jambojeef
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| posted on 31/1/05 at 06:39 PM |
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CBR 1000 Ratios
As far as i can tell there are a few of us on here using CBR 1000 engines so hopefully you can help me work a couple of things out -
My Cbr 1000 produces peak power at 10500 revs and has a 1.786:1 primary reduction. With a 3.62 rear diff and on 195,50-15 this gives a theoretical top
speed of about 105 mph.
this seems really low! Is anybody using a 3.14 rear diff from the 2.3 diesel?
Anyone got any thoughts on diff for these engines since they rev fairly low..?
Cheers
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smart51
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| posted on 31/1/05 at 07:24 PM |
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just because peak power is at 10,500 doesn't mean that this is as fast as your car will go. the engine will only have slightly less power at
11,000 and not that much less at 12,000 if it will rev that high. let's imagine that coincidentally the amount of power that your engine
generates at 12,000 RPM is enough to power your car to 120 MPH and that your top gearing is 10 MPH/1000 Revs. Your top speed will be 120 MPH.
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jambojeef
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| posted on 31/1/05 at 07:38 PM |
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yeah, I guess so - and you're right. I've done a bit more playing in gearcalc since i posted - what is everyones opinion on using the 3.14
dif and 205,50-16 wheels and tyres? Should give a 125 mph top speed but Im worried about using wheels and tyres with that size of rolling diameter!
Any thoughts?? Anyone already installed a 3.14 witha similar engine?
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Stu16v
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| posted on 31/1/05 at 07:45 PM |
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I should imagine that a 3.14 diff would be ideal. Trouble is actually finding a 3.14 diff...
Dont just build it.....make it!
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smart51
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| posted on 31/1/05 at 07:47 PM |
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big wheels = heavier wheels = slower car + more unsprung weight (ride / handling problems)
3.14 diffs are expensive and rare but if you want taller gearing are probably better than large diameter wheels.
you could always fit a 60 or 65 or 70 profile tyre to a 15" rim rather than have a low profile 16" or 17"
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jambojeef
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| posted on 31/1/05 at 08:12 PM |
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I think a 3.14 diff has to be way to go then - checkout this spreadsheet - I think I might have cracked it!!!
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zilspeed
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| posted on 31/1/05 at 09:22 PM |
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I've also had a bit of a fiddle with this spreadsheet.
Based on my Capri 1.6 axle and Yokohama A/021rs at 185/70 x13"
Here are the figures. Based on 10500 max rpm.
1st 38.04514808
2nd 50.61642827
3rd 63.52407846
4th 76.4796471
5th 89.11768077
6th 100.1188107
So - it seems I might have a bit of a sprinter on my hands once that engine goes in...
Might have to investigate 2.8i or 3.0S axles
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lukefree233
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| posted on 31/1/05 at 09:47 PM |
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Evening,
I've got a cbr1000 installed in my striker. It initially had a sierra 3.62 diff installed running on 185/60/14 and whilst the acceleration was
good the top end really struggled.
You'd hit the rev limiter about a third of the way down the pit straight at brands hatch at just over 105 and sitting almost on the red line for
a hour or so on the way back from lemans trying to keep up with the blade and r1 power cars was some what painful!
Its now got a 3.14 installed and you hardly notice the difference in acceleration and its a lot nicer having the top end there when you need it (about
120mph), ok it's still not as good top end as the other common engines but its fine for most things.
If your cars going to be a bit of all rounder i.e. road miles and track work then get the longer diff it will make a lot of difference if its just for
sprints etc then it may not be as useful, I’d say it was the best upgrade I’ve done to my car since I got it.
Also unless you've modded the engine peak power is not 10500rpm, that’s the rev limiter. In mine you can feel the power fall away after about
9250 it'll still pulls just not as quickly.
It is a good engine for the money, and very strong. Mines done three very hard trips to Le-mans, a far bit of track work and gets used all the time on
the road and so far hasn't missed a beat. It’s even survived dropping it's entire contents of oil on the off ramp of the Newhaven-dieppe
ferry last year on the way to le-mans after I ripped a big chunk out of the sump!
I've attached the gear calc that I use, it's a bit easier to muck around with the tyre and diff ratios.
Luke
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ChrisGamlin
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| posted on 31/1/05 at 10:26 PM |
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Hi Luke, good to see you 
I posted some pics of your car on here earlier for someone who was looking at CBR1000 engine positioning, although it looks like Simon was taking the
pictures through the bottom of a pint glass as they are a bit blurry so maybe you've got a few better ones?
cheers
Chris (from Le Mans last year with a 3.89 in at the time which was equally painful  )
[Edited on 31/1/05 by ChrisGamlin]
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tks
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| posted on 31/1/05 at 10:28 PM |
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WTF
what means the primary??
i thought we haddend a "extra gear"???
what a bad surprise....
what whould be the primary of a VFR 800.??
the bike's max speed = 245Km/h....
i think i wil need also a 3.14 diff..
and i wanted a 210Km/h car..
TKS
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ChrisGamlin
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| posted on 31/1/05 at 10:32 PM |
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Primary reduction is the ratio between the crank and the clutch (the crank has a gear on it, and so does the outer clutch basket). Obviously a car
engine isnt the same as the clutch is mounted directly on the end of the crank.
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jambojeef
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| posted on 31/1/05 at 11:07 PM |
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Cheers Luke! Cheers chris!
Im looking at all the kinda trips you guys do - i.e Lemons once a year, bit of all round stuff, trips to the ring occasionally and so need the old
girl to have slightly longer legs. I think I'll be going down the 195/50/15 - 3.14 - route, should be good for around 125 mph top speed and I
guessing CBR 1000s actually sprint slightly better than R1s etc owing to the slightly shorter lower ratios in 1st, 2nd and 3rd? Although I bought the
chassis and engine as an ufinished proect - Im coming round the idea of it being a really good choice for the kind of car I want - have you Chris or
Luke taken your cars around the 'ring? Be interested to see how they coped after my diasterous visit the other year!
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ChrisGamlin
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| posted on 31/1/05 at 11:12 PM |
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Ive not done the ring no, furthest afield Ive been in mine is round Spa which is an awe inspiring track. Im not sure I fancy the ring too much to be
honest, not on a public day anyway, too many things going too many different speeds and 90% of them (including me) not knowing where the hell the next
corner was!
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jambojeef
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| posted on 31/1/05 at 11:15 PM |
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You've obviously got the right idea of the place! Spa is on the list of places to visit this summer actually - sounds pretty cool! are you
running a 3.14 now then?
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lukefree233
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| posted on 31/1/05 at 11:21 PM |
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Hi Chris,
Hows the engine swap going?
Got quite a few photos if anyone needs them of the engine postion and mounts etc and it's no probs getting any images of anything in particular.
jambojeef: Nope never been to the ring in it, I know chris has done Spa and lots of other trackdays but his car has/had a blade lump in. If I
get my arse in gear I may try a bit of sprinting in it this year and it should do ok. I think i'm the weak link in getting the most out of the
car at present!
My car can just about keep up with the R1s up to about 95 then they really start to show there legs but for an engine that cost peanuts I can't
complain!
Luke
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ChrisGamlin
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| posted on 31/1/05 at 11:23 PM |
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Nope, a 3.54, Ive got a live rear axle so thats the highest I can get. The blade is higher geared than the CBR1000 though so with that diff and
185/60-13" I get around 122mph top end which is fine.
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ChrisGamlin
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| posted on 31/1/05 at 11:25 PM |
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Hi Luke
Hopefully sold the blade engine package today so it should be full steam ahead - best get my arse in gear I think.
Chris
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