Sure,

You didn't use the word "need", but it's clearly implied. You didn't add a post script noting it might be done with some other variable change...
If you call my argument speculation as well, I see your point... but I'm not throwing out numbers that I think are accurate. Instead, I'm trying to filter through the BS to see what's realistic. So you're right, it is speculation to an extent. Your claim might be realistic - - only time will tell. Not sure why you are so defensive. My first post just asked WHY because that seemed like too high of a launch to me. But if you want to get defensive, go for it.

 

I too am more concerned with 5-60.
But it so happens that's even harder to speculate on.
I know it comes from trial and error. Every car is different. There is no set "most power = best launch". Too many factors included.

I agree with all of your points. Typically you want to get to maximum torque ASAP, but other than that it's all trial and error. That's why high launches are required to get a good time for an S2000 which makes its maximum torque at around 7K rpm. Ambient temperature, humidity, track conditions, elevation, tire traction, and last but not least driver skill have an affect on 1/4 mile time.

I don't take these speculations too seriously. We are all guessing, and it will be interesting to see who comes closest to actual times. Based on history with times being all over the place, we will probably all be able to find some magazine that will get a time within a tenth of second of what we predicted.

 

Fast1 - But maximum torque ASAP is only good if it doesn't trail off right away. Im not saying either the 335i or the 7 does this, just saying it's something to consider when trying to formulate. But I think we're on the same pages.

 

True and that takes us back to the trial and error method that we discussed earlier. A torque curve can guide you, but you never know for sure until you track your car. One thing that I think we all agree on is that the G37 has a lot of promise.

 

Here's a question: why would one want to launch at peak torque versus peak horsepower? (can of worms)

 

I would assume it's a 2 part answer:
HP is a function of TQ.
TQ is best to move weight, vs sustaining it. So when you are fighting inertia at the start, you want as much TQ is possible to get off the line (compared to the momentum when you are already moving).

Probably wrong, though.

 

A car's maximum acceleation occurs when it hits its maximum torque, and because of the effects of gearing your maximum acceleration will occur in first gear. It's that simple. On some cars that reach maximum torque at 3500 rpm or less, HP by definition will be relatively low: HP = Torque X RPM / 5252. If a car made its maximum torque of 270 lb/ft at 3500 rpm, the HP at that point would only be 180. On the other hand if the torque fell down to 225 at 7000 rpm, HP at that point would be 300.

So you hit your maximum rate of acceleration at 3500 rpm and depending upon the torque curve for that engine you may maintain maximum acceleration for another 2K rpm, but after that point in time your rate of acceleration actually begins to decline. You still are accelerating but not as fast as at lower rpms.

 

I would think one would want to launch at the greatest possible horsepower, not torque. Here's an interesting take on the topic:

https://g35driver.com/forums/showpos...&postcount=105

 

There are several fallacies in that post. I'll pick just one:When given the signal to floor it, the G @ 6700 is going to easily out pace the other @ 4900 rpm. So what happened there? Last time I checked a 38 ft-lbs torque deficit was no laughing matter

Of course a G at 6700 rpm will easily outpace one at 4900 rpm. Why? Because it's travelling at a higher speed at the higher rpm, but if the torque at 4900 is higher than at 6700 rpm, the rate of acceleration will definately be faster at the lower rpm.

But if you believe what is in the referenced post, I agree with you that you would shift at the highest HP and not Torque. BTW there are lots of valid reasons that have been posted by others in this thread as to why shifting at high rpms can be counterproductive.

IMO both HP and torque are important. If you have the extremes, i.e., low HP/high torque or high HP/low torque, you wouldn't have a fast street car. In the first case you would have a truck engine. In the second case try to imagine a 1.6 liter engine that made 400 HP at 11K rpm and had a maximum torque of 150 lb/ft. Does anyone really believe that engine could propel a 3600 lb G37 to a quick 0/60 time?

 

My peak torque is roughly 4500 rpms. My peak horsepower is roughly 6300 rpms. If traction is not an issue, I will cut much better 60' times if I launch at ~6grand than if I launch in the mid 4's.

That is a fact. In fact, with my DR's, I would dead-hook at 4.5k. At 6k, I spin for the first 30 feet.

At 4500rpms, I'm putting down 220hp/250tq. At 6 grand, I'm putting down 265hp/235tq.

If you want to see some of my dyno plots, view this thread: https://g35driver.com/forums/reviews/143552-final-numbers-revup-bolt-ons-utec.html

That thread happens to be a summary review after my mods and ecu+tune. In that thread I also touch on shift points, inasmuch as they relate to the gains in each gear I netted from the utec.

 

gimme trq FTW!!!!

 

My peak torque is roughly 4500 rpms. My peak horsepower is roughly 6300 rpms. If traction is not an issue, I will cut much better 60' times if I launch at ~6grand than if I launch in the mid 4's.

I don't doubt that what you post is true, but think about what you are posting. What is your speed at 6300 rpms? You don't honestly think that you go from 0 to 40 MPH+ in less than a second do you? A 6300 rpm launch will cause your wheels to spin like crazy until get control by modulating your clutch release and gas pedal pressure. So once you get your tires to bite you are probably at a higher rpm with a 6300 rpm launch then with a 4500 rpm launch, but there's mo way that you are at 6300 rpm at that point.

As we posted earlier it's all about trial and error to get your best times, but not too many of us would be willing to abuse our cars with 6300 rpm launches to cut a tenth of a second from our 1/4 time. BTW high rpm launches are especially bad for AWD cars unless you like replacing your clutch on a monthly basis.

 

13.3

 

Oh snap! Was I the closest?!

Source: http://www.caranddriver.com/shortroa...wer-page2.html

 

What some other members are saying: