Tri Y headers VS 4 into 1's

[la360]

I was hoping to learn some more about sizing of Tri Y's compared to 4 into 1's, Possible power gains or losses, power trends etc . I am looking at doing a set of custom headers for my 365ci Chrysler Small block, and I am curious about the benifts of Tri Y's. I have one of Larry Meaux's header programs, which is based around a 4 into 1 design, with a conventional collector, Tri Y's as we know, feature two different diameter pipes, and are of different lengths. I was looking at making some adjustable length units for dyno testing, but if someone on here could steer me in the right direction, and hopefully we ALL can learn something along the way.
Discuss.
AL....

[Torquemonster]

what is the application of the engine?

what rpm range do you need power?

BTW - has anyone out there ever tried anti-reversion coned headers, where you build a port extension through the flange about 1.5" then flare the primary pipe over it to provide a 360 degree clearance - this sends most reversion back against the flange around the flared primary instead of back up the port.

David Vizard picked up significant bottom end and mid-range doing this - extending the power band on 4 into 1 headers. The engine would take wide open throttle a full 1000rpm lower while increasing vacuum at partial throttle significantly. I've always felt that the ultimate max effort headers for a street engine would be anti-reversion coned stepped 4 into 1's with Burns merge collectors.

Of conventional headers - on a Viper - the Tri-Y Ballangers with the collector center velocity cone seem to work best up to around 800rwhp with a blower. Beyond that - 5 into 1.

[maxracesoftware]

the Tri-Y design "Primaries" are very sensistive to "tuned length"

and the 4-1 design is opposite, ..very sensitive to Collector more than Primary Length

use the 1st tuned Primary Pipe length PipeMax predicts for Tri-Y intersection/joined length and the 2nd predicted tuned length for overall Primary Pipe Length

i've done over a 1000+ Dyno tests on Headers, and so far, PipeMax predicts the "overall" length of the total exhaust system from inside the Collector where Primaries end -to- the end of tailpipe or collector dumping into atmosphere, at almost 100 % accuracy

on the Primary Pipe side, it also does a good job predicting dia/length, but it will predict a Primary & Collector diameter that might make the "BEST" HP/Torque on an Engine Dyno ,..but in the Race Car going down the DragStrip , the engine likes a smaller diameter Primary & Collector sometimes.

when it comes to trying out Headers on an Engine Dyno , its one area where you can get fooled a little...sometimes a smaller Primary/Collector diameter runs faster down the DragStrip

you can easily see effects of playing with Headers by using the Air Turbine
and measuring CFM/Ve %....the lengths / diameters will also change Ve% / CFM numbers as well as HP, Torque, BSFC, BSAC
..you also look at "Rates" of changes in Ve%, playing with Headers

[la360]

To give you all some background on my combination.
It's a 360 Chrysler small block,
4.02" Bore,
3.6" Stroke,
Flat top gas ported pistons with 0.043", 1/16", 3/16" rings,
6.625" BME Rods ,
W2 heads, 2.08"/1.60" valves, 296@0.500" 313cfm@0.600" @28' intake port
Roller Camshaft was around 264/272 @ 0.050" on a 106, installed at 101, Valve lift 0.623"/0.627" with 1.5:1 Harland Sharps
Indy 360-3 or Edelbrock Victor W2 Intake
The engine was raced with a 1 7/8" Primary x 32" with a long 3" Collector, and a box stock 850DP in the early 80's before being imported to Australia. I no longer have the original camshaft that was run with the engine either, Although I plan on running something similar, just maybe a little shorter @0.050" and on a wider lobe separation.
With the header sizing, What if I was to either run the 1st primary sizing suggested in the 2 setp design of Larry's program, which I believe was 1 7/8" , and run a 2 1/8" or 2 1/4" secondary pipe , or run the first two in the 3 step units. I would also like to run a merge style collector regardless of what I run, although I have a set of Flowmaster 4-2-1 Collectors sitting here, but the collector sizing is 3.5".
The engine was run in a 3000odd pound Dart, and went in the 9.8 range at around 138mph. My race car will be a little heavier, at around 3200lbs.
As I said in my forst post, I am very curious about the how's and why's of Tri Y header design, and Merge collectors also.
Thanks for the replies so far.
AL....

[ozrace]

Larry

You said:
"use the 1st tuned Primary Pipe length PipeMax predicts for Tri-Y intersection/joined length and the 2nd predicted tuned length for overall Primary Pipe Length ".
Do you mean the lengths predicted by PipeMax for a 2 step header ?
Also, do you have any observations you could share with us of how changing to a Tri-Y setup might affect the power curve - from your Dyno experience.

Thanks

[maxracesoftware]

Larry
"use the 1st tuned Primary Pipe length PipeMax predicts for Tri-Y intersection/joined length and the 2nd predicted tuned length for overall Primary Pipe Length ".
Do you mean the lengths predicted by PipeMax for a 2 step header ?

No, not the 2-Step Header , but instead the 2nd tuned length for the 1st Tri-Y segment at the 1st pairing ,....then use the 3rd tuned length for the "Total" Primary Pipe length

sorry for confusion , i mis-stated use the 1st tuned length, instead use the 2nd ...then the 3rd tuned length for the Total Primary Length

actually in this case use the 2nd tuned Length =17.1" inches to intersection of Tri-Y Branch then another 17.2" inches to end inside of Collector
and total of approx = 34.3" long for Primaries

the idea with the Tri-Y is to also catch the negative pressure wave at the "Branching/Joining" of the 2 Cylinders to increase scavenging and velocity, thats why the Primary Lengths are so critical in Tri-Y -vs- 4-1
the Tri-Y has a negative pressure wave at the Branch and again at the collector and again at the Collector exit, the design keeps velocity up through out the system and pipe surface area is relatively small to radiate less heat and keep velocity higher

the 4-1 can have smaller negative wave reflections with 2 or 3 Step header designs, but cool gases more, and basically have 2 major negative waves coming from Primaries dumping into Collectors and again with Collectors dumping into atmosphere..the Tri-Y has 3
==========================================

Engine Bore size = 4.020
Crankshaft Stroke = 3.600
Connecting Rod Length = 6.625
Number of Cylinders = 8
Engine RPM at Peak HP = 7000
Compression Ratio = 11.50:1
Number of Intake Valves= 1
Intake Valve Diameter = 2.080
Intake Valve Stem-dia. = .343
Max. Intake Valve Lift = 0.623
Intake Duration @.050 = 264
Degreed Int. Centerline= 101.00
Camshaft Lobe Centers = 106.00
Number of Exhaust Valve= 1
Exhaust Valve Diameter = 1.600
Exhaust Valve Stem-dia.= .343
Max. Exhaust Valve Lift= 0.627
Exhaust Duration @.050 = 272
--------------------------------------
--- Straight-Pipe Specs ---
Pri.= 1.884 dia. x 31.8 to 34.3 length
Tuned-Lengths= 8.6 17.1 34.3 68.5
--- 2-Step Header Specs ---
1st = 1.884 dia. x 15.2 to 16.4 length
2nd = 2.009 dia. x 16.6 to 17.8 length
--- 3-Step Header Specs ---
1st = 1.759 dia. x 15.6 to 16.4 length
2nd = 1.884 dia. x 8.4 to 9.3 length
3rd = 2.009 dia. x 7.7 to 8.6 length

--- Header Collector Specs ---
Collector= 3.517 dia 16.4 to 21.4 length
Tuned-Lengths= 4.7 9.4 18.9 38 75
------------------------------------------------


"If" your Peak HP occured at 7000 RPM then
the Dyno would show a 1 7/8 header x 34" & 3.500 Collector x 17 "
to make best combo of Peak TQ and Peak HP

but at the DragStrip its possible to run faster with
3 Step 1.750, 1.875, 2.000 headers and maybe 3.000 Collector

the 2-Step or 3-Step would be used with 4-1 Headers

1 7/8 Headers would be the largest Headers you need.

Collector = 3.500 x 9.4", or 18.9", or 38", or 75"

i would use the 18.9" for heavy car

the next spots are 38" and 75" for total Length from where Primaries end -to- where Pipe dumps into atmosphere

Collector Tunning=>
"worst " Primary Pipe ends inside Collector -to- pipe end in atmosphere
Lengths are = 28.5" inches and 56.5" in will hurt Torque/HP


all those above numbers are "without" Dyno mufflers or added Dyno pipe lengths, but instead using only your actual Race Car headers on the Dyno

[la360]

Another thing I have read about is the Tri Y design is that it splits the cylinders that fire consecutively. What you have said so far as been quite helpful, thanks Larry. I will have to play around with your program some more.
AL...

[maxracesoftware]

Another thing I have read about is the Tri Y design is that it splits the cylinders that fire consecutively. AL...

yeah, i didn't mention the obvious

but if you look at most Tri-Y designs the 1st pairing/branch segment Length is approx "1/2" of the total best Primary Length that will tune-in for the desired RPM range.

at the 1st Branch/Pairing, a negative wave goes up the other Cylinder's pipe...so the 1st segement is =17.0" inches long, the other Cylinder's pipe is 17.0" inches long..so its a total of 34.0" inches long ...so you now have a negative wave returning at the Chamber from going from the branching to the other cylinder's closed exhaust valve going back up to the open exhaust valve overlap period, for a total of 34 inches from just in that branch segment ...then you have a negative wave from the original full 34.0" inches of the total primary length

so with Tri-Y you have a very strong primary pipe negative wave

so what you windup with is 2 effective negative waves or reinforced single negative wave in just the 34 inch segment
then another at the Collector
then another at the Exit dumping into atmosphere

with all that going on , thats why Tri-Y primaries are critical and work over a shorter RPM range than 4-1

whatever Primary Pipe results in best HP/TQ combination, then its 1/2 length segment tunes in as well, then the 2 halves make up 1 full Primary Pipe Length

Exhaust wave speed is directly proportional to Temperature
the Tri-Y has less primary pipe surface area and tube distances

[Adger Smith]

Take a look at this design. Anti reversion design & a Very interesting collector too.
www.faic.cc

I don't want my V-6 to sound like a Harley, it already sounds strange!

[maxracesoftware]

I don't want my V-6 to sound like a Harley, it already sounds strange!

i was making Dyno Pulls to 9000-9200 RPMs one day on a Chevy Canted-valve V6...and one of the guys commented ;

"it sounds like a Weed Eater on steriods"

[speedtalk]

Take a look at this design. Anti reversion design & a Very interesting collector too.

I've seen that done before, except with a funnel to catch more air. I like the theory, don't know if it works though.

[maxracesoftware]

Take a look at this design. Anti reversion design & a Very interesting collector too.

I've seen that done before, except with a funnel to catch more air. I like the theory, don't know if it works though.

yeah. i'm surprised that person received a Patent for that concept, as i've seen drawings about 30 years ago with the "Funnel-shape" on the front side of a 4 into 1 header on the collector front halve

exhaust wave and velocity is temperature dependent
so i would have thought that with that above picture header design, too much air moving thru system would cool off pipe temperatures to a point that wave and gas velocity would be reduced, hurting scavenging

but now a Harley has an overscavenging problem and there have been attemps in chamber/port design to prevent too much overscavenging out the exhaust ports....so its possible that this might only work on systems with those problems ??

it might be worth maybe some dyno time on other applications to check this out ?

in the same train of thought...that might be some of reason why sometimes the exact header pipe dia/length combos don't always run down the DragStrip the quickest ....could be in certain high-MPH cars/dragsters, that cooling air changes wave/exhaust tuning...also underneath air movement can help or hurt scavenging compared to what the Dyno says the engine should want ???

[Adger Smith]

Larry,
Vic Custer said my v6 sounded like a Mad goat running down the track.

They say the Harley header is good for mid range & driveability. They have some dyno #'s on the headers. These guys are selling a bunch of these. I rode a bike with them & the sound was alot different than a regular Harley sound. Very nice! At about 3,000 RPM the draw through the collector will pull a rag all the way into & blow it out the back of the pipe. I would think it does kill some of the draw on the other pipes.

I wonder if it would help to put a 4 tube collector on my 3 tube V-6??

[bass16v]

the cooler the air inside the exhaust means more or less velocity?s

[maxracesoftware]

the cooler the air inside the exhaust means more or less velocity?s

usually the higher the Exhaust gas temperature
the higher the Exhaust gas and sound wave velocity

up to a point, the greater the pressure differential,
the greater velocity for a fixed cross-sectional area


a few Formulas you can look at

FPS = ( CFM / CA ) * 2.4
where
FPS = velocity in feet per second time
CFM = Cubic Feet of Air per minute flow rate
CA = cross-sectional area in square inches
2.4 = Units constant


Speed_of_Sound_FPS = (( 459.67 + TempF) * 2402.625624 ) ^ .5

1116.319772 fps @ 59 F

.55 Mach = 613.9758744 fps

Speed_of_Sound = (( 459.67 + TempF) * 1.4 * 32.174 * 53.34 ) ^ .5

Speed_of_Sound = (( 459.67 + TempF) * 1.4 * 1716.567377 ) ^ .5

Speed_of_Sound = (( 459.67 + TempF ) ^ .5 ) * 49.02

TempF = temperature in degrees Fahrenheit
459.67 = Rankine degrees
^ .5 = Square Root of a Number