We recently got a 1/4 mile dragstrip and bracket racing here in Swift Current, SK and was thinking of running my Z (a 17 sec. Grand Prix made it to semifinals against bikes and tunnel rammed big blocks
)
With a pretty stock LD9 and 5 speed getrag, what RPM are any of you shifting at and are you varying the shift RPM by gear?
I'd get some practice and see which rpm feels better when shifting.
With my Eco, I shift at 6,000 rpm.
when beating on my LD9, i shift at 6k, theres not much power being made after high 5's anyway.
power quits being made after 5500, but shift as close to the rpm limiter, for when you shift into the next gear, the rpm's fall into your power range.
CrAzY Z24 wrote:power quits being made after 5500, but shift as close to the rpm limiter, for when you shift into the next gear, the rpm's fall into your power range.
Ding Ding!!!
What you have to remember is not only where your power peak is, but what your rev drop between gears is. The absolute optimal shift point is actually most times going to be different for each shift, but generally speaking with the 2.4 and the eco, shift it as high as you can go before you hit the rev limiter.
You want to shift at whatever rpm drops you to the most powerful point in your pwer curve in the next gear. For example, and this is totally off the top of my head so please no pointing out that these aren't the exact numbers for a 2.4: if your power peak is 150 hp at 5800 rpm, after 5800 power will being to drop. Lets say by redline at 6500 rpm its at 140hp. Now, if you shift AT the power peak of 5800 rpm, you could be dropping to an RPM where your engine is only making 130 hp... So you want to shift at redline, because then you will be dropping to an rpm closer to the peak power RPM. Drag racing is all about setting up your engine and gearing, and shift points, so that you are making the most possible power at all times. Naturally traction is a HUGE player but thats not what this post is about.
Anyone shifting an eco or 2.4 lower than redline with stock sized tires and stock gearing is probably not getting the best ET's they could be. Ask anyone in the all motor honor roll in the sticky at the top of this forum, and I'd be willing to bet that they're all shifting right near the rev limiter. I know for a fact that the number 2 and 3 fastest all motor ecotecs do because I race with them frequently.
In the words of the great and powerful Dave Coleman: "the best time to shift is when the power in the next gear will equal the power in the current one. Since this almost never happens, shift at redline."
Arrival Blue 04 LS Sport
Eco
Turbo
Megasquirt
'Nuff said
get some practice in first
Im a Xbox 360 fanboy...and damn proud of it!!
shiftlight comes on at 6000 and the shift happens about 6200.
I used to race cars, now I race myself.
5K PB: 24:50
10K PB: 54:26
Lots of great info, thanks all. My biggest concern now is figuring out what rpm to launch at. My old street tires spun easily, my new Federals don't spin, I get wicked wheel hop instead. Now I've gotta teach that SRT4 a lesson (dial in was 13's).
Here's how I learned...
Wheelspin on launch: Launching at too high of an RPM or giving it too much throttle right away. Much preferred over wheelhop though because it doesn't damage components like hop does and your moving while they spin.
Wheelhop on launch: Launching at too low of an RPM or too much tire pressure. If you hop the tires, launch a few hundred RPM higher and try to create some wheelspin instead or get rid of both all together. Wheelhop causes tons of stress and damage to driveline and suspension components and other parts. I broke a stock upper motor mount IN HALF with massive wheelhop. If it starts hopping try getting off the gas and getting back on. Some cars can be powered through it but if it gets worse GET OFF.
I used to race cars, now I race myself.
5K PB: 24:50
10K PB: 54:26
Oh and with the mods you have listed you won't be teaching that SRT anything. Sorry but it's true.
I used to race cars, now I race myself.
5K PB: 24:50
10K PB: 54:26
I understand I'd suck wastegate fumes running against the SRT4 heads up, but the rusty 92 Grand Prix 4 door beat him when he broke out
Pretty or Ugly, as long as you win!
Actually I wouldn't attempt to race in anything but brackets, "I couldn't AFFORD to go that fast".
In my first post, I basically said Hypsy did this:
Quote:
shiftlight comes on at 6000 and the shift happens about 6200.
But not my car, not my post to make.
This has been answered very well...so I'm thread jacking. What is the point of a redline if you can drive into it, then shift at the limiter?
Say a redline is 6500 rpm, would driving at 6400 rpm for a time damage anything? Still within the manufacturer's said limits. Yes?
Well the redline is 6250. I know where I need to shift to stay in my band from TONS of dyno-testing. I also know how long it takes me to react to my shiftlight from the feedback it gives me after a run. I know that running the car to 6200 is safe and that I won't hit a limiter until 6300 or so so I run it as high as possible to get it back into power as fast as possible.
As long as you don't hang out on the limiter for an extended period of time, running up to it won't hurt anything...just don't go past it too much.
I used to race cars, now I race myself.
5K PB: 24:50
10K PB: 54:26
Quote:
CrAzY Z24
power quits being made after 5500, but shift as close to the rpm limiter, for when you shift into the next gear, the rpm's fall into your power range.
I'm shocked... that someone GETS IT
My hope in humanity is restored
CrAzY Z24 wrote:power quits being made after 5500, but shift as close to the rpm limiter, for when you shift into the next gear, the rpm's fall into your power range.
Do you know this for a fact??? Reason I ask is I have 2 dyno sheets on 2 different year 2.4's. Both were/are mine. Different days different mods. My 97 Z24 pulled max power from about 5400 to 6000, then it dropped a few ponies and then right before the rev limiter it jumps back up. All 3 runs did the same thing. I think the reason for the drop is GM's tuning (from what has been found in HPTuners). My 2001 Z24 gets max power aroun 5100 and holds that pretty steady until about 6100 with a very slight drop. Also the 2001 pulls are more chopy. They were also before my cams, header and exhaust (had just amuffler at that time. My point is every car is different every set-up is different. You will never know where the HP starts and ends unless you have dyno sheets showing it. Heck my dyno sheet is old for my car, I should not be going by this for my car anymore. This still does not change when I shift. I agree with Scarab with stock tuning and rev limiters and stock internally you are going to want to shift as high as you can to keep the RPMs up for the next gear. With HPTuners out and allowing us to change Rev limiters now you are going to have to get some dyno puls and figure out where to shift.
FU Tuning
