Posts tagged #Mini

Mini Racecar Test & Tune

I originally wrote this over a year ago, but never got around to posting it. I had planned a Test & Tune session at a nearby drag strip. My plan was to start with a bit of straight-line tuning & then measure a number of characteristics using roll-down tests & other techniques (coefficient of friction, wing & splitter drag, downforce, IC efficiency, etc.).

Unfortunately I didn't realize that the upper bands of tropical storm Hermine were approaching. I ran two brief runs at low boost levels to adjust the fuel table before it started to rain. I got a couple more brief runs in between rain bands, but puddles started forming & I wasn't able to do any WOT runs.

Here are a couple of pictures, as well as a very brief drive-by video:

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I'm planning on trying again in the near future. In the mean time, I'm going to go ahead and add some additional sensors:


- Three additional MAP sensors (one in the manifold *before* the turbo (!), one before the Supercharger (at wastegate takeoff), and one after the Supercharger/ before the intercooler).

- Four EGT sensors (one for each cylinder)

- Four linear sensors (one for each wheel)

To achieve this I have to add an expansion box to the ECU (i.e .basically another computer). This will give me a large number of additional inputs, as well as additional outputs. I'm thinking of using one of these outputs to actively control the supercharger bypass, and perhaps another one to drive a fuel injector to provide precise water/meth injection....

One bit of data I did get regarding the IC: the maximum temperature difference between the intake temp & ambient was less than 5 degrees. I wasn't able to compare this to the stock IC (too wet to put it on), but given the fact that I have *two* compressors, I think this is pretty darn good. I am still planning on doing a side-by-side comparison in session #2. And I will have MAP sensors on either side of the intercooler to measure pressure drop at the same time.

FYI I posted up a quick test video I did playing with audio levels & video recording with the camera down near the wheel. I'm trying to get better dynamic sound levels for recording the engine:

Pretty cool strobe effect with the wheel rotation...

And here is what it currently looks like:

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Posted on January 31, 2014 .

Mini Racecar Thermal Testing

Even with the new Aluminum cover I still need to protect the back of it to reduce the heat transfer to the engine. I purchased some high-tech heat reflection foil that is supposed to reflect 96% of the radiant heat:

But given the fact that the last protective material I put on the cover vaporized in a matter of minutes, I decided to first do a semi-quasi-scientific study on heat transfer to the cover with and without protection.

For reference, the melting on the cover from the Turbo looks like this:

To recreate the indirect heat of the turbo, I set up a propane torch approximately 1.5" from the cover. I placed a sheet of thin steel between them to convert the direct flame into a radiant source:

I used an IR temp sensor capable of measuring up to 1400F to measure various points. With a moderate flame I was able to produce a radiant spot about the size of a quarter.

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This in turn heated the cover to about 300F at the closest point. At this temperature the cover began to melt in about 1 Minute & produced a melting pattern very similar to the one caused by the Turbo:

I then tried re-running the test with a cover I had painted with a high-temp ceramic-embedded paint. This did seem to improve the behavior somewhat; it now took two minutes to get to the same level of melting:

Next I tried a section covered with the Foil:

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I ran the torch for over three minutes this time and it showed absolutely no signs of melting. Furthermore, I tried to measure the inside temperature (a bit tricky) & I believe it stayed around 100F. Finally, in true Mythbusters fashion I decided to "crank things up a bit". I moved the torch a bit closer together & increased the flame on the torch:

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With this setup the cover temperature reached 500F and the metal sheet got to 800F. I let it sit like this for over a minute. I only stopped it because it looked like the torch was about to burn through the metal sheet.

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The end result looks like this:

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i.e.....nothing. No bubbling, distortions, discolorations or anything else. Color me impressed. It's definitely going on the car!!


Posted on January 11, 2014 .

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:

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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.