help with r32 rb25 swap

[ziggym28]

so just swapped an rb25 det into my r32 gtst , used the rb20 harness and modified the injector harness, swapped pins 112 and 114 for injectors, as im using the rb25det (series 2 by the way) ecu. i used the ingniter box and splitfire coils off the rb20, and am also using the rb20 maf. the car runs good and drives fine but when i lay into the throttle , its like it hits a flatline or cut of some sort, it still makes boost, but isnt a smooth pull... my rb20 pulled harder lol, any ideas?

[Skym]

TPS prevents engine running suddenly lean (lean = hesitation before accelerating), as MAF is too slow to react.

Stock R33 ECU can pull ignition timing to 0 (knock ignition map) when there's knock which should stop engine accelerating.

If fuel cut revlimiter happens at around 5000rpm, it can be due to faulty knock sensor (knock sensor error code on ECU).

[ziggym28]

i suppose it could be tps, its no so much a limiter, as its more the power just kind of slips away, kind of hard to explain but the engine sounds like its making some crazy power, but not actually pushing as much once i hit that point, its more like i cant notice it in the first 2 gears but it gets most noticeable in third

[Skym]

When open up intake, exhaust, add FMIC, etc a untuned engine should feel flat (normal). Ignition timing, fuel needs to match the mods and wakes the engine up (ECU tune is more important on a higher compression engine). So do cams (Tomei Poncams or similar). Also in midrange is where VVT switches over, so there's a dip in dyno graph power, torque curves when it does this and Poncams help to eliminate this dip. The dip is what you could be feeling, as well as engine being untuned.

3rd gear usually is the 1:1 gear ratio in gearbox (the gear that they dyno cars in). It should accelerate harder in that gear.

[ziggym28]

ok thanks alot, and how about this, my rb20 had 2 fuel pressure regulators? one on each side of the rail, and the single one on the rb25 i got, was broken, so i took one of the rb20 ones and put it on the 25, i also have a walbro fuel pump, havent hard wired that yet ( i hear thats a good thing to do?), anyways, do you think it could have something to do with having the rb20 fpr on?

[ziggym28]

cuz i have an intake , fmic, geddy style intake manifold, and 3 inch downpipe straight through
and the ecu is stock, and been sitting for a long time lol

[Skym]

One is a return FPR (rear of fuel rail or on return side of fuel rail that faces front of engine / car and sends fuel back to fuel tank), the other is damper FPR (entry for fuel rail or facing firewall). The return FPR can send a pulse back towards the damper FPR and the damper FPR sends a pulse towards return FPR. When the pulses meet (usually in the middle of fuel rail), they cancel each other out.

Similar to aiming two speakers at each other, both playing the same sound and they both cancel each other out.

With dual entry fuel rail the pulses enter both sides and cancels each other out in the middle of fuel rail. Fuel exits in the middle of fuel rail (middle of fuel rail has a braided hose with Sard FPR or similar that's mounted a small distance from fuel rail that returns fuel to fuel tank). Dual entry fuel rail is used when one fuel pump is not big enough to supply the fuel engine needs.

The RB20DET return FPR is used on RB26 engine as well (same fuel pressure), so shouldn't be a problem.

But not earthing fuel pump could be a problem. Also engine could be overfueling in mid to topend (would explain the flat feeling) if fuel pump is upgraded, but being not hardwired to get the 13.5 volts it needs (factory is 10-12 volts and 10 volts can be at higher rpm) it might not.

Also if engine has been sitting for a while, change oil filter, oil, spark plugs. Also fuel if over 1 year.

[ziggym28]

well i regasketed the whole engine, it has new oil, filter, plugs, has splitfire coils, so ill try hardwiring the fuel pump

[Skym]

Going by the mods engine has, it's probably way out of tune hence the flat feeling. Should be capable of 386hp (engine) at 12psi with stock turbo, boost up mods, Link or ViPEC ECU, etc.

[doc]

good to see we are getting to the bottom of this Zig.
i cant really help but i hope this works out

[supersayianjim]

you dont need that 2nd fuel dampner. just remove it and run your fpr(better fuel flow). also pick up a nismo adj fpr.

and also s2's have the ignitors already in the coilpacks, why go backwards with an external one??

[ziggym28]

well im using the rb25 fuel rail, just put one of the rb20 fpr's on it cuz the 25 one was broken, as for the coilpacks, i went with the external because it plugs into the rb20 harness? im not sure how to wire in the series 2 coils

[ziggym28]

good to see we are getting to the bottom of this Zig.
i cant really help but i hope this works out

yea bud i hope it does too! lol

[ziggym28]

can anyone tell me how to wire the series 2 coilpacks to the rb20 harness?

[Skym]

Series 2 RB25DET has the ignitors inside each coilpack (instead of ignitors inside ignition module that's located on top of back of engine), because you can shut the coilpacks off one at a time via ECU to check for faulty coilpack (have to have stock Series 2 R33 ECU, Nissan's Consult to do this). That's instead of removing coilpack cover, unplugging each coilpack one at a time to see if it affect's engine or not (not = faulty coilpack). Also if VVT is not working (running a retuned RB20DET ECU), that could explain the flat feeling as well.

You need the damper FPR on single entry fuel rail, don't remove it. Only time you remove damper FPR is when running a dual entry fuel rail setup.