Drag Racing Tech
Sponsored by:
Sponsored by:

Changing diff ratio for mph trap.

Old 05-22-2004, 03:37 AM
  #1  
Launching!
Thread Starter
 
GTBMad's Avatar
 
Join Date: May 2003
Posts: 200
Likes: 0
Received 0 Likes on 0 Posts
Default Changing diff ratio for mph trap.

I am running 3.73 in a A4 we are running into the 1/4 at the end at the top of 3rd gear. This is at around 6100 and right on the change up,I could change the shift point put the power is dropping of at 6300.

I was considering putting in 4.11 gear which would mean seeing the trap at around 4800 rpm and right on our TQ peak and also give us scope for a better mph.

Are we on the right track with this or am I wrong.
Old 05-22-2004, 05:40 AM
  #2  
TECH Resident
iTrader: (21)
 
Gimp98TNT's Avatar
 
Join Date: Mar 2002
Location: Bedford ,Ohio
Posts: 855
Likes: 0
Received 0 Likes on 0 Posts
Default

I don't know too much about auto's, but I thought it was bad to shift into overdrive at the track.

What i've always been told is you should be shifting 200-300 rpm's past peak horsepower, so you should aim for that.

I think that extra shift would slow you down, it did for me in my M6 when I was shifting into 5th. I was losing .2-.3 at the track.
Old 05-22-2004, 06:13 AM
  #3  
Launching!
Thread Starter
 
GTBMad's Avatar
 
Join Date: May 2003
Posts: 200
Likes: 0
Received 0 Likes on 0 Posts
Default

That would mean if I was to want to stay in third and run a higher mph I would need to go to the other way to 3.46.
Old 05-22-2004, 06:25 AM
  #4  
TECH Resident
iTrader: (21)
 
Gimp98TNT's Avatar
 
Join Date: Mar 2002
Location: Bedford ,Ohio
Posts: 855
Likes: 0
Received 0 Likes on 0 Posts
Default

If your crossing the traps at 6100 and you power is falling off at 6300 thats where you want to be.
Old 05-22-2004, 11:01 PM
  #5  
TECH Senior Member
 
Colonel's Avatar
 
Join Date: Nov 2001
Location: Troy, AL
Posts: 9,246
Likes: 0
Received 2 Likes on 2 Posts

Default

Sounds like it's just about right as it is. If anything I'd want to be crossing the line just after my HP peak (you're close enough that it would be of very little help to change anything gearingwise.) You certainly DON'T want to be crossing at your TQ peak (that has absolutely nothing to do with anything in regards to where you want to be crossing) nor do you want to be shifting into OD just before the finish line. NOT good.
Old 05-22-2004, 11:03 PM
  #6  
TECH Senior Member
 
Colonel's Avatar
 
Join Date: Nov 2001
Location: Troy, AL
Posts: 9,246
Likes: 0
Received 2 Likes on 2 Posts

Default

"That would mean if I was to want to stay in third and run a higher mph I would need to go to the other way to 3.46."

No, leave the gearing alone. If it wants to shift right at the line then put the gear selector in drive instead of overdrive....or you could raise the 3-4 shiftpoint.
Old 05-23-2004, 11:06 AM
  #7  
10 & 11 Second Club
iTrader: (2)
 
Caveman's Avatar
 
Join Date: Nov 2002
Location: Orlando Fl.
Posts: 2,584
Likes: 0
Received 0 Likes on 0 Posts

Default

Exactly what Colonel said. I just went from 3.42 to 3.73 gears and my car was shifting 3 -4 at about the 1100' mark, so now I just run in D not OD and run that little extra rpm thru the traps.


Thread Tools
Search this Thread

All times are GMT -5. The time now is 03:29 PM.