3.0Lt RPM to Km/h

[chrysler62]

Hi All.

I'm just curious as to what RPM to Km/h eveyone gets.
I've got a 2002 GU 3.0Lt five speed manual. My speedo shows 110km/h and the GPS shows 100km/h with the RPM's sitting on about 2800. At 120 on the clock and 110 on the GPS the RPM's are at 3000. I've spoken to a few peolpe who's vehicle RPM's are sitting lower, however they're running with an auto trans.

Some feedback would be great.

Cheers

[megatexture]

tyre size would make a big diffrence what have u got on i can get readings but im auto also you would need to compare with another manual

[chrysler62]

Yeah I suppose I should have mentioned that. It's running standard size 265/70-16 (passenger construction not light truck).

[macca86]

My 3ltr manual at 100 km an hr is about 2600 rpm and 110 about 2800rpm ish standard tyres on mine too. Your gps is pretty d far out my hema navigator is only 2km/hr behind my speedo

[growler2058]

My 3ltr manual at 100 km an hr is about 2600 rpm and 110 about 2800rpm ish standard tyres on mine too. Your gps is pretty d far out my hema navigator is only 2km/hr behind my speedo

I woulda thought itd be the speedo out rather than the gps, my gps differs by 7kmh @ 110kmh

[the evil twin]

Yep... it will be the Speedo that is out not the GPS...

and for the OP... those RPMs versus Speedo Error (10 KPH) versus trus GPS speed sound about spot on with those tyres.

[megatexture]

from what i understand gps speeds can be 5kmph+/- out depending on satellite numbers visible.

[macca86]

my car was dyno'd about 2 months ago and next to my dads new ve ss I's say my speedo is right vs the rpm rather than my gps as megatexture said they do vary pending on available satilites and signal strength

[Rumcajs]

Mine (05 5sp manual 275/65R17) does 2500 RPM at 100 km/h and 2800 RPM at 110 km/h. Speedo and GPS are spot on minus 2 km/h (speedo is slower). When I calculate revs and speeds by gearing and tyre sizes it doesn't match, if I input diff ratio as 4.1. It does match with 4.375 diff ratio but built plate says I've got 4.1:1 diffs. Oh well why didn't I count the pinion and crown wheel teeth when I had the front diff out. Call it a professional fatigue......lol
Cheers

[the evil twin]

from what i understand gps speeds can be 5kmph+/- out depending on satellite numbers visible.


my car was dyno'd about 2 months ago and next to my dads new ve ss I's say my speedo is right vs the rpm rather than my gps as megatexture said they do vary pending on available satilites and signal strength

Nah, GPS derived speed is different to position and if you have a valid lock will be accurate to within well less than 1 KPH except maybe 1 in 10's of thousands of units.
Factors such as multi-pathing etc that do affect speed by changing the doppler shift are only a momentary issue in a moving object for speed calcs and it is LDOP (calculated position accuracy) that is the main variable affected for satellite visibilty/sig strengths/angular relationship not speed.

[megatexture]

Well whatever the case .. I’m yet to find a gps that gives constant reading even when driving steadily they still fluctuate when there is no speed change also when i purchased my gps it stated the +-5kmph difference, good for a rough idea but i wouldn’t follow it religiously

[chrysler62]

Thanks all for the info. I think the only way I can reduce the RPM on hwy cycle is to increase the tyre size . I just have make sure that it's not so large as to loose too much bottom end torque unless someone has any other suggestions.

[eric]

I have a manual 07 3lt..and put km2s on it , which were about 40mm higher than the standard wheel side by side they are 285x70x17 it threw the speedo out 2-3 ks (speedo slow) on a standard nissan gps.At 100ks its at 2400 rpms and 110 ks about 2700rpms , i find it alot better on the hyway and i think its better on fuel...hope that helps

[choppie]

Trust your GPS before your speedo, a good GPS will be within 1/10 of a km most of the time, have got 2 and compared them in various vehicles including trucks all over the country with no variations. Would check tyre size and speedo drive

Col