posted on March 18, 2013 00:00
|We’re excited to share with you our turbo, exhaust manifold, intake manifold and wastegates selections!
Project Toyota Supra MKIV, Part 4: Turbo components
Let's flow some air!
by Pablo Mazlumian
If you missed Part 3, we discussed getting the most out of our cylinder head for maximum airflow. This time we talk about airflow components that are on both sides of that equation.
Some of the more exciting products to talk about in a turbocharged project are the turbo components themselves. Precision Turbo and Engine is our selected brand for this project’s turbocharger and waste gates, having run a Precision 71GTQ and 71GTS successfully prior to this. Our choices for both the intake and exhaust manifolds went to Hypertune and Powerhouse Racing, respectively. The latter two took a couple of months to actually arrive, but the wait was well worth it. Not only will our engine bay look incredible, the engine’s airflow will surely be maximized to compliment our trick cylinder head work by FRP Engineering featured in last time.
Before any turbo project is started, one must decide the application and power level desired. Since our goal was a street 800whp, Precision thought either their best-selling 6466 or 6766 setups would work well for our application. Since I’m also a fan of less heat and pressure, I went for the latter, should we also decide to go badder. The 6766 will give us the greatest power room to play with.
|When building a turbocharged project, one must first figure out what the application is for, and how much power will be desired. For this 800 whp street car, our decision led us to the 6766 dual ball bearing turbocharger from Precision Turbo and Engine.
|We’ll be discussing our incredible eye-candy-of-a-manifold from Hypertune , which includes a 90-mm throttle body, throttle linkage, fuel rail and installation hardware. It hails to us from the land down under but can be ordered Stateside through Titan Motorsports.
|And more eye candy--we’ll be showing you the details of this incredibly difficult-to-make exhaust manifold from the Supra gurus of Powerhouse Racing in Texas, which is also a distributor for Precision turbo components.
|Our Precision 6766 dual ball bearing turbocharger. The ported "H” anti-surge allows us to use a 4-in intake tube. The 67-mm compressor wheel is machined from a 2618 forging and features PT’s exclusive CEA (Competition Engineered Aerodynamics) technology. Thanks to the latter, these newer wheels supply a higher efficiency and faster transient response for maximum power and performance. For a 67-mm medium frame turbo, it’s crazy to think it’s rated to 935hp. In fact, online you can already see guys hitting 800whp with a Precision 62-mm! 10 years ago I would have needed a 72-mm turbo for that.
Monday, March 18, 2013 7:28 AM
Whilst the larger Throttle Body is 38% bigger, the true story is its 90% larger in surface area.....and thus airflow.
Monday, March 18, 2013 7:58 AM
Can someone explain the advantage of a divided exhaust housing? Or link to something that explains it? I would like to learn more about that. Great write-up, keep it coming.
Monday, March 18, 2013 9:04 AM
you're absolutely correct, that was a last minute addition. It's 38% "larger in diameter" but the area is 5.14in2 vs 9.92in2, or a 93% "flow improvement". Thanks, and I'll add that to caption now.
while I know it's a flow thing to aid spool-up, others have more expertise to answer this better than I, so I've deferred by asking our Supra's engine builder, Jeff Gerner of FRP and this was his comment (oh, the things we do for our readers, ;) :
"in layman's terms, on a 6 cylinder, where the exhaust pulses compliment each other more than on a 4 cylinder (whose pulses are farther apart), the divided housing keeps the pulses that compliment each other in a separate half of the housing from the other pulses so that they don't fight each other. Thus, you smoothen flow by grouping together the complimentary exhaust pulses."
That said, you'll want to have a 'divided' turbo on an exhaust manifold that also has the twin scroll ('divided') exhaust manifold flange to benefit from what Jeff said.
Also, I will say that you can't really compare a .96 AR 'open' with a .96 AR 'divided' housing in terms of flow (the open will outflow it), which is why we went with a 1.15 'divided'--in hopes of being close to the flow of a .96 'open' AR, but also hopefully better spool. Only time will show how this setup worked for us, :).
Monday, March 18, 2013 9:32 AM
Joel, this is a pretty decent explanation.
On top of that, you can add a "quick spool valve" in between the manifold and exhaust housing. This will block off one of the exhaust wheels from flow until a certain boost level is achieved. This causes all of the exhaust to flow over one smaller wheel (thus more force) causing faster spool up of the turbo.
Sound Performance's page on their QSV
Monday, March 18, 2013 9:57 AM
Time for a MotoIQ article on divided housings and pulse conversion.
Monday, March 18, 2013 1:14 PM
"Thumbs up" :)
Monday, March 18, 2013 2:38 PM
will you be using a quick spool valve?
Monday, March 18, 2013 2:41 PM
So, how much of a PITA is it to access the fasters on the bottom/back half of the manifold? ;-p
Monday, March 18, 2013 2:54 PM
Indeed. if we haven't done a test on that yet, I'm game.
on the factory one? if I recall, a pain. It's been a while since I've removed it myself. I thing the HT one will go on as one piece and not be a problem (I hope--we'll see this within the next couple of weeks).
@warmmilk: I decided that I'd test the car without a QSV in hopes that, with these featured parts, I would not be needing one for my application. I think/hope the spool up will be enough so that any more will only give me more midrange wheel spin--especially running an E85 tune. But, we shall see how it all turns out shortly.
My wife and I also have a Renntech M-B V12 TT S600 with 520+whp and 700 lb-ft of torque (it's the baby hauler-actually sold it and delivering it wednesday...sad times), and that sucker spools up so quick that I almost wish I could have more lag. Too much wheel spin.
Monday, March 18, 2013 2:58 PM
@ Pablo: I was referring to the Powerhouse manifold.
Monday, March 18, 2013 3:02 PM
@Rockwood: Ah, in that case I think we should be ok, considering the longblock is going on with the manifold already on it. Should know in a few days..
Monday, March 18, 2013 7:09 PM
How does the SQV work in this instance where there is the divided manifold, and divided turbine housing? The SQVs I have seen use a non divided manifold, and the valve simply blocks off one of the two entries to the turbine housing. Such a setup aids with spool, but looses all the advantages of split exhaust. Is there a SQV that in one position combines both flows into one of the turbine housing inputs, and in the other position, keeps the two exhaust flows separate?
Monday, March 18, 2013 7:10 PM
SQV = QSV :-/
Monday, March 18, 2013 9:50 PM
'super quick valve'? ;)
yes I'd forgotten that you'd need an open manifold otherwise you'd essentially block 3 cylinders from running.
Tuesday, March 19, 2013 1:05 PM
Have you tested the Synapse wastegate yet? I am using it on my project and it is quite an impressive product with its 12 settings of boost from the box and quick responding valve
Wednesday, March 20, 2013 6:21 PM
Wouldn't it be better for the exhaust manifold to have equal length tubes for power? and some lacunar spaces in the attachment plate to the head for heat expansion ?
Tuesday, March 26, 2013 8:58 PM
@Dochka, on the equal-length, probably. But I know one fabricator that made an equal-length turbo manifold for an E36 M3, and said he'll never do it again without charging $5k, if that helps. Unfortunately, having all 6 of those pipes collect equally into one flange isn't as simple as it may sound. For a four-banger it's different.
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