Honda DPFI vs MPFI... - Page 4 - Fuelly Forums

Android Users - Coming Soon! - Migrating from aCar 4.8 to 5.0

Reply
 
Thread Tools Display Modes
 
Old 03-09-2009, 12:11 PM   #31
Registered Member
 
GasSavers_bobski's Avatar
 
Join Date: May 2007
Posts: 463
Country: United States
Quote:
Originally Posted by aalb1 View Post
my suggestion is swap the SI 5th gear to an hf 5th gear. You'll keep your first through fourth for acceleration purposes but have lower rpm's for cruising... best of both worlds!
Yeah, a little. The HF does (as do most '92-01 Civics) have a longer 5th gear ratio (0.694 HF vs. 0.771 DX/Si), but it's super long gearing is mostly a result of its final drive (4.25 Si, 3.888 DX, 2.95 HF fed, 3.25 HF CA/VX). A 5th gear from an HF or newer Civic would reduce your cruising RPMs by about 10%. A DX final drive would reduce the RPMs across the board by about 9%.
__________________

GasSavers_bobski is offline   Reply With Quote
Old 03-10-2009, 09:05 AM   #32
Registered Member
 
aalb1's Avatar
 
Join Date: Apr 2007
Posts: 207
Country: United States
Quote:
Originally Posted by bobski View Post
Yeah, a little. The HF does (as do most '92-01 Civics) have a longer 5th gear ratio (0.694 HF vs. 0.771 DX/Si), but it's super long gearing is mostly a result of its final drive (4.25 Si, 3.888 DX, 2.95 HF fed, 3.25 HF CA/VX). A 5th gear from an HF or newer Civic would reduce your cruising RPMs by about 10%. A DX final drive would reduce the RPMs across the board by about 9%.
This is exactly how it will translate so you can decide for yourself:

Straight SI Tranny in 5th Gear:
1500rpm - 30.86 MPH
1750rpm - 36 MPH
2000rpm - 41.14 MPH
2250rpm - 46.29 MPH
2500rpm - 51.43 MPH
2750rpm - 56.57 MPH
3000rpm - 61.72 MPH
3250rpm - 66.86 MPH
3500rpm - 72 MPH
3750rpm - 77.15 MPH
4000rpm - 82.29 MPH

SI Tranny W/HF 5th

1500rpm - 34.28 MPH
1750rpm - 40 MPH
2000rpm - 45.71 MPH
2250rpm - 51.42 MPH
2500rpm - 57.14 MPH
2750rpm - 62.85 MPH
3000rpm - 68.56 MPH
3250rpm - 74.28 MPH
3500rpm - 79.99 MPH
3750rpm - 85.71 MPH
4000rpm - 91.42 MPH
__________________

__________________
aalb1 is offline   Reply With Quote
Old 03-10-2009, 09:21 AM   #33
Registered Member
 
Join Date: Nov 2007
Posts: 1,111
Country: United States
Send a message via AIM to dkjones96
Wow, I'm getting tooooo used to my new gearing cuz those numbers look high. 0.69:1 and 3.55 rear end gives me 60mph at 1750 rpm. If the TC is locked I'm at around 1175 rpm at 40.
__________________
- Kyle
dkjones96 is offline   Reply With Quote
Old 03-10-2009, 10:57 AM   #34
Registered Member
 
aalb1's Avatar
 
Join Date: Apr 2007
Posts: 207
Country: United States
yea displacement is a big factor... when I had a 2000 Civic SI my dad was simply amazed how that 1.6L would cruise @ 80mph @ 4500rpm and still get 30mpg
__________________
aalb1 is offline   Reply With Quote
Old 03-10-2009, 11:57 AM   #35
Registered Member
 
GasSavers_bobski's Avatar
 
Join Date: May 2007
Posts: 463
Country: United States
Quote:
Originally Posted by dkjones96 View Post
0.69:1 and 3.55 rear end gives me 60mph at 1750 rpm. If the TC is locked I'm at around 1175 rpm at 40.
I assume you're talking about your Durango? Don't forget the last element between the drive shaft and road... Wheel and tire size can play a big role in gearing. '88-91 Civics and CRXs have an overall wheel/tire diameter of about 23", meaning around 875 revolutions per mile.
GasSavers_bobski is offline   Reply With Quote
Old 03-10-2009, 01:01 PM   #36
Registered Member
 
Join Date: Nov 2007
Posts: 1,111
Country: United States
Send a message via AIM to dkjones96
Yeah, the Durango tires are 31.5"

Now I've got a question about that. If I had the 8.25" ring gear instead of the 9.5" that I have and still had the same tires and 3.55s would it change that final ratio? Like, right now that's a 3.32:1 ratio, would the 8.25 make it a 3.82:1?

I'm pretty sure it does. Just verifying.
__________________
- Kyle
dkjones96 is offline   Reply With Quote
Old 03-10-2009, 02:45 PM   #37
Registered Member
 
GasSavers_bobski's Avatar
 
Join Date: May 2007
Posts: 463
Country: United States
The ratio depends on the number of teeth on meshing gears, not their physical dimensions. So, you're going to have to tell me how many teeth are on each gear, assuming the pitch of the teeth, physical location and such allow them to mesh properly.
GasSavers_bobski is offline   Reply With Quote
Old 03-10-2009, 02:56 PM   #38
Registered Member
 
theholycow's Avatar
 
Join Date: Apr 2008
Posts: 6,624
Country: United States
Send a message via ICQ to theholycow Send a message via AIM to theholycow Send a message via MSN to theholycow Send a message via Yahoo to theholycow
Wouldn't the tooth size have to be the same, therefore they would increase proportionally with the larger dimension of gear?
__________________
This sig may return, some day.
theholycow is offline   Reply With Quote
Old 03-10-2009, 03:25 PM   #39
Registered Member
 
Join Date: Nov 2007
Posts: 1,111
Country: United States
Send a message via AIM to dkjones96
That's what I was thinking. 8.25:31.5 vs 9.5:31.5.

The 3.55 ring and pinion ratio stays the same.
__________________
- Kyle
dkjones96 is offline   Reply With Quote
Old 03-10-2009, 05:01 PM   #40
Registered Member
 
theholycow's Avatar
 
Join Date: Apr 2008
Posts: 6,624
Country: United States
Send a message via ICQ to theholycow Send a message via AIM to theholycow Send a message via MSN to theholycow Send a message via Yahoo to theholycow
That's the opposite of what I was saying...the ring mates to the pinion, and if you change the size of the ring it will have more teeth, so it changes the ring-pinion ratio.

The end result is the same as comparing the ring to the tire as long as the pinion is staying the same.
__________________

__________________
This sig may return, some day.
theholycow is offline   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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Help...MPG calculator not working djquik1 Fuelly Web Support and Community News 1 10-18-2010 05:57 AM
Heat Pump Hockey4mnhs General Discussion (Off-Topic) 5 10-18-2007 04:46 PM
Doh! GasSavers_Crystal General Discussion (Off-Topic) 5 06-29-2007 02:39 PM
New to GS - proudly got 38mpg in my 90 corolla today! aelfwyne Introduce Yourself - New member Welcome 9 09-25-2006 12:47 PM
Ever wonder how wind will effect your mileage? Lots of interesting Prius info krousdb General Fuel Topics 4 02-08-2006 08:49 PM

Powered by vBadvanced CMPS v3.2.3


All times are GMT -8. The time now is 03:02 PM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.