Thoughts on Gear Change for Supercharged C3
#1
Racer
Thread Starter
Thoughts on Gear Change for Supercharged C3
Hi, I have a somewhat unusual 81 vette with a stock L81 engine & a Magnuson MC220 Supercharger hooked to a Doug Nash 5 speed. It feels as if I still have the stock 2.72 gears in it. If I use the old "10" rule of "1st rear ratio x rear axle ratio" it would indicate that I should use the 3.08 ratio. Also, the original literature from Magnuson states that the 3.08 ratio is excellent. The difference in gear ratio is a little over 13%. Any input on this? I know it's a very unusual situation. Thanks in advance!
#2
Race Director
Hi, I have a somewhat unusual 81 vette with a stock L81 engine & a Magnuson MC220 Supercharger hooked to a Doug Nash 5 speed. It feels as if I still have the stock 2.72 gears in it. If I use the old "10" rule of "1st rear ratio x rear axle ratio" it would indicate that I should use the 3.08 ratio. Also, the original literature from Magnuson states that the 3.08 ratio is excellent. The difference in gear ratio is a little over 13%. Any input on this? I know it's a very unusual situation. Thanks in advance!
#3
Racer
Thread Starter
Thanks 63Mako. I guess I should have posted the Transmission Ratios. Note how low 1st is. "3.27/2.13/1.57/1.24/1". I also wondered how the Positive Displacement blower affects diff ratio choice.
#4
Race Director
I figured it was a 3.27. Just like any power adder, likes low gears, tighter ratios and RPM. Others will know better, Im not a blower guy. That said a 13% ratio change is not real noticable and would barely be worth the effort. A 25% difference will be noticable SOP and a 3.36 to 1 in fifth is not bad to cruise with.
#5
Le Mans Master
with experience on my 2 favorite play toys , when it comes to gears or breast implants always go one size bigger than you planned. don't pay to do something twice because you didn't go big enough. right suzy,?
#8
Team Owner
superchargers are made to run in lower rpm motors. where N/A motors need rpm to make power
#9
Le Mans Master
your gear pattern plate on the console says Richmond 5 speed on it i think. Do you have any idea where to get one of those? I've seen a few in cars and can only find the 6 speed version
#10
Race Director
1st gear is the same as my 61.(4.11x2.20 1st)
something else is wrong if it is not quick off the line. Put a boost gauge on it and make sure it is making boost.
something else is wrong if it is not quick off the line. Put a boost gauge on it and make sure it is making boost.
Last edited by Matt Gruber; 02-28-2013 at 07:15 AM.
#12
Racer
Thread Starter
Yes, I did just buy it in November. I would call Richmond to see if they would know where to source the plaque. truthfully, I haven't driven it much, I bought it in November & haven't put plates on it yet, so I drove it 25 miles in a snow storm to it's new home & a few blasts up & down my rural road. I'm just getting "yancy"! Spring is almost here!
#13
Le Mans Master
Interesting blower setup on that car! I've never seen anything like that before.... Pretty cool stuff..
Yeah I'd leave the 3.08 in it since you have a Nash with the low first gear... Then you'll still have decent highway RPMs.. You "could" go to a 3.36 and still have OK highway cruise rpms but I doubt you notice much increase acceleration...Not enough to spending the money to change gears/diffs anyway..
Yeah I'd leave the 3.08 in it since you have a Nash with the low first gear... Then you'll still have decent highway RPMs.. You "could" go to a 3.36 and still have OK highway cruise rpms but I doubt you notice much increase acceleration...Not enough to spending the money to change gears/diffs anyway..