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.

 

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

 

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

 

I shift around 5300 RPM....after that...the torque curve seems like it flattens out...

 

5300???? Do you maybe mean 6300? Max hp is about 6000rpm, shifting at 5300 is not making the most of the car!

 

After 6000, mine is just making noise...nothing left, but when I shift at 6, I end up in the next gear with a little more torque. For me, the power is between about 3800 to 6000.

 

I just ran the car and 5500 is where my powa drops off....

 

Hes right I just went out and did a few short runs. The power flatlines at about 5500. As I hit second I was at about 40mph.

 

Ah... nope.

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

 

Maybe it flattens a bit after 5500, but from 5500 to 6000, there is still more acceleration than in the next gear. I get decent pull from 4 to 6, then it drops off a lot. If we had a lot of low end torque, then there may be benefit of shifting earlier.

 

I am searching for a solution to make the car pull hard until the rev limiter, without losing low end. I don't know if a camshaft could do that, along with a custom map.

 

Cam and head work. It's all about making that thing breathe up top.

 

Got the head, just need the cam......And to add to the discussion, there is a noticeable loss due to the design of the camshaft after 6300-6500 Rpm. Man is 3rd strong though.

 

I just dont want to lose torque from the already weak low end torque, that's what i am afraid with the camshaft.

 

Then use an adjustable cam gear to get the power where you want it a little better.

 

Advanced cam timing = more low end, loss on top
Retarded cam timing = more top end, loss down low

 

a cam should increase overall torque. It doesn't just move the peak around. It should increase it all over, especially the lower and mid, without reducing high rev torque. At least a well made cam...

 

Any one on here installed a cam on their MC? Im very tempted to myself. Jan is tuning my car in October and I want to get most of my engine mods done by then.

 

agree, but the cam timing does have the effect described.

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...

 

If we had a dyno curve of a car with the Schrick camshaft it would be really helpfull to reach some conclusions!

 

particularly if said dyno data was accompanied by the installer's timing choice! without provision for adjustment, that cam appears to close the inlet valve at 64 degrees ATDC if I'm reading the right specs.

here's a better (for me anyway) tutorial on the matter...

http://www.compcams.com/technical/TimingTutorial/

 

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!

 

Good point. Every MC cam I've seen advertised (both R50 and 53) have been designed for improved power throughout the RPM band, not just a top end kinda thing.
That, and they all meet EPA and emissions standards, right? A super agressive cam won't pass 50 state legality while a mild to moderate cam should while retaining idle quality and total usable power from idle to redline. Speaking of which, does anyone have a decent quality video of a cammed Cooper? I'd be curious of the sound at idle, low RPM and high in revs.

 

That's why Im not even gonna mess with my Cooper's engine. Already have the 6-speed....and working towards Jan's stroker/turbo drag setup. What's it at...like 700HP?