w4lrus
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| posted on 2/2/12 at 08:51 AM |
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R1 Striker Top Speed
Morning all,
I am currently on the hunt for a diff for my R1 Striker build, and with the tyre size that I will be using (195x50x15), the theoretical top
speed with a 3:38 diff is 130. With a 3:62 diff it will be 120.
As I am sure you know:
3:38=Expensive, harder to find
3:62=Cheaper, easier to find
Does anybody know the aerodynamic limited top speed of a striker with 150ish bhp? I don't want to lash out for a 3:38 when a 3:62 is fine, but
nor do I want to be banging off the limiter all the way along longer straights on trackdays.
Another option is to use 205 tyres, which would give me another 5mph (ish) I believe....
Your thoughts and help are much appreciated
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progers
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| posted on 2/2/12 at 08:58 AM |
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You will easily be able to go > 130mph with a long enough straight. Plump for the 3.38, its the better option, especially if you plan to do any
trackdays.
- Paul
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afj
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| posted on 2/2/12 at 09:00 AM |
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What year R1? my 2003 R1 in an mk with that size tyre will hit the limiter in 6th 132mph thats with a 3.62lsd
eerrrrrrrrrrrrrrrr
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progers
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| posted on 2/2/12 at 09:27 AM |
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Your speedo might have said that but if you do the calculations a 2003 R1 with 195/50/15 tyres, 3.62 diff and a rev limit of 11,750 will max out at
approx 122mph. So your speedo is optimistic or you had a different diff in your car!
Cheers
Paul
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w4lrus
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| posted on 2/2/12 at 09:27 AM |
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It's a 5VY, 2005
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adithorp
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| posted on 2/2/12 at 10:16 AM |
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quote:
Originally posted by w4lrus
It's a 5VY, 2005
5vy has a higher final drive ratio than the ealier ones and a 13750 rev limit. Is that what you used in you calcs?
I've got 3.21 freelander diff and 205/60/13 on mine and it hits 70 in first and 150in top. It's a bit overgeared on ocation but that is an
advantage at times as well. With a Striker idea would be the 3.38 but I'd put the 3.62 in with 205's and see how it is. You can always
upgrade later to the 3.38.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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MK9R
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| posted on 2/2/12 at 10:20 AM |
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Go for the freelander, cheaper and liter than a 3.38.
Cheers Austen
RGB car number 9
www.austengreenway.co.uk
www.automatedtechnologygroup.co.uk
www.trackace.co.uk
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w4lrus
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| posted on 2/2/12 at 10:31 AM |
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quote:
Originally posted by adithorp
quote:
Originally posted by w4lrus
It's a 5VY, 2005
5vy has a higher final drive ratio than the ealier ones and a 13750 rev limit. Is that what you used in you calcs?
I've got 3.21 freelander diff and 205/60/13 on mine and it hits 70 in first and 150in top. It's a bit overgeared on ocation but that is an
advantage at times as well. With a Striker idea would be the 3.38 but I'd put the 3.62 in with 205's and see how it is. You can always
upgrade later to the 3.38.
I used a final drive ratio of 1.512, and a max revs of 12500....
How much re-engineering of the chassis is required to put in the freelancer diff?
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afj
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| posted on 2/2/12 at 11:17 AM |
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quote:
Originally posted by progers
Your speedo might have said that but if you do the calculations a 2003 R1 with 195/50/15 tyres, 3.62 diff and a rev limit of 11,750 will max out at
approx 122mph. So your speedo is optimistic or you had a different diff in your car!
Cheers
Paul
redline is 11750 my limiter cuts in at 12750 and the mk will hit the limiter drop a couple rpm and hit the limiter again that speed is on my tom
tom
eerrrrrrrrrrrrrrrr
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w4lrus
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| posted on 2/2/12 at 02:22 PM |
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Ok, so let me change my question slightly:
If I go for a 3:2 diff, what noticeable difference will this make to my acceleration over the 3:38 and the 3:62? 0-60 I am not so worried about, more
30-80. Are we talking 1 sec, 5 secs, etc
I have no real world experience of this as this is my first build.
Again, thanks
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kjouk
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| posted on 3/2/12 at 10:22 AM |
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The ratios don't have a massive impact, few tenths or so over the range you are looking at, but of course that mounts up over a lap. It's
fairly common practice on sprints/hillclimbs to vary gearing for each venue to pick up these tenths.
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JimSpencer
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| posted on 3/2/12 at 12:49 PM |
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Hi
Odd that last post know very few people who change their back axle ratio on 'locaterfields' between events, and even less that change
gearbox ratio's, but you live and learn I suppose.
Back to the OP's question.
My striker is geared to do 127mph at 8700 in top, that's with around 175bhp CEC, it won't pull it on any circuit we go to - with a screen
fitted and I suspect would only just, if at all, get their without - there's some very interesting testing been done on top speed of a striker
with and without a screen..
Highest we see is about 120, but it's very busy indeed to drive geared like that on the road (not that it does much), if the car's going
to see any road use what-so-ever then gear it a bit long to gain a bit more flexability would be my thoughts on it, the in gear perfromance will make
naff all difference, it will just move your gear change points around the speed range a bit.
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adithorp
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| posted on 3/2/12 at 01:30 PM |
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To fit a freelander diff you'd have to make up new mounting points but as it's physically smaller than the Sierra one it should fit easily
within the diff carrier. You'd then need hybrid shafts as the CV joints are different and the prop flange is different as well (I think).
On my 06R1 with 3.21:1diff, theoretical top speed is just shy of 150 and I've been past 140 and still accelerating. The Fury has an aero
advantage and doubt a Striker would achieve that.
I never get into top on most track days though (might at SilverstoneGP but not been). On the motorway it does help bring down the cruising revs, so
70mph is just under 7000rpm (R1 dash over-reads on rpm).
1st gear is high with 70mph just before the limiter.this has plus and minus points. On the good side it's nice to pull all the way to NSL before
changing gear while the numpty alonside you goes through all his gears. In the mountains I can sty in first between hairpins a lot of the time so
avoid changing up and then down (through neutral) makes life a lot easier; Hobbsy on here can vouch for the difference. Down side is getting away from
a standstill quick, is harder; Austins car is RGB raced so clutch dumps are more usual than they are on a road car. On a track day second is high so
you need to use first on a tight circuitand I often find the car overgeared.
I've seen some reports of people wh've done tests with high/low ratio's and thier 1/4mile times are alost identical due to the fewer
up changes. Add in fewer down changes and it leaves you a lot less busy when going hard.
Overall I wouldn't swap mine given the mix of touring, bimbleing and track days that I do
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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kjouk
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| posted on 3/2/12 at 01:37 PM |
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Agree not so common with locaterfields, but I know a few who do/did, removable rear bodywork is a help for diff changing. Obviously much easier to
play with tyre choices although maybe not any cheaper.
My R1 is geared about the same, 125-ish but using 3.38 although on lower profile crossply, thought about putting back to 3.62 to gain a bit but never
did, just not important enough to mess with.
The comfort factor of less frequent changes is a good point, I have a busa at the other end of that, needs 5 changes in 6 seconds which not that
pleasant to drive even on trackdays unless there is nothing at all in front.
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INDY BIRD
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| posted on 3/2/12 at 02:03 PM |
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I remember changing my blackbird Indy from a 362 to a 338 seem to take the edge of th performance and would not top out it's top speed in a 338
ratio of 135 would still only do around 120 in 5 th but changing into sixth it just didn't have h power to pull it further so I wished I'd
kept th 362 in especially on track seem to pick up better imop thanks good luck
Sean
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bobinspain
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| posted on 3/2/12 at 03:00 PM |
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The comfort factor of less frequent changes is a good point, I have a busa at the other end of that, needs 5 changes in 6 seconds which not that
pleasant to drive even on trackdays unless there is nothing at all in front.
Is that with or without Flatshifter? (Pro or Expert).
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kjouk
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| posted on 3/2/12 at 09:11 PM |
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quote:
Originally posted by bobinspain
Is that with or without Flatshifter? (Pro or Expert).
Gear sensor connected to a DTA ECU. A good shift flatlines the acceleration for normally 0.2sec with paddles, a stick shift with clutch is more like
0.4-0.5 secs for me according to data logs.
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bobinspain
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| posted on 3/2/12 at 09:27 PM |
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quote:
Originally posted by kjouk
quote:
Originally posted by bobinspain
Is that with or without Flatshifter? (Pro or Expert).
Gear sensor connected to a DTA ECU. A good shift flatlines the acceleration for normally 0.2sec with paddles, a stick shift with clutch is more like
0.4-0.5 secs for me according to data logs.
Lost me with the techie stuff, but as a beginner, 0.5 of a second appears an age (relatively speaking).
With five changes in 6 seconds, each one 'costing' a half a second, then you're not 'delivering the juice' for nearly
half the time. Or am I missing something?
The cut time of a Pro/Expert Flatshifter is milliseconds/change, fully juiced.
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kjouk
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| posted on 3/2/12 at 11:11 PM |
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quote:
Originally posted by bobinspain
Lost me with the techie stuff, but as a beginner, 0.5 of a second appears an age (relatively speaking).
With five changes in 6 seconds, each one 'costing' a half a second, then you're not 'delivering the juice' for nearly
half the time. Or am I missing something?
The cut time of a Pro/Expert Flatshifter is milliseconds/change, fully juiced.
Sorry, thread was going off topic so I was just being terse but maybe this will interest others.
I have a flatshifter feature, it's controlled by a standalone ECU that replaces the standard busa ECU. This is configured with an 80ms cut time
but in reality the log data shows that acceleration stalls for longer than this, each change is different but say 0.1-0.3 is about normal.
As you say without it things would be much slower, the car will actually start to slow down a little bit during gear changes and you could easily lose
a second on getting to top speed. But this car is an extreme example because we have plenty of bhp to overcome drag, so time between gear changes is
pretty constant, rather than slowing as you would normally expect.
If you are interested in these effects have a look at http://westboost.github.com/, the green plot shows a couple of slow changes, this is from a
couple of warmup runs of the small Curborough track.
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w4lrus
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| posted on 6/2/12 at 08:49 AM |
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Thanks for all the responses, much appreciated
I got all nerdy, and decided to crunch some numbers to see what the theoretical top speed and rates of acceleration might be.
I used the information found at the following sites:
http://vlsicad.ucsd.edu/~sharma/Potpourri/perf_est_intro.html
http://www.mayfco.com/caterham.htm
http://craig.backfire.ca/pages/autos/drag
I used the drag coefficient and frontal area of a caterham, and a torque curve from a stock R1 dyno run, and a gear change of 0.2secs, and came up
with the the following theroretical data:
Top speed: 125mph
Best diff for acceleration: 3.38.
There was not a lot between running a 3.62,3.38, and 3.2 in terms of acceleration, although running 205s was far more detrimental.
Given all of your feedback, I think I will hold out for a 3.38, but may nab a 3.62 if an LSD one comes up, as then I could use that, and then combine
with a 3.38 when I manage to find one!
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