Injector Setup
Standard TVR Injector size & timing parameters
I have estimated the size of Rover v8 injectors at around 220 cc/min. I have used just over middle-of-the-road values for opening times based on stuff found in the wiki [add link!!]
Does anyone have more accurate info? They aren't flow matched from the factory and are quite old, so given the tolerances for them reported on Piston Heads it'll do for now.
Probable New Injectors
Got a good price for some nice 600cc/min injectors. They are supplied with opening and closing parameters and flow matched to 1%. They're monumentally huge for my engine, but this gave me an idea or two...
1. Phased injection
2. Ethanol based fuels (eg E85)
Q What is the smallest pulsewidth VEMS can sensibly do? I'd like a reasonable idle!!
- 200 usec. less than 700usec are hardly useful. However if your injectors in the set open with slightly different times, you might need to supply rich (eg. lambda=0.8) to one cyl to have the other burn at all (eg. lambda < 1.1).
- Good. The minimum pulse I'm likely to need with the big injectors is 1400 usec. Plenty of tolerance there!
I bought the 600cc/min injectors, and the flow matching really shows. They were also supplied with a datasheet of opening anc closing parameters. This helped me get VEMS set up very well. The engine runs so smoothly! The idle pulsewidth is 1.35ms, so I wasn't far off on my estimate...
Since many installers struggle with similar stuff, this would be a big help. Can you Dave upload some of this ? I suggest GenBoard/Manual/Config/InjectorOpening but this page is OK too.
- chart they provided (scanned, or URL)
- your cylinder size and calculation (roughly, just to give others an idea)
- the result (link to the config, and/or extract of the parameters: injocfuel, injopen, etc...)
I'm going to take it to a garage in a couple of weeks and see if it'll pass an emissions test. Results will be posted here.
Q Can you adjust the phasing of the injection events currently? (I suppose, as long as the finish point of injection is fixed same then I can simply use the "degrees before TDC" crank trigger parameter to fool it into doing what I want (confirmed) It would maybe be nice to coincide the injection pulse to the maximum lift on the valve.
Injector firing order & h Table setup
Firing order is 1-8-4-3-6-5-7-2.
Q: Does it actually matter if there's no camsync - will VEMS fire 2 injectors anyway if it can't find a camsync?
A: Yep this works fine without camsync, just set up alternate injector 7...0 and fill in the injector table with all outputs, 0x01 to 0x80
Note: VEMS will hapily fire single injectors sequentially without a camsync. The phase (i.e. if the valve is open or not) doesn't really matter if this is right or not at the moment. If it's configured as sequential then it stays sequential.
Wiring
Injector wiring was completed & tested last night. It looks better than the factory wiring!
Also took the time to hoover out the soil and powdered grot from engine. (Best not to ask...) It looks a whole lot cleaner now.
I removed the old engine wiring loom after the injectors were shown to work. This might be considered rash. Indeed it was, because it stopped the fuel pump and starter working! Even though they weren't supposed to be connected to that part of the loom!! It seems TVR re-used part of the Rangerover loom, including where the rangerover immobiliser plugged in. (This was bypassed for the TVR immobiliser) It took 3 hours in the cold and dark evening to trace the 2 all black wires I needed to reconnect as they were mixed in with grounds and all sorts.
Now the hazzard lights and heater have stopped working. I haven't even touched those systems! (Maybe a 2nd genboard to control the heater & stuff???)
I suppose the moral here is don't do anything like this if you need the car the next day!!
Low Z and High Z comments
Me:Low-Z injectors seem expensive and quite rare to me as they only seem to be used on Japanese cars. I'll be sticking with high Z ones as they're easy to get.
Answer: I was lost in the small but high powered 4 cyl turbo world, where we usually get aftermarket injectors (500CC/min and up), and good large injectors are always low-z.
Me: My other car is a modified Impreza STi RA with 550cc/min low-z injectors... The Griffith will survive with 400cc/min high impedance still can be fuelled to >350 bhp.
Answer: BTW, Feel free to join the IRC chat, see ChatViaIrc page
Trying to understand the injector model
I understand the need to accurately model opening and closing effects of injectors, and that they change with battery voltage.
There are 4 parameters to specify. As far as I understand they work as follows:
The first 2 seem reasonably easy:
injopen is the time it takes at 14v from applying voltage to the injectors to them STARTING to open.
battfac is a linear correction to injopen such that injopen is increased by battfac at 7v and reduced by battfac at 19v.
With the transient diode mod, I have these both set to zero.
The second pair are a little more interesting, since they deal with
injocfuel is the time it takes for an injector to open minus the time it takes to close at 7 volts.
injrampup_battfac is a scaling factor applied to injocfuel as battery volts rise from 7v to 19v.
Q1 How exactly does injrampup_battfac affect injocfuel? Is it a multiply scaling or an addition?
Q2 Am I correct with how injocfuel works?
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