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DIY Fuel injection thread.


yoeddynz

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1 hour ago, Yowzer said:

Because they can. 

Just put a tone wheel on your crankshaft already. The freeplay in the drive between crank and dizzy is going to be greater than any inaccuracy caused by low tooth count anyway.

I do get what you're saying, but I'm stupid so won't take the easy route.

 

The freeplay isn't really that much of an issue.

 

The timing chain is short, so there is minimal stretch there and there won't be much vibration going on causing changes in effective length between pulleys.

The distributor is always under load from the oil pump, so the backlash isn't an issue (ignition timing on deceleration isn't even important anyway).

The main source of inaccuracy would be if any of the gears in the system had teeth that weren't perfectly spaced, but that would also be pretty minimal.

The 7K-E distributor is also better built than a 4K distributor as it has a big sealed bearing on the shaft instead of just a bushing.

 

 

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1 hour ago, ajg193 said:

VR conditioner is built in to ecu.

 

Also the tooth needs to point at sensor quite an angle before from TDC (like 60 deg or so) with megasquirt, that point gives a hard limit on the maximum timing advance possible.

 

The problem with only one tooth is that the engine speed can change significantly over the space of 180 degrees of crank rotation, so it can really end up being a guessing game for correct timing. The original 7K-E distributor was just 4 teeth and timing controlled by the ecu, but Toyota seems to use a better vr conditioning system than MS, giving cleaner signals during cranking.

 

If 4 teeth was fine for giving accurate timing then why does Toyota use 24 teeth + a single tooth wheel in shitty old 4A-FE engines?

I was more saying it works, rather than use 4 tooth.

I'm still going with the  vr sensor itself (or megasquirt depending how you want to look at it)  is the issue.      If they are still like they used to be,  the ms has issues with at least the toyota / denso vr sensors.    All the ones that worked properly had a daughter board, or some kind of add on vr conditioner.   even ms3 didn't work properly with the onboard setup.

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Tooth count mostly affects transients rather than steady state.
IF your engine speed was exactly steady then you'd not need triggers at all once its going.

Why do OEM have lots of teeth on triggers?
Probably because transient conditions are by far by far the least controllable part of engine operation when it comes to emissions and economy.
Also some ECUs do fancy stuff like look for minor accel/decel through the crank angle to spot misfire issues or as part of a knock detection strategy.

Also I guess having fewer teeth makes it more of a problem at lower rpm than high, as you've got a much longer time period between engine speed "updates" 
Just doing some low effort maths, if you have a 4 tooth trigger on cam only, then at 1000rpm you're getting engine speed updates at 33hz. 
That seems less awful than I would have thought, unless my half arsed maths is wrong.
 

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7 hours ago, Roman said:

Tooth count mostly affects transients rather than steady state.

Also I guess having fewer teeth makes it more of a problem at lower rpm than high, as you've got a much longer time period between engine speed "updates" 
Just doing some low effort maths, if you have a 4 tooth trigger on cam only, then at 1000rpm you're getting engine speed updates at 33hz. 
That seems less awful than I would have thought, unless my half arsed maths is wrong.
 

4 teeth at 1000 rpm -> 500 signals per minute -> 500/60= 8.33 per second

 

These are the exact situations where fuel only is crap, it's much harder to get rid of the stumble when jumping on the throttle at low rpm because the ecu is always 180 degrees behind the engine. With the 20-1 setup all hesitations were completely gone. And during cranking you need the most resolution, as the engine speed is the most variable throughout the cycle. 4 teeth during cranking just results in a shit timing signal.

 

The way Toyota dealt with this issue (with 4 tooth distributor VAST ignition) was with a go between module between the distributor and the ecu. If the module didn't receive a signal from the ecu it would just fire whenever it got a pulse from the distributor (the teeth were set at base timing) - but obviously one pulse later.

 

 

 

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13 minutes ago, yoeddynz said:

In the amount of time you've spent fucking about talking about trigger wheels you'd have cut and filed one out by now. Honestly--it's not a rocket science job. Tools you'll need. 

Vice, 

Hacksaw, 

File. 

I'm just going to throw a piece of steel at the mill some time this week and let it do all the work. No hassle, no stress.

I am in no rush to get back to doing it right now and I have other stuff to do.

+ The two tools I don't have at home are a vice and hacksaw.

+ I don't really want a crank trigger. I want to hide it in the distributor.

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Crank trigger setup and then use dizzy as secondary input for cam position. Easy and less fucking around than this whole discussion has been. Crank triggers still look OEM unless you use flashy billet parts or some shit. 

You seem to be making it harder for yourself, for the sake of making it harder?

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22 minutes ago, kws said:

 

You seem to be making it harder for yourself, for the sake of making it harder?

Precisely. Just want to see what I can actually get to work. If I wanted to do it the easy way I would have either used a crank trigger or just put a 4A-GE in.

But also, crank triggers are absolutely disgusting on this type of engine.

 

 

Doing this sort of stuff is a good way for me to learn as much about machining as I can. There's not really much point in me doing it if I'm not really learning much.

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18 minutes ago, Roman said:


Thats 500 cam rotations, not 500 times that a tooth swipes past the VR. You get 4x as many signals as that? 
 

Probably. Was too early in the morning to do math.

 

4 cyl, 4 stroke gives 2 combustions per revolution -> 2000 combustions per minute -> 33 Hz

 

Yep. You are correct. I still believe my argument of engine speed fluctuating significantly at low rpm/cranking is valid though.

 

 

This is a 60-2 crank wheel during cranking:

Sample+tooth+log+60-2+wheel+while+cranki

You can see pretty clearly that if you only have 4 teeth on a camshaft, you will have no idea what the real position of the engine is for the vast majority of the cycle during cranking.

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I've found a 70 mm diameter bar of cast iron, internet seems to reckon that has a low magnetic coercivity so should be good as a VR trigger.

 

I have no idea what sort of steel the last wheel was made from, for all I know it would have turned into a permanent magnet within a week and stopped working.

 

I'll make up some G code and throw it through the mill tomorrow evening and see how it goes. Should end up being fairly minimal work if I get the code right,

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On 24/03/2019 at 19:21, ajg193 said:

Tooth (prior to removal of one) count needs to be a multiple of the number of cylinders, as with a megasquirt the ECU links a physical tooth with a "tach" signal (one tach tooth per cylinder) and then counts a set time after that to send the ignition pulse. This lets it resynchronise timing every 720/#cyl, rather than once per 720 degrees, supposedly improving accuracy.

Since 30 doesn't divide by 4, the system can't accept it. And removing any other teeth to try and make it work won't work either because then the tooth spacing won't be correct.

It's a bit of a shit limitation but that's just how they made it.

Right, understand now. So just put PLL code in another arduino and rescale the output frequency. Isn't that what software is for? Fixing hardware screw-ups (caused by other software requirements).

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Anyone got any experience with converting K-Jet to normal injectors? 

This is what the manifold looks like, you can see the six spaces for the injectors,
Ford-28-V6-Cologne-Inlet-manifold-Capri.

and with injectors installed
s-l500.jpg

There seems to be some kits for other brands, like Porsche, but i can't really find any detail on how the injectors fit into the manifold. Im also pondering how to get fuel to the injectors with all their angles being on the piss, as obviously a normal rail wont work, so old school hose tail injectors running to a "remote" rail?

The injectors are also fecking long, with the narrow end pointing down into the inlet manifold (and you can just see the tops protruding in the above photo)
FORD-CAPRI-SIERRA-XR4i-XR4x4-Set-of-Inje

Other suggestions are to replace the manifold with a later model one that has normal L-jet injection, but there wasn't one for the 2.8 Cologne V6 and as far as i can see the 2.9 (which had L-Jet) doesnt fit?

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34 minutes ago, Alfashark said:

Normally have the injector seats machined out to suit modern injectors.

@00quattro00   might be able to advise further.

The vag/porsche/mercedes had removable injector seats that you could replace with ones to fit an efi injector

 

You will require a funky ruel rail, might have to feed each injector off a hose

 

http://www.not2fast.com/VAG/InjectorCup.html

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My photo of the injectors seem to indicate that they may also use a removable seat, albeit not screw in. Cant find much info on that, but still looking. Maybe i can turn the ID on them down to fit standard injectors, and retain them with the factory style clamp, and use hoses off the injectors to a remote rail.

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