2017: Revisiting 4:2:1 vs 4:1 headers w merge collectors in the modern era

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Re: 2017: Revisiting 4:2:1 vs 4:1 headers w merge collectors in the modern era

Post by exhausted » Sat Nov 04, 2017 6:14 am

NewbVetteGuy wrote:
Tue Oct 31, 2017 2:11 pm

The traditional rules-of-thumb / advice that 4:1 headers have huge advantages over 4:2:1 at high RPM but give up a lot in mid to low RPM torque and do nothing to prevent reversion as overlap increases & that 4:2:1/Tri-Y headers are for low to mid RPM torque improvement, reduce reversion and are largely appropriate for low RPM truck and street motors and fall on their face at high RPMs seem to be increasingly untrue as you look at the newer improvements to both designs. (Old street designs like the Doug Thorley 4:2:1 Tri-Ys come to mind immediately, advertising that they're better than 4:1s "up to 4,500 RPM"; note: I'm in no way bashing these, simply highlighting an example of a Tri-Y design clearly in the "improve low end torque at the expense of high end HP" camp. )
I used to race a Competition Jet boat all over the Southwest, 460"BB, Doug Thorley upswept headers and a 4-2-1 collector. They ran great but never saw a dyno or did any comparisons so who knew? The boat won two national championships. At that time like you said everyone knew they lost some power upstairs. (Well, what is upstairs anyway?) In my view what everyone knew was really that anytime you made a given header longer you would lose power upstairs. (If it was long enough to begin with.) Put those collectors on a Shorter primary header and voila. This is exactly what I did back in 1995 for the Cup restrictor engines and Voila.
Length protects your bottom end power and gives up upstairs.
Calvin Elston
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Re: 2017: Revisiting 4:2:1 vs 4:1 headers w merge collectors in the modern era

Post by RCJ » Sun Nov 05, 2017 6:12 pm

With 4:1 headers and merge collectors, have you ever experimented with moving the choke point farther from the end of the primaries?

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Re: 2017: Revisiting 4:2:1 vs 4:1 headers w merge collectors in the modern era

Post by NewbVetteGuy » Sun Nov 05, 2017 7:43 pm

exhausted wrote:
Sat Nov 04, 2017 6:02 am
NewbVetteGuy wrote:
Fri Nov 03, 2017 7:31 pm
Great advice here. I'm taking all of it.


1. I'm going with Tri-ys (Calvin's advice is pretty unambiguous.)
2. I've saved a post previously where Larry Meaux talked about how to apply PipeMax recommendations to TRI-Y designs so I'll dig that up again
3. I'll either buy the off-the-shelf option or see what the folks at Stans would charge to make a custom tri-y based upon the PipeMax recommendations (I live in Seattle so Stans is pretty close to me.)


Adam
You could ask me.
If I decide to go with a custom Tri-Y, I'll definitely give you a call first; I am almost certain I can't afford your level of expertise, though, Calvin. (My current off-the-shelf FlowTech coated headers cost $275; the only quote I got for a custom set so far, from a race-focused customer header builder was over 14x that much. My budget probably stretches to about 4x the flowtechs, but nowhere near 14x.)


Adam

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Re: 2017: Revisiting 4:2:1 vs 4:1 headers w merge collectors in the modern era

Post by 69top502 » Sun Nov 05, 2017 8:10 pm

Calvin did a set of 421’s for my 69 Vette. Worth every penny. Too pretty to put on the car lol. What was really priceless is the time talking to Calvin and learning, among other things, the internet is not the place to learn what makes a good header for a particular application.
69 Corvette, 502 w/ solid roller cam, 653 hp Street/Strip.

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Re: 2017: Revisiting 4:2:1 vs 4:1 headers w merge collectors in the modern era

Post by rebelrouser » Tue Nov 07, 2017 11:40 am

I built a set like these for my nostalgia super stock car, 512 mopar RB engine. And some of the guys I raced with made fun of them so I finally replaced the collector with a standard 4 into one merge style, the car slowed down one tenth. Put the Hedman 4to2to1 collectors back on and the tenth came back.


http://www.grumpysperformance.com/1110e ... s+.JPG.jpg

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Re: 2017: Revisiting 4:2:1 vs 4:1 headers w merge collectors in the modern era

Post by exhausted » Tue Nov 07, 2017 5:26 pm

RCJ wrote:
Sun Nov 05, 2017 6:12 pm
With 4:1 headers and merge collectors, have you ever experimented with moving the choke point farther from the end of the primaries?
Yes. If you mean by adjusting how to make the collector? No. Primary length VS Choke diameter? yes very important.
Calvin Elston
Elston Exhaust Inc.
Matthews, NC 28104
704-443-8088
Web: www.elstonheaders.com
Blog: www.exhausting101.com

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Re: 2017: Revisiting 4:2:1 vs 4:1 headers w merge collectors in the modern era

Post by Erland Cox » Wed Nov 08, 2017 12:00 pm

Calvin, is it the angle that the exhaust oprns up that is important?

I am doing tests on a 4 cylinder engine with different 4-2-1 headers.
They look like this:

Image

And come in these sizes:
Typ1 44-44-60mm
Typ2 44-48-64mm
Typ3 44-51-64mm
Typ4 44-54-64mm
The primary length is around 330mm and the secondary around 700mm.

I Have tested with different lengths on the 64mm exit and that did absolutely nothing, no difference what so ever.
The exhaust system that also is 64mm with 2 mufflers and below 95db at the track at full gas only loses 5 hp.
The tests I am doing now are with the exhaust system.

I have also tested the secondary length and that moves the power curve up with shorter pipes.
This car has Weber 50 DCO carburetors so it is an IR setup.
It is very sensitive for double carburetion and if I shorten the secondary pipe I get a very fat spot at 3500 to 4000 rpm.
With shortened secondary so fat that it wets the plugs and lowers power further up in the rpm range.

Image

This dyno test is with everything the same except starting rpm.
It is with a type 4 extractor with the secondaries shortened 150mm:s.
The lean spot in the lambda after the fat dip is because of plug wetting.
The type 2 extraktor almost totally does away with this dip and no misfire but a little less top hp.
The type 3 seems to work best and does not go fat enough to misfire as long as the engine is not held at WOT at low rpm.
I have a rolling road where the type 3 works but held in a dyno and accelerated with 600 rpm power is down and lambda reads lean.
I am busy with modifying a 4-1 header to a 4-2-1 type.
It has 45mm primaries 28" long and i am putting on adjustable 51 mm secondaries.
I will probably make the primaries as short as possible and adjustable to.
Then it is back to testing.

Any advise on hiw to stop double carburetion?
Reverse cone on a 4-1 or 4-2-1 is better?

Erland

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Re: 2017: Revisiting 4:2:1 vs 4:1 headers w merge collectors in the modern era

Post by exhausted » Wed Nov 08, 2017 1:32 pm

Erland,
Anti-Reversion valves. Smaller primaries for the first 10" and ports also.

So, 44mm. If I assume that is maybe the primary ID? 1.73",...240 HP/... way to big for that power level.
The pressure waves are able to go anywhere they want and the gases themselves are not able to get very far from the engine.
The 421 design is able to diminish reversion but for the amount of time you have between pulses with a 4 banger and such a big volume and low velocity you are at the mercy of those pulses going backwards no matter what you have.
I think I tried to lay this out on my blog "exhausting 101" but you have to impliment AR in as many places as possilbe and find which sizing and placement are most effective, and work on the blowdown length sizing along with port and valve sizing.

I have to say often that it is not my fault that the manufacturer or head porter made the exhaust ports too big.

There is also another rule; If you can change a header or a system design and not see a difference? your leaving power on the table.
Calvin
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Re: 2017: Revisiting 4:2:1 vs 4:1 headers w merge collectors in the modern era

Post by Erland Cox » Wed Nov 08, 2017 2:20 pm

I usually make the port exit the size if the valve snd this engine has a 38mm valve.
The port has a rectangular exit with radiused corners with the area of a 38nmm round hole.

This is what Pipemax says for a single diameter 4-1 header:

--- Single Primary Pipe Specs --- ( Low to Mid-Range RPM Torque and HP )
Diameter= 1,655 to 1,780 Total Length= 26,9 to 29,3 inches long

That is Diameter= 42,040 to 45,215.
Is this really to big? Popemax had smaller doameters in earlier versions but this is the diameter for Low to Mid-Range RPM Torque and HP.

Here are all sizes:

--- Single Primary Pipe Specs --- ( Low to Mid-Range RPM Torque and HP )
Diameter= 42,040 to 45,215 Total Length= 682,7 to 744,9 MM long
--- 2-Step Primary Pipe Specs --- ( Low to Mid-Range RPM Torque and HP )
1st Step Dia. MM= 42,040 Length= 341,4 to 372,5
2nd Step Dia. MM= 45,215 Length= 341,4 to 372,5
--- 3-Step Primary Pipe Specs --- ( Low to Mid-Range Torque and Hi RPM HP )
1st Step Dia. MM= 42,040 Length= 341,4 to 372,5
2nd Step Dia. MM= 45,215 Length= 170,7 to 186,2
3rd Step Dia. MM= 48,390 Length= 170,7 to 186,2

--- Single Primary Pipe Specs --- ( Mid-Range TQ to Higher RPM Horsepower )
Diameter= 47,120 to 50,295 Total Length= 682,7 to 744,9 MM long
--- 2-Step Primary Pipe Specs --- ( Mid-Range TQ to Higher RPM Horsepower )
1st Step Dia. MM= 47,120 Length= 227,6 to 258,7
2nd Step Dia. MM= 50,295 Length= 455,2 to 486,2
--- 3-Step Primary Pipe Specs --- ( Higher RPM Horsepower, possible TQ loss )
1st Step Dia. MM= 47,120 Length= 227,6 to 258,7
2nd Step Dia. MM= 50,295 Length= 227,6 to 243,1
3rd Step Dia. MM= 53,470 Length= 227,6 to 243,1

Erland

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Re: 2017: Revisiting 4:2:1 vs 4:1 headers w merge collectors in the modern era

Post by exhausted » Wed Nov 08, 2017 3:34 pm

Erland, you asked about how to control reversion. I told you.
If you make everything big you can make plenty of power but if you don't have enough gears you'll be in trouble at the race track.
Does pipe-max allow input for rpm band input? I don't know.
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Blog: www.exhausting101.com

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Re: 2017: Revisiting 4:2:1 vs 4:1 headers w merge collectors in the modern era

Post by Erland Cox » Wed Nov 08, 2017 5:10 pm

No rpm band input there.
The long stage 3 4-2-1 pipe works well for road racing but I always want more power and keep my bottom end power to.
Have your cake and be able to eat it.
I learn a lot trying at least.
Thank you for trying to help me out.

Erland

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Re: 2017: Revisiting 4:2:1 vs 4:1 headers w merge collectors in the modern era

Post by hoffman900 » Wed Nov 08, 2017 6:01 pm

Those numbers seem reversed.

I'd expect the primary to be in the 22-24" (560mm-610mm) range and the secondary in the 12-14" (305mm - 355mm) range for that poweband. Diameters are much too large. The area of a 38mm round hole could use a 1.625od pipe (41.275mm) no problem. Maybe a 1 1/2 od pipe (38mm) if the wall is thin and it is shaped correctly.

Everything Calvin preaches applies (seemless transition, large bend radii, etc.). It seems to me most cheaper 4-2-1 headers reallllyyy pinch cyl's #1 & #4 on the bend radii front. A 6-3-1 header is basically hopeless in this regard.

Calvin told me one time, and it was talking about the Burns Stainless specs, that their diameters are pretty good, but that's the ending diameter, not the starting. It may take a few steps to get there. ;)
-Bob

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Re: 2017: Revisiting 4:2:1 vs 4:1 headers w merge collectors in the modern era

Post by Erland Cox » Wed Nov 08, 2017 6:25 pm

That is why I am converting a 4-1 to a 4-2-1 with longer primaries and shorter secondaries.
I am starting out with an existing header to make it simpler but I will try a smaller diameter in the future.

Erland

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Re: 2017: Revisiting 4:2:1 vs 4:1 headers w merge collectors in the modern era

Post by hoffman900 » Wed Nov 08, 2017 6:37 pm

Erland Cox wrote:
Wed Nov 08, 2017 6:25 pm
That is why I am converting a 4-1 to a 4-2-1 with longer primaries and shorter secondaries.
I am starting out with an existing header to make it simpler but I will try a smaller diameter in the future.

Erland
My first guess is 22" and 12", but make it adjustable.
-Bob

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Re: 2017: Revisiting 4:2:1 vs 4:1 headers w merge collectors in the modern era

Post by 77cruiser » Wed Nov 08, 2017 6:43 pm

When i built my headers, after a long discussion with Calvin, I ended with the pri. & sec. about the same length.
Jim

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