3rd gear@6900rpm, or 4rth 5000rpm???
#1
3rd gear@6900rpm, or 4rth 5000rpm???
Those of you who have the Midlands gearboxes, what do you feel is faster? Taking the 3rd gear in 6800-6900rpm and shift to 4rth (revs going at 5300-5400rpm), or shift at 6200-6300 rpm from 3rd to 4rth gear, and go right on the torque peak on 5000rpm???? Sometimes i feel i am only losing time taking the 3rd gear from 6300-6400rpm to 6900.
#2
if you plot the torque at the flywheel, over the usable range of RPM
and then apply the gear rations for each gear to obtain torque at the the input shaft of the differential
you wind up with a thrust chart
that will answer your question
here is a thrust chart for the Cooper S with a 6 speed getrag as an example
note that there is NEVER a point prior to max RPM where the next higher gear produces more axle torque
I rather suspect the Cooper with the Midlands will turn out the same, but I do not have the torque data for that motor, nor the reduction ratios for each gear
and then apply the gear rations for each gear to obtain torque at the the input shaft of the differential
you wind up with a thrust chart
that will answer your question
here is a thrust chart for the Cooper S with a 6 speed getrag as an example
note that there is NEVER a point prior to max RPM where the next higher gear produces more axle torque
I rather suspect the Cooper with the Midlands will turn out the same, but I do not have the torque data for that motor, nor the reduction ratios for each gear
#3
The gearing of the Midland sucks, so maybe that'll give different results... The 4rth gear is very "short", while the 3rd is the opposite... And the Cooper non S doen't have much to give after 6300rpm, the torque is very low after that, while the max torque is obtained at about 4900rpm (stock car).
There are plenty of dyno charts of non S Coopers, could you caclulate it?
And here you can find the gearbox ratios : http://www.mini2.com/forum/faq.php?f...ansmission_faq
There are plenty of dyno charts of non S Coopers, could you caclulate it?
And here you can find the gearbox ratios : http://www.mini2.com/forum/faq.php?f...ansmission_faq
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#9
The gearing of the Midland sucks, so maybe that'll give different results... The 4rth gear is very "short", while the 3rd is the opposite... And the Cooper non S doen't have much to give after 6300rpm, the torque is very low after that, while the max torque is obtained at about 4900rpm (stock car).
There are plenty of dyno charts of non S Coopers, could you caclulate it?
And here you can find the gearbox ratios : http://www.mini2.com/forum/faq.php?f...ansmission_faq
There are plenty of dyno charts of non S Coopers, could you caclulate it?
And here you can find the gearbox ratios : http://www.mini2.com/forum/faq.php?f...ansmission_faq
But if you'd care to PM me an email address I'd be delighted to send you the MCS spreadsheet, which would require that you update the gear ratios, enter the torque numbers (in ft/lbs not NM), and do a bit of trimming to adjust for the five speed...
Cheers,
Charlie
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the cam designer has two primary variables to work with - overlap and lift. the installer has one - timing.
a radical cam will increase overlap, which has the effect of allowing the engine to breath better at high RPM - however such designs do extract a price at low RPM where the inertia of the intake column is insufficient to fill the cylinder effectively.
in competition applications the length of the intake runners is normally tuned so that the reflected positive pulse generated at the mouth of the intake arrives just prior to the closure of the inlet valve.
the exhaust is tuned in the opposite manner, by choosing a header length that catches the reflected negative pressure wave just prior to exhaust valve closure.
because these pressure events at the valves are affected by the speed of the gasses passing through the inlet and exhaust as well as the length and shape of the plumbing adjacent to the valves, the exact timing of the opening of both inlet and exhaust valves determines the RPM at which this effect comes into play.
in a single cam application, where overlap is fixed, the dominant effect is the inlet valve closing relative to crank angle. an earlier inlet valve closing provides increased efficiency at lower RPM where gas velocities in the intake runners are relatively low, and therefore where delaying the closure of the inlet valve could result in momentary flow reversal and detract from the mass of A/F captured in the cylinder at the start of the compression stroke.
here's a summary of the trade-offs involved. http://www.minimania.com/ArticleV.cfm?DisplayID=71
i've always been fascinated by this design problem, but have only scratched the surface, so take me with a grain of salt...
#21
here's a better (for me anyway) tutorial on the matter...
http://www.compcams.com/technical/TimingTutorial/
#22
Do you think going from a stock and very conservative cam to a more aggressive one that there would be any trade off? I don't know if any of the available cams (without custom grinding) would be aggressive enough to cause this effect in the lower rpms.
BTW, that comment on overall torque was concerning going from a stock to a (good) aftermarket cam.
Thanks for the write up!
BTW, that comment on overall torque was concerning going from a stock to a (good) aftermarket cam.
Thanks for the write up!
#23
Do you think going from a stock and very conservative cam to a more aggressive one that there would be any trade off? I don't know if any of the available cams (without custom grinding) would be aggressive enough to cause this effect in the lower rpms.
BTW, that comment on overall torque was concerning going from a stock to a (good) aftermarket cam.
Thanks for the write up!
BTW, that comment on overall torque was concerning going from a stock to a (good) aftermarket cam.
Thanks for the write up!
Ground to Mini Mania's exacting specifications by a major OEM camshaft supplier, this high performance camshaft increases horsepower and torque throughout the RPM range.
The Schrick camshafts for the Cooper and Cooper S are CNC machined from cold billet steel to improve top end power, without sacrificing idle smoothness or causing a Service Engine Soon light.
Last edited by hemiheaded18; 07-06-2008 at 07:21 PM.
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