, 20%, 30%...nope. Ok, add fuel by 10%, 20%...nada. Tweak timing...zilch. Sudden fear: maybe I left a rag in the air intake!!! Frantic disassembly...no, nothing there...ack!! Bad fuel? Worked last time I was running it & haven't added fuel since then...rogue settings value change in the ECU? (it's happened before)...methodical search...nope. Major frustration.

As is often the case when I let my brain work on a problem in the background (i.e. when the silly conscious part is asleep) it quickly comes up with the solution. And as I was driving to work the nextday it explained it to me:

As I've mentioned before in a 4-cylinder, wasted spark engine there are two equally correct timing points that are separated by 360 degrees. Setting the GRIP to either of these two values will work equally well. However now that I have one-coil-per-plug, this is no longer the case.

I was 99% positive I had the correct value for the GRIP, but it's easy enough to check. The minute I got home from work, I pulled out the computer, changed one entry in the settings, flipped the switch...and it purred to life! Success!

My impression thus far is that the spark with these coils is amazing. It may be my imagination, but the spark is far more intense than I remember it being before. Just as an example, when I was running the initial tests I moved one spark plug wire from coil-to-coil. At one point I forgot to switch to the next coil. When I started the test, the spark jumped from center post of the previous coil to the closest metal contact point..over 1.5" away!

Posted on December 2, 2013 and filed under Cars.

Mini Racecar Tuning #1

 

Although BHS started doing the tuning in the shop, I ended up having to pretty much start from scratch & learn how to do it myself. FYI here are three great books I've found:

        How to Tune and Modify Engine Management Systems
                
by Jeff Hartman, Motorbooks Workshop.

       Dyno Testing and Tuning 
                 
by Harold Bettes, SA Design

       Engine Management Advanced Tuning 
              
by Greg Banish, SA Design

One of my key goals is to avoid some of the issues that have hit other highly customized Minis. In my opinion, a big challenge with tuning these engines comes from the inherent difficulty in tuning a small forced air engine for all the extreme environmental variations (summer/winter hot/cold dry/humid, altitude variations, etc.) - especially if you're trying to do it all in a single tuning session. What complicates this even more are the small but significant differences between running the car on a dyno vs. on the road/track.

So my approach has been twofold: 1) capture as much real-time, real-world information as possible (including weather conditions) , and 2) develop techniques for using this data to quickly and precisely adjust the tuning maps to match the real-world conditions.

To achieve this the engine has a large number of sensors installed. Three of the most important are the wideband Lambda, EGT, and knock sensor. The Lambda is the most important way to check the fuel maps. And the EGT and knock sensors are critical for adjusting the timing, as well as providing key indicators for other potential issues.

Getting the Lambda & EGT working was easy with off-the-shelf parts, but no such luck with the knock sensor. It requires a bandpass amplifier tuned to match the specific engine configuration. I'm working on designing my own DAC-based circuit for this, but in the mean time I found an aftermarket box that seems to be working well. It appears as the small circuit board at the bottom of the wires below (fyi the wiring in this picture looks worse than it does in real life...and I'm working on simplifying it)

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Here is an example of the kind of log data I get out of a run:

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Since the main tuning map is a function of RPM and MAP, I created two graphs corresponding to the instantaneous values of these sensors at each RPM/MAP point. The value at each point is represented by a color-coded dot. The color coding is structured to make problem areas visibly stand out. These graphs are automatically generated from the logged sensor data. So after each run I can immediately see where the maps need to be adjusted. The following picture shows Lambda as a function of RPM/Boost, and EGT as a function of RPM/Boost. RPM is the X axis & boost is the Y axis:

Old_Lambda_Graphs.jpg

Over the next couple of months I took the car to a couple of one-day track sessions to do additional tuning & adjustments, as well as making sure everything is running reliably before I take it to a multi-day event.

One of the features the MoteC supports is boost control using a solenoid connected to the pressure line going to the wastegate. The wiring for the solenoid was not quite right, but I finally fixed it. So the next step was to set up the parameters for the control algorithm.

The first step in that process is to find the "target" duty cycle. This is done by setting a fixed duty cycle. I didn't want to accidentally make the boost too high, so I set a 35% duty cycle to begin with. This increased the maximum boost by about 5psi. to about 20psi. (see plots below). I then had to make some adjustments to the timing & fuel tables at those boost levels.

Old Plot:

Old_Lambda_Graphs (1).jpg

New Plot:

New_Lambda_Maps.jpg

Because I just used a fixed duty cycle, the graph is shifted to the right. Once I set up the PID controller properly, I should be able to get it to boost at least along the blue line drawn into the graph below. This graph shows the new data overlayed on the old data (in black):

Lambda_Diff_Target.jpg

I did have an issue on the second run session where the engine cut out briefly. I traced it to some water that was shorting out the sync signal. When I cleaned the contact & reassembled it, the problem didn't occur again.

Also, this is also the first run I've had a chance to log GPS data from the AIM data logger. This software is very different from the analysis software I've used before, so I'm still getting used to it.

Just for fun I tried out the engine performance analysis view. By entering the vehicle weight (including driver), frontal area & drag coefficient, it calculates HP & TQ to the ground.

Analysis_Screen.jpg

In theory this says I'm making 315 HP & 277 ft/lb of torque to the ground...BUT I'm very doubtful of those numbers at this stage. I'm planning on taking the car to the dyno in the near future; that'll give me something to compare this to.

Additional Tuning Tools

I mentioned previously I was playing with using external applications to take logged engine & environmental data to adjust the various tuning parameters on the Motec. To play with this idea I made an Excel spreadsheet that combines the logged data with any of the tuning parameters I want and applies a transformation/correction. To begin with I'm testing the idea using the fuel table.

The first tab of the spreadsheet is a dump from the logging output of the Motec. The second data tab is the log from the bluetooth weatherstation I'm using to continuously grab environment data during the day:

Engine_Log_Data.jpg
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The next tab has the input tuning parameters - in this case the original fuel table used during the run:

Original_Fuel_Table.jpg

I then apply a filter to the log data. In this case I'm removing all deceleration data (the lambdas in those areas will skew the analysis):

Filtered_Data.jpg

The next tab is a pivot table summarizing the measured lambda values at each RPM and MAP point. Since not all RPM/MAP combinations were measured, there are a number of holes in this table (it fills in at the higher RPMs):

Lambda_Table.jpg

The next tab is the correction table. For cells with a measured value, this has the actual correction factor to apply to achieve the desired lambda value. For cells that don't have measured data, the value is interpolated from nearby data. In some cases I override certain cells where I don't think the masurements were accurate, or to help smooth out between the sample points:

Correction_Table.jpg

All of this results in the output tuning table. In this case you can see some interesting additional hills & valleys added to the fuel table:

New_Fuel_Table.jpg

This data is then re-uploaded to the Motec. If necessary this cycle can be repeated multiple times to optimize the solution

After the fuel table there's timing, short-term corrections, long-term corrections, etc. etc. With some variation the same approach can be applied to all of them

Pretty cool, eh?

 

Posted on November 20, 2013 and filed under Cars.

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:

SuperTurbo_System_Diagram_v2.jpg

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  ):

Click the image to open in full size.

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.