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How to configure bigger injectors in a VE map?

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Hi there!

I have this car which ran on 400cc injectors. Those did 80%DC at 5200rpm thus needed bigger injectors. Someone came up with 'oem GTR 550CC' injectors. No information came along with them. Even posted on FB for more information.

So they are in the car now(350Z) which has a haltech platinum plugin. The fuel pressure is higher that what they are rated at so with some calculation i entered the approximation of 660cc into the haltech. got some dead time's form the fb post which i entered into the haltech. Now, the car started(not smooth but thats due to the crank enrich is in injector ms). It was richer then what it was a idle and adjusted the flow so that if was the same at idle as with the other injectors. this seemed all good. But when i drove the car it became pretty lean. in the regions of 1.12 and leaner. idle was ok, also reving it higher stationair it was ok.

I had the impression that on a VE table entering the (correct) data in the ecu no changes are needed on the fuel map. Do you guy's have any pointers? probably the dead time's or the flow rate are off. I did try to play with these a bit but that gave me a richer idle and still lean in cruise.

Really thanks in advance!

Kind regards,


Did you use the square root law for fuel pressure increase.

Discounting latency differences orifice flow increase factor is equal to the square root of the new pressure on rated pressure, it is not linear.

If the latency values you have are correct and you have adjusted the flow properly the other problem could be that the data for the original injectors wasn't right and those errors are reflected in the VE map so it is a combination of engine airflow characteristics and errors in injectors data.

Hi there!

I did not do a square root equation. just a percent based one. The thing about the older injectors could make sense. These where really weird ones with strange flowrate/deadtimes. In my opinion this could only be fixed with a fuel remap.

Thanks for this input.



You also need to remember that the higher the pressure the bigger the latency numbers are.

Hi there!

Thanks for the input. I took this in consideration while entering the deadtimes. We found out what probably is causing this the lean situation: the original injectors where configured in the haltech as 400cc at 3.5 bar while they where rated 420cc at 2.25 bar. Effectively they outputted something like 520cc. So the tune is quite off.

Kind regards,


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