Injector sizes.

**Steve Webb** · 30-11-17, 14:01

As you've probably seen, I've been questioning the abilitys of the standard Q4 injectors and looking at what they can and cannot do. On my travels to find out about them I've come across some interesting resources.

This one if from the Megasquirt website, interesting calculators to plug some numbers into.

Injectors theory and calculators All the good stuff is in the top half of the page.

**jNk** · 30-11-17, 22:23

Those calculations also supports the fact that ~250bhp is the limit of our injectors, the question is what should we buy if we aim over that bhp ?

One of the local tuner (who wrote several IAW ecu as well as some rally car engine management systems) over here said the Siemens Dekas are average at best and there are way better injectors for our cars out there (with higher price tag I assume)

**Steve Webb** · 02-12-17, 18:03

It seems that Bosch seem to have a resonable reputation around the various forums, but I'd be interested to hear what other people have to say.

Personally I'm going to be aiming for 300bhp, should be enough to keep things interesting really.

**jNk** · 03-12-17, 13:19

I've also found a nice little page regarding injector size / fuel flow / worksheet

The tuner recommended Bosch as well so I'll try to find a straight upgrade to our cars without messing around with the fuel rail or anything else.

**Steve Webb** · 04-12-17, 22:48

I think the calculations on that page are a little bit off, if you put in the standard Q4 details, it comes back recommending at least 377cc injectors at 80% duty cycle. Surely Alfa allowed a bit more injector overhead than that???