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DIY Fuel injection thread.


yoeddynz

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Id run the factory ignition to the trigger of a new relay maybe and run new feeds probably, just to be sure? How much do those things draw anyway? And any of it setup as wasted spark? And what sort of dwell time? Once you know that you can figure out how many will be 'on' at one time and calculate if its fine via 1 lead or not...

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6cyl full sequential with 3ms dwell means that at 3,333.33 RPM multiples will be on at the same time. So at worst case of say up to 10krpm, youll have 3 of them on at one time.

Now just gotta see how much current they draw and what you can draw through the 18awg, which is probably 20A without any real issue? So if the coils draw less than 7A each, youre ok at a guess

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  • 2 weeks later...
A while back I calibrated my tacho and speedo with some custom values so they are more accurate.
 
Lately though I've been trying to get a feel for how economically the car runs at various speeds.
So I've had to to take some datalogs, and then do some maths on the logs which is time consuming and it's hard to relate back to what I was doing at the time.
 
So I've come up with a better idea, I'm going to make it so that my tacho only activates when in 6th gear.
but then the sweep of the needle will be based on a table that has Effective Injector Pulsewidth and engine RPM as the axes.
 
The values populating the table will represent what sort of economy you're getting.
 
So when you're driving along if the needle is showing 2k you're doing well but if it's pinned at 8k you are doing it wrong haha.
 
When I get a new wideband and controller I'll switch to modelled fuel equation, which natively gives fuel consumption info which makes everything easier. So I could make this same thing work in all gears instead of just 6th.
It would be cool if I could switch between tacho or economy gauge, either with a switch or with some logic/criteria.
But I think I'm stuck with one or the other. Maybe I could permenantly repurpose the oil pressure gauge needle to fuel economy instead.
And then wire in an oil pressure light, I've never liked the idea of having to look at a gauge to see low oil pressure rather than having a bright light blaring in your face to tell you there's a major problem.

I've got a blue shift light mounted in top right corner of my dash cluster which works well. I've bought a second one that's red that I'm going to mount on the other side, as a general purpose "Turn this shit off somethings fucked" light that could have a few different criteria making it work.
 
At the last superlap event, Barry manon lost a very fancy engine due to oil pressure issues.
Looking back through his footage he said that his oil pressure gauge showed low oil pressure for half a lap but the oil pressure light never came on because the threshold was set too low. (something like 4psi) and no one ever looks at a gauge while you're going 10/10ths.

If he had better warning it might have saved him an engine.
It could be a good plan to have a warning light operated by a table maybe relating to engine rpm and oil temp, so you can run the light at say 20% below the threshold of what you'd expect oil pressure to be in every situation.
 
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You could use 2 outputs one for your tacho and one for your economy figures. Wire tacho input to common on a switch and each output to no / nc on switch. Then when toggled itll switch either output to your tacho display on dash.

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And for oil pressure warning I normally do a lamp in conjunction with a loud as pizo buzzer. Lamps are good but when on track your looking where your going not at dash. So an audible alarm seems to work best. Just have an argument so it dosent come on when motor not running as it gets annoying when turning ignition on. Say alarm inactivate below 100 rpm. If you drive it directly from link output youll need a resistor across the alarm to pull the output down as the transistor will leak and youll have an annoying hum going on.

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Myself and Sentra Dave spent some time getting some data on ID1000s tonight.

 

This was interesting because it's the first time I've measured some injectors which actually do come with some reliable deadtime info.

 

For better or worse my results were very similar to the provided figures, we were running a slightly different pressure compared to listed data though.

 

Unfortunately we found that the Link G4 does not appear to have a minimum pulsewdith setting, or a short pulsewidth adder table, so some of the extra lengths we went to by running lots of tests could have perhaps been streamlined a bit. (Sorry to chew up your afternoon Dave...)

It was still interesting though and good to rule out the injector behaviour as contributing to idle issues etc.
Also the injector behaviour was pretty good anyway.

They were clocking in at 938cc @ 39psi / 13.6 volts.

Nice and linear down to about 2-2.2ms but below that you really need the PW adder table as there's quite an agressive "knee" and then it drops off pretty quickly.

 

kkxxgytp.pts.jpg


This gives me some confidence that my method is pretty good, and it will work well in other cases when injectors are being used where accurate deadtime information just simply isnt available.

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My pumps can/often change sound as if pumping quicker or slower. Like one good example is when the car is idling unusually low I can hear the pumps sort of doing a struggling low sound.  I figure the voltage is really low at that point and the pumps just slow down.

 

This will effect the output pressure yeah? So then the engine could start to stumble/go slightly lean due to less pressure. Or would there always be enough pressure because even with pump cycling at a slower speed it is still possibly putting out more than what the regulator needs to regulate something down from?

 

Maybe I fit an inline fuel pressure gauge and watch. Ahh hassle.

 

I don't know how much it could effect my tables and fuel out put if at all once just driving along. Even if it did my EGO correct would probably account for and level out any slight changes?

 

Hmmm.

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Low fuel pressure from low voltage definitely changes things.

 

That's where I start to see the deadtimes being way different to factory figures, because in a real life scenario when your injectors have 8v so does your fuel pump so the pressure drops.

Below about 10volts on my car, and you start seeing fuel pressure taper off.

 

Wideband fuel trim cant really do much at idle sort of speed, I dont particularly trust my widebands readings at idle anyway.
Because the motor will be running visibily rich out of the exhaust but it'll show me everything is dandy at the wideband. Maybe I've got a small air leak somewhere.

 

My new wideband controller should hopefully be here tomorrow, woohoo. Feels like flying blind having gone a few weeks without one when I want to tinker with stuff haha.

Looking forward to having a bit of a tinker with injection timing at cruise conditions. Also now that my deadtimes are good. Seeing if my outer injectors now do anything useful below ~5500rpm.

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$35 fuel preasure sensor wired into the ECU and then you can check/log to your hearts content :-) fitted one in mine but more for over pressure, not low pressure. China 044 pumps way too much for my little 60hp KP haha.

Makes all sorts of weird noises though, always sounds like its cavitating or something but seems weird. Have been thinking of removing the pre pump filter to see if that changes anything... Might now flow enough or something? Fuel pressure is sweet though so im not too worried

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Or maybe some kind of voltage regulator at the pump so it will always see 12 volts and no more or something, so keeping it consistent no matter what the alternator is putting out?

 

I dont think it really matters, because the fuel pressure reg will hold at a particular pressure so you never get it running too high.

As Speeno says some Nissans etc run a resistor in the fuel pump circuit to run the pump at half voltage when under low load.

 

My fuel pump whines like crazy when I had the car set to ~80psi, it was the restriction to flow that cause the pump to load up.

Now running at 60psi and it's much happier. 

If I ran my engine at ~40psi I'd probably see consistent fuel pressure at a lower pump voltage again.

As it might need to drop to 7 volts or whatever before it drops below 40.

 

In my mind though the #1 thing relating to idle and fuel is dead times, because the actual deadtime is a huuuugggeee part of the total injector opening time. 

As in, deadtime could be 5x the actual time that fuel actually comes out while the injector is open.

 

If your deadtime is inaccurate then if you've got any temp compensation etc going on, your fuel at idle is gonna be a mess.

 

My idle has tidied itself up hugely since having accurate deadtimes.

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