fast951

Patrick, as I have mentioned it to you a while back. Vitesse software is semi-batch (some call it semi-sequential as it fires half as often, not half the injectors at a time).
As mentioned here, large injectors do not do well with the stock batch mode. With Vitesse semi-batch you get a clean idle with large injectors such as 85#. FYI TT was the driving force behind this feature.

333pg333

No probs there John. I just wanted to clarify the terminology.

gt37vgt

AAAAh! whitchcraft that john is to clever i'm outa here

fast951

Whitchcraft?? That's it! Thank you for the valuable information...

RPHARRIS

For a while I experimented with Batch mode, 2 squirts per revolution (4 squirts per cycle). I definitely noticed improved throttle response in the mid range. My theory is that "digitizing" the injection with a bunch of small squirts reduces wall wetting because the layer of fuel is much thinner at any given time, hence much more rapid evaporation. The downside is that even with stock injectors, the idle was HORRIBLE, and I had to keep the boost really low to manage the duty cycle. At high RPMs, too much time was being spent opening and closing the injectors.

RPHARRIS

With my new, 55lb low impedance injectors, my hope is that the opening time will be substantially lower. We'll see what works.

Kool

So sequentail fuel injection is only a viable solution for cars with large injectors? Would there be any other reason to have a sequential injection set up with a stand alone EMS?

theedge

Individual cylinder trim is another reason. You can run full sequential with any size injectors, you dont have to have big ones as you seem to imply in your post there

Kool

What if you like "big ones"?

You would need multiple O2 sensers or temp sensors on each exhaust port in order to tune each individual cylinder No?

I am just trying to understand the advantages to sequential FI.

theedge

Ideally multiple sensors yes, or some known difference.

The biggest benefit is idling with big injectors.

Chris White

A full sequential set up allows for more dynamic range from the injector. Why is this, you might ask?
In the batch fired system (typical for stock and stand alones with out a cam sensor) the injector has to fire twice for each 4 stroke set of events (2 engine revolutions). In a fully sequential system it only fires once. Due to the minimum injector turn on limitations (fuel injects have a minimum duration signal needed to get the injector to flow, its based on the physical limitation of the injector coil to oven the valve). SO all things being equal (injector size and fuel pressure) the full sequential system will inject half as much fuel when running on the minimum possible turn on time. This allows you to run larger injectors and still have a good idle mixture. That will also allow you to have larger injector to support higher boost. Typically a 72 lb injector at a “normal” fuel pressure will be right on the minimum injector turn on time at idle (in a 2.5 engine) and it will reach 90% plus duty cycle at 1.5 bar boost. Same set up with a full sequential and you can either go to a larger injector or turn the fuel pressure up to lower the max duty cycle.

Clear enough?

Kool

Got it thanks Chris.

fast951

When running large injectors, idle quality is "easier" to control with a sequential system. However, even if running a sequential system, with the increase in injector size there is a increase in the "dead time". Once the dead time exceeds a certain value idle goes down the drain as well. This is one of the reasons people requiring lots of fuel opt for a staged injection (a second set of injectors kicking in under load).
A full batch system (stock Motronic) is not happy with large injectors. With the conversion of the stock system to operate as semi-batch (when needed), it can run 95# injectors with a crisp idle.

Most injectors are rated and run best at 3bar fuel pressure. Using a higher pressure to compensate for the size of the injectors is not good. Running lower pressure than what the injectors are rated at is not good either.

Kool

So how does Electromotive fair with sequential injection?

Chris White

Its been working fine for me!
One day I will set up a staged system too - just for fun!