4.10 gears...not what I expected.

[Bob Eyres]

Right. Mine is an old Doug Rippie unit. A machined down stock Camaro single mass that weighs about 15lbs. It has worked well for 17 yrs.

BTW,What is the weight of the newest light weight flywheels?

[Hog]

Originally Posted by ZRXMAX

I do like the fact that 4.10 gears make the drop in rpm a little less between gears when shifting at 7000 rpm.

Lower gearing like 4.10's or 4.56's wont affect on the eamount of rpm drop when upshifting. Transmission gearing is the only way to affect the rpm drop when shifting. This is where the terms, Close-Ratio and Wide ratio transmissions come into play, with the close ratio usually having less rpm drop during upshifts.

[Hog]

Originally Posted by USAZR1

If all else is equal,both LT5's make the same power or very close to it.
So,their trap speeds should be very close to the same. Only way that would be lower is if the engine is running out of breath at the lights.
As Bob said,only the ET matters in drag racing. MPH is just a by-product though it is a honest indicator of how much horsepower you're putting down.

Yes, all else equal means that the cars are assumed to have identical variables, including having the exact same engine power output. The only variable being rear dif. gearing.

"Only way that would be lower is if the engine is running out of breath at the lights."
This makes 100% sense. I believe this to be the case in my setup, in going from a 3.08 to a 4.10 gear has had me trapping at an rpm that is beyond my power peak, where power is dropping off fast. Thanks for explaining.

xxxxxxxxxxxxxxxxxxxxxxxxx
Yes, ET is what matters in drag racing. If I cut a 2.0 60ft on pass #1 and trap a 12.0@100mph. Then on run #2 I lose traction off the line and run a 2.5 60ft time, I could theoretically run a considerably worse ET such as 13.0 seconds, yet still run the same MPH.

It could be argued that in drag racing, ET is as irrelevant as MPH because of the fact that having the quicker ET doesnt necessarily mean you will win the drag race.
ET is of course the most common method of comparing a cars acceleration. If all variables are the same, MPH is an accurate fashion in which to compare engine power.

Thank you !

[ZRXMAX]

Originally Posted by Hog

Lower gearing like 4.10's or 4.56's will have zero effect on the eamount of rpm drop when upshifting. Transmission gearing is the only way to affect the rpm drop when shifting. This is where the terms, Close-Ratio and Wide ratio transmissions come into play, with the close ratio usually having less rpm drop during upshifts.

If you look at the speed in each gear you will see that tallers gears add mph at the shift points as compared to shorter gears.

Here are the numbers for 3.07 compared to 4.10s
7000 rpm and 25.5 inch tall tire with ZF-6 ratios from Procrastination Racing's website.

http://www.angelfire.com/fl/procrastination/rear.html

3.07 1st 65.5 mph
4.10 1st 49.07 16.43 mph difference

3.07 2nd 97.17mph
4.10 2nd 72.76 24.91 mph difference

3.07 3rd 133.05
4.10 3rd 99.63 33.42 mph difference

3.07 4th 172.97
4.10 4th 129.05 43.92 mph difference

You are correct... the difference is "time" spent in each gear to gain those additional mph between shifts. The starting rpm at each shift is right around 4720 rpm.

However... It sure does seem like the rpm drop is increased with 3.07s

My speedometer calibration was off almost exactly 25% when switching from 4.10s to 3.07s. I made up a paper speedometer reference sheet for ORRing so I could look at the speedo and then look at my reference sheet.

I bought a Dakota Digital box years ago that was designed to allow me to calibrate my speedometer regardless of what gears I as using. I never could get it to alter the signal to the ECM to give me the correct speed. Has anybody here ever tried one of those boxes ?

[Hog]

Originally Posted by ZRXMAX

If you look at the speed in each gear you will see that tallers gears add mph at the shift points as compared to shorter gears.

Here are the numbers for 3.07 compared to 4.10s
7000 rpm and 25.5 inch tall tire with ZF-6 ratios from Procrastination Racing's website.

http://www.angelfire.com/fl/procrastination/rear.html

3.07 1st 65.5 mph
4.10 1st 49.07 16.43 mph difference

3.07 2nd 97.17mph
4.10 2nd 72.76 24.91 mph difference

3.07 3rd 133.05
4.10 3rd 99.63 33.42 mph difference

3.07 4th 172.97
4.10 4th 129.05 43.92 mph difference

You are correct... the difference is "time" spent in each gear to gain those additional mph between shifts. The starting rpm at each shift is right around 4720 rpm.

However... It sure does seem like the rpm drop is increased with 3.07s

My speedometer calibration was off almost exactly 25% when switching from 4.10s to 3.07s. I made up a paper speedometer reference sheet for ORRing so I could look at the speedo and then look at my reference sheet.

I bought a Dakota Digital box years ago that was designed to allow me to calibrate my speedometer regardless of what gears I as using. I never could get it to alter the signal to the ECM to give me the correct speed. Has anybody here ever tried one of those boxes ?

I use that same rpm calculator as well, small world.

In this example, you are comparing how much MPH youwwill get out of each trans gear using a 4.10 or 3.07 gear. Not the amount of engine rpm drop that will occur when you shift from 1st gear to 2nd gear.

Using the exact same parameters you have used.
3.07 rear gear ratio
shiftpoint=7000rpm
tire height 25.5"
rear gearing 3.07
trans 1st rear ratio=2.64:1
=65.5mph @ 7000rpm in 1st gear

Now you shift to 2nd gear from a hypothetical shift rpm of 7000rpm, same variables except the 2nd gear trans ratio of 1.78:1.
Now you will be travelling at 65.5mph in 2nd gear, with your tach now registering 4725 rpm.
Shiftpoint rpm minus resultant rpm in 2nd gear, for 3.07 gears
=7000rpm - 4725rpm
=2275rpm
= For 3.07 rear gears the RPM drop of 2275rpm when shifting from 1st gear to 2nd gear

4.10 rear gear ratio
Now lets repeat for a 4.10 gearing scenario
Shiftpoint =7000rpm
tire height 25.5"
rear gearing=4.10
trans 1st rear ratio=2.64:1
=49.0mph @ 7000rpm in 1st gear

Now we shift to 2nd gear at our hypothetical 7000rpm shiftpoint, same variables except 2nd gear ratio of 1.78:1. Now we will be travelling at 49mph in 2nd gear, with the tach reading 4725rpm.

Shiftpoint rpm minus resultant rpm in 2nd gear, for 4.10 gears
7000rpm - 4725rpm
=2275RPM
=For 4.10 rear gears, the RPM drop of 2275rpm when shifting from 1st gear to 2nd gear.

As you can see, the rpm drop in both cases is exactly the same, therefore rear gear ratios have no effect on amount of engine RPM drop when upshifting. The only way to change the amount of rpm drop during an upshift is to change the gearing inside the transmission.

[XfireZ51]

From what I am reading here, it would explain why I would be accelerating on Lgaff's car in the second 1/8. Just run out of real estate to catch up.

[USAZR1]

Little did I know how much money I wasted changing gearing in so many cars & bikes over the last 45 years..
Carry on,mates!

[ZRXMAX]

Originally Posted by USAZR1

Little did I know how much money I wasted changing gearing in so many cars & bikes over the last 45 years..
Carry on,mates!

I don't know about the wasted part you mentioned Clint. Back in the day I changed sprockets on my 750 Honda from 18-48 to 16-52. From that point on I could do wheelies from a dead stop!

[Bob Eyres]

Originally Posted by Hog

It could be argued that in drag racing, ET is as irrelevant as MPH because of the fact that having the quicker ET doesnt necessarily mean you will win the drag race.

Except for one thing, E.T. is the only relevant factor.
Except for the factor of who leaves first, who gets the jump.
That's the essence of bracket racing, which programs the tree to hold back the the quicker car to make the race even. Then, whoever responds to the light quicker theoretically wins.
In a "heads up" race, both drivers respond to the same light sequence. If both cars run the same e.t., then whoever leaves first wins.

This puts driver skill into the equation. Shifting quicker also allows you to minimize the rpm drop between gears.

[Schrade]

Originally Posted by ZRXMAX

If you look at the speed in each gear you will see that tallers gears add mph at the shift points as compared to shorter gears.

Here are the numbers for 3.07 compared to 4.10s
7000 rpm and 25.5 inch tall tire with ZF-6 ratios from Procrastination Racing's website.

http://www.angelfire.com/fl/procrastination/rear.html

3.07 1st 65.5 mph
4.10 1st 49.07 16.43 mph difference

3.07 2nd 97.17mph
4.10 2nd 72.76 24.91 mph difference

3.07 3rd 133.05
4.10 3rd 99.63 33.42 mph difference

3.07 4th 172.97
4.10 4th 129.05 43.92 mph difference

You are correct... the difference is "time" spent in each gear to gain those additional mph between shifts. The starting rpm at each shift is right around 4720 rpm.

However... It sure does seem like the rpm drop is increased with 3.07s

My speedometer calibration was off almost exactly 25% when switching from 4.10s to 3.07s. I made up a paper speedometer reference sheet for ORRing so I could look at the speedo and then look at my reference sheet.

I bought a Dakota Digital box years ago that was designed to allow me to calibrate my speedometer regardless of what gears I as using. I never could get it to alter the signal to the ECM to give me the correct speed. Has anybody here ever tried one of those boxes ?

I had one installed in my automatic conversion. SGI-5 C

Worked properly at speed, but at '0' MPH, it gave an erratic reading, for which there was a troubleshoot symptom. Followed it to a 'T', and didn't solve the problem.

Ended up removing it, and using the Tranny Control Module for speed signal feed.

Solved it. Sold the DD on eBay, guy had no problems with it on his project wheels...

http://www.zr1.net/forum/showthread.php?t=19299