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Sneak Peek: Bothwell Motorsports Pro Mod Camaro

by Khiem Dinh

Khiem Dinh is an engineer for Honeywell Turbo Technologies at the time of this writing.  All statements and opinions expressed by Khiem Dinh are solely those of Khiem Dinh and not reflective of Honeywell Turbo Technologies.

Firstly, I need to thank my co-worker Krystyna Kubran for letting me borrow her phone to take pictures (the camera on my phone sucks); I wasn’t exactly expecting a 5-second drag car in the parking lot at work so I didn’t have my camera. Oh yeah, she can out-ride the vast majority of you on a motorcycle on a race track; her street bike and former race bike is an R1 while her new race bike is a ZX-10R. Check her out on BuzzFeed. Back to the twin-turbo, few thousand horsepower drag car.

 
This is the engine cover. The two holes in the top are for the intakes of the turbos.
Underneath the piping is a 526ci big block V8 which is fed methanol stored in the fuel cell at the front. The turbos are angled at a steep 37 degrees. This is typically not recommended as it can lead to uneven oiling of the bearings and also oil leakage out of the center housing past the wheels (like water spilling out of a tilted sauce pan). The twin Garrett GTX5518R turbos use ball bearings of course and the ball bearing requires less oil flow compared to journal bearing setups. Also, a journal bearing setup relies on a thrust bearing to handle the thrust loads and oil getting fed to the thrust bearing is critical to survival due to the required hydrodynamic film the oil creates. The thrust bearing is located on the compressor wheel side which is uphill for the oil to go with the way these turbos are oriented. No oil to the thrust bearing, no hydrodynamic film, bye bye journal bearing turbo. Ball bearings don’t depend on oil to support the thrust loads, so the turbos can survive the tilt. You can read more about bearings in our Turbo Tech: Turbo Bearings article. As for the oil leakage issue, more on that later. You’ll also notice no intercoolers are used; cooling the charge air coming out of the turbos is not required when running methanol for fuel. Remember back in the day, the CART IndyCars also ran methanol and did not use intercoolers on their turbo engines. Hey, those used Garrett turbos too. Anyway…
That is one pretty exhaust manifold! EGTs are monitored on each runner. Look closely, and it appears that stepped primaries are used. The engine revs up to 10,500rpm, so I’m guessing the stepped primaries are to tune for the high rpm range of operation.
The placement of the wastegate is ideal for the best boost control. Also notice the weight of the turbo is supported by a brace attached to the oil drain flange of the turbo; bracing the turbo keeps weight off the exhaust manifold to help prevent cracking of the manifold.
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Comments
Wrecked
Wreckedlink
Wednesday, March 25, 2015 5:33 AM
Thanks for the article.

On the second page in the second photo, what is the line connecting to the intercooler pipe? It almost looks like a meth injection line.

Also, the fuel pressure sensors. They look like they connect to the manifold. Is it possible that they are measuring differential pressure (fuel vs air).

Last question, whose ECU controls it all?
JR
JRlink
Wednesday, March 25, 2015 6:02 AM
Khiem,

Can a Garrett Journal Bearing be aloud to live at the 15 degree angle, or is it only Ball Bearing turbo's that can survive up to a 15 degree angle and a journal bearing must be mounted a zero degrees?
Fabrik8
Fabrik8link
Wednesday, March 25, 2015 5:10 PM
@wrecked:
I doubt that yellow line is a meth injection line, because of the placement. The piping goes uphill around a bend, around another mild bend, and then along a long horizontal section before making a 180 degree bend. That would be a crazy flow path to try to keep a fluid in suspension after injecting it. I suspect that it connects to the black pressure sensor on the cowl panel, right above the right side BOV (visible in last picture on page 2). That is probably the sensor used for boost control feedback, given the close proximity to the turbo outlet.

The fuel pressure sensor adapters look like they were designed to use the extra injector bosses like a dummy injector, so they likely seal to the intake manifold with an O-ring (like an injector) but simply plug the manifold hole instead being ported to intake manifold pressure. There aren't any screw-in sensors that I know of that have a split front-facing port that can sense two fluids at once.

The ECU is a BigStuff3, the yellow "3" on the logo is visible on the right side door tubes in the cockpit photo on the last page.
spdracerut
spdracerutlink
Wednesday, March 25, 2015 10:05 PM
JR, short answer is no. For one, you greatly increase the risk of leaking oil past the piston rings which will dump oil out into the compressor or turbine housing depending on which way you angle the turbo. Secondly, you could possibly starve whichever bearing(s) is/are uphill of oil which will grenade the turbo quickly. Journal or ball bearing, I'd avoid angling a turbo if at all possible. This particular setup is able to get away with it due to the ball bearing and dry sump system which sucks the oil out of the turbo.

Back in the day when Subaru was still in WRC, they did have a turbo they mounted vertically (compressor side up), but they had some special sealing design to prevent oil from leaking out the turbine side. They probably had a special oil path inside the center housing for the bearings too. And of course, those WRC engines were dry sumped, so highly likely the turbo oil drain was connected to the dry sump system.
Dan DeRosia
Dan DeRosialink
Thursday, March 26, 2015 3:34 AM
I'm curious about exactly how IHI did that sealing setup. Quite obviously there's a few ways, but there's not exactly a hell of a lot of room in a CHRA. And the Subarus were wet sump, for some reason. I've heard it said that WRC required wet sumps for cost savings, which makes *no* sense in the context of WRC of that time.

It's interesting that these guys are managing what looks like one injector per cylinder. I mean really, am I missing a second or third set around somewhere?
Marty Staggs
Marty Staggslink
Thursday, March 26, 2015 7:59 AM
Those are indeed two injectors per hole. They are two very different styles is all.
spdracerut
spdracerutlink
Thursday, March 26, 2015 8:02 AM
Wet sump on the old WRC Subie eh? Definitely odd considering the cost of every other part on the car.

Those are definitely pressure sensors, so they must be integrated with the fuel injector then. I stared at them for a long time and tried searching for such a setup, but I didn't find anything. I admit it wasn't a super thorough search :)
Fabrik8
Fabrik8link
Thursday, March 26, 2015 8:10 AM
So are those external injector solenoids instead of pressure sensors?
Marty Staggs
Marty Staggslink
Friday, March 27, 2015 7:57 AM
@spdracerut - trust me on this. They are NOT pressure sensors.
That is indeed the type of injector they are. It is a side mounted solenoid instead of a conventional internal design. This design allows for incredible volumes of fuel flow capacity.

Here is just one example -http://www.precisionturbo.net/air-fuel-delivery/fuel-injectors/details/Precision-Turbo-and-Engine-ProInjectors/537
Fabrik8
Fabrik8link
Friday, March 27, 2015 8:06 AM
Those are cool, I kind of figured they were something like that if they weren't pressure sensors. Never knew injectors like those existed. Those are 500 lb/hr injectors according to the labels in the pics on Precision's site. Wow.
spdracerut
spdracerutlink
Friday, March 27, 2015 8:18 AM
Marty, thanks for the info. Yeah, when I was researching stuff, all I came upon were pressure sensors that looked the same.
mike156
mike156link
Friday, April 03, 2015 9:31 PM
Do those types of injectors offer good control? Or are they more delivery the majority of the fuel as a switch then a standard injector is used for tweaking the fuel delivery in to where it needs to be?
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