KB58 wrote:
Another thing, everyone cheats. That is, nearly everyone leaves out driver weight (and sometimes fluids), which gives a more impressive number. In such a light car, driver weight can skew the result by 15%. The number is almost entirely for bragging rights.
I'm glad you bring that up.
Caterham in particular is known to be loosy goosy with their numbers to achieve the R400/R500/620R
1) They use a metric ton vs regular ton (2240 pounds)
2) I believe and I could be wrong that the weight is dry and typically without other options. (If you order your R400 and add heater option, obviously weight goes up, P/W goes down but it remains R"400")
3) The engine numbers are crank numbers, while most of the people who build and modify their cars use wheel HP numbers
4) Even if the numbers don't add up exactly, R400 sounds a lot better than R393...
I personally have a what was sold to me and believed by the previous owners to be an R500. Zetec HP with ITB's and other mods is estimated to be ~200, which would make it roughly an R400 technically.
At the end of the day do I really care which moniker the car should have? Not at all. It's a blast to drive and I almost never go WOT.
The much bigger issues with the car other than the P/W are the other elements that come with a car like this. Strapping yourself into the harness every time you go a block, looking out for rain, debating on putting top/doors on, looking out for pot holes, etc etc.
My advice? Pick front vs back, pick a motor, pick a reasonable HP that you can easily achieve with that motor and go at it.
Edit: For fun math
R420 = 420hp/ton
~210hp Duratec crank (likely optimistic to begin with)/1240 lbs = R378 (using crank #)
We area already at way lower number than the plaque and that is stock, using their own numbers provided on the website.
Start adding other common features that don't come with that 1240 lbs standard spec. + dry sump + LSD + weather equipment + heater + windshield washer + carpet + SAE Roll bar (thicker) etc etc.
Lets even say this will add 100 lbs, we are already an "R350".
Point is, my "superlight" (In quotes as I have carpet, wet sump, windshield washer, tools in the back, weather gear + gas/fluids) as it sits now could likely be the equivalent 300hp/ton or less an I won't care cause its still a blast and its still fast.
Edit X2: I dug deeper and this is what I found (see attachment)
They actually openly list that they are realistically 375ps per tonne for the R420. 620S is "Power-to-weight: 508bhp-per-tonne"
270 is one of the most "honest ones" Power-to-weight: 254 bhp-per-tonne
Source:
http://us.caterhamcars.com/cars/seven-270