How to calculate top speed

dvollebregt · Mar 20, 2014

Hi all,

I just bought my first series III. The car has quite some modifications.
It has overdrive, range rover classic diff, 200 diesel engine and larger tires but I feel like it lacks power in 4th(overdrive gear) my current top is around 55mph with the right wind.

How can i calculate my top and what is better to fit the old or range rover diff(impact)? Should i try to find the turbo for the 200 diesel aswell? What is the expected impact?

I found this site : Engine RPM Calculator

But I cannot find out how it works.

Thanks

Duco

monkfish24 · Mar 20, 2014

Is that 55mph on the speedo or via gps?

samc88 · Mar 20, 2014

Should be more than 55. I was cruising on the dual carriageway with standard diffs, overdrive and with a 2.5 N/A fitted (only 6 more hp than standard) and I was easily getting over 60 and I wasn't flat out.

dominicbeesley · Mar 21, 2014

When mine says 55 its doing about 80. If your speedo hasn't been recalibrated and you're running different diffs and bigger tyres that'll be it....just hope you've not passed any speed cameras...

SPEED * old diff ratio / new diff ration * a bit for bigger tyres =>
55 * 4.7/3.54 * 110% = 80.32

blue beasty · Mar 21, 2014

Mines a completely standard set up and 55 on the clock is about 62

blue beasty · Mar 21, 2014

just re-read the OP and you're over geared. A 200 Di should put out about 80bhp and push a Series along at 65-70mph reasonably comfortably with either rangie diffs or an O/D not both. Even if you fit a turbo it'll struggle in 4thO/D.

You don't say how much bigger (taller) the tyres are but that won't help either.

What's it like if you save the O/D for between 3rd and 4th on hills? Remember it's a tratter not a motorway cruiser.

BTW..... :welcome:

blue beasty · Mar 21, 2014

My advice is pull the O/D off....they're rubbish and not worth the hassle...

I'll give ya 20 quid fer it

dvollebregt · Mar 21, 2014

Owhke thanks! Could it be possible that the ooverdrive would kill power on the highway, so the engine would loose power but that it needs to work a bit less?

If i go on the highway and just drive without the use of the overdrive i can try to cruise at a higher speed, just using the diffs?

Duco:clap2:

Freetime101 · Mar 21, 2014

blue beasty said:
My advice is pull the O/D off....they're rubbish and not worth the hassle...

I'll give ya 20 quid fer it

I'll give £21

I would download a speedo app for your phone or use a gps and drive flat out along a motorway (or until you reach the speed limit

) with and without the overdrive and compare it against the Landy's speedo

dominicbeesley · Mar 21, 2014

Not sure how gutless a tdi without turbo is but I run a petrol with 3.54 diffs and over drive and it is fine. Over drive is also useful as a splitter so 3+OD is the same as original 4th, then 4th is like overdrive without RR difss 4th+OD is like an extra gear. If you don't engage overdrive it doesn't do anything bad. They just want your OD!

As stated get a GPS app and check your speed it is very very unlikely that your speedo will be right if the diffs have been changed...

samc88 · Mar 21, 2014

blue beasty said:
My advice is pull the O/D off....they're rubbish and not worth the hassle...

I'll give ya 20 quid fer it

Hmmmm . nice try there BB

Has your ambulance not got one fitted?

nickjaxe · Mar 22, 2014

I run a S3 with the 200di...70mph no probs...I would also say bin the o/d if your have 3.5 rr diffs...over-geared,

In general how does it perform at lower speeds,

As stated check the speed with GPS.

Nick.

blue beasty · Mar 23, 2014

samc88 said:
Hmmmm . nice try there BB Has your ambulance not got one fitted?

Nope

be a while before I'll have the readies. Sits at 60 happily enough with the 10P purring but would sit at 60 a lot cheaper with an O/D. Useful to have the added choice on hills anorl if I can find one that don't scream like a banshee

dvollebregt · Mar 23, 2014

I have two explanations,

1 overgeared
2 bad fuel injections adjustment

I measured the 55 with gps, I will try to check today to measure with gps.

I live near the nuclear top Europe meeting and all the roads are closed for a few days.

thanks!

NiteMare · Mar 23, 2014

my 200tdi powered 109 van body with 3.54 diffs and od will clear 80mph with 3 or 4cwt in the tub (always got some weight in there) and 7.50 tyres and would pull my old caravan past 60mph (turbulence/drag killed the top speed and mpg though)

my 88" truck cab 200tdi powered will touch 85mph from J7 towards J6 of the M6 with a tatty 3/4 tilt fitted and slowing me down, again 3.54 diffs, od and 7.50 tyres (90mph without the tilt)

body styles and bolt on bits can have quite an effect on performance but 55mph does seem a touch extreme, have you got any brakes dragging ?? what tyre style/size/pressure do you have ??

i've not driven one without the turbo fitted so i can't really suggest much else

How to calculate top speed

dvollebregt

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monkfish24

Well-Known Member

samc88

Drivels spiritual representative

dominicbeesley

Well-Known Member

blue beasty

Leaks an prone to bits dropping off

blue beasty

Leaks an prone to bits dropping off

blue beasty

Leaks an prone to bits dropping off

dvollebregt

Member

Freetime101

Active Member

dominicbeesley

Well-Known Member

samc88

Drivels spiritual representative

nickjaxe

Well-Known Member

blue beasty

Leaks an prone to bits dropping off

dvollebregt

Member

NiteMare

New Member

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