carderoni

It's been a little while since my last post and, with the weather warming up, I've had a chance to put a few more miles on the RWD car (now clocking in just over 2,300) and put it through its paces a bit.

Transmission (under normal driving conditions)
A couple things here have become more apparent over time. First - and this was a surprise to me - the 8 speed transmission will NOT shift beyond 5th gear when in Sport or Sport+ mode unless you are in manual mode. Pulling on the upshift paddle while in automatic mode won't even force it into 6th, 7th, or 8th gears. This is kind of an annoyance coming from the AWD car, which will shift through all its gears automatically. I really enjoyed cruising around in automatic Sport/Sport+ mode which isn't very feasible in the RWD car which, at 50MPH, has the engine spinning at around 3,000RPM in 5th gear. In a driving environment where you can hop between low speed residential areas and high speed beltways/expressways, this is a problem.

Because of this I've found myself operating the car in manual mode far more often than I did in the AWD car. The shifts are definitely quicker and crisper with the 8 speed transmission. It's not a huge, in your face difference but something that has become more obvious as I've spent more time shifting on my own.

Fuel Efficiency
After 5,000 miles the AWD car was averaging 20.9MPG in about a 60/40 city/highway split, most of it spent driving very casually. So far the RWD car has topped this number by exactly 1MPG, for an average of 21.9MPG under the same city/highway splits and along the same routes. What makes this more impressive is the fact that, due to the 8 speed requiring you to shift manually if you want to hit gears 6, 7, and 8 while in Sport/Sport+ mode, I've found myself driving the RWD car in Sport/Sport+ mode more often and more aggressively in general. I could probably be in the mid-upper 22MPG neighborhood if I drove this car more moderately.

Around the Bends
This is where the differences between the two cars really stand out. I'm not sure if the traction control software in the RWD car is more aggressive or simply required to keep the car straight under the same conditions, but almost any loose sand or dirt under the tires will set it off. Thankfully this is easily defeatable and you can push the rear end around when you really want to. The car doesn't have so much torque that every hairpin's an adventure, rather it's very controllable and predictable.

The AWD IS 350 is a very point-and-go car but with some noticeable understeer when pushed to the limits. The RWD car does understeer a little bit, but it doesn't tend to plow face first into turns like an Audi S4 or the newer BMW 335's. The 8 speed gearbox does keep you in the engine's sweet spot - above 4K RPM - more often if you shift at just the right times. This transmission will shift right at or a hair before red line, even if you're in manual mode, where the 6 speed will actually let you cross into the red for a split second. With gears spaced so closely on the 8 speed, downshifting will sometimes result in an annoying beep that indicates "you can't do that yet, slow down". This is more nannying than I expected from a transmission built for the IS-F, something the 6 speed doesn't exhibit (unless you're really being careless), but something you can learn around. The 8 speed doesn't allow as much room for error if you want to stay in the ideal gear, but it is possible if you're on your toes and get to know all the little auditory and tactile cues that help you know when to shift.

And, of course, the tires make a big difference here as well. The summer rubber that comes with the RWD car, while not the best on the market, provides quite a bit more grip on dry pavement than the all season tires on the AWD car. Getting the all seasons to bark at sideways trajectories is easier - and scarier. Like most AWD cars you tend to have outstanding grip until you don't. Where the RWD car predictably and gradually lets loose - and lets you recover the rear end - the AWD car will let you point and go and, at some point at absurd speeds, abruptly let go. This is just how AWD cars tend to behave, in my experience, whether we're talking about a WRX or a Gallardo.

...

All that said, I still find myself enjoying the RWD car a bit more on a day to day basis. I've said it before, but the shorter first gear makes a very noticeable improvement in throttle response off the line, helping the car feel torquier than it really is. Rain and cold weather (sub 40 degrees) haven't posed a problem, though when snow hit the ground I opted for an AWD vehicle. Both the AWD and RWD cars have been great daily drivers and weekend warriors, with each having its own set of pros, cons, and quirks.

CTLG

It's important to note that on the 8-speed RWD model, if you've fully turned Traction Control off (by pressing and holding the TRAC button on the center console for 3 secs when the car is not moving), the 8-Speed will allow you to bounce off the rev-limiter until your heart's content. Although, It still won't allow you to downshift to the next lower gear if you're going too fast so you don't over-rev the engine.

05RollaXRS

Since AWD does not come with VGRS and your F-Sport came with VGRS.

What are the differences you noticed in terms of steering precision, response and feedback with VGRS in your RWD car?

carderoni

Good point made by CTLG that I forgot to mention - in both cars you can either tone the nannies down or completely defeat them. This is the difference between hitting the Trac OFF button and holding it down.

05RollaXRS, I did not get VGRS on the RWD car, so I can't comment on that. VGRS is an option, not standard equipment.

05RollaXRS

I see. Thanks. I believe, in Canada it is a standard part of both F-Sport packages for the RWD model only. That is why I thought it must have come with it. Anyway, thanks.

WiLz

The 8 speed actually does automatically shift beyond 5th gear in Sport/Sport+, if it is beyond a certain speed, and under light throttle. I haven't been able to figure out exactly when or how to get it to upshift, but I've seen it do it every so often. For me, it usually goes into 6th gear fairly easily on the freeway, but it will only shift into 7th above 70MPH (with light throttle). I've seen it shift into 8th twice, but only when my wife was driving; I've never gotten it to shift into 8th automatically myself.

I suspect maybe it takes into account how aggressive you drive it, and if the car thinks you are driving aggressively, it locks out the top gears, and when it thinks you are just cruising, it allows the top gears.

Ratedg

interesting.. thanks for sharing yo!

Aeromotive

Thanks carderoni! Another interesting read.

In one of your previous posts you mentioned the 8-speed had a shorter click to shift delay, but the shifting itself wasn't quicker than the 6-speed. Are you still under the same impression?

This issue has been bugging me. While I don't street race, I like to push the car from time to time, especially on highway ramps. However I'm worried a slight imperfection in the road (eg. joints or connecting points on elevated highways) might send the back sliding in a dangerous, uncontrollable oversteer. Have you ever felt in danger? Or is traction control always enough to save your butt? I have never owned or driven a RWD car on a long term basis (only for short drives)...

Thanks again. My RWD IS350 is due in 4 weeks!

Slust

Like the update! Though a couple things should be pointed out.

The 8-speed does auto-shift past 5th gear in Sport/Sport+ mode.
- 67mph = 7th gear
- 84mph = 8th gear

I forget the speed it shifts into 6th gear because the freeway speed limit here is 65mph and 75mph on the open highway so I'm either driving city street speed or 75+.

Gas mileage is most definitely improving as the car gains more mileage. I was averaging 22-23. Now I'm at 24mpg ...and that is with a few spirited romps (0-60 WOTs and 75 to 95 romps to lose tailgaters).

In addition to what was said by CTLG (trac off) I have been able to cross in the redline both in manual mode and even in auto mode ...with traction control on. It's not reliable but it is doable. If you want reliable, CTLG's advice is the way to go.


You would really have to do something stupid to lose the rear end in this car ...or be driving in a an environment that would be horrible for any car to keep good traction (loose gravel everywhere, thin snow (as opposed to thick snow which actually provides more traction) or slick roads). Nothing is impossible but smart driving and good conditions always prevail.

carderoni

Interesting - the first few times I tried cruising around in Sport mode the car was maintaining 3,000RPM for a solid minute while I was at 50MPH+ so I assumed it would just never shift. I couldn't even force it to shift unless I dropped it into complete manual mode. I'll have to give this another shot and see if I can narrow down what conditions are required for it to shift and how easy it is to hit them.

I haven't been able to cross into red line, or did not see it happen, but I'll give it another shot next time I get a track day. I've only had one good opportunity to really wring it out so far. I wonder if the shifts just snuck up since there are so many gears so close together? I've never had a car with more than 6 to row through.

As for the traction questions I agree with Slust, you'd have to do something really stupid to completely lose the rear end when traction control is on, like gun it on a wet highway ramp in a low gear. I've noticed the traction control kicking in on the RWD car a lot more than the AWD car but it keeps the rear end stable every time.

I might've done a poor job explaining it in a previous post, but the response time from when you pull the paddle to when the car begins to shift feels pretty identical with both transmissions. I think I was referring to this as shift response, or something similar. The time from the beginning of the shift to the end of the shift is definitely quicker in the 8 speed, which is what I think I was referring to as shift time. So, overall, the time from paddle pull to a completed shift is shorter with the 8 speed, but really the 6 speed is pretty quick, too. It's a noticeable but not night and day difference.

And congratulations on the new car - you'll love it!

Slust

Oddly enough my car was waiting till 70mph to shift to 7th gear today. In Sport mode the car will hold on to the lower gears longer as it thinks you want the power at the drop of a hat. It will hold the gears even longer if you WOT it. So you may have to get it up past the shifting speed and hold it for a bit. The more you drive in Sport mode (such as your daily driver mode) the ECU will tone down this behavior.

As far as red line goes, I've only done it 1 time in Auto. I've done it a couple times in Manual mode but I also like to shift once I hit the sweet spot of the gear. Still recommend following CTLG's advice if you want to bounce off the rev limiter.

ujwal1989

Thanks carderoni for starting this thread!
I have a RWD 350 and I noticed a few differences between the RWD and the AWD that my friend has (both 2014 F-sports).
The throttle (not the response but the peddle) is much more sensitve in the AWD than the RWD. Meaning I'd have to press the RWD throttle deeper than the AWD to attain certain amount of acceleration. I'm not sure if this is something specific to my car. I confirmed that this was not just my feeling by leaving the car in P and revving the engine to 3000 RPM. The AWD needed a lot lesser force on the throttle to get there. Do you observe the same thing?
When I spoke with the service rep about what I noticed, he just said that the AWD and RWD are programmed differenently. I'm not sure if that's the reason.
I'm may be imagining things, but I also notice a lot more brake dust on my rims than on the AWD's. Even the brakes feel different, AWD's has more bite to them. Could the reason for this be that my friend's car is 1 month newer and has 1500 miles lesser than mine( Mine is at 5500 and my friend's AWD is at 4000)? Or my car does have some issues :| . I think I should mention that my friend is a lot more harder on the brakes than me.
The last thing is that the AWD sounds louder above 3500 RPM. My car feels smoother and more refined when revved.
All this makes me wonder if there could such differences in almost same models of vehicles purchased almost at the same time.

carderoni

I've noticed the opposite phenomenon with the throttles, actually. The gear ratios in the RWD's 8 speed are more aggressive than the AWD's 6 speed, especially first and second gear (by the time you top out 8th gear is about the same as 6th in the AWD), so off the line the throttle feels more sensitive in my RWD car than it did in the AWD car.

As for brakes, I haven't noticed much of a difference in brake feel/response or brake dust. The two models come with identical brakes, but something that might contribute to a difference could be the way the cars implement engine braking. I've noticed that engine braking in the RWD car is more pronounced, especially in manual mode. This could mean the brakes themselves are doing less work, resulting in less dust. But with two different drivers, who knows for sure.

I have noticed that the RWD car seems to emphasis the lower frequencies of the exhaust note, which I'm guessing is due to the 8 speed keeping the engine at lower RPM's when cruising compared to the 6 speed. That's more of a guess though since I've never driven the two cars back to back for extended periods.

Like a lot of other owners I've noticed that both cars "opened up" after the first 1-2K miles. Mileage noticeably improves and acceleration becomes smoother. Whether this is from the drivetrain actually getting broken in, the ECU learning your driving habits, or a combination of these and other factors is anyone's guess, but it does seem to be a trend.

Slust

Ok looks like the car shifts to 6th gear around 55-57mph in Sport mode.

When I was trying to figure out the speed I found out something interesting. Normally I switch to Sport mode when the car is in park as I figure it is cleaner to do it that way. On my way to lunch I started driving and realized I forgot to put it in Sport, so when I came to a stopping point I switched it. The throttle response appeared to be that of Sport mode but it shifted like Normal mode. I got up to 8th gear when I stopped accelerating. So I was in 8th gear at 40mph in Sport mode. This is full auto by the way.

On the way back I switched to Sport mode like I always do, in Park, and it shifted based on the speed I was going (55-57 = 6th gear, 67-70mph = 7th gear) which I thought was pretty interesting. Not sure why the shifting behavior changes when you put the car in Sport mode in Park vs Drive.

Makes me wonder what exactly gets turned on (for lack of better wording) and what doesn't when you change modes when the car is in drive.

KumaF

When you switch from Normal to Sport while driving, the car doesn't change throttle response or shifting points right away, and in Sport +the steering also become heavier gradually. I remember reading about this somewhere, which claimed that the car was programmed that way as sudden changes in those parameter would make the car less predictable to some.