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Discussion Starter #1
IF you went to 3.15's?????
Top end would be faster for sure, but what about hooking quicker?/.......:-?
 

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ZO6LS6 said:
IF you went to 3.15's?????
Top end would be faster for sure, but what about hooking quicker?/.......:-?
I'm going to make some assumptions here based on experience...but not with this particular car (being that mine has not arrived yet ;)).

Is top-speed drag limited or gearing limited? If its drag-limited, then going to 3.15s might actually _hurt_ top-end performance.

As far as hooking quicker...this might help a bit, but you will give up a LOT once the car is hooked up in 1st gear. You get bit in every other gear, with the only possible advantage being that of the first 60'. The car would be less fun to drive around, too.

With some of these excellent 60' times guys are getting on the stock radials (1.8x are very, very good and even 2.0x isn't terrible), I'd say 3.15s would not help the situation.
 

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Since our cars can't top out in 6th gear at redline then going to 3.15 gears wouldn't be of any benefit there and I really doubt it would help 1/4 mile times, but it just might hurt them! I am not a racer so that is not fact I just stated, only MHO.;) Bill
 

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That is an interesting question. If you are realy interested figure out if the car could make the 1/4 in 3rd gear, if it will go 116-18 it just might be for the average driver eliminating the 3-4 shift. Our cars are gear-rpm limited in 5th but dont have the power to pull 6th higher so it might help top speed also. Ric
 

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PowerShifter said:
That is an interesting question. If you are realy interested figure out if the car could make the 1/4 in 3rd gear, if it will go 116-18 it just might be for the average driver eliminating the 3-4 shift. Our cars are gear-rpm limited in 5th but dont have the power to pull 6th higher so it might help top speed also. Ric
Ok, this is what I wanted to know...gear limited in 5th and drag limited in 6th.

In this case it just _might_ help top-end power...or you could get into a problem where 5th is now too tall to pull any higher.

The point you raise about crossing the traps in 3rd instead of having to make that one extra shift is a good one. However, this would obviously work for a _stock_ car only...once you make just a few mods (to run 120+mph trap speeds), you're going to have to shift into 4th anyway.

Plus, I still think whatever you'd gain in 60' due to less wheelspin (which would be very little in your case Powershifter...didn't you already get a 1.77 60' time?), you'd more than lose for the last 1260' of the track due to less torque multiplication through the remaining part of the run. So while the 60' split might be a fraction better, I'd guess by the 660' it would be even or worse.
 

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Wes, I am to lazy to find my calculator to figuer it out. There is a larger spaceing in ratio between 3-4 so the average driver is lossing more than someone that can make a fast power shift. We need Roger Ramjet and his quarter Jr. program to figuer out the best case. I was assuming a stock 01-02 Z06. I dont know how many mph our cars would be going with the 3.15 @6600 in 3rd. But it is an interesting question. What would the mph be in 5th at 6600 and the 3.15 be? I would think the 02 have the power to go @185+. Ric
 

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I ran your question thru Quarter Jr.

Going from 3.42 gear to a 3.15 causes an increase in ET of .16 sec, increase in 60' of .06 sec, and an increase of .7 mph. Plus, you still need to shift to 4 th gear.

Bottom line - don't do it!
 

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Discussion Starter #8
Roger

Since "Your Da' man", please run the same stats, using a 3.73, & a 3.90.....................We'll go the OTHER way......and see the increase..............:)
 

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Gear Ratio - Axle Ratio - Tire Dia - Eng RPM - MPH
1 - 2.97 - 3.15 - 26 - 6600 - 54.6
2 - 2.07 - 3.15 - 26 - 6600 - 78.3
3 - 1.43 - 3.15 - 26 - 6600 - 113.3
4 - 1.00 - 3.15 - 26 - 6600 - 162.1
5 - 0.84 - 3.15 - 26 - 6600 - 192.9
6 - 0.56 - 3.15 - 26 - 6600 - 289.4

These are the numbers using the 3.15 axle. I don't have any drag info but I doubt that a stock engine could pull 5th to 6600 rpm.

I have this on an Excel spreadsheet. I'll send it to you, if you want. It won't go on the system here so e-mail me.

[email protected]
 

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Thanks Roger, I knew I could count on you! I have a question for ya in the raceing section if you have time. Ric
 

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Hey Roger,

Great info. Does your program have a way to calculate for traction? I have an old DeskTop Dragstrip program, and while I know it has to be less sophisticated than the one you're using, it was realistic in that you couldn't "overgear" or "overpower" a car and still get traction.

In comparison to your data, I know there are a number of guys getting 1.8x 60's times with 3.42s. IMHO, I don't see someone like this benefitting at all from a 3.73/3.90 gear ratio. They are already at the adhesion limit of the stock radial tires. More TQ multiplication will just mean more tirespin...slower times.

Throw some slicks or drag radials on it, and it will be a different story of course.
 

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Yes, Quater Jr does have a tire traction input.

Using the 3.73 gears, which I consider perfect for the street, and launching at 4000 rpm with stock tires, at Std Day conditions (100% AD), the 60' time is predicted to be 1.74 sec. For a 102% AD run, the 60' time drops to 1.72 sec.
 

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Discussion Starter #15 (Edited)
What Is

Considered 100% AD?????????
And does this program reflect the top ends, if these ratio's were used....
Someone in an earlier thread said lower ratio= MOST bang for buck.
Some say, intake......well, using gears & intake, seems like you could make up some serious time on the strip........
What would the top end be in each gear, using the current M12, and 3.73'[email protected]
Roger, pls don't take your time to do this if you are busy or don't want to.......no problem............
I, for one, have THOROUGHLY enjoyed your posts using the Jr. system........fascinating stuff.
Maybe if I buy Wes's lunch, he will Edddicate me!!!!!!!!!!
Heck, some guy's won't even answer a simple private message........:roll:
 

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ZO6LS6 said:
What is Considered 100% AD?????????
And does this program reflect the top ends, if these ratio's were used....
Someone in an earlier thread said lower ratio= MOST bang for buck.
Some say, intake......well, using gears & intake, seems like you could make up some serious time on the strip........
What would the top end be in each gear, using the current M12, and 3.73'[email protected]
Roger, pls don't take your time to do this if you are busy or don't want to.......no problem............
I, for one, have THOROUGHLY enjoyed your posts using the Jr. system........fascinating stuff.
Maybe if I buy Wes's lunch, he will Edddicate me!!!!!!!!!!
Heck, some guy's won't even answer a simple private message........:roll:
100% air density is considered to be 60 F temp, 0% relative humidity, and 29.92 in hg observed barometer pressure (not corrected to sea level - the way the weather service does). The equations are kinda messy and invloved. A race weather station that calcs HP correction factor is the hot setup.

Yes, Quarter Jr does show the top mph for each gear at the shift point. Performance Trends Drag Analyzer program is more sophiscated. And the one I would suggest buying.

Gear Gear Ratio Axle Ratio Tire Dia Eng RPM MPH
1 2.97 3.73 26 6600 46.1
2 2.07 3.73 26 6600 66.1
3 1.43 3.73 26 6600 95.7
4 1.00 3.73 26 6600 136.9
5 0.84 3.73 26 6600 162.9
6 0.56 3.73 26 6600 244.4
 

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Discussion Starter #17
Roger,

So, theoretically, going to the 3.73's only cost's you around 10 mph, 10 top end.............
Not a bad trade for the increased times savings.............PLUS, a real SOTP feel......:D
 

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Re: Roger,

ZO6LS6 said:
So, theoretically, going to the 3.73's only cost's you around 10 mph, 10 top end.............
I see about 14 mph delta.
3.42 in 5th 177 mph
3.73 in 5th 163 mph

About 150 rpm increase in 6th at 65 mph. Hardly noticable for gas milage. Like I said, I consider 3.73 gears perfect fot the street.
 

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Re: What Is

ZO6LS6 said:
Maybe if I buy Wes's lunch, he will Edddicate me!!!!!!!!!!
Heck, some guy's won't even answer a simple private message........:roll:
Terry,

Did I miss a PM from you? If so, please just send me an e-mail. I don't get to the boards every day. :)

But, yeah...we've got to do lunch sometime...and no, you certainly don't have to buy!
 

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Roger Ramjet said:
Yes, Quater Jr does have a tire traction input.

Using the 3.73 gears, which I consider perfect for the street, and launching at 4000 rpm with stock tires, at Std Day conditions (100% AD), the 60' time is predicted to be 1.74 sec. For a 102% AD run, the 60' time drops to 1.72 sec.
I'll just have to sit here and humbly dispute the program. I'm no engineer, so I know I have far less credentials than those who wrote the program.

However, in real life a Goodyear Supercar tire will not hold a 4000rpm launch with a car making this much power ... and certainly not with 3.73 rear gearing, IMHO.

I would like to see this tried by someone who's willing to spend the $$ to have their gears swapped.

I predict massive tirespin. And if you slip the clutch to never, never land while applying too much throttle then you'll be replacing a clutch after 10 passes or so.

Throw on some ET Streets and sidestep the clutch at 4000 and hold on, though!!!! :D Of course, there may be a couple of half-shafts in pieces at the starting line, but....
 
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