Welp, I made my street header into a long tube header for the 12a bridgeport which collects near the rear axle simialer to the Racing beat long tube system which is for '79-85 12a....except cheaper to make. I made sure that the two pipes were equal lengh were they collect also. I have a dual flange right before the collect, so in theory I could run open uncollected there or run duals over the axle and into a custom muffler or just crom tips later on for races were noise isn't a concern. Then I have the standard flange where it hooks to the muffler pipe before the axle so I can take that off for repair transfer to another car. I have staggered glaspaks in the piping by the way.. which I had in the previous single pipe setup. They get hallowed after a while, but don't really quiet it down anyway, just deepen the tone.

Power result: Less power below 4000rpm. Bogs worse then before. However 4000rpm+ ....and above 7500rpm+....it improved considerablely. It pulls past 8500rpm easy. I shifted @50mph in 1st, and 75mph in 2nd!...realized that when I looked down at the speedo.

Anyway, I haven't yet got the jetting optimized and I haven't decided if I'll need a higher flow muffler to extract the most power, but once its optimized, watch out!

 

Well done.

What carb are you running BTW?

 

So your at about a 100 inches on the primary tube leangth? What you report is exactly what should be expected, longer tube leangth means more power at higher rpm's. Basicaly it just moves you pwr band up some while sometimes optimizing it. This realy only hold true to mild bridge ports and street ports though.

CJG

 

No, longer means LOWER rpm.

However by having the ultra-long tubes, you can take advantage of different resonance pulses. If you can imagine the separate exhaust pulses in the pipe, a longer pipe will allow it to be "tuned right" at more points than a short pipe.

 

quote from Racing Beat->Ofcourse I'm aware of exhuast tuning length, diameter, and effects on pulses combining at the right and wrong time. Scavenging... Every exhuast will hurt flow at some rpm and help it at another...its all trade offs, yes, knew that long ago. Course I knew it would hurt lowend power some.

Generally everything that helps highend power hurts drivablity at low rpm somewhat. Such as bigger carb bores and diameter piping...

Weber 50 DCO.

 

although the long tube headers will make more power at higher RPM it will also make more power over the curve vs a short tube header.

 

What are you talking about? Longer means more top end. This is a pretty proven fact.

CJG

 

At higher RPM the pressure pulses are closer together, so they'd prefer a SHORTER pipe.

 

That doesn't ring true though... Like why the stock manifold provides better lowend performance then with a streetable header? Stock manifold length were the pulses combine is very short and doesn't make the best high rpm performance you well know? And then when i get this long tube header setup yesterday, I get even more highend and less lowend below 4000rpm. Your logic is not exactly corralating with actual results.

 

no idea on this but, my buddies 2cycle alky go kart the Longer the pipe the more the Low end

 

2cycle? You know of expansion chambers don't you? There setup is completely different then a rotary & 4stroke cycle engine. Ofcourse if you are not combining pulses, things work differently.

Also by saying you have "no idea" doesn't help crediblity of that statement much. The fuel type doesn't effect how you would tune the exhaust on a engine unless your going from gasoline to nitromethane.

 

right but if you had a 2 BP motors one with straight dump 24" from the port and one with the pipes exiting 72"+ form the port

which will dyno higher?

you think exhuast wants to flow all that extra distance, not to mention the loss of velocity from the heat loss of the exhasut to the piping

loss of velocity is backpressure, last i heard bad thing for BP

rant off

 

Be more specific, "loss of velocity" ?? Pipes that are too large cause a loss of velocity at lower rpm. As for heat being absorbed by the piping...well, I'm not wrapping my pipes, you can.

IT depends...
I'm not sure with out dynoing it, but are you saying uncollected pipes into air or collected single pipe into air?
If uncollected, it depends on the length. The pulses will help flow at different certain rpm ranges for each. This is why the newest Ferrari's have varible exhuast systems to broaden the power over a larger rpm over a non-varible system.

Anyway if they collect into a single pipe into open air...
They will make different power peaks and one will probably have more lowend then the other. One will probably have more highend then the other. It also depends on the extent of porting and other factors...

 

well all i can say is that im my mind thats how things work. right or wrong i dunno untill i ask


as for collected or not whatever, again i dont thik it matters too terribly much

IMO the idea of longer for lowend i think holds true

look at any topfuel dragster/etc

again rant off

 

If you want real-world proof just look at wind instruments... you make the air-path shorter for higher frequencies. Heck just look at a pipe organ - the really long pipes are the low notes and the really short ones are the high notes.

If you want it applied to engines, look at multi-path intake manifold designs. There will be a short runner and a long runner and the engine operates off of the long runners at low RPM and switches to the short runners at high RPM. Audi has a system with a rotating barrel that allows infinitely variable intake runner lengths...

 

Am I wrong, did anyone read this???


Racing Beats direct quote:
I already have my own proof that my own long tubes on a bridgeport are giving more highend then before. The fact it is accerating much better above 4000rpm tells me that.

Peejays right though on intake systems, varible intake systems are important. Longer intake runners(in the correct length, meaning not too long) develop more torque is created by interia of the air flow/interia supercharging(a phomonom that will help a certain rpm range and hurt other rpms flow), and short ones create more highend by tuning the runners for high rpm interia supercharging. Its all trade offs unless you can utilize a varible length intake like on the MFR Racing slides.

The same is true with exhuast systems with a phomenon known as reverse interia supercharging which helps expell exhuast gases. If you are utilizing a "Full exhuast" not a open exhuast, things are different. Uncollected pipes lengths are completely different if you are just going to open air(VERY loud)
But pipes that collect ALSO have SCAVANGING which changes EVERYTHING. The flow pulses interact with each other and hurt each other at certain rpms and help at others. This is why that long tube Racing beat system makes more high end then a short tube collector with a full exhuast. Which also explains why you will loose low rpm power when you loose the stock manifold....was anyone reading that post about that?! THat collector is VERY short and isn't best for high rpm power, what the hell were you thinking? No flames intended. But when someone says shorter headers makes more power, you need to give a flowbench explaination.

 

You are thinking of frequency pitches!!! WTF? How the hell does that relate to flow paterns in a exhuast?

You make your pipes really narrow diameter is what cause the pitch to be high, the length on a trombone slide will effect the pitch only over several notes till you go to the next overtone/rate at which your lips are buzzing.
.. How do I know, I played trombone for 7years. The pitch of a music device created by a wind instrument
doesn't relate to flow in the exhuast system very well. All those rice mobiles that have 5inch fart holes to deepen the note. Very narrow pipes have a lot of velocity and not much CFM. But large pipes all things being equal, don't have much velocity but a lot of CFM. Too large doesn't help, too small doesn't help. We are dealing with pulses in exhaust, in a instrument, you are blowing a constant flow...and no where near its peak CFM I might add.

The smaller diameter pipes will be better for lower power to some extent...all things being equal. Where as large diameter pipes..all things being equal, will help higher end power. We didn't even go into length... Length and diameter together are going to scew out what point your trying to point out.


Where the hell can you make a comparsion of sound to flow?? Are you telling me a trumpet piping will flow more then a tubas?

 

PJ is right. Short primaries = max hp is achieved at HIGHER rpm. The first thing I noticed when I switched from RB short primary exhaust to long primary was MORE low end power. As a general, well known exhaust rule: The longer your exhaust system, the lower you'll have to rev your engine to achieve peak hp.

Key words when reading RB's site is STREETPORTED ENGINE. The dual setup has the potential for more flow... that's where they're getting a claimed 5hp increase over the short primary setup.

 

No, long primaries = better top end. Just think about the most high tech race cars out there like F1, CART, IRL, They have the longest headers you'll ever see and they designed the power curve to be optimal at high RPMs. F1 cars for example redline at around 17k, they don't even make power below 12k yet they have the longest primaries possible.

 

Cars in IRL and F1 have headers tunned to specific lengths that take into account all factors and effects of exhaust length tunning on 16,000+ rpm engines... they are neither long nor short. We are talking about engines that live in the 3-8000 rpm range.

 

Peejay's correct... short headers=high rpm tuning, long headers=low rpm tuning. If you don't understand this I suggest you go read Yaw's tech articles. I can't be stuffed typing an explanation.

And Rxcetera pretty much hit the nail on the head. High rpm gains from a long-primary system (especially on ported engines) are due to increased flow... not resonance pulse tuning.

 

Then what does it mean on i think its like P. 25 of Jim downings book when they talk about using leangths of like over 110 inches on bridge ports and like 95 for pp's? It sounds like long systems make more higher end. So are you guys saying that on those typr of engines they are "tuning" the lower end? I dont think so cus if you have ever driven a pp there is not much there to tune, you basicaly want as much top end HP as possible there for using the proper exhaust which according to Jim (who is somewhat knowledgable(undersatement)) is long header = high end.

CJG

 

Well, the problem with the others info is that they are all getting their info from Paul Yaw info data. All of that data is based primarily on stock port 12a's or street port. His whole info is derived from that.



THis is more what I'm stating in this thread. Bridgeport tuning and other serious overlap/duration engines are going to benifit differently from different exhausts. It also has to do with if the pipes are collecting or not. In Yaws site, we and he assumes the pipes are collecting which changes things.

If anyone has ever taken a automotive research class..."me"...you will find out about air flow testing and superflow flowbenches...etc. etc. But when it comes down to length's and such, there is a phonomon known as "Dynamic flow effects". I'm going to explain intake runner lengh tuning here instead of exhuast because no one here aparrently knows much, however it can be appied to the exhuast with different numbers for better flow through the ehaust.

. ...but anyway, engine volumetric efficiency and power can be increased considerably by taking advantage of the natural dynamic effect which occurs. Both the kinetic and resonant pulses can be harnessed to get efficiencys of 130%!..more so on a rotary ~150%..thats boost fellas!

...which is natural forced induction by means of intake length tunning. Anyway, I'm not going to recite things but to use the pulse to your advantage, it will need the correct length, however, it will only help through a narrow range of rpm. SO synochronizing it to be in the "2nd harmonic" is best and is done by dividing the rpm for Peak power as determined from flow measurements by 132,000. So a engine that peaks at 8000rpm would be 16.5inches. BUT, this caluation is based on a V8 engine with common overlap and not a bridgeport or PP port with massive overlap. IT can be tuned for the 3th and 4th harmonic but should be done for the 2nd harmonic since the others are weaker and shorter.

 

Forgot to write this but, it wouldn't let me edit...The stock duration and overlap is were Yaw shows all the numbers and figures are from basically.

Yaw keeps all his important data secret(who wouldn't?!)...so people will come to him for help and pay for intelligence. Theres nothing speical about what he does, any smart tuner knows how to use a flowbench, dyno, and where to go next..its just a matter of time aquiring data and appying it. Anyone would who put lots of work into this field would keep there hard earned data secretive. OTherwise you are potentially giving your comptetors the same edge and not make any money from the data you've spent endless hours acquiring. Most of his "posted" data is based on stock 12a's like I said. Since the stock 12a has limitations, and they are everywhere, he sees no harm in displaying a lot of data on that. He is well aware of how tuning a exhuast will change dramatically when you start porting and getting overlap as you may or may not guess.

 

Good Point. Mazda realized this back in 1986 with the 2nd Gen Intakes. On the N/A engines, the"Dynamic Chamber" actually produces up to 1.5lbs of boost, as a natural supercharging effect brought about by the intake plenum shape. Even more so with the 89+ engines.

This was one of the largest improvements over the GSL-SE's RE-EGI square shaped Plenum chamber.

That's why if you're gonna run an N/A Fuel Injected intake, the 89+ is the best for most power (and largest )