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DIY Fuel injection thread.


yoeddynz

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It's not the peak power or much of the full throttle stuff at all where you will see the gains.  Since  its not that hard to get the wot timing dailed in with the mechanical setup. Should be able to get decent gains in the part throttle with ecu controlling it.  Thats where you will gain the economy 

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Going from the factory Rover V8 injection system with distributor to ECU controlled wasted spark and fuelling, even with my basic "science dog" road tuning was a huge difference in butt dyno power. Economy didnt get any better, but that was more likely down to me not really knowing what i was doing.

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14 minutes ago, kws said:

Going from the factory Rover V8 injection system with distributor to ECU controlled wasted spark and fuelling, even with my basic "science dog" road tuning was a huge difference in butt dyno power. Economy didnt get any better, but that was more likely down to me not really knowing what i was doing.

I have a theory that butt dyno power goes up with tunes that aren't the best as you notice the power more when it comes on suddenly rather than smoothly and continuously. / @malarky's starlet has a shit tune on the carb and feels quite fast but isn't any faster than another friend's starlet with a better tune on his carbs (which feels quite slow when you're driving it in comparison)

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Agree with that 100%

Look up virtual dyno.

It's great for quantifying differences from road tuning if you can minimize variables.

I had a situation where I gained 20hp and heeeaaps of midrange power and the car felt slower.

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1 hour ago, ajg193 said:

I have a theory that butt dyno power goes up with tunes that aren't the best as you notice the power more when it comes on suddenly rather than smoothly and continuously. / @malarky's starlet has a shit tune on the carb and feels quite fast but isn't any faster than another friend's starlet with a better tune on his carbs (which feels quite slow when you're driving it in comparison)

i agree, and disagree on this statement. The difference with the Rover tune was that standard they run VERY conservative ignition timing and weak fuelling. Add a lot more timing and fuel, and it had more punch from idle to redline.

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Hey is anyone familiar with Link G1 ECU and hand controllers? Im thinking of converting to Speeduino, but would like to save the tune from the link and use it as a base map on the Speeduino. Its not PC tuneable though because made in 1990, so is there a way to review each fuel or ignition cell and write down the value? I know its a lot of cells to record down, but its only time.

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  • 1 month later...

Hi all, wondering if there’s anyone in the Nelson area who knows a bit about megasquirt stuff and that wants to come round to my place for a few beers whilst chewing over a couple of questions I’ve got re ignition. 

I’ve built the computer except for the ignition components and just need a little advice. Should be pretty simple for someone who’s been there before...

@yoeddynzmaybe when you get home...

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I'll try.... 

so, wasted spark, 6cyl, 3coils, each with two outputs.

obviously need 3 BIP373 driver things.

I was thinking of mounting the drivers remotely outside the megasquirt case and am using the relay board that came with the megasquirt and was going to mount the drivers on that, it just seemed cleaner. This way I can keep the high current switching out of the case and away from the brains...

question basically is the re the signal wires that need to go to the BIP373 for spark A, B, and C that come off the top of the little resistors R26,R29,R27, I was going to jumper them into SPR 1,2,3. Is the little pcb trace between spr123 and the DB37 plug up to the task or do I need to strengthen it? 

sorry if it makes no sense, I'm a bit out of my depth at the moment... plentry more questions no doubt...

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Without actually looking at the manuals or what is written down in my book of scribbles that pretty much sounded like what I did. Except I mounted drivers on a little heatsink a few inches from the MS case. Pics that might be useful... 

P1070435.jpg

20140806_173829.jpg

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That's what I'm aiming to do Alex except that I plan to send the signal wire through the DB37 plug. This requires that I solder into SPR1,2,&3 on the board and I want to find out if the little traces on the board between those inputs and the plug itself are up to the job...

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been chasing my tail recently with a hard to start/fouling on start/general rough running issue. 

last night i discovered a setting 'squirts per engine cycle' it was set to 1 and 'injector staging' was set to simultaneous

i changed it to 2 squirts and 'alternating, maybe a little improvement. but then i changed it to 4 squirts alternating and boom fired up really easy, ran quite smooth, i could even blip the throttle without it bogging out. shut the engine off cause it was late and i was in a closed garage and wanted to live. 

came home tonight and gave it a proper warm up, started up really easily and ran pretty good once again (previously id have to start and restart it 20 times before it would catch)

it immediately became apparent that the map was now about 4 times too rich.

image.png.c8bec5189f925fa4b1d310923bff2976.png

 

can anyone explain to me exactly what this function does. as far as i understand previously it was firing both cylinders full amount of fuel in one go and one cylinder was always scavenging its supply, and now its chopped up into 4 lots and flicks it around more evenly. 

or does it now dump 4x as much fuel in and its not just a coincidence the map is about 4x too rich. either way ill re tune the map and even at crazy rich it runs so much nicer. just sounds like a rotary. 

 

ECU - Megasquirt 1

Engine - 18rgeu + supercharger

 

 

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That is a pretty good explanation, I didn't find it via Google for some reason, cheers! 

Might give tuning on 2 squires a go and if not good bang it back to 4. Either way I'm confident it was the issue. 1 squirt for the whole crank rotation! No wonder it it was a pain to start 

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I'm not sure that's the issue. I was only idling and as far as I know the non linear is at the top of the flow? Though with 4 squirt it may have had such short openings that it affected it, I'd have expected to see lean though? 

Though in fucking around and running it quite rich I upset the spark plugs, cleaned them alot but they don't spark well anymore so will grab some new ones today and try to get a few laps around the block to bring the tune back in check. 

I have a company track day next week that I'm hoping to get the tune nailed down on. But just need to get it back close before then. 

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Nonlinear region is right at the bottom of the flow as you start to get issues with injector opening time being unpredictable when you request short pulses. Can either go too lean or too rich or just be purely random.

 

What duty cycle are your injectors at when at maximum load? What size are your injectors? Most modern 1300 cc things run 200-250 cc injectors and make maybe 60 kW-70 kW so would be around the 55 % duty cycle mark under full load.

 

You could go and characterise the injector flow properties using the built in function in the megasquirt, or just keep changing the deadtime / voltage correction / flow rate numbers until you get a stable result between 2 squirt and 4 squirt. Or you could just set it to 4 squirt and retune the map.

 

Do you have the autotune feature on TS? If you don't I can come for a drive with you and run my copy to get your map sorted.

 

Main reason the 1 squirt is no good is that it causes too much fluctuation in fuel rail pressure which results in unpredictable flow rates. Combined with the suboptimal injection timing at low speeds you get the result of it being hard to start and poor running below about 1200 rpm or so.

 

A factory 2T-GE would probably have run something like 2 squirts alternating (those old ECUs generally only have 2 injector drivers) with low impedance injectors going through a resistor.

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