Tuning on the off-week

Suspicious of missing out on some straightaway speed, I sought the advice of one of the experienced club members.  We discussed several ideas to explore but settled on doing a leakdown check on the engine.

The process is pretty simple.  You take the cam out of the operation by removing the rocker arms.  This ensures that the valves stay seated (closed) during the test.  Compressed air is introduced through the spark plug hole and we check to see where it tries to get out.

It is normal for the rings on the piston to leak some as they do not form an airtight seal but you should not hear air coming out of the exhaust pipe or the carburetor throat.  During the test on our engine, we could hear a small amount of leakage through the exhaust.  Although it is was detectable, my friend assured me that it was insignificant on the track.  What else could I try?

Spark plugs? I have been running a conventional plug like the one pictured here.

This has the standard ground and I was diligently keeping the gap set properly.  No surprises here.  What about this stuff I read in the forums about a great racing plug for the Animal?  I decided to give it a try.  It has a cut back ground to increase the exposure to the spark.  This is the plug I had in when I visited my friend for the leakdown test.

My friend pulled out yet another upgrade to the plug.  It is radically different and offers even more exposure.  This is similar to what is used in some aircraft engines.  Apparently, it is legal to run so, we will give it a try.

Another upgrade he recommended was a larger air cleaner assembly.  This picture is a side-by-side of the new verses the old.  Obviously, the new has more surface area and will have less restriction.  With the larger restrictor plate, he claimed that this could make a difference for us.  The elongated base also acts as a semi-velocity stack to leverage the inertia if the intake air to "pack" molecules in the engine.

Finally I replaced the drive chain as I understand an old chain can increase drag.  With the stretch between rollers, the rollers don't fit nicely between the teeth and take slightly more power to engage.

With the new air cleaner installed I found it interferes with the right rear tire.  I may have to get creative but for now, I'll have to run the old air cleaner.

I'm again on-shift for the next race but may still be able to get a friend to swap.  I'm looking forward to see if any of this makes a difference.

Race #3

I got a break and found a co-worker willing to trade shifts with me so we could go racing.  I was interested to see if any of my fine-tuning would pay dividends on-track.

The weather was beautiful - sunny, mid-seventies and a light breeze.  It couldn't have been more pleasant unless you could magically make the pollen go away.  There were a total of six in Lian's class ready to race so we had some good competition on the track.

The practice sessions went pretty well and Lian was keeping pace with the rest but it was hard to tell who was fast and who was just riding along.  Lian admitted that she wasn't going hard on the first session and her best time was 22.20 seconds.  She backed that up with a better effort during the second session with a 21.76 second lap.  She complained that even driving hard didn't get her as quick as some of the faster kids on the long straight.

For the heat races, Lian started 4th and 3rd.  In the first heat, Lian was passed at the start by the 5th place racer but held onto 5th and put up some good lap times.  Her best three are below.

I should note here that one of the competitors was a relative rookie and was not moving fast.  He started behind Lian in the first heat but he started on the pole in the Heat 2 - directly in front of her.  When the green flag waved, the outside line went and the 5th place starter followed.  Lian had to wait for them to clear before she could attempt a pass.  She was less aggressive than the other racers and was not confident that she could make a clean pass although she knew she was faster. She was hoping for a blue flag to wave but it never came and Lian finished in the back.

Here she is on the starting grid sporting her new drivers jacket and helmet.  We ordered a dark visor because there are many sunny days ahead...

Starting in the back of the feature, Lian managed to get past that slower driver at the start.  Later that first lap, the 3rd and 4th place drivers bumped causing one to slide wide in a turn and stop.  Lian slipped past cleanly and held on for a 4th place finish.

Despite my efforts, Lian still feels that she is down on power at the end of the straight.  I've discussed this with a few other crew chiefs and I'm hearing mixed signals.  Some don't see that there is a difference on the track, others suggest leakdown testing on the engine to see if a valve is leaking.  I'm even considering a new engine to take any doubt out of the issue.  I'll let you know what I decide in my next post.

Race #2 - washout

Not much to write here beyond the title.  We never even went out on the track for morning practice.  We hoped to at least get the heat races in before the rain started but it arrived earlier than forecast and dampened the track before registration opened.

We made a few changes after last race.  I tightened the valve lash on both the intake and exhaust valves (set at a "tight" 0.002" gap). Installed a cutback racing spark plug and adjusted the carb to a little slower idle but set the mixture so it is a little more responsive.

I will have to let you know how these changes work out next time we make it to the track.  I have to work next race (May 5) and because we are short-handed, I can't get anyone to swap with me.  It's going to be a while before we get to the track.

Points Race #1 of 2013

Back to racing!

We were able to practice the day before.  This gave Lian a chance to get used to the new set-up an brake-in the new tires.  We bought new wheels and tires all round to better operate with the increased weight and power.  Fast laps in this class are around 21.15 to 21.30 and Lian ran as fast as 22.30 so we knew we needed to get quicker but it was not a bad place to start.

We got to the track on Sunday and unloaded under cool, breezy conditions.  The sun kept things comfortable but the wind picked-up as the day wore-on.  We all eventually got cold but got some good track time.

Race day we got Lian out on the track for both practices to get some all important laps in before her first race.  Here she is waiting her turn before the second practice.

Practice went well but we were disappointed that only two other racers in her class showed-up to run the race so we were not able to compare Lian's times with many others.  Lian got plenty of complements on the new look of her kart.  The club photographer got several pictures.  He and I agreed that that was the day to get them because the graphics and body will never look this good again after the first competitive race!

The heats went well.  Lian started second of three in both and finished second and third in each.  We noted that she was turning rpm at 6709 on her quickest lap 22.98 seconds.  That was too high.  The target for this restrictor plate is 6500 to 6600.  If Lian gets any more speed (which I'm sure she will), we'll really be on the tailing side of the horsepower curve.  

Here she is on the outside pole getting ready to start Heat 2.

In the first turn of Heat 2, the yellow kart went below Lian and slid up into her.  This knocked her off line and scuffed her new graphics (ouch).  Lian was a little steamed about that (she did not speak to that racer for a while).

I, fortunately brought along some rear axle sprockets.  I quickly swapped out the sprocket and during the feature, Lian turned a maximum of 6531 on her quickest lap of 22.96.  That should give her room to gain speed.

In the feature race Lian started and finished in the back but still turned some good times and got used to the engine tune.

We still have work to do.  My list includes fine tuning the engine (plug, carb, valve lash) so we can squeeze everything out of it.  We also have to do a few things to make Lian more comfortable.  Who knew her driving suit would start to get short or her helmet would get tight?  Ok so those items are on-order...

Looking forward to more competitors next time.  Thanks for reading.

Winter preparations

Took a nice break from working on the kart after Christmas.  Now, we are back at it and starting a fresh blog for Lian's sophomore season.

Bodywork was going to be changed to the new stuff that Lian got for Christmas.  It took longer to mount than I thought but here it is.

After a little hand-wringing, she chose some nice graphics to complement the blue color.  After a short struggle to put flat vinyl on a irregular surface, we got it looking pretty good.

On the priority list for preparations we had to add weight to the kart.  This year though, I wanted to do it right so I sought to get someone to "scale" the kart with real competition grade scales.  My old standby, Doug, was pretty busy this winter/spring with 4 or 5 karts that he was trying to assemble and prep for customers.

I contacted a few racing families from the club and one name came up a couple times, Gary Lawson.  He is a veteran of the club and now races in national series on the pro level.  Gary was available when we had time and I had just received a batch of lead weights to add.  He did an amazing job starting with front end alignment with laser toe gauge and digital camber gauge.

Gary found several problems with the kart.  First, the caster settings were too excessive.  Second, the weight bias was too far forward.  After adjusting the front spindles, he got to work moving her seat back two inches.  After all that, he even adjusted the pedals to make Lian more comfortable to reach.

After getting it back home, we added the cool numbers and name decals that Lian picked out.  Here is the look she wanted.  What do you think?

Trophy

We couldn't make the club awards dinner earlier this month.  I was out of town in training with my company so we missed out.  The club officers held on to Lian's awards and passed them to a trustee who lived in our area.  Diana and Lian stopped by their house a few days ago and got them.  Here is a picture taken after she got home:

Clearly she was pleased!  Lian finished 9th out of 15 racers in her class as a rookie who missed a few races due to my schedule.  Nice size trophy for 9th.  The other award may be hard to read but it is for "Most Improved Jr. Sportsman".  Another nice accolade for here grit and determination on the track.  We are all proud of her accomplishments!

So far, I have done little to prep her kart for next race season other than make shopping lists.  I'm going to have to get busy though as we expect to be practicing in April and that is just around the corner.  Anyone have any scrap lead weights?

Fall Fun Race

No worries, just fun.  The club didn't hesitate to waive many of their rules because this was not for points.  For the kids that planned to move up a class, they were allowed to - even if their kart was not up to weight. We were about 35 lbs light ourselves but they told us not to worry about it.

I probably should have thought of this before but on the way to the track, I began to wonder if I needed to change the rear sprocket to optimize the new engine set-up.  I asked the father of one of the consistently fast drivers when we arrived at the track.  He not only told me what we should run, he offered a gear for me to borrow.  When we re-checked his ratio table, we both realized that with a 16 tooth front sprocket, neither of us had a large enough rear.  He immediately offered a 14 tooth clutch sprocket which would get us in the ball park with the collection of rear sprockets I had on-hand.  Great folks in this sport!

Gear ratios and weights didn't matter much because we were also without the correct rear tires for the class and Lian struggled for traction.  Watching her on the track was impressive.  I've gotten accustomed to watching her with the smaller plate, she is so much quicker!  The Mychron gauge also revealed that the engine is spinning much faster - max RPM today 6,900 versus typically around 5,200 RPM in the other class.

After the first practice, we adjusted the air pressures slightly and went to the driver's meeting.  Even though they spoke about doing something different like running the track backwards, the club officers decided to begin with a conventional race format.  That was to be followed by the "Halloween intermission" then the fun races.  The fun races were planned to be in a relay format where a competitor in one class would pair with a competitor in a second class.  The first group would be arranged on the front straight with drivers standing nearby.  At the green, they would run and jump in their kart, thier parent would start them and send them on their way (this is known as the Le Mans start even though that race doesn't start that way anymore).  After 4 laps, they would head off the course and when they passed a cone on the pit lane, their partner would be cleared to leave the start grid and enter the track.

Out of six racers, Lian started 4th and finished 4th in Heat one.  She complained that the kart was making her nervous by tipping up on two wheels in a fast left-hander.  I countered by increasing the track-width of her rear wheels (surprisingly easy to do).  Her kart was more stable after that change but still slid quite a bit.  In the second heat, she started 3rd and finished 5th but felt safer.  She added that the forces are tougher to deal with than before.  In the Feature, she started 5th and finished 6th.  Not what she hoped for but recognized that dad wasn't going to buy new tires for one race.  We'll do that in the spring.

The race day dragged on a little long.  It was made longer when the race director split the group in two to make it easier to officiate.  Unfortunately, during the second feature race, the leader had her steering wheel come off at the end of the long straight.  She sailed-off into the tire barrier and the race was red flagged.  She escaped with a minor injury to her hand after a thorough check-over by the paramedics.  Her kart was in drivable condition as well with some cracks and breaks in the nose.  By the time all this was cleared-up, the sun was setting.

We decided to forgo the fun races.  It was starting to look like we were not alone as other families were beginning to pack-up.  I quickly removed the borrowed clutch and profusely thanked the other crew for letting us borrow it.  We then loaded-up and headed home with a long list of things to buy or change on the kart.

At the top of Lian's list is new bodywork and wider tires.  For me it's the right clutch sprocket and the additional weight.  We are also considering a different seat as Lian complained it was hard to breathe when she was in the corners.  She may benefit from some additional support if we can find one that fits better.

Here is a early twilight picture taken before the last sunset on this race season:

I'll keep this blog going over the winter as we prep the kart for next year.  Thanks for reading!