When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Which brake pads are you running? Had my ISF on track for the first time this past weekend. Ran G16 pads all around, in the trac off mode (08 so open diff for now so no pedal dance for me), and if the VSC intervened, I got some pretty violent action. I suspect the ABS/VSC calibration was not keen to a high torque pad. Wondering if anyone else has experienced similar.
otherwise, car did as expected. Though for being stock, I did see the oil and water temps start to rise despite only being 80 outside. Took about 10~15 min of pretty hard lapping to get there, not a ton of traffic.
I have been running Porterfiend R4-s pads but have also driven on HC+ from Project Mu that are decently grippy but I didn't have anything abnormal as far as VSC operation. I actually just placed an order for R4 (race) pads from Porterfield since during the last track day the r4-S(street) compounds didn't feel up to the task anymore. Ideally i could find some WinMax w6 but they are not shipping to the US at the moment. I ordered both front and rear in the same compound and am going to see how the car feels, most car are ok running the same front and back but some cars just like softer pads out back. It depends on the the hydrolic bias of the system as well as the front and rear split weight of the car. I can always swap the rear pad back to for something softer if needed.
When you say violent action, how do you mean? The E-lsd should really only be dragging a pad, i wouldn't think it would be doing it hard enough to get any bucking or anything- but then again i'm not familiar how grippy or how much initial bite the g16's have. You can try and swap pads on only the rear left or the rear right with something stock, then see if it happens on the Lefts or Rights that correspond with where you have the aggressive pad installed.
Which brake pads are you running? Had my ISF on track for the first time this past weekend. Ran G16 pads all around, in the trac off mode (08 so open diff for now so no pedal dance for me), and if the VSC intervened, I got some pretty violent action. I suspect the ABS/VSC calibration was not keen to a high torque pad. Wondering if anyone else has experienced similar.
otherwise, car did as expected. Though for being stock, I did see the oil and water temps start to rise despite only being 80 outside. Took about 10~15 min of pretty hard lapping to get there, not a ton of traffic.
I wonder if part of the histrionics was your heavy braking and otherwise stock car with worn out suspension. The front springs are so Undersprung that they really load up on decel (Especially from 125 mph). Your car was also sitting lower than mine, despite us both being on stock springs. Maybe the suspension is just really tired?
I rode along with Hardrvin in his advanced class sessions. It was a lot of fun. Very good driver. The oem seat gave me a workout trying to stay in it. Now I Truly get why guys that track get different seats.
I had nothing like that with Carbotech XP-10s in the back. I had very little rear pad/disc wear from track use. Those XP-10 rears are still almost new thickness after a half dozen track weekends.
If it was in brake zones while on the brake pedal only after a long straights it could possibly have something to do with the brake assist as opposed to something jerky happening on throttle mid corner when the eLSD senses wheel slip. I'm going to look it up now in the FSM (actually been meaning to for a while) but the car has a brake assist whereby it senses large input on the pedal and by some programming magic if its within threshold X assumes your going for a panic brake. I believe this has something to do with the ride height sensors that are piggy backed on the sway-bar endlinks. There may be something to do with excessive dive causing the panic brake system to freak out. Ill see what i learn and if it can be disabled and post back here.
If it was in brake zones while on the brake pedal only after a long straights it could possibly have something to do with the brake assist as opposed to something jerky happening on throttle mid corner when the eLSD senses wheel slip. I'm going to look it up now in the FSM (actually been meaning to for a while) but the car has a brake assist whereby it senses large input on the pedal and by some programming magic if its within threshold X assumes your going for a panic brake. I believe this has something to do with the ride height sensors that are piggy backed on the sway-bar endlinks. There may be something to do with excessive dive causing the panic brake system to freak out. Ill see what i learn and if it can be disabled and post back here.
If you find something, please post. I've been all through VDIM on the IS350 and IS F and found nothing about the parameters it uses to invoke Brake Assist. I do know high mu pads will overrun ABS for sure. I've been able to momentarily lock my wheels with the HC+800 pads before ABS could react. Never on track, the only way to invoke it is to brake like a moron and slam the pedal hard and fast, but even this with the OEM pads won't lock wheels. It definitely does lock with high friction pads.
So I took a look in the FSM. there is really not a whole lot of anything concerning the panic brake switch other than error thresholds and parts location. There is a switch diagram and plug schematic of the wire path to the traction control computer which would make it possible to unplug the switch and build some sort of relay circuit to keep it from triggering if someone were so inclined, I'm not yet convinced something like that is needed ATM. Looking into it further- I realized there is a data output stream in the CAN signal being read by the ecu (and logged with my data logger) that is labeled BBK POS but does not correspond to any pedal inputs i've been able to do while the car is stationary in my garage. I'm actually now wondering if this signal is for the panic brake switch. Whoever wrote the Lexus ISF profile for AIM had to specifically choose which CAN addresses were to be logged. This means the whoever paid to have the ISF profile made by AIM likely specifically requested this input for some reason. There is also a Shift Mv input and a PPS VTS input that i cant for the life of me figure out what for. I built a new profile to log all these inputs along with the rest of the 'more useful' typical ones. After my next track event i"ll circle back and see if i can match up any potential triggering of the BBK POS with spikes in brake pressure and/or high longitudinal G events.
In addition to the laptop work I added some brake scoops off a 911 gt3. I had to chop them up quite a bit, and its a real tight space they have to sit, but this should scoop air into the wheel hub and make some small difference.
I also added some carbon spats to the front and rear wheels and bonded a small gurney flap to the main hood scoop to help create a larger low pressure bubble to draw the heat out at speed.
As of now i'm just waiting on some brake pads to be made and shipped. Hopefully they make it by the the 27th, which is my next scheduled track day. Should be an interesting one, i've made quite a few changes to the car and hopefully everything works out. Track event will be at Buttonwillow Raceway, which is basically the benchmark track in socal. I'll be able to tell how the car stacks up against everything else in the first few laps. I can't wait.
As of now i'm just waiting on some brake pads to be made and shipped. Hopefully they make it by the the 27th, which is my next scheduled track day. Should be an interesting one, i've made quite a few changes to the car and hopefully everything works out. Track event will be at Buttonwillow Raceway, which is basically the benchmark track in socal. I'll be able to tell how the car stacks up against everything else in the first few laps. I can't wait.
Enjoy. Would like to hear how your revamped ISF compares to your other cars!
Appreciate the feedback. Sounds like I've gone the most aggressive regarding pad selection here. Lobuxracer, I've run the X10's on another car, and these are quite a bit more aggressive. I wouldn't have thought to try the R4s for track on a heavier car, impressed to hear they held up for you.
It's been weeks now, and just wrapped up a 24 hour race, so my brain is a little cooked on the details. It would do it under hard braking and overly aggressive exits. Not sure that I got it overly loose mid corner such that VSC would step in to see if it exhibited the same behavior then. I hadn't considered the panic stop logic, interesting thought.
Hopefully have the OS in before I take it back out again, and I can try pedal dance on/off and see if that clears it up.
I'll start my own build thread and post video there once I get to it. Thanks again.
The ISF looked less planted and more tail happy. Is that an LSD model?
From the sounds of it, it's an open diff unit. KWv3s is even worse. They're not set up for track work from KW, and they're not particularly good from jump. Fine for street use if you want a softer ride though.
08-06-20, 07:16 PM
