soloist3

Quick question, I own an IS350 and it is pretty damn quick, however, driving around a friend's SC400 (1998 model) I noticed it "felt" significantly faster according to my seat of pants dyno.

I am always curious about this phenomenon as the SC is definitely not technically as fast as my IS350, though it almost doesn't matter b/c the SC seems to feel faster. I always think of acceleration in terms of the magnitude of g-forces produced, but in some odd way it seems that even slower vehicles, with larger displacement engines tend to always feel faster. I realize this is just a perceptual fallacy, however it bothers me as if I was driving around both cars, having no knowledge of how statistically quick the IS350 is I would never pick the IS350 as the quicker vehicle. I suppose what I am getting at is I am looking for not only the statistically quick car but something that feels quick as well, I wonder if I would be better off with something like an SC400 or perhaps putting in some money towards an ISF.

Also, I know all about how torque and horsepower correlate, that is not what this is about, I guess I am just sort of curious what you all think, also, to ISF owners that moved up from the IS350, do you feel that you got that "feeling" of fast from the larger displacement?

Tro209

The reason the SC400 is because it has 300lb ft of torque. Also at a slightly lower rpm range I believe. The IS350 only makes 277 lb ft of torque at im guessing a higher range. But the IS350 definitely has more of a pull feeling while the SC400 has a more push feeling. Thats how I view Hp vs Torque anyway... Shoot a 99-04 mustang gt has about 300 lb ft torque and "feels" faster too but it aint keeping up with us lol. My brother had one and I beat it pretty good. Sure the beginning push from the torque made the car feel faster at first but up top my car feels faster and is faster. Thars where horsepower kicks in.. oh and short gears lol.

Anyway dont leave your IS for an SC400. The sc400 is a pretty big car with a rather small interior. Not trying to diss the SC or anything but if your gonna trade, at least trade up and get an ISF.

J2X

all you feel is torque

by that i mean, in a given gear, g's of acceleration - what you feel - correspond directly with torque. ie while in the same gear, if you double the torque at any given point, the g will also double

hp is simply a mathematical expression of what rpm the torque is applied. ie in a hypothetical motor, x amount of torque at 3000rpm and the same x amount of torque at 6000rpm will result in double the hp at 6000rpm, even though the torque is the same. leaving aside external confounding factors like aerodynamic drag, the acceleration g will be the same at both points

Icy350

iTrader: (18)

I would agree with everyone above, You are honestly just feeling the torque. I sat in my friends 2015 C300, according to the specs, it has 273 lbs of torque at 1.3k Rpm. compared to us which have 277lbs of torque at 4.8k RPM. The c300 launch makes my car feel ridiculously slow, but I know once we past 1st gear my car walks him no problem.

soloist3

Yep, and that's what I was thinking, the torque at lower RPM's due to displacement. Yesterday I did get on the IS350 and it was pretty scary, first time I have ever been slightly surprised by acceleration in a car, but it really has to be at that "sweet spot" in the RPM range and at a certain speed, as the lack of torque over the V8's is definitely noticeable around town, just moving through traffic.

I have been on the fence about going to an F as it is literally the same car I already love but with a V8 that almost certainly has to feel quicker, not to mention IS quicker. The idea behind the SC is to keep the IS350 AND have something with some significant torque that is a little cheaper that also permits me the ability to split the miles on my IS350; I drive 31 miles to work one way and the miles are starting to add up on the IS350.

I have been saving for a house as of late, it has been taking me forever but I have 20k to spend, part of me wants to just get the ISF and stay in a rental for a little while longer but this house buying prospect is always in the back of my mind

Gville350

iTrader: (10)

Take both cars to a drag strip and see what the results are after driving both.

redspencer

iTrader: (1)

Here are the HP and Torque graphs for both the 1UZ-FE w/ VVTi and the 2GR-FSE to visually compare the available torque at 2k, 4k, etc...

1UZ-FE w/VVTI from the 98 LS400 (same revised motor)-


2GR-FSE-

Nochi20

so happy i just joined club lexus!!! learning something new all the time!! *taking notes*

J2X

i should add that its not as simple as just comparing torque figures between cars...they will have different gearing which will affect acceleration, not to mention weight

when you add the factor of gearing, then rpm becomes involved. and once rpm is involved, then its about power

a car's overall accelerative capability comes down to power to weight. however - how well it can exploit this capability comes down to the car's gearing.

to illustrate this, some of you may have cars with constantly variable transmissions (cvt). a cvt is pretty close to the ideal theoretical solution - the reason they are often found in hybrids which are aiming to extract every last % of efficiency.. in this case, optimal acceleration will take place when rpm is at peak hp.

on the other hand, in a fixed gear vehicle, the optimal momentary acceleration takes place - within each gear - at peak torque. however as it accelerates, the car obviously doesnt stay at that rpm, it moves up. by definition, torque falls off as it passes the point of peak torque. this is due to volumetric (breathing) efficiency and various factors inherent to the engine. so where we have a conventional manual transmission where we must shift between several fixed gear ratios, optimal average acceleration takes place between peak torque and peak hp - and peak hp represents the point at which the torque is providing the most benefit, or doing the most work. and the units of work? they are things like kW and horsepower