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bobbber
P4
Joined: 14 May 2003
Posts: 2162
Location: The Greatest Town on Earth - Swadlincote, UK
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 Posted: Tue Feb 26, 2008 4:45 pm Post subject: |
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And it's 132mph for a Series III (at least for the cat'd version)?
5650 @ 117 = ratio of 48.29
6750 @ 132 = ratio of 50
Therefore, 96.58% (48.29*2). OR a difference of 3.42%.
I don't think anyone would notice this difference (at least not with the dodgey combination of inaccurate speedo and rev counter)
9/35 = 0.257
10/37 = 0.2703
Difference... 4%
My mathematical genius - clearly wasted on you people! 
Bob
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Admin
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Joined: 19 Feb 2003
Posts: 1223
Location: Stafford, UK
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| Posted: Thu Feb 28, 2008 12:30 pm Post subject: |
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| paulhide wrote: |
What I'm trying to say is that top speed for an S2 1.7 limited to 5650 revs is 117 mph and top speed for a 16v limited to 6750 revs is 135 mph and these gearbox ratios work out at pretty damn similar   |
What do you mean by limited? The stock S2 1.7 had a rev limited on the rotor arm set to 6750rpm from memory (and when desperate and using an XR3i rotor arm with a limiter at 6250 or so I kept hitting the rev limiter  ).
All the best
Keith
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paulhide
P4
Joined: 20 Dec 2003
Posts: 1607
Location: Oh Beautiful Billingham
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| Posted: Thu Feb 28, 2008 3:54 pm Post subject: |
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Oops! On my dials 6750 for 16v and 6250 for S2 1.7. I guess that definately makes the S2 box shorter.
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Eddie_W
Alfasud
Joined: 08 Aug 2007
Posts: 74
Location: New Zealand
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| Posted: Thu Feb 28, 2008 11:50 pm Post subject: |
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Bobber rules! But now my head hurts. So a 3.7 diff for the S2 and a 3.9 for the S3, Alfa must have lowered it so the 16v could keep up with the 8v off the line. HeHe
Regards Eddie
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RBL
Alfa Sprint
Joined: 30 Mar 2003
Posts: 162
Location: Leicestershire
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| Posted: Fri Feb 29, 2008 12:01 pm Post subject: |
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Can you tell the difference between the s2 and S3 'boxes by looking? Not sure which I have.
Knighty, on my Spyder (1.7 8v/ 5 speed), 70mph is 3500 rpm and 80mph is just under 4000rpm. However, I'm running 15" wheels with 195/60 15 tyres - so I would have thought the revs would be lower for any given speed?!
(My gauges are Porsche 912 with the speedo running off the front wheel - so the speed is showing correct, as is the tacho)
I would have thought that at 70mph, my revs would be lower than 3500 due to the larger diameter wheels?!
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baiones
Alfa Sprint
Joined: 08 Apr 2003
Posts: 130
Location: Portugal
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| Posted: Fri Feb 29, 2008 4:32 pm Post subject: |
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| paulhide wrote: |
| Oops! On my dials 6750 for 16v and 6250 for S2 1.7. I guess that definately makes the S2 box shorter. |
Here in Portugal the S2 1.7 QV box is longer than the 16v one .
I've tested both boxs on a 16v .
And by checking the gear values and diff ratio, i got to the same conclusion...
Are you sure your S2 has the original gear box ?
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Baiones
ALFA ROMEO 33 1.5 QV
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Admin
Site Admin
Joined: 19 Feb 2003
Posts: 1223
Location: Stafford, UK
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| Posted: Fri Feb 29, 2008 7:52 pm Post subject: |
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| RBL wrote: |
| Can you tell the difference between the s2 and S3 'boxes by looking? Not sure which I have. |
Probably have to lock on output shaft from the gearbox and turn the input shaft and count the turns of the output shaft. Work it out from that. Be fiddly though. Or take the gearbox sump off and count the teeth on the diff.
| RBL wrote: |
| Knighty, on my Spyder (1.7 8v/ 5 speed), 70mph is 3500 rpm and 80mph is just under 4000rpm. However, I'm running 15" wheels with 195/60 15 tyres - so I would have thought the revs would be lower for any given speed?! |
Those wheels / tyres would make the gearing about 6.4% higher. Almost double the difference between the S2 and S3 gearboxes.
| RBL wrote: |
| I would have thought that at 70mph, my revs would be lower than 3500 due to the larger diameter wheels?! |
Working it out.
At 70mph your wheels are turning 967 times a minute. With a S2 gearbox having a 10/37 diff that would make it 3577.99 rpm to the diff. With a 1:0.854 top gear that would make the engine be turning at 3055rpm.
With a S3 1.7 gearbox it would work out at 3211rpm.
With a S3 1.3 gearbox it would work out at 3395rpm.
All the best
Keith
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paulhide
P4
Joined: 20 Dec 2003
Posts: 1607
Location: Oh Beautiful Billingham
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| Posted: Sat Mar 01, 2008 10:55 am Post subject: |
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Hi RBL, yes you can tell the difference between the S2 and S3 boxes - the S3 boxes have a nick in the housing on one side where it faces the engine, for the flywheel sensor.
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RBL
Alfa Sprint
Joined: 30 Mar 2003
Posts: 162
Location: Leicestershire
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| Posted: Wed Mar 05, 2008 5:48 pm Post subject: |
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Paul and Keith, thanks for the feedback. It does have the gap for the sensor so it must be a series 3. (The engine came from a Sprint with an S2 'box but when I took off the 'box sump plate, loads of small metal teeth dropped out! - so I got this box as a replacement)
It must be a 1.3 box from the rpm readings - I'm sure it shows 3500rpm (or very close) at 70mph. (The guy that sold it to me said it was a 1.7 box, but there you go). The problem with larger diameter wheels is that you lose acceleration, so I suppose having a 1.3 'box with these wheels is a bonus unless I wanted really low cruising rpm.
Helpful stuff - thanks
Rich
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Admin
Site Admin
Joined: 19 Feb 2003
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| Posted: Thu Mar 06, 2008 11:49 am Post subject: |
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Hi
S3 1.3 boxes are pretty rare in the UK as they were not officially imported (they were sold in Ireland though).
All the best
Keith
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RBL
Alfa Sprint
Joined: 30 Mar 2003
Posts: 162
Location: Leicestershire
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| Posted: Fri Mar 07, 2008 11:52 am Post subject: |
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| Quote: |
| S3 1.3 boxes are pretty rare in the UK as they were not officially imported (they were sold in Ireland though). |
Hmmmm. Now I'm confused. I'll have to have a closer look.
Thanks for your help.
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