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DBL_TKE Member
Joined: 28 Feb 2007 Posts: 1505 Location: Aloha, OR
1991 Chevrolet Camaro Z/28
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Posted: Thu Mar 06, 2014 8:29 am Post subject: Turbo questions |
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For the past couple of months I have been researching like crazy in order to do a proper turbo build, though some info is harder to come by than other stuff. I gave myself a crash course in learning how to read a compressor map last week. There's lot more to it than I originally thought and I still don't quite have it down, But my first question here is how do you properly determine what size wastegate and blow off valve to use? I get the general idea but is there an actual mathematical formula? _________________ Richmond 3.73 posi| 36/24 sway bars | SLP LM2 | Koni's | Ground Control 800/200 | Y2K wheels | Dyno Don headers & Y-pipe | airfoil | BBK underdrive pulleys | Raised strut mounts | Extended ball joints | LCARB'S
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Dewey316 The Lama
Joined: 08 Jan 2004 Posts: 7295 Location: Bringing the tech
1990 Chevrolet Camaro RS
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Posted: Thu Mar 06, 2014 10:26 am Post subject: |
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It depends a lot on the turbo/motor/power combo. Really, bigger turbo's you can usually deal with a smaller wastegate, since you won't need to bleed as much pressure most of the time. BOV on the otherhand, the more air you push, the bigger you need. This stuff seems to be a bit of a black-magic-art by the guys who do it, i would really just call and talk to a vendor who deals with big motors and turbos and see what they say.
With a big single like you're going to run, you might want to consider setting up the BOV as a recirc valve instead, that way you can still control pressure stalling the turbo, but you don't have to completely recharge the intake tract to get back in the power. |
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Dewey316 The Lama
Joined: 08 Jan 2004 Posts: 7295 Location: Bringing the tech
1990 Chevrolet Camaro RS
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Posted: Thu Mar 06, 2014 11:07 am Post subject: |
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I should also add a little more because it isn't as simple...
if you want really limit the boost on a big motor, with a quick spooling turbo, then you will need a large wastegate. For example, if you wanted to limit yourself to 6lbs of boost, you are going to need to pass a lot of exhaust through the wastegate. If your running 36psi, then you won't need to pass as much. That is what I mean by engine/turbo/power combo, its a matter of how much exhaust you end up actually passing through the wastegate. |
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aaron_sK Member
Joined: 23 Jan 2006 Posts: 8834 Location: Back in beautiful Tacompton
1987 Chevrolet Camaro IROC-Z
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Posted: Thu Mar 06, 2014 6:22 pm Post subject: |
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Dewey316 wrote: | i would really just call and talk to a vendor who deals with big motors and turbos and see what they say |
Some solid advice overall, but I have to disagree with Dewey about this specifically. In my experience vendors are idiots who will tell you all kinds of nonsense. Do not trust anything they say.
Instead, look for real-life results. There are thousands of guys running a gen3 Chevy with a turbo. Look at who is successful and figure out what their builds have in common. Be honest about what you want to use the car for and how much power you want to make.
The advice about WG vs. turbo size is dead-on. You will not need much of a gate with that thing, but compressor stall will be an issue.
Also bear in mind that quality is important. There are plenty of "big" WG's and BOV's that are poorly made crap. "It's not the size, mate" and soforth... |
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Dewey316 The Lama
Joined: 08 Jan 2004 Posts: 7295 Location: Bringing the tech
1990 Chevrolet Camaro RS
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Posted: Fri Mar 07, 2014 6:52 am Post subject: |
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aaron_sK wrote: | I have to disagree with Dewey about this specifically. In my experience vendors are idiots who will tell you all kinds of nonsense. Do not trust anything they say. |
Many are, but not all, some of them have built more turbo combo's that work, then anyone else you will talk to, its in picking the right guys.
Its information man, get it from the right sources, I didn't mean call Summit and ask for what WG they want to sell you. |
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Twilightoptics Hardcore (12sec Club)
Joined: 13 Jan 2004 Posts: 9191 Location: Auburn , WA
1987 Chevrolet Camaro IROC-Z
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Posted: Fri Mar 07, 2014 6:20 pm Post subject: |
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Pretty much what Dewey said. Personally when selecting a turbo itself, I find the power I want to make and the rpm and what boost level I want to make it at.
I have a sneaky suspicion you're not going to need much wastegate at all unless you're pushing extreme small block rpm. As far as the compressor map - do the math. What's your displacement/peak rpm/etc and plot it on the map of your turbo and see where things start to line up.
That turbo is bigger than what I work with all day on 7.6L Inline 6 at 2700rpm at 40psi. And the Diesel has more heat to add to the equation. _________________ A redline a day keeps the carbon away! |
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DBL_TKE Member
Joined: 28 Feb 2007 Posts: 1505 Location: Aloha, OR
1991 Chevrolet Camaro Z/28
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Posted: Sat Mar 08, 2014 12:32 pm Post subject: |
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I've been considering running twin 38mm wastegates because since the turbo is a twin scroll It'd be beneficial to keep the hot side divided as well. Seems like most people that run a single WG tend to be around 50mm. I'm intending to keep my max boost in the 16-18PSI range. |
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Dewey316 The Lama
Joined: 08 Jan 2004 Posts: 7295 Location: Bringing the tech
1990 Chevrolet Camaro RS
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Posted: Mon Mar 10, 2014 6:29 am Post subject: |
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With a twin scroll, if you really want to go dual WG if you can, controlling the flow and keeping the exhaust paths separate is ideal. You will need to be very careful to get them to balance correctly, but it shouldn't be too big of a deal.
I am pretty sure you would have more than enough WG with those, I think your on the right path, unless you bring the exhaust together, then split it again for the twin scroll mount, putting a WG on each of the exhaust banks will be your only option. If you do bring them together, you loose the real benefit of running a twin scroll. |
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DBL_TKE Member
Joined: 28 Feb 2007 Posts: 1505 Location: Aloha, OR
1991 Chevrolet Camaro Z/28
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Posted: Mon Mar 10, 2014 7:29 am Post subject: |
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Yeah. I've been reading up on the benefits of keeping the twin scroll separate. Though I did see a clever way of doing that and still running a single wastegate. They ran a short Y-pipe from the wastegate to each side. |
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Dewey316 The Lama
Joined: 08 Jan 2004 Posts: 7295 Location: Bringing the tech
1990 Chevrolet Camaro RS
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Posted: Mon Mar 10, 2014 7:34 am Post subject: |
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DBL_TKE wrote: | They ran a short Y-pipe from the wastegate to each side. |
That is all in the execution, you don't want to 'equalize' the pressure across the banks all the time (and remember, at full boost the WG will be cracked open, or fluttering between open/closed) and once the WG is open there is a path for the pressure waves to travel to try to equalize. You also want to locate the Y-Pipe somewhere where it will be able to also bleed enough pressure to control the turbo. |
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BigDaddyVu 12sec Club
Joined: 31 Jan 2004 Posts: 1118 Location: Spokane, Wa
1986 Chevrolet Camaro Z/28
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