Dekers Posted January 14, 2016 Report Share Posted January 14, 2016 ENGINE OUTPUT (PS)TORQUE (NM)CO2* (G/KM)FUEL CONSUMPTION* (MPG)dci 130 diesel 2WD MT 130 320 129 (133 with 19") 57.6 (55.4 with 19") dCi 130 diesel 2WD Xtronic 130 320 135 (139 with 19") 55.4 (53.3 with 19") dCi 130 diesel 4 WD MT 130 320 139 (143 with 19") 53.3 (52.3 with 19") DIG-T 163 2WD MT 163 240 145 (149 with 19") 45.6 (44.1 with 19") I have not seen published figures like these before, if you can fathom your way through them, it says emissions and fuel consumption are worse simply by fitting larger wheels (19") as opposed to the normal 17". Yet engine output and torque remain the same. What have I missed here, the overall size remains very similar if I'm not mistaken as the rubber is less on the bigger rim?! Can someone explain please? Many thanks. Quote Link to comment Share on other sites More sharing options...
casts_by_fly Posted January 14, 2016 Report Share Posted January 14, 2016 The weight of the actual wheel used will have gone up a bit with more metal so it takes a bit more work to get them moving. rick Quote Link to comment Share on other sites More sharing options...
Glenlivet Posted January 15, 2016 Report Share Posted January 15, 2016 IIRC by fitting bigger wheels you have changed the gear ratios, ie the engine is having to work harder/less efficiently. Quote Link to comment Share on other sites More sharing options...
Andy135 Posted January 15, 2016 Report Share Posted January 15, 2016 IIRC by fitting bigger wheels you have changed the gear ratios, ie the engine is having to work harder/less efficiently. Correct, but only if the rolling radius has increased. If bigger wheels with skinnier tyres keeps the rolling radius the same, then there should be no appreciable difference in work effort or efficiency. Quote Link to comment Share on other sites More sharing options...
Glenlivet Posted January 16, 2016 Report Share Posted January 16, 2016 Granted. Op says "very similar " and "if I'm not mistaken ". Would be good to know where the original source stats come from. Quote Link to comment Share on other sites More sharing options...
al4x Posted January 16, 2016 Report Share Posted January 16, 2016 ENGINE OUTPUT (PS) TORQUE (NM) CO2* (G/KM) FUEL CONSUMPTION* (MPG) dci 130 diesel 2WD MT 130 320 129 (133 with 19") 57.6 (55.4 with 19") dCi 130 diesel 2WD Xtronic 130 320 135 (139 with 19") 55.4 (53.3 with 19") dCi 130 diesel 4 WD MT 130 320 139 (143 with 19") 53.3 (52.3 with 19") DIG-T 163 2WD MT 163 240 145 (149 with 19") 45.6 (44.1 with 19") I have not seen published figures like these before, if you can fathom your way through them, it says emissions and fuel consumption are worse simply by fitting larger wheels (19") as opposed to the normal 17". Yet engine output and torque remain the same. What have I missed here, the overall size remains very similar if I'm not mistaken as the rubber is less on the bigger rim?! Can someone explain please? Many thanks. its fairly simple dekers, the engine power will be a bench figure and the larger the wheel the more power you need to turn it, which drops the economy and emissions. My betting is the overall diameter will be slightly larger but not much as the figures don't drop by much with the larger wheel Quote Link to comment Share on other sites More sharing options...
Dekers Posted January 16, 2016 Author Report Share Posted January 16, 2016 Granted. Op says "very similar " and "if I'm not mistaken ". Would be good to know where the original source stats come from. Current Nissan X-Trail brochure! Quote Link to comment Share on other sites More sharing options...
Dekers Posted January 16, 2016 Author Report Share Posted January 16, 2016 (edited) Correct, but only if the rolling radius has increased. If bigger wheels with skinnier tyres keeps the rolling radius the same, then there should be no appreciable difference in work effort or efficiency. That was my feeling. The overall radius must be VERY close or the speedo ratio would be out as well! Well, at least that's what I would have thought, that's why I asked! Edited January 16, 2016 by Dekers Quote Link to comment Share on other sites More sharing options...
Dekers Posted January 16, 2016 Author Report Share Posted January 16, 2016 (edited) its fairly simple dekers, the engine power will be a bench figure and the larger the wheel the more power you need to turn it, which drops the economy and emissions. My betting is the overall diameter will be slightly larger but not much as the figures don't drop by much with the larger wheel I can relate to that and would not argue, but I simply don't see the overall wheel/tyre circumference changing, maybe I'm wrong, but if it was that simple to improve fuel consumption then why isn't everything fitted with tiny wheels? However, I can't think of another reason, so perhaps the 19" rim does end up a slightly larger diameter overall, but again, what happens with the speedo ratio if that is the case? Edited January 16, 2016 by Dekers Quote Link to comment Share on other sites More sharing options...
TIGHTCHOKE Posted January 16, 2016 Report Share Posted January 16, 2016 The speedometer will be out by a few percent! Quote Link to comment Share on other sites More sharing options...
biketestace Posted January 16, 2016 Report Share Posted January 16, 2016 Speedometers are sometimes up to 10% out, my own car is a prime example.. On standard size wheels and tyres, it would read 77mph but was really dong 70mph, the same was shown at all speeds, eg. 33mph was 30 and so on. This was checked by a friend using police approved equipment. When I changed tyre sizes it was all good again.... I went from 235/60/16 to 225/70/16 It reads 100,000miles on the clock, but has it really only done 90,000miles ? Quote Link to comment Share on other sites More sharing options...
al4x Posted January 16, 2016 Report Share Posted January 16, 2016 They may of course calibrate the speedo to the wheel size if it's a factory option wheel! Quote Link to comment Share on other sites More sharing options...
Glenlivet Posted January 17, 2016 Report Share Posted January 17, 2016 The transmission system is calibrated to work with the engine. Change either and it all goes t..ts up. Unless you go for an expensive remodelling of the ecu. Quote Link to comment Share on other sites More sharing options...
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