In vehicle injector dead times

I'm currently working on a BMW M50 Turbo with Seimans Deka 630cc injectors on an ECU Master Classic. With their injector wizard settings, it runs rough with very little control, small changes making massive variations in Lambda values.

I did a little digging online to find injector dead times and came across a technique of using a scope to check the amp draw and voltage of the injector, with this it gives a dead time of nearly twice the injector wizard values. Obviously, a re-tune is needed from this. With some quick, rough changes, I got it back to idling at lambda, but it still sounded rough and has very little control at idle

Has anyone got any other methods of finding the rough dead times with the injectors running in a car?

I always liked the methods suggested by megasquirt. Where you can change from injecting once per cycle (sequential injection) to once per rev (so two injections per cycle. If you flip back and forth between these modes an incorrect deadtime shows up as a Lambda change. One some ECUs this is Sequential vs. Wasted Spark mode. I've only done it a couple of times, but it really works when you don't have any data to work with.

Hey Chris,

One thing to consider is that the injector deadtime will have more effect at idle, as it will account for a bigger percentage of the "total" injection time (deadtime + actual injection). So testing at idle is ideal.

I think I read the following method somewhere, which I tried and I think it was proper. You populate your deadtime table roughly in the ballpark. Make sure you have a stable voltage to your ECU with the engine running (14v). Then you match you lambda to your target with your VE table (lets assume lambda 1.0). You then change your lambda target to a richer one, by a considerate amount (let's say .90 or .85). If the lambda doesn't track, your deadtime isn't set properly. Adjust your target back to lambda 1.0, change your deadtime (in the 14v cell), the actual lambda will change, reajust it to match your target with the VE table. Target back a richer lambda, check if it tracks, then repeat. When it does, unplug the alternator and increase electrical load by enabling coolant fans or anything that could do so to achieve 12V, then repeat the process for that cell. You'll need to extrapolate for some of the cells you can't access, keeping in mind that the relation deadtime vs voltage is non-linear.

Hopefully someone will chime in and confirm or debunk this method!