zzrpowerd-locost
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| posted on 18/10/05 at 06:37 PM |
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Making sense of GearCalc
I have been number crunching with GearCalc and getting some odd results!
I presume the speeds it comes up with are theretical speeds!
Either that or my car will top out at 212mph!
these are the figures i got
GearCalc v2.0.0.3 Copyright ©2001, Peter Ogden
Gear Ratio, Speed and RPM Calculator
Gear set: Manually entered values
Gear 1 2 3 4 5 6 Final
Ratios: 2.800 2.000 1.590 1.333 1.153 1.035 3.540
RPM Limit: 11500
RPM @Peak Power: 10500
Tyre Size: 205/60 x 13
Tyre Diameter: 22.69 in
Tyre Circumference: 71.28 in
Gear Mph per 1000 RPM Mph @10500 RPM Mph @11500 RPM
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1 6.81 72 78
2 9.53 100 110
3 11.99 126 138
4 14.30 150 165
5 16.54 174 190
6 18.42 193 212
Mph RPM (in Gears)
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1 2 3 4 5 6
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5 734 524 417 350 302 271
10 1468 1049 834 699 605 543
15 2203 1573 1251 1049 907 814
20 2937 2098 1668 1398 1209 1086
25 3671 2622 2085 1748 1512 1357
30 4405 3147 2502 2097 1814 1628
35 5139 3671 2918 2447 2116 1900
40 5874 4195 3335 2796 2419 2171
45 6608 4720 3752 3146 2721 2443
50 7342 5244 4169 3495 3023 2714
55 8076 5769 4586 3845 3326 2985
60 8810 6293 5003 4194 3628 3257
65 9545 6818 5420 4544 3930 3528
70 10279 7342 5837 4893 4233 3799
75 11013 7866 6254 5243 4535 4071
80 8391 6671 5592 4837 4342
85 8915 7088 5942 5140 4614
90 9440 7505 6292 5442 4885
95 9964 7921 6641 5744 5156
100 10488 8338 6991 6047 5428
105 11013 8755 7340 6349 5699
110 9172 7690 6651 5971
115 9589 8039 6954 6242
120 10006 8389 7256 6513
125 10423 8738 7558 6785
130 10840 9088 7861 7056
135 11257 9437 8163 7328
140 9787 8465 7599
145 10136 8768 7870
150 10486 9070 8142
155 10835 9372 8413
160 11185 9675 8684
165 9977 8956
170 10279 9227
175 10582 9499
180 10884 9770
185 11186 10041
190 11489 10313
195 10584
200 10856
205 11127
210 11398
Gear Change RPM drop (change @10500) RPM drop (change @11500)
-------------------------------------------------------------
1 -> 2 -3000 (to 7500) -3286 (to 8214)
2 -> 3 -2152 (to 8348) -2358 (to 9142)
3 -> 4 -1697 (to 8803) -1859 (to 9641)
4 -> 5 -1418 (to 9082) -1553 (to 9947)
5 -> 6 -1075 (to 9425) -1177 (to 10323)
I would expect top end to be 130mph at the most??
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ChrisGamlin
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| posted on 18/10/05 at 06:42 PM |
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You are forgetting the primary reduction ratio (the ratio between the crank RPM and the clutch/gearbox input RPM), which on most bike engines is
around 1.5:1 to 1.6:1. Unlike a car where the crank directly drives the clutch (and so gearbox), on a bike the crank has a drive gear on the end which
drives another gear on the clutch basket.
Chris
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need4speed
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| posted on 18/10/05 at 06:44 PM |
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Been beaten to it but read this thread.
Link
Dave
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zzrpowerd-locost
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| posted on 18/10/05 at 06:44 PM |
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so i divide those figures by 1.5 ?
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zzrpowerd-locost
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| posted on 18/10/05 at 07:02 PM |
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wow hoo!
the zzr primary reduction is 1.637:1
so if im right with my calculations the indicated 212mph in top divided by 1.637 comes out at 129.5mph at 11500rpm (redline) or 117.9mph at 10500rpm
(max power)
And thats with a 3.54 diff
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ChrisGamlin
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| posted on 18/10/05 at 07:07 PM |
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Roughly yep, if you want to download the spreadsheet (originally from they Yahoo BEC List) then click
here
Chris
[Edited on 18/10/05 by ChrisGamlin]
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zzrpowerd-locost
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| posted on 18/10/05 at 07:23 PM |
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1992 zzr1100 c1, full power 147ps
just downloaded that chris, ratios on there are slightly more actuate and the redline show 500rpm lower but still returns a figure of 124mph so 120ish
should be somewhere right?
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ChrisGamlin
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| posted on 18/10/05 at 07:26 PM |
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Dont take any notice of the red line, they were set at 11,000 for all engines as it was the one bit of data that was tricky to get hold of accurately,
if you know what it actually is then edit the spreadsheet to put in the correct max rpm
Chris
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zzrpowerd-locost
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| posted on 18/10/05 at 07:31 PM |
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Oh rite! I thought my engine hit 11500 when i ran it while still in the bike, so thats the 129mph top end then(approx)
Im happy with that, means i will settle for english axle at 3.54 for the moment
[Edited on 18-10-05 by zzrpowerd-locost]
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zzrpowerd-locost
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| posted on 18/10/05 at 07:37 PM |
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As a matter of interest i just ran gearcalc again with the same data but with 3.14 diff (sierra diesel)
result = 139.9mph
That is insane!!!
But i presume aceleration would suffer?
[Edited on 18-10-05 by zzrpowerd-locost]
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ChrisGamlin
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| posted on 18/10/05 at 07:45 PM |
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It would suffer a bit, but not hugely, a mate of mine has a 3.2 Freelander diff in his Megablade and that still flies, not noticably slower than mine
when it had the blade engine.
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zzrpowerd-locost
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| posted on 18/10/05 at 07:52 PM |
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3.2 diff show 137.5 mph, enuff to blow the local chavs away then
[Edited on 18-10-05 by zzrpowerd-locost]
 
Rescued attachment vonchav_icon.gif
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ChrisGamlin
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| posted on 18/10/05 at 08:20 PM |
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In all honesty as long as you are geared for 120mph plus, I really wouldnt worry about it, you'll be hard pushed to hit 130mph+ in a 7 style BEC
due to the attrocious aerodynamics anyway, so unless you're going to be doing lots of motorway driving and want a slightly mor relaxed cruise,
then there's no point in gearing any higher.
Chris
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zzrpowerd-locost
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| posted on 19/10/05 at 11:40 AM |
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so is a 3.54 english diff common or is there a more common ratio
roads and hills round here call for acelertaion over top end
Only time i will max out is on the track, anyone want to join me at cadwell!
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ChrisGamlin
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| posted on 19/10/05 at 12:13 PM |
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with an English live axle, the highest ratio you'll get is a 3.54, so obviously that makes it most suitable for a BEC. Its only if you go IRS or
de-dion that you can use the 3.38 / 3.14 Sierra diffs and further lengthen the gearing.
You won't max it out at Cadwell either though, Ive driven it a couple of times when my car was in the blade guise and I never hit the limiter in
6th when using a 3.54 
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zzrpowerd-locost
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| posted on 19/10/05 at 12:41 PM |
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wouldnt 3.89 be better for aceleration than 3.54? although gearcalc shows top end would be 113mph 
So you rekon 3.54 is a good all round diff?
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zzrpowerd-locost
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| posted on 19/10/05 at 12:43 PM |
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another thing i noticed the bit on gearcalc that so how much engine rpm drops between gear ratios doesnt change between 3.54 and 3.89???
so it cant take the final drive into count?
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kb58
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| posted on 19/10/05 at 01:52 PM |
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Aerodynamics is THE limiting issue at the top end, nothing else. Sure the math may say you can reach 140-200mph, but it isn't going to happen.
As another post said, due to the poor aerodynamics of the BEC, you may reach about 125-135, depending if you have a windscreen or not, but
that's it.
My mid-engine Mini with about 165 wheel-horsepower will never go over 130mph due entirely to aero loading.
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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zzrpowerd-locost
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| posted on 19/10/05 at 01:59 PM |
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yep! i think 120mph will be mad enuff ina open top with ya arse basically 3 inches of the ground!
Anyone got any tales of those home made gokarts u made when you was a kid?? didnt they seem fast with ya mate pushing lol
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ChrisGamlin
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| posted on 19/10/05 at 02:56 PM |
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quote:
Originally posted by zzrpowerd-locost
another thing i noticed the bit on gearcalc that so how much engine rpm drops between gear ratios doesnt change between 3.54 and 3.89???
so it cant take the final drive into count?
Regardless of what diff you have in the car, your RPM drop will always be the same between gears.
...and to answer the other question yep I think a 3.54 is a good BEC diff for most engines, but can also get a 3.7 or so which might be OK for you,
although I have had my car geared for various top speeds between 110 and 130mph and I would alweys now aim for the upper end of that so its not quite
so buzzy on dual carriageways etc, and has a bit in reserve for the very fast circuits.
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