Dyno Graph - MAF or fuel pump problem? - GT-R Register - Official Nissan Skyline and GTR Owners Club forum

NewClearBomb · 26th July 2005, 10:41 AM

I had my car on Thor's rollers at JAE at the weekend and although I'm pretty pleased with the potential I've got, it was detting pretty badly under full load at high RPMs

It started running lean from about 5500rpm and started detting pretty much straight away after that.
The analysis on the day was that the fuel pump was on it's way out, but I'm wondering if it could be that the MAF was maxxed out.

quick spec of the relevant stuff is:
RB25DET series2
R33 GTS ECU
HKS FMIC
Apexi induction kit
Free flowing cat-free exhaust
Hybrid rollerbearing T3-core steel-internals turbo running 0.85 bar
GTR fuel pump

Graphs are here:

I've got a walbro 255lph pump I can put in, but am I wasting my time doing that? Does it look like it could be the MAF is maxxed out?
Any pointers greatfully received.

The long term plan is for 550cc injectors, Z32 MAF and some engine management, but for now I just want to stop it exploding

Could always retard the timing a degree I suppose....
cheers all

NISFAN · 26th July 2005, 11:16 AM

Have you still got two stage boost on it? First stage by 3200RPM, and then more boost from 5000 ish.

AFR is not very smooth across the rev range. I think your risking an engine blow up without fitting something like an Apexi Power FC. The MAF should go a little higher than 300bhp. Possibly injectors or fuel pressure are not capable. Anyway a PFC will give you feedback to let you know what % injectors, MAF etc are doing.

NewClearBomb · 26th July 2005, 11:20 AM

I'm getting full boost by about 3000rpm and the actuator gets it's pressure directly off the plenum, so no. I guess the 2 stage boost is gone.
Sounds like the pump is on the way out, but that I'm also right at the limit of the MAF...
I'lll wack another pump in this afternoon and see where that leaves me.

But yeah, long term, the engine management, injectors and MAF all need sorting regardless

NISFAN · 26th July 2005, 11:29 AM

Interesting, NVCS kicking in at 5000rpm? Making more difference than 'normal'?

Must be something else giving that torque bulge @5K if it isn't boost, ignition timing going off on one?

NewClearBomb · 26th July 2005, 11:31 AM

didn't think there was any variable timing on the non-NEO RB25DET.
What the guy said was that as the fuelling started to run lean at about 5000rpm the power increased and he thought that would be because of a faulty or tired fuel pump

NISFAN · 26th July 2005, 11:39 AM

If it's a spec 2 RB25DET then has got NVCS, easy to check, bulge in cam cover on inlet cam side, and a solenoid on front drivers side of engine. Normally comes in at 4.5K.

AFR runs quite rich up to 5000, then starts leaning out, actually that will explain the torque bulge. Could be MAF, injectors, or Fuel pressure. Install a FP gauge, and multi meter the MAF, if it goes up to 5V then you have run out of MAF range.

NewClearBomb · 26th July 2005, 11:53 AM

cool, thanks

I'll check the cam cover shortly.
If I'm considering a power FC, do you know if I need a specific spec2 one to handle the NVCS?

NISFAN · 26th July 2005, 11:58 AM

No, any R33 GTS-t PFC will have the control for NVCS. Spec 1's also had NVCS.

NewClearBomb · 26th July 2005, 12:00 PM

cheers

skylineman · 26th July 2005, 12:20 PM

hi, my gtst does the same thing, apparently its running out of fuel, mine dies off about 5500rpm then i get a kick at about 5900 till the red line.
ive just ordered 550cc injectore, pump, PFC, and afm. give those ago

NewClearBomb · 26th July 2005, 12:25 PM

which 550cc injectors have you gone for and where from?
I'm not sure which engine management to go for yet, there's a few options available I'm looking at

skylineman · 26th July 2005, 12:42 PM

to be honest not sure what there called they came with a 255lh pump.
i was going to have a custom ecu and loom from jamsport but everyone thinks pfc works well, so ill try that

26th July 2005, 10:41 AM	#1 (permalink)
NewClearBomb GTR Register Member Join Date: Sep 2003 Location: Birmingham Posts: 74	Dyno Graph - MAF or fuel pump problem? I had my car on Thor's rollers at JAE at the weekend and although I'm pretty pleased with the potential I've got, it was detting pretty badly under full load at high RPMs It started running lean from about 5500rpm and started detting pretty much straight away after that. The analysis on the day was that the fuel pump was on it's way out, but I'm wondering if it could be that the MAF was maxxed out. quick spec of the relevant stuff is: RB25DET series2 R33 GTS ECU HKS FMIC Apexi induction kit Free flowing cat-free exhaust Hybrid rollerbearing T3-core steel-internals turbo running 0.85 bar GTR fuel pump Graphs are here: I've got a walbro 255lph pump I can put in, but am I wasting my time doing that? Does it look like it could be the MAF is maxxed out? Any pointers greatfully received. The long term plan is for 550cc injectors, Z32 MAF and some engine management, but for now I just want to stop it exploding Could always retard the timing a degree I suppose.... cheers all

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26th July 2005, 11:16 AM	#2 (permalink)
NISFAN GTR Register Member Join Date: Oct 2003 Location: Herts Posts: 1,696	Have you still got two stage boost on it? First stage by 3200RPM, and then more boost from 5000 ish. AFR is not very smooth across the rev range. I think your risking an engine blow up without fitting something like an Apexi Power FC. The MAF should go a little higher than 300bhp. Possibly injectors or fuel pressure are not capable. Anyway a PFC will give you feedback to let you know what % injectors, MAF etc are doing.

26th July 2005, 11:20 AM	#3 (permalink)
NewClearBomb GTR Register Member Join Date: Sep 2003 Location: Birmingham Posts: 74	I'm getting full boost by about 3000rpm and the actuator gets it's pressure directly off the plenum, so no. I guess the 2 stage boost is gone. Sounds like the pump is on the way out, but that I'm also right at the limit of the MAF... I'lll wack another pump in this afternoon and see where that leaves me. But yeah, long term, the engine management, injectors and MAF all need sorting regardless

26th July 2005, 11:29 AM	#4 (permalink)
NISFAN GTR Register Member Join Date: Oct 2003 Location: Herts Posts: 1,696	Interesting, NVCS kicking in at 5000rpm? Making more difference than 'normal'? Must be something else giving that torque bulge @5K if it isn't boost, ignition timing going off on one?

26th July 2005, 11:31 AM	#5 (permalink)
NewClearBomb GTR Register Member Join Date: Sep 2003 Location: Birmingham Posts: 74	didn't think there was any variable timing on the non-NEO RB25DET. What the guy said was that as the fuelling started to run lean at about 5000rpm the power increased and he thought that would be because of a faulty or tired fuel pump

26th July 2005, 11:39 AM	#6 (permalink)
NISFAN GTR Register Member Join Date: Oct 2003 Location: Herts Posts: 1,696	If it's a spec 2 RB25DET then has got NVCS, easy to check, bulge in cam cover on inlet cam side, and a solenoid on front drivers side of engine. Normally comes in at 4.5K. AFR runs quite rich up to 5000, then starts leaning out, actually that will explain the torque bulge. Could be MAF, injectors, or Fuel pressure. Install a FP gauge, and multi meter the MAF, if it goes up to 5V then you have run out of MAF range.

26th July 2005, 11:53 AM	#7 (permalink)
NewClearBomb GTR Register Member Join Date: Sep 2003 Location: Birmingham Posts: 74	cool, thanks I'll check the cam cover shortly. If I'm considering a power FC, do you know if I need a specific spec2 one to handle the NVCS?

26th July 2005, 11:58 AM	#8 (permalink)
NISFAN GTR Register Member Join Date: Oct 2003 Location: Herts Posts: 1,696	No, any R33 GTS-t PFC will have the control for NVCS. Spec 1's also had NVCS.

26th July 2005, 12:00 PM	#9 (permalink)
NewClearBomb GTR Register Member Join Date: Sep 2003 Location: Birmingham Posts: 74	cheers

26th July 2005, 12:20 PM	#10 (permalink)
skylineman GTR Register Member Join Date: May 2005 Location: northampton Posts: 174	hi, my gtst does the same thing, apparently its running out of fuel, mine dies off about 5500rpm then i get a kick at about 5900 till the red line. ive just ordered 550cc injectore, pump, PFC, and afm. give those ago

26th July 2005, 12:25 PM	#11 (permalink)
NewClearBomb GTR Register Member Join Date: Sep 2003 Location: Birmingham Posts: 74	which 550cc injectors have you gone for and where from? I'm not sure which engine management to go for yet, there's a few options available I'm looking at

26th July 2005, 12:42 PM	#12 (permalink)
skylineman GTR Register Member Join Date: May 2005 Location: northampton Posts: 174	to be honest not sure what there called they came with a 255lh pump. i was going to have a custom ecu and loom from jamsport but everyone thinks pfc works well, so ill try that