Injection phasing is a key element to getting the required fuel into the cylinder atomised correctly ands i hoped we would drift naturally onto that but it seems Karl cant sleep and has saved me the trouble now anyway...


Roflol.. like i said earlier it was a quick few lines whilst a car warms up for mapping, i wasnt wasting time putting any hard calculated figures in at almost 11pm, i wanted it to be very simple for people to understand the theory, nothing more, nothing less... I considered describing it accurately as time between intake valve closing and then opening again but decided that 95% of peeps would simply think i worded it wong anyway, so i left it oversimplistic with exagerated numbers....

Whats this anyway? Tuner wars? Have i a cap in my ass yet?

I will however tell you where my original numbers came from in my head, they are in fact the correct total injector ontime available figures for our antiquated Cosworth speed density management systems. Im sure it will occur to you where the ontime figures effectively "double up" once you think about it, but it wasnt remotely relevant to this topic at all...

I wasnt saying 600bhp at 9000rpm required a bigger injector than 600bhp at 6000rpm i was saying that we are running higher power now at higher revs and requiring larger injectors...

As for RPM having "No Significant part in injector choice" im afraid i disagree Karl. A simple example of why i disagree is this: At 8000 RPM the intake valve is opening and closing at 66 times a sec. And is only open for an average of 6ms. At this cyclic rate the transient time to complete the delivery of fuel, from injector to cylinder, is critical and as a result, we rely heavily on pre valve event phasing to deliver the fuel to the valve before it opens at all. the one thing that will never ever change no matter how hard we rev the engine is the fact that an average peak and hold injector operating on a saturated (or otherwise) circuit driver typically has a reaction time of 2 milliseconds while a peak and hold injector typically responds in a much better 1.5 ms dont forget it has to close again too so please double this figure.... It also has whats known as a dead time of 0.6ms on average. Couple these facts to the obvious injector duration issue with high speed switching and the technical need to start limiting inj duty to 70% instead of the 85% that was safe at lower engine speeds and i stand by my reasoning that for higher horsepower and higher RPM we should be using a bigger injector for safety.

Anyway.. its 03:30am and ive no time or inclination to start any technical chat this morning as i need to go home to sleep, but i thought id best quickly redress this post since it seems to be dig at Stu week and ive no "defensive" time available during a busy Saturday.. lol