MPH per 1000 RPM?

[Boanerges]

I can't find the official figure anywhere.  Can anyone help?

Our 2005 1.4 SE seems to be doing around 20mph/1000rpm in fifth. Does this sound about right?

Thanks,

Brian

ps cleaned the EGR valve yesterday 'just in case'. What an easy job! Thanks to all the members who posted DIY instructions.

[guest869]

20 mph per 1000 does seem a little low, but it is a small engined car designed for more town driving.

I would always aim for about 20mph per 1000rpm for the cars I built (big engine small car) but they were more for acceleration and not motorway crusing. On the motorway they were not ideal.

Measure the tyre circumference, find the gear ratios and work it out. Or there will be websites that will do it

John

[Boanerges]

Thanks for the advice, John.  I didn't think to look on the Web for a formula. 

Using the one found here:  http://www.tomstickland.co.uk/astra/homework/hwork.htm#gearing   I measured my wheel diameter as best I could at 570mm and here's the working:

V(mph) per 1000rpm = 117.09 x Wheel diameter in metres
                                           gear ratio x final drive ratio

If I have done the maths right, this gives: 117.09 X .570
                                                          .805 x 4.111

                                                       = 66.7413 
                                                          3.309355

                                                       = 20.167 mph per 1000rpm.

Conclusion: "No, my clutch isn't slipping. Hurrah!" 


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This is even easier and confirms my 20mph/1000rpm as being correct.

http://www.car-videos.net/tools/speedrpm.asp

So, when the engine is producing maximum torque at 2,800rpm, the car will be doing 56mph.