edmandsd Posted June 16, 2007 Share Posted June 16, 2007 I appreciate that to most on this forum drag racing is pretty boring at face value. However there are some interesting stats surrounding it. Ever wondered what an average of 1G would equate to in quarter mile times i.e. If you dropped a stone (in a vacuum) from 1320ft how long it would take to hit the ground. The answer is a fraction over 9 seconds. 0.5G equates to just under 13 seconds 0.75G equates to 10.5 secs A modern top fuel dragster pulls an average of 4G in the 4.5 seconds it takes to travel 1320ft. It wasn't that long ago that top fuel dragsters were running 5 second quarter mile times which equates to 3.25G so although the 0.5 second improvement over the last few years may seem relatively small it equates to an increase in average G force equivalent to what's required to run a 10.5 second quarter mile ! The formula used is t(secs)=SQRT(1320/16G) Interestingly a 9.0 second quarter mile time supports average acceleration of 1g where the terminal speed is usually c 160mph. However if you drop a stone from 1320ft (in a vacuum) it will hit the ground at just under 200 mph. The reason for this is that acceleration is of course not constant and a 9 second car may launch with say 2g acceleration and then tail off to 0.5g at 1320ft. Similarly 4g constant acceleration of an object over 1320ft would result in just under 400mph terminal speed whereas a top fuel dragster's speed is c 340mph at the end of a 4.5 second run indicating that well in excess of 4g acceleration is recorded initially and probably 1.5g at the end of a run. This is of course entirely logical and my own timing slips support it as follows: 60ft - 1.60 secs = 1.5G 330ft - 4.3 secs = 1.1G 660ft - 6.5 secs = 1G 1000ft - 8.4 secs = 0.9G 1320ft - 10.1 secs = 0.8G The formula i've used to calculate final velocity from a constant rate of acceleration is V= [sQRT(64G x 1320)] x (45/66) I think i'm right in saying that the improvements in top fuel dragster performance from 5 seconds @ 300mph to 4.5 seconds @ 340mph over recent years indicate that the improvement has come primarily from additional power output and not necessarily improved initial acceleration as the 40 mph increase in terminal speed is consistent with that seen from the differential in constant acceleration at 3.25g and 4g which supports 357mph and 396mph terminal speeds respectively. This appears to be borne out by the suggested increase in power output from 5,500-6,000 bhp to 7,500-8,000bhp during the period, which is in itself quite extraordinary considering the strict limitations applied to these engines throughout the period. Home of BDR700 Edited by - edmandsd on 17 Jun 2007 03:35:52 Link to comment Share on other sites More sharing options...
john aston Posted June 17, 2007 Share Posted June 17, 2007 Some may find drag racing boring- that's because they have never seen it.Or , especially ,heard it.I've been an irregular 'Pod attender since the Dennis Priddle days- and found the above info fascinating. Link to comment Share on other sites More sharing options...
Simon.Rogers1 Posted June 18, 2007 Share Posted June 18, 2007 Thanks for the above Dave very interesting. Silly Hat on now. Is it possible to create a vacuum big enough to do a sprint in. 😬 Perhaps someone will invent a method of creating a mini vacuum around the car so it can always accelerate whilst in a vacuum. Giving it some Welly. As Always! Link to comment Share on other sites More sharing options...
neil.cavanagh Posted June 18, 2007 Share Posted June 18, 2007 SImon, don't forget the oxygen tank then... both for the driver and the engine!! 😬 😬 Link to comment Share on other sites More sharing options...
ruff seven Posted June 18, 2007 Share Posted June 18, 2007 Dennis Priddle is a top bloke, last time I saw him he was supercharging Police Range Rovers in Somerset. Link to comment Share on other sites More sharing options...
Dannyboy Posted June 18, 2007 Share Posted June 18, 2007 Err.......and the pressure suit neil! Could get messy without external air pressure in that vacuum 😬 😬 Dannyboy Link to comment Share on other sites More sharing options...
S47zz Posted June 18, 2007 Share Posted June 18, 2007 So how much power in an average Cat is required to acheive a 12.5 sec standing 1. /4mile? Link to comment Share on other sites More sharing options...
Grubbster Posted June 18, 2007 Share Posted June 18, 2007 Looking at last years 'Fastest Caterham' results it would appear that 130 bhp is enough - but you need to be good off the line to achieve it. 160bhp seems to make it a lot easier. Full results in excel format are here - many thanks to knowley for hosting this link Link to comment Share on other sites More sharing options...
davef Posted June 18, 2007 Share Posted June 18, 2007 appear that 130 bhp is enough Based on last years results you need a bit more than that - when I properly hooked it all together I saw 12.74sec qtr mile - that was with a shade under 200BHp. Dave Link to comment Share on other sites More sharing options...
john aston Posted June 18, 2007 Share Posted June 18, 2007 No way will 130bhp get a 1/4 under 13 surely?Unless you have an unbelievably light shortgeared car.Having had quite afew goes with 160bhp I struggle to get below 14.2.But Maybe I'm crap at it? Link to comment Share on other sites More sharing options...
Grubbster Posted June 18, 2007 Share Posted June 18, 2007 😳My mistake, sorry I was reading the wrong column in the spreadsheet 😳 😳 😳 😬 You need 200 bhp to do a 12.5 Edited by - Grubbster on 18 Jun 2007 20:59:17 Link to comment Share on other sites More sharing options...
edmandsd Posted June 18, 2007 Author Share Posted June 18, 2007 A Mk1 Escort weighing 800kgs w/out driver and using a full race 2.2lt Pinto showing 210bhp on HT Racing's dyno recorded 11.6 secs @ 113mph recently. My old Sylva Phoenix with full house xflow did 12.4 secs @ 109mph and would have shown about 175bhp on HT's dyno. I reckon that engine in my Caterham with alloy block and Elite sequential would dip under 12 secs. A genuine 200bhp in a Caterham should therefore really run under 12 seconds @ 115mph. Home of BDR700 Edited by - edmandsd on 18 Jun 2007 21:37:49 Link to comment Share on other sites More sharing options...
edmandsd Posted June 18, 2007 Author Share Posted June 18, 2007 Although it shouldn't be strictly linear this is what i'd expect a 500kg (w/o driver) Caterham to achieve on slicks. Power 150 175 200 225 250 275 300 Time 13.5 13.0 12.5 12.0 11.5 11.0 10.5 Speed 100 105 110 115 120 125 130 Home of BDR700 Link to comment Share on other sites More sharing options...
davef Posted June 18, 2007 Share Posted June 18, 2007 Dave, I can't quite reconcile your claim that "A genuine 200bhp in a Caterham should therefore really run under 12 seconds @ 115mph" and your table that suggests a 200 bhp seven (weighing 500Kg w/o driver) will do 12.5 on slicks. Anyway I'll note that: - my time was run w/o slicks (Yoko A021Rs in fact) - I'm not the lightest of drivers Dave Link to comment Share on other sites More sharing options...
dannylt Posted June 18, 2007 Share Posted June 18, 2007 Ouch, so at 11.2s I was 0.7s off what I could have done? Though I guess an extra 30kg, marginal clutch and H pattern box don't help. I'll keep my cage though thank you 😬 Link to comment Share on other sites More sharing options...
edmandsd Posted June 18, 2007 Author Share Posted June 18, 2007 Like i said it's a linear table and so not perfect although 225/12.0/115 supports a standard R500 albeit on road tyres. Similarly Dave Townley's 280bhp 2.3 n/a YB supports 275/11.0/125 on slicks although it is much heavier than 500kgs. My own 275/10.0/135 also isn't supported by the table as it's only 430kgs. The 200/12.0/115 previously quoted is assumed to be 'optimum' with less than 500kgs and slicks. Home of BDR700 Edited by - edmandsd on 18 Jun 2007 23:15:03 Link to comment Share on other sites More sharing options...
Colin Mill Posted June 18, 2007 Share Posted June 18, 2007 most on this forum drag racing is pretty boring at face value Went to a drag track in the USA one time and, yes, if it was not for all the silicone enhanced ladies walking around the place I would have nodded off completely 😬 Link to comment Share on other sites More sharing options...
S47zz Posted June 19, 2007 Share Posted June 19, 2007 I'm hoping to achieve. a 13 second time with 158BHP in my S4 which weighs 620Kg in road trim, with halftank of gas etc, at the strip I'll remove the sparewheel, jack, tools etc so ought to make 600kg maybe slightly less coz my toolkit is 12kg Last time I did 1/4 mile was in the other kitcar which weighed 660 and had reputedly 165BHP from 2.1pinto - my best time at avonpark was 13.98 @102mph Link to comment Share on other sites More sharing options...
edmandsd Posted June 19, 2007 Author Share Posted June 19, 2007 Weight is definately a factor although much more so in the first 60/330ft thereafter it becomes a power thing I ran 10.6 at last year's Fastest Caterham event which was 0.5 secs off my normal pace due to the use of new drag tyres that take a few runs to really start working. I'll be trying some new Hoosiers at this year's event and an airshifter which should be enough to run a 9 ❗ With some additional engine mods i'm also hoping to record 140mph over the finish line 😳 Home of BDR700 Link to comment Share on other sites More sharing options...
Irrelevant Posted June 19, 2007 Share Posted June 19, 2007 Although it shouldn't be strictly linear this is what i'd expect a 500kg (w/o driver) Caterham to achieve on slicks edmandsd: What sort of ET/terminal speed could one expect from a 403bhp/540kg(inc. driver) 6 speed sequential equipped, slick shod Caterham? Link to comment Share on other sites More sharing options...
edmandsd Posted June 19, 2007 Author Share Posted June 19, 2007 9.5 @ 150 Home of BDR700 Edited by - edmandsd on 19 Jun 2007 14:46:45 Link to comment Share on other sites More sharing options...
S47zz Posted June 19, 2007 Share Posted June 19, 2007 EdmundsD I agree - though my time does not follow a similar trend to the Cats from last year, my top end seems high compared to last years Cats doing similar elapsed times, which suggests to me that aerodynamics also affects the terminal speed - my other kitcar was far more aerodynamic than even an aero'd Cat. Link to comment Share on other sites More sharing options...
edmandsd Posted June 19, 2007 Author Share Posted June 19, 2007 Aero doesn't really come into much as speeds up to 100mph. If you're getting slow times compared to the speed then it strongly suggests that you getting poorer initial traction as the terminal speed doesn't change much regardless of how good the start is. With slicks you should be doing 13 seconds dead with 100mph terminal speed. This is what my old Mk1 Fiesta XR2 did with an all singing and dancing x'flow. Home of BDR700 Edited by - edmandsd on 19 Jun 2007 15:03:54 Link to comment Share on other sites More sharing options...
S47zz Posted June 19, 2007 Share Posted June 19, 2007 Slicks I've never tried - my car is a 'blatter' - a road car - I'll have ao21's, the best road tyres I know of in 70 section, unless you know of any alternatives? Link to comment Share on other sites More sharing options...
edmandsd Posted June 19, 2007 Author Share Posted June 19, 2007 Let the pressures right down to between 12 and 15 psi - that and a good few chirps to get some heat into them should help a fair bit. Home of BDR700 Link to comment Share on other sites More sharing options...
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