BNR 2 or 3?
 

I'm going to stay with stock ports. Looking for about 300whp. I will stick with the stock top mount if I'm able to reach my goal with it. I have searched and browsed.

Seen the Stage 2 reach that goal only with porting done.

Stage 3 is more liking what I want/need. So if I go this route. How big of injectors should I run. 1000cc secondary with stock primaries or 720cc? And what piggyback is the best to go with? I saw lots go with Rtec but Im not sure if that for me yet.

I don't think you can get 300hp with stock primary's. Gonna need atleast 720cc, the secondaries sound good. You could go with a microtech but thats going to cost alot, or a power fc. I would recommend getting an fmic. The tmic gets heat soaked at 300hp.

I'm in the same boat as you. I'll be purchasing a BNR stage 2 or 3 sometime this summer and not quite sure what to choose yet. The 3 will definetly give you some more head room to about 330hp I think it's, as the stage 2 is 300hp. Go for the 3, cause I bet after a while you'll be wanting more hp. Even though it goes the same way with the 3, you'll want the 4 in about a year tops haha.

Yeah I figured that stocks wouldn't do it. Hahaha I was just looking at the Apex FC. Be good if I get one but hard to find now. I just wanted people not to think I was turbo'd upgraded if they didn't see a fmic. But yeah, I knew I would have to go that way eventually. Are the BNR 2 and 3 the same price like on the BNR site?

Anyways I was looking for something like his. Good reference for me.

https://www.rx7club.com/time-slips-dyno-128/bnr-3-15psi-stock-ic-808661/

I have a stage 3 and I love it! If your looking for 300WHP, its not hard with that turbo. Granted Im using a front mount and a ported motor I made 300 at 10PSI, and at 15PSI I made just under 350(needed more fuel)

Knock yourself out. http://www.bnrturbos.com/

The only differences between the 2 and 3 is a larger compressor wheel, clipped turbine wheel, and the wastegate is ported more. ...... I swear the 3 used to be about $30 more but it looks liek there the same price now! Sick! Definetly get the 3. .... I didn't realize either that the s5 is $100 cheaper then the s4.

hi guys,

imin the same boat as you guys as my car is quite rare (Luce) and has the series 4 version 13bt.

my project is to modify but keep it as stock looking as possible.

so the top mount has to stay. to which im going a custom core with the genuine top guard fitted.

cause mine is an auto as well, i got the stage 4 BNR straight up as the stage 3 uses back cut rear wheel which means the turbo looses some drive from the exhaust. which isnt what you need for an auto vehicle.

so by going the stage 4 straight up its a full t04 shell mated to the series 4 exhaust housing it should work well.

to combate the heat soak issue and to bring intake temps down im installing the coolmist dual water jet kit (water injection).

as for injector sizing

rule of thumb that seems to be on par with most "workshops" that know whats up...

Flywheel kW x 7 = cc flow per minute.
Divide across number of injectors.
this also has a safety margin built into it, so no need to go throwing heaps more than what you calculate.

Fuel pumps are same formula except multiply be 8 instead of 7... AND make sure that is the fuel flow AT THE RATED PRESSURE AND 95% DUTY CYCLE!!

Its funny how a 1600cc injector can flow 2000cc when its running 100% duty cycle and 70psi up it... So do you rate it at 2000cc or 1600cc??

I recently got the stage 2 because it has better response (less lag) than the stage 3 due to the smaller compressor wheel. I had 550/720s and maxed them out at like 10-11 psi, I'm currently running 550/1680s and it works fine :p:. but I'm switching in the 720s in the primaries just because I have them...

I'm aiming for 300ish with the stage 2, I'll post when I'm tuned enough to do a baseline with the stock top mount.

if a stage 3 can make 300@10 psi, a stage 2 should easily make well over that @ 15psi...

I'd say go with under driving the turbo versus over driving.

I've been running stock turbos ragged and regret having to rebuild them.

I'd say go with stage 3 and do 10 psi versus trying to push the stage 2 harder.

around 14 psi on a stage 2 is right around it's efficiency range (maybe a little high), but they also have the 360 degree thrust bearing, which protects you when you're spinning it a little faster.

and a fast spooling turbo is really nice...

basically it's a decision between spool time and maximum boost just like every turbo choice is... for 300 whp I would definitely go with a stage 2 though, for 350 you're in stage 3 territory.

Great thread, deffinitly useful, im planning on a Stage 4 build lookin for around 350. keep the info going, thanks guys.

To make your final decision, check out this thread, it's very usefull. Read what some of these people have put down with the different stages.

https://www.rx7club.com/time-slips-dyno-128/bnr-turbo-dyno-sheets-please-629521/

This thread will also give you a little more information, that I made a while ago. Mostly to do with fuel.

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/i-got-quicky-about-bnr-stage-2-3-a-783418/

The BNR stage 3 has the larger wastegate port.

BNR 2 - 34mm
BNR 3 - 35mm

I know it's only 1 mm but I figure that it will make some difference and as someone already said I would rather under work a larger turbo rather than overwork a smaller one.

I've read the top thread before, and didn't find it very useful... most of the people in that thread are running their turbos at the wrong psi... (ie: someone running a stage 4 at 10 psi and only getting 290 whp)

Yeah I looked at the first one. It was an ok source. So much crap in it that you cant really search well in it.

im running the stock IC on a BNR stage 3. From what Ive noticed running more than 11-12 psi on the stock IC does not get you much more power.. i noticed only 5hp difference on the dyno between 12 psi and 15 psi

what kind of power were you seeing on the dyno with the stock IC?

295whp at 15psi, streetported too

that's disappointing... what kind of ECU?

not really, i mean the stock IC is what is killing the power.. not much power is gained by turning the boost past 11-12 psi. It does give you a nice quick spooling torque curve though. this was with a haltech

Damn, thats really bad.

lol, I only said it was disappointing because I'm still running the stock top mount :p: It's good to know how much of a bottle neck it really is running an upgraded turbo..

Hey guys, here's a noob question for you. I was just on the BNR site looking at the different stages and they are making all the comparisons to the stock oem turbo. When you send them the core are most of you using the OEM turbo and getting it spec'd to their stage 2 or 3? Or are you guys sending after market units to be modified?

Just trying to figure out the best route to take. Not looking to spend 3 or 4 grand on a garrett or anything so if i can pick up a stock turbo and get it worked out by BNR i think this might be a better route. Looking to hit about 300-350 with street ported S4 turbo.

Thanks

BNR modifies the stock turbo. for 300-350 whp, I think a BNR would be fine.

Ahh ok nice i wasnt 100% sure what their setup was. Good to know, thanks!