smart51
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| posted on 16/2/06 at 09:27 AM |
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quote:
Originally posted by Sean
How about a good old V8? All that torque...
All that torque in a light weight car = big wheel spin. A lower torque, higher revving engine is a better way of getting the power in a seven.
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NS Dev
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| posted on 16/2/06 at 10:37 AM |
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quote:
Originally posted by billy
you cant beat the powa of the old xe  ask ned
SECONDED!!!!!!!!!!!!!!!!!!!!!!
Get an XE in it! Won't be cheap, but will be quick.
We ran a caterh*m HPC vauxhall up with some datron gear on it a while back so accurate figures. Completely standard vauxhall XE in it but with 48mm
jenvey throttle bodies and a decent exhaust manifold (BTB one I think) and some sticky tyres and got consistent sub 4 secs.
Average 0-60 was 3.9 secs over 10 runs, don't think that's too bad really!!!!
Do the maths on the power to weight, the only bike engine (in std form) that can really beat the equivalent car fitted with the XE engine (in std form
on throttle bodies) in terms of power to weight, is the Hayabusa, and then it's not by much.
Yea, I like the revviness and sequential gears with the bike setup, but I like the fact that the XE can be a pussycat cruiser one minute and then
really brutal when you need it to be!
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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britishtrident
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| posted on 16/2/06 at 11:06 AM |
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quote:
Originally posted by smart51
quote:
Originally posted by Sean
How about a good old V8? All that torque...
All that torque in a light weight car = big wheel spin. A lower torque, higher revving engine is a better way of getting the power in a seven.
For the same performance you get the same wheel spin (with reason).
Who would want to fit a wheezing ancient Rover-Buick V8 anyway even in the 60s it was grossly over rated.
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NS Dev
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| posted on 16/2/06 at 11:59 AM |
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Not necessarily BT!!!
Once again, I'll quote something I wrote on here ages ago!
"""The fact is that you need an engine with a power/torque curve which approximately matches the ability of the wheels to put that
torque on the road.
Having loads of torque at low revs is of no practical advantage in a seven because the laws of physics (and therefore the traction that can be
obtained) mean that the maximum torque that can be transmitted to the road via the driven wheels is very low.
As wheel rpm increases, you can transmit progressively more power (same TORQUE!) through the driven wheels.
What you really need is an engine with a very wide power/torque band and a very big rev range.....................but then that's what we are
all trying to achieve!!
As was pointed out, all the reasonably powerful engines can spin the wheels of a 7 with relative ease, the difference is that most of them have bigger
rev ranges and their torque tends to fall from the bottom of the power band to the top, hence whilst accellerating, the likelihood of breaking
traction decreases with speed through each gear.
Here the v8 becomes a problem as it's rev range (for the cheaper end of the market!) is limited, and in each gear the torque tends to build to a
peak and then fall off again (remember that for any engine, the power and torque curves (in bhp and ftlb) cross at 5250 rpm, how does that compare to
peak rpm, if it's near the limiter then all your driving will be on the increasing part of the torque curve!!)
The next problem is that with that limited rev range, the time until the next gear is short, and then the problem is repeated all over again!!!
Now contrast that to a revvy 4 cyl or 6 cyl engine (I know this is not scientifically correct, but I am referring to commonly available engines, not
the "ideal world"!) where (for my Vauxhall XE for example) the working rev range is basically 5000rpm to 7500rpm. Torque peaks at around
5000rpm (as it does for most roughly square bore-stroke 4 cyl engines) and then falls all the way to 7500rpm, but the power peaks at 6500rpm ish. This
means that if you can get away from a standing start fairly cleanly, traction should increase through the rev range, whereas with the v8 it will
actually decrease. """
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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Sean
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| posted on 16/2/06 at 01:05 PM |
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I see your point about a V8 but hey, there has to be some of us who like the retro nature of the "wheezy V8 ". Still you only need 2
gears. Pull off in second and then to fifth. Casual and relaxed. Much less hectic. Seriously though, all the engines mentioned have their benefits.
Bike for track days must be sentational, but for a lazy summer's drive the burbling V8 everytime.
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donut
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| posted on 16/2/06 at 01:26 PM |
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Here are a couple of pics of my R1 carbs attached to a Bogg Brothers ally inlet manifold.
Image deleted by owner
[img][/img]
Andy
When I die, I want to go peacefully like my Grandfather did, in his sleep -- not screaming, like the passengers in his car.
http://www.flickr.com/photos/andywest1/
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NS Dev
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| posted on 16/2/06 at 01:32 PM |
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quote:
Originally posted by Sean
I see your point about a V8 but hey, there has to be some of us who like the retro nature of the "wheezy V8 ". Still you only need 2
gears. Pull off in second and then to fifth. Casual and relaxed. Much less hectic. Seriously though, all the engines mentioned have their benefits.
Bike for track days must be sentational, but for a lazy summer's drive the burbling V8 everytime.
Yep fully agree, unbeatable for summer picnic cruises and those drives out for the sake of it that make summers so lovely!!!......can't wait!
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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smart51
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| posted on 16/2/06 at 01:54 PM |
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quote:
Originally posted by britishtrident
All that torque in a light weight car = big wheel spin. A lower torque, higher revving engine is a better way of getting the power in a seven.
For the same performance you get the same wheel spin (with reason).
Not so. Wheel spin is a function of torque at the wheel versus tyre grip on the road. A low revving high torque engine will put more torque on the
wheel but for a shorter time, then you have to change into 2nd gear. A low torque, high revving engine will apply less torque on the wheel but for
more time, you won't have to change gear so soon. Both will give similar overal acceleration but the high torque engine is more likley to wheel
spin.
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Lippoman
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| posted on 16/2/06 at 03:24 PM |
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Power vs. Torque
quote:
Originally posted by smart51
A low torque, high revving engine will apply less torque on the wheel but for more time, you won't have to change gear so soon. Both will give
similar overal acceleration but the high torque engine is more likley to wheel spin.
Torque is a function of power and speed, so if an engine has more power at a certain speed, the torque at the wheels is higher. It's basically
all about the gearing.
What you should compare when looking at engines are the power curves, put them in a diagram where the X-axis is percents of rpm-range. The one with
the greatest area in the usable range is the one that will be pulling away, when you gear them correctly...
[Edited on 16/2/06 by Lippoman]
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NS Dev
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| posted on 16/2/06 at 03:49 PM |
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Which is what I said further up the thread here:
quote:
Originally posted by NS Dev
Not necessarily BT!!!
Once again, I'll quote something I wrote on here ages ago!
"""The fact is that you need an engine with a power/torque curve which approximately matches the ability of the wheels to put that
torque on the road.
Having loads of torque at low revs is of no practical advantage in a seven because the laws of physics (and therefore the traction that can be
obtained) mean that the maximum torque that can be transmitted to the road via the driven wheels is very low.
As wheel rpm increases, you can transmit progressively more power (same TORQUE!) through the driven wheels.
What you really need is an engine with a very wide power/torque band and a very big rev range.....................but then that's what we are
all trying to achieve!!
As was pointed out, all the reasonably powerful engines can spin the wheels of a 7 with relative ease, the difference is that most of them have bigger
rev ranges and their torque tends to fall from the bottom of the power band to the top, hence whilst accellerating, the likelihood of breaking
traction decreases with speed through each gear.
Here the v8 becomes a problem as it's rev range (for the cheaper end of the market!) is limited, and in each gear the torque tends to build to a
peak and then fall off again (remember that for any engine, the power and torque curves (in bhp and ftlb) cross at 5250 rpm, how does that compare to
peak rpm, if it's near the limiter then all your driving will be on the increasing part of the torque curve!!)
The next problem is that with that limited rev range, the time until the next gear is short, and then the problem is repeated all over again!!!
Now contrast that to a revvy 4 cyl or 6 cyl engine (I know this is not scientifically correct, but I am referring to commonly available engines, not
the "ideal world"!) where (for my Vauxhall XE for example) the working rev range is basically 5000rpm to 7500rpm. Torque peaks at around
5000rpm (as it does for most roughly square bore-stroke 4 cyl engines) and then falls all the way to 7500rpm, but the power peaks at 6500rpm ish. This
means that if you can get away from a standing start fairly cleanly, traction should increase through the rev range, whereas with the v8 it will
actually decrease. """
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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Lippoman
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| posted on 16/2/06 at 04:42 PM |
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NS Dev: Not quite
You're still mixing power and torque in that post. Torque is just an expression of power.
Torque = Horsepower x 5252 / rpm
If you enter the rpm at the wheels, you get the torque at the wheels. If you enter the rpm at the engine, you get the torque at the engine.
Torque depends on gearing, power is constant (minus losses).
An excess of power at the wheels is controlled by throttle or by spin control. If you optimise the power curve for low gears you will have less power
than traction in the higher gears.
__________________________________________
Which is the most important nut in a race car?
The one holding the steering wheel.
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dern
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| posted on 19/2/06 at 04:14 PM |
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All these tales of lazy v8s suitable for a summer evenings drive don't really match my experience of the 300bhp 4.6l rover v8 in my
westfield.
Can't wait to finish the bec to compare the 2.
Regards,
Mark
R1 (2003 FI) powered Locost in progress
Fireblade/Impreza
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jon_boy
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| posted on 19/2/06 at 06:26 PM |
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Or get a ca18det from a 200sx. Mine cost £150 then £40 for a norris design stage one chip, £150 for a T3 turbo and gubbins to fit, air filter etc.
Easy 250 plus bhp. I have done it all myself and reconned it to make sure it doesnt pop but it should be a luagh when its in. Just have to build the
car now...
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