Jwconeil

If the backside of the hood is a high pressure area, would it be more beneficial for the venting to all be in the middle and front of the hood, similar to the novel hood, instead of the seibon?

illwillem

To an extent. Venting up front middle is going to be better for sure. I'm more talking about stagnation right where the window and the hood meet. Sometimes old hot rod guy and ricers put stand offs on the rear hinges of the hood to 'extract' air. That is actually doing the opposite of what they intended. One of the very first things i noticed about the ISF was how careful the engineers worked to smooth all of the front panel transitions. A great example you'll notice on your car is where the hood dips to meet the wiper cowl and they sit almost flat against each other. This was done very deliberately to reduce drag and raise the top speed.

This is something you have to do yourself on other car if you plan on smoothing the airflow for drag.. here another racecar of mine..


In these CFD rendering you'll see the bottom of the windshield the air creates a stagnated bubble that slows flow considerably





I would say the Seibon hood is similar to the ACR hood in that it has the vented slats sit far enough forward that you still get venting flow over the headers (which is big for heat) and still helps in under hood pressures. its just not ideal for the pressures im cramming into my bay from the seal ducting I have built into the front.

FNSSESPORT

The selfishness in me is glad you still need to make tweaks, Im going to miss this build when it’s over!
-R

illwillem

Oh, have no fear- this will never be finished unless I stack it into a tire wall. Fingers crossed that doesn't happen.

So I have been preparing for the new scoops on the hood (still waiting for them to show up) and have been thinking about what I need to do to make this hot air evacuation more efficient. The obvious step is to clear the air from obstruction on its way out of the hood- I started lookin around and found a few interesting things, Seems that Lexus had a similar thought when they were building the CSS-R's. You'll notice that they notice that the engineers moved their expansion tanks from on top of the radiator fans to the battery tray as its a MAJOR flow blocker.

(Props to Meurz for the pics)



I recognize that Carbing "reservoir tank" as I used to have one on my old s14 drift car. For that tank you need a low pressure side flow from the lower radiator hose and the upper flow from the stream port on the upper nub off the radiator.


Problem is the stock set up has a hose also coming off the t-stat housing and going into the oem plastic bladder. there is another port for it available on the Carbing reservoir but as you can see its blocked off. I also wonder if the CSSR ISF's are using a Y-pipe to tap into the lower rad hose or if they are pulling that water from the t-stat housing...



I bought parts to replicate the CSSR coolant set up but I have to take a look though the service manuals too see the flow of the coolant and figure out if i need to run the y-pipe like the instructions or just tap into that t-stat outlet.

I do find it strange that OEM Lexus set up uses a plastic jug as part of the pressurized coolant system and there is no over flow. Those Carbing tanks are pretty small, like around a qt.. so im wondering of they'll have enough room for expansion, this is probably why you can see an overflow bottle stuffed into the fender to trap then siphon the water back into the system as the pressure equalizes. One of the main benefits to ditching the coolant bottle other than increases airflow to the hood duct is that it ditches a plastic failure point.

On my car also got rid of the RR racing AOS. Not only was it also blocking airflow like the coolant bladder- but it was just to small and would fill up after a session on track. Even after letting it cool down id have to handle the hot oil and risk dripping the thumb screws into the seal engine bay. I'm going to be moving this to another spot and replacing it with a bigger tank that i can either use a petcock valve to drain when i get home OR an extraction pump to pump it back into the oil filler after the first runs of the day.

First session after the car has sat a while ill throw away the catch can content, but all sessions after the oil has been brought above boiling a few times itll be safe to recirculate back into the motor and not waste 1/4-1/3 a qt of expensive oil.

WillAP1

Sorry to go kind of off topic but this first part of your post got me wondering... does someone at your level ever buy track insurance (on any of your cars)? Any thoughts on it in general? My local track has no walls and is usually run in a config that is fairly low speed (for me at least) so I don't usually bother... but I've been considering stepping up to some bigger/better tracks and have been contemplating this.

Jwconeil

I had this same question. I’m about to take my 50k plus investment on track, which seems a little scary.

Hardrvin

Wondering if you’d get some benefit from modifying the aero built into the hood. Sounds like you have a lot of knowledge yourself, but there’s some interesting testing in a tunnel from these guys.

https://racelouvers.com/

illwillem

Yes that's the plan. I personally don't like the look of aluminum stamp vents so I'm having a carbon 'waterfall' vent made that i will pair with some recessed carbon louvers. I actually probably wont be using the current carbon hood anymore since the new drop vent placement may interfere with the built in side vent strips in the seibon hood. I have a spare hood that I'll try and graft the stuff onto in a way that hopefully wont look cheap. My other option is to buy the Novel hood, which i almost did until I saw the wait times. I'll see if I can get this custom one looking halfway decent. Hopefully I can, for the cost of the parts I ordered im more than halfway to the Novel hood. I just need functional for now and will worry about permanent solution when i see that its all working how i want it.

I did a lot of cutting and moving of stuff last night. Did a deep dive on the coolant flow and have a few ideas of what I could get to work as far as moving the pressure canister only using OEM ports. I'm sort of at a cross roads on the two best, but different, options of where to pull the flow from. I'm going to wait for all the parts to show up so I can base my decision on the actual parts in hand. Ill post more on that later.

As far as track insurance, no, i don't use it. Depends on the car and track i'm driving though. If I were borrowing a friends Mclaren at Lime Rock and it was a 50% chance of rain, id look into it. Here at the tracks in California i typically don't. You gotta be comfortable with your own decision to be on track with or without it. To be honest i more worry about some trackday neophyte in a over powered car that's convinced someone he belonged in the advanced run group run into me. I have seen this scenario happen over and over and over again. This is exactly why i mostly choose to drive with reputable organisations and people I know and trust. Heavy traffic track days just aren't worth it.

illwillem

So after figuring out that I wanted to move stuff out of the way of the soon-to-be hood vent, i had to find somewhere else to put it all. Problem with the ISF bay is there isn't really a lot of room for anything to move. Also, coolant fillers typically need to be at the highest point of the engine to prevent air pockets and for bubbles to get stuck when bleeding the engine. I took a page out of the CSS-R and decided that I would put everything where i currently had the battery. Doing so also meant that Id get a chance to rebuild some of the battery cables and rerun a kill switch inside the car.

I needed to find a spot for the battery that wasn't going to limit where i could load stuff in the car. Having exposed positive leads getting bumped by coolers and tool boxes is a recipe for bad stuff. I decided I'd install it behind the cage 'strut bar' and the rear bulk head but I also wanted it to stand off a little.

I had a set of roll bar clamps that had to be modified but would be perfect for this.


I trimmed a piece of 1/4 pressed carbon fiber our of some material i had and bolted the battery box to it. I then stuck a thick rubber sheet under it for vibrations and bolted it to the roll bar.



After that i built cables and ran them to a charging terminal and a body ground that i tapped and lugged into the rollcage foot pad.





I then ran a 0 gauge the cable down the passenger side to a spot in the dash that was previously occupied by the passenger knee airbag infiltrator. I had to be careful on routing so that the cables and ends wouldn't come in contact with anything in the event of a crash. I used to have a battery cut off for long term parking in the engine bay but moving it to the passenger compartment made more sense now.


It was tricky, and you have some pretty limited spaces when working under the dash as everything is either curved or wouldn't have sufficient clearance. I ended up finding one spot under the ECM Hub that worked perfectly.

Coming off the other side from the 0 gauge is a 2 gauge cable that goes to a terminal bus that connects the starter and passenger side injector fuse box. Building cables right with the correct glue shrink, compression clamps and boots is comically expensive and time consuming but worth it in the end. Nothing is worst that intermittent electrical issues.


Now I had room in the bay I built a plate out of more pressed carbon and installed the pressurized header tank with a 22psi cap. Because its pretty compact (about 1.25l) I also added an expansion tank that i drilled and nipped so it stays at ambient pressure. If i puke air or coolant out of the radiator cap it will go into the overflow tank via bung at the bottom, the air escapes but the water is caught. Once the coolant cools and the system is depressurized it pulls a vacuum on the expansion tank and draws the expelled coolant back into the system. This is a really good way to be constantly bleed the coolant of cavitated air. The red hose is temporary until I can get more black, I like to keep things oem looking of possible.


The hose on the right goes to the steam port off of the radiators upper tank. I took a while to settle on good routing and cushion clamped all coolant hoses to keep from chafing.




I also removed the fans and trimmed the fan shroud to let more air out. Doing this will lessen the efficiency of the fans while stopped but I am really only concerned at the moment with the car at speed.


Still waiting on other parts, should have some more work done as soon as they show up.

kos

iTrader: (1)

Keeping very busy

illwillem

So I found some interesting reading in the FSM.


Verified that ELSD isn't shut off with the VSC. This makes sense I guess. VSC is holistically looking at every perameter- steering angle, brake pressure, wheel speed, inertia, etc and affects different systems according to some data table. With this stuff off you'd probably still want the help from the electronic LSD if you don't have an upgraded clutch type. If you have an upgraded LSD you, for sure, don't want any intrusion of the rear brakes. After looking in the FSM there is a section on attaching the car to a dyno and its says the only way to turn off the rear brake "LSD" is to put the car in 'test mode' with the tech stream software or complete the sequence of whats commonly referred to as the pedal dance. I actually read in a few places that the "pedal dance" is something Lexus doesn't want you to know about and is not in the manual... actually in the introduction chapter on page 20 of like 5000. :shrugs:


It was already hard enough for me to remember to put the car in sport mode and hold the VSC button for 3 seconds while not moving.. now i gotta input a cheat code before every session (eye rolls). Only partially kidding.

Every so often you are made to wait on hot grid for 5-10 min before a session while a car is towed off track or something. I usually don't keep my car running in these cases in an effort to lower IAT's and keep from heat soaking everything. In a perfect world you'd get a "1 min" warning before release, but that in practice never happens and your left struggling to do all the sequences necessary to turn off all the nannys and not block the pit lane.

To help with this end I wired up two momentary (NO non-latch) buttons. One is connected the the brake pedal sensor switch (NOT the brake pressure switch) and the other is attached to the e brake ground switch. After digging though the schematics for the traction control ECU I realized there is a open fault circuit integrated in the ECU for the ABS pressure. I found it the best bet to jump the pedal voltage at two of the wires at the pedal switch itself and not feed the signal directly to the TC ECU just to be safe. Seems to be OK after some testing, the brake input signal going to the TC ECU without the corresponding pressure signal from the Master cyl has not thrown any codes in techstream so looks like I'm in the clear with this method.
The parking brake is a simple 12v looking for ground that's also being read by the traction computer. With these buttons and can VERY quickly, while strapped in with helmet and gloves on, disable the rear ELSD. I just wish it shut of the VSC too. The cheat code only works for the ELSD and won't effect VSC, that still need the push and 3 sec hold. The only other thing I want to make sure im in the clear with is that Test Mode does not ALSO shut of the ABS. They seem to be a divorced system but ill have to test it when the car is back on the road.


While I was at it I decided to remove the e-brake pedal. I don't like these floor pedals in track cars.. its in a really bad spot and in case of a wreck you asking to brake an ankle. I pulled this and all the rear drums and cables out. pedal is almost 4lbs as well as 4.5 per brake shoe assembly. Add other 3lbs for the cables brackets and springs. I'm probably eventually going to look into adding a line lock on the hydraulic system to just clamp the calipers to rotors when towing the car. ADs for now ill just used extra chassis straps when on the trailer like I do anyways.


I also bonded on some wicker flaps to help with the air extraction on the skirts. Any little bit helps.

WillAP1

Yeeeeeeep. Pretty annoying. While not widely known I've seen it discussed several times on here. I fall in the same boat but never do the pedal dance... just too much work so I just use the 3 sec button hold method... but still often forget to turn it off til I'm already moving... I hate it. Might have to consider implementing a system similar to yours. I really doubt it would mess with ABS as I've heard of many people using this... but yeah definitely test it out and let us know.

I wonder how difficult it would be to take your idea one step further and wire up a simple board to do the sequence with a single press of a button? Would be a great product for someone to develop but no idea if the demand is there.

illwillem

Yeah, agreed. I was actually looking into writing an Arduino program to do exactly this. It honestly wouldn't be to difficult or costly parts wise once you isolated the signals that needed to be sent. A one button push that would do the pedal dance and turn off all VSC sounds like a winner. I had done a similar thing on my NSX for the TC memory but that was like sticks and stones in comparison to what Lexus has implemented here.

lobuxracer

iTrader: (2)

We covered all this stuff a long time ago. Pedal dance does kill VDIM. There is nothing you can to do turn off ABS short of removing the ABS actuator assembly from the braking system. Also can't stop EBFD and Brake Assist. EBFD is Electronic Brake Force Distribution (electronic brake proportioning valve). Brake Assist assumes you don't know how to use the brakes on the car and under certain circumstances will apply more pressure for you again using the ABS actuator.

Pedal dance is in the service manual for sure, I've seen it there. This same approach is used even with the electronic parking brake in the GS F. Same process, just using a switch instead of a parking brake foot pedal.

Way back in '06 when the first of the 2IS models came out, there was no VSC off switch, and the only option was the pedal dance. They changed that in '07, so the guys who were considering building out a device to plug in and perform this action scrapped the idea. Not rocket science by any means.

I have tracked the car with the open diff after the pedal dance. The eLSD makes a big difference - I was driving out of turn 8 at CMP and the engine tached out, hitting the rev limiter like I had a bad clutch. That's when I figured out the OEM front spring rates were insufficient because the inside rear wheel was coming off the ground. I only needed one session like that to convince me I needed:
1. More front spring
2. Clutch type LSD
3. Never do the pedal dance until 1 & 2 are already completed

illwillem

What I need a Matrix like device to download everyones been-there-done-that lessons directly into my brain. It would save me a lot of time flipping through the FSM. You're dead on about the eLSD, I had the same exact experience going about 6 seconds faster on track after I just let the car sort out the one tire fire wheel spin. Now with the clutch type in and all nannys off i'm curious to feel the cars natural dynamic. It was already so easy to drift around only using the eLSD, surprisingly so. Good to hear about the ABS staying on in Test Mode that would be a huge bummer to lose on track.