greenday_5606

Hey guys,

A friend of mine just bought an rx7 and it came with a single turbo on it. He wants to go back to the stock twins because they came with the car as well. I am wondering what we need to have to put the stock twins on. We are wanting to do a simplified non-sequential setup if possible. Any help and info would be appreciated. The car has an after market injector setup and is running a pfc.

Thanks in advance.

Slow2k

iTrader: (9)

Stay single turbo. There is absolutely no reason to go back to the twins if you're going to do a non seq. set up. It's basically a laggy single set up with all the downfalls of the twins. Heat, space, etc.

ondabirdhouse

iTrader: (26)

I disagree, there are plenty of reasons to go back to twins. A somewhat stock setup will usually hold better value then a single turbo setup. Twins are anything but laggy, their instant power is what make the rx7 so much fun to drive.

Now..... I will say that if he is coming from a GOOD responsive single turbo setup like a GT35r, borgwarner, or A-500, etc. I wouldn't recommend going to stock. As those turbos are a great alternative to the twins and you would be back tracking in terms of power/mods goals (which I believe Slow2k was expressing)

I have thought about going back to twins myself, and if I did I would go BNR Stage 3 twins.

What is the current setup on the car now? that would help to give us a better idea/reasoning behind going back to twins??? ECU, Fuel system, turbo, intercooler, etc??????

jmadams74

Note he said going back to NON-sequential twins. Not sure that makes sense. I would imagine if you went back to BNR Stage 3 you would go sequential (this is what I have). Lots of low-end kick and good high-end power to 350 RWHP+.

cr-rex

iTrader: (114)

non-seq twins are basically the same as a single..... just in a different size. i would recommend going twins over single if you plan on using the car for some regular high speed action and are worried about replacing turbos. a set of twins can be had for almost free and swapping them isnt a that big of a job.

i would suggest staying single regardless.....

DaleClark

iTrader: (55)

IMHO the only reason to run the twins is for the sequential system and for the OEM-ness of the install. Non-sequential is a poor man's version of a single turbo - all the lag for a little more power.

That said, I would go back sequential if I was putting the twins back on. Good thing is you can probably sell the single turbo setup and make money on the process. Hard part is if the previous owner really gutted the system - cut up the wiring harness, removed the solenoid rack, etc. You'll have to track those pieces down. If you're brand new to RX-7's, putting that all together and having it work right is a scary process, there's a LOT to it. I could do it no problem, but I've been around it for ages .

For a job like that, I would probably just pull the motor, do all the work on an engine stand, and put it all back in. In the long run that would be SO much easier and give a better result, you won't be bending over a car and trying to reach bolts, you can sit on a stool right next to the engine and work on it.

Dale

greenday_5606

He's has already sold the single turbo setup. His fuel set up is 1680cc secondaries and 850 primaries. He has a god speed intercooler but I'm not sure on the sizing. I'm also not new to rx7s, but it has been forever since I have touched twins. The car has a modded wiring harness for a single turbo, so that's the big problem. I'm wondering what's the easiest way to get back to twins, as in minimum electronics/solenoids and minimum vacuum. Thanks for the help thus far guys.

greenday_5606

Oh it also has an after market boost controller and wideband.

7-XR

iTrader: (7)

If I were him, I would look for a running long block with wiring harness for the same year/model and swap the motors.

greenday_5606

Well the motor is ported and actually has 0 miles on it so we are avoiding that.

Slow2k

iTrader: (9)

Shoot Fritz Flynn a PM, im pretty sure he would have most of the parts you need and would have a decent idea what you would need.

lOOkatme

iTrader: (19)

Not to be blunt, but why would someone buy a single turbo car and want the stock twins?

I mean buy one with the stock twins. This sounds like a nightmare in the making.

greenday_5606

Why would it be a nightmare? This is an easy job persay, but it's not something most people do. Stock is something only some people desire. Not for me either.

Slow2k

iTrader: (9)

I dont feel like it's a bad idea going back to stock twins for sequential but I think it's absolutely pointless to go from single to non seq twins. It's like taking a step backwards. Even if replacement twins are cheap they are a complete pain in the ***. You can get borg warners real cheap, they're great turbos and most setups the turbo is easily accessible.

Montego

iTrader: (1)

From someone who has had a perfectly working sequential setup and before these cars got old: IMO The stock setup sucks *** compared to a well sorted out single.

I have done all three setups and came away with these notions:

Sequential
Pros - awesome response, the setup is so responsive that it will fool you into thinking the car is na.

Cons - 70+ vacuum hoses that at some point or another will crack and cause boost issues constantly, if replacing the vacuum line that is attached to a solenoid chances are that you will crack that nipple (solenoid replacement) upon removal, cracked housings (yep all of them), turbos are non rebuildable and get enough miles on the turbos and they will smoke.

Non-sequential
Pros - 99% of boost issues solved! Easier control to higher boost settings e.i. no wild boost transition etc.

Con's - all of the sequential problems minus the boost issues. Laggy... Not only does the boost threshold gets bumped back to around 3800rpm, there's a notable lag in boost response. What that means is that you won't see full boost until about 3800 rpms (instead of 2900) and it will also lag once you get there.

Single
Pros - none of the negatives of the stock twins with all of the pros of non-sequential. Plus: much cleaner engine bay ( less heat), depending on the set up it can be very responsive and with MORE power to boot, easier to work on.

Con's - costs money to convert, depending on your state: smog compliance.




So other than for smog purposes I can't fathom on why anyone would want to convert back to stock twins.

DaleClark

iTrader: (55)

I bought my FD with 68,000 miles in Oct '04, it now has about 126,000 miles on it.

Boost problems I've had? A slow turbo control solenoid. That's it.

In other words, a sequential setup can be dead reliable. Silicone vacuum hose on the hoses that routinely get disconnected (intake manifold) or are sketchy/loose. Leave the baked-on rat's nest hoses there unless the motor is out of the car and you're bored. Viton check valves. Done and done.

Going a little off topic here, so getting back on point.

So, how would I approach this?

- Good set of N3C1 twins, or if feeling baller, N3G1 '99 spec twins.
- JDM exhaust manifold with no EGR tube
- Oil and water lines for the twins, get new water hoses from Ray
- Rat's nest with solenoids, preferably low mileage
- Decent shape stock wiring harness, pull off the cracked tape and re-wrap/patch it up
- Ceramic coated downpipe

I would also go back to stock fuel rails and probably start with stock fuel injectors, or 550/1300cc injectors. 850 primaries are a pain in the ***, and that's WAY more fuel than the twins need.

I would try and find someone going single and buy the whole works for a package price. Or, buy a JDM engine. You can get a longblock with trans for $1800 - get that, cherry pick the good parts, sell the rest, and you could probably come out money ahead or break even.

Dale

lOOkatme

iTrader: (19)

Most people convert to single turbo and modify the car in a way it cannot be brought back to run the stock twins. like modifying the engine harness. then you have to find all the components to go back to run stock twins. I mean why go back to non-seq? this is such a horrible idea. There is no positives going back to non-seq. Most likely have a higher risk of buying used crappy components as well.

TomU

iTrader: (11)

Stock Rocks

Montego

iTrader: (1)

Food for thought: If the sequential setup is so reliable then why would anyone choose to go non-sequential?... Exactly.

Akagis_white_comet

iTrader: (4)

I'm gonna have to agree with Dale Clark on this one. A set of properly working twins with the correct supporting parts in the logical manner is the way to go. since the FD was introduced, we've had 20 years to observe its behavior, locate its flaws and implement corrections in materials and methods to make it work as Mazda intended to do from the start.

Silicone vacuum line is a must, although I would personally relocate the turbo control solenoids to a more survivable location as done on my 20B's twins. Another good idea would be to use one of AzEKnightz's solenoid racks, relocated in the same manner

Above all, if you're going to do this, go Simplified Sequential and replace all the vacuum lines all at once. Do it once, do it right and be done with it untill hell freezes over.

96fd3s

Because people are stupid.
We all know issues happen. But it can be reliable.
Its not bullet proof, and its definitely not idiot proof. What it is, is complicated to the majority of people who know nothing about it.

People go non-seq because they have issues with their seq system, take the easy way out, and convert it to non-seq. It could be 1 out of however many solenoids or hoses that is causing the issue, but many will rip the whole lot out rather than diagnosing the issue.
Its not the most reliable thing in the world, but people go non-seq because they don't have the nouse to fix issues properly.

Montego

iTrader: (1)

You two come talk to me after 15 years of ownership and have put on close to 120k miles.

Before you come back and try to teach me something please keep in mind that:

1) I have put on a **** load of miles on my fds
2) I live in southern ca where there is a plethora of rotary shops
3) have done the silicon vacuum thing
4) switched over from a perfectly working sequential to non-sequential to see what the big deal was
5) finally went single

I am not just talking about sequential vs non sequential, but about the whole system itself. I.e turbos, solenoids, housings ect.


Now in my experience if were to choose between between seq and non-seq I'd choose seq . But to say that seq is a problem free enviroment goes against not only what we have seen on the forum but also against common sense. Because it takes 72 hoses to work properly, and that those hoses sit in a very hot place, and on top of theres the aging factor.

96fd3s

I may not have had my car for 15 years, But I have had it about 7 years now, and have DDd it for most of the those years so I can comment. (I still DD it)

Not sure what having rotary shops close by has to do with anything.

Im from New Zealand, a dumping ground for Japanese cars. We have some of the best rotary shops (and cars) in the world and im sure we have many more rotary's running around then you do in your area. All the 4 rotor cranks etc come from NZ..
The redbull rx7 drift car is situated about 6 minutes down the road from me. There is an old 808 parked just on the road outside my work as I type this, there's my FD in the parking lot, and another FD a couple of numbers down the road.

EDIT; My comment was only related to the "then why do people go non-seq comment". They go non-seq because they cant fix their stuff, OR they have too many issues so cant be bothered fixing it anymore.
Im not arguing that its very reliable, only arguing the reasoning for going non-seq
cheers

Montego

iTrader: (1)

So you didn't understand the comment but yet decided to metaphorically 'whip it out and engage in a biggest dick contest'...

Here let me explain the comment: living in southern California (opposed to a place like Montana) lends itself to quite a few rotary shops which means more people having first hand experience and an overall broad rotary knowledge. And therefore the wheel isn't being reinvented each and every time the car goes to the shop. That's it just that you expect people to be familiar with these cars. Not that people know more than where you live nor that this is the mecca for rx-7s.



WTF bro? Then your whole input is kinda on the pointless side if you choose to ignore why the comment was made in the first place. The ROOT CAUSE (key word root cause) of why many people choose to go non sequential is because their sequential system failed them (reliability). People not being able to fix it is the secondary the reason because first the system had to break. Very simple logic

Jason94R2

iTrader: (3)

Seems like most sequential problems arise because people wait for them to break. Its not rocket science to to some preventive upkeep on a know to be troublesome system. When i bought my i had everything replaced and added the upgraded control solenoids for the twins. Everything worked fine for almost 20 years, now its all new again with better components, i have little concerns with the reliability of the twins control system.

That said, i would never own a twin car w/o them being sequential. If i had to go back from a hacked car to sequentials I'd probably look elsewhere like TS's IWG EFR setup since that seems as close to the twins respone wise as you'll get(love to see how it drives with light/part throttle where the stock twins are very lively) and wont have the headache of undoing what someone else has already potentially hacked up.

Jason