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Old 12-11-2014, 02:26 PM   #21
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Originally Posted by shuiend View Post
I talked to JKav a good while back about bracing. If I remember correctly he was not a huge fan of cranes. Hew much preferred to use a mount that attaches to the engine block and goes up to the bottom of the turbo. I asked him for some pictures of how he was going to do it, but I never received them.
This is how they show it on the Edmunds long-term Miata (JKav); They have provisions where they are going to install a dive-board brace, but it does not appear to be fabricated yet. I really wish they would make more progress on this...

TiAL Sport Turbine Housing And Wastegate - 1997 Mazda MX-5 Miata Long-Term Road Test

This is similar to a previous iteration JKav had fabricated using all Burn$ components (including a Burn$ collector) in the early 2000's. IIRC this was featured in Sport Compact Car circa early 2004 on JKav's black miata. This was later sold to Jon (dv/dt on various forums) with a laguna blue miata. Tis manifold was a work of art. Unfortunately a previous hard drive took a dump and I lost all the pics.

Last edited by M2Ken; 12-11-2014 at 02:50 PM. Reason: remove duplicate information
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Old 12-11-2014, 04:29 PM   #22
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But it also increases the force of the exhaust swinging back and forth on the on the manifold since it basically turns the whole exhaust into a lever with a pivot. The flex pipe between the brace and the rest of the exhaust only gets you some relief of this. And also making a brace for this that doesnt break on a 3" exhaust is kind of hard.

There's an older thread on the subject where I had the idea to also hard mount the exhaust to the middle or back of the PPF to completely get rid of the effect and to more or less let the whole exhaust move with the engine but no one was buying it at the time. It pretty much operates under the assumption that without miss matched mount stiffnesses (IE engine and diff mounts are allow around the same amount of flex) that the PPF doesnt get twisted all that much while driving.
With no brace the entire length of the exhaust is the lever and the fulcrum is the width of the downpipe flange, and the leverage is pulling directly on the studs.

With a downpipe brace the leverage is 2/3rds of the exhaust to 1/3rd and the force on the turbo studs is attempting to shear them.

A bracestrong enough is easy, u bolt exhaust clamp and 3x15mm mild steel flatbar mounted on a u bolt bolt and a lower gearbox bolt. It goes through a 90 degree rotation allowing a little expansion but eliminates most of the swinging force. Of course a flex pipe goes behind the brace.

Whether the engine and diff mounts are of equal stiffness doesn't change the fact that the engine and diff rotate in opposite directions.

Dann.
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Old 12-11-2014, 04:40 PM   #23
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With the brace the exhaust moving makes close to a linear force on the turbo bits, without its almost entirely a moment (twisting) force. We already know the exhaust U bolt doesnt work.
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Old 12-11-2014, 04:51 PM   #24
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Doesn't work how?

I've tried lots of **** and the u bolt is the only thing this side of sleeving the exhaust to double it's wall thickness then using angle. Everything else fatigues the exhaust that I've tried.
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Old 12-11-2014, 04:52 PM   #25
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Also what are you worried about, the engine twisting or the exhaust swinging?
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Old 12-11-2014, 04:54 PM   #26
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Doesn't work how?

I've tried lots of **** and the u bolt is the only thing this side of sleeving the exhaust to double it's wall thickness then using angle. Everything else fatigues the exhaust that I've tried.
Everyone else with a fast car that has tried the u bolt has had it fail the exhaust. I think bundy found some like extra heavy duty type band clamps that worked but they're like over $100 each.

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Also what are you worried about, the engine twisting or the exhaust swinging?
With just a single brace I'm worried about the exhaust swinging. With the additional brace on the ppf I'd be worried about the ppf twisting.
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Old 12-11-2014, 05:00 PM   #27
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Ten bucks from my exhaust supplier, work fine for me?

Swinging exhaust is fine with a flex. No?
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Old 12-11-2014, 05:01 PM   #28
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Ten bucks from my exhaust supplier, work fine for me?

Swinging exhaust is fine with a flex. No?
Go out to your shop and try to bend a flex pipe with your hands and tell me it wont still transmit a good bit of force.
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Old 12-11-2014, 05:17 PM   #29
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A bracestrong enough is easy, u bolt exhaust clamp and 3x15mm mild steel flatbar mounted on a u bolt bolt and a lower gearbox bolt. It goes through a 90 degree rotation allowing a little expansion but eliminates most of the swinging force. Of course a flex pipe goes behind the brace.
Great minds Dann....

I use a similar clamp made from 5mm x 25mm bar attached to the bottom gear box bolt.
Some times I extend it and fit 2 clamps for track use cars. This type of bracket provides support and dampening but still allows for some movement so nothing gets sheared.

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Old 12-11-2014, 08:22 PM   #30
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I've also considered bottom bracing

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Originally Posted by Leafy View Post
There's an older thread on the subject where I had the idea to also hard mount the exhaust to the middle or back of the PPF to completely get rid of the effect and to more or less let the whole exhaust move with the engine but no one was buying it at the time. It pretty much operates under the assumption that without miss matched mount stiffnesses (IE engine and diff mounts are allow around the same amount of flex) that the PPF doesnt get twisted all that much while driving.
Interesting idea. More to the point, what about the mount FM uses for their exhaust systems, connecting the downpipe to the transmission?



I've been thinking of trying to come up with something similar for my ARTech stuff, but using one of the big wide band style clamps to spread out the load:



Bottom brace on the manifold/turbo does sound ideal. Plenty of bolt holes on the side of the engine block to accomplish this.

Edit: Yeah, what sturovo said
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Old 12-11-2014, 08:25 PM   #31
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Isn't the issue with any bottom brace that when the manifold expands the brace doesn't expand with it?
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Old 12-11-2014, 10:23 PM   #32
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Isn't the issue with any bottom brace that when the manifold expands the brace doesn't expand with it?
Which way does your manifold expand? I did temperature fea on my manifold to so I know mine basically tries to tuck the manifold in closer to the engine when it gets hot and twists is a little clockwise when looking at it straight down. So any mount with 2 rod ends on either end would give enough freedom for my setup.
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Old 12-11-2014, 11:03 PM   #33
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Originally Posted by EO2K View Post
...what about the mount FM uses for their exhaust systems, connecting the downpipe to the transmission?

I've been using the FM brace for several seasons. My downpipe originally had a flex joint in front of where the brace mounts which didn't make sense to me so I cut it out and sleeved in a thicker piece of aluminized exhaust pipe and put the flex joint behind the brace. There is an indent where the ubolt and bracket have squeezed that section over the years but it hasn't fatigued or failed. More importantly, my exhaust no longer uses my downpipe as a breaker bar to kill my DP and turbo fasteners.

Related to the original topic, the MSM turbo has a nicely designed brace integrated into the motor mount. It seems to provide excellent support although there is less inertia on the little OEM turbo on the factory log manifold than there is on a big turbo on a ram horn tubular.
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