Remember that GPS based speedos don't respond quickly - their refresh rate is once every couple of seconds at best so although they're OK for, say, motorway use they aren't any use at all for when you're pulling out of junctions etc.

Phil

I did wonder how fast they update, the speedhut gps has a 5hz processor while a DS200 by digital speedo's uk has a 10hz , I haven't got a clue what difference that makes in real time . Speedhut's has a 0-60 feature as well, but whether it's accurate who knows?

Your car is the Typhoon ,speed six engine so very differnent the old V8 lump..

Hi folks, I've found the answer to my question, courtesy of a new GPS digital speedo.
3500rpm produces 104 mph while standard speedo says 80 mph , that's why the roof rattled a tad, but having both windows open a few inches seems to cure that.
Sorry about delay in producing an answer, took me a while to fit GPS speedo neatly and then it rained and rained, what a wonderful summer it's been.

Hi Phil, I went for a DS200 from Digital Speedos, it's seems fairly accurate when testing in my Volvo and updates within a second or so. Couple of downsides are :
1:It only comes with a cigar lighter fitment which is way to short to be of use(18 inches approx), and if you remove it I assume I will invalidate any buyers warranty.
Because the chim's socket is in the door I chopped a couple wires in to the circuit under dash and fitted a second socket on the tunnel just below middle of dash. This is where I mounted it with it's own switch so as not to drain battery, not an ideal position I know, but I can see it between handbrake and gear stick (good for a glance now and then).
2:Also the wire on the back is very close to the top of the unit and the two connectors GPS and 12v are quite bulky and and wired close together so you have to make quite a large hole to get them through.
3:Instructions are a little vague and I think converted from Italian.
That said it does work well, it has a auto light sensor, a speed warning feature that flashes a small red light and it's a damn sight more accurate than the original,but bang goes my excuse if I get pulled for speeding.

Indeed it does.
If I recall correctly (it was around 0430am), I was reading roughly 90mph at 3000rpm but this was only for a few seconds as I wanted to check 3500rpm results. It just amazed me how far out the standard speedo was, it seems fairly close at sub 60 mph speeds, but 70 upwards, it as if the needle hits a wall.

Same here - really must get it sorted.

I find it's handy for scaring teh sh*t out of our American colleagues when they come over here ...

...I take 'em out for a curry and they see what appears to be me passing police cars at 100mph and think I'm an outlaw!

Phil

errrr....but you mostly are.

Best keep quiet - love it.