Does This Sound Right.

[kjb_r33]

Rb20 with a r34 turbo, FMIC, HKS pod, adjustable cam gears set at +3 inlet, -5 exhaust, split dump, about a 3 1/2 inch front pipe to cat and a 3" cat back, running 10psi. I would have thought with those mods that the standard fuel system could cope, but its leaning out on full boost. I have got myself one of Newkleer's consult units and its telling me im hitting 100% duty cycle on the injectors. Air flow meter is no where near the 5.1 volts for R&R so what else could be causing my injectors to hit max duty cycle?

Seems im about to upgrade rail pressure, although i beleive the rise in flow is not lineal with pressure, meaning a 100% rise in pressure only gains around 40% rise in flow through the injectors.

So what would be my next step?

[paulr33]

old tired pump

[kjb_r33]

old tired pump

Pump is brand new

[mad082]

has the ecu been remapped? it may have been set to dump in as much fuel as possible. or possibly o2 sensor is cactus.

[paulr33]

plot fuel press from the regulator on a dyno run

with afrs

should isolate the gremlin

[kjb_r33]

O2 sensor is also brand new. I had it on a dyno late last week, it was running very lean, had to stop the run, but at that time i didnt know it was because the injectors were maxed out.

[DFAULT]

this aint relevant but would like to know more about your cam gear adjustments

i got the best results with ex: -3

though all the inlet: degrees made me lose power

just would like to know if you tried other settings, is that your best setting?

[Al]

What power are you making at 10psi?

If it is anywhere over 200rwkw, then yes you need to replace your injectors with 550cc items.

What fuel pump did you buy?

[kjb_r33]

What power are you making at 10psi?

If it is anywhere over 200rwkw, then yes you need to replace your injectors with 550cc items.

What fuel pump did you buy?

Have not had it near a dyno that has shootout mode, i have access to a dynodynamics dyno but its the raw bones, no shootout mode and therefore no adjustments for ambent air temp and so on. Last time i had it on that dyno it said 140 kw (and i think thats conservative given the dyno) but ive since added the split dump and cam gears . I seriously doubt its anywhere near 200 kw though with what i have done. Just bought a sard reg, on the hunt for an 040 pump.

[kjb_r33]

this aint relevant but would like to know more about your cam gear adjustments

i got the best results with ex: -3

though all the inlet: degrees made me lose power

just would like to know if you tried other settings, is that your best setting?

Hadnt tried other settings simply because the settings i had used seemed to work from other peoples experiences. I was going to move either way from there but never got the chance because of my leaning out.

Seriosly though, before i got it on the dyno and knew the leaning problem, going by seat of the pants, its felt HEAPS better and the dyno run i did do showed BIG improvements mid range, just started leaning out too much on top end to carry on..

Edited September 24, 2006 by kjb_r33

[Abo Bob]

So what pump is in there now? HAve you checked your base fuel pressure?

[kjb_r33]

So what pump is in there now? HAve you checked your base fuel pressure?

The pump in there is an aftermarket replacement for the standard pump, had to buy it when i bought the car as it wasnt running. I have just bought a sard rising rate regulator (not yet installed) but i will check base pressures as soon as i get my ECU back in it. Its off having a socket mounted so i can replace the eprom. I actually have another ECU at home so i'll check fuel pressures when i get home.

Ken

OK, just checked fuel pressures, about what they should be, Sitting on 230-250 kpa at idle, moving up just to around 300 as revs come up. Flow and pressure increased as the pump switched from 8.5 volts to battery voltage at the off idle position. Crimp return line and pressure almost hit the 350kpa mark. Maybe im just getting a higher output than i thought and the standard system cant cope. We'll see if the sard helps when i get it.

Edited September 25, 2006 by kjb_r33

[kjb_r33]

Fitted an 040 this afternoon, damn sard hasnt showed up yet. Just changing the pump seemed to make some improvement, but im still hitting max duty cycle with my injectors. Hopefully the reg will fix it.

At what power do the standard fuel system, (pump and injectors) normally max out?

Edited September 29, 2006 by kjb_r33

[cameron]

What size are the factory RB20 inj?

[Cubes]

My stock injectors didn't get me far.

I managed 176rwkw and they were hitting 92%.

A friend is making 182 or 187rwkw (I forget exactly) and hitting 100%. Both duty cycles were a 12:1 AFR.

As I run 2 fuel pumps I assumed the low volts being seen at the fuel pumps were causing the low power reading and high duty cycle. Running a direct feed to the fuel pumps saw volts jump to exactly what the alt throws out ~13.8v. The car did run slightly richer so no doubt I would have got a little more out of the injectors but I gave up and threw a set of larger injectors in.

As an interesting note also a friend ran up his VLT on the same dyno I run on and made 187rwkw. His stock injectors were also maxing out and afr's began getting leaner than 12:1 as it approached redline. VLT's run the same sized 260cc injectors as the RB20DET's.

EDIT: How long since you changed your fuel filter?

[kjb_r33]

i beleive it was changed just before i bought the car, about 4 months ago, but i will change it today anyway, just to eliminate that as a cause

[Adriano]

Unfortunately none of this explaines why duty is at 100%, as the duty is only dependant on the programming and the airflow meter. O2 sensor feedback turnes off under load. Either the computer is remapped, or possibly the coolant temp sensor is stuffed, and the computer is giving it cold enrichment. Also your fuel pump is nowhere big enough, if you block the return line, pressure should go up to about 600kpa.

[kjb_r33]

Unfortunately none of this explaines why duty is at 100%, as the duty is only dependant on the programming and the airflow meter. O2 sensor feedback turnes off under load. Either the computer is remapped, or possibly the coolant temp sensor is stuffed, and the computer is giving it cold enrichment. Also your fuel pump is nowhere big enough, if you block the return line, pressure should go up to about 600kpa.

The 100% has been reached using both the standard eprom, and now a reprogrammed chip. O2 feedback (closed loop) does turn off underload, but any changes made to the original mapping will be a broad change, across the WHOLE of the fuel map, ie 10% richer or leaner. I have now put a 040 bosch pump in and also changed the filter this morning, checking flow and pressure before and after the filter change, no real change to pressure but a slight increase in flow (.2 liter per minute), Car does not seem to be leaning out as much but im still waiting for my sard Rising rate reg to show up, was hoping it would be here last week.

[kjb_r33]

Fitted sard yesterday, went into work this morning and did a quick dyno run. Bumped up pressures and ended up acheiving AF's of 11.5:1, at .8 bar. Dyno is a dyno dynamics, but a very basic one. Has no shootout mode and therefore no corrections. Last time i had the car on it it reached 140 rwkw's (ramping from 80K's in 4th gear). This time 150, but i have changed the cam gears, fuel pump and reg. I think the readings are conservative to what it would be in shootout mode though, as a comparison a VT commodore 3.8l hits about 65-70 rwkw on this dyno. Power and torque curves look sweet though.

I realise that i have to replace injectors ASAP, am working on it.

Green one is before cam gears, blue one today. (date is wrong on computer, dyno gets used probably once every 3 months).