mackie
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| posted on 24/9/03 at 10:57 AM |
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I've not had the pleasure of a ride in a V8 7 but I will! Give us about 18 months  Maybe.. 
I've read reviews of the Wesfield SEight and they usually contain "insane, stupendous, spits fuel at you" etc. Mind you that's
with 270bhp. We are going with a standard 3.5 out of an SD1, can't really afford to do much more than change the cam for a "fast
road" really but that should still give us 160-170bhp and over 200lbft of torque at a guess. Maybe in future we can upgrade it with such things
as a Weber 4-barrel and higher compression pistons etc. That's if we feel the need for more power, no doubt we will 
[Edit]
I'd be fascinated to drive an S2000 powered 7 of some description though. I had a Civic Type-R for a month and was smitten by that engine and
'box. S2000 is better still!
I'd not imagine that being low cost though.
[Edited on 24/9/03 by mackie]
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Simon
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| posted on 24/9/03 at 11:49 AM |
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Julian,
Quick point to bear in mind:
Rover V8 and box etc £350 upwards
Hayabusa engine £3500, plus Turbo £4000
If you've the money, the choice is yours and you won't hear a bad word from anyone on here
I'm going for a V8. I don't expect it to be spectacularly quick, but certainly enough to amuse me.
Plus there's the bonus of two exhaust pipes within 4' of me ear 'oles.
Fantastic.
ATB
Simon
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ijohnston99
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| posted on 24/9/03 at 01:25 PM |
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quote:
Now does anyone have a scrapped evoVII ?
These guys might!!!!
http://www.glenburgie-subaru.co.uk/
[Edited on 24/9/03 by ijohnston99]
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Julian B
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| posted on 24/9/03 at 09:21 PM |
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As Simon has quite aptly pointed out there is another factor higher than torque or bhp to be taken into account.
It’s the pound to smile ratio.
Buying a £50 fiesta and extending the brakes, pedals and steering, and welding a swivel chair to the roof and driving it from there would achieve a
very high pound/smile ratio. Do the same with a STI Impreza and the factor goes down.
I’m not a Robin Hood apologist but it’s this factor alone that sells their cars.
1300 escort engine tied upto a paper cup..... yes please!
Cheers all
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kiwirex
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| posted on 26/9/03 at 09:04 AM |
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I'm a torque man myself.
When I'm wasting the boy racers at the lights I like it to sound like I'm not really trying.
- Greg H
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Desmo904
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| posted on 26/9/03 at 10:16 AM |
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Having been riding Bikes for about 20 years, I know a lot more about M/cycle dynamics than I do about the same issues concerning cars.
There is a school of thought that says bikes with big V-twin engines (high torque - lower revs) enjoy better traction and "driveability",
especially exiting corners.
Because of this, the bike is easier to ride quickly. High revving, high power 4 cylinder engines tend to produce power which is less manageable,
danger of high-side crashes etc. (This is where the rear tyre breaks traction)
I wonder if the same is true for cars?......
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blueshift
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| posted on 26/9/03 at 12:29 PM |
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As I understand it, yes it is. When you have a turbo or somesuch that gives you a very peaky bhp curve, you can get caught out accelerating out of
corners and, in a rear wheel drive, lose the back end.
aiui this is why 200SX's have an amount of respect (and high insurance group) attached to them
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timf
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| posted on 26/9/03 at 01:26 PM |
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i opted for the v8 but not rover
chevy v8 producing 420 Bhp and 440 lbft and able to rev to 7000 rpm.
BTW for those in the ipswich area look out for a black jeep renagade. It's the wifes car and she's currently got this engine in it as i
blew her's up last week.
hehe you can lay 4 strips of rubber in 3rd when the things got 4wd engaged and you floor it so should be fun in the 7 thing.
Tim
[Edited on 26/9/03 by timf]
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mackie
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| posted on 26/9/03 at 01:40 PM |
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Your sir, timf, are a complete nutter
How much does a motor like that cost?
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timf
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| posted on 26/9/03 at 01:51 PM |
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parts "Imported" from the states during business trips £2500 machining etc £500
dyno time and setup £250
total £3250 not including my assembly time
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mackie
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| posted on 26/9/03 at 02:08 PM |
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Not so bad I guess. There's a UK outfit, I forget their name but they supply large ford and chevy engines for around that cost. That's
very silly power to have in a 7 though. More poke than even hicost himself.
Is it an iron block?
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smart51
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| posted on 26/1/05 at 07:28 PM |
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Force = mass x acceleration
Torque = a turning force
therefore torque (at the road wheels) /weight of vehicle & driver = acceleration.
Torque at roadwheels = flywheel torque * gear ratio (box and diff)
Power = torque x rpm
RPM means that you can stay in each gear for longer before you have to change up. higher gears = less acceleration.
scenario 1
two identical cars, both weigh the same.
engine 1 = 100Nm at all revs and 7161 RPM red line. this gives 100BHP
engine 2 = 100Nm at all revs and 14322 RPM red line giving 200 BHP.,
in a drag race, these cars would accelerate at the same rate off the line. at about 32MPH, car 1 would hit the rev limiter and have to change into
2nd gear. the 1/2 second wasted changing gear means that car 2 is ahead. car 1 is now in 2nd and is accelerating less than car2. by the time both
cars get to 62MPH car 2 is ahead. why? car 2 still has the same torque at the road wheel because in 1st gear the gearbox multiples the engine torque
more.
scenario 2
two identical cars, both weigh the same.
engine 1 = 100Nm at all revs and 7161 RPM red line. this gives 100BHP
engine 2 = 50Nm at all revs and 14322 RPM red line giving 100 BHP.,
in a drag race, car 1 would accelerate much faster than car two to about 32MPH, car 1 would hit the rev limiter and have to change into 2nd gear.
the 1/2 second wasted changing gear means that car 2 is catching up. car 1 is now in 2nd and is accelerating less than car2. by about 50MPH they are
neck and neck. By 60 MPH the high reving car is ahead. why? car 1 wasted 1/2 a second changing gear. car 2 had ON AVERAGE more torque AT THE ROAD
WHEEL.
it is the area under the torque curve and the gear ratios that give acceleration. a car engine may have more height on a torque graph but it hass
less width (1000 - 6000 RPM typically). A bike engine may only have 2/3 of the torque for the same BHP as a car BUT it will rev from 1000 - 12000 RPM
- more than twice that of a car.
given optimum gear ratios in each, a bike engine has more road wheel torque than a car engine over a broad range of speed and so is faster. The fact
that a bike engine is lighter also helps.
If you prefer 0 - 30 times over 0 - 60 then a car engine is for you.
If you enjoy changing clutches for fun and want to spend your time pushing your car in reverse then a bike engine is for you.
you pays your money, you takes your choice.
[Edited on 26/1/05 by smart51]
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craig1410
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| posted on 26/1/05 at 10:58 PM |
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Guys,
I agree with the approach which smart51 has taken and would emphatically agree that it is AVERAGES which are important, not peak or instantaneous
power or torque. The area under the curves are useful when understanding this stuff.
However, I personally find it much easier to work with BHP than torque when calculating this stuff and using it to estimate expected performance
figures. For a start the BHP curve tends to be a "simpler" shape and it is easier to find the area under it than with the torque curve,
especially with "peaky" engines. Bear in mind that power is simply the rate of delivery of energy and energy is related to velocity and
mass by this equation:
Kinetic Energy = (mass x velocity^2)/2
By rearranging this formula you can easily show the relationship between BHP and Velocity which is very handy for 0-60MPH or 0-100MPH calculations.
BUT, don't use your PEAK power figures when calculating this, you must use the AVERAGE power figure within the band defined by the spacing of
your gear ratios. If a gear change from 1st to 2nd drops revs from 6000 to 4500 then this is your working range. If you have a rolling road power plot
for your engine then you can easily calculate the average power output over this range and use it to work out 0-60 times.
In practice you will find that the AVERAGE power can be estimated as a fraction of PEAK power based on the type of engine. If expressed as a
percentage of PEAK power, you will tend to find that a peaky engine will have a lower percentage than a big lazy V8 or a diesel engine. Highly tuned
engines tend to be optimised to work well at particular RPM and it is essential to match this "power band" as it's often called,
with a suitable gearbox to ensure that the engine doesn't fall outside this band. This is why highly tuned engines need more gears and more
gearchanges to get the best from them. Conversely this is why big capacity V8's tend to be easy to drive fast because the engine produces a
large proportion of peak power even outside the classic "power band"
I'm building with a Rover V8 3.5 litre by the way and I just can't wait to get it running...
Cheers,
Craig.
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Lawnmower
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| posted on 27/1/05 at 12:16 AM |
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quote:
Originally posted by craig1410
Guys,
I agree with the approach which smart51 has taken and would emphatically agree that it is AVERAGES which are important, not peak or instantaneous
power or torque. The area under the curves are useful when understanding this stuff.
However, I personally find it much easier to work with BHP than torque when calculating this stuff and using it to estimate expected performance
figures. For a start the BHP curve tends to be a "simpler" shape and it is easier to find the area under it than with the torque curve,
especially with "peaky" engines. Bear in mind that power is simply the rate of delivery of energy and energy is related to velocity and
mass by this equation:
Kinetic Energy = (mass x velocity^2)/2
By rearranging this formula you can easily show the relationship between BHP and Velocity which is very handy for 0-60MPH or 0-100MPH calculations.
BUT, don't use your PEAK power figures when calculating this, you must use the AVERAGE power figure within the band defined by the spacing of
your gear ratios. If a gear change from 1st to 2nd drops revs from 6000 to 4500 then this is your working range. If you have a rolling road power plot
for your engine then you can easily calculate the average power output over this range and use it to work out 0-60 times.
In practice you will find that the AVERAGE power can be estimated as a fraction of PEAK power based on the type of engine. If expressed as a
percentage of PEAK power, you will tend to find that a peaky engine will have a lower percentage than a big lazy V8 or a diesel engine. Highly tuned
engines tend to be optimised to work well at particular RPM and it is essential to match this "power band" as it's often called,
with a suitable gearbox to ensure that the engine doesn't fall outside this band. This is why highly tuned engines need more gears and more
gearchanges to get the best from them. Conversely this is why big capacity V8's tend to be easy to drive fast because the engine produces a
large proportion of peak power even outside the classic "power band"
I'm building with a Rover V8 3.5 litre by the way and I just can't wait to get it running...
Cheers,
Craig.
So your saying a diesel is similar to a Rover V8
The vauxall 1.7dti I drive is a very peaky (at least to me) engine, ith the best accelaration in 1st, 3rd, and 5 gear at least in my opinion.
what ways are there of flatenning the bhp peak, but increasing the width to make it more drivable (particulay for diesels)?
I agree with the comment about turbos kicking in on roundabouts corners etc. a bit dodgy
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NS Dev
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| posted on 27/1/05 at 09:56 AM |
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Crikey, for once I'm impressed with a torque spread explanation! Nice one Smart51!!!
Yes, the torque spread and gearing relative to traction available are the most important to the usefulness of any level of power in a car.
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cidersurfer
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| posted on 27/1/05 at 11:25 AM |
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Guys
This is by far the best explanation that I have seen for BHP/Torque explanation.
Go down to Technical Articles and see Power and Torque 1, 2 & 3
Puma
HTH Chris
shimming solid lifters is a job for a friend...
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Dale
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| posted on 27/1/05 at 12:25 PM |
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Proper turbo sizing for an engine can smooth that torque curve out so it is not nearly so peaky. You can get full boost at 2500rpm or at 5000rpm.
Its all in sizing and what your intensions for the car are. In a car this light I am leary of going to a bigger than stock turbo which could give a
BEC performance over a smaller turbo which can give good hp and high torque almost across the board.
Dale
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David Jenkins
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| posted on 27/1/05 at 01:03 PM |
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What a good site, in many respects!
It also gives a very good explanation for running an with a new cam at 2000 rpm, which has been worrying me a bit (I've just put one in my
engine). Lots of places tell you do it, but not why.
David
quote:
Originally posted by cidersurfer
Guys
This is by far the best explanation that I have seen for BHP/Torque explanation.
Go down to Technical Articles and see Power and Torque 1, 2 & 3
Puma
HTH Chris
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craig1410
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| posted on 27/1/05 at 01:19 PM |
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quote:
Originally posted by Lawnmower
So your saying a diesel is similar to a Rover V8
Er, no, not quite...
(I drive a SEAT Alhambra 1.9 TDI 130 by the way and it's great....BUT it is nothing whatsoever like a Rover V8. Remember you need to turbocharge
a diesel to get half decent power from it and it's only really the high compression and combustion pressures which give large torque peaks low
down the RPM range.)
What I am saying is more along the lines of, the Diesel has a flatter torque curve like a large capacity V8 and thus the BHP curve is more like a
straight slope from low revs up to peak power. On a highly tuned smaller engine the torque curve will tend to be more peaked with the result that the
BHP curve will also peak. Also, you will find that the peak torque RPM is closer to the peak BHP RPM on a highly tuned engine which tends to
exagerate the BHP peak figures but narrows the "power band". On a larger engine the peak torque is low down the RPM range (maybe as low as
2000RPM or even lower) which boosts the low RPM power figures and thus widens the power band. The downside is that you don't get as high a BHP
peak because the torque has already started to tail off after peak torque at say 2000 RPM.
I'll try to post some graphs later showing characteristics of highly tuned small engines compared to lazy larger engines to show the effect
graphically. A picture paints 1000 words and all that...
Hope this helps,
Craig.
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