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Old 01-11-2010, 08:03 PM   #21
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Oh ok so that doesn't apply to me anyways since I'm only looking for a mani. Thanks, I've been a v8 guy for years and this is my first turbo car. Still learning
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Old 01-11-2010, 08:05 PM   #22
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Thanks Sav.
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Old 01-11-2010, 08:07 PM   #23
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So how much more is it for a t3 external wastegate added to that?
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Old 01-11-2010, 09:19 PM   #24
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Originally Posted by jtothawhat View Post
I really don't agree, I think a Ramhorn will outflow the "AbsurbFlow" design and certainly the ETD, I had an ETD and can tell you the inside of the runners/collector was not smooth what so ever; gaps, roughness, etc there are many 700+ hp cars running ramhorn style manifolds they just make power higher in the powerband. Maybe for 250-300 whp AbsurbFlow would be the better bet due to shorter runners and quicker spool.
It is my position that the longer the runners, the more the restriction. But I could be wrong.
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Old 01-11-2010, 09:36 PM   #25
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I smell a scientific experiment. I may just have to make both of them and get 2 dyno plots with everything else constant.
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Old 01-11-2010, 09:45 PM   #26
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It is my position that the longer the runners, the more the restriction. But I could be wrong.
I agree and also the longer it takes the exhaust pulse to hit the turbine.
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Old 01-11-2010, 11:38 PM   #27
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^
While what you say is may be true, I base my opinion off results; several high horsepower cars (over 700 hp) run ramhorn designed manifolds. Most are based off equal length runner design. For what more members are using there cars for on the forum ABSURDFlow could be the better manifold when it comes to spool and hp/tq lower in the RPM range, but when it comes to peak power ramhorn for the win. I can say for a FACT ETD manifold should not be even compared to ramhorn when it comes to flow, the inside of the runners/collector look like ****.
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Old 01-12-2010, 09:08 AM   #28
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Quote:
Originally Posted by Braineack View Post
It is my position that the longer the runners, the more the restriction. But I could be wrong.
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Originally Posted by wayne_curr View Post
I agree and also the longer it takes the exhaust pulse to hit the turbine.
I agree with these two statements and will add the greater number of bends, the more the restriction.

The longer the pipe, the more it will bbuuuzzzzzz. Harmonics are a bitch with these engines.
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Old 01-12-2010, 09:12 AM   #29
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I smell a scientific experiment. I may just have to make both of them and get 2 dyno plots with everything else constant.
That'd be cool as I have little interest in spending the time & effort on that. If it turns out the ramhorn is better, that makes our lives much easier.
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Old 01-12-2010, 09:33 AM   #30
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Quote:
Originally Posted by jtothawhat View Post
^
While what you say is may be true, I base my opinion off results; several high horsepower cars (over 700 hp) run ramhorn designed manifolds. Most are based off equal length runner design. For what more members are using there cars for on the forum ABSURDFlow could be the better manifold when it comes to spool and hp/tq lower in the RPM range, but when it comes to peak power ramhorn for the win. I can say for a FACT ETD manifold should not be even compared to ramhorn when it comes to flow, the inside of the runners/collector look like ****.

These points all have merit and I'm not an expert, I just read articles like these:

Quote:
Turbo Manifold Design

Start talking about turbo exhaust manifold design and people have all sorts of theories. Most say that equal-length, long runners should be used – irrespective of the length of runner that then results. But others say runners should be grouped on the basis of firing order. Sounds easy – until you ask some questions. Like, grouped exactly how on the basis of firing order? Or, how important is it that the runners are of equal length? For example, is it more important that runner length be equal – or the runners are organised to provide the best flow? After all, the longer the runner, inside a typical engine bay the more bends it’s likely to have in it and the greater resistance it will pose to flow.
Let’s take a look at what the experts actually have to say.


The original bible of turbocharging is Turbochargers, by Hugh MacInnes (published by HP Books). Despite being first published in 1978 – and so containing almost nothing that relates to EFI engines – the core content of the book has stood up surprisingly well in the years since. MacInnes suggests that turbo exhaust manifolds should use small diameter runners with about the same internal area as the ports and that in turbo engines, the use of “smooth flowing exhaust headers with beautiful swerving bends.... is more aesthetic than power-increasing”. Except for V8 engines, he makes no comments at all about grouping the flow from cylinders in any particular manner.


Another old book is Turbocharging and Supercharging, by Alan Allard (first published by Patrick Stephens in 1982). Allard says: “The main criteria when designing and fabricating an exhaust manifold are: firstly, to build in sufficient strength to take the weight of the turbocharger system and to remain rigid without distortion or fracture even when working up to 1000 degrees C; and secondly, to have sufficient wall thickness (3.0mm minimum is recommended) to withstand the corrosion effects of running up to high temperature over a long period.”
Allard suggests the use of a log-type manifold pipe of not more than 2.5 times, and not less that double, the area of one exhaust port. The log is joined to the individual exhaust ports with stubs with the same inside diameter as the exhaust ports, each as short as possible and of equal length. The stubs can enter the log at right-angles or be angled towards the turbo.


However, while not mentioned in the text, a diagram shows a 1-3-4-2 firing order four cylinder engine using a manifold where cylinders 1 and 2, and 3 and 4, are paired and fed to a split-pulse turbine. In addition, again while it is not discussed in the text, many turbo racing engines are shown where equal-length long runners join at a common collector just prior to the turbo.


Automotive Supercharging and Turbocharging Systems was first published in 1992 by Motorbooks International. The author is John Humphries. Of my references, this book provides the most detailed treatment of turbo exhaust manifolds. However, rather than making things clearer, if anything it further muddies the waters! The book suggests that there are two fundamentally different approaches to turbo exhaust manifold design.
The first is to use a manifold with sufficiently large internal volume that the exhaust output pulses of each cylinder are damped and a more or less constant pressure is available to the turbine. The internal volume of the manifold sufficient to obtain this pulse dampening can be 1.4 – 6 times the swept volume of the engine. That rules out pretty well all long runner exhaust manifolds, although a log-type one of the sort suggest by Allard may fit into the bottom end of this scale, and the current fashion in the US for mounting the turbo at the back of the car (in a car with a front engine!) would also conform to this approach.
The second approach is a pulse system, where the exhaust pulses provide additional short-term energy to the turbine. In a pulse-type manifold, Humphries suggests that the pipe runners should have a “cross-sectional area....not significantly greater than the geometric valve area at full lift [and] these connections should be kept short and free of sharp bends”.
He says the reflection of pulses within the system will be determined by pipe length, exhaust temperature and the status (ie open, closed or partially open) of the exhaust valves. In addition, at pipe junctions the exhaust pulses will split, with smaller magnitude exhaust pulses travelling down each pipe. “The overall pressure wave system that occurs in such a manifold will be very complex, with pulses propagating from each cylinder, pulse division at each junction, total or partial reflection at an exhaust valve...and reflection from the turbine.”
In order to take advantage of this pulse flow, “narrow pipes from several cylinders can be connected through a single branched manifold to one turbine....a four stroke engine which can have its cylinders grouped into threes is particularly attractive.” This is because “the opening periods of the exhaust valves follow successively every 240 degrees with very little overlap between them.... thus a sequence of pressure pulses arrives at the turbine...”


Humphries suggests that the use of twin turbos on a six cylinder engine allows for efficient pulse operation, and where cylinder multiples are not in threes, a single turbo entry can be linked to multiple cylinders through “pulse converters”. Pulse converters are suitably shaped junctions which prevent reverse pulse flow. Humphries shows a four cylinder exhaust manifold with cylinders 1 and 2, and cylinders 3 and 4, paired and then coming together through a pulse converter junction.


One of the more recent books on turbocharging is Corky Bell’s Maximum Boost (published by Robert Bentley, 1997). Bell suggest that it is important the manifold retains heat, prevents reverse flow (eg by the use of so-called reversion cones in the first section of each runner), and is designed to minimise thermal loads on each section of the manifold. The latter can be achieved by the use of runners from each cylinder travelling separately to the turbo inlet – that way, each runner is subjected only to the heating loads of one cylinder. It is implied but not stated that controlling these heating loads is more important than flowing the individual pulses in a sequence to the turbine – in the diagram the pipes are of unequal lengths.
Bell also says that the experience with turbo F1 cars suggests that “the best manifolding is multiple-tube, individual runner style”. As with the other authors, he recommends the use of relatively small diameter runners with large wall thicknesses. With regard to pulse tuning, he says “a design that allows exhaust gas pulses to arrive at the turbine at regularly spaced intervals is ideal but difficult to achieve”.
So what does one make of all of that?
Firstly, it’s clear that these authors agree that the use of heavy wall tube (“steam pipe”) bends are preferable to thin gauge materials. Secondly, the individual cylinder runners should be sized smaller rather than larger, being near to port size. It also appears that if it is possible within the confines of the engine bay, equal-length runners that join at the turbo are to be recommended. In six cylinder engines, the grouping of two pairs of three cylinders to feed either two turbos or a single split-pulse turbine housing is to be favoured.
However, unequal length runners are extremely widely used (few if any factory turbo cars have equal length runners in their cast manifolds) and some aftermarket tubular manifolds use branchings of unequal length runners. (Most of the latter are dubbed ‘pulse converter’ manifolds but whether the internal junctions conform to pulse converter geometries is not known.) Not one of the best known references is particularly critical of exhaust manifold designs which on a naturally aspirated engine would be seen as fatally flawed.



And what you suggest about the shorty might be correct as well, I could probably put it under the ramhorm styles, but definitely above the cast manifolds.
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Old 01-12-2010, 09:44 AM   #31
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These points all have merit and I'm not an expert, I just read articles like these:
Can you cite the source of the above post, or did I misunderstand and it's you?
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Old 01-12-2010, 09:57 AM   #32
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not me, im dumb. that was on the autoblog.
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Old 01-12-2010, 11:29 AM   #33
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Well this turned into an informative thread. Thanks for all the contributions guys
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Old 01-12-2010, 11:39 AM   #34
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That article doesn't agree with the order of half on that list. This is the current bible for manifold builders, but good luck finding it for anything close to retail.

Theory of Engine Manifold Design: Wave Action Methods for IC Engines
by Desmond E. Winterbone, Richard J. Pearson, Sir John Horlock
# Hardcover: 512 pages
# Publisher: John Wiley & Sons (July 18, 2005)
# Language: English
# ISBN-10: 1860582095
# ISBN-13: 978-1860582097

My understanding is that axial collectors like those used on the Absurdflow manifold (often used on sportbikes) are used for clearance purposes since they have a very small profile, while radial collectors, like those on a ramhorn, are the best for performance. A smooth bend is not as much of a restriction as exhaust waves colliding against each other at a steep angle, so the smaller the merge angle, the better it will flow.

Look at some drag racing setups, turbo or na. The manifolds are a snake orgy. Why would they use a restrictive design?



SKmetalworks, I'd be willing to donate a manifold/dp for testing if you ever get around to doing it.
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Old 01-12-2010, 11:56 AM   #35
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^^ I think that's a Bisi Moto header, he made over 350 whp on a SOHC Honda motor N/A.
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Old 01-12-2010, 12:38 PM   #36
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^^^ nope...AN-R...or better yet...a bisi knock off.
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Old 01-12-2010, 01:30 PM   #37
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My track car needs to be finished in a month for the novice school so I am going to be busy for a little while. I'm gonna take a week.off work to bust ***
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Old 01-12-2010, 02:29 PM   #38
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Quote:
Originally Posted by ARTech View Post
My understanding is that axial collectors like those used on the Absurdflow manifold (often used on sportbikes) are used for clearance purposes since they have a very small profile, while radial collectors, like those on a ramhorn, are the best for performance. A smooth bend is not as much of a restriction as exhaust waves colliding against each other at a steep angle, so the smaller the merge angle, the better it will flow.

This makes a good deal of sense. I do agree, the better the collector, definitely the better manifold.
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Old 01-12-2010, 03:10 PM   #39
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most of the studies looking over ramhorns vs the traditional logs is that the log spools up a weee bit faster, but after that... total loss compared to the ramhorn. lower rpms...lower flow... not really that much turbulence occurring in the log - - - but when higher flow happens, an equal length with a proper merge collector would totally organize the flow much more.
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Old 01-12-2010, 04:12 PM   #40
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Originally Posted by wherestheboost View Post
most of the studies looking over ramhorns vs the traditional logs is that the log spools up a weee bit faster, but after that... total loss compared to the ramhorn. lower rpms...lower flow... not really that much turbulence occurring in the log - - - but when higher flow happens, an equal length with a proper merge collector would totally organize the flow much more.
When talking about a standard log manifold you're damn skippy that its not going to flow as well. Just look at it.



I'm more intrigued by how this might flow and spool versus a ramhorn style.

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And I should be finding out fairly soon as i'm going to be hopefully building 3 or 4 of them as soon as some people get their **** together and buy parts. I'm not even charging for labor, just building them at cost for fun. Actually bob bundy built a manifold with the same concept for a 323 GTX so he should really chime in here. I dont want to post a picture of it without his permission.
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