Twin Scroll Turbo

[Geoff]

For all you machinist out there or you just appreciate shiney metal.
This is the company who made the tap we used for the O2 bungs. He also got great tech support from the actual tool engineer. Threading stainless is a bitch. If it gets upset, it work hardens and gives you the finger.
https://www.youtube.com/watch?v=WaX8VIBeCkY
On the super slow mo of the tap busting, my buddy and I thought some six million dollar man sound effects would be a nice edit.

With a sound bite saying, "We have the technology, we can rebuild it!"? May not be worth rebuilding that busted tap

A novel way to thread a hole.
https://www.youtube.com/watch?v=SkPdgrjUEhY

I just sent that video around to a few folks I work with. We had Protolabs doing a quick turn prototype for us recently. The part had a blind tapped hole with a relatively thin wall at the base and we wanted to make sure they used blind hole tap and not something with a nice pointy tip (would have poked through the thin wall at the end of the tapped hole). "Oh, we don't use taps" was their response. Nice to see it in action.

[squaab99t]

Mockup of the wideband O2 sensors. Water plumbing PEX and some hot melt glue. Checking for clearances and placement so it does not too whacked out.

[squaab99t]

For the AEM electronics wideband AFR per cylinder to work properly with a force induction engine a pressure sensor is needed pre-turbo. The twin scroll added some complexity because you want to take the pressure across all four and get an combined average. I contacted AEM, and for a twin scroll they suggested two ports, and bring to a Y to feed a single pressure sensor.
I found -4 AN ports in stainless. Had to do some modification to suit my needs. The base was too beefy for the tubing, so I cut and ground it down to a reasonable thickness. Then I cupped the base to fit the dia of the tubing. I used a vise, a block to set the width , and two hammers. I did wrap the threads on the fitting to prevent damage and it also kept the fitting centered in the vise jaws.

Prefit on some tubing I used for some practice runs. I used a portaband to cut the base down. This left a nice disk to practice forming a run a fillet bead on some tubing. The practice piece is on the far end of the tubing.

Drilled holes in the wastegate tube branches, as these will have the pressure from a pair of cylinders.
I used a 1/8" filler rod to center the fitting over the hole. I originally used a straight rod, but it fell in, as there are holes in the tubing to let the gases in. A quick little J bend fixed that, and no more fishing or having to disassemble my back purge caps .

Fully welded. I'll cap the fittings with B-nuts (caps) when the pressure sensor is not in place.

[squaab99t]

Final stages of the fab. Once all the welding is done, Kevin and I are dropping off our truck load or stainless to the finisher for a high temp coating.

A bit unnerving drilling a 7/8" hole into a 1-5/8" OD tube. Mind the backside of the tube or your step drill will make one large hole and a smaller one.

Dry fit, and I radius the base of the bung to conform to the shape of the inner tube diameter.

Placed a single tack on each bung at the tangent. This allowed me to do some minor angle alignment to match their adjacent bung.

Removed from the head jig and welded individually. All back purged. Not a time to cheat and dork it up now.

Typical bung.

The snake orgy.

[beckmannag]

Looking good.

The snake orgy.

http://www.youtube.com/watch?v=aHzZRUikvaw

[Mezzanine]

Dennis knows how to treat a bung.

[squaab99t]

Dennis knows how to treat a bung.

You must respect the bung...
Couple more to do. A pyrometer port on the merge collector and a second O2 on the downpipe.

[squaab99t]

The welding is finally done.
Pyrometer ports pre and post turbo. It will be interesting to see the delta T across the turbo.

Second O2 bung further downstream of the turbo for sensor longevity. 36" recommendation from Bosch via AEM electronics correspondence. This ends up just past the downpipe hanger that cantilevers off the gearbox.

Almost 12 months to the day on this project. It has been a heck of a ride. Learned plenty, successes and failures were all in the mix. I'm sure there will be more as we do some testing and run it thru it paces.
It all started and with an idea, some paper, and it grew from there.

Happy New Year

[Nate]

I was going to ask if you were going to run pyrometer(s) but you beat me to it.

I was wondering if you were going to run individual pyrometers for each cylinder or just one in the collector. It would be interesting to see the differences between the cylinders but I suppose you could infer the same sort of thing from the oxygen sensors which are more useful for tuning anyways.

If you haven't purchased a thermocouple yet, I would check out the sensor connection, http://thesensorconnection.com/

I purchased one from them and it seems to be top notch quality.

[squaab99t]

Thanks for the input. Thermocoupes on each primary is the standard to infer individual AFR. It would increase in temperature if it went more lean than the rest, but you did not know how much. Now if you retard the ignition timing, the temp would also go up as un-burnt fuel continued to burn in the tube itself.
Individual AFR addressed these issues and gave real time data for each cylinder. Now, individual pyrometers work great for engine start up, as it tells straight away if the fuel injector is not firing or the spark is not happening. The rest will warm up and the bad cylinder will remain cold.

Thanks for the link. I'm thinking about replacing my existing probe with something of more quality as the probe will be pre turbo and I worry about the tip eroding and flowing into the turbine and housing. The link you provided advertise inconel sheath probes. That is the good stuff to hold up to the high temperatures.

Yesterday Kevin, Mezzanine, and I paid the high temperate coating finisher a visit. After seeing the colors in person, checking out their operation, and talking to the person who will be doing the work we wrote up the work order.
BMW Motorcycle primaries, hot out of the oven.

Color choice Satin Ti compared to the idled cycled natural stainless

Kevin's X pipe and mufflers

V8 pipe set. We number punched each flange while we were there with its respective number for easier locating.

Mezzanine checking out the goods.

Going over the details of what is to be masked. I brought my original downpipe (foreground) to be refinished. I welded in the wastegate bellow after the original design developed a crack. They did the silver some 10 years ago. It will be up for sale with the TiAl wastegate when refinishing is complete.

[squaab99t]

Found a picture of what we had for instrumentation when we had the big block on the engine Dyno. If you look at each primary you will see the wideband afr sensor and a pyrometer. These were made just for the Dyno as they do not fit in the car. The final config will only have the afr sensor bungs.

[squaab99t]

Tidying up some items while I wait for the headers to come back.
A while back I put a connector in for the COP for the wasted spark setup. To properly support the connector and wire bundle I decided to build a support bracket. A bit on the over engineered side, but I guess some may say that is the theme of this project.

I have a zip tie on there for the fit check. After I add some finish I plan on a glue lined shrink tubing section in lieu of the zip tie. Should look nice and tight.

[squaab99t]

Received the parts back from the finisher. Satisfied with the color and texture. Applied by the pros so no drips, runs or fish eyes.
The coating was applied both outside and inside the tubes to keep the heat inside to protect the engine bay and feed the turbo energy.

The paint does high light any cosmetic flaws in the welding.

[squaab99t]

Tried my hand at some stills and video. Not bad on the stills. The video is going to take some good editing or a re-do.

[squaab99t]

Reassembly in the car. A little nervous since the part was sandblasted prior to the finish. If you get too crazy with the media blast the part can warp and/or stress relieve and go places where it won't fit back up.

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Looking in good shape. Had to use the Swedish wrench some to sweet talk the merge collector on fully.

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Turbo V-band fittings line up in the original location.

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Next task is the downpipe and wastegate fitup. Tomorrow during the playoffs since Seattle Seahawks are out.