I've been looking into K Series injector flow rates.
I've been trying to help someone who is fitting TF135 camshafts and an aluminium plenum with 52mm TB to a Freelander 1.8. The only ECU can find that works happily with the other Freelander systems is from a Rover 25, so he wants to copy the fuelling and ignition tables from a TD135 map into the Rover 25 map to correct it. However, there's a problem with injector scaling. If he uses the black injectors that the map was written for, they won't flow enough to be safe at the top end. If he uses the blue VVC injectors, the map will be scaled wrongly as the injector flow rate will not match.
So I needed to look into exactly how he could update the injector scaling in the map. There was a table which I had previously identified as loosely "injector flow rate compensated for battery voltage (pump performance)" but I hadn't been able to consistently match the numbers in the table with actual injector flow rates in any sensible units.
The VVC/TF135 injectors are widely quoted on the internet as being 191.8 or 192 cc/min.
This has always made me feel uneasy because if you work out the peak BHP that they can support, they shouldn't be capable of delivering the 160bhp of the VVC engine.
So today I went back to the Bosch data sheets to get the original specifications for the injectors. These are quoted in g/min, based on a test fluid of n-heptane at 3 bar. From these I used the density of heptane 0.684 g/cc to convert to cc/min using heptane. The injectors tend to flow a bit better using petrol than heptane (but heptane is easy to standardise for tests where petrol formulations vary) so it is generally recommended to multiply the mass flow rates by 1.035 to convert to petrol. I then also converted the petrol mass flow rates to cc/min based on a representative density of 0.750 g/cc.
As you can see, I came up with a rather different number of 207 cc/min at 3 bar using petrol for the VVC injector, rather than the usually quoted 192 cc/min.
This makes a lot more sense.
As a final check, I then compared these numbers to the flow rates found in the ECU tables:
As you can see, they are an almost perfect match (if I assume that the ECU tables are in units of 0.1 g/min - the ECU only works in whole numbers).
These ECU tables are always consistent across engines with the same injectors and I'm now confident they are flow rates in g/min, and that I can easily rescale a map to allow for different injectors by copying in the appropriate table.
And I'm fairly sure that the value of 192 cc/min is a miscalculation that has since been propagated widely around the internet - unless someone can point out a mistake in my logic?