To all those seasoned performance experts on the GS -

I completed my handling mods last month (other than rims and tires - too expensive to do that mod properly right now). I have ordered cosmetic mods as my second stage of mods and that will be complete in April.

Now I want to focus on incremental performance mods. Based on what I have read here, this is my summary of what most members seem to think is the best bang for the buck (not necessarily in this order - please feel free to post your opinions regarding this order).

1. SRT intake with ECU (30 - 40 HP gains - can anyone here comment on this in terms of real world experience?)
2. PI Torque Converter
3. Tranny cooler (what brand is the best out there?)
4. TRD LSD (not sure which one is best that improves launch times and is easy to install).

Any others. Supercharging or Turbocharging is not an option right now - way too much money for the incremental increase in performance - unless someone has a radically different experience - after all we are not talking about the type of performance that the 2003 E55 AMG supercharged car has - almost 500 HP, 0-60 times of less than 4.5 seconds etc.)

Please post prices when you comment on the above mods and the order you think is best to do these performance mods.

Thanks guys!

 

I don't have the SRT intake but from what I've heard/seen/read it might give a slight dip in torque/responsiveness at low rpms but you do gain some HP in the higher rpms. I personally doubt it's 30-40. IMHO, not worth $600.

PI TC - I have it - no brainer upgrade. DEFINITELY allows the car to put more of its maximum torque to the ground more quickly, improves shifting, etc. Carson has 'em for $860 I think and it's about a $500 or less install. I'd say this should be #1 on your list.

I really don't know if the a cooler is needed, but I figure it's cheap insurance to protect a $6000 transmission. I've got PearlPower's (Lee's) kit on mine, which includes a B&M racing cooler. I think his price has gone up since I got mine so I won't quote.

LSD - there's TRD kind (clutch, only the 'inside' part) which is less money to buy but more money to install. Then there's Supra / (Torsen, whole diff.) RMM kind - more money to buy (maybe) and less money to install. I don't have an LSD - I had the TRD part for a while but couldn't find an installer. I'd probably buy the Supra part if I could find one for a reasonable price.

 

IMO:

A) Do #2 and #3 together.
2. PI Torque Converter & 3. Tranny cooler (what brand is the best out there?)

PI TC is what I recommend as biggest bang-for-buck performance mod. Least obvious to dealers as well, if your dealer gives you a hard time about mods.

Tranny coolers are pretty much the same. The one Bitkahuna has from Pearlpower looks great (in pictures at least, haven't seen it in person yet), but functionally they're about the same. Others like Permacool (mine) and Hayden are fine and a bit less expensive.


B) Next do the intake 1. SRT intake with ECU (30 - 40 HP gains - can anyone here comment on this in terms of real world experience?)

That HP increase is a bit optimistic IMO, you're more likely to see 10 - 15 increase at peak HP. You may also lose a little at low end. I'd still recommend this mod, but don't get it if you don't like a bit more noise in the cabin as it's fairly loud (but cool sounding ).


C) TRD LSD (not sure which one is best that improves launch times and is easy to install).

Only get this if you have traction problems after doing A and B above. If you are never going to do forced induction (turbo, SC), I'd say get the Supra TT LSD (also sold by RMM rebadged) for the gear ratio jump to 3.76 which will make you faster off the line, but reduce your top speed. If you might do FI, go for the TRD LSD.

 

Thanks Paul and Dave! Based on your comments I think I will just pass on these modifications - it seems the performance gains are very slight - we are talking about less than half a second at best in 0- 60 times. Is it really worth spending over $3000.00 for that (The TC and LSD) ? I cannot justify that expense.

I will just save up my money and get a good light set of 18 inch rims with the staggered setup to finalize the handling mods on my car and then enjoy the car as much as possible till I can afford a second GS - (hopefully Lexus will come out with a performance version of a GS like an M5 or E55 AMG next year). Whoo hoooo - the dreaming starts!

 

I had the benefit to ride in DaveGS4 and Dex's modified GS4's to determine which mods I wanted to do first (they have all of the mods you listed).

My order of priority (and installation):

1. PI TC / Trans Cooler. Hands down the best mod out there other than forced induction. I paid $350 to have the TC installed and trans cooler plumbed by a local independent mechanic. I installed a Perma-Cool trans cooler model #1013 as "insurance" for transmission longevity. I sourced the cooler from Summit Racing ~$45 shipped.

2. Exhaust. I know you already have mufflers, but for the benefit of others doing a "search" on this subject it is worth mention as one of the first things to mod (I'm sure you agree with me). Expect little to no performance gain, but worth every penny for the sound.

3. Swift ECU / HFI. Definitely not 30-40HP; more like 10HP to the wheels and difficult to feel "seat of the pants". I ordered this from Intense Motorsports for $549 shipped and installed myself. I was quite shocked as to how much louder the car became after the Swift intake (50% throttle or more); this definitely isn't for everyone. DaveGS4 has a custom cold air box installed on his GS4 which significantly reduces the sound level of the intake to an acceptable level IMO. I ordered the same CAB and plan to install this week. As an additional benefit, the CAB should theoretically improve performance as it shields the intake better from the hot engine bay air.

4. LSD. I definitely plan to do this mod within the next couple months. I wouldn't do this mod unless you had the TC installed as you really don't need it for off-the-line traction.. I plan to install the 3.76 ratio Supra TT differential to take advantage of the peformance gains offered by a higher gear ratio (vs. 3.26 stock). Some have experienced hitting the rev limiter with the 3.76 unit; do a search to learn more.. You can source the Supra TT LSD for around $550 used and the install is very straight-foward vs. the TRD LSD (I was quoted $150 install by my mechanic).

Good luck!
Tom

 

i would consider the LSD more of a handling mod.

 

To effectively upgrade the performance of a GS400/430, all these measures seem at best just a way to burn cash as the real world benefit is very small.

I think the best way to really modify the performance of the car is to go Forced Induction, but then again that is whole different cup of tea with the cost running close to $15K. The long and short of this, keep the money for other stuff.

Thanks guys!

 

Although "very small" is a very subjective term, I would have to disagree. I would describe the real world benefit as "significant".

If you lived closer, we could line them up and I could show you what I'm talking about Try to hook up with someone in your area with these mods to experience the real world differenece.

 

Yes, I have to agree, I would need to see the actual improvement in performance to justify to myself it is worth it. Unfortunately in this neck of the woods (Canada), hardly anyone who has a GS mods it. In the four months I have had mine, I have come accross only one other GS owner who has modded their car - and that too was the L-tuned springs/shocks.

I wish I lived closer to some of you guys who are serious about mods................

 

i tend to agree with you here. the GS motor is pretty well pumped up from the factory, so there isn't much more to do to it. 75hp/L from an NA motor is pretty good. (M5 has 79hp/L) so there really isnt much room for improvement without going to forced induction or making the motor rev higher (which decrease driveability as this is a heavy sedan with an automatic) . the only thing you can really do is mod your drivetrain to keep you in the powerband. you can do this to pretty much any car.

 

Well I didn't do the LSD (yet) but the TC was a great buy in my opinion (and that of everyone else who has done it). The car is just a lot more fun to drive. For me it's not about 0-60 times, it's about how much fun is the car to drive.