Fritz Flynn

iTrader: (263)

YEP

For a street car nothing beats the twins unless you want to completely rebuild your car around a fast spooling single. BUT get ready for exhaust leaks, fuel leaks, blown engines etc....

Bolt on a fresh set of twins with a good engine and supporting system and you should go sailing off for 50k miles with no issues.

I wonder how many single turbo cars make it even 10k

Tom93R1

iTrader: (2)

Getting water to the turbos could be a bitch depending on how the previous owner went single.

I do have to agree with some of the others here that it is going to be a lot of work for no benefit if making it non-seq. If you are going back to the twins, just go all the way and make it seq. The vast majority of the work and parts you will already have done anyway.

BLUE TII

iTrader: (9)

has anyone done a good job of converting from the vacuum system to an electronic one controlled by one of the current EMS's?

My view on this is electric solenoids don't have a good history of surviving in the engine bay of the 3rd gen, I couldn't imagine sticking them right on the turbos' Y-pipe.

I think the vacuum/boost actuators are much more simple, reliable, cheaper to replace on the y-pipe.

The '99-'02 Mazda approach was a good one IMO Simplified sequential operation with a "black box" vacuum/boost switching module.

One module, less vacuum lines, less wiring.

Basically, Mazda did fix most all of the problems with the FD during the 11 years of production.
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Regarding the original posters dilemma.

I would never want a non-sequential stock turbo FD. The boost response is much, much worse than a modern single turbo of the same power.

I have been through diagnosing and fixing sequential turbo problems and it is a complex system to learn and a pain to work on with the cramped conditions and solenoids under the upper intake manifold.

Once you learn how it works, you just have the pain of working on the cramped system.

Going back to sequential operation after the harness has been hacked is going to be a lot of work.

If I didn't have to pass a visual inspection I might go with a modern small single turbo instead like I did on my FC.

I used an EFR 7670 and it is by far the highest low rpm torque single that I have seen on a 13B. It does only get 5psi by 2,000rpm but it has full boost between 2,500 and 3,000rpm (depending on boost levels).

scotty305

iTrader: (2)

With some planning, it should be possible to get the OEM twins running in a simplified sequential setup. Below are some notes I took when I simplified the OEM setup, removing all the rat's nest hard lines and replacing them with a few vacuum lines and T's. I highly recommend using DaleClark's viton check valves, they are nice and compact.

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Did some more research on the OEM solenoid vacuum lines, ECU pins and control logic. I've always wondered why most (but not all) of the solenoids are OFF at low RPM and ON after the secondary transition. The only exception is the Charge Control solenoid, it is controlled exactly opposite of all the others... ON at low RPM and OFF after the secondary transition. It turns out the vacuum lines for the Charge Control solenoid are plumbed backwards compared to the other solenoids... see diagram below (solenoids_stock.jpg)

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I want the ECU to operate the Charge Control Solenoid the same way the others are activated, (off then on) this will allow me to experiment with controlling the sequential switchover point based on a combination of TPS, MAP, RPM or even VSS rather than simply RPM-based control. In order to do that, the vacuum and pressure lines going to the Charge Control solenoid will need to be swapped. The plan is to install the solenoids and vacuum lines as shown below (solenoids_modified_w_vacuum_routing.jpg), this should leave room to mount the Prespool and Wastegate solenoids on the bottom row of the solenoid rack (the top-feed fuel rail is going to prevent them from being installed in their original location).

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04G35S

iTrader: (10)

This seem like a nightmare to me. You have a single converted engine harness and now you want to go back to twins? You will need at the very least the vacuum manifold, solenoids, and a new engine harness... If the guy wants a responsive setup why not just go with a smaller single turbo since everything is already converted?!

greenday_5606

Thank you! This is actually pretty helpful.

As a response for everyone else, the owner wants a the car to be fairly stock. He doesn't want a single turbo, he wants the original twins. I know there is a lot of controversy, but I know when my car was running twins I loved it. Wiring really isn't that big of an issue for me because I have two or three harnesses laying around. I'm just trying to figure out the simplest way to run twins. Whenever I first bought my rx7 it was a "poor mans non sequential" and it was awful. Bolts and other various objects plugging vacuum lines, and mechanics wire everywhere. Not to mention the car kept falling in and out of limp mode due to the previous owner being a master mechanic and doing the wiring in the worst way possible.

greenday_5606

How is the response with a large street port and sequential twins? I know that is a vague question because there are so many variations on what is considered large, but I've never had a rx7 run twins with porting. Also another question I have is has anyone ever ran e85 on twins? Any benefits really? Do you think it would be possible to do this with 850 and 1650 injectors without maxing them out?