Socksipper
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| posted on 4/4/07 at 10:30 PM |
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Diff advice?
Hi there, new in here, but looking forward to building a 'book' Locost with bike engine power.
My main question is, is the Sierra lsd diff ok for use with a bike engine, or should I be looking at something else, like a Freelander (as Fisher
seems to prefer these)?
Any suggestions welcome (before I buy the wrong bits!)
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zxrlocost
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| posted on 4/4/07 at 10:40 PM |
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hi sierra 3.62 lsd from a xr4x4 is the most common one to use it has about the right ratio for most bike engines and is reasonably cheap.
furys and westfields use land rover diffs which apart from being 5 x the price the only advantage I can think of is there lighter by 6kg dont know
much about the ratios
but the xr4x4 one will be fine with bolt on shafts and caliper disc rear end
if you get a normal sierra diff it may have a different ratio it will be push in shafts and drum brakes
hope that helps
chris
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Socksipper
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| posted on 4/4/07 at 10:47 PM |
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Hi Chris, thanks for that.
As I will be sprinting/hill-climbing this car, any advice on engine choice? I'm baffled by the amount of different Fireblades there are, but
don't fancy the expense of a Busa.
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zxrlocost
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| posted on 4/4/07 at 11:04 PM |
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if its your first go at something like this
bang for buck would be a carb R1 or 893 -919 carb fireblade or another great one is the zx9r engine
the above engines need minimal if any mods to run safely day in day out in a kit car and will out accelerate basically any car on the road
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Guinness
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| posted on 5/4/07 at 06:51 AM |
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If you are going to be sprinting the car, gear ratios are going to be crucial.
Have a look for any post by Chris Gamlin on here. At the bottom of his posts is a link to an excell spreadsheet that allows you to put in variables
for diff, tyre size, bike engine etc, and will give you max speed in each gear.
For example my ZZR1100 / 3.62 diff gives a Vmax of 124mph in 6th at 11500 rpm (running 185/60/14 tyres). Great for motorways where 6200 rpm sees 70
mph on the clocks, but probably not great for sprinting.
Using the same diff / tyres but a CBR1000 gives a Vmax in 6th of 107mph and 70 mph on a motorway is going to be 7200 rpm.
Hope that helps.
Mike
P.S. I know they aren't built for cruising on motorways but you can see how important matching the diff to the engine is.
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smart51
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| posted on 5/4/07 at 07:13 AM |
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I have a 3.62 LSD with my carbed R1 and it's just fine on the road. Peak power happens at 105 MPH and the top speed is limited by revs not
power.
For sprinting, a 3.92 diff might be better. These are also available as LSDs. They would limit the top speed by even more (111 MPH with 195/50/15)
but you'll get proportionally more acceleration in each gear.
3.38 or 3.14 diffs give more top speed, but less in gear acceleration.
It depends what you want. If that crucial 0-40 sprint in 1st or 30 - 60 in 2nd is what you want, then a higher numbered diff might be better.
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worX
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| posted on 5/4/07 at 08:13 AM |
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Your Engine choice, Diff choice and wheel/tyre size choice will all have to be decided together for you to best work out which one of each you will
choose...
for instance if I were you I would start out by saying that you'd want to be running 13" wheels for two reasons, less weight and chance of
part worn slicks for competition use. (mine are 15" but mostly for road use)
from there you can work out what engine you would want based on your wallet - I have built a car using relatively expensive brake and suspension
components to get my weight down, but then plumped for a less powerful engine because thats what I could afford - I can always upgrade my engine
later. (mine is a 919 Blade RRT - Ebay)
and then from there you will choose your diff - and like Guinness said look for Chris Gamlin's posts which contain his diff ratio calculator
thing and you should then be sorted! (mine is NON LSD 3.62)
Also don't discount NON LSD diff's they weigh 10 kilos less if you include driveshafts into that equasion...
hth
cheers,
Steve
[Edited on 5/4/07 by worX]
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mike smith1
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| posted on 5/4/07 at 09:34 AM |
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There is a big debate about LSD or Non LSD, having spoken to people who have had a couple of cars with lsd's and done track days and road use,
they have said that they would not use a lsd in there next car as they feel they are easier to drive with non lsd, however others have said that they
would always go LSD.
I have a non LSD in mine and not having tracked the car or driven it on the road yet i cannot comment, but the people i am talking about are members
on here and i'm sure they will be along shortly to comment.
Its really each to there own, I must admit though i have bought a second donor as it was cheap and it does have a LSD so i have the option!
Mike
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dilley
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| posted on 5/4/07 at 10:37 AM |
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I tried lsd and non lsd when I did my turbo conversion, the ford lsd is crap with my engine now so I ditched the lsd and I can drive it loads better,
as I have said before a quaiffe lsd is probably a different kettle of fish!!
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jimgiblett
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| posted on 5/4/07 at 10:51 AM |
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Non LSD cars tend to be a lot easier to drive as when they loose traction they effectively kill the power bringing things back in shape. On the limit
lift of oversteer caused by this cutting of power can snap you into a spin.
LSD cars have the downside of push understeer and respect is needed when loosing traction as it is both wheels that are spinning. Driving on the
throttle is so much easier though (even with the Ford LSD).
- Jim
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chockymonster
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| posted on 5/4/07 at 11:23 AM |
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quote:
Originally posted by dilley
I tried lsd and non lsd when I did my turbo conversion, the ford lsd is crap!!
Sorry, just had to fix that line for you!
PLEASE NOTE - Responses on Forum Threads may contain Sarcasm and may not be suitable for the hard of Thinking.
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dilley
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| posted on 5/4/07 at 11:32 AM |
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TimC
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| posted on 5/4/07 at 04:33 PM |
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quote:
Originally posted by jimgiblett
Non LSD cars tend to be a lot easier to drive as when they loose traction they effectively kill the power bringing things back in shape. On the limit
lift of oversteer caused by this cutting of power can snap you into a spin.
LSD cars have the downside of push understeer and respect is needed when loosing traction as it is both wheels that are spinning. Driving on the
throttle is so much easier though (even with the Ford LSD).
- Jim
My thoughts exactly! Another point if you're hillclimbing is check the rules for the series that you want to run in. Things like windscreens
and being road registered can make a big differerence to the class that you run in.
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Socksipper
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| posted on 5/4/07 at 07:06 PM |
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Bloody hell! Thanks for all the input and advice guys, I definitely know where to come for answers in future!
Something tells me the lsd/non lsd debate will run and run though. I currently sprint/hill-climb/trackday a Golf VR6, which runs a plate lsd, and
after sprinting various other fast Golfs without one, I wouldn't do without one again! The grip levels are awesome, and I even out-cornered an
STi Imprezza (with 330 bhp to my lowly 190 bhp) at a Croft trackday last year. Talking to the owner in the paddock afterwards, he was amazed that he
'couldn't touch you in the corners'.
But that's front wheel drive though, and I think I'm going to have fun learning to drive this bec locost-thingy I'm about to embark
on!
Once again, CHEERS!
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G.Man
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| posted on 6/4/07 at 05:47 AM |
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The ford LSD is fine for catching the back end under power and powersliding..
But it does add a lot of weight.. especially the 7.5 cossie version! which also has very heavy drive shafts..
Non-LSD cars will spin up an inside wheel on the limit and stop the back end kicking out.. LSD cars will get more power down and if the back end kicks
out you can "drift" and powerslide the car if you have reasonable car control, however that is higher risk car control...
Opinions are like backsides..
Everyone has one, nobody wants to hear it and only other peoples stink!
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