Caterham CSR Trackday toy: April 2012

2012-04-17

Trackday slicks part #4 - how did it go?

During the winter I modified the rear calipers to fit 13" rims, and this weekend was the first test how it worked out.

Well..

First impression was that it didn't. Lots of scrape marks on the inside of the rims and I was really concerned that the rims were ruined.

After a closer inspection, I believe the scrape marks are not from the calipers themselves, but from gravel trapped between the calipers and rims. They are very shallow and I don't think it's anything to be bothered about except maybe for visual appearance. Brake dust, old tire rubber for sure doesn't improve the look of things...

I might give the calipers another go with the grinder just in case.

UPDATE:

After another track day I did have another go with the grinder. After trying several different ways to measure clearance I found the best way was to tape a small drill on the inside of the rim and see where it touches the caliper. Now I'm certain I have at least 2 mm clearance everywhere.

I also took a black pen and painted the edges of the caliper, so if it touches the rim again I can see exactly where I need to grind some more.

2012-04-16

Mantorp graduation

A big day today, I have done so many modifications since last track day before the winter.

In short I have

Fitted 13" rims and modified the rear brake calipers to fit.
Bought an used set of Radical 13" slicks, which are radials and totally different than the Avon cross-ply slicks I have tried before.
Rebuilt the whole engine and added much more power.

"April weather"

In sweden we use the expression "April weather", because the weather can't be trusted at all this time of year. Some days are warm spring days, but suddely the snow come back when you least expected. This is what happened the day before. Lots of snow and below zero degrees temperature. I had to knock away ice from the trailer when loading, and my neighbour had to help me to push the Caterham because I couldn't get it out of the garage.

A few hours later when I got to the track the weather was complely different. +8 degrees, dry and sunny?!

First the good parts. I have so much power I now need to learn how to master. No other car (ok the turbo charged 350-400 hp Atom excluded) had any chance to keep up with me, but most of my driving was like an on/off switch, and my mind played tricks on me so all brake points were too early. I gained about two seconds on the main straight, but lost much of the gain because I braked way too soon! The higher top speed made the grass at end of the straights really intimidating!

Red line this day, black line last year.
Very good acceleration, very poor braking!

The tires worked flawless. The asphalt was cold today but there was no overheating and good balance. My impression is that the tires are more forgiving than cross-plys, and not equally sensitive to camber/pressure and slip angle.

Best time today 1,26.1 but the car has for sure potential for sub 1,24 times!

Then the less good things.
My temporary catch tank was too temporary and spew oil all over the engine room. Yuck!

The rear calipers scraped on the inside of the new 13" rims. I have to do a damage check on this, more about this later.

2012-04-12

Camber calculator

An easy way to measure camber is to use a spirit and a ruler. It is really important that the car is standing on a completely flat surface for this to work. Accurate? Well, accurate enough for me anyway.

Simple camber calculator:

Rim	mm
D1	mm
D2	mm
Camber	degrees

2012-04-11

Rear hub nuts

Both sides loose - scary! Left side so much I could turn it with my fingers.

41 mm socket.
270 Nm (yes that is a lot!)

2012-04-06

Engine upgrade - part #9 - final results

So far the engine have behaved extremely well and almost no problems at all. A bad battery connector, small coolant leak because of a loose jubilee clip, oil filler cap leak, but nothing serious.

Then it was time for a rolling road session at Turbocenter. It was kind of the ultimate test to see if the build was successful or if the engine would dissolve in a puff of smoke. The first time Claus took it to rev limiter my hands were shaking and my heart was up my mouth, but it held together!

As you can see in the video, in the beginning there was some problems with tyre slip against the rollers. I left the car with them for a week while going for a well needed vacation and I'm not sure how he solved the tire slip, but I think he tied down the roll cage to the floor.

The final result is: 231 hp on the rear wheels @7500 rpm. Max torque ~230Nm. It would for sure be interesting to know how much that power would equal on the flywheel, but that is impossible to find out. Google it and you'll find lots of opinions on this subject. The loss is dependant on gearing, tyre wear, tyre air pressure, moon phase etc etc and even compare the same car on the same dyno two different days could generate different results. But I guess crank power around 270-280 hp is within reason.

As seen on the chart I have a problem maintaining constant fuel pressure when power increases. The reason for this could be many, leaking low quality fuel regulator, insufficient fuel pump, clogged fuel filter, too narrow fuel lines. Before buying a new pump Claus recommended me to move the fuel regulator to the end of the fuel rail, and put the fuel return line from there. He had a neat solution for this and I might give that a go further on.

I also have a power plateau around 4500 rpm. I don't know why. Could it be the exhaust system? I leave it as it is for a while and let all this digest until I feel ready to handle it.

Immediately when I got the car I took it on a test drive. It is early April and the roads are cold and my tyres have almost no rubber at all, but on all of the first four gears I got wheel spin when getting into the engine's power band!! This is crazy!

UPDATE: A test run this morning. Here is a 110-190 km/h comparison before and after: