Done!
Now, back to your original post!
nimblemotors wrote:I'm currently finishing up conversion of the ignition to a distributerless coil-on-plug setup,
which I will show when its finished. (well ok, here is a pic.. :)
Cool! :-)
(BTW, the megasquirt is way overpriced for what it is, I'm using my $10 micro)
Agreed! MS2 chips are around 8usd or so, but they chose the variant poorly and the main boards are both badly designed and a poor fit for the needs of the majority IMO. The FreeEMS MCU/CPU is around 15usd for the chip, for what it's worth.
But now I'm thinking of replacing the worn out carb with manual choke with an EFI system,
and I'm thinking of how simple can I make it? As a TLB, it isn't like a car, the engine is usually always loaded,
running the hydraulic pump and/or moving the vehicle.
The answer is "very". Especially on a single fixed application. A lot of the complexity and sophistication in FreeEMS is centered around working properly for nearly anything.
It takes a long time to warm up before it runs properly, using a manual choke seems quite primitive.
I'm fond of manual chokes on cars, though you do need to understand the machine, and it seems a poor fit for a machine that doesn't have a driver focussing on it constantly. A temperature sensor and a simple lookup table should perform better in every way :-)
So how simple can I get to replace the carb? A TBI for sure, but can I just use a wide-band o2 sensor, and a MAF as inputs, or do I also need engine temp and air temp, etc. how simple can I make it?
That depends upon how fuel efficient you want it to be, and how maintenance friendly. Running richer than you'd like will solve some of the issues that you'll face, but foul plugs and wash the bores down.
The wideband is only required for setup, once tuned you can take that and put it in a shelf or use it in another project. On boosted cars it's nice to keep a wideband on the dash, but if you go a little lean for a second it's very bad under those circumstances. On NA stuff, though, it's purely for show/interest. So you don't need the wideband long term. You should either fit a bung near the engine and put a plug in it later, or make a tail pipe fitting to stop clean air from screwing your readings due to reversion. In fact, re the wide band, the only reason you connect it to the ECU itself in terms of tuning usage is close correlation of the O2 data with the other parameters. For tuning it as is, you can likely just watch it and tweak values around until you're happy.
MAF would keep things simple, that's for sure, and likely eliminate or include the air temp sensor. In terms of MAF tuning, you just figure out the calibration of the device, then supply a desired lambda table and it should "just work".
Air temp you could add anyway to change ignition timing to be more optimal for varying conditions. But you don't need it if you use MAF. If you use MAP however, without running too rich, it's essential. Especially if you live in a place with proper seasons.
You're definitely going to want engine temperature. The fuel demand in a cold engine can be double, or triple or more. The only way you could dodge this, is, you guessed it, with a "choke" attached to a rich/lean pot :-) Which I think you said that you didn't like ;-)
In terms of code, it can be pretty straight forward too. You can do without any sort of transient enrichment due to the steady state nature of it. Worst case is a slight stumble if you change the throttle suddenly.
In terms of hardware, you can do without a warm up valve for airflow, but you'll either have to run a high idle, or manually keep it alive when cold, or pull timing out and make it inefficient at idle when warmed up. Idle can be set with the stopper on the throttle, though, other than that.
I hope that helps :-)
Fred.
