top speed part deux!!

[Anonymous]

Right then i have been reading the top speeds post and i want to know what is wrong with my 1.3 sr i see 1.2's reading 110 and 1.4's reading 130 but mine struggles to get past 95/100 - whats causing this???

[Anonymous]

all do... mine wont do more than 115 on a straight stretch

speedos read wrong a lot

[Anonymous]

no mods done 2 your engine have you???

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[Anonymous]

that's probably accurate mate...when people say "my 1.0 does 300mph in 2nd" it's cos nova speedos are inaccurate

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[Anonymous]

top speed is irelevant on a small car. its all about how quickly you can get it there and if it can hold the speed well.

BEng Hons Automotive Electronics Engineering :) worship my electronics skills :D

[Anonymous]

I agree with Cambridge on his last comment. The most important thing is acceleration, thats where its at. When I say my 1.4 would do 120 easy and struggle on to 130 down hill, my motor was very highly modified. I spoke to a lad the other night with a 1.3 sr with just a back box and he said to me that his car does 140mph. I made no comment, coz there is a possibility that his speedo is that far out, but I had a little laugh after he had left.

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[Anonymous]

140 ? But the speedo only shows upto 120! lol

[Anonymous]

yeah well, my GSi can do 200mph now that it doesn't have a big scoop on the front slowing it down!!!! :D

Mmmmm forbidden donut. :)

[Anonymous]

yeah cos its got those 4 speed holes on the bonnet !
mine never does over 70 ;) so i don't know the top end. lol

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[Anonymous]

They actually show 130mph, and he was guestimating on how far the needle goes past the end of the clock, lmao!

Whilst I was playing with a vtec honda a while back I managed with a lot of effort on a down hill stretch to go off of the clock (in the 1400) And as a friend of mine finally caught up I told him how fast I had just been, and he replied "me 2 I went off the clock!" It took him almost 5 minutes to catch us up and he still didn`t twig that his clocks must be reading high! His car is also a 1300sr (back box only). It must just be something about 1.3sr`s coz everone I speak to says they can get their one off of the clock.

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[Anonymous]

it depends on the size of your wheels too, the speedo will be inaccurate on a nova with 16"s it will read slightly fast the faster you go.

i think thats right anyway ( trying to remember what was written in redline a while ago )

[Anonymous]

Other way around.if your car is travelling at a set speed, the smaller the wheels, the faster they have to turn. Your gearbox will also turn faster and so the speedo does and it then reads high. I`ve gott 15"55, cp has 16"45 and My mate has 16"45 on his GSi. CP and my clocks read the same, but the GSi with the same size rubber reads a lot faster. We all ahve 1600`s with f13cr boxes.

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[Anonymous]

sorry mc. the larger the wheels the faster the outside edge is traveling, to keep up with the centre of the wheel. its all to do with angular velocity and physics

BEng Hons Automotive Electronics Engineering :) worship my electronics skills :D

[Anonymous]

surely if you have a smaller wheel it has to turn more times to get the same distance as a big wheel?!?! so this would mean MC is right. I think, I may just be confusing myself here!!!! :)

Mmmmm forbidden donut. :)

[Anonymous]

If the outside edge is travellin faster, then the car would also go faster. Your theory breaks down there.

You is thinkin the wrong way round. Dont think of the engine turnin the wheels, think of the wheels turnin the engine. Little wheels have to turn a lot faster to match the speed of large wheels. We are talking rpm not outside edge speed. If the wheels need to turn faster to match the outside edge speed, then the entire drive train will also be going faster and the speedo will read faster, but the actual road speed is still the same.


Dont talk to me about Physics, I had enough of that when I went to University. boo hiss!

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[Anonymous]

yep, smaller wheels means higher reading!!! If u want to know the 'real reading' from ur speedo post ur wheelsize and profile here and il work it out for ya. i posted this last year on howto work it out!!
My 1.3sr would say almost 120 downhill (110 on the level) for top speed, but with my new engine it will do 125 on straight and goes until the needle cant go any further (straight down) with a bit of a bank!
I reckon its gotta b at least 10% out.
Dicko

[Anonymous]

Go on then, what speed am I doing if the clox read 70mph on 205/40/17`s?

[Anonymous]

you cant do it like that, you need engine rpm. If you know rpm, and gear ratio, you can work it out.

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[Anonymous]

i got go faster stripes that adds 25mph to the speed

[Anonymous]

So you can now get 27mph eh Waynetta!

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[Anonymous]

Or you could think of it as 'if car A has larger diameter wheels and tyres than car B, i.e. car A has a larger rolling circumference. One full rotation of Car A's wheels will make that car travel further on the road than that of car B - after all it has a larger rolling circumference, right? This means that for the same indicated speed (assumption: both cars have identically calibrated speedos/gearboxes) car A will *actually* be going faster.' So bigger wheels means the speedo will be under reading - Hmm I think thats right anyhow, ah who cares!

You can tell I am really bored!!

Ben.

[Anonymous]

Nice and simple my 2.0 would pull off the clock on 15" wheels. And I mean with the needle bouncing off the pin!!!. Now with 16" it'll almost get to the pin, the spedo lies because of the wheels. It's illegal for car manufacturers to make speedos under read so they make them over read.:D