Exhaust Merging options and Scavenging

JBrady

Moderator
What about this merge design ......Would it be effective on the 1UZ?
http://planetsoarer.com/pdf/xfactorcolour.pdf

Simple enough to make in a shed. :D


On my Hilux conversions, I use the stock LS400 exhaust manifolds into 2.5" down pipes (about 12" long) then the rest of the system is all 2" pipe with a 'H' pipe where the 'Y' pipe would have been on the LS400, then a Flowtech Raptor muffler on each end with polished 3" tail pipes. No Cats. Nice sound to the exhaust at idle and light throttle and an 'I take no prisoners' bellow at WOT!:D
Bushwhacker, I have seen the planetsoarer posting before, it is a Y pipe design, it was guesswork and the results will not be the same for other engines and configurations as total dimensions are important. There is a lot of math involved along with R and D in developing effective systems. Sure, you can get lucky with a "new" design but I would say few improve upon the stock Y pipe on these cars.

I am unsure of why you use 12" sections of 2.5" pipe off the manifolds?
If it were mine I would make a smooth transition from the manifold outlet to 2.00" tube.
Why an H instead of a Y or X?
BTW, there are multiple types of X and Y pipes and they function differently.
 

JBrady

Moderator
I don't know if that X-pipe kinda setup you linked would have any sort of decent scavenging Bushwhacker, the idea is to get each exhaust pulse from one bank to "draft" the pulse of the other bank by ramming them into a merge, that design is more just like a chamber to mix the gas from each bank to balance the noise, would be a heap of turbulence in there (My guess)

What I was hoping to do was because my merge will quieten it down a lot, is run an electronic cutout at the End of my merge just before it splits again so I can have a loud button. Just not sure the flow through these "e-cutouts" is any good. Plenty of dyno results out there saying they pick up power across the board. But I'm thinking that might be because it's reducing power while it's closed rather than gaining power while open lol.

Just been thinking about it, and I might speak to the exhaust guy Samsdad knows sometime to see if he's willing to try and make a a W-pipe I guess you could call it. A Y pipe with a middle piece that is valve, so that the flow shouldn't be interrupted much (The 2 splits coming off at a greater angle) And also when it's open MOST of the gases will blow through the middle section rather than past the cut out (Making it sound like an exhaust leak rather than cut off exhaust).

Could work well for times when you want extra loud and some extra flow, like at the track.

Something like this so to speak (Excuse the picture, Microsoft paint and bad mouse pad)


open the valve and the flow will go straight out the middle of the Y pipe (Most of it)

I guess you could even make it a bigger valve
Steve, you seem to be grasping the physics fairly quickly.
The valves can be used to bypass restrictive mufflers therefore creating power by reducing backpressure or they can be used as you are intending bypassing unrestrictive mufflers to increase sound. If you want maximum power when in quiet mode with the option to increase sound only on some occasions I would create a reverse X after the second split. Using a good Y section to split the exhaust towards the duals create a mirror Y back to a central single bypass... OR... use two bypass valves right before each muffler.

If you want a quiet system for moderate operation and a loud system for all high RPM power... you could use the duals asymetrically... one outlet to a restrictive small even stock muffler and the other to an unmuffled pipe ending in the valve. When closed all gasses go to the muffled side and when open something like 75% will go to the unrestricted side.
 

BigSteve

Member
Yeah the plan was Moderate flowing system for regular town use, and the higher flowing loud system for performance. Sleeper mode to Loud/fast mode with a button.

Without taking up too much space and being too complicated, The most efficient way I've thought of doing this so far is just having the valve flanged onto the end of the 2.5" pipe and Have sort of chambered bends welded onto the side so the gas doesn't have to turn around and come back to escape.

Here's another Pro MS Paint example.


I like the idea of exhaust gases going nowhere but straight when the valve is open. Plus it'd be easier to fit under the car
 

Beezer

Member
My exhaust (2.25 dual with balance pipe)my original exhaust guy suggested putting a small balance pipe in my twin exhaust setup and due to lack of research, I let him go with the balance pipe instead of the X-pipe I asked for.

I regretted not doing enough research first, the slap/cackle is rather annoying and there was no noticeable increase in performance, felt more like a loss in response (Which I have no doubt that was the exact result).

So I'll be changing the setup to a merged system. Either a Y pipe into 1 straight through muffler and then split back into 2. Or a dual in/dual out Muffler with internal x-pipe.
This is *exactly* what happened to me too. I got a 2 box system with a balance pipe rather than the 3 box system I asked for. It was loud and performed badly. I took it back and this time he tried to save time/money by fitting a centre twin in/out silencer & keeping the balance pipe. Now it was quieter and performed badly. So, I took it back a 3rd time and insisted on him removing the balance pipe and fitting a centre silencer as you describe above. The difference in performance was astounding!
 

BigSteve

Member
Yep, unfortunately most exhaust shop owners don't understand the actual science behind exhaust scavenging and reversion. I guess it's like trying to find a Doctor that knows something about the human body.
 
A thought i had about the collectors being 2 1/4" instead of Johns recommended 2".
Would a fix be to put a filler peace suspended in the middle of the pipe to effectively reduce the flow area off the pipe.?
 

BigSteve

Member
Nz Jailbar. I'm going to take a guess and say no, a single section of reduced diameter won't help much unless you're asking something else?
 

JBrady

Moderator
Yeah the plan was Moderate flowing system for regular town use, and the higher flowing loud system for performance. Sleeper mode to Loud/fast mode with a button.

I like the idea of exhaust gases going nowhere but straight when the valve is open. Plus it'd be easier to fit under the car
Steve,

Attached are three quick drawings suggesting what I would TRY to achieve your goals.

Depending on what mufflers you choose after the split the backpressure they create could be very small or somewhat high. If the backpressure is small there is little if any power gains by using the valve but of course the sound level will go up substantially especially inside the car if the openning is under the car.

Even the stock mufflers will flow decently and should not create too much backpressure at up to 300hp.

I like having an efficient splitter or dividing Y pipe after the main single section. I don't like the idea of a flat end to the center pipe. I would design a Y section as pictured with the valve being one half of the split. I would limit the valve opening to half the angle of split. If the split is 45 degrees the valve should open only 22.5 degrees. When closed it becomes part of the split and guides the flow to that side pipe and muffler. When open it creates a straight exit for the exhaust. Do not worry about the total area as the combination of the flow outlet area should drop pressure to zero. Lets call this a Y valve.

Now, the length of the center pipe and the position of the Y valve WILL effect the tuned length of the secondary piping and will effect power. It is possible to increase power and also possible to reduce power. When open the Y valve will look to the exhaust system/engine as an open pipe creating a negative pulse. You may need to experiment with the length of pipe AFTER the Y to optimize the effect. I will say that when I removed my second Y from my stock system leaving apx 2.5 feet of pipe after the front Y collector the sound went WAY up but the power did not... if anything it went down and that is compared to the stock 4 mufflers. My design below has the benefit of being able to easily adjust the length of the 2.00" pipe after the Y.

First picture shows with vavle closed and the flow. 2nd valve open. 3rd open flow.
 

Attachments

JBrady

Moderator
This is what i was meaning .Please excuse to drawing ,first time on paint
jailbar, while your idea to reduce the collector volume is in the right direction I think the variables as well as the hassle to create a good flowing insert and weld it in place... with unknown results... leaves the probably better solution to cutting the stock collector off the headers and building a good collector out of smaller pipe.

The length of the collectors matter and smooth transitions are helpful. What is the power level of the engine you are working with? What are the primary pipe diameters of the headers you have? If you have the 2.25" collector I would just make a smooth transition from that to the 2.00" stock Y pipe or build one out of 2.125" (two and an eigth inch) pipe. If you have the 2.5" collector then it depends on the primary pipe size as well. A cone shaped adapter to reduce collector to pipe size is reasonable with a slow taper being better than a quick one.
 
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The manifolds are a tri y design with 1 5/8 primaries into 1 3/4 then into 2 1/4 collectors .
I have it going down to 2" them merge into 2 1/2 and have made that collector with a double d similar to the toyota one (that took some time).This is all on a ucf20 motor with custom long runner intake .Just playing with it. Will be a long time before it is going. Will be interesting to see how it goes when finished .
 

BigSteve

Member
Hey JBrady, I had already considered the type of design you have drawn up but dismissed it as I don't see it possible to build that kind of system with the valves that are actually available on the market. If you have a look at the type of electronic valves that are around they are built into a fairly thick flange and open to 90 degrees. I'm not sure the results would be worth building a whole new electronic valve system.

So unless you think you can build the part you designed for still a reasonable price, I still need to look into other methods to incorporate the ebay electronic valves.

The mufflers will still be the straight through magnaflows on the back for now. But I figured taking out all of the rear bends will result in still good gains.

Maybe just using one of the standard electronic cutouts is the simplest option?
 
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JBrady

Moderator
Hey JBrady, I had already considered the type of design you have drawn up but dismissed it as I don't see it possible to build that kind of system with the valves that are actually available on the market. If you have a look at the type of electronic valves that are around they are built into a fairly thick flange and open to 90 degrees. I'm not sure the results would be worth building a whole new electronic valve system.

So unless you think you can build the part you designed for still a reasonable price, I still need to look into other methods to incorporate the ebay electronic valves.

The mufflers will still be the straight through magnaflows on the back for now. But I figured taking out all of the rear bends will result in still good gains.

Maybe just using one of the standard electronic cutouts is the simplest option?
If you are running straight through Magnaflows I doubt there is any power gain available with the cutout valve unless you engineer the system to TUNE to the length to the cut out. The extra pipe that you eliminate from the flow path is not a problem and can actually be a benefit as it directs the MASS of the flow. This larger mass will continue to flow in ONE direction... away from the engine and thereby help prevent mass reversion.

Yes, the larger mass will take a moment to accelerate and will give slightly less crisp tip in throttle response but on these street cars something hardly noticeable where the low and mid range torque increase will be.

The only "benefit" I see to a cut out in the design is increased sound for those wanting that result.
 

BigSteve

Member
Hmm, well I guess I might stick to a simple cut-out system and have it there just for some extra noise. And see what sort of effect it has on a dyno when it eventually gets tuned.
 

JBrady

Moderator
The manifolds are a tri y design with 1 5/8 primaries into 1 3/4 then into 2 1/4 collectors .
I have it going down to 2" them merge into 2 1/2 and have made that collector with a double d similar to the toyota one (that took some time).This is all on a ucf20 motor with custom long runner intake .Just playing with it. Will be a long time before it is going. Will be interesting to see how it goes when finished .
Jailbar, well done, your design should work nicely.
I applaud your effort to duplicate the factory "double D" design for your Y pipe collector.
If you are so inclined you could fabricate inserts for your header collectors.
Take sections of 2" pipe the length of your current collectors, make one lengthwise cut, expand slightly to fit the inside of a 2.25" pipe (roughly 2.1")
Finish to fit tightly to the ID (inside) of the 2.25" pipe (roughly 2.1" OD) effectively reducing your collectors ID from 2.1" down to apx 2.0" before flowing into your Y pipe ID of 1.85" (2.0" less .065" tube wall thickness for 16 gauge)
A slight chamfer of the edges should reduce any edge obstruction to flow to a minimum. These inserts could be relatively easily inserted or removed for dyno and street testing.
Keep us posted.
Do you have any pics of that intake?
 

JBrady

Moderator
Just some pics off what I have been doing
Excellent.

Readers take note, this is the CORRECT way to build a high efficiency collector.

On the intake, very interesting. It appears as you have more or less duplicated the factory runner length to preserve low end torque and response while removing the restictive lower intake manifold. It should work well.

Great work!
 

spf_lexus

New Member
Very clean solutions! Most people use about half the runner length when ditching oem but as said above, best of both worlds... impressive indeed.
 
Thanks guys. That was what I was trying to achieve. I have lots of height to play with so that wasn't an issue with the runner length. The exhaust headers haven't got as good merges as that one but should still be way better than factory . These mods along with slight cleanup off the ports, aftermarket engine management ,a bit off trans shift improvement and one off kdogs tiptronic trans controllers should make it quite nice to drive.
 
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