Sounds like you all need a full cage as the body twists so much on its own is stock form. But seriously those braces I posted in the full underbody shot should keep the suspension in check. The upper A-arms have a fraction the load of the lowers. That said the arms themselves likely eat up some response as they are pretty flimsy.
I suppose for pennies on the dollar one could box them in, powder coat and add poly to crispin up input...


C, I am surprised your rear diff only has front solid mounts. Has it been that way since the LSD installation?

 

I don't believe the front end of the 2IS platform (IS250/350/F) has that much chassis flex which led to the RR brace being so beefed up. I believe the original RR brace design was made for the RC-F which does support another mounting point along the firewall which allows for the triangular brace design. Since the IS-F does not have the same mounting points on the firewall as the RC-F, the design of the brace was modified to not include the mounting portion by the firewall while still retaining a similar look.

Though there is no TRD branded front tower brace for the 2IS, the Tom's version is available which is kind of like TRD.

Regarding the braces that I feel have the most impact with improving responsiveness of the chassis from steering input, here are my top 3 in order:

1) F-Sport Rear Under Chassis Brace: Easily a night-and-day difference in reducing the polar moment of inertia with steering and chassis responsiveness. It's easy to see why this was the sole chassis brace offering from Lexus USA/TRD USA with the F-Sport Accessories package.

2) Four Point lower tie brace: Another excellent chassis brace to further improve steering responsiveness from the chassis. It ties the lower control arms to the chassis.

3) Front Tower Brace: As much as I have been skeptical about putting a strut bar on a vehicle with a double wishbone suspension over the years, I found having a solid single piece brace does provide additional improvement with steering responsiveness and assisting with the distribution of load when initiating a sharp turn. It should certainly help more than the three piece strut bars with pivot points.

It has. I believe I was one of the early adopters within the 2IS community (ISF included) for the OS Giken TCD back in 2013. IIRC, there were no upgraded differential poly bushing kits being offered by Figs or any other vendor at Club Lexus so I was unaware of recommended upgrades to the bushings at that time. When I went to Titan Motorsports for the LSD install, the shop owner recommended that I install a pair of solid aluminum diff ear mounts that were used for the MKIV Supra differential upgrades and would help eliminate wheel hop ( http://www.titanmotorsports.com/sodiearmof.html ). It sounded good so I added those to the install.

The rear end feels stable and I don't notice any wheel hop when I launch the car from a dig so I'm guessing the more critical bushings to upgrade are in the front (though it's still recommended to upgrade both the front and rear now that diff bushing kits are available).

 

On the topic regarding suspension tuning and setup, I saw this very interesting video earlier today with puts an E39 M5 on a front suspension testing rig in order to put the components and tires under extreme stress (which appear to be under track conditions based on the acceleration, deceleration, and cornering behavior):

 

Someone is selling the RR on Ebay modified somehow. Not really sure. I messaged the seller did it really improve handling, and did the chassis flex that much. Response I got was a video link on how strut bars work.

 

^^
That used RR strut bar doesn't look as purdy as the ones shown on the website (it's also missing the carbon fiber inserts as well). For the price though, it's not a bad compromise. However, I do recommend getting the F-Sport rear under chassis brace and/or the lower four-point tie down brace before getting a strut bar as those are more effective based on my observations.

On a side note, the mod bug has begun with the IS350C. I won't post much more on this car as I don't plan on adding an extensive mod list to the convertible like with the IS350. However, the stock vacuum cleaner intake sound of the factory setup was driving me nuts (too sedated) so I went ahead and installed both the F-Sport lower intake box as well as the 3IS350 F-Sport intake pipe with Sound Generator that I had laying around the garage.

It's a simple mod using OEM parts to maintain the whisper quiet setup at lower RPMs and adding a bit more growl and rumble at the higher RPM range. Here's are a few pics of the install process (the IS350C only has 35k miles so the engine bay is still sparkling clean):











EDIT: On another side note, when I popped open the intake box, I noticed that the engine air filter was a completely different design. Upon further research, it turns out that someone installed the engine filter from the 3rd Gen IS350 into this 2nd Gen IS350C. It still fits but it's a tight fit. I'm debating on whether or not to keep this clean filter even though it's not for the correct generation Lexus IS.




As this 2014 2nd Gen IS350C is of the same year as when the 2014 3rd Gen Lexus IS model rolled out the production line, I can foresee this being a problem whenever I need to take the car in for service (installing wrong parts from a different chassis). It's probably best that I tell a shop to look for parts pertaining to a 2013 MY in order to minimize confusion and errors.

 

@redspencer Thanks for the info!!!

 

With the summer heat continuing to make each day feel muggy in Florida, I've been hiding mostly indoors. I did, however, make a few random short videos on my YT channel to pass the time until things get a bit cooler outside for more AutoX/HPDE events. Till then...

EDIT: BTW, I've officially renamed my YouTube channel to Redspencer IS350

 

Man now that I'm looking for a lower F Sport air box. There seems to be none available. A few months back I saw one on Ebay. I should of snagged it while I had a chance.

 

I still have the box with the part number if it helps with your search (you can try sites like mylparts to see if it's in stock).

BTW, according to the warning on the box, the intake box may cause cancer or reproductive harm.

 

Thanks,

Just placed an order on oemvehicleparts.com. As I'm also looking for a little more noise up front. My HPS intake pipe does a bit good, but I feel it needs a little more throatier sound.

 

Last thread to read before taking off and that "touch" of humor is Appreciated after this day. First time I chuckled, maybe?

Take away is CA does not condone explicit air box activities as you may be altered! Lol

 

As they say, laughter is the best medicine but if you laugh for no reason, you need medicine.

All this talk about cancerous F-Sport Intake Boxes had me wanting to do more datalogs which I have been this week. I'm currently testing to see if how much of an impact the hole in front of the F-Sport Intake Box has on both IATs and recorded MAF g/s.

I've already recorded several days worth of data with my current setup and I plan on swapping out the F-Sport intake box with the stock OEM intake box that I have laying around from the IS350C to see if the enclosed box has a noticeable impact to peak air flow and IATs.

The current Florida weather has consistently been in the low 90s with max humidity during lunch time when I did my recordings and should remain the same next week when the intake boxes are swapped out. I'll post the results soon after so we can see if there are any performance benefits or penalties with the additional intake hole from the F-Sport Intake Box....

 

Since I'm on the topic of datalogs, I figure I would consolidate most of my previous datalogs from back in summer of 2018 and January of 2019 for those that are new to my build thread this year (and for future reference with intake pipe discussions).

Here is a collection of datalogs I recorded when I was testing to see which of the two intake pipes (JoeZ Intake Pipe vs 3IS F-Sport Intake Pipe w/ Sound Generator) provided the highest peak MAF g/s recording (intake air flow) during both summer and winter testing.

The end result was the JoeZ intake pipe consistently having higher recorded MAF g/s readings compared to the 3IS F-Sport Intake Pipe during similar weather conditions.

1) Summer 2018 Recordings

- JoeZ Intake Pipe Datalogs:







- 3IS F-Sport Intake Pipe w/ Sound Generator Datalogs:






2) January 2019 Recordings:

 

As I mentioned in one of my previous posts (#687), my current plan is to datalog the changes in IATs and MAF g/s readings between the stock OEM intake box (enclosed) and the F-Sport lower intake box (with the additional intake hole in the front). I'll be recording several days worth of data at approximately the same time of the day and the same outside temperature to ensure consistency with the data and the results (and also means plenty of WOT pulls for me).

For the longest time, we've been hearing that the only benefit of the F-Sport intake box is the increase in sound from the additional hole but no increase in performance (with no actual data to back up these claims). The intent of the datalog comparison is to see if there are actual performance benefits to the F-Sport lower intake box (via the peak MAF g/s readings after a multitude of WOT pulls). I've already collected several days worth of data with the F-Sport lower intake box so now it is time for the swap to the OEM enclosed intake box (the question is whether or not it's considered to be an upgrade or downgrade....):

1) Getting ready to make the swap back to the OEM lower intake box (donated from the IS350C which recently received its own F-Sport lower intake box)




2) While I was making the swap, I decided to wrap the end of the intake snorkel with multiple layers of electrical tape to better seal the intake box from the engine bay heat (as the original seal is completely flat and/or deteriorating away)




3) OEM lower intake box is secured (not sure if it was worth sweating in the garage)




On an unexpected turn of events, my car battery reached the end of its 3-year lifespan (it only had a voltage reading of 10.5V). I managed to swap out the battery to a fresh one but now my Knock Correction Learn Value (KCLV) has gone from a strong 23 to the default 15 (which will drastically reduce peak ignition timing advance).


BEFORE




AFTER



This is both a blessing and a curse because the lowest KCLV reading of 15 will also give me a brief opportunity to record the peak ignition timing advance permitted from the ECU while it is at its most retardedest (yes, I made up that word ). From previous datalogs (and a KCLV over 20), my peak ignition timing is at 30 degrees (on rare occasions at 31 degrees) so we'll see what it shows when the KCLV is at its lowest settings.

 

Yeah I hope there is some positive gains in the lower airbox. I'm still waiting on my order. Slowest shipping imaginable.

I used velcro I found at work. For the seal on the snorkel. Still going strong after a few months. Most of the stuff I have used. Would loose adhesivness with in a couple of weeks.