Single Turbo RX-7's Questions about all aspects of single turbo setups.

short runner manifold

Old 12-13-10, 05:00 PM
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Originally Posted by neukin View Post
Why is it pointless? Guess the HKS engineers messed up too. Please teach me something.
The sole function of a wastegate is expell exhaust gas once a desired boost level is reached... If the manifold is a true divided manifold, and only one of those runners exits to a wastegate, then you're basically doubling the time it would take to effectively expell the excess gasses, as half of pulses (1 of 2 runners) completely reaches the turbo... 100% of the exhaust from the runner WITHOUT the wastegate exit is reaching the turbo... whereas most of the exhaust from the runner WITH the wastegate exit is being evacuated to compensate. You now have two different energy levels, one greater than the other, giving you a less than efficient exhaust wave to the turbo.
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Old 12-13-10, 06:42 PM
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He does have WG runners on both runners, though they rely more on pressure than flow. You can get around the pulse or wave issue by having equal length WG runners as well. We noticed no real gain in response by running a divided twin gate setup versus a divided single gate setup. We might have if we stepped down to smaller gates.

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Old 12-13-10, 07:01 PM
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think about this...a true divided manifold...is well..divided..when you have 2 WG runners merge via another collector...that then bridges the 2 runners pressure wise...thus...you dont have a true divided manifold anymore and it would have been far simpler to just use a non divided flange/turbo...
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Old 12-13-10, 09:22 PM
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A argument can be made both ways... having a point where both "cylinders" meet, can equalize the pressure. Saying that you're not gaining anything by running a divided manifold with a collected gate is simply not true. Running equal length primaries as well as secondaries will work just as good for the most part, only really being effected by overall flow once the gate is open. Arguments have been made that running a divided manifold on a undivided housing are no good as well and you might as well run a collected manifold. Again not true. Running a divided manifold on a undivided housing will improve response over a collected manifold on a undivided housing.

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Old 12-18-10, 03:55 PM
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I"m also int eh market for a divided short runner manifold

I don't think i'll be running anything bigger then an hx40 or an s362 BW.

Steel or SS doesn't matter as it'll be ceramic coated anyway
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Old 12-26-10, 01:43 AM
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So i found what i have been looking for in a manifold. 7in equal length runners, equal degree bends, 2in inner diameter, schedule 40piping, and tear drop waste gate flanges.
MINES
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Old 12-26-10, 10:26 AM
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vince @ CTD made that manifold...vince is a way talented welder/fabricator
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Old 12-26-10, 01:31 PM
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Originally Posted by Zero R View Post
A argument can be made both ways... having a point where both "cylinders" meet, can equalize the pressure. Saying that you're not gaining anything by running a divided manifold with a collected gate is simply not true. Running equal length primaries as well as secondaries will work just as good for the most part, only really being effected by overall flow once the gate is open. Arguments have been made that running a divided manifold on a undivided housing are no good as well and you might as well run a collected manifold. Again not true. Running a divided manifold on a undivided housing will improve response over a collected manifold on a undivided housing.

~S~
I have had quite a bit of experience with single gate setups on divided manifolds and I can say that there really isn't any benefit besides only having to purchase one gate and maybe the space saved. On two separate occasions where cars were dynoed before and after going from a single collected gate to a true divided twin gate manifold they picked up quite a bit of mid range response and power. One test was on Forrest ****'s drift 240 and the other on AFI's time attack S2000. One wrench to throw in the mix however is the type of engine these manifolds were bolted onto.

I don't claim to know much about the inner working of the Wankel but i do know that they output very different exhaust pressures and velocities than piston type engines. I believe this is why a short runner turbo manifold with a minimal pressure drop will shine and outperform pretty much anything out there. These pressures and velocities also might be the answer why a collected wastegate on a divided setup may not have much of a negative effect.

From a manufacturing fabrication point of view collected gates make little sense. There are many aspects like efficiency of fabrication, space constraints, and stress on the waste gate collector ect...

If you are thinking well then i'll just put a divider plate into the wastegate collector than I tip my hat to you and say good luck. While a divider would truly divide the whole manifold they are subject to a massive amount of heat and stress from the alternating pulses between the two runners. I have personally seen these dividers melted, mangled and torn into little tiny pieces. When you reach a thickness that will work (3/16+), it cuts down on the internal volume a noticeable amount. Compound that fact with the obvious fact that you are still running a single gate that has to deal with two runners. Compound that even further with the fact that the wastegate runners to collector angle is far from optimum for efficient bypass.

Dual gates
Dual Tear drop
Semi-Priority gate placement

Pretty much game over if you ask me


Oh and quite a few OEM turbo cars run divided turbo manifolds to undivided turbos, sr20, rb20-25. I love to make divided manifolds for internally gated turbos. The name of the game is mixing, whenever you can keep exhaust pulses from ******* with each other you will benefit.

Last edited by CTD Fabrication; 12-26-10 at 01:35 PM.
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Old 12-27-10, 02:51 PM
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Originally Posted by BOOSTALMIGHTY7 View Post
Ctd do you make long runner manifolds?
eww this is a short runner thread no long runners allowed haha. if you dont mind me asking why wouldn't you want to go with a short runner?

Originally Posted by CTD Fabrication View Post
Hey thanks Aaron! Thanks again for the opportunity to have another crack at an FC manifold, its amazing what you can do when you learn from your previous mistakes.

Comparing this manifold to the previous is like apples to oranges and it showed even when starting the car for the first time with the new kit. The car seemed to start easier and it was quite a bit smoother. Aaron texted me later that night about how much smoother it drove and how the turbo felt more responsive.


I can't wait to see some dyno numbers and graphs

Oh and any questions about manifold cost/buying stuff like that just PM me. I'm not a vendor on here and would not to step on any toes. thanks guys


Vince
No problem man this was what i was looking for in a manifold haha and you jus happen to be making it haha. Plus with all the time you put into my car besides the manifold i cant complain at all.
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Old 12-27-10, 04:35 PM
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Closing this thread down (at least temporarily) because it turned into an unpaid advertisement.

CTD Fabrications/Vince, welcome to the forum..... if you're interested in becoming a vendor and advertising your services, please click here:

https://www.rx7club.com/showthread.php?t=897023

Feel free to PM me with any questions
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Old 01-07-11, 10:44 PM
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Thread reopened guys...... let's keep it informative, and please there is no place on this forum for unpaid advertisements. OP (or any other customer) you are more than welcome to share with us info/specs/pics about your new manifold/turbo/whatever. But--- any business or vendor who wants to talk/push product would need to become a paid site vendor, it's only fair to the companies that do pay every month in order to be able to operate on this site.

I'm all for freedom of speech, innovation, and sharing knowledge amongst the rotary community.

That being said, have at it
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