Link G4X JZX100 Plugin - VE numbers too high

Hi All,

Thanks for taking the time to read my post.

Currently working on a JZX100 with G4X plugin, customer supplied the injectors (came from a not well-know vendor, without boxes, in a zip lock bag), they are EV14 730cc PN = 0280158112. (see injector data below).

The issue I am having is that the injectors are flowing nowhere near 730cc/min of fuel. The VE table numbers are around 77 in the idle area (750rpm, 33kPA). The numbers are much more sensible and overall fuelling much better when using 450cc as the injector size, around 47% VE at idle and 105% peak torque.

I have checked the base fuel pressure at 42psi (reading on dial pressure gauge) and the FPR is working correctly at 1:1 differential pressure. Also have confirmed that by checking that fuel flow is stable across the RPM and load range, which it is, it does not drop off.

Has anyone had trouble with fake Bosch EV14s before? These injectors look very legit, but flow is nowhere near the declared injector size.

Using modelled fuel equations mode and have turned off all corrections, charge temp table is temporarily set to 0 as any ECT will obviously lean out the fuelling more.

It's worth noting that the idle quality is very good, and the engine is very responsive with an approximate VE table setup. The injectors do seem to be behaving linearly. I am road tuning the car so steady state in not an option at the minute.

I am wanting to advise the customer to buy a new set of injectors from a well known source, I don't think there is anything else that could be the issue. Does anyone else have any insight or final things I should review before condemning these injectors?

Thank you,

Craig

I havent tested that particular injector, but bosch quote a nominal qstat of 500g/min for that injector. Most vendors are then converting that to a flowrate using the density of N-Heptane. Bosch quote a conversion factor/density of 0.744 for gasoline flowrate from Qsat. 500/0.744 = 672cc/min.

The rest of your error is probably due to deadtime.

The data that I have for those injectors off of our test bench is that they flow 740cc/min at 3bar and 860cc/min at 4bar.

Thanks for confirming Stephen, good info but leaves me wondering if the supplied ones are not genuine.

Adam, thanks for your input, but there was a flow sheet provided at 684cc/min, that was the original flow size I entered in the injector setup, which give 77% VE at idle and 150% VE peak torque. Dead times have been entered as per the above values. Also, as you know, the dead time would not skew the entire VE table by 50%, but an injector which is flowing 2/3 of what it's claimed size could be causing that much error in the fuel mass calculation.

Is there anything else which could be causing this much error in the fuel calculation? MAP, ECT and IAT are calibrated and reading correctly.

Nominated engine displacement is correct?

Hi Michael,

Engine displacement is set correctly at 2500.

"Is there anything else which could be causing this much error in the fuel calculation? MAP, ECT and IAT are calibrated and reading correctly"

Anything that can effect the calculated fuel or air mass. Fuel press, air press, temps, fuel density, injector settings, other fuel trims etc.

Did you verify MAP calibration? I wouldnt just trust the mechanical fuel press gauge as well, many of those, especially the unvented liquid filled ones can be a long way off.

You can often set up a simple on car injector test without too much work to verify flow and deadtime. An example in this post on the link forum here: https://forums.linkecu.com/topic/24564-ve-at-max-value-but-i-need-more-fuel-suspect-bad-injectors/#findComment-134687 I explained the test and calculation earlier in that same post.

Some oil filled guages have an equaliser port you can open, probably not likely on an FPR guage but worth checking.

Thanks again for you input Adam, greatly appreciated.

Fuel pressure - gauge came off my personal car, is high quality and confirmed to be accurate, tested right before the JZX100 fuel rail also. Also validated by the 1:1 pressure relationship with vacuum/ boost.

Air pressure - MAP calibration confirmed, also validated by correct vacuum at idle and barometric pressure when engine not running.

Temps - also correct +/- 3-4 degrees as per sensor specs

Fuel Density - set correct for gasoline - 0.745g/cc

Injector settings - set according to the flow test and dead times for the Bosch PN 0280158112

Other Fuel trims - turned off and verified there are no trims active, verified in logs

With regards to the injector test, that will be my next port of call. Thank you very much for providing the link to the forum post. Will come back with my findings.