Arrvaxx's quest for the 10s.

Arrvaxx · 08-29-2014, 06:58 PM

Yes, massive room for improvement. Which I expected having done this once.

Thanks for all the feedback. Validates my own thoughts on what needs focus. I think this Wednesday night I will try a few things including shifting in to second earlier. I think I might try shifting before recline. If I remember correctly my hp peaks at 6800 or 7000.

*Edit: Using the 91 octane tune numbers.*

- So my torque ramps fast and starts its gradual decline at 3500rpms.
- Torque and HP cross at 5250rpms.
- From 5500rpms to peak HP at 7250rpms the HP difference is only 10%. By redline I've lost that 10% and am back down to 5500rpm HP.

My thoughts on what this tells me...looking for validation or correction:

- If I launch at 3000rpms my torque is a full 100lbs less than 3500rpms. Launching at 3000rpms vs 3500rpms should help to keep the spin down. ?
- I should shift from 1st to 2nd at 5250rpms. Landing in 2nd should put me at peak torque. If the R-S3s are warm I won't spin in second.
- I should shift from 2nd to 3rd at 6500rpms which will land me at 5250rpms...right when HP overtakes torque.

Finally...4th. As I mentioned on Wednesday I ended the 1/4 mile just a tick shy of redline. I'm 'thinking' that I should shift from 4th to 5th at 7000rpms. At 7250 it drops like a stone so I think it would be better to shift earlier than later or risk the chance of shifting too late. I might even do it at 6500. But the car pulls sooooo hard in 4th it is hard to not let it have every moment it can there. But it has to be better to get the car in 5th sooner than shift 10' from the end or even worse hit the limiter and watch it suck out the power.

Japanjay · 08-29-2014, 08:04 PM

Do you load up the suspension at all before the tree drops?

phunk · 08-29-2014, 08:48 PM

Quote:

Originally Posted by Arrvaxx

My thoughts on what this tells me...looking for validation or correction:

- If I launch at 3000rpms my torque is a full 100lbs less than 3500rpms. Launching at 3000rpms vs 3500rpms should help to keep the spin down. ?
- I should shift from 1st to 2nd at 5250rpms. Landing in 2nd should put me at peak torque. If the R-S3s are warm I won't spin in second.
- I should shift from 2nd to 3rd at 6500rpms which will land me at 5250rpms...right when HP overtakes torque.

If you are not spinning top of second or into third, then you want to take second gear all the way to redline. Dyno graphs are a little misleading... see, even though we call that graph "rear wheel power", it is NOT rear wheel power. That graph is ENGINE power as measured at the rear wheels. So it does not take into account gearing. It only takes into account drivetrain loss.

With the 370z stock final drive and transmission gears, first gears absolute ratio is 14.00. Second gears absolute ratio is 8.58, and third is 5.99.

Reference your dyno chart at any RPM you wish. Take the number either HP or TQ and multiply it by your absolute gear ratio. THAT is your power to the axles. When you do the math, you will find numbers that are insanely high in low gears. YUP! Imagine what 100fb lb of torque feels like when you tighten a lug nut with a torque wrench, and then try to imagine that amount of torque powering a honda civic to 14 second 1/4 miles... Then it will start to make sense. 100ft lb can only do that after its multiplied several times through gearing.

This is why, unless you are spinning the tires, you keep the car in the lower gear AS LONG AS YOU CAN!!! Power applied to the wheels in second gear is nearly cut in half from first gear. You loose like 25% from second to third, not as bad, but obviously very significant.

Arrvaxx · 08-29-2014, 08:51 PM

Quote:

Originally Posted by phunk

If you are not spinning top of second or into third, then you want to take second gear all the way to redline. Dyno graphs are a little misleading... see, even though we call that graph "rear wheel power", it is NOT rear wheel power. That graph is ENGINE power as measured at the rear wheels. So it does not take into account gearing. It only takes into account drivetrain loss.

With the 370z stock final drive and transmission gears, first gears absolute ratio is 14.00. Second gears absolute ratio is 8.58, and third is 5.99.

Reference your dyno chart at any RPM you wish. Take the number either HP or TQ and multiply it by your absolute gear ratio. THAT is your rear wheel numbers. When you do the math, you will find numbers that are insanely high in low gears. YUP! Imagine what 100fb lb of torque feels like when you tighten a lug nut with a torque wrench, and then try to imagine that amount of torque powering a honda civic to 14 second 1/4 miles... Then it will start to make sense.

This is why, unless you are spinning the tires, you keep the car in the lower gear AS LONG AS YOU CAN!!! Power applied to the wheels in second gear is nearly cut in half from first gear. You loose like 25% from second to third, not as bad, but obviously very significant.

Interesting. Thanks!

phunk · 08-29-2014, 08:56 PM

If you want to do the supreme calculations to figure out how to drive your car on paper, input your dyno graphs and gearing into a spreadsheet and make yourself a graph like this one. This graph reflects torque to the axles in an ITR for each gear comparing 3 different final drive options.

Build a graph like this, and you can figure out when its best to shift, which will almost always be redline.

Another thing you can TRY and do but its really sloppy, is estimate roughly how much torque it seems like your tires can take before they let go, and try and stay under that but close to it as possible. Tons of error in there though as so many things will cause the tires traction limit to fluctuate heavily on a street car. It can get closer though if you work at doing things consistently as far as tire pressure and temps and application of clutch.

Arrvaxx · 08-29-2014, 09:01 PM

Haha. Maybe when I am trying to break in to the 9s.

phunk · 08-29-2014, 09:04 PM

LOL its not really required for selecting shift points anyway, its more for deciding on gearing changes. You can see for yourself on that ITR graph that there is never any point on the graph where the next gear up was able to get more power to the axles than the gear before it. So you shift at redline for best acceleration.

You can also notice that the transmission gearing was intended so that if you shift at redline, you are landing in the peak of the next gear. To shift any earlier would cost major power... so you only do that if you cant use the power anyway.

Mitco39 · 08-30-2014, 01:00 AM

This might help you out, made it awhile back just for fun.

** Mitco's Acceleration and Gearing Spreadsheet

Arrvaxx · 09-07-2014, 08:46 PM

Just got back from my second ever drag night. I am very pleased.

I shaved .8 seconds off my best run on my first night (down to 12.47 @ 117.62 mph). I was going to credit all of the improvement to it being slightly better turbo weather but then I looked at my slip. My 60' was .3 seconds faster and my 330' was .5 seconds faster. So I am claiming .4 seconds of the improvement for myself and better launches. The other .4 can be claimed by my lovely, lovely turbo twins.

1cleanZ · 09-07-2014, 11:04 PM

Quote:

Originally Posted by phunk

Generally, you always shift as late as you can due to torque multiplication. But when you have a scenario where gear A or gear B will BOTH just light up the tires anyway.... well in that case it makes no difference aside from what is easier to drive... and that will be the taller gear. If you still cant go full throttle in second anyway, then I would experiment with early shifting and seeing if you can do it without the car landing too low in the powerband in second. Otherwise, always shift as late as you can.

One thing I have noticed about my car, it doesnt like to shift while the wheels are spinning. I havent really sat down to think about that one... but I have observed that if I am in first gear banging the rev limiter from tire spin, its not going to let me into second (nasty grind) unless I let off for a moment. I assume the tires and drivetrain need to decelerate down for everything to be happy and allow the shift, just havent really thought about it yet.

Quote:

Originally Posted by GaleForce

I have the same issue. I try to get out of first as fast as I can with reasonable throttle input, then mash *within reason* the right pedal from 2nd, on.

I've had this EXACT issue both on the drag strip, as well as the road course. 2 gears inparticular stick out to me, 3rd and 5th. I remember being on the straight stretch 4 laps in a row, and the car literally would NOT LET ME PUT IT INTO 5TH?? I was like, wtf, there is NO WAY that I simply cannot find the gear??? Then I realized when I lifted completely off the accelerator early and shifted early with no redline, it allowed it to go in.

This past weekend, I had the same issue going into 3rd, causing me to shift early and actually held the clutch in early, delayed, and then shifted just to make sure I could get a run in without the car refusing me to get it into 3rd.

THEN, of course the fuel starvation. Have had this on the road course, saying I had over a half tank, yet completely shut the car off in the middle of accelerating on the straight. Wouldn't start back up, disconnected the battery hoping it wasn't something electrical. Sure enough, once I reconnected, the fuel meters/lights were completely empty. Have also ran out of fuel/cut off during auto-x events and exit ramps on the way to events.

uggggh, the struggles of the 370, yet I still love this damn thing and can't get enough of ittttt!!!

Kojack · 09-14-2014, 09:51 PM

Arrvaxx: Quick question... on the last pass, you was running at 492hp?

Super Werty · 09-15-2014, 12:06 AM

Quote:

Originally Posted by Kojack

Arrvaxx: Quick question... on the last pass, you was running at 492hp?

His car is probably making less power . Only reason I say this is because 492 hp was basically at sea level(tuned in California I'm assuming) and that track was at 1200 ft. above sea level.

Explains why he wasn't able to trap in the 120's. If he wants to break into the 10's, moving down in elevation may be one of the things he has to do to get there.

Arrvaxx · 09-22-2014, 03:17 PM

Quote:

Originally Posted by Super Werty

His car is probably making less power . Only reason I say this is because 492 hp was basically at sea level(tuned in California I'm assuming) and that track was at 1200 ft. above sea level.

Explains why he wasn't able to trap in the 120's. If he wants to break into the 10's, moving down in elevation may be one of the things he has to do to get there.

Is it that high? I had no idea. Good to know, thanks.

FPenvy · 09-22-2014, 03:24 PM

Quote:

Originally Posted by Arrvaxx

Is it that high? I had no idea. Good to know, thanks.

head out to the east coast.

got my best ET's in MD.

Hotrodz · 09-23-2014, 09:51 PM

I don't know how linear the power loss is as you climb from sea level to whatever elevation, but I'm at 3,500' and if I come down the hill to 1,200', there is a significant difference in the performance. I'm also guessing the car will run a little richer at elevation as well.

It's most noticeable in launching the car....

08-29-2014, 06:58 PM	#16 (permalink)
Arrvaxx A True Z Fanatic Join Date: Jul 2013 Location: Whore Island, MN Posts: 1,243 Drives: 40th F.I. Twin Turbo Rep Power: 18	Yes, massive room for improvement. Which I expected having done this once. Thanks for all the feedback. Validates my own thoughts on what needs focus. I think this Wednesday night I will try a few things including shifting in to second earlier. I think I might try shifting before recline. If I remember correctly my hp peaks at 6800 or 7000. Edit: Using the 91 octane tune numbers. - So my torque ramps fast and starts its gradual decline at 3500rpms. - Torque and HP cross at 5250rpms. - From 5500rpms to peak HP at 7250rpms the HP difference is only 10%. By redline I've lost that 10% and am back down to 5500rpm HP. My thoughts on what this tells me...looking for validation or correction: - If I launch at 3000rpms my torque is a full 100lbs less than 3500rpms. Launching at 3000rpms vs 3500rpms should help to keep the spin down. ? - I should shift from 1st to 2nd at 5250rpms. Landing in 2nd should put me at peak torque. If the R-S3s are warm I won't spin in second. - I should shift from 2nd to 3rd at 6500rpms which will land me at 5250rpms...right when HP overtakes torque. Finally...4th. As I mentioned on Wednesday I ended the 1/4 mile just a tick shy of redline. I'm 'thinking' that I should shift from 4th to 5th at 7000rpms. At 7250 it drops like a stone so I think it would be better to shift earlier than later or risk the chance of shifting too late. I might even do it at 6500. But the car pulls sooooo hard in 4th it is hard to not let it have every moment it can there. But it has to be better to get the car in 5th sooner than shift 10' from the end or even worse hit the limiter and watch it suck out the power. __________________ 2010 370Z 40th Anniversary (#480 born 1/19/2010) Fast Intentions Twin Turbo \| Varis Arising II \| Limited Edition Recaro Sportster \| Tuned by Specialty Z \| 604hp 525 torque @14lbs boost on 100 octane Last edited by Arrvaxx; 08-29-2014 at 08:08 PM.

08-29-2014, 08:56 PM	#20 (permalink)
phunk A True Z Fanatic Join Date: Mar 2009 Location: Chicago Posts: 3,668 Drives: 370 Rep Power: 974723	If you want to do the supreme calculations to figure out how to drive your car on paper, input your dyno graphs and gearing into a spreadsheet and make yourself a graph like this one. This graph reflects torque to the axles in an ITR for each gear comparing 3 different final drive options. Build a graph like this, and you can figure out when its best to shift, which will almost always be redline. Another thing you can TRY and do but its really sloppy, is estimate roughly how much torque it seems like your tires can take before they let go, and try and stay under that but close to it as possible. Tons of error in there though as so many things will cause the tires traction limit to fluctuate heavily on a street car. It can get closer though if you work at doing things consistently as far as tire pressure and temps and application of clutch. __________________ Charles @ CJ Motorsports : Website \| Facebook \| Instagram \| YouTube Home of the 9 second, stock longblock, stock drivetrain 6MT 370z. 9.91 @ 142mph

08-29-2014, 09:01 PM	#21 (permalink)
Arrvaxx A True Z Fanatic Join Date: Jul 2013 Location: Whore Island, MN Posts: 1,243 Drives: 40th F.I. Twin Turbo Rep Power: 18	Haha. Maybe when I am trying to break in to the 9s. __________________ 2010 370Z 40th Anniversary (#480 born 1/19/2010) Fast Intentions Twin Turbo \| Varis Arising II \| Limited Edition Recaro Sportster \| Tuned by Specialty Z \| 604hp 525 torque @14lbs boost on 100 octane

08-29-2014, 09:04 PM	#22 (permalink)
phunk A True Z Fanatic Join Date: Mar 2009 Location: Chicago Posts: 3,668 Drives: 370 Rep Power: 974723	LOL its not really required for selecting shift points anyway, its more for deciding on gearing changes. You can see for yourself on that ITR graph that there is never any point on the graph where the next gear up was able to get more power to the axles than the gear before it. So you shift at redline for best acceleration. You can also notice that the transmission gearing was intended so that if you shift at redline, you are landing in the peak of the next gear. To shift any earlier would cost major power... so you only do that if you cant use the power anyway. GaleForce likes this. __________________ Charles @ CJ Motorsports : Website \| Facebook \| Instagram \| YouTube Home of the 9 second, stock longblock, stock drivetrain 6MT 370z. 9.91 @ 142mph

08-30-2014, 01:00 AM	#23 (permalink)
Mitco39 A True Z Fanatic Join Date: Aug 2012 Location: Edmonton Alberta Canada Posts: 2,089 Drives: 40th 370z Rep Power: 132	This might help you out, made it awhile back just for fun. ** Mitco's Acceleration and Gearing Spreadsheet __________________ 2007 Chevy Duramax - EFILive Tuned By Me 2010 40th W/ Nav - Boosted Performance - UpRev Tuned By Me The Mrs. Ride -2012 335XI N55 BMW - Cobb Tuned By Me, Built by her My Build --> http://www.the370z.com/members-370z-...39s-build.html

08-29-2014, 08:04 PM	#17 (permalink)
Japanjay Track Member Join Date: Mar 2012 Location: Puyallup Posts: 856 Drives: 09 Nissan 370z MB M6 Rep Power: 14	Do you load up the suspension at all before the tree drops?

09-14-2014, 09:51 PM	#26 (permalink)
Kojack Base Member Join Date: Oct 2012 Location: USA Posts: 144 Drives: G37s Rep Power: 13	Arrvaxx: Quick question... on the last pass, you was running at 492hp?

09-23-2014, 09:51 PM	#30 (permalink)
Hotrodz A True Z Fanatic Join Date: Aug 2012 Location: NW, AZ Posts: 9,330 Drives: 10 Nissan 370z Nismo Rep Power: 2684385	I don't know how linear the power loss is as you climb from sea level to whatever elevation, but I'm at 3,500' and if I come down the hill to 1,200', there is a significant difference in the performance. I'm also guessing the car will run a little richer at elevation as well. It's most noticeable in launching the car.... __________________ *Fast Intentions TT Installed and Tuned by Seb at SpecialtyZ 610whp 560tq:\|Fast Intentions 3" TT-TDX*\|SpecialtyZ/Fast Intentions 72 Row Oil Cooler\|SZ 6 Puck Clutch & Flywheel\|3GsCustoms\|Z1\|Wavetrac\|Hotchkis\|Whiteline \|Blitz\|Fortune Auto 500\|Fujimura\|SPL\|H&R\|TK\|TWM\|RPM Rollbar\|Sparco\|Next Level Performance\|TrackSpec\|AeroFlow Dynamics\|Pioneer\|

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