Rock-a-Lex

iTrader: (4)

I have a question for you all. I just want to get some ideas as to what makes the GS4XX so inferior when it comes to performance. Please read the below example to further expand on my question...

I have read in MANY places (mainly on CL) where various members either currently or in the past have had superchargers on their GS4XX's, had them properly tuned and running excellent where they dyno'd anywhere from 350-400whp and around 350ish wtq range. So assuming that their is in fact a 20% drivetrain loss, this equates to 440 - 500hp @ crank and around 440 torque at the crank - a MONSTER! However, I always see 1/4 mile runs NEVER braking 13.1/13.2 in the 1/4 mile!!! Why the hell is this?

Take a stock IS350 for example...nice cars but I don't know much about them. However, I DO KNOW that in stock form they have 306hp and 277tq at the crank and weighing around 3600lbs (approx 300lbs LIGHTER than a GS4XX). Well folks, time and time again I see these cars running 13.4/13.5's in the 1/4 mile and as low as (record) 13.2 in the 1/4 mile. How the HELL on gods sweet earth can a car with only 307hp achieve the same results as a car with 440-500hp???

The members with the SC'd GS4XX's never really mentioned excessive wheelspin during their runs so what gives? I know that the GS is around 300lbs heavier but there is NO WAY that this is offset by 150hp/150tq more.

So, for my ultimate question...what is the VERY VERY weak link of the GS4XX? and where is the VERY VERY strong link of the IS350?

This is NOT about comparing the actual cars! I have nothing against either car...just logically trying to understand the numbers and performance results from each as they do NOT make sense! Based on these findings I WILL NEVER supercharge my GS400! Either turbo it or get another damn car! I will be damned if I am going to throw $10K+ in a SC setup to only achieve results that of another Lexus in bone stock form (excluding the F-line).

It's a damn shame because the styling is there and the power is there it just doesn't efficiently or effectively deliver it performance-wise. On this note, I am keeping my car as-is and not performance modding anymore.

Can anyone add or comment on this?

GSJake

iTrader: (21)

From what I can surmise. The A650E. Thats the culprit. Gearing is gearing. HP is HP so what is in the middle.. the trans. Our trans is only a true 3 speed. As you may or may not know, 2nd and 5th are od of 1st and 3rd. I am no trans guru. From what I have read the any manual will take the car to a new dimension. Just that the supra 6 costs a grip and the 154 is not cheap either. Also pending on who drives the car in the house this may not be viable.
I have not driven a manual GS but I did have a 540i\6 for many years. I dove a friends 540i\AT and it was totally different animal. Not even in the same league for responsiveness and fun factor.

3UZFTE

Rock, I agree with GSJake, the A650e is a power rubber, I think it's time you got V160, you've done everything else except for FI and a 6-speed.

lexusben

iTrader: (3)

What would be a good transmission swap automatic wise for the GS400?

JeffTsai

iTrader: (1)

IMO only good trans swap for the GS4 is to do a 6speed manual. It's a close gear ratio transmission. The R154 has longer gears which is good for a turbo car, but not so good for NA. The A650E's gear ratio is a decent compromise because the gears are pretty close together. The main thing holding back the 5spd auto in the GS is how slow it shifts from the factory. It takes the stock setup almost 1 second between the 1-2 and 2-3 shifts. I've been tweaking my transmission heavily to try and find the sweet spot for the perfect shift-timing. I'll post up some videos later to show how fast my transmission shifts right now.

3UZFTE

Jeff, I am sure I don't speak alone in stating that I am sure we all want to know a little bit more about the tweaks. I have followed most of your build and I am pretty familiar with the A341e, but not as much with the A650e other than what has been posted. Any chance you could shed a little light on how your achieving the shifts, via line pressure, bands, or valve body, etc. I know I would like to know, not sure about the rest of these folks.

Quick VR-4

iTrader: (2)

I think we are wondering why performance sucks out of a non-performance inspired car. Sure Lexus wanted to give you enough power/torque to get around town, but I think that is where it stops. These are luxury cars that were never designed to be street beasts. The tranny shifts slow and smooth because that is how it was designed. I think if you want performance and speed, a GS4XX is not the best platform. My car has plenty of power for me, but I am not trying to break the 13 sec. barrier in it. I have a sports car for when I want to go fast and have the GS for when I want comfortable cruising. In your comparison, I think we can all agree the IS350 is a more sports minded car and much more efficient since it is a few years newer. I think these cars do very well based on the time of production and similar cars in its category.

Rock-a-Lex

iTrader: (4)

My entire point is that I FEEL that these cars are BOTH considered sport-oriented luxury cars!!! Don't forget, in '98 the GS400 was supposedly the world's fastest 4dr luxury car (NA of course). You are correct in that it is NOT a sports car and NEVER was and of course there are better platforms (cars) for modding. However, I highly doubt the GS was/is considered as strictly a "luxury only" car based on the aforementioned. So basically, if the GS4XX had a different tranny it would be a WORLD of a different car!

lexusben

iTrader: (3)

Yeah the slogan for the 400 was "Something Wicked This Way Comes" so even though maybe it shouldn't handle or perform like a true sports car, it should come pretty close.

Quick VR-4

iTrader: (2)

And it did.........back in 1998

Compare a 1998 Corvette's performance to the latest 2010 Corvette. Was the 1998 inferior then...not at all...compared to a new model...absolutely. This is not only due to motor, but everything such as materials, suspension, aero, etc.


1998
Performance Specs
Top Speed: 173
0-60: 4.8 sec
1/4 mile: 13.2 @ 109

2010
Performance Specs
Top Speed: 190
0-60: 3.9 sec
1/4 mile: 12.2 @ 117

Rock-a-Lex

iTrader: (4)

^No one is saying that one has greater technology than the other!!! Obviously, ANYTHING newer (it could be a frickin' blender for Pete's sake) almost always has better technology than its predecessors! However, the POINT I was trying to make is that it was/and still is considered a sport-luxury sedan! So, eventhough its platform is not that of a SPORTS-CAR it is STILL "sport oriented"...just like the IS350. Look at the LS versus the GS, especially in the late 90's - tell me which one you think is more of a sport-sedan; obviously the GS.

IMHO the IS350 is still at the same sport-sedan oriented level as the GS4XX, it's just that due to it being MUCH newer the newer technology allows it to utilize its power more efficiently thus making it SEEM like it's a sportier car. They both have 4drs, both have a relatively soft suspension in stock form (compared to a real sports car), both have engines that deliver a healthy dose of HP and TQ, both ONLY come in automatic; IMHO they are both sport-sedans.

The reason of MY THREAD is to find out what makes the IS350 able to achieve what it does on small(er) power levels (compared to an FI's GS4XX) and what is KILLING the GS4XX performance? ...and I found the reason that answers both questions - the transmission. The IS350 has a VERY quick shifting transmission (due to newer technology) and the GS4XX has a VERY slow-shifting, lazy transmission; opposite ends of the spectrum where the GS4XX could have more than 100hp on the IS350 and can barely achieve the same results. Weight also plays a factor but its MAINLY due to the transmission.

Who knows, for all we know a moderately modded GS4XX with a 6mt swap could deliver MUCH better performance results than say a heavily modded auto GS (turbo'd or SC'd). I'm sorry but with over 350hp and 380tq coupled with a high stall TC and a more aggressive rear I should easily run around a 13.4 in the 1/4 mile. Based generally on weight and power; however this is obviously unattainable due to the crappy GS auto transmission - change it out to a 6mt and you will see those figures or damn near close to it!

DaveGS4

iTrader: (2)

Don't put too much of the difference in the transmission. Weight (3,527 lb) of the IS350 and the 2IS' gearing (4.083:1) also play a big part in the overall equation, not to mention the improved delivery capabilities of the newer NA engine design with direct injection, higher compression, etc as well as more advanced traction control and other improvements. Every 100 lbs takes off a 10th of a second according to conventional discussion so that's .3 explained immediately.

Another factor I haven't ever really looked into for difference between the two models (but could matter) is aerodynamic drag.

EDIT looked it up... For the IS350 Aerodynamic Drag Coefficient 0.28 and for the GS it looks like 0.29, another very slight improvement.

Rock-a-Lex

iTrader: (4)

...agreed Dave, and thanks for your input! However, are you saying that these differences are equalled by adding another 150hp to the GS? Seems like a lot of power is needed in order to achieve the same results. The add of 150hp comes from a stock GS4XX at 300hp and adding 150hp via FI (roughly 360-400whp).

As far as traction control advances go, would this even matter in this equation if both cars run a 1/4 mile with traction control off? Because from what I have read this is what the majority do at the track.

I am not too sure but don't most FI GS4XX's have the 3.76 LSD diff? Still, less aggressive than the 4.08 IS350 diff but much closer performance-wise than that of the GS's stock 3.23 gearing. Also, doesn't the higher torque figures help the GS in this comparison? The GS ranging from 310-325tq versus the 277tq of the IS350.

I do agree with the weight difference though...hands down; .2-.3 difference is easily seen from this weight difference.

The difference must mainly be from the tranny IMHO. I have read in many old threads that the original CL members with FI experienced such issues with their trannys that they literally had to let of the gas almost every gear shift to prevent slippage during their 1/4 mile runs...if this is/was the case then running more power from the engine through the tranny is rather pointless.

DaveGS4

iTrader: (2)

Sorry, still don't agree on the 'main difference' being the tranny. What I'm saying is that it is the COMBINATION of all those smaller things that add up to that significant difference in performance. The transmission is certainly a factor, but its not the only one and I don't think its going to be the 'end solution' to getting a reasonably fast 2GS at the track. Have to look into doing weight reduction, the right gearing, traction improvements, etc too

Gears vary from car to car - I haven't noticed any propensity for the 3.76 vs 3.23 with FI but even 3.76 to 4.08 is huge jump.

For some background here are fastest 5 IS350's courtesy member Caymandive
http://spreadsheets.google.com/pub?k...2lAN-EQ&gid=10

GSteg

iTrader: (15)

Rock, you gotta look at other things than just rear end ratio. Rear end ratio means nothing if you don't take into account the transmission itself. The IS350 has higher torque multiplcation in every single gear. It makes up for the deficit. In fact, they make both about the same amount of peak torque in 1st gear, but from there one out, the IS350 takes the slight lead.

Coupled that with a faster shifting transmission, slight weight advantage and maybe 16hp difference, you can see why the IS350 is quicker.


There is a spread of 8 years between the two cars. That's an eternity.