I'm currently looking at a full overhaul of my engine (coolant seal letting go...) and was thinking it would be a good time to transition turbo setups, if necessary.

Goal for the car is to be a fun, reliable weekend machine that sees regular autocross (I'm already in SSM for my hood so class be damned lol) and occasional HPDE on track. Power-wise I would be happy with 300whp; my priority is response.

Is there a setup better than stock twins for this kind of duty? I've heard the 99 spec get bashed, but typically from those comparing it to BNRs... but usually the people going for BNRs want 380whp+ which is where most regard reliability/cost ratio to effectively go down like a lead balloon.

I searched and most people going for singles want the moon (400whp+ with near-stock response), so either I'm blind or the info is old, but is there a single setup nowadays for my goals that has advantage enough to justify the cost?

Thanks in advance for the info!

 

The Borg Warnert EFR turbo's are very responsive with the lightweight Ti exhaust turbine wheels.

If you want super responsive go with an EFR 7670, if you want responsive and a little more up top an 8374 is perfect.

 

BorgWarner EFR IWG FD3S Turbo System

Dotted line below is boost pressure, solid is RWHP.

 

For your usage, '99 twins are a very good bet. There's really no need for all of the bashing they get. I've run them for YEARS on (road racing) track at 13 psi, making 340 to 350 rwhp and very hard use, and it outruns many small single kits.

Not that I wouldn't LOVE one of those BW single turbo kits...

 

The only thing better than more horsepower, is even more more horsepower....

 

I agree with the above. I don't think you can beat the low end responsiveness of the 99 twins. I've had mine for about seven years with no problems. I do 2 or 3 autocrosses a year, and wouldn't want a single turbo for that. With an oem cat and smog pump, I have around 320 rwhp at 13 psi.

 

Yup, I think the BW EFR 7670 is an awesome option for exactly this. But the price is too much for me to justify myself at over 2k for the twin scroll internally gated 0.92a/r t4 with the 3" v band outlet. At 14-20 psi with a huge exhaust should be a response monster.

So I've been looking at the BW Airwerks s200sx 7670 as it's a 1/3 of the price but requires external Wastegate so cost goes up. I'm building a t2 motor. So a lil diff. But interested to hear your decision and results. Good luck

 

Thanks for all the replies!

Those BW EFR turbos are good to know about, but the cost, not to mention the supporting mods, is a bit pricey for now... I may revisit that option in the future though..

If I were to choose between 99 spec and BNR, I do have a few questions... Is it disadvantageous for me to run BNR over 99 spec if my goals are low (I will likely be at 10-12psi MAX), since the BNRs were designed out to ~18psi, efficiency wise?

I'm not a powertrain engineer, but it seems as if it may fall into the same realm as running a GT40 and shooting for 350whp when the turbo is made for double that.

For people that bought just the BNRs second hand, what needs to be done to adapt to the setup? I believe the ypipe has to be reworked (is this easily done? how much does BNR charge to just perform the mod if not?) but I have not heard of any clearance issues, new intake piping, etc...

For either of the twin setups, is a new tune necessary? or is the base map viable for stock boost? still using a PFC.

 

Most of the people here in CO have some sort of stock twins, 99 twins, or BNR twins. Most of them switch because of the hassle of getting these turbo's to work properly in sequential mode. All them, yes, 5-6 FD owners here have all switched to either a non-sequential mode to reduce the vacuum lines and failures through out the system, or they couldn't get the turbo's working properly cause of other issues and went single turbo.

I tuned these cars, and the efr7670 whips them up with low end power and torque. It would be like comparing a V8 to a stock turbo system, it's that big of a difference. My GT3574R makes more power down low than the stock non-sequential twins, and we have never had a great running stock sequential system to compare to.

I do think for longevity the stock system is great because of how everything is controlled, wastegate, hard lines for cooling system, etc. They just seem to be a big pain in the butt to work right and for long periods of time after the system gets old.

 

They don't make 99 twins any longer or Mazda does not import them.

 

Our iwg 7670 is probably the fastest spooling turbo configuration ever produced for a 2 rotor engine . It will blow any stock twin turbo configuration out of the water.

The cost of an ewg airwerks 7670 is pretty close in price to our efr iwg 7670 kit. There is only a $1000 dollar difference between the two, but you need a Bov, the flange welded on, atleast one If not two wastegates(twin wg will give better response ), one or two open dumptubes, and wg runners . Then you will still be stuck with a journal bearing airwerks with dated wheel technology.

 

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I am in a similar boat. I want a fun, reliable weekend machine that sees curvy rds and a few HPDE a year and here what’s been going through my head.

I’m currently on OEM twins with simplified non sequentials with DP, ported wastegate and full exhaust
• Pros – simple setup and easy to maintain
• Cons – kinda laggy on the low end

Kinda want OEM twins with simplified sequentials
• Pros –affordable, little more complex that non sequentials but won’t be terrible to maintain
• Cons – having the 2nd turbo kick on while trying to haul *** on a curvy road might be challenging and heat management might be an issue on HPDE

BNR and 99 spec
• BNRs are expensive if you get them newly rebuilt
• If you can get a good condition 99 specs for a decent deal then go that route but me personally I wouldn’t pay more than $500.

Borg Warner internal wastegate turbos
• Pros – simple setup and fast spooling
• Cons – cost and from what I understand the turbos aren’t rebuilding and if you blow an apex seal and that gets sucked into the turbo say bye bye to 2gs.

Aspec or Turbo blown turbo setup
• Pros – great response and good quality turbo
• Cons – personally I just don’t like the complexity of dual wastegate.

As far as engine management. Having a new flying lead harness to replace the old crispy FD harness would be nice but that’s time and money. Adaptronic and Haltech seem like awesome ECUs but gets costly due to tune and dyno time.

The route I’m leaning towards right now is OEM twins, simplified sequential setup, aftermarket SMIC, Supra fuel pump, Pettit tuned ecu, AEM water injection kit, turn up the boost to run 12 / 10 / 12 pattern.

Hope this helps.

 

There is a local guy here who went with the 99 spec turbo's and went to a simplified sequential but couldn't get them to work properly. He then went NS and they still weren't working right. He dumped them for a single wastegate A-spec GT3574 turbo that is new for 1800 shipped off this forum. We are doing a custom v-mount and custom fuel system with FFE rails and EV14 injectors for cheap. His car had a koyo that we are welding up for modification, and we purchased the correct sized intercooler off ebay for like $140 shipped or so. We are fabbing up a intake pipe to place the filter in the mouth of the bumper between the intercooler and radiator for cold air and ducting everything. I will be tuning it for him.

This whole system was pretty damn cheap and should be responsive and reliable.

The EFR7670 in Speedjunkies car moves like a beast. It will decimate the stock turbo in response and power.

We have more cars putting in single turbo's here, one with an EFR8374, a BW forget the size (S363?), and one with a NS set up.

 

If sequential isn't working with either the BNRs or 99s, you have another issue. Usually it is a control issue related to a solenoid or check valve. Even if you don't want a whole lot of power, a single turbo greatly simplifies the engine bay, makes room for airflow, gets rid of the heavy stock cast manifold that traps heat, and makes it easier to work on the car. Done properly it makes for a much more reliable setup. The downside is obviously cost. A T3 35R will spool extremely fast and be more affordable. Just something to consider.

 

I love my sequential 99 twins.

Rotary Performance | FD Turbo

quick spool up for excellent street behavior and make good power up top as well. Once they work right, they stay working right in my experience.

 

EFR 8374 is an amazing turbo.

 

Very happy with my BNR stage 3 sequential twins. It is a shame that folks just "give up" on making the sequential twins work properly. The low end is fun and responsive, then the power really comes on with the secondary when you get there.

 

^ people "give up" on the sequential stock twins because there is a huge flapper blocking exhaust pulses and holding in the hottest heat from the deepest depths of hell.

 

I don't hang around here very anymore so I'm a little bit outdated with my knowledge...


****! I'm sold. ~192HP @ 3200RPM???!!! In terms of the low end power I can't see sequential twins (99, BNR's or stock) outperform that. Nevermind not having to deal with a sequential setup.


If I ever need to replace my GT35R I know what I'm getting. No question about that. Edit- Elliott, In fact I might just give you a call to get some info.

M-

 

****! I'm sold. ~192HP @ 3200RPM???!!!

Exactly! I am working on putting an EFR 7670 on my FC.

Just remember that graph is like 24psi boost on E85.

I am going with two 44mm external WGs to try to run 10psi on pump gas (our gas is really bad around here) and whatever boost the car makes good power on with race gas.

Maybe I should have used both IWG and EWGs as I have never had a turbo 7 that didn't boost creep like crazy (sea level, cool temps year round)...

300rwhp @ 10psi with this turbo should be pretty enjoyable on the street. I am expecting to get 10psi at 2,000 to 2,500rpm, so it should drive like 300rwhp on sequential twins.

 

^ people "give up" on the sequential stock twins because there is a huge flapper blocking exhaust pulses and holding in the hottest heat from the deepest depths of hell.

While that is representative of turbo track guys, I feel stock twins work well for street use and sprint racing.

If you go to the extreme of endurance racing you are going to end up ditching the turbo for an multirotor NA (3-4 rotor).

ie-
^ people "give up" on turbo rotaries because there is a little spinning pinwheel blocking exhaust pulses and holding in the hottest heat from the deepest depths of hell.

Shades of gray...

 

I'm noticing that everyone's definition of low end is different. To me that would be idle to 3k. 3k-6k would be mid range and 6k- 9k top end. With that being said, properly running stock or 99 twins will beat this turbo below 3k in response. I dont think this single will make 14psi on a 13b below 2.5k like sequentials already do. Now I have become an NA guy so I may be out of date on my turbo knowledge. For dailey driving in stop and go traffic, nothing beats the twins.


Edit: I just relooked at that chart and I must say that damn this single is impressive.

 

I dont think this single will make 14psi on a 13b below 2.5k like sequentials already do

As you can see from the chart that is about what the 8374 is doing.

The 7670 has a much lower surge line and is smaller so I expect even better boost response.

Now if you got a couple EFR 6258s in the stock sequential housings it would be downright insane response...

 

I wonder if there would be enough room to run twin EFR 6258s, would be crazy.