solo2racer

All right, you made me do it. I got out the old physics book

Here's the situation:

Coming out of a 30 MPH turn into a 200 ft full acceleration section. This could be a straight, or an increasing radius slalom, or offsets. Somewhere that you are full throttle for 200 ft. We want to know how long it will take each car to get to the end of the straight-away.

Since this is physics, we need to make some assumptions:

• First, we neglect friction since it should be similar between cars.
  
• Second, we assume acceleration is constant in the necessary speed range. This isn't entirely true but I can't remember how to integrate the torque vs speed function
  
• Third, weights include a 200 lb driver.

So first, we have to find mass of each car:
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s2k2fast4me

Brad, your numbers look fine, though you admit you are assuming constant acceleration. In the case of the Boxster's, this isn't necessarily bad since they have such flat torque curves. However, you show the S2K as hitting ~60mph at the end of it's 200' acceleration run (from 30mph), which would take it through the VTEC changeover and it's correspondingly greater acceleration.

Now, let's assume that the S2K accelerates as you say for the first 100', but using 1480 ft-lbs (on VTEC) for the second 100'.

Running through the math the S2K is doing 46.6mph after 100' and 60.75mph after another 100'. What's kind of interesting is the first 100' take 1.772 sec and the second 100' take 1.271 sec for a total of 3.04sec, same as the Boxster 2.7. Get a course where acceleration zones are in the 20mph's to about 50mph, the 2.7 will benefit assuming the S2K driver doesn't use 1st (and vice versa for the 2.7 driver). Get a course like San Diego where the S2K driver isn't dropping out of VTEC much and you can say sayonara to the 2.7. Been there, had that done to me (twice!). I still think the benefit of the S2K's lighter weight will outweigh (pun intended) will largely offset it's torque disadvantage at lower RPM's, and make it a clear winner at higher RPM's.

Of course, all of this is just pencil work. If there were a perfect predictor of autox performance, classing would be a whole lot easier.

ronbauer

Andy,

You keep talking about the S2000 weighing less than the Boxster, but the difference between your weight and mine almost makes up for that!

Ron

y2ks2k

Non-scientific. seat of the pants...

I've been to 2 PCA autoX'ing events in OR. The first one was 2 S2000 and 2 Boxster S's... Both S2000's had faster times. 2nd time, I had higher times by myself.

Now, I was behind the same guy driving one of the Boxster S while a passenger in a Comptec mod'ed 91 NSX (no sc) at PIR. He pulled the entire time and eventually I could not see him by the end (10 laps or so)...