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Single turbo question

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Old 09-16-18, 02:00 AM
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Single turbo question

I often hear people switch to single turbo for reliability reasons. Is there any truth to that? If so what makes it more reliable, assuming its more then just half the turbos half the problems.
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Old 09-16-18, 02:22 AM
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Welcome to the board.

I'm not really a Gen 3 guy, but I'll take crack at it. I think the "truth" is it's a matter of perspective. The twins have a complex array of vacuum lines and solenoids from the factory that can make for time-consuming and difficult troubleshooting. Converting to single will eliminate that hassle (for lack of a better word). So I don't think they are necessarily less reliable so much as they require more maintenance, and a more complex knowledge base to keep them happy. Not every Gen 3 owner (or the person they bring their car to) has that knowledge base. I suspect those are the ones that may say they convert for more reliability. Likewise, I suspect the ones that have the knowledge, and more particularly the ones that are happy with the twins, would probably not share that perspective. Now, again, I'm not a Gen 3 guy, so I may be way off the mark.

Hopefully SgtBlue will see this and share his thoughts on it.
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Old 09-16-18, 02:39 AM
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Thanks for the response diabolical1,
Makes sense what you've said, and i guess this can really apply to anything twin turbos like 2j's/rb's etc. And like most things knowledge is king and knowing how to care properly for the twins and proper maintenance most parts can be reliable.
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Old 09-16-18, 06:58 AM
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Wikipedia has some informative articles on Wankel, NSU, Mazda, and the RX-7/8. Of course they are very introductory, but the RX-7/8 article in particular covers the life-timeline, and I recall has an overview of the 'two-turbo' version.
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Old 09-16-18, 10:51 AM
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I think this thread has the diagram for the stock vacuum system, and a simplified vacuum system using a single turbo (and a few variations in between)
https://www.rx7club.com/3rd-generati...-turbo-749702/

At a high level, you can eliminate a majority of the stock vacuum lines, solenoids, valves, etc when going single. Less moving parts in theory should mean less problems/surprises. Especially considering most all of these parts/lines live between the engine and the intake manifold, which is basically an oven.

If you're chasing power, I believe a single setup has lots of advantages there as well (turbos in general are a lot better than they were in 1993).

All of that said, Its a personal choice and I would never move away from using the twin setup on my car. I can certainly understand the appeal though.
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Old 09-16-18, 02:11 PM
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I don't disagree with anything diabolical said. While I'm a "3rd Gen. guy", I'm also still rocking the twins...so I don't have any real experience with singles and this is FWIW...
In addition to simplification... which believe me I get jealous of, the singles almost always carry with them more potential power. I'm making maybe 300 at the wheels on my car at just a bit over stock boost levels (10 psi). That's close to 100 whp more than when it rolled off assembly. Fast car, a lot of fun but there are a lot of cars faster. Still, I'm old and given my use of the car I'm content. Twins really start working hard past about 12 psi and start making a lot of heat. The higher you push them the shorter their lifespans tend to be. 25 years ago the sequential twins were the way to get low-end/low rpm power without turbo lag and continue to maintain that power. Pretty high-tech stuff for the day...not so much anymore. Turbo technology has come along way since then. Instead of the OEM journal bearing turbos, modern ball-bearing turbos will spool up very quick and still breath well. And they move a lot more air at a given psi than the OEM's without the strain. All that is a pretty compelling case for going single...until you factor in the cost. Buying the turbo, manifold, oil lines etc., relocating things, serious upgrading of the fuel system, intercooler and engine management, along with professional tuning. It gets expensive quick. And I'm not sure how it works in a state with emissions testing.

Last edited by Sgtblue; 09-16-18 at 02:23 PM.
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Old 09-16-18, 02:31 PM
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thanks everyone, got some great info here appreciate it.
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Old 09-16-18, 02:52 PM
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NH

Originally Posted by slblay83 View Post
Wikipedia has some informative articles on Wankel, NSU, Mazda, and the RX-7/8. Of course they are very introductory, but the RX-7/8 article in particular covers the life-timeline, and I recall has an overview of the 'two-turbo' version.
I've recommended this book several times over the years. I think it's a great primer for the new(er) owner of a rotary. And since I understood it (still pull it out occasionally), you can be confident a big-brain isn't needed...
https://www.amazon.com/Street-Rotary-HP1549-Horsepower-Reliability/dp/1557885494 https://www.amazon.com/Street-Rotary-HP1549-Horsepower-Reliability/dp/1557885494




Last edited by Sgtblue; 09-17-18 at 05:51 AM.
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Old 09-16-18, 05:28 PM
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Diabolical really summed it up. The sequential turbo lines and solenoids are all located underneath the upper intake manifold where it tends to get pretty warm. The lines deteriorate over time and give a plethora of issues with the turbos switching over at the correct times. Switching to a single turbo really removes the need for the rats nest of vacuum hoses because there's no need to switch anything over anymore. You can make decent power on the stock sequentials, as I'm running just under 290hp on the stock twins, upgraded fuel pump, apexi power FC and a proper tune on my 92 FD.
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