4.10's and 1/4 mile trap speed
11-17-2014, 08:51 PM
#1
Instructor
Thread Starter
4.10's and 1/4 mile trap speed
I have a 2007 Z51 with an RPM stage 4 diff loaded with 4.10's. The car is bolt-on only. I was trying to decide on 4.10's or 3.90's and I kept reading on here that 4.10's are the best until you go with forced induction but I think I was hitting the cut-off before I crossed the line. I was running 121-122mph the last couple times at the track but this was the first time I was doing 124+mph. I could see that I wasn't over the line when I hit the rev limiter. On the 121-122ish passes I was crossing the line before the cut. I plan on going with Heads and cam over the winter and I'm thinking I will already have to switch to 3.90's. I was hoping I'd be good until I go with a Supercharger but I think I'm at the limit already. Anyone have experience/thoughts on this?
11-17-2014, 09:08 PM
#2
Racer
I was between 480 to 500 rwhp. The 4.10 gears were too much gearing. I switched to the 3.90 when I was getting the diff fixed. I didn't get to test it because a lifter collapsed. The 3.90 should be good for the 480 to 500 rwhp range. The only reason I stay close to the 4.10 with the 3.90 gears was because of the cam I had at the time. I just suggest consider what cam you are getting first and the ability on when you can use 6th gear without surging. You might consider 3.73 gears for both n/a and boosted. This would save a gear change for later.
11-17-2014, 09:43 PM
#3
Le Mans Master
You need to do the math with the diameter of tire and your limiter set point along with rear different gearing. The calculators will be very close. Factor in tire growth if slick.
And measure tire on exact rim for accuracy.
And measure tire on exact rim for accuracy.
11-17-2014, 10:31 PM
#4
Instructor
Thread Starter
I'm running 275/40/17's on C5Z fronts with a stock rev limit. How would I calculate that?
My fastest run was 124.60, also had 124.50, 124.36, 124.28 and 124.22 Those were all 11.4x's
I'm thinking that's it, I wonder what that is costing me in my E.T's since I'm pretty sure it's before I cross the line, every little bit counts
My fastest run was 124.60, also had 124.50, 124.36, 124.28 and 124.22 Those were all 11.4x's
I'm thinking that's it, I wonder what that is costing me in my E.T's since I'm pretty sure it's before I cross the line, every little bit counts
Last edited by Vade46; 11-21-2014 at 03:27 PM. Reason: Had wrong tire size. Thought they were 275/45
11-17-2014, 11:21 PM
#5
Racer
try this: you should be able to search for your tire diameter and transmission gear ratio. The 4th gear is generally 1:1 ratio
http://www.f-body.org/gears/
MN6 base and z51 trans gears
http://www.corvetteactioncenter.com/...008tr6060.html
http://www.f-body.org/gears/
MN6 base and z51 trans gears
http://www.corvetteactioncenter.com/...008tr6060.html
Last edited by needcheese; 11-17-2014 at 11:40 PM. Reason: changed url and added trans gear link
11-18-2014, 01:20 AM
#6
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Member Since: Sep 2007
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Adding a cam will allow you more top end RPM. Adjust the rev limiter to match. Problem solved. Stay with the 4.10.
11-18-2014, 06:50 AM
#7
Tech Contributor
Speaking from experience with your setup, + cam and heads, your 4:10's are good until about 135 with your tires at 6800 rpm. I've had both and would never go back to 3.90's. The 4:10's make the launch a lot easier.
Check 1 minute into the video.
Check 1 minute into the video.
11-18-2014, 10:02 AM
#9
Tech Contributor
Me? Thanks if so.
But FARTPIPE sets the bar. See below. Difference is, he gets a new car every 3-4 months, I keep mine for 77k miles and 8 years so far, so I'm a little kinder to my equipment. Breaking two third gear blocker rings will make you slow down your shifting a bit, I can tell you. That's a $2,500 repair.
https://www.corvetteforum.com/forums...-w-dr-s-2.html
[/QUOTE]
But FARTPIPE sets the bar. See below. Difference is, he gets a new car every 3-4 months, I keep mine for 77k miles and 8 years so far, so I'm a little kinder to my equipment. Breaking two third gear blocker rings will make you slow down your shifting a bit, I can tell you. That's a $2,500 repair.
https://www.corvetteforum.com/forums...-w-dr-s-2.html
[/QUOTE]
Here is FARTPIPE's scan on the 10.42 pass.
Some interesting things to note.
1. Launch rpm = 4373, 100% throttle, full boost of 8.2 psi (calculated as the scanned map of 22.9 psi - 14.71 baro (per dragtimes, @ 3 pm, 54 degrees, 44% humidity, 29.95 baro, (29.95 inches of mercury = 14.71 psi), = (204) DA). I'm assuming on these blower calcs as I'm a N/A guy...I look for .99-100 kpa and know my filter's not plugged and I'm good.
2. Interestingly, the car was revving up to 5357 under about 1/2 throttle, then FARTPIPE floored it, the RPM's went down to 4307, boost was building to max of 8.2 during that time...up to 4373 as the car spun just a smigen at launch (FARTPIPE compensated by reducing throttle 5% for .130 of a second), then bogged down to 3424 during the launch sequence (all at 100% throttle). Not sure why the RPM's went down when he floored it, clutch in, from where it was at 1/2 throttle...must be some sort of torque management kicking in. My car doesn't do that.
Some data:
0-60 time = 2.195 seconds...though if his DR's are shorter than stock that time is a little off...still...blazing fast...assuming they are short, even using 0-65 mph it's 2.455...handily beating the Veyron.
60-130 time = 6.165 seconds.
1-2 shift time, .195 seconds, 6,564 rpm.
2-3 shift time, .260 seconds, 6,621 rpm.
3-4 shift time, .195 seconds, 6,813 rpm. I wonder if FARTPIPE went clutch in before letting off the gas on 3-4, as you can see the rpm flare up to 6,922 when he was off the gas.
It appears the scanner only reads time in .065 increments...3x.065=.195 so the shifts were likely between .130 seconds and .195 seconds, but below .195 except for the 2-3.
FARTPIPE got about 13 mph wheel spin on the 1-2 shift, 8 mph on the 2-3 shift, and 10 mph on the 3-4. Some ET left on the table there, but I couldn't find any other ET left on the table.
Car was running about 26 degrees timing, IAT at the start of the run was 75, going down to 63 degrees in 4th gear through the end of the run. I'm not familiar if that's the pre-blower IAT or the IAT after compression on the pid that was scanned. My .cfg wouldn't read the knock sensor for some reason but based on the commanded timing line I don't think it had any knock. Interesting that this blown car takes more timing than my N/A car.
FARTPIPE ran it to 6400 in 4th...145 mph....in 10.65 seconds. Feels good to go that fast. I won't type how long it took my car to go 145.
Overall, one of the cleanest runs I've ever reviewed.
Hats off to you FARTPIPE.
Some interesting things to note.
1. Launch rpm = 4373, 100% throttle, full boost of 8.2 psi (calculated as the scanned map of 22.9 psi - 14.71 baro (per dragtimes, @ 3 pm, 54 degrees, 44% humidity, 29.95 baro, (29.95 inches of mercury = 14.71 psi), = (204) DA). I'm assuming on these blower calcs as I'm a N/A guy...I look for .99-100 kpa and know my filter's not plugged and I'm good.
2. Interestingly, the car was revving up to 5357 under about 1/2 throttle, then FARTPIPE floored it, the RPM's went down to 4307, boost was building to max of 8.2 during that time...up to 4373 as the car spun just a smigen at launch (FARTPIPE compensated by reducing throttle 5% for .130 of a second), then bogged down to 3424 during the launch sequence (all at 100% throttle). Not sure why the RPM's went down when he floored it, clutch in, from where it was at 1/2 throttle...must be some sort of torque management kicking in. My car doesn't do that.
Some data:
0-60 time = 2.195 seconds...though if his DR's are shorter than stock that time is a little off...still...blazing fast...assuming they are short, even using 0-65 mph it's 2.455...handily beating the Veyron.
60-130 time = 6.165 seconds.
1-2 shift time, .195 seconds, 6,564 rpm.
2-3 shift time, .260 seconds, 6,621 rpm.
3-4 shift time, .195 seconds, 6,813 rpm. I wonder if FARTPIPE went clutch in before letting off the gas on 3-4, as you can see the rpm flare up to 6,922 when he was off the gas.
It appears the scanner only reads time in .065 increments...3x.065=.195 so the shifts were likely between .130 seconds and .195 seconds, but below .195 except for the 2-3.
FARTPIPE got about 13 mph wheel spin on the 1-2 shift, 8 mph on the 2-3 shift, and 10 mph on the 3-4. Some ET left on the table there, but I couldn't find any other ET left on the table.
Car was running about 26 degrees timing, IAT at the start of the run was 75, going down to 63 degrees in 4th gear through the end of the run. I'm not familiar if that's the pre-blower IAT or the IAT after compression on the pid that was scanned. My .cfg wouldn't read the knock sensor for some reason but based on the commanded timing line I don't think it had any knock. Interesting that this blown car takes more timing than my N/A car.
FARTPIPE ran it to 6400 in 4th...145 mph....in 10.65 seconds. Feels good to go that fast. I won't type how long it took my car to go 145.
Overall, one of the cleanest runs I've ever reviewed.
Hats off to you FARTPIPE.
11-19-2014, 11:53 AM
#10
Race Director
Ya first day out and he nailed it on the 5 th pass. Is this correct?
Your car seemed not to bog down like the ZR1 out of the hole. Although the last run was minimal. This is where the 4:10s shine.
The only reason I do not track is because I don' t have the $$ for repairs. Or a better way of looking at it is the money is doing something more important.
Nice hobby if you can get it!
Your car seemed not to bog down like the ZR1 out of the hole. Although the last run was minimal. This is where the 4:10s shine.
The only reason I do not track is because I don' t have the $$ for repairs. Or a better way of looking at it is the money is doing something more important.
Nice hobby if you can get it!
11-20-2014, 07:43 PM
#11
Safety Car
something wrong there
I'm running 275/45/17's on C5Z fronts with a stock rev limit. How would I calculate that?
My fastest run was 124.60, also had 124.50, 124.36, 124.28 and 124.22 Those were all 11.4x's
I'm thinking that's it, I wonder what that is costing me in my E.T's since I'm pretty sure it's before I cross the line, every little bit counts
My fastest run was 124.60, also had 124.50, 124.36, 124.28 and 124.22 Those were all 11.4x's
I'm thinking that's it, I wonder what that is costing me in my E.T's since I'm pretty sure it's before I cross the line, every little bit counts
11-21-2014, 03:22 PM
#13
Instructor
Thread Starter
Yup, I ran a couple more 11.4's at the track yesterday but the car tops out at 124 before the finish line. Fastest I went was 124.93. Maybe it's because my Hoosiers are pretty much flat across, no wear lines or anything so they are a bit shorter than they should be. I'm at the stock rev limit so I guess I need to raise it and get new tires. Otherwise I feel like getting 4.10's was a mistake if I'm already maxxed out before a full quarter mile.
Last edited by Vade46; 11-21-2014 at 03:29 PM.
11-21-2014, 03:52 PM
#14
Instructor
Thread Starter
Ambient temps were probably around 45-55 that day. Here are all my 11.4 runs -
These are all my runs from that day in order - Air wasn't as good during the middle of the day
And here's a couple more 11.4's @124 that I ran yesterday, probably around 40-45 degrees -
Last edited by Vade46; 11-21-2014 at 05:30 PM.
11-21-2014, 03:55 PM
#15
Instructor
Thread Starter
Hey Joe G, I don't understand how our MPH's are so different if we pretty much have the same setup. I'm obviously topping out 4th at 124 and I topped out 5th around 175.
, did something break
11-21-2014, 04:02 PM
#17
Instructor
Thread Starter
11-21-2014, 04:19 PM
#18
Race Director
11-21-2014, 07:22 PM
#19
Race Director
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Only thing wrong with what you quoted was that I was running a 275/45 when I'm running 275/40. I made a typo
Ambient temps were probably around 45-55 that day. Here are all my 11.4 runs -
These are all my runs from that day in order - Air wasn't as good during the middle of the day
And here's a couple more 11.4's @124 that I ran yesterday, probably around 40-45 degrees -
Ambient temps were probably around 45-55 that day. Here are all my 11.4 runs -
These are all my runs from that day in order - Air wasn't as good during the middle of the day
And here's a couple more 11.4's @124 that I ran yesterday, probably around 40-45 degrees -
When you say the air wasn't as good in the middle of the day, don't be complaining. Drag Times showed 87' around 2 PM on the 10th. Last night at 8 PM it was -1334'. That's where those high MPH's are coming from. Be sure to bump the rev limiter up when you do the cam this winter. You're going to need the extra RPM.
11-21-2014, 07:45 PM
#20
Race Director
Nice runs. Fairly consistent for the most part too.
When you say the air wasn't as good in the middle of the day, don't be complaining. Drag Times showed 87' around 2 PM on the 10th. Last night at 8 PM it was -1334'. That's where those high MPH's are coming from. Be sure to bump the rev limiter up when you do the cam this winter. You're going to need the extra RPM.
When you say the air wasn't as good in the middle of the day, don't be complaining. Drag Times showed 87' around 2 PM on the 10th. Last night at 8 PM it was -1334'. That's where those high MPH's are coming from. Be sure to bump the rev limiter up when you do the cam this winter. You're going to need the extra RPM.