Downpipe tech... FM Turbine outlet vs 3" elbow vs BEGI Separated
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I am having a 3" downpipe and exhaust fabricated for my car locally and I am wondering what is the ideal way to solve my problem.
Specifically this discussion is in reference to an internally gated turbo like the GT2650 or 2860. MY main goal is reducing time to boost target. Peak HP/Torque is but a bonus.
One method is the BEGI method where the wastegate gasses are routed via a separate tube into the exhaust down stream.
Another method is the Flyin' Miata Turbine outlet which uses a separate cast elbow and from there the downpipe bolts onto the bottom. I am unsure how large the outlet of the casting is.
The last is the big open elbow method which is taken by some people here.
Is there any benefit to separating the gasses until downstream? How does the "big elbow" method compare with the BEGI and FM methods? IF I decided to just use a FM cast outlet and have the rest fabricated in 3" from that point on, will I be losing any measurable power or boost latency?
If this were a smart person discussion of downpipe design, what would we be talking about?
Specifically this discussion is in reference to an internally gated turbo like the GT2650 or 2860. MY main goal is reducing time to boost target. Peak HP/Torque is but a bonus.
One method is the BEGI method where the wastegate gasses are routed via a separate tube into the exhaust down stream.
Another method is the Flyin' Miata Turbine outlet which uses a separate cast elbow and from there the downpipe bolts onto the bottom. I am unsure how large the outlet of the casting is.
The last is the big open elbow method which is taken by some people here.
Is there any benefit to separating the gasses until downstream? How does the "big elbow" method compare with the BEGI and FM methods? IF I decided to just use a FM cast outlet and have the rest fabricated in 3" from that point on, will I be losing any measurable power or boost latency?
If this were a smart person discussion of downpipe design, what would we be talking about?
Last edited by Chiburbian; 12-04-2014 at 08:51 AM.
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Thanks. The question is though, will the added complexity of the dual tube design cost me too much in money to be worth it?
FM housing costs $220 plus $550 "three inch conversion" kit. Add a cat and complete the midpipe... Yikes!
BEGI version goes for $550 + $85 three inch conversion. The separated gasses thing looks pretty complex to fab up correctly. I imagine the reason the BEGI design costs what it does is that they solved the problem already and can jig it up for additional builds.
All together this is looking expensive. :(
FM housing costs $220 plus $550 "three inch conversion" kit. Add a cat and complete the midpipe... Yikes!
BEGI version goes for $550 + $85 three inch conversion. The separated gasses thing looks pretty complex to fab up correctly. I imagine the reason the BEGI design costs what it does is that they solved the problem already and can jig it up for additional builds.
All together this is looking expensive. :(
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just get the elbow and fabricate the rest. that's what I would do. I have the elbow, and its a great piece
is it worth it? no.
if you're really looking to make some serious power you shouldn't even be messing with this configuration. you should be looking at a top mount tubular or bottom mount or absurdflow style
is it worth it? no.
if you're really looking to make some serious power you shouldn't even be messing with this configuration. you should be looking at a top mount tubular or bottom mount or absurdflow style
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What spurred this on was Blaen99. He is using the same manifold I am using but with a 3" exhaust.
Honestly I am totally happy with his numbers. I haven't even built my motor yet so I can't even push it, I just figured this upgrade would give me a bit of spool and would not mean replacing tons of stuff later after I built the motor. You are making me question my thinking. My end goal is "only" mid 300s...
Honestly I am totally happy with his numbers. I haven't even built my motor yet so I can't even push it, I just figured this upgrade would give me a bit of spool and would not mean replacing tons of stuff later after I built the motor. You are making me question my thinking. My end goal is "only" mid 300s...
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So what's your current exhaust? BEGI's 2.5" dp and exhaust?
Have you considered going with Artech? That's what Jared has if you were happy with his results.
He also says there is some warping on perhaps both manifold and turbo surfaces from before he installed the TSE studs, so that will only hurt build up of boost.
Have you considered going with Artech? That's what Jared has if you were happy with his results.
He also says there is some warping on perhaps both manifold and turbo surfaces from before he installed the TSE studs, so that will only hurt build up of boost.
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This upgrades the piping to 3" from the turbine elbow
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Flyin' Miata : Turbochargers : Parts and upgrades : Hybrid to full 3 inch exhaust upgrade
This upgrades the piping to 3" from the turbine elbow
This upgrades the piping to 3" from the turbine elbow
Oh. So that still goes on the same cast turbine elbow? I wonder if you can get just the 3" downpipe and not the cat. Pretty sure i have that in a box in the garage.
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Great, that makes sense. Looks like I will be getting the FM elbow and either buying their 3" kit or having the rest of the downpipe fabbed.
I DO want a catalytic converter. Maybe not that specific item though so I will talk to FM and see what they say.
I DO want a catalytic converter. Maybe not that specific item though so I will talk to FM and see what they say.
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76mm downpipes can fit without modifying the shelf with axial logs. It depends on how the axial log is made and how the turbo is positioned.
On typical cast logs the t2 flange is set higher than the center of the manifold by an inch or so. Is this significant? Yes as it reduces the clearance available for the downpipe as can be seen in the following sketch. (red line is shelf/firewall)
![](https://www.miataturbo.net/attachments/diy-turbo-discussion-14/128702-downpipe-tech-fm-turbine-outlet-vs-3-elbow-vs-begi-separated-downpipe_zps0f08e6a9.jpg?dateline=1417720440)
Also in this case the turbo is rotated by 10 degrees. This means that the downpipe angle leaving the turbo is 55 degrees as opposed to 90 degrees and more in some of the other types.
It is possible to fit 80mm downpipes by keeping the T2 flange at port center and rotating the turbo 10 degrees.
On typical cast logs the t2 flange is set higher than the center of the manifold by an inch or so. Is this significant? Yes as it reduces the clearance available for the downpipe as can be seen in the following sketch. (red line is shelf/firewall)
![](https://www.miataturbo.net/attachments/diy-turbo-discussion-14/128702-downpipe-tech-fm-turbine-outlet-vs-3-elbow-vs-begi-separated-downpipe_zps0f08e6a9.jpg?dateline=1417720440)
Also in this case the turbo is rotated by 10 degrees. This means that the downpipe angle leaving the turbo is 55 degrees as opposed to 90 degrees and more in some of the other types.
It is possible to fit 80mm downpipes by keeping the T2 flange at port center and rotating the turbo 10 degrees.
![](https://www.miataturbo.net/attachments/diy-turbo-discussion-14/128703-downpipe-tech-fm-turbine-outlet-vs-3-elbow-vs-begi-separated-p1050615_zps1497e068.jpg?dateline=1417720440)
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Neat William. Your downpipe is what I was thinking of as a true 3" from the flange style actually.
Just got off the phone with FM. Looks like I will be going with their stuff unless my fabricator puts the kabosh on it.
Just got off the phone with FM. Looks like I will be going with their stuff unless my fabricator puts the kabosh on it.