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Old 07-18-2008, 11:46 AM   #1
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Default Cast or tubular manifold?

Hi all,

I think I will replace rather than repair my warped and cracked (second time) used JGS manifold. I have a 94 running a T360 at 16-18 psi.

I am looking at the BEGI cast and the ETD shorty manifolds. The BEGI looks bulletproof but the ETD looks like it will flow a bit better. What is the real world difference in terms of horsepower at the same boost levels between these? The BEGI puts the turbo closer to the engine and lower which is an advantage. BEGI also sells downpipes. With the ETD I can probably use most of my existing intake and IC pipes. I may have to modify my downpipe or make a new one though.

Also what is the real difference in horsepower between internal vs. external wastegate and divorced gases vs. single pipe if you use an internal? Right now I am running up to 18 psi with pretty good boost control using the internal setup; no boost creep. 15psi actuator on the internal gate, AEM ecu, RX7 550 cc injectors, GM boost solenoid.

Thanks,
Barry
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Old 07-18-2008, 01:14 PM   #2
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Manifolds,wastegates and downpipes have no effect on hp.

I would go with a log from a reliability stand point, tubular is nice but I wouldnt want to tear into my car because it cracked. Wastegates is all about how big your turbo is, how much your exhaust can flow etc etc. Downpipes affect spool for the most part.
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Old 07-18-2008, 01:19 PM   #3
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you've been smoking crack lately haven't you. First the intake manifold comment and now this....
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Old 07-18-2008, 01:21 PM   #4
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Quote:
Originally Posted by Saml01 View Post
Manifolds,wastegates and downpipes have no effect on hp.
You are wrong. They directly influence flow, and HP is related to flow. Put a peashooter size DP on your car and see if you can tell a difference.

Maybe you should stop dispensing "wisdom".
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Old 07-18-2008, 01:44 PM   #5
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I can't answer the first part of your question as far as numbers go. But if your goal is just trying to have a reliable, long lasting, and low maintenance turbo system, I'd personally go with a log manifold. Also because you can get supporting parts easily as you stated. The ETD will flow better, so there is power to be had there. It all just comes down to what do you really want and paying for it.

The main reason someone would choose an external wastegate over an internal is consistent boost control, not so much for HP gain. However, with an external gate, the flow that comes out of the gate is reintroduced into the exhaust stream later on (or atmospherically dumped), and causes less turbulance in the flow which helps power. That same concept is applied between the single and divorced pipes. I can tell you that at 15psi, when I switched from my old FM single downpipe to my BEGi divorced pipe, there was one hell of a difference in the way the car pulled.
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Old 07-18-2008, 02:24 PM   #6
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Quote:
Originally Posted by Saml01 View Post
Manifolds,wastegates and downpipes have no effect on hp.

I would go with a log from a reliability stand point, tubular is nice but I wouldnt want to tear into my car because it cracked. Wastegates is all about how big your turbo is, how much your exhaust can flow etc etc. Downpipes affect spool for the most part.
Dear Sam's GF who doesn't want him to spend money on his car: leave his miata.net and miataturbo.net accounts alone.
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Old 07-18-2008, 02:45 PM   #7
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Quote:
Originally Posted by Saml01 View Post
Manifolds,wastegates and downpipes have no effect on hp.

I would go with a log from a reliability stand point, tubular is nice but I wouldnt want to tear into my car because it cracked. Wastegates is all about how big your turbo is, how much your exhaust can flow etc etc. Downpipes affect spool for the most part.


I'd go with the cast, even though my manifold is tubular.
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Old 07-18-2008, 02:58 PM   #8
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Quote:
Originally Posted by johndoe View Post
you've been smoking crack lately haven't you. First the intake manifold comment and now this....
Quote:
Dear Sam's GF who doesn't want him to spend money on his car: leave his miata.net and miataturbo.net accounts alone.
seriously sam....what gives?!
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Old 07-18-2008, 03:07 PM   #9
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Quote:
Originally Posted by johndoe View Post
you've been smoking crack lately haven't you. First the intake manifold comment and now this....
What intake manifold comment?

------

Now I admit, I could be wrong. Hell if im wrong you can correct me. But, from what I see, people are gaining faster spool times from larger exhausts. What I understand is that as long as you get your turbo spooled sooner or later you can make the same "peak power" on a restrictive exhaust. You wont have the same powerband, but peak hp will be the same.

UNLESS... a restrictive exhaust can hinder the top speed of a turbine. Then everything I said is totally wrong and I accept that.

As for the manifold thats to each his own. marginal improvement in spool vs reduce reliability, different strokes for different folks.

Wastegate, comment there is nothing wrong with, just half assed answer. I apologize

Are you guys seriously bending me over because of the downpipe and exhaust?

Quote:
Originally Posted by Braineack View Post
seriously sam....what gives?!
You know me well enough, I dont say things unless thats how I feel. I could be wrong, and I would rather be wrong here and corrected. Then be wrong in front of people talking face to face. I want to spur discussion, hopefully after the flames

Last edited by Saml01; 07-18-2008 at 03:21 PM.
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Old 07-18-2008, 03:14 PM   #10
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I certainly didnt make any extra power with my exhaust....

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Old 07-18-2008, 03:17 PM   #11
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a restrictive exhaust easily slows the speed of the turbine...

if the gases arent flowing freely out the tailpipe, both the turbo and motor waste energy pushing it out.

the motor has to push the exhaust out of the head, so less torque from teh pistons, and the turbine does spin as fast, so slower spool and power output....

lose lose.
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Old 07-18-2008, 03:25 PM   #12
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Quote:
Originally Posted by Braineack View Post
a restrictive exhaust easily slows the speed of the turbine...

if the gases arent flowing freely out the tailpipe, both the turbo and motor waste energy pushing it out.

the motor has to push the exhaust out of the head, so less torque from teh pistons, and the turbine does spin as fast, so slower spool and power output....

lose lose.
Then I stand corrected. As always I am in your debt.
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Old 07-18-2008, 03:49 PM   #13
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lets break it down real simple:

power comes from controlled ignition of gasoline raising the heat energy inside the cylinder and converting that energy into linear motion by expanding above the piston.

now here's the important part:

ALL OTHER FUNCTIONS OF AN ENGINE REDUCE THE NET POWER GENERATED FROM THIS PROCESS.


why?
moving gases through piping, ducts, valves, nozzles, whatever requires energy. in or out doesn't matter. you're either sucking it in or pushing it out. restrictions on either end lower the power efficiency. even turbos (they just raise the gross power before subtracting out their losses).

so to maximize net power you can either raise the gross or lower the losses. both is best. that means the most efficient flow path in and out of the engine and a big fat turbo.
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Old 07-18-2008, 04:03 PM   #14
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Sick explanation.

So that means im ordering a begi manifold in the near future.
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Old 07-18-2008, 04:44 PM   #15
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paul's absurdflow manifold and exhaust is all the proof i need.
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Old 07-18-2008, 05:10 PM   #16
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I was sold when i saw how big his....what the?!
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Old 07-18-2008, 05:13 PM   #17
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Quote:
Originally Posted by budget racer View Post
paul's absurdflow manifold and exhaust is all the proof i need.
Isnt he running a begi manifold?
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Old 07-18-2008, 05:19 PM   #18
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Not on the machine, it is all about the absurdflow!!!
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Old 07-18-2008, 05:19 PM   #19
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intake manifold, yes.
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Old 07-18-2008, 05:37 PM   #20
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Quote:
Originally Posted by Zabac View Post
Not on the machine, it is all about the absurdflow!!!
Nobody is able to hit 10psi on a GT2560 @ 3rpm on a begi manifold?

I get the above numbers from compuatics thread with his spool problems.
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