Project S2000 – More Winter Testing and a Challenge
By Khiem Dinh
Khiem Dinh is an engineer for Honeywell Turbo Technologies at the time of this writing. All statements and opinions expressed by Khiem Dinh are solely those of Khiem Dinh and not reflective of Honeywell Turbo Technologies.
It started off like any other chat conversation (note: actual words may have been modified from the original text in order to fit the screen and time allotment)
Khiem: Yo Martin, what's happenin man?
Martin: Workin. What's up with you?
Khiem: I need to take the S2k out for a track day in cold weather.
Martin: Oh yeah? I need to take the SE-R out. Speed Trial USA has a day coming up at Streets.
Khiem: Perfect! How much power does that SE-R make…
And so the bench racing began. Let me back up a bit first as to the reason I needed a track day. Last winter, I did a day at Streets of Willow running the counter clockwise configuration. Since then, I have revised the suspension and added the oiler cooler, so I wanted to see how the car handled and how well the oil cooler performed in similar conditions and on the same track. Martin has a B13 Classic SE-R that needed the cobwebs shaken off. Let's see how they match up shall we?
In corner #1, we have Project S2000. Weighing in at 2950 pounds with the driver and packing about 200whp at the rear tires. Project S2000 rolls on 245 wide Bridgestone Potenza RE-11s tires with 20,000 miles of usage and a lot of track time. In corner #2 sits Martin's B13 SE-R. This is no ordinary SE-R though as a SR20VE resides in the engine bay generating about 200whp to the front tires and weighing in around 2825 pounds with driver. The SE-R can comfortably fit 205 width tires.
|S2k vs. SE-R. The battleground was Streets of Willow at a track day put on by Speed Trial USA. Thanks to Maddog Mike for putting on a fun and laid back track day! Also, a quick shout out to a few MotoIQ readers we met at the track.|
The power to weight ratio is decidedly in the favor of the SE-R with each horsepower only needing to lug around 14.125 pounds. The S2000 has an extra 0.625 pounds to carry per horsepower putting the S2000 at roughly a 4.5% disadvantage. The advantage in grip however goes to the S2000 with a weight to tire width ratio of 3.01 (2950 pounds divided by 4 x 245 width tires). The SE-R has to support 3.45 pounds per mm of tread width in comparison. That actually gets worse if you look at the situation more accurately and examine each end of the vehicle individually as the SE-R has an approximate 60/40 weight distribution. 60% x 2825 = 1695 pounds on the front pair of tires. So that means the front tires need to carry around about 4.13 pounds per mm putting the SE-R at a whopping 37% disadvantage in front end cornering grip.
*Is there already an established performance parameter for tire width to weight in common use? If not, maybe I should claim it; if Coleman can have his Monkey Power Point, I can have Khiem's Grip Ratio (or some other name…. Traction Ratio? Loaded Rubber Ratio?)
In a straight-up street tire battle, it appeared the S2000 easily had enough of a grip and handling advantage to overcome the power deficit on the relatively tight Streets of Willow road course. However, Martin had a card up his sleeve to level out the playing field; Martin brought along an old and well-used set of Toyo RA1 track tires to add grip to his setup. In order to try to balance the understeer experienced by his street driven FWD set up, Martin stuffed 225 wide RA1s in the front while using 205s in the rear. This should allow the car to rotate better, while reducing the weight on the front tires to 3.76 pounds per mm of width. So now the battle consisted of worn-out sticky street tire RE-11s vs. worn-out sticky track tire RA1s. This was shaping up to be a very close battle.
|Not towing to the track requires stuffing lots of gear in your car. “Hey Khiem, bring your jack and jack stands. I'll bring the tools and chairs!” Here's Martin swapping on the wider track rubber and front brake pads using my jack and jack stands that I was able to stuff in the back of the S2K.|
The forecast for the day was a low in the 20Fs and high around mid-50Fs. Considering the reduction of oil temperatures from the oil cooler, I decided to stick with the standard 10w-30 fill instead of the thicker 15w-50 I had used for previous track days. I was feeling especially lazy and decided to forego my ghetto cooling ducts too.
The drive in the morning to the track was COLD. The air temp was only 22F with my oil only reaching 60C (140F) despite the Mocal thermostat being rated for 170F. I am glad I decided to stick with the standard 10w-30! This also proved to be a good decision with my peak oil temperature for the day only hitting 108C (226F) with ambient air temperatures around 55F. 108C is a little warm, but well within reason as the car was designed to operate with an oil temperature of 100C in constant highway driving in warm weather. In going up a mountain grade when the car was stock, I'd gotten the oil temperature up to 106C. So the oil temperatures and pressures were a non-issue with the standard 10w-30 during tracking in the cold weather with the oil cooler. The oil temperature readings are courtesy of the ARK Design MFD-II of course.