Windscreen performance penalty
Discussion
I was on Silverstone GP circuit yesterday with my 260CSR, and was very pleasantly surprised by the car's performance over a lap compared to a Porsche 997GT3RS.
My CSR is a standard road car with a full screen and side curtains, my question is, how much quicker would it be if I removed the screen ? Are there any definitive figures ?
My CSR is a standard road car with a full screen and side curtains, my question is, how much quicker would it be if I removed the screen ? Are there any definitive figures ?
Just had a quick look at the Caterham Graduates Racing Club's results archive. The Club's 'Sigmagrad' class competed up to 2011 with windscreens, and for 2012 the regs were changed to permit the removal of the windscreen and the fitting of a small aeroscreen in front of the driver. I don't recall any other relevant regs changes being made for 2012.
We visited Rockingham in 2011 and 2012, and both visits the weather was dry for the races. Also, both visits a lap record was established.
In 2011, with windscreens, the LR was set at 1:37.141
In 2012, without winscreens, the LR was set at 1:35.646
So at a long circuit like Rockingham International Sportscar, the difference could be 1.5 seconds. For the sake of perspective, I should say that the Sigmagrad is a 120bhp, 5-speed, open diff car and they're fitted with Yokohama A048 tyres.
Losing about 3 sq.ft. of practically vertical frontal area will make a difference!
We visited Rockingham in 2011 and 2012, and both visits the weather was dry for the races. Also, both visits a lap record was established.
In 2011, with windscreens, the LR was set at 1:37.141
In 2012, without winscreens, the LR was set at 1:35.646
So at a long circuit like Rockingham International Sportscar, the difference could be 1.5 seconds. For the sake of perspective, I should say that the Sigmagrad is a 120bhp, 5-speed, open diff car and they're fitted with Yokohama A048 tyres.
Losing about 3 sq.ft. of practically vertical frontal area will make a difference!
I have the interchangeable screen on my R400d. Agree with the comments above- switching to aero screen is worth 2-3 seconds a lap for me at the longer power circuits (eg silverstone and spa). I also switched from cr500s to zzr tyres and that generated another couple of seconds. Combined these two mods have been the cheapest and most effective way to increase performance.
subirg said:
I have the interchangeable screen on my R400d. Agree with the comments above- switching to aero screen is worth 2-3 seconds a lap for me at the longer power circuits (eg silverstone and spa). I also switched from cr500s to zzr tyres and that generated another couple of seconds. Combined these two mods have been the cheapest and most effective way to increase performance.
Excuse my ignorance but how is your 'intercangeable' screen different to the std one, I ask this as I use the carbon aero screen on track, std windscreen on road and it seems a pretty quick change already..Unfortunately CSR owners have been left somewhat high and dry on the tyre front, only CR500's are available for the car as it has 15' wheels, and to convert to 13" wheels means a non-road legal car as the rear uprights and brakes have to be changed, leaving no possibility for a hand brake ! Not Caterham's finest hour in looking after clients who bought their premium product ?
PHOENIXUK said:
Excuse my ignorance but how is your 'intercangeable' screen different to the std one, I ask this as I use the carbon aero screen on track, std windscreen on road and it seems a pretty quick change already..
Not much difference. Its all the same kit just with captive nuts inside the car to make the switch over a bit simpler. I do the same as you- air brake on the road and aero screen on track...ravon said:
Was thinking about captive nuts to hold the windscreen in place under the scuttle and hopefully "racing screen" mountings in line with the windscreen line so the racing screen mountings are covered up by the original windscreen when it is in place .
Done that for mine. I seem to recall the captive nut brackets are a fairly standard upgrade, and with Brooklands mounted on a stanchion it means going from screened to screenless takes less than 5 minutes.
Dr Slotter said:
Oh, I see now. You can't get the rear tyres wide enough in 15s. Ignore me!
It is not the rears, it is the fronts. Most tyres in 15" are too large in diameter and may foul the front fenders, but this can be fixed with a bit of creativity. ACB10 works (but are crossply).13" split rims can be fitted with the handbrake still in place if you grind down the cooling-fins on the rear calipers.
I'm using a calliper with a 156.5mm radius inside a 13" Force split rim.
That's with a 279mm dia. disc.
Am I correct in thinking the CSR has a 260mm rear disc and VW callipers?
I believe the Force rims have the larges inside dia. available.
I can't remember what it is now, but MB's also have a large inside dia. That's if you can get them....
That's with a 279mm dia. disc.
Am I correct in thinking the CSR has a 260mm rear disc and VW callipers?
I believe the Force rims have the larges inside dia. available.
I can't remember what it is now, but MB's also have a large inside dia. That's if you can get them....
I don't know about the exact measurements but yes I think the rear calipers are from VAG.
I use Force racing 13" rims and it works ok. I got some scrape marks on the inside from the calipers but not that bothers me too much.
http://csr200.blogspot.se/2011/11/trackday-slicks-...
I use Force racing 13" rims and it works ok. I got some scrape marks on the inside from the calipers but not that bothers me too much.
http://csr200.blogspot.se/2011/11/trackday-slicks-...
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