andygtt
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| posted on 22/10/05 at 09:59 AM |
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I'm not sure the answer myself..... I'm using an R1 engine with 215/40/17s and have a few diffs that I could install.
1 is out of Mr masons R1 indy with LSD.
2 is an open diff with no LSD.
3 is a big rwd cossie diff.
I'm favouring the open diff initially as whilst I'm used to this kind of car and much prefer an LSD, however the wife will be driving this
also and she's not.... so the safer handling with the open diff may be a good break in for her.
The open diff also saves in excess of 10kgs over the LSD one and the cossie is heavier still.
Do you have to strip the diff to find out the ratio?
[Edited on 22/10/05 by andygtt]
Andy
please redefine your limits.
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G.Man
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| posted on 22/10/05 at 05:41 PM |
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Ran some calcs on my ZX12R powered car and got the following...
205/50x15 tyres so (102.5mm/25.4)x2 + 15 = 4.035 then multiply by 2 and add 15 inches for the wheel... 23.07 inches diameter... x 3.142 = 72.5 rolling
circumference...
12,000 rpm rev limit /1.596 primary ratio / 1.033 secondary ratio in top / 3.62 diff ratio = 2011 revolutions of wheels at full speed...
2011 x 72.5 = 145797.5 inches per minute / 63,360 inches per mile x 60 minutes in an hour for max speed...
138mph theoretical
Opinions are like backsides..
Everyone has one, nobody wants to hear it and only other peoples stink!
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billy
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| posted on 22/10/05 at 06:26 PM |
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Well that seems quick enuff for me looks like ill take out me 3.38 and put me 3.6 in. think i may go back to no lsd,having now tried both now,
having lsd dont make a quicker car. and yeh the weight saving meens i can eat a few more pies
luego-lo-cost finished,vauxhall 16v 2.0,twin 45s de-dion rear set up
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kb58
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| posted on 22/10/05 at 07:14 PM |
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You guys should really use manufacturer's specs for tire size. The OD of the actual tire will always be a bit different then doing the math.
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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Hellfire
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| posted on 22/10/05 at 07:37 PM |
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Or just take our Dyno figures as being somewhere near. 129.7mph with 3.62 diff and 195x55x15's 
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G.Man
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| posted on 22/10/05 at 10:42 PM |
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quote:
Originally posted by Hellfire
Or just take our Dyno figures as being somewhere near. 129.7mph with 3.62 diff and 195x55x15's
works for me...
and yes an lsd wont make you faster in a straight line..
it may make you push on in a corner, but it will make the back end well driftable in the bends..
[Edited on 23/10/05 by G.Man]
Opinions are like backsides..
Everyone has one, nobody wants to hear it and only other peoples stink!
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ChrisGamlin
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| posted on 23/10/05 at 10:45 AM |
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As originally put before it was edited.......quote:
and yes an lsd wont make you faster..
Bit of a sweeping statement that aint it, that an LSD won't make you faster?
In most cases an LSD will make the car faster because it gives you more grip coming out of corners and allows you to use full throttle earlier,
although obviously it does depend on the setup of the car and the ability to get the right diff / setup so as not to compromise turn in, and also
depends on the type of driving you are doing, on the road it will make sod all difference in 99% of situations, and the other 1% you probably shouldnt
be in those situations on the road anyway
On track though, it can make a huge difference to the car's lap time, without an LSD my live axle'd car used to spin up the inside wheel
on the exit of corners all the time, eating the tyre and allowing anything with decent grip to pull several car lengths on me going onto the straight.
Chris
[Edited on 23/10/05 by ChrisGamlin]
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G.Man
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| posted on 23/10/05 at 01:47 PM |
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quote:
Originally posted by ChrisGamlin
Bit of a sweeping statement that aint it, that an LSD won't make you faster?
In most cases an LSD will make the car faster because it gives you more grip coming out of corners and allows you to use full throttle earlier,
although obviously it does depend on the setup of the car and the ability to get the right diff / setup so as not to compromise turn in, and also
depends on the type of driving you are doing, on the road it will make sod all difference in 99% of situations, and the other 1% you probably shouldnt
be in those situations on the road anyway
On track though, it can make a huge difference to the car's lap time, without an LSD my live axle'd car used to spin up the inside wheel
on the exit of corners all the time, eating the tyre and allowing anything with decent grip to pull several car lengths on me going onto the straight.
Chris
I meant top speed, which was what we were talkin about, and you knew that..
I have a cossie 7.5 inch LSD on mine, a bit heavy yes, but it will help stop spinning up one rear wheel on accleration runs and out of the
corners..
[Edited on 23/10/05 by G.Man]
Opinions are like backsides..
Everyone has one, nobody wants to hear it and only other peoples stink!
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ChrisGamlin
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| posted on 23/10/05 at 02:10 PM |
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Errr........
quote:
and yes an lsd wont make you faster..
it may make you push on in a corner, but it will make the back end well driftable..
Dont get much of that happening on the straights
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G.Man
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| posted on 23/10/05 at 02:31 PM |
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oh fgs
sometimes I wonder about IQ's
I'll edit it to make it clearer for the numpties who couldnt understand...
[Edited on 23/10/05 by G.Man]
Opinions are like backsides..
Everyone has one, nobody wants to hear it and only other peoples stink!
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ChrisGamlin
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| posted on 23/10/05 at 02:35 PM |
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Likewise!!!
Read it out of the context you seem too have meant it. When saying "it wont make you faster"the logical conclusion to come to is that you
mean round a track / down a bendy road, its so bloomin obvious that it wont make a jot of difference to top speed so why would anyone think thats what
you meant??
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G.Man
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| posted on 23/10/05 at 02:37 PM |
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Chris
If you are going to be pedantic, then I will add that the extra weight will make you slower...
Opinions are like backsides..
Everyone has one, nobody wants to hear it and only other peoples stink!
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ChrisGamlin
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| posted on 23/10/05 at 02:45 PM |
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Im not being perdantic at all, you seem to write stuff which could be misleading (presumably unintentionally), but get upset when people question what
you say.
Anyone with an ounce of mechanical knowledge will know that the only thing that is going to affect top speed is the actual gear ratio of the diff
itself, whether its an LSD or not has absolutely no bearing on that. Your post made the statement about an LSD not making you quicker then listed a
reason why (because it pushes you on in the corners), so the logical conclusion is that you're talking about an LSD not making you
quicker through corners!! 
[Edited on 23/10/05 by ChrisGamlin]
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G.Man
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| posted on 23/10/05 at 02:49 PM |
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quote:
Originally posted by billy
W having lsd dont make a quicker car.
That was what I was agreeing with...
The car will not be QUICKER/FASTER whichever way you want to put it... It MAY mean that you can put power down better on the track coming out of a
corner if you can control the back end.. I was merely, in anew paragraph pointing out another effect of an LSD
If you read the thread rather than look for posts to pick holes in maybe you would understand better...
[Edited on 23/10/05 by G.Man]
Opinions are like backsides..
Everyone has one, nobody wants to hear it and only other peoples stink!
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ChrisGamlin
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| posted on 23/10/05 at 03:07 PM |
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LOL!!! 
I may be wrong but in exactly the same way, I think most will assume that billy was talking about his overall experience with an LSD, that he found
that it didnt make his car faster overall, which may well be true for his particular setup / driving style etc, Im not arguing that.
However, I really fail to see the logic of your penultimate comment, if you can put the power down better, the car WILL BE QUICKER, it will get from
point A to point B in a faster time than it would without the LSD, so by definition its QUICKER!!!!!
Its not just control of the back end that it gives you, its outright grip. If one wheel is spinning with an open diff you are not accelerating as the
wheel not spinning is not receiving drive. With an LSD this doesnt happen, the (usually outside) wheel that isnt trying to spin still receives a
portion of drive whatever the inside wheel is trying to do, so you're always gettign drive and accelerating.
To borrow a GIF from the WSCC site
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G.Man
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| posted on 23/10/05 at 03:18 PM |
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Jeez
:patronise mode off:
I don't need a lesson in how an LSD works and the benefits...
With an LSD both wheels can spin up, so they are NOT always driving... Extra weight means the car may be slower in a straight line... all sorts of
other factors come into account...
Potentially the car may be quicker on a lap... thats as far as it goes... there is no WILL about it...
Opinions are like backsides..
Everyone has one, nobody wants to hear it and only other peoples stink!
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ChrisGamlin
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| posted on 23/10/05 at 03:58 PM |
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I should have known that with an avatar like yours, you could NEVER EVER be wrong about anything
Hands up, I did say the wheels were always driving and the car always accelerating, which although technically accurate (unless the tyres have zero
coefficient of friction when spinning), I can see what you are saying. What I meant to highlight was that both wheels are ALWAYS receiving drive,
unlike an open diff that does give virtually zero traction in certain circumstances, with one wheel spinning with no weight on it, and the other
freewheeling. As Im sure you know, if an LSD is working, you need to overcome the grip of both tyres before they will spin up, and because the sum of
weight on the tyres will always be significant (ie one tyre might be lightly loaded but the other will be heavily loaded), there will always be an
element of significant forward traction even if its reduced due to both wheels spinning, and the occasions when spinning will occur will be far less
compared to an open diff and an unloaded inside wheel, so less occasions where you lose effective drive.
Apart from that, nowhere did I claim that in all circumstances an LSD WILL be quicker though, and in a previous post actually said that in certain
circumstances it wouldnt.
[Edited on 23/10/05 by ChrisGamlin]
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G.Man
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| posted on 23/10/05 at 05:33 PM |
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Don't know what you mean about my avatar, but whatever....
There is absolutely no point in arguing over your misinterpretation of what I wrote...
Technically you are correct as am I so we are just arguing with no gain...
I am just adult enough to let it drop...
Opinions are like backsides..
Everyone has one, nobody wants to hear it and only other peoples stink!
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ChrisGamlin
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| posted on 23/10/05 at 06:12 PM |
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"G Man"
If it was my misinterpretation then I apologise, but I dont apologise for questioning it because Im sure that 99% of people that read the comment drew
the same conclusion.
Up until the point where you started personal digs at me such as questioning my IQ, it was a perfectly light hearted thread, so please do not insult
me further by saying that you're the one thats "adult enough to let it drop"
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wilkingj
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| posted on 23/10/05 at 06:19 PM |
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3.38 Diff for sale
Sorry chaps... I only asked what I thought was a simple question.
40 odd postings later... I feel so guilty..I have decided to part with it. I only got it the other day.
http://www.locostbuilders.co.uk/viewthread.php?tid=33267
Anyone interested see the above link.
1. The point of a journey is not to arrive.
2. Never take life seriously. Nobody gets out alive anyway.
Best Regards
Geoff
http://www.v8viento.co.uk
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ChrisGamlin
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| posted on 23/10/05 at 06:23 PM |
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Grrrrrrrrr you ungrateful........
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billy
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| posted on 23/10/05 at 06:33 PM |
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Well i will say this.......i think the viscous lsd on the sierra diffs are shite!!! only seems to be noticable when doing dohnuts on the local
roundabouts, nice little argument by the way when i ment it didnt make it any faster i ment overall with my tame kina driving
luego-lo-cost finished,vauxhall 16v 2.0,twin 45s de-dion rear set up
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tks
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| posted on 23/10/05 at 08:44 PM |
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Chirs is right...
When judging an technical setup (an car)
you have to look at minimum laptime you can get. In the same circumstances (trackstate,driveining line etc.)
then with LSD you are faster wy? because an inside tire loses weight due to the roll effect... also the roll on an Seven is much less then on an
cossie....
Also i saw some one saying topspeed
and weight.... but those 2 haven't todo with eachother....
only acceleration does...
(99,9% of topseepd is down to power/ aire resistance==> aero dynamics)
power means engine power but also gearing offcourse.... in fact we talk about force ==> Torque!
The above comments are always meant to be from the above persons perspective.
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tks
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| posted on 26/10/05 at 08:10 PM |
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well as far as i read this post
i will have an great problem.....
i Have an BEC
with an 3,92 diff (LSD)
and i use 195/45/R15 Tyres...
i think i should be lucky to top out at 100Mph?
p.d. i don't know my primary gear ratio..in my hayness it doesn't talk about it with any word..only the rest of the gears i can find
beginning the chapter..
Tks
p.d. what i do know is the bike sprockets size and the rear tyre size.. this could be usefull, also i know its topspeed..
(245Km/h)
how much does an fireblade (900) has??
[Edited on 26/10/05 by tks]
The above comments are always meant to be from the above persons perspective.
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ChrisGamlin
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| posted on 26/10/05 at 09:27 PM |
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Its a Pan Euro engine you have isnt it?
If so a quick Google brings this up
Primary reduction 1.829
Gear ratio
1st 2.266
2nd 1.500
3rd 1.142
4th 0.916
5th 0.758
Works out at around 122mph with a 3.38 diff, or 105mph with your diff.
Why such low profile tyres though?
Edited to add, those figures assume (a total guess of) a 9,000rpm red line.
[Edited on 26/10/05 by ChrisGamlin]
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