I notice that the car is well balanced when accelerating hard and usually through 1st and 2nd gear where all the torque is at....but after that, with a flat torque curve, would you still feel that whipping back feeling when accelerating through the gears or having a flat torque curve means that the car is always pulling and never drops out? I'm sorry, I'm not familiar with the whole torque thing....I just know how it feels, but when I downshift to 3rd on the highway I don't really get that accelerating "feel" that really gets the adrenaline rushing...or is it because I need to work on my shifting? Or is it because the torque curve is so flat that the car is pulling without that initial boost?

Thanks for any clarification, I'm not vary savvy on this topic...

 

The VQ engine does have a pretty flat TQ curve, but it's not extremely flat. You can look at the Honda's VTEC I4 engines for real flat TQ curve. It makes about the same TQ +/- 10 ft-lb of TQ @ any given RPM. Since the G TQ start dropping off at around 4-5k rpm, you won't feel the same pull on the high end as you do w/ cars like the S2000. TQ and HP are directly related. Since the TQ drops off on the upper RPM range, the HP doesn't increase as fast as it did in the lower RPM where the TQ is really flat. There's really nothing much you can do to greatly improve your top end unless you go F/I.

 

I think what you are not taking into account is torque multiplication: Each gear has a different ratio at which it multiplies the engine torque. Since 1st gear has the highest gear ratio, it creates the most torque at the wheels. The engine itself produces the same power and torque at a given RPM/throttle input regardless of gear.

 

So basically I shouldn't gauge on how the car accelerates by how I feel, but see how well it goes...I guess I expected too much when downshifting and accelerating to pass, I feel as if it could move much quicker....

 

if you want more top end you should buy a plentium spacer. can anyone tell me what F/I means?

 

F/I = Forced induction (Turbo or supercharger).
I agree, N/A mod will help, but you won't be able to notice it that much from a butt dyno unless you go all out w/ all the NA mods. But by then, it'll cost as much as going F/I.

 

Yeah Stock G's torque in 3-5th is pretty lame, or so in my experence

 

Okay...so I'm not the only one thinking there is a lack of accelerating "feel" between those gears. I wish there was more for such a luxo sport coupe....

 

Sorry...so again, what's the benefit for having a flat torque curve besides having power throughout the RPMs? Is it to keep the car moving strong but not accelerate at any gear strong? Gosh...I wish I knew more about engines

 

Actually, your observation is your answer. Torque, in and of itself doesn't tell us anything. In fact, it is useless. Now torque per unit time, that tells us 100% of the story. Torque per unit time is also known as power. In other words, power moves your car, torque does not.

To clariy, power as a function of engine speed, also known as "power band" is what counts. Chances are when you're downshifting to third on the freeway it's putting you a ways down in the power band. Also, you're up against more wind resistance, so you wouldn't feel the acceleration you do in lower gears.

 

i added a crawford plenum and kinetix high flow cats on my Z, and the car definately pulls harder above 4k rpms! it feels like v-tec on a honda it should feel the same in the Gcoupe, although i don't know about the '05's since they have a different tq curve

 

So it's best to stay in the current power band to keep the car moving? Downshifting and rev matching should take care of that right? Or am I wrong and that it puts me at the new gear's powerband? Gosh...I don't even know what I'm saying, lol...

 

http://www.allpar.com/eek/hp-vs-torque.html

This is about drag racing with a dodge neon (I know I know don't flame yet) but the information this guy has seems very useful. Read it, it may answer many of your questions.

good luck. I am not certifying the truth of the information.

As a side point. This could be why german cars seem faster even with same or less power. Better gear ratio selection to make the best of the power available.

 

Yeah, BMW use really low ratios for the lower gears. The M3 first gear is 15.4:1 vs. G35C at 13.4. That means for the same engine torque the BMW will have 15% more thrust at the road (felt by butt dyno). It helps that they can rev the thing to 8000 rpm, which is the power side of the equation. For reference a Mustang GT uses 12:1, but makes up for it with 320 ft-lbs of torque.

 

Down shifting will always give you better result than staying in the same gear because not only will you put yourself in a higher RPM which usually = more HP, but you'll be in a lower gear which = high TQ multiple. The reason why you feel less pull when down shifting from 6th to 4th gear compare to say 4th to 2nd gear is because you're already going quite fast already, so the change in acceleration is not as noticable compare to lower speed.

TQ and HP is directly related. Here's the equation:
Tq x RPM / 5252 = HP
HP x 5252 / RPM = Tq
So to say TQ in itself doesn't tell us anything is not true. Because when you know TQ at a certain RPM, you'll know the HP.

When people talk about power band, they usually reference it to the HP or TQ curve. Gearing will multiply the amount of TQ output by the engine and put that amount of TQ to the wheel. So downshifting will always yield you a higher multiple = higher amount of TQ to the wheel.
So here's an example with the G35 6MT:
So you're in 6th gear at about 3000 RMP going about 80 MPH.
6th gear has a TQ multiple of 0.794. Lets say @ 3000 RPM, the HP is about 100. So the TQ = 100 x 5252/3000 = 175 ft-lb. But since you're in 6th gear, the amount of TQ at the wheel is really 175 x .794 = 139 ft-lb of TQ or about 80 HP.
If you down shift to 4th, I don't know exactly where the RPM will end up going 80 @ 4th gear but pretend it's @ 4000 RPM, at the point of engagement, you'll have the following TQ and HP:
4th gear has TQ multiple of 1.271. So HP@4000RPM is about 150HP. TQ = 150 x 5252/4000 = 197 ft-lb of TQ. But since you're in 4th gear, the amount of TQ at the wheel is really 197 x 1.271 = 250 ft-lb of TQ which is about 190 HP.
If you down shift to 2nd gear, lets say that's about 6000RPM. @ that RPM, the HP is about 220 HP. So the TQ = 220 x 5252/6000 = 193 ft-lb of TQ. But since you're in 2nd gear and the gear multiple is 2.324, the amount of TQ @ the wheel is really 193 x 2.324 = 448 ft-lb of TQ = about 511 HP.

So as you can see, with butt dyno, you can feel a change from 250 to 448 ft-lb of TQ or 190 HP to 511 HP more than you can from 139 to 250 ft-lb of TQ or 80HP to 190 HP.
I hope that help. I get the HP estimate from this dyno chart and gear ratio from here.