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Injector test results


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To satisfy my curiosity and give myself decent injector data to tune with, I've hooked up a test bench and run the two sets of injectors I have:

  • Bosch 0280150803 (typically from a Porsche 944 Turbo), which I am going to use with resistors (ECU they will be used with is saturated only) so any deadtime data around is meaningless
  • Bosch 0280150363, which is a very low impedance (0.7 ohm) performance injector which I understand was pretty popular in the past

I ran the advanced injector test at various ms, picking a number of events and hz that are (I think) about 50% duty cycle and roughly a minute, then made a spreadsheet. You can work out the deadtime if you know the number of ms requested and the fuel delivered within the injectors linear range using the INTERCEPT function, and the SLOPE function gives the number of ms per fuel delivered so can be used to work out flow. The deviation from this theoretical calculation is the short pulse adder. I only did this at 12v (actually more like 11.7v) and base fuel pressure - I don't have a particularly reliable means of varying either.

The results look like you'd expect (particularly if you extract the Motec M1 data and do the same analysis on that - results are fairly similar) - the injectors are linear down towards 2 ms test, then show non-linearity. The deadtime with resistors on the 803 injectors with saturated driver is longer than with peak and hold. However, there are two things I can't figure out:

1) Both sets of injectors show some crazy non-linearity at a certain point - in particular both had a point where the amount of fuel delivered went up when I stepped down to a shorter pulse width. Is this normal? It was slightly unexpected as Motec's data didn't show this. Note - the 363 did it at 1.2ms test and the 803 only did it when run as saturated as I didn't go low enough in P&H (I stopped at 1.3ms as that's really low for an injector of that size bearing in mind it includes deadtime). I guess I am not worried as in each case as both are where requested pw is below 1ms.

2) Both injectors flowed less than expected, and I am not sure what to use as the flow in the ECU for modelled fuel. The 803 injectors flowed slightly less (approx 5%) than Bosch spec / Motec data, which would be mostly explained if pressure is actually 250kpa (what the regulator is supposed to be) rather than the 270kpa a cheap ebay sensor measured (I will use proper sensors when each car is done). The 363 injectors were >10% too low (~8% if the pressure sensor is inaccurate or incorrectly calibrated), and in addition to Bosch data and Motec data I had them measured and cleaned a number of years ago so know they should be a bit higher. I guess I can think of a couple of reasons - looking for thoughts:

  • weighing the fuel delivered and dividing by 0.745 is not accurate 
  • I used 4 amp peak, 1 amp hold and this somehow wasn't enough and limited flow 
  • the Advanced Injector Test is somehow not a good measure for flow 
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I ran low impedance injectors with ballast packs which you are intending to do


i would advise against it and move to big impedance injectors as I have 


car runs much better and I have better control of fuelling and idle is much better and have even managed 33mpg on a run compared to a dismal 24 mpg 

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Thanks. I have thought about changing but can't really justify it. The injectors are clean, they aren't particularly high flow or difficult to drive, my spreadsheet shows they deliver fuel linearly in the planned range, and I have the data to make them work well. The spray shape (narrow cone) is suited to the engine too, as its only a 2 valve. 

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CamB as you know I've done this testing also. I weighed the fuel as it was easier to do the testing. Just have to make sure you spray into a big container with a larger exhaust filter to stop spray back. Next time I do testing I will measure the weight of the fuel in the test rig before and after testing not the amount sprayed.

To measure max Cc I used a aux output. 

Also there can be a big difference in SPAT of several injectors. I'm running wideband in each turbo runner and the accuracy and repeatability of the injector in the lower IDC is just crazy. Even using ID objectors.

Even with all the injector data supplied by ID I still needed to tweak there dead times. Reason being running large injectors in non linear range at idle and low loads. 

Get yourself an external power supply to run just the ECU and injectors. I think mine is a 30 amp only because I wanted to run a pump as well.

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20 hours ago, CamB said:

1) Both sets of injectors show some crazy non-linearity at a certain point - in particular both had a point where the amount of fuel delivered went up when I stepped down to a shorter pulse width. Is this normal?

Yes this is normal.  I have come across it before tuning idle on cars with large injectors sometimes you lower the fuel table number and it suddenly gets richer.

A pic from google which shows this particular injector flows more at 0.3ms eff than at 0.4ms:


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Thanks @Adamw and @Ducie54. I actually think I'm fairly happy - I know my test wasn't perfect and its not ideal that the flow might be different, but that is the flow I experienced... My key goal was getting a deadtime for the injectors with resistors and confirming they sprayed nicely when driven like that.

So this topic has any relevance, I've attached a spreadsheet if anyone is interested. It has a blank worksheet and one I filled in (and modified) for the 803 injectors, plus the Motec data I compared it against.

Injector test spreadsheet - Link forum.xlsx

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