Single or twin turbos?
 

Ladies and gents,

I'm buying an 93 FD that needs to have the turbos redone. So I was thinking of just going with the twins from BNR, but my mechanic is telling me to go ahead and do the conversion to single. He can get me a borgwarner single turbo for a pretty good price but I don't know if they are any good. Does anyone know how good those borgwarner turbos are? And is it good to just make the conversion since I need to redo them? Any help would be appreciate it!

What your mechanic is not telling you is that you will need to control that Turbo with an Aftermarket ECU and fuel,etc..so really just slapping on a single is not just a simple thing.

Oh the car already has that.. It is ready for a single.. Only thing it needs is the actual single, manifold and pipes.

So are those good single turbos or better stick with the BNRs?

My turbo is a based off of a T6 S400, and when it was a base 75mm unit it was a great and reliable turbo. Now since the day I've upgraded it (larger compressor side and race cover) I love it 10x more!
Best bang for the buck turbo out there IMO.

How much money do you have?

What are your power goals?

What is your primary use for the car? Track? Daily driver? Drag? Autox? A combo?

Mechanical ability?

Here is the deal gents. The car is just my toy so I'm going drive it about 2-4 times a week. Im switching from motorcycles to cars. I'm not mechanically inclined at all so I can't do it myself. I know it's pathetic, but I'm working on it! The car that I'm getting needs the trany redone and the stock turbos are fine but need to be redone or changed or something in the near future. Since the car is close to a good rotary mechanic which is about 9 hours from me, I was going to just go ahead and get those 2 things done and I have about $3300. I was planning on just getting the bnrs and the fuel system, but he said since the car is basically ready then I could do the single and trany for about 3500. The single turbo he says is a borgwarner but I don't know if those are good.

^This. Just saying you're going to single turbo isn't enough. Which one? And saying your getting a borg Warner is like saying you're getting a Chevy. Which one? Does it fit your use of the car and your goals?

I am curious myself, what are the main difference between a single and twin turbo?

I currently have twin turbo and I must say I like fact it can boost twice? That 2nd gear low boost is really fun.

with sequential twins, one turbo spools at the bottom half of the rpms while its twin spools at the upper portion, think of it almost primary and secondary fuel injection, also with a single its only that turbo spooling from xxxx rpms - xxxx rpms

I think you'll have a hard time doing a proper single turbo conversion for $3500 if you are having someone else do the work. Reason being is that most of the single turbo bolt on kits are $4000. If you have to pick and choose your parts to get everything you need, there's going to be a lot of fitting and modifying.

A very quick breakdown:

-turbo...$1500 (sounds like you already have one)
-manifold....$1000 at least
-wastegate....$500
-downpipe fabrication....$500 (or more)
-intercooler piping...$400 (you DO already have an upgraded front mount, right? If not, add that to the bill....$1000)
-misc plumbing, fittings, gaskets, etc....$400

Then of course the car needs to be retuned.

At least with the BNR turbos they bolt right on. The car will still need to be retuned, and the stock intercooler is not enough.

No, what is pathetic is when people act like they are God's gift to automotive tuning, when in fact they don't know much of anything.

It is a good brand, but as mentioned earlier, you would need to state the exact model if you want forum members to comment on it. Additionally, you will need to state following about the engine in order for people to know if the turbo is a good match:
- Type of porting, if any
- High-rpm modifications, if any
- Type of seals, if not OEM
- Doweling, if any
- What kind of aftermarket ECU is installed on the car?

Is he on this forum?

Is he going to include ECU tuning for that price? Is he bonded and insured in case he blows up your engine or accidentally causes other damage to your car? Mechanics are not necessarily engine tuners, and even with the BNR turbos the ECU is going to need a retune.

He mentioned that he could get me the turbo for $730 which is his price ( he has a racing team so he gets a lot of them I'm guessing ) the manifold he said $500 and the rest if the stuff he said I would be around $3500 total with his discount to buying parts. He's the mechanic from the previous owner and for the people I've talked to that he's done work for he gives people his price on things to get the work.

I'm going to have to get the specs of the turbo from him and will post it up here.
This is the car I'm getting and the specs of what he's done to the car.
https://www.rx7club.com/3rd-generation-rx-7-1993-2002-vehicles-107/1993-black-new-paint-engine-interior-c-tons-quality-parts-1014233/
Maybe that gives you a better idea of what the car has and what it needs.
Thank you for the help.

The same mechanic that rebuilt the engine would be doing the turbos and he said he is insured.

I'm going to have to agree with Aaron Cake on this one. While a single turbo conversion could conceivably be done on a budget of $3500, I see quite a few ways in which the financial limitation could create larger problems.

Even though I am running the factory JC Cosmo twins on my Project OldTree 20B-REW FC, I have to give credit where it's due on the simplicity and straightforwardness of a single turbo. There are just far fewer items that can break. Instead of six solenoids controlling the twin turbos (Pre-Control, Wastegate, Turbo Control-Vac, Turbo Control-Boost, Charge Control & Charge Relief), only one is needed for a single turbo (wastegate). To Mazda's credit, the changeover system works quite well when it is in proper order. However, baking the turbo control solenoids under the UIM has shown to consistently make headaches for FD owners due to heat failures. On the plus side, solutions are available for using better solenoids and relocating them so they endure better. My car is using 3-port GM truck solenoids mounted on the fender along with an impressive vacuum line routing system to turn the mess of vacuum lines into something a regular person can follow from beginning to end on every single line.

If you're serious about this project, I would invite you to step into the 3rd Generation and Single Turbo sections, read their FAQs and then reassess the goals, parts, tools, and means you have to work with. BNR twins are proven to work well and be a nearly bolt-on affair while delivering upwards of 400hp depending on what stage you get. Given your experience, a set of BNR twins would be a far simpler and straightforward option as far as the nuts and bolts go. As for tuning, this is a question best found in the 3rd Gen section or forwarded to BNR Supercars directly.

With either path, you'll still need to upgrade your cooling systems to balance the equation out. A good aftermarket radiator such as a Koyo one, along with a larger intercooler should be on your shopping list from the very start as these are reliability items.

One other thing to keep in mind is that you can almost always find good deals in our Classifieds section if you look carefully. When I needed to replace the damaged Charge Relief Valve on my 20B due to its vacuum nipple being broken off, I couldn't find one as it is a Japanese Market part. On a hunch, I went into the classified and snagged two FD CRVs and two stock BOVs, essentially four identical parts for $15 shipped. Put them side by side with the Cosmo parts and found them to be identical with exception to their mounting (FD is hose barb, Cosmo is flange on one side). Disassembled one FD part, transferred the internals into the Cosmo CRV shell along with an undamaged cap from the donor FD part and sealed it back up with some JB Weld so it's good as new. Best of all, I've got 3 more in case the CRV or BOV need rebuilt again.

Just remember, Search is your Friend :nod:

It doesn't look like it needs much of anything to me. Well, I would put on better coilovers, but the drivetrain sounds like it is just fine as-is once the transmission is fixed. However, I am a 2Gen RX-7 guy, so hopefully a 3Gen RX-7 guy can chime in with a better assessment.

When people ask about your setup, here are the important things (internet slang in parenthesis):
- The engine is street ported (SP).
TurboRX7.com > Porting Pictures
- The engine is running on an Apexi PowerFC (PFC) engine management system (EMS)
Power FC Forum - RX7Club.com
- The turbos have the "Rich man's" non-sequential modification.
Secondary turbo modification

If you are not familiar with the ATE Super Blue brake fluid, the idea is that during the next fluid change you flush it with ATE Typ 200 amber fluid. When the bleeder discharge turns from blue to amber then you know that the line is completely flushed. When you change the fluid 2-3 years later, you would use the blue again.

Thanks so much for the info. The car already has a koyo radiator as well as a greddy SMIC on. The mechanic told me that I already have everything I need for the single besides the single, manifold, intercooler and down pipping. I don't really know what to do to be honest! Lol.

So i have a n/a fc and i want a power upgrade, immediately what comes to mind is a turbo system. The only problem is i would be on a budget of $2500 and prices being spoke of would be at least an aditional grand on my max. Could i find a reliable turbo system for that amount? Or would it be best to swap to a 302? It would be for racing purpose , otherwise id keep it rotary.

what type of racing? and depending on what you source and use for a v8 swap it could be potentially the same amount if not more, depends all on what the car is specifically being used for

$2500 budget....and it's for racing? :scratch:

Yup like everyone else mentioned your turbo choice should depend on what you want to do with the car .. Dont jump the gun before you decide that . and dont be shy be honest . if you wanna race some 1000 HP vipers on mexico's highways.. not US high ways ofcourse...

then say so . or you want to track teh car , or drag race . it all changes turbo is like finding a good shoe .. you arent going to run a marathon in some dress shoes .

I really don't think I'm going to race it right now.. I just want to start by having one with minimum issues and learn about the car as it goes. The turbo he said he can get me is the S360 Borgwarner. Anyone know about this one?

Its just a start (what i had left from purchasing car) for a track oriented car. I know its not much at all but you gotta start somewhere. At the same time i just assume get more track time now while theres less money and power rather jump into a 400 hp monster i wouldnt know how to handle. Eventually i want to max it at 450hp with a full cage an all the goodies, but i cant afford it all in one go. Im doing the basics of gutting as well, that doesnt take a genious. Again im just asking if i can get any sort of reliable turbo system at all for that price. I know i can get the 5.0 and swap parts for that price.

Lots of good info on what to expect going to single from twin, but it appears this has the potential to turn out good once all the details are provided.