Help with tune/ecu questions rb25

[camo240]

I have a rb25 series 2 and I'm running a different turbo that came with my swap. It's a custom turbo. The guy said its just a little bigger than a gt2871r. Garrett won't email me back with specs yet. I'm also using the cxracing top/forward turbo mount manifold. Now I was told I need a power fc bc the stock ecu can't handle it? I'm not planning on going over 12-14 psi if I can still use stock ecu. I don't have motor in yet bc I'm waiting on my harness and need a one piece drive shaft and clutch and flywheel. So I want to get it all first before I swap it in. So my ?? Will I be ok running a stock ecu with this turbo and mani? If so what is my boost limit without tune? If I can't then best choice to run my car? Don't have a lot of cash but may be able to afford like 800-1000 when I sell my rb20 parts. I plan on doing a Freddy intake and injectors later down the road and want to run more boost later on. So what do you recommend? If someone has time to bs about this I will pm u my number. Any help is appreciated!!! I searched and so much flaming I can't get a real answer for what I'm running. Thanks

[fliprayzin240sx]

If its an upgraded turbo, no way in hell your stock ECU is gonna like it. Stock ECU will pretty much fritz on the stock turbo when you boost more than 10 psi. Flow of an upgraded turbo will be alot more air a stock turbo will produce. You need something to tune it and you'd also need larger injectors since you'd more than likely max out the stock injectors.

[camo240]

Damn so even if I ran 10 psi it won't be safe? And as far as it flowing diffrent wouldn't the maf keep up till a certain point? Unfortunately this is my only car and my rb20 jumped time and bent valves on me. So I. Went rb25 and the guy I got it from screwed me and sent me rb20 ecu and maf. So I was hoping for now I can run stock ecu with low boost if I had to just to drive it. Then work on a tuner like power fc or something better. Any ideas on how to do this safely for now with a rb25 ecu just so I can drive then work on a tune? What if I ran a stock turbo on my top mount manifold? Does the manifold change anything?

[Kingtal0n]

If you have an RB25 ecu
and you have an RB25 maf

First you need to verify that you actually have these. The best way to tell is to start the car and try to drive it. If it runs normal then you are in decent shape, however, you cannot boost it yet with the larger turbocharger.

To actually boost the engine with the larger turbo you need bigger injectors. No questions there, it will want gas and lots of it. Get yourself some 550~cc/min injectors at the minimum for 10~psi of boost it should be ok with any turbo.

Now you have to "tune" it. I used quotes because I am going to say something that no one will recommend of course, Use a SAFC-II.

Three good reasons to use a SAFC-II in your situation:
1. The stock ecu is for a turbo engine, so increasing the injector size to only 550cc/min will only add a few degrees of timing to your wide open throttle, you can compensate for this by lowering your base timing at the CAS slightly. As long as boost is ~10psi it will be fine.

2. if you sprung for an aftermarket ECU you would have a whole new problem which is getting it tuned, something that most people cannot do properly, even ones that claim they can.

3. Safc is quite cheap compared to a new computer + tuning.

I am going to repeat this again so you dont miss it: you need to verify, by driving, that your ECU + MAF is correct for your engine before you wire anything in (i.e. SAFC) and before you change injectors. If you swap the injectors and wire up the SAFC-II PRIOR to running the engine, and you cant figure out why it wont run properly despite having the right settings, you wont know if the ECU and MAF is correct for the engine. Don't go by the ECU cover either; people can change those in 30 seconds.

Furthermore, you need to boost leak check the plumbing on a regular basis; Get used to it. All Maf cars owned by people like us with these old engines need to learn how to do this properly. Build a boost leak check device out of some PVC and a tire valve and regularly fill the entire plumbing with compressed air to find leaks. This is the major #1 source for problems with these swaps and noobs.

[Kingtal0n]

The stock RB25 engines are very sensitive to air fuel ratio, it seems more so than usual. I have seem them lose rings at just 13.2:1 air fuel around 9psi.

You want that engine to be in the 11.5:1 range for best safety. It would make another 20~ horsepower if you run it at 12:1 but because you are using the SAFC and cannot directly pull timing I highly recommend you sacrifice the 20 horses for the sake of longeivity, install an AEM wideband about 3-4 feet away from the turbocharger, check for exhaust leaks, then tune the engine on a dyno so you can verify using the dyno's wideband that yours is reading correct. the dyno will read slightly leaner than yours, because of its location; You will want yours to say 11.4:1 and the dyno's to read about 11.8:1 across the board.

Dont let it creep up on you as the rpm passes 6,200, it will try, its not ok to let it creep up, keep the air fuel flat, even if it takes max adjustment and additional fuel pressure and dont take the engine over 7,000rpm for best longevity. Better to have an engine that puffs a little black smoke now and again than one that needs new piston rings.

[camo240]

Awesome info guys!!! Love the PVC idea I did something like it once but much more complicated lol. I just takes to my buddy's friend in 9k racing and he told me the same thing I thought. Bc the turbo is only a hair bigger and spools just a little faster I should be fine as long as I watch my afr and keep it at ten psi. I should be fine. I like the idea of a sfac2 cheap enough to pick up and throw in just as added protection. Now I need to get a rb25ecu and maf and sell my rb20 ones I got. I plan on doing a lot more down the road so I'm gonna put it together and see how it does then if all is good I will daily it gently until I get everything together and plan it out.

Let me ask u this, I want a greddy style intake with q45 style throttle body, I will like to do more boost then... And after I get bored of that I want cams. Then after that internals. So my question is what do I need to get to do step one the intake and more boost? I know injectors like u said at least 550s. But I know I will need bigger and don't wanna buy twice if I can. And what maf should I get? Should I just go for a z32 right now or?? My end goal will be a aem standalone?? Unless u recommend something different? Throw me some ideas and what's needed please and thanks again for the help and not flaming :) lol

[smoked240]

I would personally leave the head alone until 500hp+. I would keep the stock cams for now and throw some adj. cam gears on.

I have an aem v.2 standalone and it's awesome. Rb's must have a new ecu and proper tune to run for a long time when building. The stock ecu can support around 300hp but I would ditch the whole ecu and go aem or haltech.

[supersayianjim]

go nistune. unless you have $1,500.00+ for a aem stand alone.

ive had nistune for years. and I didn't know how to tune for shit. but if I can pick up and make kind of a decent map. so can you. and again the price point you can get a full nistune setup for under or around $600.00.

[camo240]

Ok I'm getting a stock Ecu and gonna find a safc and just run lower boost until I get a standalone. But I can't seem to find a answer on what maf to use??? Please let me know and reasons why. I would like to learn more about the mafs

[smoked240]

I believe a z32 maf is best to use but I could be wrong.

[supersayianjim]

^ you are NOT wrong!!

[camo240]

Getting a rb25 Ecu in a few days and will be looking for a z32 maf thanks a lot for the help this is why I love zilvia!!!

[fliprayzin240sx]

Also, just a heads up, if you get 550cc injectors and Z32 MAF, you can run your stock ECU. My car run with that until I installed my PFC and got it tuned. Something between the 2 nullifies the need to tune the stock ECU for some reason.

[camo240]

Hey I need you guys help again!! Car is finally running but I'm leaning out bad like starts at 14.6 idle and goes up as I drive to highest was 18-19 AFR so I'm scared lol I have a vafc I got it cheap IDC about the vct adjustment bc I have a s1 ecu ATM on a s2. I just went my tach and AFR to be right does anyone have a wiring how to or anything I can't find one in all the searches I do.. I have a z32 Mac sitting here right now I'm running a rb20\25 s1 maf Idc what maf I have to use as long as its running right please help

[Kingtal0n]

I told you to

#1 verify your stock maf + stock injectors + stock ecu run the car normal
#2 install an AEM wideband 3-4 feet from the turbocharger
#3 once the car is running normal during all situations with the original injectors/maf,

Then proceed to #4

#4 install slightly larger injectors and use an SAFC to tune the air fuel ratio to around 11.5:1 by watching the aem wideband you installed 3-4 feet from the turbocharger

Under no circumstances should you:
A: install an SAFC or larger injectors without first verifying the original injectors/maf/ecu all match by driving the car normally for as long as it takes (a few weeks wouldnt hurt) while watching the wideband
B: install a larger than stock maf sensor
C: install injectors that are more than 25%-30% larger than OEM
D: run the engine with the SAFC without retarding the ignition timing at the crank (CAS) by about 2-4* BTDC
E: run more than 10psi of boost TOTAL with the larger injectors, and no more than 3psi on the original injectors (or 0PSI if your wastegate will not support 3PSI) from a larger than stock turbocharger