I was answering yet another good PM on what to do about the Y pipe so I am starting this thread as a reference.

I am planning a high flow Y pipe. The stock Y pipe works very well for low RPM response and torque. That "crisp" feeling. I want to keep as much or all of that power and feel as possible while increasing peak flow capacity. No easy task.

This is not easily measured on the dyno either since most dyno runs start above 3500rpm but most street driving is below 3500rpm. Also, feel is not measured on a dyno nor is transient response which is part of the feel but REALLY important for actual performance.

This is similar to the difference between skid pad peak numbers vs. actual time around a race track. Sure, high skid pad numbers are impressive but not very valuable unless your car is faster in actual use. Same as peak horsepower numbers. Great bragging rights, not so great when a "less" powerful car outruns you! Some people may be thinking "no way" but, ah, yes, way, definitely way, happens much more often than people realize.

Lexus sedans are for the most part heavy cars with small engines. 4 liters is 242 cubic inches. Most 6 cylinder cars, when I grew up, were larger and in fact most performance 6 cylinder new cars are very close at 3.5 liter and 3.7 liters.

Engine displacement or size (in liters or inches or whatever) is a big factor in low RPM power/torque. Another is efficiency or how well the systems work together to CHARGE the engine at low RPM with air. A BIG part of this is a high velocity exhaust system that prevents reversion. The stock system is VERY good at this. It is also much smaller than MOST people are used to seeing on performance engines.

A few years back I contributed a high flow racing 2-1 merge collector 2.25" into 2.50" to the first car to run the S&S headers. A 2.25 to 2.50 Y pipe was built using this. Peak power went up by ONE horsepower. Low speed feel was terrible. The part flowed too well BACKWARDS. It hurt velocity and allowed reversion.

Because of that and other evidence I have been recommending the STOCK Y pipe for some time. I have always said a better system COULD be built it was just unlikely that most muffler shop efforts would beat the stock Y and most likely be worse.

So, I am finally able to focus on this situation. I will build a performance Y pipe for my LS which has a nearly identical Y pipe to the GS. The LS is heavier so it is even more important to keep low end power. If I successfully make a better than stock Y then we will have a repeatable design to copy.

My experimental Y pipe will feature a high velocity one way merge like the stock part does. It will be smaller than 2.25" but larger than stock. The LS Y pipe is VERY similar to the GS4xx. I will post a picture showing just how close. The LS and GS engines are identical.

 

Look closely. This picture shows the LS400 Y pipe on TOP of a GS400 Y pipe. The GS430 Y pipe is also identical except it has a center catalyst instead of a center resonator. The GS has a larger inside diameter center resonator than the LS400.

 

I will keep my eye on this thread. Thanks for answering my pm Jbrady

 

Interested to get one for my GS430 because mine is leaking. Keep us posted.

 

Great work J...can't wait until you are done!

 

Jbrady, this is an interesting topic you have started, I have been mullng this over for some time now. Have you done any research on X and H pipes? I was wondering why lexus didn't use either, I was thinking to keep the exhaust system separate by banks, and use an h pipe at the same distance that lexus has the crossover. What do you think?

 

Yes, and I have more than a few posts about them. Y and X systems MERGE the two flows together to enhance velocity which creates power. H systems including "window" type X pipes (two pipes bent towards each other that just "kiss" with a small window connecting them) create a large pressure area change at a targeted point to simulate the open air signal at the end of a collector that has no exhaust. Like any tuning attempt the position, size(s) and design of the crossover have a BIG effect on whether it works or possibly hurts performance.

The stock system is actually a LONG X design as the front Y feeds the extended merge then it is split again into duals. The stock design is NO mistake and was carefully crafted by Lexus engineers for low speed performance AND durability.

 

man...never thought about the large x pipe...thats deep...call me when you're ready, I'll be there

 

For your car I would like to try two designs. First, I am going to build a NA system for my LS400. As shown in the above pics it will be easy to duplicate for a GS4xx. Then I want to build a SLIGHTLY larger Y pipe system for your supercharged car. I would like to test BOTH the NA design and the larger design on your car. My gut feeling is the NA design may offer a better over all feel with minimal sacrifice of peak power. Are you super concerned about making 430rwhp vs 420rwhp especially if the 420 system makes better mid range power?

Anyway, if you want to try both systems all I will need is to order enough of each size pipe, flanges and V band clamps. Usually I prototype in steel and then if proven build with stainless. There is NOTHING wrong with a steel system as it can be Jet Hot coated for excellent durability, performance and appearance. We can discuss the variables before you drive in to the third largest city in the USA

 

Can we discuss these variables between stainless and JETHOT.

Cost VS durability, performance and appearance.

Living in a rust belt state, I am wondering on the cost of the S&S headers in stainless steel.. even if they would build them. Then paring these with your Y pipe.

 

I'm all about driveable hp as opposed to max hp. Let me know when you are ready, I have a baby due Feb 5th so the sooner, the better. That way I can leave without having to worry about the wife going into labor.

 

Jake,

Jet Hot was developed as a rust preventor for marine apps (extreme salt and temperature environments) that could withstand extreme heat changes. I applied it to an old rusted custom exhaust I had built for my turbo car years ago and it made the part "new" again. Applied to new steel it results is a very durable finish that keeps the part protected from corrosion.

It looks very nice. Maybe not as nice as polished stainless but still nice.

Performance wise it reduces heat transfer and keeps underhood temperatures down even without heat shields. The ceramic is a better insulator than stainless so some stainless headers get ceramic coated to reduce temps.

Cost to build a stainless header is much higher than mild steel due to many reasons. Materials cost much more, stainless is harder to cut, must have very tight fitment prior to welding, welding is harder and must be backpurged to prevent internal scaling. S&S does not typically work with stainless so they are not likely to make it an option since they are not set up for it. It is more than material it is the process of construction.

Jet Hot coated steel should outlast your ownership

 

Very interesting J..

Well it looks like I will get my headers Jet Coated - black. S&S wants $50 more for the color change but its worth it IMHO.

Are you planning on building these and shipping them straight to the person after payment? Or are you going to just sell the plans then we take them to a local shop?
IF you are going to build these for us, are you willing to ship it to JET HOT for us so I can get it coated...

Thanks!!

 

A little premature as I have not built even a prototype and at this point I am not a vendor. If I decide to make a quantity for others I will look into either becoming a vendor or offering through an approved vendor.

That said, and IF... then sure, Jet Hot is a good option. I may even do stainless of course the cost would be greater.

So, step one, build prototype and test. Step two, if it warrants production figure out how to make them available.

BY THE WAY.

Was looking at some of my GTech data for my car in the GTech PASS software and found a VERY interesting view that I had not noticed the value of. The HORSEPOWER vs. TIME tab gives exactly that how much power is produced throughOUT a run in ALL gears. While no RPM is included it can be cross referenced with that tab.

The IMPORTANT part of the above is I can see improvements in ALL ranges which is BETTER than a chassis dyno!!! SWEET

 

any update on this Y pipe im in need of this really bad,