A&Q about 350Z
Q:
Here's a thought. Go outside and time yourself [one way or another] going 40-100mph, once shifting at redline, once shifting at whatever made up point you choose. It doesn't matter, because it will be slower. And before you start loading your artilery, if you are that concerned about where to shift to get the most out of the car, a couple 100mph runs isn't going to kill you [unless you crash]. It's like some of these people have never driven these cars before and are philosophers or something.
19[TT]91
My TT beauty is gone.
2[00]2 Honda 954RR
Suzuki 1200 S; sportscar eater
19[I4]94 Integra GSR Sedan
Long live the Z...
aka SAHTT
A:
Dan is right. You want to go past peak because you are still getting high power output, and then shifting higher into the power band of the next gear.
Shifting at peak really doesn't make any sense.
A:
Dan's analysis is correct, folks. The point is what gear you're going into, and at what rpm's vis a vis maximum power delivered. You want to be going into the next gear accelerating into the peak torque point, not simply approaching the curve. Thus, right at redline is ideal. Keep in mind that the time spent going from the point at maximum torque (usually between 4600 to 5400 rpms) to 6500 rpms is very small, but critical to being at a high enough rpms when upshifting to maximize power to the wheels. Shift at too low an rpm, and you squander valuable milliseconds too far below the maximum torque figure in your next gear.
There is a reason that the gear ratios are what they are - it is to maximize thrust when shifting at redline - and for fuel efficiency at lower throttle levels.
Believe only what you think, not what you feel.
A:
Clownsrus:
>The link posted is good, but I find the writeup that has been on
> twinturbo.net even easier to understand, and has actual formatting,
> showing that someone cares. telling people to shift at redline howerver
> is just plain stupid considering most of the other information is good.
First of all, his charts show that he shifts almost at redline every time (6800-7200 RPM). Second, he claims he is targetting 3500 RPM in the next gear. I disagree, since his torque goes way up at 4500 RPM. Moving closer to redline would get him that extra few hundred RPM.
So Clown, you're basically supporting our argument that redline is the place to shift. Look at your charts closer next time!
A:
DG39 writ:
>Remember the red line is the warning for max revs of the engine. At a certain point in each gear you hit your max torque rev. Anything past that point is wasted power.<
This is untrue. You must rev WELL past peak torque rpm in order to maximize acceleration. Though torque does drop off above peak torque rpm (obviously), it doesn't drop off NEARLY as much as the change in ratios from going up a gear reduces torque TO THE DIFF and TO THE WHEELS!
Torque peak in a 350Z engine is at ~4700 rpm. At this rpm in, say, 2nd gear, you're getting ~235 rw lb-ft, which translates into force accelerating the vehicle thusly:
235 lb-ft * 2.324 (2nd gear ratio) * 3.538 (diff ratio) / 1.11 ft (tire radius) = 1741 lb. acting to accelerate the vehicle.
If you shift into 3rd gear at this point, rpms drop to 3284, engine torque is ~227 lb.-ft, and accelerative force is:
227 lb.-ft * 1.624 * 3.538 / 1.11 ft = 1175 lb.
You've given up 566 lb. of THRUST! If you keep 'er in 2nd gear up to redline of 6500, rear wheel torque drops to 190 lb-ft, but you'll STILL have:
190 lb.-ft * 2.324 * 3.538 / 1.11 ft = 1407 lb. of thrust driving the vehicle!
To maximize acceleration, you ideally would shift far enough above and beyond the POWER peak such that you have the same power in the higher gear as you had in the lower gear. In the 350Z you can't do this because max power rpm is so close to redline. So you just shift at redline.
POWER is more important than TORQUE. POWER translates from torque * rpm / 5252 at the engine to thrust (lb) * road speed (ft/s) /550 at the road. If you want to maximize accelerative thrust at any road speed, you want to maximize engine POWER, not torque. This will dictate higher revs and delaying upshifts allowing you to take advantage of the greater leverage via lower GEARING, vs. shifting at max torque and lugging it against a taller gear.
Final word: Of course in NORMAL driving you won't shift anywhere NEAR redline! Only when you want to MAXIMIZE acceleration would you be revving it that high. No need to in 95% of all street-driving.
Post Edited (Oct 5, 3:08pm)
A:
sorry, i meant to write "snot stock dan" kinda making fun of your attitude. my mistake. to clarify, it is not stock. but i do SHIFT around 4500 Not redline.
Post Edited (Oct 6, 12:35pm)
A:
What mods? Do you have a dyno chart? Unless you have a mondo bizarro torque curve, I would bet money that you'll go quicker shifting at much higher rpm.
edit:
On second thought, forget it. I didn't believe you when you said you ran 12.9 in a stock Z shifting at 4500, so why should I now believe you ran 12.9 in a modded Z shifting at 4500?
Sorry.
Post Edited (Oct 6, 2:01pm)
A:
Dan,
Mr. Danger is jecking your chain all the way around. He isn't a Drag Racer. If he was for real, he wouldn't be talking the way that he is.
Mspeasl
Central Illinois - Form member since 2/02
"Growing old may be mandatory, but growing up is optional"
03 Redline Touring 6sp "350Z" (Pre-Ordered 02/02) - Delivered 29 August 02
05 Satin Jade Pearl Chrysler 300C 6/04
A:
ok i'm not bothering reading all the BS posted here... i got to the dyno chart BTW and was tired of reading... i agree with you guys that say rev past peak torque... i've been road racing quite a bit myself...
approx...2-1/2 years... i admit probably not the smartest thing i've done... but fun regardless...
and i don't consider myself to be a professional... but a rather good driver...
anyways... simply put wouldn't it just make sense to time your shifts to just past the peak torque so that when your engine kicks back into a lower rpm range for the next higher gear that it would land in the most powerful part of the RPM band???
hense the idea of reving past the peak torque... so that youare not wasting time letting your engine struggle through the weaker portions of the band...up to the peak torque again...
so basically i'm saying it's not necessary to redline your car unless that's where youneed to be to hit the next gears peak torque range... otherwise just rev up enough to land yourself in the range...
who agrees?
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Chrome Silver '03 Touring -MT-
C.F. Nismo Wing
Shorty Antenna (Stolen!!! Thanks alot!)
Kicker Solo Baric L7 1200w
I don't think, I know...
Well, I don't think you know either
Post Edited (Oct 7, 1:51pm)
A:
Some other things to consider as well when shifting...
If you drive a turbo sports car that has fuel cut close to/at redline, like an MKIII Supra Turbo, you should shift before hitting it.
You should also shift accordingly so that the next gear lands as close as possible to boost range, so you don't have too much boost lag. As I understand it, this isn't necessary on an automatic since an automatic will hold boost once it is built up.
Dragonball Z
A:
staticivi03
your correct.
different gear ratios, aftermarket turbos, blowers, nos, and alot of other things change the peak torque (lower it by 100's if not thousands of rpm)
hence making the shift points much lower than redline..
NNA runs this site!!!
A:
Guys,
This thread has gone on long enough. You will never convince some folks which is the correct RPM to shift at. The only way is to take both ideas and Drag Race them against each other. Finish lines never lie, they just produce the winner.
Mspeasl
Central Illinois - Form member since 2/02
"Growing old may be mandatory, but growing up is optional"
03 Redline Touring 6sp "350Z" (Pre-Ordered 02/02) - Delivered 29 August 02
05 Satin Jade Pearl Chrysler 300C 6/04
A:
(sorry, I can't stop!)
staticivi03,
For max acceleration you want to rev it WELL past (not "just past") peak torque rpm. You want to shift far enough beyond peak POWER rpm such that when you upshift you're making the same power on the way UP the power curve in the taller gear as you were making on the downside of the power curve in the lower gear. On a 350Z this means shifting at redline is best. Believe it or not, if you have a tranny with close enough ratios, shifting for maximum performance can mean you're above peak engine torque rpm at all times!
Good points on *some* power adders in *some* cases actually reducing peak power rpm. It all depends, FWIW, but what I've seen of some supercharged 350Z power curves, they pretty much peak AT redline! Anyway the above holds true no matter what, i.e. shift WELL above peak torque rpm, and somewhat above peak power rpm.
OK I'm done now (really!).
A:
Dan, your math is right on with the dyno chart. What I found really interesting is the difference in curve between the 350z and the 300zx TT. The takeaway is that not only do you want to shift after peak on the 350z, you REALLY want to hang on to the bitter end with the 300zx and take it right up against redline, because it's pumping out torque the whole way.
Check it out:
Very different engine behavior, so they will require different driving styles.
A:
Dan what i was saying is you really need to know the amount of RPMs your engine will drop when shifting to a taller gear...and go that amount above the peak torque... so you land your next gear in peak torque...
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Chrome Silver '03 Touring -MT-
C.F. Nismo Wing
Shorty Antenna (Stolen!!! Thanks alot!)
Kicker Solo Baric L7 1200w
I don't think, I know...
Well, I don't think you know either
A:
Dan, your math is right on with the dyno chart. What I found really interesting is the difference in curve between the 350z and the 300zx TT. The takeaway is that not only do you want to shift after peak on the 350z, you REALLY want to hang on to the bitter end with the 300zx and take it right up against redline, because it's pumping out torque the whole way.
hmmmmm, differnent torque graphs? hence different shift points? i guess you're not supposed to redline the motor after all??
hhahahahahahahahahahahahahahahahahaha
A:
i know i hate repeating myself but sometimes i have to lay it in simpler terms...
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Chrome Silver '03 Touring -MT-
C.F. Nismo Wing
Shorty Antenna (Stolen!!! Thanks alot!)
Kicker Solo Baric L7 1200w
I don't think, I know...
Well, I don't think you know either