sorry if im talking shite again?
Ive heard alot of people say that regardless of how much power you run in a 7 it will slow down after 100mph? due to aerodynamics, someone commented
in another thread that a 7 would not keep with an evo after 100mph, has this been proven or is it pie in the sky?
sorry if im talking shite again?
Theoretically speaking the theory is right. However my old flight instructor used to say that given enough power even a brick will fly.
yea the thread about the evo was one i started lol
i have done some calculations about BHP Vs Top speed....
Will post pic of graph in few mins....
Max speed isn't the point of a seven, IMHO. They're all about rapid acceleration and snappy cornering. I probably drive faster in my
tin-top! However, I have more fun in the twisty bits with the seven.
I don't know about aerodynamics, but the airflow around the driver gets a bit fierce after 90mph!
Mine will pull too around 125 on its own, hit 132 two up with a bit of slipstreaming under the dunlop bridge at Donnington.
The thing is you have braked later, gone round the corner quicker and accelerated away quicker than most "supercars" this is of course on
twisty roads or circuits, in a straight drag race on a straight road sooner or later the "supercar" will pull away but not until you have
reached lost your license speeds.
Here is the graph i was talking about,
it assumes that you have built by book dimensions, that you have a windscreen and the car weighs about 600kg
http://www.locostbuilders.co.uk/photos.php?action=showphoto&photo=untitled%20graph.JPG
cheers
Matt
hold on that link isnt working.....
The power required to overcome aerodynamics is proportional to the cube of speed. If you double your speed, you need 8x the power to overcome
aerodynamic drag. you only need to double the power to overcome rolling resistance.
A seven has roughly 40% more drag than an ordinary car and about half the rolling resistance. At low speeds, the seven goes like stink but it will
slow down more with increasing speed than your ordinary car.
The 100 MPH figure quoted is just nonesense. It is purely down to the power of your enigne. It takes about 78 BHP for a seven to do 100 MPH versus
about 61 for an ordinary car. With 150 BHP, your seven will top out at 123 MPH and your ordinary car 137. At 100 MPH your seven's acceleration
is decreasing more rapidly than your similarly powerful ordinary car. but it will still feel fast. A 95 BHP pinto will feel slow below 100 MPH but a
180 BHP seven will still be pulling strong at 120 MPH
try this link instead ....
http://www.custom-concepts.co.uk/untitledgraph.JPG
it might be absolute rubbish but i hope it give somewhat of a guideline
and i have to agree with Dave Jenkins on this one, a 7 is all about the acceleration.
matt
[Edited on 30/12/06 by novacaine]
In my r1 160hp after dynojet
I raced an EVO (03 plate? they are fantastic cars for people who cant drive and need the car to drive for them) from the cannock toll road standing
start I DESTROYED it clutchless upshifts all the way to 122mph on the limiter I think I pulled away so quick that he couldnt keep up and gave up
however i think if he had of tried after about 90mph there wouldnt have been much in it
DILLEY YOU HAVE A TURBO BEC have you been drinking to much over this festive period
you should be moving onto Bugatti bating not asking about evos
PS everyone Im talking about normalish EVOS not MAX POWER 650bhp ones that never get took out
chris
Acceleration is heavily dependant upon power:weight. Top speed is more dependant upon power and drag coefficient.
Sevens have a poor drag coefficient (to put it mildly) and although they have a good power:weight ratio they usually don't have humungous amount
of power.
If you get something that is effectively a covered Seven (like a Phoenix / Fury) it will weigh more (therefore accelerate slower) but the top speed
will be better for a given power engine due to the reduced drag...
The difficult bit is that when you start using huge amounts of power, you usually need loads of downforce to allow you to use it. Creating downforce
creates drag, so higher power can equal increase drag (hence a Lambo Countach has the same drag coefficient as a VW minivan).
Clear as mud huh!
[Edited on 30/12/06 by BenB]
from experience i added a dyno proven 90hp to a car i had and it gained only 10mph top speed
'Theoretically speaking'
Given the same power, there would be few(if any) 'tin tops' that would keep up with a Se7en type car in any circumstance.
Even though the drag of a 7 windscreen is high, the frontal area overall would be much less.
Cheers,
Syd.
Have to remember that most sevens are well under 200hp. The only reason 200hp is fun is because its in a light car. A 200hp camaro isn't nearly
as fun.
This is fine for acceleration at low speeds when its power/weight, but when it become power/drag 200hp is not really exciting. At that point the
high drag of the seven** sucks up all the power to push through the air. My first vehicle was a 70 C10 with a mild V8. In top gear at 120mph the
truck stopped at 4500rpm. Engine just flat out did not have the power to push through the air any faster, or to raise the engine rpm. Add enough
power and even that brick will go faster. Proven by a 72 C10 which was the worlds fastest drag truck. 1st truck to do over 200mph in the 1/4 mile.
http://www.dragracecanada.com/canadian/cool/photos/017.jpg
Anyhow, best to stick to lower speed events in a low horsepower seven .
Cheers.
** I have not actually seen any evidence of the sevens poor drag co-efficient. Just going by hearsay. Does anyone have some further info to
edumacate me?
I can keep with a gsxr 1000 all the way to 151mph and I hit the rev limiter, running 220 bhp at the wheels. so how does that equate to what people
say?? it doesnt mak sense to me
Just like to add all testing done on track, and I do not condone speeding unless ive been down the pub(joke)
[Edited on 30/12/06 by dilley]
you have got 220bhp at the back wheels
can keep up with a gsxr1000 up to 150
and your asking about drag?
I think the point is some havent got even 100bhp 7's
and after 100mph they may not have the affect yours does
It's all about the power required to force a brick/7 through the air at speed. 7's aren't geared for really high speeds (160-180 I mean
here). Just adding power will make you faster, but if the gears allow 20 mph then that's it. This is fiddily to explain with just words. Most
7's will top out at 120 ish due to either gears or power. Assuming the gears aren't a problem, then more power = more top end, but sooner or
later, you'll run out of gears. An example is my mini. 150 odd bhp, but only does 110 due to hitting the red line in 4th. Given a 5th/longer 4th
it would do much higher. Dilley can go so fast due to having a silly/brilliant engine!
I'll apologies now if all that sounds stupid, but as I said, I'm finding it hard to type what I mean.
Have a look at Wikipedia here for some examples of drag coefficient (Cd) and more importantly
CdA which multiplies Cd by drag area. The Caterham Seven is listed as a Cd of 0.7 which is indeed pretty bad. Unfortunately they don't give a
measure of the frontal drag area for the Caterham. The Subaru Impreza has a Cd of 0.33 and a CdA of 7.72 ft^2 so while the Cd is half that of the
Caterham, the frontal drag area is probably also about half, especially if you remove the Caterham windscreen and use an aeroscreen instead as many
do.
I know Seven's were never known for high speeds but this is probably more to do with the fact that they were so quick on a modest amount of power
(say 75BHP) that people were disappointed that they couldn't go on to higher top speeds. (eg. 0-60 in 6.5 seconds but only 110MPH just
didn't seem "normal!"
Here are some figures from the Caterham website:
105bhp, 6.5sec, 110mph
125bhp, 5.9sec, 112mph
140bhp, 5.1sec, 122mph (550Kg)
140bhp, 4.9sec, 125mph (500Kg)
160bhp, 4.9sec, 128mph
200bhp, 3.7sec, 140mph
260bhp, 3.1sec, 155mph
Note, these are all car engines so have comparable characteristics.
Edit: Just found this:
http://www.mayfco.com/caterham.htm
Shows Caterham Super 7 Cd to be 0.62 , area to be 15.82ft^2 and therefore CdA is 9.81ft^2.
Not that far removed from the Subaru mentioned above.
[Edited on 30/12/2006 by craig1410]
This tin top gets up too 200mph
Sounds really nice while it's doing it too...
Im no aerodynamicist but I have done some messing around. Far as I've seen most of the drag comes from the air leaving the body, and the big
empty hole behind the car trying to pull the body into it. The CdA seems less important to me than reducing that drag from the rear. Which is why
the wedge shaped cars of the 80s have lost favour. I would guess the worst of the sevens drag comes from the open cockpit (and windscreen if
equipped) and the big,flat back panel. Add to it the wide open grille that is rarely vented correctly and yes, for a small car I can see the drag
being quite high. On the average seven I would guess the air under hood tries to get out under body, and worse, through the trans tunnel. I'd
would be curious to see if there is a high pressure area in front of the rear panel because of that. That high pressure area, and the known low
pressure area behind the car may be nasty for drag.
As I said, this is all my own ideas. No calculations to back it up, but it makes sense to me. I do intend to have "proper" ducting on my
seven and play with the aero a little bit. My 100hp engine is going to need all the help it can get .
Cheers.
Without doubt the easiest way to achieve these speeds is to fit a bike engine and clocks and not re-calibrate the clocks!
A mate with a blackbird engined Westfield did this (he just hadn't got round to re-caling the clocks), took a friend of his out who came back
ranting and raving about doing 170mph down small back roads.
120 in a BEC feels nuts anyhow!
quote:
Originally posted by C10CoryM
The CdA seems less important to me than reducing that drag from the rear.
Sorry but i just can't accept that, who was riding the bike, big daddy with giant haystacks as pillion?
Originally posted by dilley
I can keep with a gsxr 1000 all the way to 151mph and I hit the rev limiter, running 220 bhp at the wheels. so how does that equate to what people
say?? it doesnt mak sense to me
Just like to add all testing done on track, and I do not condone speeding unless ive been down the pub(joke)
[Edited on 30/12/06 by dilley]
speak to jack at holeshot racing, or pop down on a nice dry sunny day and ill take you out, that quote was with 2 in the car, looks like I need to
take sombody out on this site to varify a few things you about Sean??
Sean, please don't be offended, i don't doubt that the car is awesomely quick, but to match a gsxr 1000 all the way to 155 in a 7 ????.
Tell you what bring it to York next year and do the 0-60 challenge, if you hand me a timing slip with a sub 3 sec 0-60 and a 1/4et of 10 secs, i might
just accept i'm wrong.
Al.
Originally posted by dilley
speak to jack at holeshot racing, or pop down on a nice dry sunny day and ill take you out, that quote was with 2 in the car, looks like I need to
take sombody out on this site to varify a few things you about Sean??
Apparently this monstrosity only has a drag coefficient of 0.19!
Aerodynamics make no sense to me anymore... 
quote:
Originally posted by Wadders
Sean, please don't be offended, i don't doubt that the car is awesomely quick, but to match a gsxr 1000 all the way to 155 in a 7 ????. Tell you what bring it to York next year and do the 0-60 challenge, if you hand me a timing slip with a sub 3 sec 0-60 and a 1/4et of 10 secs, i might just accept i'm wrong.
Al.
I see it has 140BHP and yet it can only do 118mph whereas a Caterham with 140BHP can do 125mph with a Cd of 0.62. Then again, the frontal area of the
Bionic must be 3 or 4 times that of the Caterham.
[Edited on 31/12/2006 by craig1410]
quote:
Originally posted by Wadders
Sean, please don't be offended, i don't doubt that the car is awesomely quick, but to match a gsxr 1000 all the way to 155 in a 7 ????. Tell you what bring it to York next year and do the 0-60 challenge, if you hand me a timing slip with a sub 3 sec 0-60 and a 1/4et of 10 secs, i might just accept i'm wrong.
Al.
Don't always believe what you read, in my experience real world times never match what the calculators say. Its all about putting the power down,
But hey, truthfully i would love to proved wrong.
Originally posted by akumabito
quote:
Originally posted by Wadders
Sean, please don't be offended, i don't doubt that the car is awesomely quick, but to match a gsxr 1000 all the way to 155 in a 7 ????. Tell you what bring it to York next year and do the 0-60 challenge, if you hand me a timing slip with a sub 3 sec 0-60 and a 1/4et of 10 secs, i might just accept i'm wrong.
Al.
no offence taken
Trust me, i wouldn't say it, if i didn't know it was possible
http://www.dontbescaredracing.com/video/zx10r_nj.wmv
Originally posted by craig1410
ps. Wouldn't you need to prep the bike's rear tyre in order to do a 10sec 1/4 mile? Surely a bike with a cold rear tyre would lose more time
on a 1/4 mile run than a car with cold tyres? I'm not a biker but I would expect it would take a lot of effort to maximise a bike's 1/4 mile
performance - more so than a car.
[Edited on 31/12/2006 by craig1410]
Cool, you up for making me eat humble pie then??
Originally posted by dilley
no offence taken
possibly
Shouldn't t that be definately
seriously, it would be nice to see you there, waving a timing slip and two fingers at me
Originally posted by dilley
possibly
I allways said that I would stay away from santapod and the likes, I know it will all end in tears because ill have to have the boost wound open to
about 26psi and ill get carried away.......when is it
anyone got some slicks?? and suspension setup, might need to change the diff aswell!!
Usually around May time, and believe me it's no santa pod, hillbilly racing kind of sums it up good fun tho, and those timing slips are
addictive. You should get at least a dozen runs, so no need to go mad with the boost, well not at first anyway Go on you know you want to In
all fairness you would stand a good chance of taking home the silverware.
I'll remind you nearer the time, no one from here ever turns up, which is a shame as it's a top day out.
ATB
Al.
Originally posted by dilley
I allways said that I would stay away from santapod and the likes, I know it will all end in tears because ill have to have the boost wound open to
about 26psi and ill get carried away.......when is it
I wasn't doubting it was possible, just that it would require rear tyre prep (as shown in your video) as well as a rubbered in track to get the
best times. A car would also benefit from a burnout beforehand but I would expect it not to be quite so crucial to a decent 1/4 mile time.
On the subject of video's, have you seen this one?
http://www.youtube.com/watch?v=HXQTzxepYjg
Enjoy!
quote:
Originally posted by Wadders
Trust me, i wouldn't say it, if i didn't know it was possible
http://www.dontbescaredracing.com/video/zx10r_nj.wmv
Originally posted by craig1410
ps. Wouldn't you need to prep the bike's rear tyre in order to do a 10sec 1/4 mile? Surely a bike with a cold rear tyre would lose more time on a 1/4 mile run than a car with cold tyres? I'm not a biker but I would expect it would take a lot of effort to maximise a bike's 1/4 mile performance - more so than a car.
[Edited on 31/12/2006 by craig1410]
Hi Everybody,
Been reading this thread with much interest, i will stress right now that my knowledge and indeed understanding of aerodynamics is VERY limited
however it is common knowledge and rather obvious that something like a Fury is better than a 7 regarding air flow over and around the body. This is
the whole point of us buying the old Tiger Storm moulds so we can supply a "smoother" body for the Locost chassis.
as soon as we have a demo car completed it would be very interesting to test it alongside a standard 7 shaped Locost with similar engine and power to
compare acceleration and top speed.
FT.
I dont dispute, if you involve lots of corners the bike will always lose, especially to a 7.
But in a straight line dash to 155, my brass would still be on the bike.
On the subject of video's, have you seen this one?
http://www.youtube.com/watch?v=HXQTzxepYjg
Enjoy!
Look forward to that one Chris, maybe arrange it to coincide with the 0-60 challenge? its usually a RWYB and 2NZ day as well, with the additional
bonus of getting a 0-60 time on your slips. Only downside is, being May the weather might not be 100%.
more than likely i'll be arranging another drag day up at york for everyone who's interested at sometime in 2007,
quote:
Originally posted by craig1410
On the subject of video's, have you seen this one?
http://www.youtube.com/watch?v=HXQTzxepYjg
Enjoy!
quote:
Sorry, been a bit slow. I reckon in the best tradition of TG, that that was a fix, coz Clarkson is a know twowheelophobe.
Tiff and crew did a similar thing with a bike and a load of cars from 7's to supercars, and a few in between (like Evo's and clones), and none were as quick as the bike.
I don't doubt that a turbo bec is quick, but can it do 100 in under 6 secs, let alone 60 in under 3?
For next project, I'm going to aim for 80 mpg at 80mph
ATB
Simon
craig1410 - 4/1/07 at 01:31 AMSimon,
I know where you are coming from and you may well be right. However, a bike tyre only puts down a fraction of the rubber that a car tyre puts down and I don't think a bike can generate any sort of downforce so cornering and braking (and start line traction) must be less than that of a car surely.
Where the bike is untoucheable is when you can let loose full power without flipping the bike and without losing grip. I'm guessing that to be from around 60MPH upwards while in a straight line.
A typical track will have a mix of corners and straights and I would guess there are some tracks which would favour bikes and some which would favour cars. Clarkson might just have chosen one to favour bikes to "prove his point."
When all is said and done you can probably only compare the "ultimate bike" to the "ultimate car" and I don't think many would expect any sort of bike to beat an F1 car around any track!!
Cheers,
Craig.
Simon - 4/1/07 at 08:00 PMCraig,
Don't forget the tyre compounds - I never managed more than 800 (yep hundred) miles from a set of tyres on my 'busa.
I go to Brighton Speed Trials every year (including a trip back to Brighton from our honeymoon in Dorset
Anyway off topic, how's your build coming on? You must be nearly done now
ATB
Simon
craig1410 - 4/1/07 at 10:19 PMSimon,
Oh don't mention my build... I've just spent the entire day fixing (hopefully) a leaky bath. Had to remove it and reinstall it basically with a generous dose of silicon all round. I also had to repair damage to my house roof after the storms a few days ago.
I've been off work since 22nd December and have spent precisely zero days on my car. I'm hoping to get peace to work on it this weekend. As usual, not much left to do but the last few jobs seem to take forever don't they!!
Cheers for asking,
Craig.