shaywez
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| posted on 4/3/05 at 03:24 PM |
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bhp per tonne
Just a quick question, does anybody know the formula for working out BHP per tonne?
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ned
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| posted on 4/3/05 at 03:25 PM |
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your current bhp divided by car weight (in kg's) x 1000(kg's)
beware, I've got yellow skin
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mookaloid
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| posted on 4/3/05 at 03:26 PM |
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BHP divided by weight of vehicle in tonnes?
You speedy typer Ned
[Edited on 4/3/05 by mookaloid]
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locoboy
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| posted on 4/3/05 at 03:33 PM |
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Ie,
2.0 Zetec at 140BHP
Car weighing 700kgs
= 200BHP/Tonne
ATB
Locoboy
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DarrenW
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| posted on 4/3/05 at 03:36 PM |
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The only thing to consider if you are comparing with other people is the weight theyve used. Wet weight (all oil, water, lubricants etc and full tank
of fuel), dry weight or wet weight with driver.
I always use wet weight without driver as i believe this is the kerb weight that manufacturers quote. This should be the locostbuilders standard.
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Spyderman
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| posted on 4/3/05 at 03:43 PM |
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quote:
Originally posted by DarrenW
The only thing to consider if you are comparing with other people is the weight theyve used. Wet weight (all oil, water, lubricants etc and full tank
of fuel), dry weight or wet weight with driver.
I always use wet weight without driver as i believe this is the kerb weight that manufacturers quote. This should be the locostbuilders standard.
What would be the purpose of having a BHP/ton figure if it was kerb weight?
Are you going to make it remote control? 
Spyderman
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JonBowden
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| posted on 4/3/05 at 03:48 PM |
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quote:
What would be the purpose of having a BHP/ton figure if it was kerb weight?
If you include the weight of the driver then my cars will always be faster than most peoples since I am short and skinny.
My top speed should be better too as my head is aerodynamic.
Jon
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DarrenW
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| posted on 4/3/05 at 04:43 PM |
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What would be the purpose of having a BHP/ton figure if it was kerb weight?
Are you going to make it remote control?
Youve got me there, i must be having a thick moment. What do you mean??
Is my definition of kerb weight wrong? Sounds like it -oops. I meant the weight of the car on its own full of fuel etc but no driver so there is a
comparable between the models. Of course i say this 'cos even if i built a car with big budget weight reduction carbon fibre additions id still
be knackered cos im a fatlad!! At least using the car weight alone we get a comparison.
At the end of the day it is largely irrelevant cos torque, grip, driver ability etc make the car go fast. BHP/tonne only shows the potential and
something to brag about over a pint. Its nice to have big stats tho
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Hellfire
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 posted on 4/3/05 at 05:23 PM |
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That makes our ZX12R engined MK....
errrmmm
Max 500Kgs
Min 180bhp (at the wheel)
is that 360bhp/tonne? minimum... OMG
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Dale
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| posted on 4/3/05 at 05:57 PM |
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It looks really good (and is ) but declines rapidly with a driver and a passenger
(1000kg / 500 kg) *180hp =360hp/t
(1000kg / (500kg + {75kg driver}) *180 = 313 hp/t
(1000kg / (500kg + 150kg {driver and passenger}) *180 = 276 hp/t
its still blindingly fast but another 12% or more slower when you take a passerner out the scare the living sh$% out of them
But in the end its only number vs adreniline
Dale
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carnut
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| posted on 4/3/05 at 06:40 PM |
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I always work it out for a dry weight without driver as this is what most of the manufacturers tend to do. This allows a decent comparison.
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clbarclay
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| posted on 4/3/05 at 06:43 PM |
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Weight and power are figures that manufactures spin. Yes like politicians they can be very economical with the truth without actually lieing.
For example you can measure power at the wheels, however they often quote power at the flywheel because the higher figure sounds better.
Takeing it a level further they can quote power at the crankshaft, where they add onto the flywheel power the power absorbed by engine ancileries like
alternator, water pump and feul pumps.
The same goes for weight like has already been mentioned, for power to weight I would use wet weight less driver because any extra weight like drive,
passanger or luggage is very variable.
Even if you only use the weight of one drive, thier weight is not constant, cloths and food in the gut don't make a dig difference but it can
easily vary as much as a few Kg.
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ChrisGamlin
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| posted on 4/3/05 at 06:55 PM |
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Hellfire, you should be considerably lighter than that! Im ultimately aiming for just under 400bhp/ton with the R1 conversion (165bhp / 420kgs) -
I'll await a power readout of the engine before I stick to that power claim as the bike only puts out just over 150bhp quoted by Yamaha, but
people seem to get around that figure from a stock R1 with a nice free flowing exhaust etc, 140bhp+ at the wheels so it should be attainable.
The car was around 415kgs with the blade in, the R1 is if anything a couple of kgs lighter but I am adding a bit of weight with a few extra bits and
bobs (oil cooler etc)
Chris
[Edited on 4/3/05 by ChrisGamlin]
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carnut
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| posted on 4/3/05 at 08:41 PM |
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370kg
215bhp
=580bhp/tonne ish.
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Hellfire
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| posted on 4/3/05 at 09:40 PM |
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quote:
Originally posted by carnut
370kg
215bhp
=580bhp/tonne ish.
Yeah but don't forget, if you add the things you've missed out ie, Fluids, wheels, engine etc and recalculate your BHP/tonne, you may be
shocked.
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clbarclay
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| posted on 4/3/05 at 10:03 PM |
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Driver weight makes a considerable difference, especially if more than one driver is to use the car.
When he was still hill climbing, a friend of my father was sharing a car, he was all ways quicker than hi team mate.
1
He was lighter than his team mate.
2
The car had to have ballast added to counter balance the extra weight of the other driver.
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carnut
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| posted on 5/3/05 at 12:19 AM |
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Yes Helfire I know im being a bit over the the top but my car weighed in at 380kg at the sva and I guess i had 10kg of fuel and fluids on board.
The power figure is for the new engine (not built yet ) but I hope to have it ready for the 0-60 thing at melbourn in may.
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clbarclay
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| posted on 5/3/05 at 12:29 AM |
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quote:
Originally posted by carnut
Yes Helfire I know im being a bit over the the top but my car weighed in at 380kg at the sva and I guess i had 10kg of fuel and fluids on
board.
Just like the manufaturers then, your trying to make your car sound as good as possible.
Don't blame, I'd probably do the same.
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carnut
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| posted on 5/3/05 at 09:41 AM |
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I do the same as the manufacturers so I get a good comparison.
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Hellfire
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| posted on 5/3/05 at 03:34 PM |
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quote:
Originally posted by carnut
Yes Helfire I know im being a bit over the the top but my car weighed in at 380kg at the sva and I guess i had 10kg of fuel and fluids on board.
The power figure is for the new engine (not built yet) but I hope to have it ready for the 0-60 thing at melbourn in may.
Aaah, I see. As far as I know the SVA does not weigh the complete vehicle. They only give you front and rear axle weights and the combined weight
(which IIRC is not the actual wet weight of the vehicle). If you stick it on a public weighbridge you'll probably find you are around the 470 -
480kg mark. (Unless you've spent poo loads of cash on it to reduce weight)
We too thought the weight at SVA was the total vehicle weight without driver. However, when weighed at work on our weighbridge, it exceeded the figure
given at SVA by a significant amount.
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Dale
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| posted on 5/3/05 at 06:35 PM |
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When I weighed my rolling chassis - its heavy 1255lbs 570kg still needs bodywork and a fuel tank--I used bathroom scales with boards across them
under the wheels at each end--2 under each wheel at the back -but with a board to bring the front up to the same level as the back- and then did the
same for the front. If you did not level the car when weighing it it made quite a bit of difference as weight would transfer to the lower set of
wheels.
Either way your cars are going to fly. I am starting out with 200hp and hope to finish off after I have driven the car a bit and bump it up to the
300 to the wheels.
Dale
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NS Dev
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| posted on 6/3/05 at 09:23 AM |
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Yep, I'm hoping my Vauxhall XE on throttle bodies should put out around 200hp on std cams (the last one did!) and the car should hopefully weigh
in at under or around 600kg (no heater, screen, wipers, washers, gauges etc etc) so around 333hp/tonne+
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ChrisGamlin
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| posted on 6/3/05 at 06:27 PM |
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I'd tend to agree with Hellfire on this one Carnut, 380kgs is VERY light for a BEC unless you've done some trick things you havent told us
about?
Richard Miles's R1 Striker was a measured 390kgs (on proper cornerweight scales) and that had virtually every light bit to be found, plus a
generically (slightly) lighter chassis and an engine thats best part of 30kgs lighter than the 'bird. That car is the only Se7en style BEC I
know of thats under 400kgs, apart from that Evo Caterblade they built up a couple of years ago with carbon fibre everything. The only other one that
was around that figure was Ed Cane's Westie Megablade, but thats up around 430kgs now he's sold his Barmby wheels, ditched the ACB10s in
favour of Yoko 48s and put a cage on etc.
Chris
[Edited on 6/3/05 by ChrisGamlin]
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Peteff
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| posted on 6/3/05 at 06:47 PM |
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I took mine with a pinto engine to weigh it on the scrapyard weighbridge, the b@&tards offered me £20 for it. The combined weight for the sva
was considerably more than the actual weight of the car though. The actual weight was under 600kg and the operating weight something like 770kg. If
that's 380kg for an Indy with an engine in I'd have a look round it as you've obviously forgotten to fit some parts.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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shaywez
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| posted on 6/3/05 at 07:00 PM |
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SVA station reckon the weight of my car is 819kg, i thought this was a bit much but i am not sure. They measured the front axle first then the back
and added the 2 together. Is this the operating weight or the actual weight? Just seems a bit to much as i have no screen etc!!
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