| View previous topic :: View next topic |
| Author |
Message |
knighty
Alfasud
Joined: 12 Oct 2004
Posts: 33
Location: Essex, UK
|
 Posted: Tue Feb 19, 2008 4:39 pm Post subject: 1.7 8v rpm at 70mph???? |
 |
|
| I'm in the process of having my beetle gearbox re-built for my beach buggy which has 1.7 8v alfa boxer power, and I will be specifying a new diff ratio.......I need to know, whats the rpm of an 1.7 8v alfa-boxer when at 70mph in top gear?????......I'm hoping its about 3500rpm, as thats where max torque is |
|
| Back to top |
|
 |
bobbber
P4
Joined: 14 May 2003
Posts: 2162
Location: The Greatest Town on Earth - Swadlincote, UK
|
| Posted: Tue Feb 19, 2008 5:40 pm Post subject: |
|
|
I love these.... here goes.
Wheels are 14" diameter. That's 35.56cm.
185/60/R14 have additional tyre of 60% of 185mm = 11.1cm
That's on each side though. So, 22.2cm.
Therefore, Total tyre and wheel width combined = 57.76cm.
The circumference therefore 57.76 x pi = 181.48cm per revolution
OR 1.8148metres per revolution.
70mph is 112.9032kph. This is 112,903.2 metres per hour OR 1881.72 metres per minute.
So @ 70mph - the wheels turn at 1881.72/1.8148 which is 1036.9 revolutions per minute.
The diff ratio is 35/9. So (35/9) * 1036.9 = 4032.248
Gearing in 5th is 0.854:1. Therefore 0.854 * 4032.248 = 3444rpm
I'm afraid you're going to be about 56rpm out. 
Bob
_________________
Fiat Bravo 165 Sport |
|
| Back to top |
|
|
mt
Alfa Sprint
Joined: 19 May 2005
Posts: 177
Location: Portsmouth
|
| Posted: Tue Feb 19, 2008 6:53 pm Post subject: |
|
|
Bobbber, that post is sheer quality!  |
|
| Back to top |
|
|
BigAl
P4
Joined: 06 May 2003
Posts: 2990
Location: U.K Surrey
|
|
| Back to top |
|
|
lee16v
16 Valve
Joined: 29 Jun 2005
Posts: 1429
Location: Devon, UK
|
| Posted: Tue Feb 19, 2008 8:42 pm Post subject: |
|
|
| Bob, you da man ( but you need to get a job that takes up more of your time ) |
|
| Back to top |
|
|
johnboy
16 Valve
Joined: 26 Jun 2003
Posts: 1061
Location: margate U.K
|
| Posted: Tue Feb 19, 2008 8:55 pm Post subject: |
|
|
| lee16v wrote: |
| Bob, you da man ( but you need to get a job that takes up more of your time ) |
yep buy an alfa 
_________________
WODA WE NEED? MORE POWER!!
Alfa gt jtdm blackline
1990 S2 16v veloce sleeping!
2002 ts gtv the wifes now
1997 seadoo gsx 800
1999 freestyle superjet |
|
| Back to top |
|
|
bobbber
P4
Joined: 14 May 2003
Posts: 2162
Location: The Greatest Town on Earth - Swadlincote, UK
|
| Posted: Tue Feb 19, 2008 11:41 pm Post subject: |
|
|
See? Nothing wrong with a state education!
Then again - I was one of the last before they made exam results meaningless. A* indeed.
By the way... the diff ratio is for the later Series III boxes... some earlier boxes had a different ratio. The information for this is on this site.
Bob
_________________
Fiat Bravo 165 Sport |
|
| Back to top |
|
|
Admin
Site Admin
Joined: 19 Feb 2003
Posts: 1223
Location: Stafford, UK
|
|
| Back to top |
|
|
knighty
Alfasud
Joined: 12 Oct 2004
Posts: 33
Location: Essex, UK
|
| Posted: Wed Feb 20, 2008 6:42 pm Post subject: |
|
|
| thanks for the detailed reply bob, but I was rather hoping someone could tell me the answer from actually driving the car, but its nice to see your not far off my 3500 max torque estimation.........has anyone driven a 1.7 8v at 70mph in top gear recently? |
|
| Back to top |
|
|
Admin
Site Admin
Joined: 19 Feb 2003
Posts: 1223
Location: Stafford, UK
|
| Posted: Wed Feb 20, 2008 9:59 pm Post subject: |
|
|
| knighty wrote: |
| thanks for the detailed reply bob, but I was rather hoping someone could tell me the answer from actually driving the car, but its nice to see your not far off my 3500 max torque estimation.........has anyone driven a 1.7 8v at 70mph in top gear recently? |
Series 2 or series 3 as they have different diff ratios?
All the best
Keith
_________________
I owe, I owe, its off to work we go.
Bimota Forum
Stafford Christmas Lights
 |
|
| Back to top |
|
|
Lee
Alfa Sprint
Joined: 13 Mar 2003
Posts: 150
Location: Essex UK
|
| Posted: Wed Feb 20, 2008 10:38 pm Post subject: |
|
|
Cant find out until a week friday when it goes in for its MOT  sitting waiting around unused.
_________________
`97 155 2.0 16v sport
`91 33 1.7 I.E |
|
| Back to top |
|
|
ZeNiTh-PbArM
Alfa 33
Joined: 14 Mar 2003
Posts: 388
Location: Paris, France
|
| Posted: Thu Feb 21, 2008 6:45 am Post subject: |
|
|
Hi,
don't trust readings from a drive test as alfa dashboards never tell you the truth
over time, speedometers develop a tendancy to exagerate vehicle speed
and rev-meter underestimates engine revs
i remember Alfa used to write figures in the owners manual for vehicle speed in 5th gear at 1000rpm anyway.
regards,
zp |
|
| Back to top |
|
|
knighty
Alfasud
Joined: 12 Oct 2004
Posts: 33
Location: Essex, UK
|
| Posted: Thu Feb 21, 2008 9:56 am Post subject: |
|
|
| not worried if series 2 or 3, some form of actual in-car rpm figure at 70mph would be much appreciated thanks guys |
|
| Back to top |
|
|
paulhide
P4
Joined: 20 Dec 2003
Posts: 1607
Location: Oh Beautiful Billingham
|
| Posted: Thu Feb 21, 2008 11:25 am Post subject: |
|
|
Both my 16v and series 2 read just under 3500 revs at 70 in top, so looks like Bobber is spot on.
_________________
Owner's Club 33 Registrar. Now from P4 & S2 1.7 QV
http://www.alfa-pages.co.uk/viewtopic.php?t=5188 |
|
| Back to top |
|
|
baiones
Alfa Sprint
Joined: 08 Apr 2003
Posts: 130
Location: Portugal
|
| Posted: Thu Feb 21, 2008 1:23 pm Post subject: |
|
|
Hi.
Series 2 1.7 QV gearbox is longer than the series 3 16v one .
If i recall correctly the difference is in the diff...
I have a friend of mine with an 1.7 QV gearbox on a 16v and you can tell the difference...
It was reving on 5th till 7200 ( 230 ) and now goes further...
( the engine is tunned, i've pusshed a Celica once when i was going at 230 )
_________________
Carpe diem!!
Baiones
ALFA ROMEO 33 1.5 QV
ALFA ROMEO 33 1.7 QV
ALFA ROMEO 33 s16 QV
ALFA ROMEO Sprint 1.3
ALFA ROMEO 156 SW "Train Edition" ( it's a JTD... ) |
|
| Back to top |
|
|
knighty
Alfasud
Joined: 12 Oct 2004
Posts: 33
Location: Essex, UK
|
| Posted: Thu Feb 21, 2008 3:26 pm Post subject: |
|
|
| paulhide wrote: |
| Both my 16v and series 2 read just under 3500 revs at 70 in top, so looks like Bobber is spot on. |
agreed - spot on everyone, thanks very much, I have now specified a final drive ratio and 4th gear ratio that will allow 72mph at 3500 rpm, that equates to 118mph at 6000rpm, which I will never do, but I just want a sensible crusing rpm around max torque......previously it was 4200rpm at 70mph, so its a drastic improvement without the gear feeling too long. |
|
| Back to top |
|
|
ZeNiTh-PbArM
Alfa 33
Joined: 14 Mar 2003
Posts: 388
Location: Paris, France
|
| Posted: Thu Feb 21, 2008 8:57 pm Post subject: |
|
|
hi,
just had a book at my user manual and it says series 3 33s fitted with 1.7ie 8V and 16V run 31.8kph @ 1000rpm in 5th gear
regards,
zp |
|
| Back to top |
|
|
paulhide
P4
Joined: 20 Dec 2003
Posts: 1607
Location: Oh Beautiful Billingham
|
| Posted: Fri Feb 22, 2008 9:35 am Post subject: |
|
|
I agree with zp. Work out top speeds of all 1.7 series 2 and 3 and compare to max revs and I think you'll find they all have the same gearing ratios. if there is a difference it's very small.
_________________
Owner's Club 33 Registrar. Now from P4 & S2 1.7 QV
http://www.alfa-pages.co.uk/viewtopic.php?t=5188 |
|
| Back to top |
|
|
bobbber
P4
Joined: 14 May 2003
Posts: 2162
Location: The Greatest Town on Earth - Swadlincote, UK
|
| Posted: Fri Feb 22, 2008 10:46 am Post subject: |
|
|
31.8kph @ 1000rpm.
That's 19.7mph.
70 / 19.7 = 3.55
3.55 * 1,000 rpm = 3550rpm
Bob
_________________
Fiat Bravo 165 Sport |
|
| Back to top |
|
|
baiones
Alfa Sprint
Joined: 08 Apr 2003
Posts: 130
Location: Portugal
|
| Posted: Fri Feb 22, 2008 4:16 pm Post subject: |
|
|
| paulhide wrote: |
| I agree with zp. Work out top speeds of all 1.7 series 2 and 3 and compare to max revs and I think you'll find they all have the same gearing ratios. if there is a difference it's very small. |
The gear ratios are the same but not the diff .
you can checkit on this page on the above menu, the gear section :
................................................................DIFF
Alfa 33 series 2, 1.7 QV & Sprint 1.7...........10/37
Alfa 33 series 3, 1.5 & 1.7, including 16 V.....9/35
_________________
Carpe diem!!
Baiones
ALFA ROMEO 33 1.5 QV
ALFA ROMEO 33 1.7 QV
ALFA ROMEO 33 s16 QV
ALFA ROMEO Sprint 1.3
ALFA ROMEO 156 SW "Train Edition" ( it's a JTD... ) |
|
| Back to top |
|
|
paulhide
P4
Joined: 20 Dec 2003
Posts: 1607
Location: Oh Beautiful Billingham
|
| Posted: Fri Feb 22, 2008 9:32 pm Post subject: |
|
|
If that's true, what would be the revs at 70 in top for both and what would be the top speeds at 5700 revs for the S2 and 6700 revs for the S3 
_________________
Owner's Club 33 Registrar. Now from P4 & S2 1.7 QV
http://www.alfa-pages.co.uk/viewtopic.php?t=5188 |
|
| Back to top |
|
|
baiones
Alfa Sprint
Joined: 08 Apr 2003
Posts: 130
Location: Portugal
|
| Posted: Tue Feb 26, 2008 11:14 am Post subject: |
|
|
| paulhide wrote: |
| If that's true, what would be the revs at 70 in top for both and what would be the top speeds at 5700 revs for the S2 and 6700 revs for the S3 |
I have an excel file at home that calculates that .
You can input the tire size, anda then check the speed at all the gears.
I'll try to find it to post here .
For example, if you put a 33 s2 1.7 QV gearbox on a 16v, and if you could rev till 8000RPMs, that will be almost 274km/h in 5th gear!!! 
( thats the one i remember )
7200 ( rev cut on 16v ), it's about 250...
_________________
Carpe diem!!
Baiones
ALFA ROMEO 33 1.5 QV
ALFA ROMEO 33 1.7 QV
ALFA ROMEO 33 s16 QV
ALFA ROMEO Sprint 1.3
ALFA ROMEO 156 SW "Train Edition" ( it's a JTD... ) |
|
| Back to top |
|
|
paulhide
P4
Joined: 20 Dec 2003
Posts: 1607
Location: Oh Beautiful Billingham
|
| Posted: Tue Feb 26, 2008 11:32 am Post subject: |
|
|
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 
_________________
Owner's Club 33 Registrar. Now from P4 & S2 1.7 QV
http://www.alfa-pages.co.uk/viewtopic.php?t=5188 |
|
| Back to top |
|
|
baiones
Alfa Sprint
Joined: 08 Apr 2003
Posts: 130
Location: Portugal
|
| Posted: Tue Feb 26, 2008 2:49 pm Post subject: |
|
|
| paulhide wrote: |
| (...)top speed for a 16v limited to 6750 revs(...) |
weird...
All the 16v i've seen are limited to 7200...
_________________
Carpe diem!!
Baiones
ALFA ROMEO 33 1.5 QV
ALFA ROMEO 33 1.7 QV
ALFA ROMEO 33 s16 QV
ALFA ROMEO Sprint 1.3
ALFA ROMEO 156 SW "Train Edition" ( it's a JTD... ) |
|
| Back to top |
|
|
bobbber
P4
Joined: 14 May 2003
Posts: 2162
Location: The Greatest Town on Earth - Swadlincote, UK
|
| Posted: Tue Feb 26, 2008 4:35 pm Post subject: |
|
|
Ok ok...
MPH / 0.0197 = rpm
SO...
135mph = 6850rpm
117mph = 5940rpm
BUT... with the lower diff = (5940 * (9/35)) / (10/37) :
117mph = 5650rpm
That's slightly off for the 135mph Series III... but SPOT ON for the Series II @ 117mph...
That ok now Paul?
Bob
_________________
Fiat Bravo 165 Sport |
|
| Back to top |
|
|
|
