No username? Register here.
Go Back   ZClub.net > General > Rally & race
Click here to visit the Opie Oils website

Reply
 
Thread Tools Display Modes
  #1  
Old 03-06-2017, 09:25 PM
Rob Gaskin's Avatar
Rob Gaskin Rob Gaskin is offline
Membership Secretary
Sixth gear
 
Join Date: Dec 2002
Location: Hinckley
Posts: 10,572
Member 214
Get your calculators out

Ok, for all you budding 'Regularity Rally Navigators' here is a question:

If you have to average 60 mph for 2 miles and you actually do the first mile at 30 mph what speed have you got to do the second mile at?
__________________
240Z '71 Built and Modified by DJR
260Z Super Samuri
Reply With Quote
  #2  
Old 03-06-2017, 09:27 PM
jonbills's Avatar
jonbills jonbills is offline
Z Club member
Fifth gear
 
Join Date: Sep 2005
Location: M6
Posts: 2,394
Member 254
You've got 2 minutes to do 2 miles.
you do the first mile in 2 minutes @ 30 mph.
you need to be infinitely fast for the 2nd mile.
__________________
1974 260z
Reply With Quote
  #3  
Old 03-06-2017, 11:23 PM
Rob Gaskin's Avatar
Rob Gaskin Rob Gaskin is offline
Membership Secretary
Sixth gear
 
Join Date: Dec 2002
Location: Hinckley
Posts: 10,572
Member 214
Quote:
Originally Posted by jonbills View Post
You've got 2 minutes to do 2 miles.
you do the first mile in 2 minutes @ 30 mph.
you need to be infinitely fast for the 2nd mile.
Correct. I got it too, but most people apparently say 90mph!

Ok next question:

At 3000 rpm (fairly relaxed pace) how many times does a piston in any engine go up and down in one second?

And how many times do the valves open and close in that second?
__________________
240Z '71 Built and Modified by DJR
260Z Super Samuri
Reply With Quote
  #4  
Old 03-06-2017, 11:50 PM
jonbills's Avatar
jonbills jonbills is offline
Z Club member
Fifth gear
 
Join Date: Sep 2005
Location: M6
Posts: 2,394
Member 254
3000 rpm = 50 revolutions/second. So the piston goes up and down 50 times.
each valve opens and closes 25 times per second, unless it's a 2 stroke, in which case it's probably 50 too.
__________________
1974 260z
Reply With Quote
  #5  
Old 04-06-2017, 02:39 AM
Jimbo's Avatar
Jimbo Jimbo is offline
1978 260z in yellow
Third gear
 
Join Date: Jul 2015
Location: Birmingham
Posts: 375
Member 1049
3000rpm devided by 60secs = 50 revs per second
50 divided by 4 stroke cycle for one valve = 12.5 so 2 valves would be 25

makes sense to me jonbills
Reply With Quote
  #6  
Old 04-06-2017, 07:44 AM
johnymd's Avatar
johnymd johnymd is offline
Z Club member
Sixth gear
 
Join Date: Jun 2003
Location: in denial
Posts: 5,500
Member 514
Cam rotates at half the speed of the crank so each valve would open and close 25 times a second.
__________________
Drives:

'73 240z 1JZ-GTE. Was pretty quick. 11.10@132.5mph
'72 240z RHD (4BOA) Painted and waiting assembly.
'72 240z LHD Silver "Rat look" daily runaround.
'76 280z ExLHD Red v8 Lexus powered restomod.
'74 260z LHD Restomod just started.
'71 240z LHD zg arched. Still in California.

Go to: www.240z.me.uk to checkout the cars.
Reply With Quote
  #7  
Old 04-06-2017, 07:48 AM
jonbills's Avatar
jonbills jonbills is offline
Z Club member
Fifth gear
 
Join Date: Sep 2005
Location: M6
Posts: 2,394
Member 254
Which is a lot, when you think about it 🤓
__________________
1974 260z
Reply With Quote
  #8  
Old 04-06-2017, 08:00 AM
johnymd's Avatar
johnymd johnymd is offline
Z Club member
Sixth gear
 
Join Date: Jun 2003
Location: in denial
Posts: 5,500
Member 514
It's a lot more at the red line. Gives you something to think about when the engine screaming at North Weald today.
__________________
Drives:

'73 240z 1JZ-GTE. Was pretty quick. 11.10@132.5mph
'72 240z RHD (4BOA) Painted and waiting assembly.
'72 240z LHD Silver "Rat look" daily runaround.
'76 280z ExLHD Red v8 Lexus powered restomod.
'74 260z LHD Restomod just started.
'71 240z LHD zg arched. Still in California.

Go to: www.240z.me.uk to checkout the cars.
Reply With Quote
  #9  
Old 04-06-2017, 10:26 AM
Rob Gaskin's Avatar
Rob Gaskin Rob Gaskin is offline
Membership Secretary
Sixth gear
 
Join Date: Dec 2002
Location: Hinckley
Posts: 10,572
Member 214
Correct guys and when I was discussing this 'in the pub' recently people didn't believe me.

I'm sure Joe Public thinks that the piston goes up and down about 5 times per second - if they ever even consider it.

Old F1 engines used to rev to 18k, so each piston goes up AND down 300 times per second!

Extract from the V6 regs of about 10 years ago:

Engines are limited to 18,000rpm

No wonder the components of the engine are as light as poss.!
__________________
240Z '71 Built and Modified by DJR
260Z Super Samuri
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +1. The time now is 03:23 AM.

The Future Is Bright... The Future Is ZClub!

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Copyright ZClub.net, All Rights Reserved.