Kurtz

iTrader: (1)

I was gonna respond in detail here, but it seems panyo64 has already done a pretty good job explaining things to you... even explaining why you're wrong about the auto-x track.


Your continued comparisons to other cars remains quite silly though... apart from vast differences in gearing, torque curves, weight, and a myriad of other factors...is the stall speed of the torque converter (and the STR and size of the converter too, especially if trying to compare to other vehicles... switching from say a 12" to a 9.5" converter alone can make a significant difference... but for this situation stall speed is the big one).


THAT is why you can't just rev to 4500 and dump it and get a great performance out of the car.

Your comments, despite all the "race experience" you claim, suggest you don't even know what stall speed is, or why it matters.... since you didn't even bother to mention it in all your talk about how a "4500 rpm launch" should be ideal and no problem.


Here's a nice explanation for you though:
http://www.bankspower.com/techarticl...ng-Stall-Speed



But once stall speed IS reached... trying to launch higher is fairly pointless.


Which is why the IS350 is not traction limited and why AWD doesn't help at the track.

You know... like I told you in the first place.




I'm not aware of anyone who makes aftermarket converters for the IS350... and even if there were I suggest that driveability with a 4500 stall converter on a 2IS would be utter crap... (and boy howdy you'd hate driving that thing in the snow... which kinda defeats everyones purpose in buying AWD)

I can say that as someone who has been going to the track for more than 10 years, has owned and built cars with a lot more power and torque than the 2IS... and has been through a pretty decent range of aftermarket torque converters/stall speeds explicitly for drag racing vs. street-ability reasons.




Kudos BTW to panyo64 not only for his excellent input on the track information (though I'm curious WTF you saw repeatedly breaking a TH400... I went through my own share of 4L60 transmissions but never could break a TH400... only guy I ever saw do so was in a nearly 5000 lb vehicle with nearly 900 hp), but his response to me regarding the "lazy driver" notion for AWD... It goes a lot further in explaining the popularity of AWD despite it being mostly a negative performance-wise than the couple of earlier defenders of AWD did in supporting the drivetrain choice.

It's still not a choice I agree with (and neither does he all else being equal it seems) but I can certainly accept the non-enthusiast owner, which I agree with him is the majority of both lexus and car owners in general, won't really care that he's giving up a little mileage and performance in exchange for not having to learn better driving technique, or having to bother using proper tires and it being "good enough"

I'd still argue the folks who crow about the "safety" of AWD and then tool around on all-seasons are lying, at least to themselves, but likely it's out of ignorance of just how much safer proper tires are regardless of your drivetrain... and that's something I think is worth educating folks about... then again people will run out to drop thousands on BBKs thinking it does anything to stop them shorter when it doesn't, but try and explain that proper tires will and they look at you funny...so that might be a losing battle :P


My issue was primarily with the folks insisting AWD was the better choice for performance...it ain't when a car isn't traction limited... and under most conditions for most people, the 2IS simply isn't.

GrandSedanFan

iTrader: (1)

Budget build pro street cars will spit out TH400s all day long because some people won't spend on the extra trans cooler. Congratulations, that trans went 9.20s... twice. Saw 'em at Englishtown, Atco, and Island (mostly Island, because a lot of people who won't spend the money for proper cooling also won't spend the money to build a certified cage, and tech there is a joke). A few friends of mine have lost third gear because of it.

And my point about the typical car owner....

In 2004 I had a G35 Coupe 6MT. It came with Michelin Pilot Sports. Which are useless under 45 degrees. It got cold early that winter. I remember driving with a friend and the car was all sorts of loose because I hadn't switched tires yet. She looks at me and goes "You spent all this money on this car and you can't even use it in the winter? You got ripped off."

That is your standard car owner.

And, not for nothing, it has been infinitely more convenient in my current living situation not to have to store three sets wheels and tires for winter and haul them around to change. Snows on the GTO meant I could damn near drive a high 12s car in the snow if it wasn't too deep or not up a hill (although it was a bit rough on the clutch, as I'd still have to slip the hell out of it to get moving). Hill starts were still fairly useless. All seasons on the RX mean that as long as I don't high center the vehicle, I can get virtually anywhere (including up a muddy, snowy, and rocky trail to my buddy's cabin in Vermont) as long as I drive carefully.

autovation

iTrader: (1)

I've auto-x'd AWD & RWD cars/trucks dozens of times and with AWD you keep the same line but you can get on it quicker after the apex, this will be especially true when the cars are identical with the only difference being AWD vs RWD. It's all about balance + power and traction out of the corner. I find it much easier to control the balance with AWD.

Can you launch your RWD IS at the full stall speed like an AWD IS can? I certainly can't, even with sticky F1 275's in the back.

Let's stop the personal attacks on credibility, ok? Just like you I've owned several 500+hp cars, drag raced and auto-x'd for 20+ years now, as well as designed transmissions for several OEM's in the 90's (including Mercedes and Jeep AWD transmissions).

Kurtz

iTrader: (1)

Unless you've done so with a 2IS in both trims you can't really say.

But since the IS isn't really traction limited the weight and balance probably won't be offset by extra traction.

I could certainly buy that the AWD might win on an auto-x course being flooded... but not on a well preped track.



Do you actually know the stall speed of the RWD 2IS?

If not then you've no idea if you can launch at stall speed or not.

But it's not really relevant.

Again, this is evidenced by the fact that the AWD car, launching at higher rpms, still doesn't obtain any better 60' times than the RWD one does launching at 1500 rpms.

If the car was traction limited then that wouldn't be the case.

(it's also quite possible the two cars don't even have the same stall speed... they sure don't have the same transmission)


Feel free to experiment with this- but the factory service manual mentions no more than 5 seconds of brake torquing at a time (with at least 1 minute of cooldown after) or you risk damaging the transmission.

machefai

wow, too bad i hadn't been on in a couple of days! i sure missed a ton of serious snow tire talk!

Glad to see we're finally on to some of the good stuff! I did notice in the vid on the first page, it showed a launch of about 2700-2800rpm. It looks like they had a little more than a 1/4 tank, and they could benefit slightly from getting that down a little for sure. And if they DID in fact have a bad start, w/ the sunroof open, extra weight in the trunk and have it be 70 degrees out, then I would imagine the awd could do much quicker than 5.1 sec's. Especially after you do some simple mods like an intake, headers and exhaust!

But as always, none of us will know how much of an advantage the improved brake torque will actually play in over compensating for the slight increase in weight. But clearly this vid shows an increase in rpm at launching at a whopping 1700 rpm higher than caymandive's run pointed out below! That's a difference of starting w/ out any brake torque at all! Would love to the impact of getting up into that power range from a start w/ mods and ideal conditions!

This is why I really started this thread, in hopes AWD's will start hitting the track with all they can bolt on! Can't wait for an awd to hit it w/ an intake, headers, exhaust, etc and maybe even a supercharger!

Does anyone know what the most hp an IS has been able to achieve? Can it break 400?

Jmags

iTrader: (1)

Kurtz.

While the 250 awd/350 awd might not be "traction limited" or whatever you are calling it on a track with dry smooth sand free pavement. I can for SURE tell you that even a Honda 85hp FWD car will spin it's tires coming off a stop under the right conditions.

Here in the north east, as you know, it rains quite a bit. The roads are generally horrible when it comes to back roads and have tons of holes/sand/dirt/leaves all over them, depending on what time of year you are driving on them.

This is where the AWD shines. If I REALLY HAVE TO I'll video my drive to work, where the AWD comes in handy on three different occasions, EVERY SINGLE DAY of bad weather (ice, rain) or ****ty road conditions ( dirt/sand/leaves).

One is at the end of my street, it's a stop sign - I make a right hand UP hill turn where people FLY down the road. Even in my 98 year old grandmother's car (90's base Chevy Cavilier) the tires would spin and leave you hanging on this turn. With the AWD the CAR GOES.

Also there is a specific TYPE of road here that is SUPER slippery when it gets wet for the first time after a while of no rain. Again depending on where you enter the road, it's an up hill turn. In the snow, even with snow tires, in a RWD you are NOT going to be able to enter this road from the side streets the way it is.

And lastly, dirt/sand is no longer an issue like it used to be.

For you to sit there and make a generalization about how useless AWD is to the common driver really isn't valid. People buy subarau's and audi's partly because they just want it to go.

If you're trying to say on perfectly flat dry roads AWD is useless, FINE. However in REAL LIFE roads are NOT ALWAYS PERFECTLY FLAT AND DRY!

Since I got this 250 awd in January, I've seen ONE 350 RWD and the rest have been 250 AWD's.

Kurtz

iTrader: (1)

I guess being away for so long you missed the technical explanation of why launching at higher RPMs doesn't help... explained by the guy who did take his AWD 350 to a 1/4 mile track and repeatedly was unable to get any better 60' times than RWD owners... and ran 13.7s as his best times... a couple tenths off a typical RWD model.


Because the 2IS isn't traction limited. Like I told you 3 threads ago.


Anyway... there are no headers for AWD models... the existing ones don't fit. Mazzuri made one prototype set that one member has, but I don't think the gains were that great, and he's no longer in business.

Your only power mods that are actually sold in the US are intake and exhaust. If you go with a full exhaust ($1500 or so) plus a Joe Z intake ($125) you should almost make back the power the AWD system is robbing from your engine compared to a RWD model... probably not all of it, but most.

And that's it. (well, except for nitrous, see below on that)

There are no superchargers sold for the 2IS in the US at this time... (and the one that was sold was $6000 for about 50 hp).

You can occasionally find a used one though from one of the 5 or so that were ever made.

A stock RWD 350 puts down about 265 at the wheels. I'd expect an AWD model to be more like 235-240.

Intake and exhaust give you about 15. (illegal exhaust... legal is more like 12)

Headers (again, don't exist for AWD models) are another 15

So theoretically with all the bolt ons a RWD should be able to crack 300, barely...but I've yet to see a dyno of anyone doing it.

With a 65 shot of nitrous and the bolt ons you can get into the 325-330 range... which would barely keep you above 300 with AWD... HKS350 has safely run that on pump gas.

With the LMS supercharger in stock form you might get a similar # to the nitrous

So no, nobody has come even close to 400.

Kurtz

iTrader: (1)

Sure... on summer tires on a sheet of ice I'm sure it will.

If you're spinning tires on an 85 hp car, short of doing a 6k rpm clutch dump, or trying to launch in a hurricane, your tires are bald. Replace em.

Sure. But RWD with summer tires does great in rain.

better than AWD with all seasons in fact.

But unless you're driving like a maniac either will be perfectly safe in the rain... or on a road with some dirt on it.


If it's a >15-20% grade then I'm sure AWD is a huge help in the snow there.

As we've established though, RWD with snows would be fine too if it's less of a hill. If it IS a 15-20% grade or more then you'd have trouble with RWD no question. But that's a pretty steep hill, and it'd only be a problem in snow.

If you want to see a 20% grade BTW, here's a picture:

http://www.kenpapai.com/racing/sf2001/lap8_5719.jpg

Is your hill that steep?

If not then RWD with good snows will be fine, though you won't be able to launch it like you're drag racing.

In the rain RWD with summers will have no problem at all. I can't speak to what your grandmas car has- probably very small, very cheap, tires though.

Again, tires matter more than drivetrain. I've posted objective testing proving that.

and again, if the hill is steep enough, I can believe that. Otherwise not so much.

This one I'm not getting. If you mean some sand or dirt that got spread across a paved road it wouldn't be an issue in RWD with decent tires either.

If you're trying to drive up a sand dune or something, well, you're in the wrong car regardless of drivetrain. That's jeep work.

It is though. The average driver has to drive in snow less than 5% of the year. And outside of snow AND a big hill, RWD with proper tires works great, while costing thousands less and offering better mileage AND better performance.

For the minority that live where they spend 6 months in snow (Alaska, parts of Canada, maybe a few folks in the peaks of the rockies)- by all means those folks should have AWD (though again something with more ground clearance would work even better than an AWD IS). But that really IS a small minority.


and because they don't know any better. I'm trying to fix that


It's also not real useful in the rain... especially if you keep the all-seasons on it it came with... RWD with summers will outperform it.

In the snow it's not useful either for stopping or normal handling... it is useful for going up steep hills in the snow.

And while I understand your personal drive apparently has a couple... most folks don't... (and even then most folks deal with snow between 0 and a handfull of days out of a year).

First... 4 out of every 5 ISes sold is a 250. Because they're cheaper and the average guy doesn't give a crap about the extra hp.

Second- Lexus allocations to dealers in the north is primarily AWD models...because again they assume the average buy doesn't know any better and will happily pay $2500 more for the car thinking AWD with all-seasons is safer year round compared to RWD with proper tires... and it's not

machefai

lol, no i caught it. it's just that, and no offense to my fellow awd'r, panyo64 who posted his times, he's nearly 300lbs and was bone stock. Great numbers to know though, so I appreciate the info share!

panyo64, did you mention what rpms you were releasing at? was it as high as seen in the vid?

LexFather

When the IS first debuted Lexus figured it would be a 70/30 split 250 to 350 but it actually was a 60/40 split, so they have to chance production to meet 350 demand. Not sure what it is today.

GrandSedanFan

iTrader: (1)

2000 RPM. I didn't want to load up the converter higher than that. At 2200, I'm deep in the brake, past the stall speed. I am not willing to put the trans and converter through that kind of abuse.

The car with a 170lb driver would've gone 13.6s. 100lbs equals approximately 1/10th.

Kurtz

iTrader: (1)

Yup... 100lbs=1/10th typically.

Plus as I mentioned the factory service manual says brake stalling for more than 5 seconds at a time risks transmission damage.

And bear in mind- you can't change the fluid either... so you cook your fluid, you're pretty much stuck with it.

So others can feel free to experiment at the track trying to hit a really specific RPM, but they do so at their own risk... and as explained, brake torquing above stall speed does nothing except waste your time... it certainly won't make your car any quicker at the track.

I could certainly see a skinny driver on a very cold day getting AWD times down in the the 13.5 range (stock)... but you're not gonna see them matching the 13.2-13.3 times that RWD 350s hit in those conditions (stock)...and you certainly won't see them beating them.

machefai

Stinks about no headers yet for the 350 awd's, that's for sure.....maybe soon.... one can hope. I would like to learn more about the differences in trans though too.

RWD does 13.2-13.3 stock? I thought those were times w/ add on's, no?

Not suggesting anyone hold their rpms for more than 5 secs, but why would you need to? You could rev and release in less than 2 secs. Am I understanding the manual correctly? It means not to hold it at high rpms for more than 5 secs w/o releasing, right?

However, if it's true that a higher rpm release does not impact speeds, then yeah, I would say it may NOT be possible to beat then. I'm still kinda blurry as to how that would be true though....

Glad to finally see some initial facts come in from the track though, thanks panyo64! What cars did you go up against? Look fwd to hearing and learning about others! Keep 'em comin!

Kurtz

iTrader: (1)

Nope. Those are stock times with good weather.

Toothdoc for example ran a 13.228@105 in 36 degree weather in a stock RWD 350.

(and a 13.234 as a backup time)

That's the fastest totally stock one I know of... but Paul has a 13.345@104.42 in 43 degree weather...

Once it's a bit warmer the times move into the 13.4-13.5 range

Sure... if just wanting to "rev and launch" should take just a couple seconds.

I was mentioning the 5 second rule for folks who might want to try testing a range of SPECIFIC rpms... ie "I'm gonna launch at exactly 2k... then exactly 2050... then exactly 2100..." etc...

It might well take 5 seconds or more if you're trying to reach and hold a very specific rpm rather than "rev to roughly X and go"



Read the stuff I posted on torque converters.

Once you're at stall speed you can't launch any higher than that

That's why drag racers put high-stall converters in their cars...you can gain half a second on your 1/4 mile time from a really good hi-stall converter... but you lose on-street driveability if you go high enough.

If they made the 350 in a manual you'd be able to launch at 4500 or whatever (though you might be replacing clutches pretty often)... but of course your shifts would be significantly slower, so you might well find this makes your times worse compared to an auto launching at 2k. (plus this car does not exist)

machefai

nice, those ARE some sweet times! Thought I recall seeing them typically in the 13.4-13.5-or higher stock....heck, those times above beat some w/ intake, headers AND exhaust!