JBrady

Here are the 3 parts ready to be welded

JBrady

Here is the 3 parts welded on the left showing the D shaped nozzles. Notice this is a bit of an oval shape. The 2.50" open section should be shaped to fit this oval before that is welded together completing the Nozzle Y pipe.

JBrady

Here is the assembled Nozzle Y pipe from the outside there is not indication of the center divider. Notice the gentle angle of the merge.

JBrady

Here is the view looking in through the 2.50" pipe. Notice how smoothly the transition is accomplished.

I hope this helps a lot of people to build great sounding and great performing exhausts. DM me with questions and I will try to help.

JBrady

One more note. Do not bother with aftermarket cats. The OEMs flow just fine

joemg

Thank you so much for posting all of this!


Do you think there would be much gain for me to replace my existing (a few posts above) front Y with this one? I've already redone my midpipe, my exhaust shop is going to think i'm insane if I go back a 3rd time, lol. Also, I have 2.25" pipe coming from the cats now.



I have the stock cats, I did the math on them a while back and you're correct (obviously), they're more than ample for our N/A application.

digitatc

We just got some great information regarding the exhaust system, and it should be added to the sticky notes.

JBrady

joemg, yes, I do think you will pick up torque, throttle response and likely fuel economy if you add both 2.125" from the cats to the nozzle collector as shown. As I mentioned the very first set of headers for the GS400 I donated a 2.25" to 2.50" Y pipe and it lost torque. This has to do with exhaust velocity and directional inertia. You want the highest speed exhaust at the lowest engine RPM that still allows for full power flow with low restriction. The stock Y pipe has 1.97" (50mm) pipes from the cat outlets to the stock Y pipe. Many people have made near 400hp supercharged through the stock Y pipe. The 2.125 to 2.50 flows more than stock but retains the stock response. The 2.25 to 2.50 slows the gases out of the cats (relative to stock) and the speeds them up with a more aggressive ratio causing back pressure and a loss of internal velocity. That is what bcsc400 originally installed in his system on this SC400. He did not make that mistake again with his SC430.

joemg

Does anyone know a good place to get this Y pipe made? My local shops don't seem to do much 2.125" and mandrel bend solutions isn't replying to my emails, I'm wondering if they have closed? I have half a mind to just go back to the stock Y pipe (minus the 3rd cat), but I don't have mine anymore and the cost of the ones on ebay are practically as much as redoing the Y pipe with 2.125".

joemg

I emailed 4 different fabrication places that specialize in Y pipes and the like and got zero replies, including mandrel bending solutions which appears to be out of business now. I can only imagine the pandemic was a death nail for these guys with all the supply chain issues and materials inflation.

I found a OEM Y pipe for a good price... I'm never going to make even close to 400hp with my naturally aspirated engine so I don't see the point in wasting more time/energy into this.

After 3 pages and to much money, here is the TL;DR for anyone who wants to do an exhaust on this car and isn't going forced induction (ie. pretty much everyone):
PPE headers > stock cats > stock Y pipe with 3rd cat delete > 2.5" pipe > 2.5" straight through resonator of your choosing > good quality Y pipe > dual 2.25" pipe > 2.25" mufflers of your choosing

If you have money to burn or want to do a high hp build, then obviously the nozzle Y pipe Jbrady was kind enough to detail for us is clearly the way to go.

After I get the pipes swapped I think I will probably do 1 more dyno run to see what the final numbers are since they were so terrible when I had done it with the X-pipe setup. I'll share my results.

digitatc

did you get the OEM y-pipe yet?
I got the mega y-pipe (without the 3rd cat) I think it lost some torque, but it sounds louder. The megan y-pipe is a little bigger in diameter compare to the OEM one.
I really don't know the torque lost is due to the bigger pipe or removal of the 3rd cat.

At this point, you should just enjoy the car as is, and buy the LC500 later.

joemg

Just ordered it today.

I think you lost torque because the megan Y pipe is dual 2.25" tubing which is what I currently have.

Once I install the factory Y pipe, that will likely be the last performance mod for this car.

joemg

Ok, so today I put back the OEM Y pipe (minus 3rd cat) and used 2.5" pipe to the rear "Y" which splits into dual 2.25 mandrel bent pipe. Jbrady was not kidding, it feels SO much more responsive, the dual 2.25" right out of the cats were too big and the "Y" pipe I had definitely had an inferior design for this engine.

I could have saved a bunch of money doing it this way from the beginning. Unless you're going forced induction, keep the stock Y pipe and just replace the headers and everything after the "Y" in the stock Y pipe.

I have scheduled a dyno run for later in the week.

Here is my disappointing original dyno sheet from the true dual 2.25" X-Pipe setup.
I was averaging about 251hp/235tq at the wheels. I'm willing to be that the torque figure will be substantially higher than the hp figure this time around.

joemg

Ok, here are the results. Jbrady knows what he's talking about.

I didn't average the run in red because they said it was a "bad run."

I went from averaging 251hp/235tq at the wheels to averaging 252hp/249tq. So a gain of about 15tq by going from a true dual 2.25" X pipe back to the factory "Y" (minus 3rd cat) into 2.5" pipe before splitting to dual 2.25". (91 Octane for all runs)

This is pretty consistent with what spdrcr771 did with the 2 1/8 "nozzle Y" setup, and I'm assuming from his TX location he had 93 octane if that matters:
https://www.clublexus.com/forums/sc-...-dyno-day.html

The car feels so responsive now, I didn't understand until now how dramatically the design of an exhaust can affect the power and throttle response. Most cars have "off the shelf" exhausts where all this R&D is done already, so I never really had to learn about it.


Here is the full powertrain mod list (excluding suspension):
Modified OEM airbox (smoothed interior and hole cut in the front)
Blitz drop-in air filter
Modified intake tube (removed accordion section and replaced with smooth silicone coupler)
Extrude honed intake manifold
PPE Headers
OEM Cats & Y pipe (3rd cat removed and replaced with 2.5" pipe/resonator)
Dual 2.25" mandrel bent to the rear
All4swap remapped ECU


TL;DR a long way to go for moderate gains. If someone was to ask what I would recommend for the best bang for your buck in terms of power, I would say modify the stock Y-pipe and everything behind it. If you have money to burn, go for the PPE headers but they're expensive and installing them is a big job. Get the remapped ECU. Spend the rest of your mod money on big brakes and suspension. Aside from the ECU, the big brakes and suspension mods transformed this into a much better car than it already was.