Starting with the 1st fired pulse as it leaves the cylinder,
#1 pulls #2 & #2 push's #1 Eg: the vacuum trail from #1 sucks on the forward pressure wave from #2 which is also pushing the vacuum trail from #1
mrfxit,
Dec 4, 6:05pm
Variations.
Set all 1st stage pipes the same exact length Start with the firing order, follow each pulse, set the pipe lengths so that each pulse is in the same exact order as the firing order as it enters the collector. (which is the exact reason for equal length pipes)
The hard bit . > If you have or need a dual collector system (4 in to 2 in to 1), set the collectors so that they follow the same pulse pattern 1243, 1243, 1243
sr2,
Dec 4, 6:11pm
It's an inline 6?
mrfxit,
Dec 4, 6:13pm
The old basic engines from the 60's & 70's respond very well to breathing mods. Each time I went from the factory cast manifold to freeflows to tuned extractors created the need to totally retune the engine at each stage
mrfxit,
Dec 4, 6:15pm
Irrelevant, the science is the same regardless of how many cylinders are involved
tintop,
Dec 4, 6:24pm
1342 ?
sr2,
Dec 4, 7:28pm
For Gawd's sake it's an inline, 9 port Holden Red!
twink19,
Dec 4, 7:31pm
my son built a set for his BDA stainless, took him about a week, work and look good
mals69,
Dec 4, 7:52pm
Yeah , was reffering to "supercharging" term mentioned in article in second link. Not actual supercharging.
mals69,
Dec 4, 7:55pm
Are you reffering to TVR griff 500 ?
timmo1,
Dec 4, 9:10pm
If the pipe diameter is the same, then if the volumes are the same, the lengths are too.
tintop,
Dec 4, 9:14pm
:) It was a leg pull, being used to BMC engines - I got caught out by a Ford once :)
The one I am working on presently is a Datsun A15 into a MG Midget. Not a hellishing amount of room between the chassis rail and the suspension cross member brace.
snoopy221,
Dec 4, 9:49pm
Dare one rock in here and simply state. Not only do extractors allow more surface area for cooling and shrinking exhaust gas volume-The *Upside* IS as alluded to
The ability to use the reverse shock wave traveling at the speed of sound to *Intrinsically momentarily*-Given speed and TIMING* Allow the shock wave to be physically present as an *evacuate* In the exhaust valve area-THEREFORE REMOVING 14.7 PSI(Gauge) of Atmospheric pressure.
NOTE-This effect is inherently MOST pronounced in *power-band* on single cylinder engines. (Motorbikes)
For Gawd's sake it's an inline, 9 port Holden Red!
bjmh wrote:
True, but having a bit of 'suck' at the end of the exhaust stroke will help scavenge the last of the exhaust gases and start the inlet flow a wee bit earlier during valve overlap time.
Quote
tintop . a lot of the headers in the early days ,had staggered pipe lengths in the collectors to achieve this. then eventually I guess it was a heck of a lot easier to just join them all flush inside the collector,i built some for a zephyr looked like a spaghetti factory. but had a sound of its own,who knows if it went different.
Well put too cheers - makes sense - helping to pull air in and exhuast gases out, like in the article - supercharging in effect :)
Hence as to the sonics of the shock wave and the ole 4in to 2 and 4 in to 1 and 4x2(builders-lol) arguments have yae NEVER noticed most jappers actually have a timed RESONATOR built in to the exhaust system at a specific distance. I.E. AS AGAIN STATED One single cyl-pipe expansion area shock wave Hence WHY 4 in to 2 +4in to 2 . Does NOT have the same shock wave as 4 IN TO 1 Most propriety exhaust systems USE many pipes in to a single collector
For Gawd's sake it's an inline, 9 port Holden Red!
186S Was an improvement in flow-two manifolds and a Y pipe- Effectively a collector-Which inherently had a sonic
For Gawd's sake it's an inline, 9 port Holden Red!
Yeah Bo 60's and waa hay factory option- lol-sonic powerbanded shockwave SUPERCHARGED. - .
mrfxit,
Dec 5, 7:28am
LOL Snoopy, I totally understand that posting.
Another factor that most ppl forget about is gas expansion & contraction along with (to a lesser degree) pipe as well.
Large front pipe leading down to a resonator then reducing slightly to a smaller pipe as the exhaust gas cools. This keeps the gas velocity reasonably constant
mrfxit,
Dec 5, 7:32am
Basic Thermal Dynamics.
If you don't understand that concept, then you will never make the best extractors possible for the application.
mals69,
Dec 5, 7:39am
Whats with the quoting - read the article in the second link and it will make sense - their words not mine.
sr2,
Dec 5, 7:47am
You still haven't told us which of the options in #22 you would recomend and why? (Inline holden 186, f/o 153624)
bjmh,
Dec 5, 8:50am
however you do your "extractors " the one thing that amuses me is how some build large diameter primary tubes,surely a bit bigger than the exhaust valve is sufficient . all this huge diameter pipe must play havoc with low torque,unless its got forced induction . awww option D for me ,but collected with staggered secondary tubes into 1.
lack of room can be a bitch in a lot of these jobs (excuse the brand & model)
mrfxit,
Dec 5, 9:05am
What I used to do 'way back' in the bad/good old days was reduce the rest of the system in size. Eg: 2" to the 1st muffler & 1" 3/4 tail pipe after that Gas's shrink in volume as they cool & to keep a constant gas flow speed, hence my thinking on that concept
bjmh,
Dec 5, 9:33am
I agree . nowadays its almost like penis extension. bigger,bigger drain pipes out the back
budgel,
Aug 1, 8:20pm
That's interesting, when I put up the original post I was researching building an after-turbo exhaust system for my 1.8T Audi. Do you think the volume shrink has as much effect on a Turbo car? Back pressure was thought to be quite important, now everyone seems to want to be rid of it.
I remember the term 'headers' wasnt used much when I was a youngster, we had freeflows; and extractors which were the better designed ones. I suppose headers becoming the common term just goes with the Americanisation of everything, not that it matters to any great degree.
Since the public registrations are closed, you must have an invite from a current member to be able to register and post in this thread.
Have an account? Login here.