Kurtz

iTrader: (1)

First- the video says 5.1, not 4.7. Which is slower than we've see from plenty of RWD cars.

What? that doesn't say anything at all about stall speed.

If someone got better 60' times launching ABOVE stall speed that would somehow contradict a basic concept of how automatics have operated for decades. But that didn't happen in either case.

But that didn't happen in the above case, and you're not even comparing the same result there. (you're comparing a 1/4 mile ET to a 0-60 time, without knowing what either ran in the other measure)

Plus- we've no idea how he measured 5.1 seconds... for all we know he was counting in his head... If you're not gonna run against timing lights like a track then show me a datalogger hooked to the car... or at least a G-tech or something on the dash.

In theory you want to launch higher- to a point...and after that point it'll be the same, or slower.

In real life it depends on probably half a dozen different factors, and they won't always be the same.

That's why you take your car to an open test-n-tune day at the track, so you can get a lot of runs in and find out your optimal times by trying a lot of different things out.

(Oh- and by the way... tire pressure isn't just about traction... it's about weight transfer during launch as well... same reason a person with adjustable shocks would set front/back differently at a drag strip for the best times)


Lastly- bear in mind caymandiver changed his tire size to change his gearing. It's possible that changed the rpms he got optimal launch at. In fact all 3 of the fastest times on the drag page changed tire size to change gearing.

But the best 60' times were toothdoc- on stock tires. (in a stock car)

But that's another reason to do test-n-tune... it's possible a different tire size might help or hurt your 60' and even more fun is it might do something weird like slightly improve 60' time but make the 1/4 mile time slower... or vice versa.

There's a lot that goes into drag racing.

I'm not sure anybody knows what the AWD stall is... it might well be lower than RWD...or it might not. Generally the higher it is the less efficient it is so they might well have put a lower-stall one in the AWD car to help mitigate the lower mileage and greater drivetrain losses a bit.

Stall speed can vary a little bit from car to car, but on a RWD model it's something like 2490, +/- 150. That doesn't mean every RWD cars best launch and 1/4 times will be launching at 2490 though.
(if you wanted to remove ANY question of traction and figure this out for a given car you'd go to the track on drag radials, then test launching everywhere from idle to 2700 rpms, cooling down fully between each run... but I suspect nobody has that kinda time... it'd be really interesting data to see though)

As to the AWD, while it's true we only have 1 data point, it's from someone who knows what to do at a track, and tried a number of techniques and never broke out of the 2.0 range for 60' times.

Given RWD cars have put 1.9x times that suggests traction isn't a real limitation on the RWD model.

That doesn't mean it's IMPOSSIBLE an AWD will ever put a better 60' time down... I'm sure in 36 degree weather on a perfect day he might- maybe with a change in tire size to improve gearing too... But I doubt he'd end up with a better ET than the RWD car in the same conditions... the weight and drivetrain losses already put him at at least a couple tenths disadvantage out of the gate.... so you'd need to see AWDs putting down 1.7s before they had a serious chance of "showing the RWDs their taillights" as someone put it.

machefai

Sorry kurtz, wasn't referring to the vid in this thread, rather the one in the link autovation posted. showed a rwd launching at ~2k and hitting 4.7 0-60. agreed that it's not the same as a 1/4, but does show much improved 0-60 over launching at 1k in other vids online and certainly that of just flooring it. It also showed many rwd owners complaining about the bad traction and the inability to floor it using brake torque w/o losing their back ends. in fact, they said you cannot just floor it, but had to "ease it down" even with dropped pressure in the rears.

I need to know the stall! lol

GrandSedanFan

iTrader: (1)

Although Kurtz and I do not see eye to eye on certain topics, on this he's absolutely right. I'm a moderately decent drag racer. If I really wanted to, I could pull weight out of the car and toss my 150lb buddy in it who has cut 100s of 1.7-16s, and it'd go 13.5. However, if he were to run down the track against ME in a RWD IS350, I'd still win, even with my 120lbs deficit.

Kurtz

iTrader: (1)

Ah, you mean the videos of the RWD 2500-ish rpm launches in the second thread?

That seems to suggest no traction problems for RWD.

But again it'll depend on the tires, the road conditions, the weather, and more. We've no idea what tires are on those cars for example... I can tell you my Hankooks (stock size) are a LOT better than the OEM Turanzas that came on the car... measurably shorter braking distances and I was pretty impressed with their ability to NOT spin at all in the various 0-60 testing I did for the Sprintbooster review I wrote.



As to the rest of those threads about launching a RWD-

in the first one the author originally didn't know how to launch properly (evidenced by his 60' times) and later got them down lower...in fact he had a 13.9 best the first time and a 13.1 by later in the thread with some advice...

and he was also on 19" rims with different sized tires... read through the thread and you'll see people offering advice like avoiding the water box on street tires and such...


The other thread is about 1/8th mile runs... in that one the guy seem to have a bit of an obsession with R/T for some reason, despite it having nothing to do with ET... but anyway he mentions one 1500 rpm launch with wheelspin, and then another one that was a lot better... this again can easily be a surface prep issue (water box being a biggie)...further- he was doing huge John Force style burnouts... which are not a good idea for regular street tires... he even notes this near the bottom and states he'll skip that next trip... he was also running with no spare and almost no gas (he mentioned his "range" as only 10 miles at one point)... interestingly, once he went to a 1/4 tank, his 60' and ETs both dropped. Weight over the drive wheels produced a better launch.


When he went back a second time he skipped the crazy huge burnouts and had a 1/4 tank, and got consistently better times... no mention of wheel spin either except the one time he tried to launch as high as 2500...and he seems to entirely give up trying high rpm launches after that so we've no idea if it was a one-time fluke like that first 1500 launch was.

Later he appears to give up on burnouts entirely, and better times still.



As I say though, there's a LOT of variables that go into your times at the track.. I could certainly buy the idea that if your goal is "running the absolute best possible 60' times a given car can do" that an AWD 350 might be easier to find that best possible time on... but that doesn't mean that best possible time will be significantly lower... and the RWD one will still have the lower ET assuming both cars are decently prepped.

I suspect that if you were talking about an IS-F though, you'd be at the point an AWD model would turn out better times on street tires...but the 350 just isn't there power wise to need it.

(and the AWD model F would lose if you let the cars use drag radials of course)


There's a myriad of variables that go into all this- but a rule of thumb that I'm sure you can find exceptions for would be:

~300 hp: RWD>AWD, pretty much period.

~400 hp: AWD>RWD on normal street performance tires; RWD>AWD on street-legal race tires.

~500 hp: AWD>RWD on anything but slicks, where RWD is still doing well.

>500 hp: AWD all the way, no question.


But the thing is, the IS350 is that first kind.

machefai

but i guess in reading both threads, I noticed that multiple people were pointing to the rwd definitely being traction limited, especially using brake torque. There was mention of spinning the rears in multiple gears down the track! Now i'm not saying some didn't find that sweet spot in gas pedal/tire pressure/suspension/gears/type of wheels/etc, they clearly did, eventually. But what I think it proves is that it's clearly present in rwd's and something you either need to learn and get used to at launch, or overcome somehow w/ add ons!

Jeez, def a lot of factors that come into play, agreed! So if they met stock on the street, I guess the differences between a 14-16 sec type run(even w/ bolt ons and hankooks) as seen in that first thread and one in the mid to low13's boil down to mostly weather, driver, time off the block, then it's still unknown about the AWD's stall speed, tranny, weight(awd/tires/gas/driver weight/spare/jack/etc) to see who might win!

As I believe I mentioned before and seen in that 1st link, the difference in .5 sec or full seconds in a 1/4 mile happens all the time from run to run. And I would think that's even compounded more by an off the track race where distances aren't typically that great.

GrandSedanFan

iTrader: (1)

On the street, any number of variables can affect a RWD IS from hooking up. Surface temp, tire temp, surface condition, so on and so forth. . However, on a prepped track, at 25-30lbs of air, on stock tires, the car should hook all day long.

Mind you, this is with a quick dust-off burnout and not trying to load the converter up too high.

I think the solution is for someone to bring a 2011 IS350 RWD to a rental with me one day and let me run 'em both.

I also propose that the members of this thread contribute to the $200/car entry fee, as this is purely a data collection exercise for the benefit of the community.

machefai

HAHA! Well I think it's only a matter of time before we get a bit more data on the awd's. maybe eventually we'll even get a nicely tuned match up from both parties. Would be fun regardless the outcome! Honestly, I like this car in every make! Love the looks, comfort and performance!

But as far as not losing traction w/ the 25-30 pressure, in those 2 previous threads above, you had folks with that same pressure still losing grip if they stomped on it, ASIDE from the wet tracks. (Which is kinda sweet. love all the power in the IS!) But I don't know for sure if that's always the case since I don't drive one. Maybe smokeyis350 can chime back in. Seemed his last run he lost his wheels every shift! This was after mentioning he'd tried dropping the pressure to ~25.

Well aside from all of the "what if's" I presented above (prob a bit wishful thinking), at the very least, I think we determined that the awd will provide a slightly more consistent launch. I'm not saying it would necessarily be faster, not going there. All I know is, I've YET to be able to lose any of my tires, ever. No matter how hard I stomp(even while trying brake torque/trac off), even with my stock tire pressure and all-seasons. And honestly, I hope I never do lose my wheels! But maybe, just maybe the brake torque does have a bit more room for some extra power. Could it be hiding in a range the rwd can't take advantage of without losing contact?

smokyis350

iTrader: (21)

Poorly prepped track. The only time I ran 25 PSI I believe is when it was import night. 90% of the cars were FWD and they got the track wet 1/2 of the way. The crews never bothered cleaning up the track.

All my 13.1 runs were accomplished by brake boosting and then stomping the accelerator with ~32 PSI. No traction problem at all if the track is perfectly prepped.

GrandSedanFan

iTrader: (1)

Track prep track prep track prep.

Where are you launching?

machefai

Thanks for the info smoky! At what rpm did you launch? And what about the last post? You mentioned not being able to hook too? Was that the import day or was the import day one of the previous?