Glad I posted the original query, it's turned into quite the interesting thread, thanks all for the contribution.
Small aside, why does the RBTB need different, and I assume larger injectors or are they just a faster duty cycle? I understood they provided more control over the air entering each cylinder and hence better combustion equaling increased power. Are they actually allowing more air and hence the need for more fuel thus bigger injectors?
Can I see no three seven coming to your garage Mark ,,,,mince pies will be in soon
Unlikely, there's more chance of me going back to just the one. Hopefully it won't come to that, but it's still up in the air. The thread is just curiosity.
I believe you Mark ,,,good post ,,had flue jab today ,,think he served his time on a whaling ship ,,that's why I'm still up late ,,you back at work yet or do they let you work from home
keep well both
Regarding the injector sizes: it's really about matching the duty cycle to the use the full resolution of the map. A larger injector will mean mean each step of adjustment is bigger, and this can make mapping less refined. Conversely a smaller injector running at over 80% duty cycle may struggle to get fuel in when it's most needed. IIRC the blue injectors are pretty much max'd out on the standard R400, so more head room is required for even small increases of power.
Yes, the R400D can run over 90% duty cycle on the stock blue injectors with the plenum. Looking at my logs at just before the redline cutoff at 7,800 RPM I'm running 81% with 11% altitude adjustment (equates to 91% at sea level) and 0.85 lambda.
James, your ECU is unlocked? If I recall from our work with John, I seem to remember it is.
Can I suggest the ins and outs of injectors etc would make a fascinating Low Flying article.
Hi Mark, yes I have an unlocked 9A4 ECU I bought from SBD directly to load a TPS based alpha-N map into as opposed to the MAP sensor based map that Caterham uses, combined with a barometric sensor from SBD (too limited in using the pre-startup MAP pressure value for altitude, with the assumption altitude doesn't vary a lot during a journey) and a wideband lambda sensor system from Innovative Motorsports.
For me, the lack of direct altitude adjustment in the Caterham mapping is a big problem. It is easy to add, a matter of a relatively cheap sensor and a couple of tables to be configured. Within a tank of fuel from my house I can be on paved roads below 1,000m and above 2,200m, so a single blat without stopping can see the fueling requirements change from -11% to -24% compared to sea level and then again to -8% at the track in Edmonton I go to that is at 700m attitude.
I've never thought about doing a Low Flying article, perhaps something to think about putting together over the upcoming winter.
It would be very interesting to have more base info on this. As one who grew up putting Cooper S engines in woody mini estates and building super quick Hillman imps and Mk 1 Escort Mexico's before gaining company cars and not dabbling any more until I got my 1st Caterham.
I would really like a bit more baseline information of how this works just for information and understanding.