Caterham Seven 485 CSR

[David aka Blue7]

Can anyone clarify the designation of the Caterham Seven 485 CSR.  I thought the numbers indicated the bhp per tonne eg:

Seven 270 / 500kg / 135 bhp / 270 bhp per tonne … hence designation “Seven 270”

Seven 420 / 500kg / 210 bhp / 420 bhp per tonne … hence designation “Seven 420”

Seven 485 CSR / 580kg / 237 bhp / 409 bhp per tonne … but designated “Seven 485”?  Where does the 485 come from, why not 409?  Is it a dastardly Brexit trick to confuse the Europeans

David

[Roadsport06]

I understand the numbers are now based on a nominal figure of 500kg

[Golf Juliet Tango]

Nominal weight for all three different chassis.   

I suppose it is just a number.

[7 wonders of the world]

problem is non of them weigh anywhere near 500kg...... and the weights CC quote are dry weights with no coolant oils or fuel, in the lighteat spec for the car too, with aero etc.

They should use the kerbweight calc that tintops do.

 

[7 wonders of the world]

CC quaote the 420 as 560Kg......

....and the 620 at 545Kg

.....bearing in mind the 620 has a significant amount of additional plumbing, coolers lines blower brackets and lubes which adds circa 25-30 Kg the additional weight saving measures CC quote must include the use of a Helium filled chassis.......  

[Mcalvert]

I'm slightly doing this from memory from when I test drove the original 485 for Lowflying (it's in the archive here) but I seem to recall that the reality is a little more complicated. 

As stated above, the model numbers are based on the the power in PS over a nominal weight of 500kg (for all models).  The original 485 made 240PS which would of course have made it a 480R, however the 5 was added to reflect that it had successfully passed EU5 compliance...

 

[StevehS3]

From now on I am going to consider my 120hp K to be a 243. Much better.

[rj]

Yeeeks. If I have to use 500kgs my figure will go down by 12%

That would be a disaster as it surely would make the car slower.

Or... are the BHP & BHP/whatever figures just for bragging?

[David aka Blue7]

Thanks everyone for the replies, especially Mike's which gets close to explaining it. 

First of all 7 Wonders is correct ... confusingly, when I looked at the CC website last night it was showing a weight of 500kg for the 420 but this morning I just can't find that page but I can locate another page that indicates a weight of 560kg.  Your other information regarding the weights being dry as opposed to kerb is also very interesting.

Nevertheless I seem to be getting closer to an answer in that all the designations are based on the bhp of the engine, which I assume is a bench test or maybe in S3 chassis on a rolling road.  Regardless this figure is assessed against a nominal weight of 500kg which is applied to all models in the range.

On that basis 237 bhp against the nominal 500 kg weight results in 474 and maybe there is now a EU compliance reg. EU11 so add 11 to result in 485?  However, I hate mysteries so further research reveals a further complication in that sometimes CC quote bhp and other time ps, which is pferdestärke (German), sometimes referred to as metric bhp, which is about 98.6% of a single bhp ... now we're getting closer.

So another calculation could be that CC quote for CSR 485 is 237ps, which would be 240 bhp, which using the nominal but incorrect 500 kg dry weight (that doesn't relate to a CSR because it is SV only), would be 480 bhp per tonne plus EUC5 and voilla ... 485 voilà !! 

Talk about confusing

The reason I posed the question is that I attend and enter a lot of static car displays during the year and display a CV for my CSR, which previously indicated that production ceased in 2016.  I have now modified the CV to make reference to the (none Cosworth) European variant CSR 485.  There are always al lot of questions about CC and the variants and what the numbers represent, which I could explain ... apart from the CSR 485 ... but now it is all quite clear ... as Mud!   Thanks again, it has been a very useful exercise for a 70 yo brain

David

PS ... I am going to fit a couple of additional heavy duty battery cables to the bulkhead so that I can claim to comply with EUC 100 "the approval of vehicles with regard to specific requirements for the electric power train" ... and rebadge my CSR 260 as a CSR 360

[Ivaan]

The BECs out there with an electric reverse should claim to be Hybrid. Reduction in VED anyone?

[Richard_420R]

What is different about the 485 Duratec that gets it to 237bhp?  Assume must have higher rev limit, the roller barrel throttles and different ECU?  Be nice to get all those on my 420 :)

[paul jacobs]

I'm working on it - got the badge on the back that says "HYBRID" all I have to do now is to convince the DVLA.  What could possibly go wrong?

 

[simon_h]

A 485 engine, compared to a 420 engine, has high compression pistons, more aggressive cams, ported head, roller barrel throttles and 8500 rev limit to get to the power plus the usual bits to help it stay together. 

[Richard_420R]

Caterham don't seem to offer upgrades to get a 420 to 485 or old R500D spec.  Is it an emissions thing or something?  Or maybe just too expensive to be viable ... I would have thought there'd be a market to get to the ultimate NA setup - wasn't really attracted to the 620 with the supercharger.  

[7 wonders of the world]

If your going spend that money then you can choice a better cam to, A well respected master of the dyno had several R500D visit and not a single one made the claimed 263BHP

Must admit I went the same way for a pokey NA 2.0 Duratec - simply a fantastic motor and arguable the best engine for a 7     

[CharlesElliott]

My '310' race car weighs about 530Kg with fluids, but no carpet, no lights and only one seat. The imperial chassis were definitely lighter than the new metric ones by maybe 15Kg but you would struggle a lot to get to 500Kg.

[David aka Blue7]

I assume that the 500kg is just a base standardised figure to use across the range to generate appropriate model identification names / numbers.  It is an easy way to identify the more "powerful" models in the range whilst not being a true bhp / tonne.

[7 wonders of the world]

Not seen a figure for the difference in chassis weights but 15kg seems on the high side.

However the Mazda gearbox is 15kg heavier than the Type 9, and the BMW iron final drive is heavier than the Sierra version, and then theres the ironmongery to attach it to the chassis too.

The classification is pure marketing smoke and mirrors as the figure are not reflective of real weights - and we wont mention the R500 SV.......  

[Nigel B]

They certainly have become heavier over the years. I traded in my 8 valve Vauxhall engined live axle car for a 420R last year. 

I’ve always pushed the car out of the garage, before closing the garage door & heading out for a blat. I was a bit taken aback by how much more effort was required to roll the 420R out onto the drive!

[David aka Blue7]

Nigel, it's aka ... old age

[Nigel B]

I must confess, that had occurred to me too!