FullmetalFD3S

Greetings All,
I'm in need of some advice from the experts on this forum, with regards to single turbo setups.

I understand that this topic has been discussed to death on the forum and i have searched a fair bit. But most discussions are between 5 and 10 years old at this point, which doesn't make it irrelevant but things do change.

What im finding difficult to figure out is the following.
What is a decent setup for someone moving from stock twins to a single setup? Bearing in mind i have a rebuilt stock port engine, with 2mm mazda apex seals. PowerFC and stage 1 exedy clutch.
Also, i am not looking to make big power numbers even below 300 hp is fine. What im looking for is some daily drive-ability similar to the twins. Still looking to run 10 - 11 PSI, nothing more.

Now Turblown Engineering seems to have what im looking for with a shorty cast manifold and Internal wastegated Borg Warner 7670 turbo. Seemingly outperforming the twin turbo setup even at lower RPM's.
But as i live in SA , its a package unaffordable to me considering i have to import it all and pay tax on my end on an already pricey package. Unless im able to find some parts used.

Now youre thinking why not get an upgraded set of BNR twins.Long story short, they cost a lot of money and you are still stuck with the old and complicated sequential control system.
If the turbos were to fail for whatever reason , you're back to square one as rebuilding is an unlikely option.

So getting down to the real question, Is there a recommended setup for someone like me thats looking for a slightly better than stock experience with a single?
What are the downsides of running a smaller turbo for that down low power experience? i know power suffers at top end but am i doing damage to a smaller turbo at high rpm?

Any advice / discussion would be greatly appreciated.

Regards
Brendon

DaleClark

iTrader: (55)

The IWG 7670 is a great way to go for what you are looking for. Near instantaneous response and nice power and it doesn't have an obnoxious external wastegate.

The BNR's are great and they ARE rebuildable, more so than the stock twins. Part of the upgrade process on the BNR's is going to more commonly available parts in the center section and ball bearings instead of journal bearings.

If cost is an issue, the BNR's would actually do better - going with a single you have other things to consider like re-doing intercooler plumbing, a new intake, etc. so that's more parts costs and labor. BNR's are straight bolt in and can use everything you currently have.

A good single turbo setup isn't cheap. If you do want something used and inexpensive you're going to get 10+ year old tech which means you'll have more lag but the capability for more power. The new internal wastegate Borg Warner turbos are quite new and you really won't see many used, if you do it will be for a small discount over new since they are in great demand.

Dale

Topolino

iTrader: (2)

IWG 7670 is definitely what you are looking for when upgrading the twins to comparable performance w a single setup; yet, still room to *reliably* up the boost if/when desired.

Note: Don't fret too much regarding pricing of the 7670 turbo kit. If you are patient, you are likely to see a gently used kit for sale soon enough listed at a good discount that should fit your *import* budget as I'm in the process of upgrading my system to the 8374 setup as we speak.

FullmetalFD3S

Wise words as always Dale,

I think one of the best options out there is the IWG 7670 setup. As you say its probably going to require me to go Vmount in terms of cooling.

For now i would probably have to stick with the twins for my goals. BNR's would probably be the way to go, if they are indeed rebuild-able.
What is the general opinion on reliability on BNR's nowaday's? i read some posts on the forum stating they dont use the greatest quality CHRA's for the upgrades, not sure how true this is.

Its a pity new replacement twins from japan are so expensive, when looking on RHDJAPAN for a new set , they make BNR's look like a steal.

Thanks
Brendon

FullmetalFD3S

Well well well Topolino,
This kit had my interest , but now you have my attention

Please do pop me a PM when you have it ready for sale. Im on a slow course trying to decide what to do and really like the simple setup and performance of the IWG kit.
As you mentioned, once installed , there is a lot of room for increasing power output when required.

In the meantime, i might have a look at what i can do about a vmount setup.

Thanks for the reply

Brendon

DaleClark

iTrader: (55)

BNR's had some problems when they were brand new but at this point they've been extremely reliable and proven.

Dale

Gilgamesh

Can you source EFR turbos locally?

If so then just buy the manifold and ancillaries separate from the turbo, the turbo is the biggest chunk of money from the kit price.

zx1441

I had the latest version of BNR twins installed back in May. Sequential mode too, and the car is very fun to drive. You will make 300hp with 8 lbs of boost if you choose to keep it low.

Topolino

iTrader: (2)

While a V-mount IC is ideal for optimum air temperature cooling, it's definitely not required for single turbos. I believe what Dale referenced was simply that your piping configuration to the IC changes when you go from twins to single. You'll need to have a local shop fabricate something for your specific setup; eg., turbo exit to IC inlet...

Narfle

iTrader: (16)

The external gate BW turbos are a great deal, way less $$$. And, external gate manifolds can be had fairly. Expect to dole out some money for tuning and fuel system upgrades also.

If you could make the twins work for you, they meet your goals. You could simplify the sequential system or run aftermarket solenoids and make ~300whp reliably. And, good used twins are pretty darn cheap.

TwinCharged RX7

iTrader: (14)

Yeah. If you only want a small improvement over stock, just turn up the boost a little.

FullmetalFD3S

Thanks for all the feedback guys,

Unfortunately i'm unable to source the EFR turbo's locally.

In terms of cooling , for starters i could definitely go with decently sized SMIC. When removing the stock airbox, ill have a decent amount of space to play with.

The externally gated turbos are definitely less costly, but adds a slight bit more of complexity. I would have to add at least one wastegate, which will introduce a possible point of failure.

The IWG setups just really simplify's it all, but the turbo's are pricier.

The twins definitely match my power goals, but damn have i been struggling to get my boost working consistently.
My secondary boost works perfectly, but as the car heats up, primary loses boost. I am 99 percent sure i do not have a boost leak, as i have checked and replaced everything as needed.
All vacuum lines and boost piping has been replaced.
Ive even built my own solenoid relocation kit using MAC valves.
But still experience boost loss.
It works brilliantly when everything's cool.
Also, i have a weird screeching sound coming from the turbo area , when the car gets really hot. Sound really only happens at lower speed and rpm, when pulling away fro a stop it will screech, at high rpm .
Had the car on a dyno last week and believe the sound originates from one of the twins.

Actually pulled the turbos this weekend, no major issues were discovered, no exhaust leaks. everything still seemed perfect.
Turbos are being sent in for a checkup this week.
Only thing i have not replaced yet is the turbo control actuator and the green pre-control / wastegate solenoids. Its possible one of these if failing as they heat up.

This is why im considering going single, its really a downer driving a car that works perfectly.... sometimes.

The IWG setup should give me close to stock experience with the option of scaling power in the future.

Any advice / discussion is greatly appreciated.

Regards
Brendon

nickl

Will be following! Also considering the same.

cib24

I don't see what is so complicated or wrong with the stock twins setup or why you can't rebuild them if the oils seals let go...Simple solution for you to overcome your heatsoak issues (I experience them too on my car in this hot summer we are having) is water injection and a vented bonnet.

BNRs are a waste of money in my view as if you want more power just turn the twins boost up and add water, and if you want even more than that then go single.

It's your money though, swapping to a single setup will cost you several thousand Rand because of the single turbo kit and all of the accessories you will need to buy to go with it.

JeffWels

I have new BNR's on my car running sequential still and absolutely love them. Sounds like you already have your turbos out of the car. I sent in my core on Monday and had the new turbos shipped to me on Wednesday of the same week from BNR. I wanted an ability to reliably hit 400whp with sequential twins, which is far beyond your HP goals, but you will have room to expand beyond there if you go with BNR;s now.

That said you should invest in cooling mods first. Sounds like you have a fairly stock car. I wouldn't touch your turbos without first visiting cooling/supporting mods.

Lastly, on your boost loss issue, check all of your check valves in the boost system. I had all kinds of boost problems with my car when i purchased it with the stock twins. Sometimes the primary wouldn't boost in 1st gear, the secondary would never hold boost etc. I replaced all solenoids and check valves and that fixed all my issues.

FullmetalFD3S

Thanks very much for the input Cib,
I have had my twins rebuilt once already locally, and actually do very much like them.
The twins themselves are actually in excellent condition, apart from a serious screeching sound that occurs when they've heated up.
When it screeches you can actually feel the vibration / resonance of the sound through the secondary turbo air inlet pipe.


This is what led me to pull the twin this previous saturday in search of the culprit. Thought i may be a gasket leak possibly, but there was no evidence of anything like that.
Sent the twins in to the original rebuilder and they inspected the internals and also found no evidence of failure. Keeping in mind that the twins have less than 2000KM's on them after rebuild.
The only issue seeming to be fairly minimal bearing wear.

As for the heatsoak issues, luckily i do also have a vented hood which i do believe makes a massive difference to this oven on wheels.
Water injection has always been in my plans, but i suspect will have a minimal impact on a failing solenoid or actuator, which i think is the main cause of my boost loss. Or am i missing an important aspect to the heatsoak , like some sort of thermal limit of the turbos, causing them not to create boost efficiently?
Sorry, im a bit of a newbie when it comes down to the true science behind turbos.

So, at this point im torn between deciding replacing the bearings on the twins and all gaskets , then replacing the solenoids/actuators that have not yet been replaced.
Or just eliminating most of the variables and doing a good proven single setup.

Apologies for the wall of text, i need all the sage advice i can get

-Brendon

FullmetalFD3S

Thanks for the advice Jeff,
i have replaced all my check valves with the viton ones, twice! Only unreplaced solenoid that remain are the wastegate / precontrol solenoids and the turbo actuator itself.

I am pretty sure i was close to solving the boost issue, but then the turbo screeching sound started. So while in the process of trying to sort it out, i started thinking , why not just trash it and move on, heheh

-Brendon

BLUE TII

iTrader: (9)

Screeching sound and vibration is usually the compressor or exhaust wheel of the turbo rubbing on the housing as it spins.

Since the turbos were recently rebuilt and bearings checked out, I would eliminate the usual worn out bearings as the cause for wheel to housing contact.

Other causes of wheel to housing contact are-

If you have an exhaust leak onto the compressor housing this has been known to cause the Aluminum compressor housing to grow from thermal expansion so much that it removes the clearance to the compressor wheel and they contact. This is especially possible on the 99+ High Power turbos as they use a very close fit compressor wheel to housing fit with abradable plastic insert on the compressor housing for very low clearance.

If you have a crack in the exhaust housing it is possible there is asymmetrical expansion of the housing and the exhaust housing contacts the exhaust wheel when heated up.

FullmetalFD3S

Thanks for the info Blue TII, appreciate it.
In the scenarios you mentioned above , would i be correct in saying that there should be visible contact marks on the inside of the housing?
Ill have to get the rebuild shop to specifically look for this in the morning. When i checked them on Saturday i did not notice any obvious markings.

Thanks again.
Brendon

BLUE TII

iTrader: (9)

If there was contact between either the compressor or exhaust wheels and housings the turbo shop should definitely see the marks on the wheels for sure and likely on the compressor housing as well. The exhaust housing is less likely to have visible marks.

FullmetalFD3S

Thanks for the reply,
Im guessing something is slightly out of spec in my tubo rebuild. I will have to sit down tomorrow and inspect everything again. And see if i should buy a rebuild kit. Gpop shops seems the only way to go, but is very pricey. 225 per turbo kit, Not sure if thats just because of rarity.
Refurb CHRA's from BNR ,could also be an option i guess.

-Brendon