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Triple Blowthrough Turbo


Dat73z

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FYI, VR38 downpipe studs are M8x1.25 on nut side and torque spec is 25.5ft-lbs so don't over think it.  If you're having issues sealing then it is likely due to the mating surfaces not being completely flat and that gasket, which appears to be just a flat piece of metal with no raised sealing area.  VR38 gaskets are thicker with a raised edge around the sealing surface to create the seal.  If you have future issues you might consider the remflex carbon gasket (18-005) as they conform the surface due to their ability to be compressed. 

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@240zturbo in the video I posted earlier, I'm fairly certain all of the studs had stretched. I think the root cause was spiking egts when I was throwing fire out the exhaust with retarded timing when the crank pulley was walking off, but also I am running inconel shielding all around which traps the heat into the hot side. 

 

The gasket is actually a stamped SS piece with a raised lip, but it's only good for one use (attached a pic of the new gasket I have).

 

I agree simpler is better, but I also didn't want to order the same hardware to slam it together and have the same issues down the line which is why I'm now at resbond, inconel studs, and stage 8 hardware. 

 

Edit: also for reference after going through all this and doing the research, the next iteration of this build with the next turbo will be all vbands and no gaskets including the manifold. No gaskets, studs, or hardware to fail. 

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Edited by Dat73z
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That gasket looks good so you should be fine assuming the down pipe flange is flat.  You can always run it on a belt sander and you will quickly discover if the surface has high spots.  Now that you have the inconel hardware just get some good prevailing torque nuts and tighten to 25.5 ft-lbs and you're golden.  If your threads on the nut side are M8x1.25 then the prevailing torque nuts from Nissan for the GTR downpipes are an option.

 

If you're going to do a manifold from scratch then I would highly recommend that you go twinscroll as opposed to open scroll and vband.  Also, I never have issues with the 4 bolt flange leaking on any of the iterations of turbo's I've run on the EVO.  TwinScroll will give you significantly better spool and allow you to run a larger turbine, which reduces drive pressure.  The lower driver pressure makes the car way less knock prone on 93 pump allowing you to run more timing or more boost or both.  You'll want to keep the runners small using 1.25" schedule 10 pipe, which is good for applications up to about ~1100hp.  The smaller runners will keep the port velocity higher and allow for quicker response and will not affect hp vs a 1.5" schedule 10 pipe.

 

I'm a big fan of the S362 SXE (6268) and based on my testing in comparison to the Gen1 GTX3582r (6262), I lost no spool and picked up 50hp@wheels (~600whp vs ~550whp) on 93 pump.

 

 

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My sincerest apologies as it looks like I gave you inaccurate information.  I pulled one of my old downpipe studs from a box to measure the turbine side threads and they were M10x1.5 so I struggled to understand how I thought the studs were M8.  Turns out the tap I used to measure the nut side threads was an M8x1.25 tap, but I didn't see that is was one of my heli-coil taps.  To make it worse, I was reading the Nm column instead of ft-lbs for the torque spec, but luckily that was the correct spec in ft-lbs for M8 assuming you have the highest grade stud.

 

The correct information is as follows for M10 GTR down pipe studs

Turbine side is M10x1.5 torqued to 19ft-lbs

Nut side is M10x1.25 torqued to 36ft-lbs

 

Attached is Nissan's torque table for various size bolts depending on Grade.

 

 

GeneralTorqueSpecs.jpg

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Thanks @240zturbo. Lots of great information, just haven't had time to process it this week. It seems the dry trq spec for m8x1.25 in your table is 21ftlbs which is what I expected. I posted the torque values I intend to use but wet with Resbond in a prior post, which are close enough to your table I think. 

 

Anyways now that it's Friday I'm starting back in on the build. Fortunately my resbond showed up so tonight I'll start back in on this turbine work. 

 

Unfortunately a supplier who was supposed to ship me an OE Nissan part sent me one of those aftermarket deals in a ziplock bag. So more parts delays again and changing of suppliers. Every time this happens, I feel like a week is lost in waiting, return shipping, etc. 

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Tonight I test fit the rest of the stage 8 and modified hardware to the inconel shielding. 

 

Things don't fit as well as they used to, mostly due to the hardware on the stage 8 being larger. Since the inconel shielding is just two layers of inconel with a ceramic layer sandwiched inbetween, I'll just bend the shielding a bit to hug nicer before the final safety wiring. 

 

Debatably, Ive read online that inconel shielding and turbo blankets trap heat in allowing turbo hardware to heat higher and longer than they would exposed to free air resulting in high temp creep for the hardware. But since I drive this car on the street I'm hoping to find a compromise since I've found through this build that carbs and ethanol fuel in bowls above the turbo really benefit from the shielding. If it was a pure track machine I'd lean towards no shielding around the hardware at all for reliability since the carb radiant heat issues start coming up in stop and go traffic only. 

 

Edit: Just to document this and perhaps only those that have run these setups know (which is the point of documenting this build thread since I've never seen this info out there...) but one thing I've found is when you're boosting, the atomization of the fuel and charge air cause the carbs to get ice cold to the touch. So even when you've parked and heat soaked to where the carbs have boiled over/fuel had completely evaporated and you will literally burn skin touching the carbs...after the first mile or so of boosting the carbs get ice cold and can have condensation building outside of them depending on ambient weather conditions. These are details I wanted to document here I've never found researching these setups. 

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Edited by Dat73z
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@240zturbo just to keep it simple and in one post, in my research there are ultimately 5 things seem to solve all turbo hardware failure issues: 

 

1. Upsizing hardware to M10

2. Inconel or high temp alloys

3. Some form of mechanical locking hardware

4. Do not overtorque materials to yield

5. Don't trap heat in

 

Edit: added 5 but again since this is a carb setup everything is conpromise

Edited by Dat73z
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