View Full Version : RB25 NEO S2 car cuts out at full throttle

02-26-2012, 10:02 PM
So i have a RB25det NEO S2 and the motor is completely re built. I have the greddy style manifold with Q45 TB. Its running the R32 injectors and rail cause the NEO ones dont fit. The car runs great idles fine no problem except when in 4th or 5th gear around 50mph and if i 100% throttle it the car will start to go and boost fine then the car just cuts out like the ECU is telling it to. Its not running out of fuel like the injectors aren't working its like the ECU is cutting all spark to all cylinders and then if you stick with it it will come back on. I have a Apexi Neo in the car and the throttle is set correctly with the correct volts, and the air inlet percent thing never hits 100% thinking maybe the HY35 turbo i have is sucking to much air cause i only have 8lbs of boost. Ill try and get a video of it doing it so you guys can see. But dose anyone know why its doing this?! Is the ECU seeing something it dosnt like and just going to safe mode or something? Thanks in advance!! Feel free to ask any questions!

02-26-2012, 10:27 PM
what spark plugs and gap are you running?

have you checked your timing?

did this happen randomly or after you installed something?

02-26-2012, 10:50 PM
First off, what fuel pump and size injectors are you running. 8psi on a HY35/HX35 turbo aint exactly stock air flow. Either way, it sounds like you need a tune too. I wouldnt hold my breath for your engine to last with a SAFC. Lastly, stop stomping on the gas, sounds like your hitting fuel cut.

02-27-2012, 12:07 AM
the plugs are gaped to i think the 28 i dont remember but it was what ever majority of the RB guys run. The timing is right on to spec. Im running a walbro 255 and its the stock 370cc injectors. Iv had the car dyno'ed and its actually running fine until i get up to the 6,500 rpm mark but even then it only leans out till about 12 which i know isnt obviously good but for being stock ecu and running stock boost with that turbo it runs great no problems. recently if i get onto a freeway and ease the throttle it dose the "fuel cut". but why is it doing it? is it just because the turbo is drawing to much air. im going to a stand alone at some point but i dont have that kinda cash after building this motor up.

02-27-2012, 03:13 AM
How much HP were you putting down on the dyno? Also, what sparkplugs are they? Maybe you need colder plugs.

02-27-2012, 09:27 PM
Its doing 308whp 257trq. I'm running copper bcpr6es-11 for spark plugs. I dont think hte plugs are failing because the car dosnt sputter at all. Its like something is telling either the spark plugs or the injectors to just literally cut out and stop. The car runs great other wise no problems, just when at freeway speed and you try to boost real quick it will cut out.

02-27-2012, 11:03 PM
read through this without catching the fact that your are running a completely stock tune. that is your problem. you are right to much boost/airflow for the stock ecu. you need some kind of fuel cut defender. you need to A) turn down your boost or B) get it tuned.


02-28-2012, 12:29 AM
so let me run this by you guys cause i think im getting what your saying and this just popped into my head. Even tho the Stock ecu is set for 8lbs and im running 8lbs but because im running the HY35 and not the stock turbo im actually running the equivalent of what like running 10-12lbs? dose that make sense and is that right? So the ECU is seeing some extra boost and thinks somethings wrong so it is cutting everything to be safe?

Id have to buy a new wastegate because the spring is set to 8lbs at its low point and its kinda a old one. im looking into tune but before i drop $500 on a tune id rather do standalone and injectors then tune once. Like i said the car runs great and drives great it was just that weird cut at freeway speeds thing that i was weirded out about. I appreciate all your guys responses.

02-28-2012, 01:12 AM
I'd just drive the car normally without mashing the pedal until I saved up ~$1500 for a good tune setup. (injectors, maf, tune)