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I pulled my engine for a rebuild and noticed my stock twins aren't in good shape. They seem to work fine (correct boost pattern and all) but they lose a ton of oil through the intake, and are caked in oil residue. The rear turbo manifold is cracked in multiple places and the gasket was split. The shafts have a little bit of vertical movement.
I see three options and I am looking for advice:
1. Keep using these stock twins (if they are still useable) and plan for a turbo upgrade later
2. Upgrade to BNR stage 3 twins for ~$2k
3. Upgrade to a single turbo kit that spools like the stock twins, without reducing reliability. Maybe a Borg Warner EFR 7670 kit? ~$3.7k+
Because I've already spent $3k to rebuild my engine, repair the transmission, replace the clutch, and a bunch of other parts, option 3 is pretty tough right now, and I am very hesitant to move that far away from the stock setup. I also just love having twin turbos. But if the 7670 is as good as it seems, I'll consider it, even if I don't do it now.
Current upgrades include: Koyo radiator, aluminum intercooler, dual oil coolers, and racing beat catback exhaust. I plan on replacing the precat with a downpipe during the rebuild, and getting a powerFC soon.
I'd recommend the 7670. It spools early and has great transient responce as well. I don't miss the sequential twins at all. no dip at transition, or odd laggy times if the tca was slow to close ect. plus really cleans up the engine bay, and reduces failure points
I personally would recommend going BNR stage 3 twins. I was in the same exact situation as you, spent a fair chunk of change on engine rebuild, transmission rebuild, new emissions equipment... money was a bit too tight to afford a single turbo kit so I purchased the BNR stage 3 twins. You will keep the down low response while gaining reliability, better cooling, and better top end power compared to the stock twins. Also keep in mind going with BNR stage 3 twins is pretty much a bolt on upgrade, just some bending of your water and oil lines.
I wouldn't run the BNR Stage 3 or the EFR 7670 on the stock ECU/ injectors, etc etc.
Even with the safety of the factory ECU 10psi fuel cut you will be running very lean in the high rpms at 10psi. You can't even run exhaust and intake on the stock ECU without this happening.
Then you are looking at $5-10K build not $2-3.5K for a BNR or EFR turbo upgrade.
So, unless you are looking to do a big build up of the car you are pretty much stuck with stock twins or sticking a header on it and some block off plates (hey, weight reduction and reliability mod!).
Correct me if im wrong, but i believe derSchwamm is getting a powerFC. Wouldn't he be able to get the BNR stage 3 and run the turbos at waste gate spring only with no boost control. He will still need a tune no doubt since the BNRs are pushing more air.
I would not run a turbo/turbos that I cannot match its output with fuel, but I wouldn't run a PFC either- so I guess there is that.
Like I said, it turns into $5-10K not $2-3.5K for the turbo(s) alone once you get ECU, injectors, rail, downpipe, tuning, etc. Probably can do it a bit cheaper than my estimate buying used outdated stuff.
Correct me if im wrong, but i believe derSchwamm is getting a powerFC. Wouldn't he be able to get the BNR stage 3 and run the turbos at waste gate spring only with no boost control. He will still need a tune no doubt since the BNRs are pushing more air.
Yep, I plan on getting a PowerFC regardless of what I do with the turbo to account for the downpipe I am installing since the precat isn't going back on. If another ECM upgrade would be better than the PowerFC, I'm all ears, but I didn't factor the PowerFC into the turbo prices above. I'm hoping to keep the stock fuel system for now and I'll run whatever boost level makes that safe.
One other consideration is that my car is almost stock right now, and I have all the parts to make it stock again. The BNR set just seems like I'd keep the car more 'stock' than going with a single, although I'd be happy to simplify that engine bay.
Nobody has provided any input on whether my stock twins look useable though. Am I at risk of harming my engine if these turbos give out? Is it significantly harder to get the turbos off with the engine in the car? If I can keep using my stock twins for now that'd be preferable, so I can do the turbos the right way later
It doesn't make much sense to buy a set of stock twins if you're going to replace them later. You'd be spending more money in the future. I'd got with the BNRs
It doesn't make much sense to buy a set of stock twins if you're going to replace them later. You'd be spending more money in the future. I'd got with the BNRs
So you're saying my current set is not useable? I was not going to buy new stock twins if they are not
Those twins are rough but you could clean them up and run them, long term you'll need to replace them. I've seen pictures of stock twins in much worse shape than yours pop up on here over the years.
So you're saying my current set is not useable? I was not going to buy new stock twins if they are not
BNR's are ~$2,400, a secondary step up kit with new injectors is ~$800, a PFC is ~$750 used w/ commander, and a tune will be ~$600. Total is $4,550, if you throw is $450 for a fuel pump upgrade an incidental items you're looking at $5k to upgrade to BNR's that you can run turn key without worry.
An EFR kit is going to be around $4k by itself and you'll still need supporting mods. Going used is always an option but if you want to "one and done" for a turn key car buying new parts is usually best.
If money is an issue for you just buy a set of good low mileage twins and port the wastegate. N3G1 twins are an option too (good used are ~$800-1,500) but you'll need some supporting mods and a tune to run those as well.
Just food for thought, once you make the decision to upgrade the costs don't stop.
Keep in mind that this isn't something you need to do RIGHT NOW. The big pitfall of an engine rebuild is the "while you're in there" gotchas, there are a zillion things you can throw money into during a rebuild.
The cracking on those turbos is about normal for a set of N3A1 turbos. Cracking is only a problem if a) the cracks go under the gasket surface, or b) if there are a lot of cracks around the wastegate/precontrol doors that allow exhaust gasses to bypass the door. The N3C1 turbos are the same but much less prone to cracking, and the N3G1 turbos are the 99 spec turbos.
It sounds like you have a lot of money in the rebuild already and sinking money into turbos right now isn't the way to go. I would clean those turbos up good (they are filthy!), replace any gaskets that are compromised, maybe new coolant hoses for the turbo and all new oil return gaskets. Maybe also replace any missing/broken studs and replace the stock turbo nuts with copper lock nuts.
Get the engine broken in, get things dialed in and happy. Start with any supporting mods that are needed - PowerFC, fuel pump, intercooler, etc. Then look at your budget and see what you want to do.
Cheapest option - good set of used twins, preferably N3C1 twins, about $300. Bolt in, done.
B - 99 twins, used, about $1000 or so.
C - either new 99 twins or BNR's. The 99s will give more low end grunt and not need a lot more as far as supporting mods go. The BNR's will probably want some more mods to get the most out of them. Both are easy bolt on and go.
D - single turbo kit. This is the "You must be this tall to ride this ride" option. You'll need good exhaust, PFC, bigger injectors, fuel pump, intercooler at minimum. Also will need a proper tune or you will have a hand grenade.
PFC is probably the best computer for you. The others out there will cost more and have more power, but will require a LOT more expertise when it comes to tuning, wiring, etc. PFC is damn near plug and play, is very well supported and documented, and really works damn well.
Keep in mind that this isn't something you need to do RIGHT NOW. The big pitfall of an engine rebuild is the "while you're in there" gotchas, there are a zillion things you can throw money into during a rebuild.
The cracking on those turbos is about normal for a set of N3A1 turbos. Cracking is only a problem if a) the cracks go under the gasket surface, or b) if there are a lot of cracks around the wastegate/precontrol doors that allow exhaust gasses to bypass the door. The N3C1 turbos are the same but much less prone to cracking, and the N3G1 turbos are the 99 spec turbos.
It sounds like you have a lot of money in the rebuild already and sinking money into turbos right now isn't the way to go. I would clean those turbos up good (they are filthy!), replace any gaskets that are compromised, maybe new coolant hoses for the turbo and all new oil return gaskets. Maybe also replace any missing/broken studs and replace the stock turbo nuts with copper lock nuts.
Get the engine broken in, get things dialed in and happy. Start with any supporting mods that are needed - PowerFC, fuel pump, intercooler, etc. Then look at your budget and see what you want to do.
Cheapest option - good set of used twins, preferably N3C1 twins, about $300. Bolt in, done.
B - 99 twins, used, about $1000 or so.
C - either new 99 twins or BNR's. The 99s will give more low end grunt and not need a lot more as far as supporting mods go. The BNR's will probably want some more mods to get the most out of them. Both are easy bolt on and go.
D - single turbo kit. This is the "You must be this tall to ride this ride" option. You'll need good exhaust, PFC, bigger injectors, fuel pump, intercooler at minimum. Also will need a proper tune or you will have a hand grenade.
PFC is probably the best computer for you. The others out there will cost more and have more power, but will require a LOT more expertise when it comes to tuning, wiring, etc. PFC is damn near plug and play, is very well supported and documented, and really works damn well.
Dale
Thanks. Since no one seems to think that it's dumb or dangerous to keep using my current turbos, I'll just clean them up and reinstall. I may upgrade turbos later AFTER I've done the supporting mods.
I'm glad to hear the BNRs have a lot of votes here – that's what I have been leaving towards mostly due to them being basically stock replacement turbos that hold up better, but I'll make that decision when the time comes.
Dale put it very well and I agree. If the turbos make boost and you are working with budget constraints, leave the turbos alone. Much of the oil can be from the stupid stock pcv system that dumps oil into the primary turbo inlet. Block the pcv valve and run a vented catch can in line with the hose that goes to the front turbo inlet and a lot may clear up.
Break the motor in as is, and slowly accumulate the parts required for either the BNRs or a single turbo. I would only stay with stock twins if you never plan to make more than 300-320whp consistently. Any more and they just don't last. BNRs are the most cost effective upgrade. If you are interested I can get you the best price on them. The EFR 7670 will spool nearly as fast as the twins, make a whole lot more power, and greatly help reduce underhood heat. I can build you a full kit with a properly designed true equal length manifold for the best spool and boost control.
How big is your budget? If I were looking to stay within the 350hp range I would simply get your twins rebuilt and find a good used exhaust piece that isn't cracked or as cracked.
Think about the big picture here and what you want out of the car. How much do you want to learn and how much do you want to drive? The further you get away from stock hardware/stock ECU, the more learning you do but the less carefree driving you can do.
You have to put the concept of "reliable single turbo" in context. Jumping from a stock ECU level of mods to Power FC level of mods is a big step in terms of compexity/stuff to worry about. Now you are looking at your boost pattern, adjusting boost controllers, looking at a wideband o2 gauge. Jumping from Power FC with bolt ons to single turbo is another big step.
So basically it's a leap going from stock ECU, barely modded to single turbo. There are so many more things you have to think about, so many more things to check. Like, you need to be sure the tune is ok as the seasons change (a mild concern on bolts ons + Power FC, bigger concern on bigger fuel system and single turbo). You'll find yourself looking at your boost gauge and wideband every thing you hit the gas pedal. You'll be playing around with the idle a lot to get it right. You start thinking about how much fuel you have in your tank and whether you should have put a fuel cell in there in case the tank gets too low. You pop the clutch in as you approach a stop sign and hope it doesn't stall due to the combination of your clutch/flywheel and the idle deceleration tuning.
You start looking at intake air temperatures and knock readings all the time. If it's in the middle of the summer and all you've got is a catback, it will still drive great and idle smoothly when you hot start it after stopping for gas. When you have big injectors, aftermarket fuel pressure regulator, a single turbo, you start driving it differently after a hot start. You're looking at all your gauges all the time and constantly tinkering with it. Or you go the "ignorance is bliss" route and cross your fingers that nothing goes wrong.
You don't just put the single turbo in, go to the tuner for a couple hours, and from then on drive it the same way you did when it the car had was a catback and a small stock mount intercooler. The whole ownership experience changes. It's not a "normal" car anymore (by the definition of people who are not serious enthusiasts). You can't just give the keys to somebody without giving them a long explanation of stuff.
Think about the big picture here and what you want out of the car. How much do you want to learn and how much do you want to drive? The further you get away from stock hardware/stock ECU, the more learning you do but the less carefree driving you can do.
You have to put the concept of "reliable single turbo" in context. Jumping from a stock ECU level of mods to Power FC level of mods is a big step in terms of compexity/stuff to worry about. Now you are looking at your boost pattern, adjusting boost controllers, looking at a wideband o2 gauge. Jumping from Power FC with bolt ons to single turbo is another big step.
So basically it's a leap going from stock ECU, barely modded to single turbo. There are so many more things you have to think about, so many more things to check. Like, you need to be sure the tune is ok as the seasons change (a mild concern on bolts ons + Power FC, bigger concern on bigger fuel system and single turbo). You'll find yourself looking at your boost gauge and wideband every thing you hit the gas pedal. You'll be playing around with the idle a lot to get it right. You start thinking about how much fuel you have in your tank and whether you should have put a fuel cell in there in case the tank gets too low. You pop the clutch in as you approach a stop sign and hope it doesn't stall due to the combination of your clutch/flywheel and the idle deceleration tuning.
You start looking at intake air temperatures and knock readings all the time. If it's in the middle of the summer and all you've got is a catback, it will still drive great and idle smoothly when you hot start it after stopping for gas. When you have big injectors, aftermarket fuel pressure regulator, a single turbo, you start driving it differently after a hot start. You're looking at all your gauges all the time and constantly tinkering with it. Or you go the "ignorance is bliss" route and cross your fingers that nothing goes wrong.
You don't just put the single turbo in, go to the tuner for a couple hours, and from then on drive it the same way you did when it the car had was a catback and a small stock mount intercooler. The whole ownership experience changes. It's not a "normal" car anymore (by the definition of people who are not serious enthusiasts). You can't just give the keys to somebody without giving them a long explanation of stuff.
haha this is a great way to put it.
after reading what stuff u have done already, id retract my recommendation of the EFR, and just keep your turbos for now. I went from a downpipe and catback, to the power FC, then a resonated midpipe, 99 y pipe, intake,thicker smic, and slowly had to keep changing the tune as I added stuff.
Then when I went to the EFR and going with a larger smic I ended up totally changing my tune pretty dramaticly, and am more constantly watching things. I still have the stock injectors/pump and am at 90%+ dc at 12 psi, so now I'm looking to change things even again once I upgrade the pump and secondarys.
As simple as the single setup is, the complexty lies in tuning now since its so far from stock.
after reading what stuff u have done already, id retract my recommendation of the EFR, and just keep your turbos for now. I went from a downpipe and catback, to the power FC, then a resonated midpipe, 99 y pipe, intake,thicker smic, and slowly had to keep changing the tune as I added stuff.
Then when I went to the EFR and going with a larger smic I ended up totally changing my tune pretty dramaticly, and am more constantly watching things. I still have the stock injectors/pump and am at 90%+ dc at 12 psi, so now I'm looking to change things even again once I upgrade the pump and secondarys.
As simple as the single setup is, the complexty lies in tuning now since its so far from stock.
There is some truth to that, but the way we tune cars in house the car will start up hot or cold, be manageable in traffic and daily driving (weather permitting), and survive at the track. The tune is one of the biggest factors that affects the drivability of a car. One of the biggest mistakes people make is think a few full throttle pulls is all it takes to tune a car. You missing out on a lot. That being said one of the important things I always tell people before they drive a single turbo rx7 or any modified car is to go easy until they get used to it. A modified car can have a much different power delivery curve than a stock car.
On a mostly stock car, you just need to keep spending time/money to replace the OEM parts that reach end of life. Turbos go, you get rebuilt ones. Motor wears out, you rebuild, and there are a lot of warning signs that it's time. You don't get much oddball stuff though and you don't get catastrophic failures (sudden blown motor) if you replace the wear items like AST and coolant hoses. There's literally a gazillion page manual on how to keep the car going, and a tune that works in all temperatures and altitudes, with only the 3000rpmost hesitation as a possible annoyance. The check engine light works so you get fair warning of basic problems without having to actively check things. For example, people see the oil metering pump limp mode on stock ECU as an annoyance, but it's still a highly engineered system to protect your engine.
On a single turbo car you need a healthy sense of anxiety and a lot of engagement to keep it together no matter how good the tune is. I say that as someone who respects good professional tunes and as someone who has spread a lot of knowledge of good tuning practices. Even if the tune is not a problem, all the non OEM stuff can be potential problems. You've got to be mindful of cracked manifolds, boost leaks, exhaust heat getting into the cabin, fuel lines you assembled leaking, and the list goes on.
That doesn't mean you shouldn't single turbo it or ditch the stock ECU on stock turbos. The car is going to be way faster and higher performing, but it's a different kind of enjoyment.
I had a feeling a single turbo wouldn’t be so easy, but the first people I talked to made it sound like it’s dumb to do anything else when your factory turbos die, so I thought I’d ask.
My FD is clean and almost stock and I feel bad moving too far away from that for now. I want to take care of it in it’s factory form, even if I’m elbows-deep in vacuum hoses. Maybe I’ll get BNRs some day, when these turbos die completely, but I’ll plan on breaking in my rebuilt engine stock.
10-02-17, 08:36 PM
