U chat more waffles than birdseye! Unless ur right and my speedo is wrong then my times r right. Im hardly gonna post it if I was wrong knowing ud all say it was rubbish & as for ur RS2000. Yeh thier quick and in good nick u should b under 8 easy. My m8s now got a beauty of a cossie but b4 hand his RS2000 went like shit off a shovel & it was just about standard. Seems like it must have been a friday afternoon when the mechanic finished ur engine off. But seriously is the speedo known to be inaccurate cause if it is then apologies!
Once you get over a tonne speedo's, especially in old cars, are very unreliable. Read a mag article a few months ago where they were speed testing some new Jag, can't remember why and its speedo was very accurate,
3mph over read, but it was constant. I..e it said 33, you were doing 30, it said 123 you were doing 120. They used proper equipment to get the actual speeds. Guessing they have a new way of doing it now than the old cable ;)
In news: snipped-for-privacy@posting.google.com, Jonathan Walsmley decided to enlighten our sheltered souls with a rant as follows
Right, few things. I owned the Mk5 RS2000 when it was four years old, according to every car magazine I can find from the era, AND the official Ford figures, its 0-60 time is 8.5 seconds. That's with 150 bhp, no airbags, no side impact bars, no huge great stereo. That's how they were built. Not Friday afternoon cars, that's how quick a Mk5 RS was. As for the Mk2 RS2000 being built on a Friday afternoon, well, no, it was nut and bolt restored over the best part of two years, my mechanic was me. I know what I'm doing, especially with a 2.0 Pinto. When the car was completed, it was run on the rolling road at Hodgsons in Liverpool where all my Mk2 RS's used to be set up and produced IIRC 106 bhp at the rear wheels. This means it was
*slightly* up on power on a standard RS (which produced 110 @ the flywheel), but all engine internals were standard, just well chosen standard parts. Kinda cheaply done blueprinting, done for reliability not for power.
As someone else has pointed out, most car speedos read miles out over about
100 mph anyway, I've seen 130 on the clock in a diesel turbo Sierra, 115 in a 1.0 Micra, 137 mph in a 205 GTi 1.6, even 120 mph in a 1.6 Cortina Crusader (that was a while back though).
A very well reasoned and clear explanation I must say. But guy's like that would sooner believe Max Power magazine saying "K&N rules OK!" than half a dozen experienced engine tuners who state that the performace gain from fitting only a K&N is negligable. You've probably wasted an awful lot of good bandwidth trying to tell him that.
Citroen axgt ... 103 on the speedo = 100mph on my gps. 65 on the speedo = 62mph on my gps.
My mates citroen ax 1.4 ... 105 on the speedo = 100mph on the gps. 63 on the speedo = 62mph on my gps. So theres differences between "same" cars.
Bmw 525e ... 62 on the speedo = 55 on my gps. Bmw 730i ... 62 on the speedo, 62 on the computer, 62 on the gps ..... 'cause you can press buttons and re-calibrate on my 730i. Even though it is ancient!!
Car speedometers usually overstate the speed, the amount varies from car to car but I would usually expect a few mph or maybe 10% to be a fairly typical sort of figure. This can be a lot worse on some cars and in some circumstances.
The laws for type approval require the speedo to read anything up to +10% +3 mph over the actual speed, but to read no more than exactly the speed, and these tests are run with the car set up to give the highest speed readings.
As for people who say, "my speedo is accurate", there is a simple way to think about this. The radius of the tyre determines how far the car travels in one revolution, yes?
The speedo works by counting the revolutions of the wheel (well, it measures this in the gearbox but it boils down to the same thing in practice).
If you have new tyres, they will have quite a bit more tread than worn down tyres, this is obvious, and the extra centimeter or so on the diameter of the wheel means it is travelling further with each revolution.
As a direct consequence, the speedo will vary by a significant amount (a few mph) as the tyres wear down over their life. In the same sense, tyre pressure will go up and down as they are pumped up or neglected, this will have an even larger significance to the reading on the speedometer as the flat bit under the tyre is your effective radius and this can be quite a large percentage, especially if it is nearly getting flat.
Therefore, a car with a speedometer is usually reading higher than the actual speed, because it will need to be no higher when the tyres are new and over inflated, so when the tyres are normal pressure and brand new, the speedo will be up a bit, and when the tyres are down on pressure and worn on tread, the speedo will be well higher than the real speed.
This means nobody truly has an accurate speedometer except the police, and they only have accuracy because they measured it that week and got it adjusted by technicians, which isn't usually the case for us punters, I think you'll agree.
If you can borrow a handheld GPS, this ignores the tyres, doesn't have a legal obligation to over read, and gives a fairly accurate figure when you are travelling at a constant speed. This will tell you what your speedo is more likely indicating when you are actually doing 60, and is frequently a surprise.
Apparently >U chat more waffles than birdseye! Unless ur right and my speedo is
:: Once you get over a tonne speedo's, especially in old cars, are very :: unreliable. Read a mag article a few months ago where they were :: speed testing some new Jag, can't remember why and its speedo was :: very accurate, 3mph over read, but it was constant. I..e it said :: 33, you were doing 30, it said 123 you were doing 120. They used :: proper equipment to get the actual speeds. Guessing they have a new :: way of doing it now than the old cable ;)
Maybe Datron or some GPS thing. My GPS always shows a slight difference between what it and the speedo, the speedo reading higher. And it's a fly by wire speedo too. They used to say the discrepency was a calibration or mechanical error but IMHO it's deliberate.
It's illegal to produce cars with under-reading speedos, and so to allow for the variation with tyre pressure and tread and maufacturing tolerances, manufacturers give themselves a safety margin and it is not uncommon to have speedos overreading by 10%.
There are measured miles on various roads around the country - you can time yourself against these, or you can use a GPS system to calibrate your speedo. In any case it's almost certain that the 0-60 time you measured is significantly optimistic.
That's what you'd get if the cylinder filled fully at atmospheric pressure, but you'll probably find it's somewhat less than this (you could measure the vaccum in the manifold to find out by how much). I'd guesstimate it to be about 65% of this value, although it depends on so many factors specific to your engine that that's probably wildy out.
From an engineering point of view, if you wanted to know the potential cfm rate required, then your figure would be the one to go for.
Noise is release of energy to the atmosphere. OK so you can't release energy to make power without some noise but any excess noise is wasted energy that could be put to some use.
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