Gaffgarion

Good afternoon all,

I am a new member that has been browsing the boards without membership for some time. I am an enthusiast of the GSF, as the ISF and LFA are what inspired my passion for cars during my adolescence.

I do not currently own a Lexus GSF, but plan on buying in the next 6 months or so, unless I find a good deal sooner. I have been contemplating modifications I would like to implement when I do finally pull the trigger, and one that has been gnawing at me is the potential to change the final drive ratio.

It is to my understanding that the RCF Track and Fuji editions also have their final drive ratios changed in order to receive their claimed 0-60 times. Because the GS and RC are not too dissimilar in their architecture, I was curious if it is possible to change the final drive ratio of the Lexus GSF?

While I do have some basic to intermediary level comprehension of vehicles and how their drivetrains work, I am not certain this is possible with just a parts swap. Would someone enlighten me on whether or not this is possible, any complications or caveats, etc.?

My ultimate goal is to build a “better than stock” car that stays naturally aspirated. I understand RR Racing does some awesome tunes and they’re pretty reliable, but it’s not in the spirit of the drive in my opinion and therefore not for me. Instead I’d rather look at some options like this or perhaps different cams, internals, etc. to help the car perform better in these capacities.

Thank you for your time, hope to hear from those more knowledged and experienced than I.

lobuxracer

iTrader: (2)

A tune would be the most effective approach after exhaust. Intakes are mostly noise or they allow a lot more dirt than the OEM filter.

Changing final drive will get you to redline in first a little quicker. That's all you get.

"Better than stock" can mean lots of things. What it definitely does not mean with the 2UR engine is aftermarket support. There is very little available in the aftermarket for the Lexus V-8 because nobody is racing them in any competitive series, and the owners generally are not gearheads looking for more than what they can get with bolt-ons and a tune. Cams just don't exist for the IS F, RC F, GS F, or LC500, or even IS500. You'd be on your own with (maybe) a regrind. There are pistons and rods, but there's not much to be had with that unless you want to do a full build, and just blueprinting with a tune would likely be a lot of money for not a lot of improvement (depending on the individual engine.)

If you want to spend a pile of money there are options, but I mean a pile of money on parts and labor to set up the engine with a bigger bore, bigger pistons, port work, oversize valves...the usual stuff, but then you're back to a crap shoot with cams again. The only other option with substantial power gains is supercharging. Not quite a pile of money, but definitely getting there.

It all comes back to the same old song - Speed costs money, how fast do you want to go?

Gaffgarion

Thanks for the response! I appreciate your thoroughness. I am painfully aware of the lack of aftermarket support, my last car was a Hyundai Genesis 5.0 R-Spec, a VERY slept on car that was worth every penny at $18k-$20k used. I only sold it so I could start saving up for a GSF, what I call my realistic dream car 😁 Anyway, it had zero support from aftermarket vendors, the best mod I could install was a bay mounted sway bar. It helped with keeping the car tight in corners, but that’s about it.

I’m okay with paying a few grand for shaving a few tenths of a seconds off the 0-60 time. My good friend who is my car buddy has a base 2018 M4, I know they’re totally different cars but I’d like to at least try to keep up! That and a little extra kick in first gear just adds more to the fun.

I have extensively read about getting a tune and exhaust helping increase NA horsepower output, but the gains don’t seem to be that much unless you get better headers. I live in California, so unfortunately non-stock headers would be an expensive endeavor just to get smogged. I used to know a Smog guy, but the key word there is used to 😬

I’m not looking to spend a pile of money, more to the point, I’m just looking for things to do here and there to help optimize the vehicle to its potential within the capabilities of the market.

kukudm

From what I read on the forums, it's about 20-30 hp with a midpipe (secondary cats deleted), a little bit more with a tune. Headers will get about 50 hp with a tune + much improved midrange. I'm in CA too, I personally won't touch a tune yet, as smog places start checking ECU calibration ID, unless there's a way to easily flash back to stock tune (still a hassle with RR as you have to rent the flashing dongle or send the ECU to them)

For a good 0-60, you'll probably also want a stickier tire, maybe try one of those 200 treadwear ones.

I think final drive definitely helps. The latest RCF with TVD comes with 3.13 FD, which is slightly shorter than 2.94 on the GSF. If you can't source a used one, a brand new one isn't cheap though, for how little gain it provides. So, for me, I'd just install a midpipe and get some good tires and call it a day.

lobuxracer

iTrader: (2)

Buying any TVD diff is going to cost an arm and a leg. They're literally 1/4 the cost of the car retail vs. retail. It would be way cheaper to buy the gearset and install it, even if it cost $2k to do it. I've put a Giken spool in my IS F, so this wouldn't be a big deal from my perspective, but if you're paying someone to do the job, it won't be cheap. It's not an easy afternoon job.

skhmund

what midpipe do you suggest? My goal is not power, it’s more so noise, but I’ll take me the power gains if any.

kukudm

Apexi, get non-resonated if you want noise. I listened to some clips, even stock exhaust paired with non-res Apexi was pretty loud. So be aware if you have a catback, it’ll be pretty insane.

Gaffgarion

It’s good to know that even just replacing the exhaust can bring out some ponies! I have seen/heard that, just haven’t seen any solid numbers. I finally found a source that showed the price of a TVD unit and $21k is ludicrous for that, I was expecting maybe $3-5k…I wouldn’t even bother trying replacing the gears myself either without some experience! Better and lighter tires and wheels, exhaust and a tune seems to be the consensus here on the forums.

To get around the ECU problem, I was thinking of just buying a secondary stock ECU unit to “hot swap” when smog time comes around. I’m sure it’s not cheap, but is that the only reason that would hold you back? Replacing the headers would be expensive in labor just to undo/redo once your smog is up; though you’d only have to do that once every three years.

Gaffgarion

I didn’t know that until I looked up a parts supplier, it was $21k! I don’t think I would replace the gears myself, I’d pay someone to do it for me. Where would I start with that? Are there aftermarket suppliers for FDR gears like that company you mentioned?

lobuxracer

iTrader: (2)

No reason to bother with aftermarket. Lexus sells gearsets and they're not unreasonable from Internet sources. Honestly, the hard part is getting the diff out. It's a lot of work. Not terribly difficult, but a lot of work, so the cost gets prohibitive pretty quickly if you can't do the most tedious parts yourself.

Gaffgarion

Good to know! I didn’t realize they did that, I found navigating their parts website a little difficult but I found the items I was looking for. Definitely not cheap, but I intend to keep the car forever so it’s just a matter of time.

designo

iTrader: (6)

Let me get this right.. you are looking at changing the final drive ratio on an 8 speed automatic car with torque converter?

Gaffgarion

The initial idea was to buy the differential from the RCF Track Edition, but after discussing with others here, buying the gears and swapping them would be more realistic(if you can even call it that).

Once I get the vehicle, first mods will probably just be better wheels, tires, exhaust and a tune as suggested here and elsewhere. Moreover, I just wanted to know if swapping the final drive ratio on the differential was possible, since that’s mostly what gives the RCF Track Edition the 0-60 bump.

lobuxracer

iTrader: (2)

Maybe. I'd say the 4034 pound claimed weight for the GS F vs. the 3781 pound claimed weight for the track edition RC F has a lot to do with it too. My IS F with 2.94 gears and a significantly lower power rating accelerates almost dead even with the GS F. My IS F weighed a little over 3700 pounds on a scale at Roebling Road, so pretty close to the RC F track edition. I really doubt you'll see a significant change with a gearing change that small.

Gaffgarion

I agree that the weight savings is nothing to scoff at. That is something I am also looking at, all the way down to lighter weight tires, since unsprung mass is more difficult to move.

However, let me ask this then: why is it a 2018 BMW M4 with 20 less horsepower and about the same weight as a RCF/GSF can out sprint it by half a second? My understanding is that their gearing is more aggressive and shorter, sacrificing top speed in the process. Could just be a transmission tune, could also just be that BMW is under reporting their horsepower figures like they do with the M5, but I am certain that most of their performance oriented vehicles have shorter gears to get those numbers.

I’m fine with sacrificing some of the winding out to get better acceleration, because the Lexus won’t completely lose its character from a change like that. To me, you sacrifice a little to get a little, except perhaps the cost of course 😭 and at the end of the day I’m not trying to chase BMW level performance out of a naturally aspirated Lexus product, I just use them as an example because that’s what I’m familiar with. I still want the Lexus to be a Lexus, which is why I’m not interested in forced induction.