L$X$10

iTrader: (4)

Just ordered a set of 4.10s from Summit and they should be in tomorrow. Im going to test them this weekend at the LSX Challenge in Commerce, GA. Ive been running a consistent 12.3/4 at 109 with a 1.74-8 60ft on the 3.42s. This was crossing the 1320ft mark at 5100rpm. I threw in the specs on a gear convertor and it told me in order to cross the line at 6100(what my cam pulls to) with a 28" tire i would need a 4.09 gear(3.42s out, 4.10s in).
So what do you guys think it will run in Commerce??

L$X$10

iTrader: (4)

ok ill start...12 flat@111

thunderstruck507

iTrader: (18)

My car has never responded to gear changes worth a ****. Seem to do a lot more for manuals. Don't be surprised if you get .1 and 0mph.

Always feels like a different car but no notable gains at the track.

L$X$10

iTrader: (4)

not what i wanted to hear but now that its in the back of my mind i wont be as let down if i dont see any improvement, thanks for the input thunderstruck
anyone else have a guess?

BrianSF-GA

As long as it isn't raining first thing Saturday morning, we will be up there and will have to look for your truck ... pretty sharp. Without my S60 completed, the SS will remain in the garage though.

Try these calculators for simulating the 1/4 mile and gear changes ... I think they are pretty cool, although, probably not too accurate. There are too many variables to accurately predict drag times.

http://vexer.com/automotive-tools/1-...MPH-calculator

http://vexer.com/automotive-tools/speed-rpm-calculator

Mike Morris

iTrader: (55)

1 tenth and 1MPH if you are lucky

HioSSilver

iTrader: (8)

x2.....maybe a little more if you can leave on it. If you don't utilize the gear in the 1st 60-100' then it acually can hurt you. It uses power to turn more gear. I went from 4.10 to 3.90 and picked up 2mph. Hell I would'nt mind trying a 3.73.

thunderstruck507

iTrader: (18)

I went from stock 10 bolt 2.56 to 12 bolt 3.08 to 3.42 and 1/8th mile times stayed within .2 and within 1mph of each other.

Don't know the DA for each, but it was summer hot and humid every time. Just saying so you don't get your hopes up.

The car is MUCH more pleasant to drive on the street and actually gained in town MPG due to not lugging the engine on hills and stuff.

BrianSF-GA

I think you guys are missing the whole idea of gear ratio changes. Gears don't add or rob power! A lower gear ratio (higher numerically) will only change the operating rpm of your engine at a given mph. The idea of gear ratio changes is to keep your engine rpms in the range of where the power is being made. At the end of the strip (whether 1/8 or 1/4), optimally you want your engine to be at the rpm that makes peak power in 4th gear (or 1:1 transmission gear). There are two variables that affect this rpm ... transmission gearing and tire diameter. Another factor in gear selection is how fast your car is at the end of the strip (whether 1/8 or 1/4).

My car for example ... A 4.10 in an M6 with a 26" tall tire is perfect for a mid-10 second 1/4 at 128 mph crossing the line at 6,800 rpm. But, if a similar car could only run 115 mph, crossing the line at the optimal rpm of 6,800 would require a 4.56 gear. The proper gear and tire diameter make better use of the available power and can affect elapsed time and mph depending on the scenario. Too much gear can slow a car just as much as to little gear can.

HioSSilver

iTrader: (8)

A 4.10 m6 with a 26" tire won't run 128 @ 6800. It will run 122.6 on the limiter. That's why I changed to a 3.90. I had that exact setup. Also a lower gear ALWAYS uses more power, it has to turn faster so that makes it use more power.

BrianSF-GA

exactly right .... if you are bumping the limiter at 6,500 then 123 mph is your top speed in 4th gear, but what makes you think I am limited to 6,500? My rev limiter is set to 6,800 .... hence 128 mph! When I mount a 27" tire, my top speed is 133 mph and when I mount a 28" tire, my top speed is 138 mph. That gives me room to grow.

Concerning your other comment ... think about a high gear (lower numerically) as a standard length open end wrench and a low gear (higher numerically) as the same wrench with a "cheater" bar on the end. Which one are you going to exert more force to turn a bolt??

HioSSilver

iTrader: (8)

No I was hitting the limiter @ 6800. Did'nt you read my post? I had the exact set-up you said. Max speed in 4th @ 6800 is 122.6with a 26" tire. Been there done that. If you have'nt been to the track you should go. With your power you will be on the limiter way before the traps. Your theory works great for looseneing bolts.....not so much for accelerating cars. Steeper gears changes the speed at which the power is applied. From 80mph on the steep gear car gets no benifit from the steep gear.