Hi,
Have any of you done 1/4 miles in your car or have measured acceleration? If so please could you post the times and what engine used, approx weight
and any mods which may have an effect. I think my car is seriously down on power and would like to prove this to myself without using a dyno.
thanks
Carnut
Yep
Locost blade (425kgs)
Quarter Mile was 13.4s @ 105mph
With the R1 engine (same weight) is was 13s dead @ 110mph but would get into the high 12s as I only had a couple of runs that day.
Both of these were on normal Yoko A509 road rubber (not sticky Yoko 32/48s etc), launch technique was approx 6k dialled in then lift clutch as fast as
possible (not sidestep though), then feather the throttle to minimise wheelspin
Chris
Excuse my ignorance but whats "Sidestep"?
Thats made me think im down on power even more. I do it in 13.2@101 normally aspirated. I think im putting out similar power to a blade engine
because of this.
A possible reason for this is that when I broke my engine I got a 2nd hand head and cams. I think this may have come from an x11 rather than
blackbird. This would put me around the same power as the blade as the x11 is a detuned blackbird engine by having a shorter duration and lower lift
inlet cam.
I need to get home to take it apart and compare some cam profiles but im at uni so that wont be for ages.
If it is an x11 cam, ill be well chuffed as i'll just change it and get 30hp.
Carnut
Sidestep is sliding your foot of the clutch sideways so it springs up as fast as it can.
Carnut, you might be down on power but judging from personal experience it could also be technique maybe?
As an example mate of mine with a fairly heavy ZX12 ST Locost managed a 12.5s @ 115mph yet a mate with a lighter Megabusa on stickier tyres couldnt
get within half a second of it. Also a friend with a Megablade only just managed to scrape under 14s on one occasion out of about 6, again with
stickier rubber than I was using and looked to be launching well when I watched his runs.
Chris
[Edited on 10/11/05 by ChrisGamlin]
It could be but ive been to just about all of the drag racing meetings at york this year doing beteen 10 and 20 runs at each meeting. I think ive
honed my technique resonably well. Anyway the only real point where technique matters is the start and gearchanges. If it was the technique the
terminals wouldnt suffer as much as I only get 100 mph where you got 105 with a blade.
thanks
Carnut
Chris,
Can you remember what your 60' times were? and also your 1/8 time and speed if you know.
thanks
Carnt
Fair enough about the technique, sounds like youve had lots more practice than I have! I agree on the terminal speed being a good indicator of power
too, so does sound like you're a bit low.
ISTR I also had times of around 2.2-2.4s on the slips so I assume that would be 60ft times? Sorry not really up on my drag racing as Ive only done it
a couple of times).
Where we were there weren't any 1/8th times I dont think, it was only a one off RWYB on an airfield down near Portsmouth.
Chris
Thanks Chris
Those would be the 60ft times. I run about 2 to 2.1 secs in the first 60ft. As this is faster then your running for that distance and im slower over
the higher speeds, I assume that I am making less power.
BTW I use toyo proxies t1-s tyres which aren't all that grippy although I dont spin the wheels once rolling so I cant put it down to traction.
Carnut
Cheap performance upgrade (2 week waiting time)
13.3s best on old carb blade engined ('92)indy. cant remember term velocity
Still fast enough to whupp the neds! well except the odd nissan
pulsar with megaboost.....
Any chance there's a difference in gearing carnut?
What final diff you using? And Chris?
Within the bounds of useable diffs for BECs, in my experience the ratio really doesnt make much difference to overall acceleration. I think I might
have had the 3.89 in at the time of running the blade, and had the 3.54 in when running the R1 last summer.
Chris
Ive had both 3.9 and 3.62 in it. It makes hardly any difference.
Thanks for that. Very interesting...
Chris
I just need to be patient now before I can take the cam cover off and see if it is an x11 cam.
If not I need to find where the loss of power is coming from. Maybe i'll have to start by getting it on the rollers.
quote:
Originally posted by carnut
Maybe i'll have to start by getting it on the rollers.
quote:
Those would be the 60ft times. I run about 2 to 2.1 secs in the first 60ft. As this is faster then your running for that distance and im slower over the higher speeds, I assume that I am making less power.
quote:
Originally posted by Chris Clarke
This is because when you get a lot of wheelspin off the line (and therefore a higher 60ft time) you end up shifting earlier, and therefore are in a higher gear earlier and have a higher final speed.
I cant see the part of being earlier in an higher gear and being faster...
i think that in the fastest run you will have the fastest exit time.. wy?
because an cars potentinal on the 1/4mile or any distance is just down to the technique... the driver uses and the car will differ ver small (fuel
consumption==> less wight, hotter tyres, more rubber on the strip..better engine temp?)
if you take off with allot of wheel spin you
a) waste space because you move but not eff. ==> TERMINAL SPEED
(maybe you increase tyre temp and grip!)
b) you waste time because you are practically aren't moveing. ==> LESS TIME
you can only getting faster out, if you can use more room/way or have better grip!
(altough on an straight line it might be less important as long as you don't have slip)
Any way you will need X room to make Y speed with the car. if X is bigger and the technique is the same Y will be higher (if not on his limits...)
the rate of X and Y will depend on HP and gearing also the limit of Y (shiftings needings etc.)
Tks
It might be different with other car / gearbox types, but I was only getting wheelspin in first which takes me up to around 50mph. I was always
getting an element of wheelspin and then feathering it to minimise it and always changing up at around 11k by which time the wheelspin had abated,
then nailing it thereafter. I wasnt getting any wheelspin in 2nd, and wasnt using second to reduce the wheelspin so in my instance I dont think it
would make much difference.
[Edited on 10/11/05 by ChrisGamlin]
yahh
quote:
b) you waste time because you are practically aren't moveing. ==> LESS TIME
quote:
Any way you will need X room to make Y speed with the car. if X is bigger and the technique is the same Y will be higher (if not on his limits...) the rate of X and Y will depend on HP and gearing also the limit of Y (shiftings needings etc.)
quote:
It might be different with other car / gearbox types, but I was only getting wheelspin in first which takes me up to around 50mph. I was always getting an element of wheelspin and then feathering it to minimise it and always changing up at around 11k by which time the wheelspin had abated, then nailing it thereafter. I wasnt getting any wheelspin in 2nd, and wasnt using second to reduce the wheelspin so in my instance I dont think it would make much difference.
quote:
I think that 13.0's generally run around 105mph, and 110 mph is closer to 12.5 ET's. So it probably is a power issue for you. 2.0 - 2.1 60' is normal for a RWD car on street tires also.
I think there's a fair amount of variation in the top speed / ET time relationship though. A Locaterfield will often get off the line better
because its very light, but by the time you're hitting 80-90mph its fighting againg very poor aero so may well have a slower top speed than the
ET suggests. Conversely a very heavy and powerful car might struggle to get off the line but once it does, will still hit a high terminal speed. There
were quite a few TVRs and a Lotus Carlton at the event I did last year, they were often 5-10mph faster through the trap than me but were still a good
half second slower ET, so running ~13.5-14s @ 110mph+.
Carnut, a power run shouldnt be more than £25-40, just for power run you don't need the RR to be BEC knowledgeable but make sure they work out
how they are going to do the roll-down test with a sequential gearbox before they start otherwise they can end up clattering gears and making you
wince whilst trying to find neutral (voice of experience!)
so thats why the becs are so quick up to the 60 mark then aftre that aero dynamics kick in( never thought about that)
chris
Its just about grip...
because the et speed is measured at the finals..an heavy car will because of its grip acelerate better once on speed....
we will move faster from standing..
also we need to took @ bhp figures because with more bhp your top speed will always be higher.....
Sow an cosworth with 240Bhp will have an high terminal speed, but will spent very much time on getting on speed, for us its in reverse..(fast On speed
but low top speed)
i think that in the first 4-6seconds of the launch weight/grip rate is very important..
after that its just BHP against resistance(air)...
also i think that the BEC is more time on 80+mph than the cosworth wy? because its faster on the 80mph..(resulting in an low ET time)
but then it grows slower..and the cosworth will still be pulling...(resulting in an highet ET speed)
the et time goes allong with the average?
The shorter the distance the more advantage will have the BEC/Locost....
its like the F1 against the Jet Fighter....
its about weight / grip ratio...
The jet fighter tops out the F1 on lets say 1400Km/h difference.. but because of its weight and bad tracion....it just needs time to put the energie
in his mass....
don't unther estimate the force of an Turbine! they have an very very high torque level and then when they turn on afterburner its even 170%! sow
its just is weight...
Tks
quote:
Originally posted by tks
Its just about grip...
quote:
Originally posted by tks
Its just about grip...
because the et speed is measured at the finals..an heavy car will because of its grip acelerate better once on speed....
we will move faster from standing..
also we need to took @ bhp figures because with more bhp your top speed will always be higher.....
Sow an cosworth with 240Bhp will have an high terminal speed, but will spent very much time on getting on speed, for us its in reverse..(fast On speed but low top speed)
i think that in the first 4-6seconds of the launch weight/grip rate is very important..
after that its just BHP against resistance(air)...
also i think that the BEC is more time on 80+mph than the cosworth wy? because its faster on the 80mph..(resulting in an low ET time)
but then it grows slower..and the cosworth will still be pulling...(resulting in an highet ET speed)
the et time goes allong with the average?
The shorter the distance the more advantage will have the BEC/Locost....
its like the F1 against the Jet Fighter....
its about weight / grip ratio...
The jet fighter tops out the F1 on lets say 1400Km/h difference.. but because of its weight and bad tracion....it just needs time to put the energie in his mass....
don't unther estimate the force of an Turbine! they have an very very high torque level and then when they turn on afterburner its even 170%! sow its just is weight...
Tks
